diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index 5d2965ca..2c198f14 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -1,4047 +1,4045 @@
 <?php
 
 /**
  * Calendar plugin for Roundcube webmail
  *
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2014-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class calendar extends rcube_plugin
 {
     const FREEBUSY_UNKNOWN   = 0;
     const FREEBUSY_FREE      = 1;
     const FREEBUSY_BUSY      = 2;
     const FREEBUSY_TENTATIVE = 3;
     const FREEBUSY_OOF       = 4;
 
     const SESSION_KEY = 'calendar_temp';
 
     public $task = '?(?!logout).*';
     public $rc;
     public $lib;
     public $resources_dir;
     public $home;  // declare public to be used in other classes
     public $urlbase;
     public $timezone;
     public $timezone_offset;
     public $gmt_offset;
     public $ui;
 
     public $defaults = [
         'calendar_default_view' => "agendaWeek",
         'calendar_timeslots'    => 2,
         'calendar_work_start'   => 6,
         'calendar_work_end'     => 18,
         'calendar_agenda_range' => 60,
         'calendar_show_weekno'  => 0,
         'calendar_first_day'    => 1,
         'calendar_first_hour'   => 6,
         'calendar_time_format'  => null,
         'calendar_event_coloring'      => 0,
         'calendar_time_indicator'      => true,
         'calendar_allow_invite_shared' => false,
         'calendar_itip_send_option'    => 3,
         'calendar_itip_after_action'   => 0,
     ];
 
     // These are implemented with __get()
     //  private $ical;
     //  private $itip;
     //  private $driver;
 
 
     /**
      * Plugin initialization.
      */
     function init()
     {
         $this->rc = rcube::get_instance();
 
         $this->register_task('calendar', 'calendar');
 
         // load calendar configuration
         $this->load_config();
 
         // catch iTIP confirmation requests that don're require a valid session
         if ($this->rc->action == 'attend' && !empty($_REQUEST['_t'])) {
             $this->add_hook('startup', [$this, 'itip_attend_response']);
         }
         else if ($this->rc->action == 'feed' && !empty($_REQUEST['_cal'])) {
             $this->add_hook('startup', [$this, 'ical_feed_export']);
         }
         else if ($this->rc->task != 'login') {
             // default startup routine
             $this->add_hook('startup', [$this, 'startup']);
         }
 
         $this->add_hook('user_delete', [$this, 'user_delete']);
     }
 
     /**
      * Setup basic plugin environment and UI
      */
     protected function setup()
     {
         $this->require_plugin('libcalendaring');
         $this->require_plugin('libkolab');
 
         $this->lib             = libcalendaring::get_instance();
         $this->timezone        = $this->lib->timezone;
         $this->gmt_offset      = $this->lib->gmt_offset;
         $this->dst_active      = $this->lib->dst_active;
         $this->timezone_offset = $this->gmt_offset / 3600 - $this->dst_active;
 
         // load localizations
         $this->add_texts('localization/', $this->rc->task == 'calendar' && (!$this->rc->action || $this->rc->action == 'print'));
 
         require($this->home . '/lib/calendar_ui.php');
         $this->ui = new calendar_ui($this);
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         // the calendar module can be enabled/disabled by the kolab_auth plugin
         if ($this->rc->config->get('calendar_disabled', false)
             || !$this->rc->config->get('calendar_enabled', true)
         ) {
             return;
         }
 
         $this->setup();
 
         // load Calendar user interface
         if (!$this->rc->output->ajax_call
             && (empty($this->rc->output->env['framed']) || $args['action'] == 'preview')
         ) {
             $this->ui->init();
 
             // settings are required in (almost) every GUI step
             if ($args['action'] != 'attend') {
                 $this->rc->output->set_env('calendar_settings', $this->load_settings());
             }
         }
 
         if ($args['task'] == 'calendar' && $args['action'] != 'save-pref') {
             if ($args['action'] != 'upload') {
                 $this->load_driver();
             }
 
             // register calendar actions
             $this->register_action('index', [$this, 'calendar_view']);
             $this->register_action('event', [$this, 'event_action']);
             $this->register_action('calendar', [$this, 'calendar_action']);
             $this->register_action('count', [$this, 'count_events']);
             $this->register_action('load_events', [$this, 'load_events']);
             $this->register_action('export_events', [$this, 'export_events']);
             $this->register_action('import_events', [$this, 'import_events']);
             $this->register_action('upload', [$this, 'attachment_upload']);
             $this->register_action('get-attachment', [$this, 'attachment_get']);
             $this->register_action('freebusy-status', [$this, 'freebusy_status']);
             $this->register_action('freebusy-times', [$this, 'freebusy_times']);
             $this->register_action('randomdata', [$this, 'generate_randomdata']);
             $this->register_action('print', [$this,'print_view']);
             $this->register_action('mailimportitip', [$this, 'mail_import_itip']);
             $this->register_action('mailimportattach', [$this, 'mail_import_attachment']);
             $this->register_action('dialog-ui', [$this, 'mail_message2event']);
             $this->register_action('check-recent', [$this, 'check_recent']);
             $this->register_action('itip-status', [$this, 'event_itip_status']);
             $this->register_action('itip-remove', [$this, 'event_itip_remove']);
             $this->register_action('itip-decline-reply', [$this, 'mail_itip_decline_reply']);
             $this->register_action('itip-delegate', [$this, 'mail_itip_delegate']);
             $this->register_action('resources-list', [$this, 'resources_list']);
             $this->register_action('resources-owner', [$this, 'resources_owner']);
             $this->register_action('resources-calendar', [$this, 'resources_calendar']);
             $this->register_action('resources-autocomplete', [$this, 'resources_autocomplete']);
             $this->register_action('talk-room-create', [$this, 'talk_room_create']);
 
             $this->add_hook('refresh', [$this, 'refresh']);
 
             // remove undo information...
             if (!empty($_SESSION['calendar_event_undo'])) {
                 $undo = $_SESSION['calendar_event_undo'];
                 // ...after timeout
                 $undo_time = $this->rc->config->get('undo_timeout', 0);
                 if ($undo['ts'] < time() - $undo_time) {
                     $this->rc->session->remove('calendar_event_undo');
                     // @TODO: do EXPUNGE on kolab objects?
                 }
             }
         }
         else if ($args['task'] == 'settings') {
             // add hooks for Calendar settings
             $this->add_hook('preferences_sections_list', [$this, 'preferences_sections_list']);
             $this->add_hook('preferences_list', [$this, 'preferences_list']);
             $this->add_hook('preferences_save', [$this, 'preferences_save']);
         }
         else if ($args['task'] == 'mail') {
             // hooks to catch event invitations on incoming mails
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 $this->add_hook('template_object_messagebody', [$this, 'mail_messagebody_html']);
             }
 
             // add 'Create event' item to message menu
             if ($this->api->output->type == 'html' && (empty($_GET['_rel']) || $_GET['_rel'] != 'event')) {
                 $this->api->output->add_label('calendar.createfrommail');
                 $this->api->add_content(
                     html::tag('li', ['role' => 'menuitem'],
                         $this->api->output->button([
                             'command'  => 'calendar-create-from-mail',
                             'label'    => 'calendar.createfrommail',
                             'type'     => 'link',
                             'classact' => 'icon calendarlink active',
                             'class'    => 'icon calendarlink disabled',
                             'innerclass' => 'icon calendar',
                         ])
                     ),
                     'messagemenu'
                 );
             }
 
             $this->add_hook('messages_list', [$this, 'mail_messages_list']);
             $this->add_hook('message_compose', [$this, 'mail_message_compose']);
         }
         else if ($args['task'] == 'addressbook') {
             if ($this->rc->config->get('calendar_contact_birthdays')) {
                 $this->add_hook('contact_update', [$this, 'contact_update']);
                 $this->add_hook('contact_create', [$this, 'contact_update']);
             }
         }
 
         // add hooks to display alarms
         $this->add_hook('pending_alarms', [$this, 'pending_alarms']);
         $this->add_hook('dismiss_alarms', [$this, 'dismiss_alarms']);
     }
 
     /**
      * Helper method to load the backend driver according to local config
      */
     private function load_driver()
     {
         if (!empty($this->driver)) {
             return;
         }
 
         $driver_name = $this->rc->config->get('calendar_driver', 'database');
         $driver_class = $driver_name . '_driver';
 
         require_once($this->home . '/drivers/calendar_driver.php');
         require_once($this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php');
 
         $this->driver = new $driver_class($this);
 
         if ($this->driver->undelete) {
             $this->driver->undelete = $this->rc->config->get('undo_timeout', 0) > 0;
         }
     }
 
     /**
      * Load iTIP functions
      */
     private function load_itip()
     {
         if (empty($this->itip)) {
             require_once($this->home . '/lib/calendar_itip.php');
             $this->itip = new calendar_itip($this);
 
             if ($this->rc->config->get('kolab_invitation_calendars')) {
                 $this->itip->set_rsvp_actions(['accepted','tentative','declined','delegated','needs-action']);
             }
         }
 
         return $this->itip;
     }
 
     /**
      * Load iCalendar functions
      */
     public function get_ical()
     {
         if (empty($this->ical)) {
             $this->ical = libcalendaring::get_ical();
         }
 
         return $this->ical;
     }
 
     /**
      * Get properties of the calendar this user has specified as default
      */
     public function get_default_calendar($calendars = null)
     {
         if ($calendars === null) {
             $filter    = calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_WRITEABLE;
             $calendars = $this->driver->list_calendars($filter);
         }
 
         $default_id = $this->rc->config->get('calendar_default_calendar');
         $calendar   = !empty($calendars[$default_id]) ? $calendars[$default_id] : null;
         $first      = null;
 
         if (!$calendar) {
             foreach ($calendars as $cal) {
                 if (!empty($cal['default']) && $cal['editable']) {
                     $calendar = $cal;
                 }
                 if ($cal['editable']) {
                     $first = $cal;
                 }
             }
         }
 
         return $calendar ?: $first;
     }
 
     /**
      * Render the main calendar view from skin template
      */
     function calendar_view()
     {
         $this->rc->output->set_pagetitle($this->gettext('calendar'));
 
         // Add JS files to the page header
         $this->ui->addJS();
 
         $this->ui->init_templates();
         $this->rc->output->add_label('lowest','low','normal','high','highest','delete',
             'cancel','uploading','noemailwarning','close'
         );
 
         // initialize attendees autocompletion
         $this->rc->autocomplete_init();
 
         $this->rc->output->set_env('timezone', $this->timezone->getName());
         $this->rc->output->set_env('calendar_driver', $this->rc->config->get('calendar_driver'), false);
         $this->rc->output->set_env('calendar_resources', (bool)$this->rc->config->get('calendar_resources_driver'));
         $this->rc->output->set_env('identities-selector', $this->ui->identity_select([
                 'id'         => 'edit-identities-list',
                 'aria-label' => $this->gettext('roleorganizer'),
                 'class'      => 'form-control custom-select',
         ]));
 
         $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
         if (in_array($view, ['agendaWeek', 'agendaDay', 'month', 'list'])) {
             $this->rc->output->set_env('view', $view);
         }
 
         if ($date = rcube_utils::get_input_value('date', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('date', $date);
         }
 
         if ($msgref = rcube_utils::get_input_value('itip', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('itip_events', $this->itip_events($msgref));
         }
 
         $this->rc->output->send('calendar.calendar');
     }
 
     /**
      * Handler for preferences_sections_list hook.
      * Adds Calendar settings sections into preferences sections list.
      *
      * @param array Original parameters
      *
      * @return array Modified parameters
      */
     function preferences_sections_list($p)
     {
         $p['list']['calendar'] = [
             'id'      => 'calendar',
             'section' => $this->gettext('calendar'),
         ];
 
         return $p;
     }
 
     /**
      * Handler for preferences_list hook.
      * Adds options blocks into Calendar settings sections in Preferences.
      *
      * @param array Original parameters
      *
      * @return array Modified parameters
      */
     function preferences_list($p)
     {
         if ($p['section'] != 'calendar') {
             return $p;
         }
 
         $no_override = array_flip((array) $this->rc->config->get('dont_override'));
 
         $p['blocks']['view']['name'] = $this->gettext('mainoptions');
 
         if (!isset($no_override['calendar_default_view'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_default_view';
             $view = $this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view']);
 
             $select = new html_select(['name' => '_default_view', 'id' => $field_id]);
             $select->add($this->gettext('day'), "agendaDay");
             $select->add($this->gettext('week'), "agendaWeek");
             $select->add($this->gettext('month'), "month");
             $select->add($this->gettext('agenda'), "list");
 
             $p['blocks']['view']['options']['default_view'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('default_view'))),
                 'content' => $select->show($view == 'table' ? 'list' : $view),
             ];
         }
 
         if (!isset($no_override['calendar_timeslots'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id  = 'rcmfd_timeslots';
             $choices   = ['1', '2', '3', '4', '6'];
             $timeslots = $this->rc->config->get('calendar_timeslots', $this->defaults['calendar_timeslots']);
 
             $select = new html_select(['name' => '_timeslots', 'id' => $field_id]);
             $select->add($choices, $choices);
 
             $p['blocks']['view']['options']['timeslots'] = [
                 'title' => html::label($field_id, rcube::Q($this->gettext('timeslots'))),
                 'content' => $select->show(strval($timeslots)),
             ];
         }
 
         if (!isset($no_override['calendar_first_day'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id  = 'rcmfd_firstday';
             $first_day = $this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
 
             $select = new html_select(['name' => '_first_day', 'id' => $field_id]);
             $select->add($this->gettext('sunday'), '0');
             $select->add($this->gettext('monday'), '1');
             $select->add($this->gettext('tuesday'), '2');
             $select->add($this->gettext('wednesday'), '3');
             $select->add($this->gettext('thursday'), '4');
             $select->add($this->gettext('friday'), '5');
             $select->add($this->gettext('saturday'), '6');
 
             $p['blocks']['view']['options']['first_day'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('first_day'))),
                 'content' => $select->show(strval($first_day)),
             ];
         }
 
         if (!isset($no_override['calendar_first_hour'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $first_hour  = $this->rc->config->get('calendar_first_hour', $this->defaults['calendar_first_hour']);
             $time_format = $this->rc->config->get('calendar_time_format', $this->defaults['calendar_time_format']);
             $time_format = $this->rc->config->get('time_format', libcalendaring::to_php_date_format($time_format));
             $field_id    = 'rcmfd_firsthour';
 
             $select_hours = new html_select(['name' => '_first_hour', 'id' => $field_id]);
             for ($h = 0; $h < 24; $h++) {
                 $select_hours->add(date($time_format, mktime($h, 0, 0)), $h);
             }
 
             $p['blocks']['view']['options']['first_hour'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('first_hour'))),
                 'content' => $select_hours->show($first_hour),
             ];
         }
 
         if (!isset($no_override['calendar_work_start'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id   = 'rcmfd_workstart';
             $work_start = $this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']);
             $work_end   = $this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']);
 
             $p['blocks']['view']['options']['workinghours'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('workinghours'))),
                 'content' => html::div('input-group',
                     $select_hours->show($work_start, ['name' => '_work_start', 'id' => $field_id])
                     . html::span('input-group-append input-group-prepend', html::span('input-group-text',' &mdash; '))
                     . $select_hours->show($work_end, ['name' => '_work_end', 'id' => $field_id])
                 )
             ];
         }
 
         if (!isset($no_override['calendar_event_coloring'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_coloring';
             $mode     = $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
 
             $select_colors = new html_select(['name' => '_event_coloring', 'id' => $field_id]);
             $select_colors->add($this->gettext('coloringmode0'), 0);
             $select_colors->add($this->gettext('coloringmode1'), 1);
             $select_colors->add($this->gettext('coloringmode2'), 2);
             $select_colors->add($this->gettext('coloringmode3'), 3);
 
             $p['blocks']['view']['options']['eventcolors'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('eventcoloring'))),
                 'content' => $select_colors->show($mode),
             ];
         }
 
         // loading driver is expensive, don't do it if not needed
         $this->load_driver();
 
         if (!isset($no_override['calendar_default_alarm_type']) || !isset($no_override['calendar_default_alarm_offset'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $alarm_type = $alarm_offset = '';
 
             if (!isset($no_override['calendar_default_alarm_type'])) {
                 $field_id    = 'rcmfd_alarm';
                 $select_type = new html_select(['name' => '_alarm_type', 'id' => $field_id]);
                 $select_type->add($this->gettext('none'), '');
 
                 foreach ($this->driver->alarm_types as $type) {
                     $select_type->add($this->rc->gettext(strtolower("alarm{$type}option"), 'libcalendaring'), $type);
                 }
 
                 $alarm_type = $select_type->show($this->rc->config->get('calendar_default_alarm_type', ''));
             }
 
             if (!isset($no_override['calendar_default_alarm_offset'])) {
                 $field_id      = 'rcmfd_alarm';
                 $input_value   = new html_inputfield(['name' => '_alarm_value', 'id' => $field_id . 'value', 'size' => 3]);
                 $select_offset = new html_select(['name' => '_alarm_offset', 'id' => $field_id . 'offset']);
 
                 foreach (['-M','-H','-D','+M','+H','+D'] as $trigger) {
                     $select_offset->add($this->rc->gettext('trigger' . $trigger, 'libcalendaring'), $trigger);
                 }
 
                 $preset = libcalendaring::parse_alarm_value($this->rc->config->get('calendar_default_alarm_offset', '-15M'));
                 $alarm_offset = $input_value->show($preset[0]) . ' ' . $select_offset->show($preset[1]);
             }
 
             $p['blocks']['view']['options']['alarmtype'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('defaultalarmtype'))),
                 'content' => html::div('input-group', $alarm_type . ' ' . $alarm_offset),
             ];
         }
 
         if (!isset($no_override['calendar_default_calendar'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             // default calendar selection
             $field_id   = 'rcmfd_default_calendar';
             $filter     = calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_ACTIVE | calendar_driver::FILTER_INSERTABLE;
             $select_cal = new html_select(['name' => '_default_calendar', 'id' => $field_id, 'is_escaped' => true]);
 
             $default_calendar = null;
             foreach ((array) $this->driver->list_calendars($filter) as $id => $prop) {
                 $select_cal->add($prop['name'], strval($id));
                 if (!empty($prop['default'])) {
                     $default_calendar = $id;
                 }
             }
 
             $p['blocks']['view']['options']['defaultcalendar'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('defaultcalendar'))),
                 'content' => $select_cal->show($this->rc->config->get('calendar_default_calendar', $default_calendar)),
             ];
         }
 
         if (!isset($no_override['calendar_show_weekno'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id   = 'rcmfd_show_weekno';
             $select = new html_select(['name' => '_show_weekno', 'id' => $field_id]);
             $select->add($this->gettext('weeknonone'), -1);
             $select->add($this->gettext('weeknodatepicker'), 0);
             $select->add($this->gettext('weeknoall'), 1);
 
             $p['blocks']['view']['options']['show_weekno'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('showweekno'))),
                 'content' => $select->show(intval($this->rc->config->get('calendar_show_weekno'))),
             ];
         }
 
         $p['blocks']['itip']['name'] = $this->gettext('itipoptions');
 
         // Invitations handling
         if (!isset($no_override['calendar_itip_after_action'])) {
             if (empty($p['current'])) {
                 $p['blocks']['itip']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_after_action';
             $select   = new html_select([
                     'name'     => '_after_action',
                     'id'       => $field_id,
                     'onchange' => "\$('#{$field_id}_select')[this.value == 4 ? 'show' : 'hide']()"
             ]);
 
             $select->add($this->gettext('afternothing'), '');
             $select->add($this->gettext('aftertrash'), 1);
             $select->add($this->gettext('afterdelete'), 2);
             $select->add($this->gettext('afterflagdeleted'), 3);
             $select->add($this->gettext('aftermoveto'), 4);
 
             $val    = $this->rc->config->get('calendar_itip_after_action', $this->defaults['calendar_itip_after_action']);
             $folder = null;
 
             if ($val !== null && $val !== '' && !is_int($val)) {
                 $folder = $val;
                 $val    = 4;
             }
 
             $folders = $this->rc->folder_selector([
                     'id'            => $field_id . '_select',
                     'name'          => '_after_action_folder',
                     'maxlength'     => 30,
                     'folder_filter' => 'mail',
                     'folder_rights' => 'w',
                     'style'         => $val !== 4 ? 'display:none' : '',
             ]);
 
             $p['blocks']['itip']['options']['after_action'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('afteraction'))),
                 'content' => html::div(
                     'input-group input-group-combo',
                     $select->show($val) . $folders->show($folder)
                 ),
             ];
         }
 
         // category definitions
         if (empty($this->driver->nocategories) && !isset($no_override['calendar_categories'])) {
             $p['blocks']['categories']['name'] = $this->gettext('categories');
 
             if (empty($p['current'])) {
                 $p['blocks']['categories']['content'] = true;
                 return $p;
             }
 
             $categories      = (array) $this->driver->list_categories();
             $categories_list = '';
 
             foreach ($categories as $name => $color) {
                 $key = md5($name);
                 $field_class = 'rcmfd_category_' . str_replace(' ', '_', $name);
                 $category_remove = html::span('input-group-append',
                     html::a([
                             'class'   => 'button icon delete input-group-text',
                             'onclick' => '$(this).parent().parent().remove()',
                             'title'   => $this->gettext('remove_category'),
                             'href'    => '#rcmfd_new_category',
                         ],
                         html::span('inner', $this->gettext('delete'))
                     )
                 );
 
                 $category_name  = new html_inputfield(array('name' => "_categories[$key]", 'class' => $field_class, 'size' => 30, 'disabled' => $this->driver->categoriesimmutable));
                 $category_color = new html_inputfield(array('name' => "_colors[$key]", 'class' => "$field_class colors", 'size' => 6));
                 $hidden         = '';
 
                 if (!empty($this->driver->categoriesimmutable)) {
                     $hidden =  html::tag('input', ['type' => 'hidden', 'name' => "_categories[$key]", 'value' => $name]);
                 }
 
                 $categories_list .= $hidden
                     . html::div('input-group', $category_name->show($name) . $category_color->show($color) . $category_remove);
             }
 
             $p['blocks']['categories']['options']['category_' . $name] = [
                 'content' => html::div(['id' => 'calendarcategories'], $categories_list),
             ];
 
             $field_id = 'rcmfd_new_category';
             $new_category = new html_inputfield(['name' => '_new_category', 'id' => $field_id, 'size' => 30]);
             $add_category = html::span('input-group-append',
                 html::a(
                     [
                         'type'    => 'button',
                         'class'   => 'button create input-group-text',
                         'title'   => $this->gettext('add_category'),
                         'onclick' => 'rcube_calendar_add_category()',
                         'href'    => '#rcmfd_new_category',
                     ],
                     html::span('inner', $this->gettext('add_category'))
                 )
             );
 
             $p['blocks']['categories']['options']['categories'] = [
                 'content' => html::div('input-group', $new_category->show('') . $add_category),
             ];
 
             $this->rc->output->add_label('delete', 'calendar.remove_category');
             $this->rc->output->add_script('
 function rcube_calendar_add_category() {
     var name = $("#rcmfd_new_category").val();
     if (name.length) {
         var button_label = rcmail.gettext("calendar.remove_category");
         var input = $("<input>").attr({type: "text", name: "_categories[]", size: 30, "class": "form-control"}).val(name);
         var color = $("<input>").attr({type: "text", name: "_colors[]", size: 6, "class": "colors form-control"}).val("000000");
         var button = $("<a>").attr({"class": "button icon delete input-group-text", title: button_label, href: "#rcmfd_new_category"})
             .click(function() { $(this).parent().parent().remove(); })
             .append($("<span>").addClass("inner").text(rcmail.gettext("delete")));
 
         $("<div>").addClass("input-group").append(input).append(color).append($("<span class=\'input-group-append\'>").append(button))
             .appendTo("#calendarcategories");
         color.minicolors(rcmail.env.minicolors_config || {});
         $("#rcmfd_new_category").val("");
     }
 }',
                 'foot'
             );
 
             $this->rc->output->add_script('
 $("#rcmfd_new_category").keypress(function(event) {
     if (event.which == 13) {
         rcube_calendar_add_category();
         event.preventDefault();
     }
 });',
                 'docready'
             );
 
             // load miniColors js/css files
             jqueryui::miniColors();
         }
 
         // virtual birthdays calendar
         if (!isset($no_override['calendar_contact_birthdays'])) {
             $p['blocks']['birthdays']['name'] = $this->gettext('birthdayscalendar');
 
             if (empty($p['current'])) {
                 $p['blocks']['birthdays']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_contact_birthdays';
             $input    = new html_checkbox([
                     'name'    => '_contact_birthdays',
                     'id'      => $field_id,
                     'value'   => 1,
                     'onclick' => '$(".calendar_birthday_props").prop("disabled",!this.checked)'
             ]);
 
             $p['blocks']['birthdays']['options']['contact_birthdays'] = [
                 'title'   => html::label($field_id, $this->gettext('displaybirthdayscalendar')),
                 'content' => $input->show($this->rc->config->get('calendar_contact_birthdays') ? 1 : 0),
             ];
 
             $input_attrib = [
                 'class'    => 'calendar_birthday_props',
                 'disabled' => !$this->rc->config->get('calendar_contact_birthdays'),
             ];
 
             $sources  = [];
             $checkbox = new html_checkbox(['name' => '_birthday_adressbooks[]'] + $input_attrib);
 
             foreach ($this->rc->get_address_sources(false, true) as $source) {
                 // Roundcube >= 1.5, Ignore Collected Recipients and Trusted Senders sources
                 if ((defined('rcube_addressbook::TYPE_RECIPIENT') && $source['id'] == (string) rcube_addressbook::TYPE_RECIPIENT)
                     || (defined('rcube_addressbook::TYPE_TRUSTED_SENDER') && $source['id'] == (string) rcube_addressbook::TYPE_TRUSTED_SENDER)
                 ) {
                     continue;
                 }
 
                 $active = in_array($source['id'], (array) $this->rc->config->get('calendar_birthday_adressbooks')) ? $source['id'] : '';
                 $sources[] = html::tag('li', null,
                     html::label(null,
                         $checkbox->show($active, ['value' => $source['id']])
                         . rcube::Q(!empty($source['realname']) ? $source['realname'] : $source['name'])
                     )
                 );
             }
 
             $p['blocks']['birthdays']['options']['birthday_adressbooks'] = [
                 'title'   => rcube::Q($this->gettext('birthdayscalendarsources')),
                 'content' => html::tag('ul', 'proplist', implode("\n", $sources)),
             ];
 
             $field_id = 'rcmfd_birthdays_alarm';
             $select_type = new html_select(['name' => '_birthdays_alarm_type', 'id' => $field_id] + $input_attrib);
             $select_type->add($this->gettext('none'), '');
 
             foreach ($this->driver->alarm_types as $type) {
                 $select_type->add($this->rc->gettext(strtolower("alarm{$type}option"), 'libcalendaring'), $type);
             }
 
             $input_value   = new html_inputfield(['name' => '_birthdays_alarm_value', 'id' => $field_id . 'value', 'size' => 3] + $input_attrib);
             $select_offset = new html_select(['name' => '_birthdays_alarm_offset', 'id' => $field_id . 'offset'] + $input_attrib);
 
             foreach (['-M','-H','-D'] as $trigger) {
                 $select_offset->add($this->rc->gettext('trigger' . $trigger, 'libcalendaring'), $trigger);
             }
 
             $preset      = libcalendaring::parse_alarm_value($this->rc->config->get('calendar_birthdays_alarm_offset', '-1D'));
             $preset_type = $this->rc->config->get('calendar_birthdays_alarm_type', '');
 
             $p['blocks']['birthdays']['options']['birthdays_alarmoffset'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('showalarms'))),
                 'content' => html::div('input-group',
                     $select_type->show($preset_type)
                     . $input_value->show($preset[0]) . ' ' . $select_offset->show($preset[1])
                 ),
             ];
         }
 
         return $p;
     }
 
     /**
      * Handler for preferences_save hook.
      * Executed on Calendar settings form submit.
      *
      * @param array Original parameters
      *
      * @return array Modified parameters
      */
     function preferences_save($p)
     {
         if ($p['section'] == 'calendar') {
             $this->load_driver();
 
             // compose default alarm preset value
             $alarm_offset  = rcube_utils::get_input_value('_alarm_offset', rcube_utils::INPUT_POST);
             $alarm_value   = rcube_utils::get_input_value('_alarm_value', rcube_utils::INPUT_POST);
             $default_alarm = $alarm_offset[0] . intval($alarm_value) . $alarm_offset[1];
 
             $birthdays_alarm_offset = rcube_utils::get_input_value('_birthdays_alarm_offset', rcube_utils::INPUT_POST);
             $birthdays_alarm_value  = rcube_utils::get_input_value('_birthdays_alarm_value', rcube_utils::INPUT_POST);
             $birthdays_alarm_value  = $birthdays_alarm_offset[0] . intval($birthdays_alarm_value) . $birthdays_alarm_offset[1];
 
             $p['prefs'] = [
                 'calendar_default_view' => rcube_utils::get_input_value('_default_view', rcube_utils::INPUT_POST),
                 'calendar_timeslots'    => intval(rcube_utils::get_input_value('_timeslots', rcube_utils::INPUT_POST)),
                 'calendar_first_day'    => intval(rcube_utils::get_input_value('_first_day', rcube_utils::INPUT_POST)),
                 'calendar_first_hour'   => intval(rcube_utils::get_input_value('_first_hour', rcube_utils::INPUT_POST)),
                 'calendar_work_start'   => intval(rcube_utils::get_input_value('_work_start', rcube_utils::INPUT_POST)),
                 'calendar_work_end'     => intval(rcube_utils::get_input_value('_work_end', rcube_utils::INPUT_POST)),
                 'calendar_show_weekno'  => intval(rcube_utils::get_input_value('_show_weekno', rcube_utils::INPUT_POST)),
                 'calendar_event_coloring'       => intval(rcube_utils::get_input_value('_event_coloring', rcube_utils::INPUT_POST)),
                 'calendar_default_alarm_type'   => rcube_utils::get_input_value('_alarm_type', rcube_utils::INPUT_POST),
                 'calendar_default_alarm_offset' => $default_alarm,
                 'calendar_default_calendar'     => rcube_utils::get_input_value('_default_calendar', rcube_utils::INPUT_POST),
                 'calendar_date_format'          => null,  // clear previously saved values
                 'calendar_time_format'          => null,
                 'calendar_contact_birthdays'      => (bool) rcube_utils::get_input_value('_contact_birthdays', rcube_utils::INPUT_POST),
                 'calendar_birthday_adressbooks'   => (array) rcube_utils::get_input_value('_birthday_adressbooks', rcube_utils::INPUT_POST),
                 'calendar_birthdays_alarm_type'   => rcube_utils::get_input_value('_birthdays_alarm_type', rcube_utils::INPUT_POST),
                 'calendar_birthdays_alarm_offset' => $birthdays_alarm_value ?: null,
                 'calendar_itip_after_action'      => intval(rcube_utils::get_input_value('_after_action', rcube_utils::INPUT_POST)),
             ];
 
             if ($p['prefs']['calendar_itip_after_action'] == 4) {
                 $p['prefs']['calendar_itip_after_action'] = rcube_utils::get_input_value('_after_action_folder', rcube_utils::INPUT_POST, true);
             }
 
             // categories
             if (empty($this->driver->nocategories)) {
                 $old_categories = $new_categories = [];
 
                 foreach ($this->driver->list_categories() as $name => $color) {
                     $old_categories[md5($name)] = $name;
                 }
 
                 $categories = (array) rcube_utils::get_input_value('_categories', rcube_utils::INPUT_POST);
                 $colors     = (array) rcube_utils::get_input_value('_colors', rcube_utils::INPUT_POST);
 
                 foreach ($categories as $key => $name) {
                     if (!isset($colors[$key])) {
                         continue;
                     }
 
                     $color = preg_replace('/^#/', '', strval($colors[$key]));
 
                     // rename categories in existing events -> driver's job
                     if (!empty($old_categories[$key])) {
                         $oldname = $old_categories[$key];
                         $this->driver->replace_category($oldname, $name, $color);
                         unset($old_categories[$key]);
                     }
                     else {
                         $this->driver->add_category($name, $color);
                     }
 
                     $new_categories[$name] = $color;
                 }
 
                 // these old categories have been removed, alter events accordingly -> driver's job
                 foreach ((array) $old_categories as $key => $name) {
                     $this->driver->remove_category($name);
                 }
 
                 $p['prefs']['calendar_categories'] = $new_categories;
             }
         }
 
         return $p;
     }
 
     /**
      * Dispatcher for calendar actions initiated by the client
      */
     function calendar_action()
     {
         $action  = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $cal     = rcube_utils::get_input_value('c', rcube_utils::INPUT_GPC);
         $success = false;
         $reload  = false;
 
         if (isset($cal['showalarms'])) {
             $cal['showalarms'] = intval($cal['showalarms']);
         }
 
         switch ($action) {
         case "form-new":
         case "form-edit":
             echo $this->ui->calendar_editform($action, $cal);
             exit;
 
         case "new":
             $success = $this->driver->create_calendar($cal);
             $reload  = true;
             break;
 
         case "edit":
             $success = $this->driver->edit_calendar($cal);
             $reload  = true;
             break;
 
         case "delete":
             if ($success = $this->driver->delete_calendar($cal)) {
                 $this->rc->output->command('plugin.destroy_source', ['id' => $cal['id']]);
             }
             break;
 
         case "subscribe":
             if (!$this->driver->subscribe_calendar($cal)) {
                 $this->rc->output->show_message($this->gettext('errorsaving'), 'error');
             }
             else {
                 $calendars = $this->driver->list_calendars();
                 $calendar  = !empty($calendars[$cal['id']]) ? $calendars[$cal['id']] : null;
 
                 // find parent folder and check if it's a "user calendar"
                 // if it's also activated we need to refresh it (#5340)
                 while (!empty($calendar['parent'])) {
                     if (isset($calendars[$calendar['parent']])) {
                         $calendar = $calendars[$calendar['parent']];
                     }
                     else {
                         break;
                     }
                 }
 
                 if ($calendar && $calendar['id'] != $cal['id']
                     && !empty($calendar['active'])
                     && $calendar['group'] == "other user"
                 ) {
                     $this->rc->output->command('plugin.refresh_source', $calendar['id']);
                 }
             }
             return;
 
         case "search":
             $results    = [];
             $color_mode = $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
             $query      = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
             $source     = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
 
             foreach ((array) $this->driver->search_calendars($query, $source) as $id => $prop) {
                 $editname = $prop['editname'];
                 unset($prop['editname']);  // force full name to be displayed
                 $prop['active'] = false;
 
                 // let the UI generate HTML and CSS representation for this calendar
                 $html = $this->ui->calendar_list_item($id, $prop, $jsenv);
                 $cal  = $jsenv[$id];
                 $cal['editname'] = $editname;
                 $cal['html']     = $html;
 
                 if (!empty($prop['color'])) {
                     $cal['css'] = $this->ui->calendar_css_classes($id, $prop, $color_mode);
                 }
 
                 $results[] = $cal;
             }
 
             // report more results available
             if (!empty($this->driver->search_more_results)) {
                 $this->rc->output->show_message('autocompletemore', 'notice');
             }
 
             $reqid = rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC);
             $this->rc->output->command('multi_thread_http_response', $results, $reqid);
             return;
         }
 
         if ($success) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $error_msg = $this->gettext('errorsaving');
             if (!empty($this->driver->last_error)) {
                 $error_msg .= ': ' . $this->driver->last_error;
             }
             $this->rc->output->show_message($error_msg, 'error');
         }
 
         $this->rc->output->command('plugin.unlock_saving');
 
         if ($success && $reload) {
             $this->rc->output->command('plugin.reload_view');
         }
     }
 
     /**
      * Dispatcher for event actions initiated by the client
      */
     function event_action()
     {
         $action  = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $event   = rcube_utils::get_input_value('e', rcube_utils::INPUT_POST, true);
         $success = $reload = $got_msg = false;
         $old     = null;
 
         // read old event data in order to find changes
         if ((!empty($event['_notify']) || !empty($event['_decline'])) && $action != 'new') {
             $old = $this->driver->get_event($event);
 
             // load main event if savemode is 'all' or if deleting 'future' events
             if (($event['_savemode'] == 'all' || ($event['_savemode'] == 'future' && $action == 'remove' && empty($event['_decline'])))
                 && !empty($old['recurrence_id'])
             ) {
                 $old['id'] = $old['recurrence_id'];
                 $old = $this->driver->get_event($old);
             }
         }
 
         switch ($action) {
         case "new":
             // create UID for new event
             $event['uid'] = $this->generate_uid();
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->new_event($event)) {
                 $event['id']        = $event['uid'];
                 $event['_savemode'] = 'all';
 
                 $this->cleanup_event($event);
                 $this->event_save_success($event, null, $action, true);
                 $this->talk_room_update($event);
             }
 
             $reload = $success && !empty($event['recurrence']) ? 2 : 1;
             break;
 
         case "edit":
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->edit_event($event)) {
                 $this->cleanup_event($event);
                 $this->event_save_success($event, $old, $action, $success);
                 $this->talk_room_update($event);
             }
 
             $reload = $success && (!empty($event['recurrence']) || !empty($event['_savemode']) || !empty($event['_fromcalendar'])) ? 2 : 1;
             break;
 
         case "resize":
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->resize_event($event)) {
                 $this->event_save_success($event, $old, $action, $success);
             }
 
             $reload = !empty($event['_savemode']) ? 2 : 1;
             break;
 
         case "move":
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->move_event($event)) {
                 $this->event_save_success($event, $old, $action, $success);
             }
 
             $reload = $success && !empty($event['_savemode']) ? 2 : 1;
             break;
 
         case "remove":
             // remove previous deletes
             $undo_time = $this->driver->undelete ? $this->rc->config->get('undo_timeout', 0) : 0;
 
             // search for event if only UID is given
             if (!isset($event['calendar']) && !empty($event['uid'])) {
                 if (!($event = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE))) {
                     break;
                 }
                 $undo_time = 0;
             }
 
             // Note: the driver is responsible for setting $_SESSION['calendar_event_undo']
             //       containing 'ts' and 'data' elements
             $success = $this->driver->remove_event($event, $undo_time < 1);
             $reload = (!$success || !empty($event['_savemode'])) ? 2 : 1;
 
             if ($undo_time > 0 && $success) {
                 // display message with Undo link.
                 $onclick = sprintf("%s.http_request('event', 'action=undo', %s.display_message('', 'loading'))",
                     rcmail_output::JS_OBJECT_NAME,
                     rcmail_output::JS_OBJECT_NAME
                 );
                 $msg = html::span(null, $this->gettext('successremoval'))
                     . ' ' . html::a(['onclick' => $onclick], $this->gettext('undo'));
 
                 $this->rc->output->show_message($msg, 'confirmation', null, true, $undo_time);
                 $got_msg = true;
             }
             else if ($success) {
                 $this->rc->output->show_message('calendar.successremoval', 'confirmation');
                 $got_msg = true;
             }
 
             // send cancellation for the main event
             if ($event['_savemode'] == 'all') {
                 unset($old['_instance'], $old['recurrence_date'], $old['recurrence_id']);
             }
             // send an update for the main event's recurrence rule instead of a cancellation message
             else if ($event['_savemode'] == 'future' && $success !== false && $success !== true) {
                 $event['_savemode'] = 'all';  // force event_save_success() to load master event
                 $action  = 'edit';
                 $success = true;
             }
 
             // send iTIP reply that participant has declined the event
             if ($success && !empty($event['_decline'])) {
                 $emails    = $this->get_user_emails();
                 $organizer = null;
 
                 foreach ($old['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                         $old['attendees'][$i]['status'] = 'DECLINED';
                         $reply_sender = $attendee['email'];
                     }
                 }
 
                 if ($event['_savemode'] == 'future' && $event['id'] != $old['id']) {
                     $old['thisandfuture'] = true;
                 }
 
                 $itip = $this->load_itip();
                 $itip->set_sender_email($reply_sender);
 
                 if ($organizer && $itip->send_itip_message($old, 'REPLY', $organizer, 'itipsubjectdeclined', 'itipmailbodydeclined')) {
                     $mailto = !empty($organizer['name']) ? $organizer['name'] : $organizer['email'];
                     $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
 
                     $this->rc->output->command('display_message', $msg, 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
             }
             else if ($success) {
                 $this->event_save_success($event, $old, $action, $success);
             }
 
             break;
 
         case "undo":
             // Restore deleted event
             if (!empty($_SESSION['calendar_event_undo']['data'])) {
                 $event   = $_SESSION['calendar_event_undo']['data'];
                 $success = $this->driver->restore_event($event);
             }
 
             if ($success) {
                 $this->rc->session->remove('calendar_event_undo');
                 $this->rc->output->show_message('calendar.successrestore', 'confirmation');
                 $got_msg = true;
                 $reload  = 2;
             }
 
             break;
 
         case "rsvp":
             $itip_sending  = $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
             $status        = rcube_utils::get_input_value('status', rcube_utils::INPUT_POST);
             $attendees     = rcube_utils::get_input_value('attendees', rcube_utils::INPUT_POST);
             $reply_comment = $event['comment'];
 
             $this->write_preprocess($event, 'edit');
             $ev = $this->driver->get_event($event);
             $ev['attendees'] = $event['attendees'];
             $ev['free_busy'] = $event['free_busy'];
             $ev['_savemode'] = $event['_savemode'];
             $ev['comment']   = $reply_comment;
 
             // send invitation to delegatee + add it as attendee
             if ($status == 'delegated' && !empty($event['to'])) {
                 $itip = $this->load_itip();
                 if ($itip->delegate_to($ev, $event['to'], !empty($event['rsvp']), $attendees)) {
                     $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
                     $noreply = false;
                 }
             }
 
             $event = $ev;
 
             // compose a list of attendees affected by this change
             $updated_attendees = array_filter(array_map(function($j) use ($event) {
                     return $event['attendees'][$j];
                 },
                 $attendees
             ));
 
             if ($success = $this->driver->edit_rsvp($event, $status, $updated_attendees)) {
                 $noreply = rcube_utils::get_input_value('noreply', rcube_utils::INPUT_GPC);
                 $noreply = intval($noreply) || $status == 'needs-action' || $itip_sending === 0;
                 $reload  = $event['calendar'] != $ev['calendar'] || !empty($event['recurrence']) ? 2 : 1;
                 $emails  = $this->get_user_emails();
                 $ownedResourceEmails = $this->owned_resources_emails();
                 $organizer = null;
                 $resourceConfirmation = false;
 
                 foreach ($event['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array_nocase($attendee['email'], $emails)) {
                         $reply_sender = $attendee['email'];
                     }
                     else if (!empty($attendee['cutype']) && $attendee['cutype'] == 'RESOURCE' && !empty($attendee['email']) && in_array_nocase($attendee['email'], $ownedResourceEmails)) {
                         $resourceConfirmation = true;
                         // Note on behalf of which resource this update is going to be sent out
                         $event['_resource'] = $attendee['email'];
                     }
                 }
 
                 if (!$noreply) {
                     $itip = $this->load_itip();
                     $itip->set_sender_email($reply_sender);
                     $event['thisandfuture'] = $event['_savemode'] == 'future';
                     $bodytextprefix = $resourceConfirmation ? 'itipmailbodyresource' : 'itipmailbody';
 
                     if ($organizer && $itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, $bodytextprefix . $status)) {
                         $mailto = !empty($organizer['name']) ? $organizer['name'] : $organizer['email'];
                         $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
 
                         $this->rc->output->command('display_message', $msg, 'confirmation');
                     }
                     else {
                         $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                     }
                 }
 
                 // refresh all calendars
                 if ($event['calendar'] != $ev['calendar']) {
                     $this->rc->output->command('plugin.refresh_calendar', ['source' => null, 'refetch' => true]);
                     $reload = 0;
                 }
             }
 
             break;
 
         case "dismiss":
             $event['ids'] = explode(',', $event['id']);
             $plugin  = $this->rc->plugins->exec_hook('dismiss_alarms', $event);
             $success = $plugin['success'];
 
             foreach ($event['ids'] as $id) {
                 if (strpos($id, 'cal:') === 0) {
                     $success |= $this->driver->dismiss_alarm(substr($id, 4), $event['snooze']);
                 }
             }
 
             break;
 
         case "changelog":
             $data = $this->driver->get_event_changelog($event);
             if (is_array($data) && !empty($data)) {
                 $lib = $this->lib;
                 $dtformat = $this->rc->config->get('date_format') . ' ' . $this->rc->config->get('time_format');
                 array_walk($data, function(&$change) use ($lib, $dtformat) {
                     if (!empty($change['date'])) {
                         $dt = $lib->adjust_timezone($change['date']);
 
                         if ($dt instanceof DateTimeInterface) {
                             $change['date'] = $this->rc->format_date($dt, $dtformat, false);
                         }
                     }
                 });
 
                 $this->rc->output->command('plugin.render_event_changelog', $data);
             }
             else {
                 $this->rc->output->command('plugin.render_event_changelog', false);
             }
 
             $got_msg = true;
             $reload  = false;
 
             break;
 
         case "diff":
             $data = $this->driver->get_event_diff($event, $event['rev1'], $event['rev2']);
             if (is_array($data)) {
                 // convert some properties, similar to self::_client_event()
                 $lib = $this->lib;
                 array_walk($data['changes'], function(&$change, $i) use ($event, $lib) {
                     // convert date cols
                     foreach (['start', 'end', 'created', 'changed'] as $col) {
                         if ($change['property'] == $col) {
                             $change['old'] = $lib->adjust_timezone($change['old'], strlen($change['old']) == 10)->format('c');
                             $change['new'] = $lib->adjust_timezone($change['new'], strlen($change['new']) == 10)->format('c');
                         }
                     }
                     // create textual representation for alarms and recurrence
                     if ($change['property'] == 'alarms') {
                         if (is_array($change['old'])) {
                             $change['old_'] = libcalendaring::alarm_text($change['old']);
                         }
                         if (is_array($change['new'])) {
                             $change['new_'] = libcalendaring::alarm_text(array_merge((array)$change['old'], $change['new']));
                         }
                     }
                     if ($change['property'] == 'recurrence') {
                         if (is_array($change['old'])) {
                             $change['old_'] = $lib->recurrence_text($change['old']);
                         }
                         if (is_array($change['new'])) {
                             $change['new_'] = $lib->recurrence_text(array_merge((array)$change['old'], $change['new']));
                         }
                     }
                     if ($change['property'] == 'attachments') {
                         if (is_array($change['old'])) {
                             $change['old']['classname'] = rcube_utils::file2class($change['old']['mimetype'], $change['old']['name']);
                         }
                         if (is_array($change['new'])) {
                             $change['new']['classname'] = rcube_utils::file2class($change['new']['mimetype'], $change['new']['name']);
                         }
                     }
                     // compute a nice diff of description texts
                     if ($change['property'] == 'description') {
                         $change['diff_'] = libkolab::html_diff($change['old'], $change['new']);
                     }
                 });
 
                 $this->rc->output->command('plugin.event_show_diff', $data);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectdiffnotavailable'), 'error');
             }
 
             $got_msg = true;
             $reload  = false;
 
             break;
 
         case "show":
             if ($event = $this->driver->get_event_revison($event, $event['rev'])) {
                 $this->rc->output->command('plugin.event_show_revision', $this->_client_event($event));
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectnotfound'), 'error');
             }
 
             $got_msg = true;
             $reload  = false;
             break;
 
         case "restore":
             if ($success = $this->driver->restore_event_revision($event, $event['rev'])) {
                 $_event = $this->driver->get_event($event);
                 $reload = $_event['recurrence'] ? 2 : 1;
                 $msg = $this->gettext(['name' => 'objectrestoresuccess', 'vars' => ['rev' => $event['rev']]]);
                 $this->rc->output->command('display_message', $msg, 'confirmation');
                 $this->rc->output->command('plugin.close_history_dialog');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectrestoreerror'), 'error');
                 $reload = 0;
             }
 
             $got_msg = true;
             break;
         }
 
         // show confirmation/error message
         if (!$got_msg) {
             if ($success) {
                 $this->rc->output->show_message('successfullysaved', 'confirmation');
             }
             else {
                 $this->rc->output->show_message('calendar.errorsaving', 'error');
             }
         }
 
         // unlock client
         $this->rc->output->command('plugin.unlock_saving', $success);
 
         // update event object on the client or trigger a complete refresh if too complicated
         if ($reload && empty($_REQUEST['_framed'])) {
             $args = ['source' => $event['calendar']];
             if ($reload > 1) {
                 $args['refetch'] = true;
             }
             else if ($success && $action != 'remove') {
                 $args['update'] = $this->_client_event($this->driver->get_event($event), true);
             }
             $this->rc->output->command('plugin.refresh_calendar', $args);
         }
     }
 
     /**
      * Helper method sending iTip notifications after successful event updates
      */
     private function event_save_success(&$event, $old, $action, $success)
     {
         // $success is a new event ID
         if ($success !== true) {
             // send update notification on the main event
             if ($event['_savemode'] == 'future' && !empty($event['_notify'])
                 && !empty($old['attendees']) && !empty($old['recurrence_id'])
             ) {
                 $master = $this->driver->get_event(['id' => $old['recurrence_id'], 'calendar' => $old['calendar']], 0, true);
                 unset($master['_instance'], $master['recurrence_date']);
 
                 $sent = $this->notify_attendees($master, null, $action, $event['_comment'], false);
                 if ($sent < 0) {
                     $this->rc->output->show_message('calendar.errornotifying', 'error');
                 }
 
                 $event['attendees'] = $master['attendees'];  // this tricks us into the next if clause
             }
 
             // delete old reference if saved as new
             if ($event['_savemode'] == 'future' || $event['_savemode'] == 'new') {
                 $old = null;
             }
 
             $event['id']        = $success;
             $event['_savemode'] = 'all';
         }
 
         // send out notifications
         if (!empty($event['_notify']) && (!empty($event['attendees']) || !empty($old['attendees']))) {
             $_savemode = $event['_savemode'];
 
             // send notification for the main event when savemode is 'all'
             if ($action != 'remove' && $_savemode == 'all'
                 && (!empty($event['recurrence_id']) || !empty($old['recurrence_id']) || ($old && $old['id'] != $event['id']))
             ) {
                 if (!empty($event['recurrence_id'])) {
                     $event['id'] = $event['recurrence_id'];
                 }
                 else if (!empty($old['recurrence_id'])) {
                     $event['id'] = $old['recurrence_id'];
                 }
                 else {
                     $event['id'] = $old['id'];
                 }
                 $event = $this->driver->get_event($event, 0, true);
                 unset($event['_instance'], $event['recurrence_date']);
             }
             else {
                 // make sure we have the complete record
                 $event = $action == 'remove' ? $old : $this->driver->get_event($event, 0, true);
             }
 
             $event['_savemode'] = $_savemode;
 
             if ($old) {
                 $old['thisandfuture'] = $_savemode == 'future';
             }
 
             // only notify if data really changed (TODO: do diff check on client already)
             if (!$old || $action == 'remove' || self::event_diff($event, $old)) {
                 $comment = isset($event['_comment']) ? $event['_comment'] : null;
                 $sent    = $this->notify_attendees($event, $old, $action, $comment);
 
                 if ($sent > 0) {
                     $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
                 }
                 else if ($sent < 0) {
                     $this->rc->output->show_message('calendar.errornotifying', 'error');
                 }
             }
         }
     }
 
     /**
      * Handler for load-requests from fullcalendar
      * This will return pure JSON formatted output
      */
     function load_events()
     {
         $start  = $this->input_timestamp('start', rcube_utils::INPUT_GET);
         $end    = $this->input_timestamp('end', rcube_utils::INPUT_GET);
         $query  = rcube_utils::get_input_value('q', rcube_utils::INPUT_GET);
         $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
 
         $events = $this->driver->load_events($start, $end, $query, $source);
         echo $this->encode($events, !empty($query));
         exit;
     }
 
     /**
      * Handler for requests fetching event counts for calendars
      */
     public function count_events()
     {
         // don't update session on these requests (avoiding race conditions)
         $this->rc->session->nowrite = true;
 
         $start  = rcube_utils::get_input_value('start', rcube_utils::INPUT_GET);
         $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
         $end    = rcube_utils::get_input_value('end', rcube_utils::INPUT_GET);
 
         if (!$start) {
             $start = new DateTime('today 00:00:00', $this->timezone);
             $start = $start->format('U');
         }
 
         $counts = $this->driver->count_events($source, $start, $end);
 
         $this->rc->output->command('plugin.update_counts', ['counts' => $counts]);
     }
 
     /**
      * Load event data from an iTip message attachment
      */
     public function itip_events($msgref)
     {
         $path = explode('/', $msgref);
         $msg  = array_pop($path);
         $mbox = join('/', $path);
         list($uid, $mime_id) = explode('#', $msg);
         $events = [];
 
         if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
             $partstat = 'NEEDS-ACTION';
 
             $event['id']        = $event['uid'];
             $event['temporary'] = true;
             $event['readonly']  = true;
             $event['calendar']  = '--invitation--itip';
             $event['className'] = 'fc-invitation-' . strtolower($partstat);
             $event['_mbox']     = $mbox;
             $event['_uid']      = $uid;
             $event['_part']     = $mime_id;
 
             $events[] = $this->_client_event($event, true);
 
             // add recurring instances
             if (!empty($event['recurrence'])) {
                 // Some installations can't handle all occurrences (aborting the request w/o an error in log)
                 $freq = !empty($event['recurrence']['FREQ']) ? $event['recurrence']['FREQ'] : null;
                 $end  = clone $event['start'];
                 $end->add(new DateInterval($freq == 'DAILY' ? 'P1Y' : 'P10Y'));
 
                 foreach ($this->driver->get_recurring_events($event, $event['start'], $end) as $recurring) {
                     $recurring['temporary'] = true;
                     $recurring['readonly']  = true;
                     $recurring['calendar']  = '--invitation--itip';
 
                     $events[] = $this->_client_event($recurring, true);
                 }
             }
         }
 
         return $events;
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for updated data in active calendars and sync them to the client
      */
     public function refresh($attr)
     {
         // refresh the entire calendar every 10th time to also sync deleted events
         if (rand(0, 10) == 10) {
             $this->rc->output->command('plugin.refresh_calendar', ['refetch' => true]);
             return;
         }
 
         $counts = [];
 
         foreach ($this->driver->list_calendars(calendar_driver::FILTER_ACTIVE) as $cal) {
             $events = $this->driver->load_events(
                 rcube_utils::get_input_value('start', rcube_utils::INPUT_GPC),
                 rcube_utils::get_input_value('end', rcube_utils::INPUT_GPC),
                 rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC),
                 $cal['id'],
                 1,
                 $attr['last']
             );
 
             foreach ($events as $event) {
                 $this->rc->output->command(
                     'plugin.refresh_calendar',
                     ['source' => $cal['id'], 'update' => $this->_client_event($event)]
                 );
             }
 
             // refresh count for this calendar
             if (!empty($cal['counts'])) {
                 $today = new DateTime('today 00:00:00', $this->timezone);
                 $counts += $this->driver->count_events($cal['id'], $today->format('U'));
             }
         }
 
         if (!empty($counts)) {
             $this->rc->output->command('plugin.update_counts', ['counts' => $counts]);
         }
     }
 
     /**
      * Handler for pending_alarms plugin hook triggered by the calendar module on keep-alive requests.
      * This will check for pending notifications and pass them to the client
      */
     public function pending_alarms($p)
     {
         $this->load_driver();
 
         $time = !empty($p['time']) ? $p['time'] : time();
 
         if ($alarms = $this->driver->pending_alarms($time)) {
             foreach ($alarms as $alarm) {
                 $alarm['id'] = 'cal:' . $alarm['id'];  // prefix ID with cal:
                 $p['alarms'][] = $alarm;
             }
         }
 
         // get alarms for birthdays calendar
         if (
             $this->rc->config->get('calendar_contact_birthdays')
             && $this->rc->config->get('calendar_birthdays_alarm_type') == 'DISPLAY'
         ) {
             $cache = $this->rc->get_cache('calendar.birthdayalarms', 'db');
 
             foreach ($this->driver->load_birthday_events($time, $time + 86400 * 60) as $e) {
                 $alarm = libcalendaring::get_next_alarm($e);
 
                 // overwrite alarm time with snooze value (or null if dismissed)
                 if ($dismissed = $cache->get($e['id'])) {
                     $alarm['time'] = $dismissed['notifyat'];
                 }
 
                 // add to list if alarm is set
                 if ($alarm && !empty($alarm['time']) && $alarm['time'] <= $time) {
                     $e['id']       = 'cal:bday:' . $e['id'];
                     $e['notifyat'] = $alarm['time'];
                     $p['alarms'][] = $e;
                 }
             }
         }
 
         return $p;
     }
 
     /**
      * Handler for alarm dismiss hook triggered by libcalendaring
      */
     public function dismiss_alarms($p)
     {
         $this->load_driver();
 
         foreach ((array) $p['ids'] as $id) {
             if (strpos($id, 'cal:bday:') === 0) {
                 $p['success'] |= $this->driver->dismiss_birthday_alarm(substr($id, 9), $p['snooze']);
             }
             else if (strpos($id, 'cal:') === 0) {
                 $p['success'] |= $this->driver->dismiss_alarm(substr($id, 4), $p['snooze']);
             }
         }
 
         return $p;
     }
 
     /**
      * Handler for check-recent requests which are accidentally sent to calendar
      */
     function check_recent()
     {
         // NOP
         $this->rc->output->send();
     }
 
     /**
      * Hook triggered when a contact is saved
      */
     function contact_update($p)
     {
         // clear birthdays calendar cache
         if (!empty($p['record']['birthday'])) {
             $cache = $this->rc->get_cache('calendar.birthdays', 'db');
             $cache->remove();
         }
     }
 
     /**
      *
      */
     function import_events()
     {
         // Upload progress update
         if (!empty($_GET['_progress'])) {
             $this->rc->upload_progress();
         }
 
         @set_time_limit(0);
 
         // process uploaded file if there is no error
         $err = $_FILES['_data']['error'];
 
         if (!$err && !empty($_FILES['_data']['tmp_name'])) {
             $calendar   = rcube_utils::get_input_value('calendar', rcube_utils::INPUT_GPC);
             $rangestart = !empty($_REQUEST['_range']) ? date_create("now -" . intval($_REQUEST['_range']) . " months") : 0;
 
             // extract zip file
             if ($_FILES['_data']['type'] == 'application/zip') {
                 $count = 0;
                 if (class_exists('ZipArchive', false)) {
                     $zip = new ZipArchive();
                     if ($zip->open($_FILES['_data']['tmp_name'])) {
                         $randname = uniqid('zip-' . session_id(), true);
                         $tmpdir = slashify($this->rc->config->get('temp_dir', sys_get_temp_dir())) . $randname;
                         mkdir($tmpdir, 0700);
 
                         // extract each ical file from the archive and import it
                         for ($i = 0; $i < $zip->numFiles; $i++) {
                             $filename = $zip->getNameIndex($i);
                             if (preg_match('/\.ics$/i', $filename)) {
                                 $tmpfile = $tmpdir . '/' . basename($filename);
                                 if (copy('zip://' . $_FILES['_data']['tmp_name'] . '#'.$filename, $tmpfile)) {
                                     $count += $this->import_from_file($tmpfile, $calendar, $rangestart, $errors);
                                     unlink($tmpfile);
                                 }
                             }
                         }
 
                         rmdir($tmpdir);
                         $zip->close();
                     }
                     else {
                         $errors = 1;
                         $msg = 'Failed to open zip file.';
                     }
                 }
                 else {
                     $errors = 1;
                     $msg = 'Zip files are not supported for import.';
                 }
             }
             else {
                 // attempt to import teh uploaded file directly
                 $count = $this->import_from_file($_FILES['_data']['tmp_name'], $calendar, $rangestart, $errors);
             }
 
             if ($count) {
                 $this->rc->output->command('display_message', $this->gettext(['name' => 'importsuccess', 'vars' => ['nr' => $count]]), 'confirmation');
                 $this->rc->output->command('plugin.import_success', ['source' => $calendar, 'refetch' => true]);
             }
             else if (!$errors) {
                 $this->rc->output->command('display_message', $this->gettext('importnone'), 'notice');
                 $this->rc->output->command('plugin.import_success', ['source' => $calendar]);
             }
             else {
                 $this->rc->output->command('plugin.import_error', ['message' => $this->gettext('importerror') . ($msg ? ': ' . $msg : '')]);
             }
         }
         else {
             if ($err == UPLOAD_ERR_INI_SIZE || $err == UPLOAD_ERR_FORM_SIZE) {
                 $max = $this->rc->show_bytes(parse_bytes(ini_get('upload_max_filesize')));
                 $msg = $this->rc->gettext(['name' => 'filesizeerror', 'vars' => ['size' => $max]]);
             }
             else {
                 $msg = $this->rc->gettext('fileuploaderror');
             }
 
             $this->rc->output->command('plugin.import_error', ['message' => $msg]);
         }
 
         $this->rc->output->send('iframe');
     }
 
     /**
      * Helper function to parse and import a single .ics file
      */
     private function import_from_file($filepath, $calendar, $rangestart, &$errors)
     {
         $user_email = $this->rc->user->get_username();
         $ical       = $this->get_ical();
         $errors     = !$ical->fopen($filepath);
 
         $count = $i = 0;
 
         foreach ($ical as $event) {
             // keep the browser connection alive on long import jobs
             if (++$i > 100 && $i % 100 == 0) {
                 echo "<!-- -->";
                 ob_flush();
             }
 
             // TODO: correctly handle recurring events which start before $rangestart
             if ($rangestart && $event['end'] < $rangestart
                 && (empty($event['recurrence']) || (!empty($event['recurrence']['until']) && $event['recurrence']['until'] < $rangestart))
             ) {
                 continue;
             }
 
             $event['_owner']   = $user_email;
             $event['calendar'] = $calendar;
 
             if ($this->driver->new_event($event)) {
                 $count++;
             }
             else {
                 $errors++;
             }
         }
 
         return $count;
     }
 
     /**
      * Construct the ics file for exporting events to iCalendar format;
      */
     function export_events($terminate = true)
     {
         $start       = rcube_utils::get_input_value('start', rcube_utils::INPUT_GET);
         $end         = rcube_utils::get_input_value('end', rcube_utils::INPUT_GET);
         $event_id    = rcube_utils::get_input_value('id', rcube_utils::INPUT_GET);
         $attachments = rcube_utils::get_input_value('attachments', rcube_utils::INPUT_GET);
         $calid       = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
 
         if (!isset($start)) {
             $start = 'today -1 year';
         }
         if (!is_numeric($start)) {
             $start = strtotime($start . ' 00:00:00');
         }
         if (!$end) {
             $end = 'today +10 years';
         }
         if (!is_numeric($end)) {
             $end = strtotime($end . ' 23:59:59');
         }
 
         $filename  = $calid;
         $calendars = $this->driver->list_calendars();
         $events    = [];
 
         if (!empty($calendars[$calid])) {
             $filename = !empty($calendars[$calid]['name']) ? $calendars[$calid]['name'] : $calid;
             $filename = asciiwords(html_entity_decode($filename));  // to 7bit ascii
 
             if (!empty($event_id)) {
                 if ($event = $this->driver->get_event(['calendar' => $calid, 'id' => $event_id], 0, true)) {
                     if (!empty($event['recurrence_id'])) {
                         $event = $this->driver->get_event(['calendar' => $calid, 'id' => $event['recurrence_id']], 0, true);
                     }
 
                     $events   = [$event];
                     $filename = asciiwords($event['title']);
 
                     if (empty($filename)) {
                         $filename = 'event';
                     }
                 }
             }
             else {
                 $events = $this->driver->load_events($start, $end, null, $calid, 0);
                 if (empty($filename)) {
                     $filename = $calid;
                 }
             }
         }
 
         header("Content-Type: text/calendar");
         header("Content-Disposition: inline; filename=".$filename.'.ics');
 
         $this->get_ical()->export($events, '', true, $attachments ? [$this->driver, 'get_attachment_body'] : null);
 
         if ($terminate) {
             exit;
         }
     }
 
     /**
      * Handler for iCal feed requests
      */
     function ical_feed_export()
     {
         $session_exists = !empty($_SESSION['user_id']);
 
         // process HTTP auth info
         if (!empty($_SERVER['PHP_AUTH_USER']) && isset($_SERVER['PHP_AUTH_PW'])) {
             $_POST['_user'] = $_SERVER['PHP_AUTH_USER']; // used for rcmail::autoselect_host()
             $auth = $this->rc->plugins->exec_hook('authenticate', [
                 'host' => $this->rc->autoselect_host(),
                 'user' => trim($_SERVER['PHP_AUTH_USER']),
                 'pass' => $_SERVER['PHP_AUTH_PW'],
                 'cookiecheck' => true,
                 'valid'       => true,
             ]);
 
             if ($auth['valid'] && !$auth['abort']) {
                 $this->rc->login($auth['user'], $auth['pass'], $auth['host']);
             }
         }
 
         // require HTTP auth
         if (empty($_SESSION['user_id'])) {
             header('WWW-Authenticate: Basic realm="Kolab Calendar"');
             header('HTTP/1.0 401 Unauthorized');
             exit;
         }
 
         // decode calendar feed hash
         $format  = 'ics';
         $calhash = rcube_utils::get_input_value('_cal', rcube_utils::INPUT_GET);
 
         if (preg_match(($suff_regex = '/\.([a-z0-9]{3,5})$/i'), $calhash, $m)) {
             $format  = strtolower($m[1]);
             $calhash = preg_replace($suff_regex, '', $calhash);
         }
 
         if (!strpos($calhash, ':')) {
             $calhash = base64_decode($calhash);
         }
 
         list($user, $_GET['source']) = explode(':', $calhash, 2);
 
         // sanity check user
         if ($this->rc->user->get_username() == $user) {
             $this->setup();
             $this->load_driver();
             $this->export_events(false);
         }
         else {
             header('HTTP/1.0 404 Not Found');
         }
 
         // don't save session data
         if (!$session_exists) {
             session_destroy();
         }
 
         exit;
     }
 
     /**
      *
      */
     function load_settings()
     {
         $this->lib->load_settings();
         $this->defaults += $this->lib->defaults;
 
         $settings = [];
 
         // configuration
         $settings['default_view']     = (string) $this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view']);
         $settings['timeslots']        = (int) $this->rc->config->get('calendar_timeslots', $this->defaults['calendar_timeslots']);
         $settings['first_day']        = (int) $this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
         $settings['first_hour']       = (int) $this->rc->config->get('calendar_first_hour', $this->defaults['calendar_first_hour']);
         $settings['work_start']       = (int) $this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']);
         $settings['work_end']         = (int) $this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']);
         $settings['agenda_range']     = (int) $this->rc->config->get('calendar_agenda_range', $this->defaults['calendar_agenda_range']);
         $settings['event_coloring']   = (int) $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
         $settings['time_indicator']   = (int) $this->rc->config->get('calendar_time_indicator', $this->defaults['calendar_time_indicator']);
         $settings['invite_shared']    = (int) $this->rc->config->get('calendar_allow_invite_shared', $this->defaults['calendar_allow_invite_shared']);
         $settings['itip_notify']      = (int) $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
         $settings['show_weekno']      = (int) $this->rc->config->get('calendar_show_weekno', $this->defaults['calendar_show_weekno']);
         $settings['default_calendar'] = $this->rc->config->get('calendar_default_calendar');
         $settings['invitation_calendars'] = (bool) $this->rc->config->get('kolab_invitation_calendars', false);
 
         // 'table' view has been replaced by 'list' view
         if ($settings['default_view'] == 'table') {
             $settings['default_view'] = 'list';
         }
 
         // get user identity to create default attendee
         if ($this->ui->screen == 'calendar') {
             foreach ($this->rc->user->list_emails() as $rec) {
                 if (empty($identity)) {
                     $identity = $rec;
                 }
 
                 $identity['emails'][] = $rec['email'];
                 $settings['identities'][$rec['identity_id']] = $rec['email'];
             }
 
             $identity['emails'][] = $this->rc->user->get_username();
             $identity['ownedResources'] = $this->owned_resources_emails();
             $settings['identity'] = [
                 'name'   => $identity['name'],
                 'email'  => strtolower($identity['email']),
                 'emails' => ';' . strtolower(join(';', $identity['emails'])),
                 'ownedResources' => ';' . strtolower(join(';', $identity['ownedResources']))
             ];
         }
 
         // freebusy token authentication URL
         if (($url = $this->rc->config->get('calendar_freebusy_session_auth_url'))
             && ($uniqueid = $this->rc->config->get('kolab_uniqueid'))
         ) {
             if ($url === true) {
                 $url = '/freebusy';
             }
             $url = rtrim(rcube_utils::resolve_url($url), '/ ');
             $url .= '/' . urlencode($this->rc->get_user_name());
             $url .= '/' . urlencode($uniqueid);
 
             $settings['freebusy_url'] = $url;
         }
 
         return $settings;
     }
 
     /**
      * Encode events as JSON
      *
      * @param array Events as array
      * @param bool  Add CSS class names according to calendar and categories
      *
      * @return string JSON encoded events
      */
     function encode($events, $addcss = false)
     {
         $json = [];
         foreach ($events as $event) {
             $json[] = $this->_client_event($event, $addcss);
         }
         return rcube_output::json_serialize($json);
     }
 
     /**
      * Convert an event object to be used on the client
      */
     private function _client_event($event, $addcss = false)
     {
         // compose a human readable strings for alarms_text and recurrence_text
         if (!empty($event['valarms'])) {
             $event['alarms_text'] = libcalendaring::alarms_text($event['valarms']);
             $event['valarms'] = libcalendaring::to_client_alarms($event['valarms']);
         }
 
         if (!empty($event['recurrence'])) {
             $event['recurrence_text'] = $this->lib->recurrence_text($event['recurrence']);
             $event['recurrence'] = $this->lib->to_client_recurrence($event['recurrence'], $event['allday']);
             unset($event['recurrence_date']);
         }
 
         if (!empty($event['attachments'])) {
             foreach ($event['attachments'] as $k => $attachment) {
                 $event['attachments'][$k]['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
                 unset($event['attachments'][$k]['data'], $event['attachments'][$k]['content']);
 
                 if (empty($attachment['id'])) {
                     $event['attachments'][$k]['id'] = $k;
                 }
             }
         }
 
         // convert link URIs references into structs
         if (array_key_exists('links', $event)) {
             foreach ((array) $event['links'] as $i => $link) {
                 if (strpos($link, 'imap://') === 0 && ($msgref = $this->driver->get_message_reference($link))) {
                     $event['links'][$i] = $msgref;
                 }
             }
         }
 
         // check for organizer in attendees list
         $organizer = null;
         foreach ((array) $event['attendees'] as $i => $attendee) {
             if ($attendee['role'] == 'ORGANIZER') {
                 $organizer = $attendee;
             }
             if (!empty($attendee['status']) && $attendee['status'] == 'DELEGATED' && empty($attendee['rsvp'])) {
                 $event['attendees'][$i]['noreply'] = true;
             }
             else {
                 unset($event['attendees'][$i]['noreply']);
             }
         }
 
         if ($organizer === null && !empty($event['organizer'])) {
             $organizer = $event['organizer'];
             $organizer['role'] = 'ORGANIZER';
             if (!is_array($event['attendees'])) {
                 $event['attendees'] = [$organizer];
             }
         }
 
         // Convert HTML description into plain text
         if ($this->is_html($event)) {
             $h2t = new rcube_html2text($event['description'], false, true, 0);
             $event['description'] = trim($h2t->get_text());
         }
 
         // mapping url => vurl, allday => allDay because of the fullcalendar client script
         $event['vurl']   = $event['url'];
         $event['allDay'] = !empty($event['allday']);
         unset($event['url']);
         unset($event['allday']);
 
         $event['className'] = !empty($event['className']) ? explode(' ', $event['className']) : [];
 
         if ($event['allDay']) {
             $event['end'] = $event['end']->add(new DateInterval('P1D'));
         }
 
         if (!empty($_GET['mode']) && $_GET['mode'] == 'print') {
             $event['editable'] = false;
         }
 
         return [
             '_id'     => $event['calendar'] . ':' . $event['id'],  // unique identifier for fullcalendar
             'start'   => $this->lib->adjust_timezone($event['start'], $event['allDay'])->format('c'),
             'end'     => $this->lib->adjust_timezone($event['end'], $event['allDay'])->format('c'),
             // 'changed' might be empty for event recurrences (Bug #2185)
             'changed' => !empty($event['changed']) ? $this->lib->adjust_timezone($event['changed'])->format('c') : null,
             'created' => !empty($event['created']) ? $this->lib->adjust_timezone($event['created'])->format('c') : null,
             'title'       => strval($event['title']),
             'description' => strval($event['description']),
             'location'    => strval($event['location']),
         ] + $event;
     }
 
     /**
      * Generate a unique identifier for an event
      */
     public function generate_uid()
     {
         return strtoupper(md5(time() . uniqid(rand())) . '-' . substr(md5($this->rc->user->get_username()), 0, 16));
     }
 
     /**
      * TEMPORARY: generate random event data for testing
      * Create events by opening http://<roundcubeurl>/?_task=calendar&_action=randomdata&_num=500&_date=2014-08-01&_dev=120
      */
     public function generate_randomdata()
     {
         @set_time_limit(0);
 
         $num   = !empty($_REQUEST['_num']) ? intval($_REQUEST['_num']) : 100;
         $date  = !empty($_REQUEST['_date']) ? $_REQUEST['_date'] : 'now';
         $dev   = !empty($_REQUEST['_dev']) ? $_REQUEST['_dev'] : 30;
         $cats  = array_keys($this->driver->list_categories());
         $cals  = $this->driver->list_calendars(calendar_driver::FILTER_ACTIVE);
         $count = 0;
 
         while ($count++ < $num) {
             $spread   = intval($dev) * 86400; // days
             $refdate  = strtotime($date);
             $start    = round(($refdate + rand(-$spread, $spread)) / 600) * 600;
             $duration = round(rand(30, 360) / 30) * 30 * 60;
             $allday   = rand(0,20) > 18;
             $alarm    = rand(-30,12) * 5;
             $fb       = rand(0,2);
 
             if (date('G', $start) > 23) {
                 $start -= 3600;
             }
 
             if ($allday) {
                 $start    = strtotime(date('Y-m-d 00:00:00', $start));
                 $duration = 86399;
             }
 
             $title = '';
             $len = rand(2, 12);
             $words = explode(" ", "The Hough transform is named after Paul Hough who patented the method in 1962."
                 . " It is a technique which can be used to isolate features of a particular shape within an image."
                 . " Because it requires that the desired features be specified in some parametric form, the classical"
                 . " Hough transform is most commonly used for the de- tection of regular curves such as lines, circles,"
                 . " ellipses, etc. A generalized Hough transform can be employed in applications where a simple"
                 . " analytic description of a feature(s) is not possible. Due to the computational complexity of"
                 . " the generalized Hough algorithm, we restrict the main focus of this discussion to the classical"
                 . " Hough transform. Despite its domain restrictions, the classical Hough transform (hereafter"
                 . " referred to without the classical prefix ) retains many applications, as most manufac- tured"
                 . " parts (and many anatomical parts investigated in medical imagery) contain feature boundaries"
                 . " which can be described by regular curves. The main advantage of the Hough transform technique"
                 . " is that it is tolerant of gaps in feature boundary descriptions and is relatively unaffected"
                 . " by image noise.");
             // $chars = "!# abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890";
             for ($i = 0; $i < $len; $i++) {
                 $title .= $words[rand(0,count($words)-1)] . " ";
             }
 
             $this->driver->new_event([
                 'uid'        => $this->generate_uid(),
                 'start'      => new DateTime('@'.$start),
                 'end'        => new DateTime('@'.($start + $duration)),
                 'allday'     => $allday,
                 'title'      => rtrim($title),
                 'free_busy'  => $fb == 2 ? 'outofoffice' : ($fb ? 'busy' : 'free'),
                 'categories' => $cats[array_rand($cats)],
                 'calendar'   => array_rand($cals),
                 'alarms'     => $alarm > 0 ? "-{$alarm}M:DISPLAY" : '',
                 'priority'   => rand(0,9),
             ]);
         }
 
         $this->rc->output->redirect('');
     }
 
     /**
      * Handler for attachments upload
      */
     public function attachment_upload()
     {
         $handler = new kolab_attachments_handler();
         $handler->attachment_upload(self::SESSION_KEY, 'cal-');
     }
 
     /**
      * Handler for attachments download/displaying
      */
     public function attachment_get()
     {
         $handler = new kolab_attachments_handler();
 
         // show loading page
         if (!empty($_GET['_preload'])) {
             return $handler->attachment_loading_page();
         }
 
         $event_id = rcube_utils::get_input_value('_event', rcube_utils::INPUT_GPC);
         $calendar = rcube_utils::get_input_value('_cal', rcube_utils::INPUT_GPC);
         $id       = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
         $rev      = rcube_utils::get_input_value('_rev', rcube_utils::INPUT_GPC);
 
         $event = ['id' => $event_id, 'calendar' => $calendar, 'rev' => $rev];
 
         if ($calendar == '--invitation--itip') {
             $uid  = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GPC);
             $part = rcube_utils::get_input_value('_part', rcube_utils::INPUT_GPC);
             $mbox = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_GPC);
 
             $event      = $this->lib->mail_get_itip_object($mbox, $uid, $part, 'event');
             $attachment = $event['attachments'][$id];
             $attachment['body'] = &$attachment['data'];
         }
         else {
             $attachment = $this->driver->get_attachment($id, $event);
         }
 
         // show part page
         if (!empty($_GET['_frame'])) {
             $handler->attachment_page($attachment);
         }
         // deliver attachment content
         else if ($attachment) {
             if ($calendar != '--invitation--itip') {
                 $attachment['body'] = $this->driver->get_attachment_body($id, $event);
             }
 
             $handler->attachment_get($attachment);
         }
 
         // if we arrive here, the requested part was not found
         header('HTTP/1.1 404 Not Found');
         exit;
     }
 
     /**
      * Determine whether the given event description is HTML formatted
      */
     private function is_html($event)
     {
           // check for opening and closing <html> or <body> tags
         return preg_match('/<(html|body)(\s+[a-z]|>)/', $event['description'], $m)
             && strpos($event['description'], '</'.$m[1].'>') > 0;
     }
 
     /**
      * Prepares new/edited event properties before save
      */
     private function write_preprocess(&$event, $action)
     {
         // Remove double timezone specification (T2313)
         $event['start'] = preg_replace('/\s*\(.*\)/', '', $event['start']);
         $event['end']   = preg_replace('/\s*\(.*\)/', '', $event['end']);
 
         // convert dates into DateTime objects in user's current timezone
         $event['start']  = new DateTime($event['start'], $this->timezone);
         $event['end']    = new DateTime($event['end'], $this->timezone);
         $event['allday'] = !empty($event['allDay']);
         unset($event['allDay']);
 
         // start/end is all we need for 'move' action (#1480)
         if ($action == 'move') {
             return true;
         }
 
         // convert the submitted recurrence settings
         if (!empty($event['recurrence'])) {
             $event['recurrence'] = $this->lib->from_client_recurrence($event['recurrence'], $event['start']);
 
             // align start date with the first occurrence
             if (!empty($event['recurrence']) && !empty($event['syncstart'])
                 && (empty($event['_savemode']) || $event['_savemode'] == 'all')
             ) {
                 $next = $this->find_first_occurrence($event);
 
                 if (!$next) {
                     $this->rc->output->show_message('calendar.recurrenceerror', 'error');
                     return false;
                 }
                 else if ($event['start'] != $next) {
                     $diff = $event['start']->diff($event['end'], true);
 
                     $event['start'] = $next;
                     $event['end']   = clone $next;
                     $event['end']->add($diff);
                 }
             }
         }
 
         // convert the submitted alarm values
         if (!empty($event['valarms'])) {
             $event['valarms'] = libcalendaring::from_client_alarms($event['valarms']);
         }
 
         $attachments = [];
         $eventid     = 'cal-' . (!empty($event['id']) ? $event['id'] : 'new');
 
         if (!empty($_SESSION[self::SESSION_KEY]) && $_SESSION[self::SESSION_KEY]['id'] == $eventid) {
             if (!empty($_SESSION[self::SESSION_KEY]['attachments'])) {
                 foreach ($_SESSION[self::SESSION_KEY]['attachments'] as $id => $attachment) {
                     if (!empty($event['attachments']) && in_array($id, $event['attachments'])) {
                         $attachments[$id] = $this->rc->plugins->exec_hook('attachment_get', $attachment);
                     }
                 }
             }
         }
 
         $event['attachments'] = $attachments;
 
         // convert link references into simple URIs
         if (array_key_exists('links', $event)) {
             $event['links'] = array_map(function($link) {
                     return is_array($link) ? $link['uri'] : strval($link);
                 },
                 (array) $event['links']
             );
         }
 
         // check for organizer in attendees
         if ($action == 'new' || $action == 'edit') {
             if (empty($event['attendees'])) {
                 $event['attendees'] = [];
             }
 
             $emails = $this->get_user_emails();
             $organizer = $owner = false;
 
             foreach ((array) $event['attendees'] as $i => $attendee) {
                 if ($attendee['role'] == 'ORGANIZER') {
                     $organizer = $i;
                 }
                 if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                     $owner = $i;
                 }
                 if (!isset($attendee['rsvp'])) {
                     $event['attendees'][$i]['rsvp'] = true;
                 }
                 else if (is_string($attendee['rsvp'])) {
                     $event['attendees'][$i]['rsvp'] = $attendee['rsvp'] == 'true' || $attendee['rsvp'] == '1';
                 }
             }
 
             if (!empty($event['_identity'])) {
                 $identity = $this->rc->user->get_identity($event['_identity']);
             }
 
             // set new organizer identity
             if ($organizer !== false && !empty($identity)) {
                 $event['attendees'][$organizer]['name']  = $identity['name'];
                 $event['attendees'][$organizer]['email'] = $identity['email'];
             }
             // set owner as organizer if yet missing
             else if ($organizer === false && $owner !== false) {
                 $event['attendees'][$owner]['role'] = 'ORGANIZER';
                 unset($event['attendees'][$owner]['rsvp']);
             }
             // fallback to the selected identity
             else if ($organizer === false && !empty($identity)) {
                 $event['attendees'][] = [
                     'role'  => 'ORGANIZER',
                     'name'  => $identity['name'],
                     'email' => $identity['email'],
                 ];
             }
         }
 
         // mapping url => vurl because of the fullcalendar client script
         if (array_key_exists('vurl', $event)) {
             $event['url'] = $event['vurl'];
             unset($event['vurl']);
         }
 
         return true;
     }
 
     /**
      * Releases some resources after successful event save
      */
     private function cleanup_event(&$event)
     {
         // remove temp. attachment files
         if (!empty($_SESSION[self::SESSION_KEY]) && ($eventid = $_SESSION[self::SESSION_KEY]['id'])) {
             $this->rc->plugins->exec_hook('attachments_cleanup', ['group' => $eventid]);
             $this->rc->session->remove(self::SESSION_KEY);
         }
     }
 
     /**
      * Send out an invitation/notification to all event attendees
      */
     private function notify_attendees($event, $old, $action = 'edit', $comment = null, $rsvp = null)
     {
         $is_cancelled = false;
         if ($action == 'remove' || ($event['status'] == 'CANCELLED' && $old['status'] != $event['status'])) {
             $event['cancelled'] = true;
             $is_cancelled = true;
         }
 
         if ($rsvp === null) {
             $rsvp = !$old || $event['sequence'] > $old['sequence'];
         }
 
         $itip        = $this->load_itip();
         $emails      = $this->get_user_emails();
         $itip_notify = (int) $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
         // add comment to the iTip attachment
         $event['comment'] = $comment;
 
         // set a valid recurrence-id if this is a recurrence instance
         libcalendaring::identify_recurrence_instance($event);
 
         // compose multipart message using PEAR:Mail_Mime
         $method  = $action == 'remove' ? 'CANCEL' : 'REQUEST';
         $message = $itip->compose_itip_message($event, $method, $rsvp);
 
         // list existing attendees from $old event
         $old_attendees = [];
         if (!empty($old['attendees'])) {
             foreach ((array) $old['attendees'] as $attendee) {
                 $old_attendees[] = $attendee['email'];
             }
         }
 
         // send to every attendee
         $sent    = 0;
         $current = [];
         foreach ((array) $event['attendees'] as $attendee) {
             // skip myself for obvious reasons
             if (empty($attendee['email']) || in_array(strtolower($attendee['email']), $emails)) {
                 continue;
             }
 
             $current[] = strtolower($attendee['email']);
 
             // skip if notification is disabled for this attendee
             if (!empty($attendee['noreply']) && $itip_notify & 2) {
                 continue;
             }
 
             // skip if this attendee has delegated and set RSVP=FALSE
             if ($attendee['status'] == 'DELEGATED' && $attendee['rsvp'] === false) {
                 continue;
             }
 
             // which template to use for mail text
             $is_new   = !in_array($attendee['email'], $old_attendees);
             $is_rsvp  = $is_new || $event['sequence'] > $old['sequence'];
             $bodytext = $is_cancelled ? 'eventcancelmailbody' : ($is_new ? 'invitationmailbody' : 'eventupdatemailbody');
             $subject  = $is_cancelled ? 'eventcancelsubject'  : ($is_new ? 'invitationsubject' : ($event['title'] ? 'eventupdatesubject' : 'eventupdatesubjectempty'));
 
             $event['comment'] = $comment;
 
             // finally send the message
             if ($itip->send_itip_message($event, $method, $attendee, $subject, $bodytext, $message, $is_rsvp)) {
                 $sent++;
             }
             else {
                 $sent = -100;
             }
         }
 
         // TODO: on change of a recurring (main) event, also send updates to differing attendess of recurrence exceptions
 
         // send CANCEL message to removed attendees
         if (!empty($old['attendees'])) {
             foreach ($old['attendees'] as $attendee) {
                 if ($attendee['role'] == 'ORGANIZER'
                     || empty($attendee['email'])
                     || in_array(strtolower($attendee['email']), $current)
                 ) {
                     continue;
                 }
 
                 $vevent = $old;
                 $vevent['cancelled'] = $is_cancelled;
                 $vevent['attendees'] = [$attendee];
                 $vevent['comment']   = $comment;
 
                 if ($itip->send_itip_message($vevent, 'CANCEL', $attendee, 'eventcancelsubject', 'eventcancelmailbody')) {
                     $sent++;
                 }
                 else {
                     $sent = -100;
                 }
             }
         }
 
         return $sent;
     }
 
     /**
      * Echo simple free/busy status text for the given user and time range
      */
     public function freebusy_status()
     {
         $email = rcube_utils::get_input_value('email', rcube_utils::INPUT_GPC);
         $start = $this->input_timestamp('start', rcube_utils::INPUT_GPC);
         $end   = $this->input_timestamp('end', rcube_utils::INPUT_GPC);
 
         if (!$start) $start = time();
         if (!$end) $end = $start + 3600;
 
         $status = 'UNKNOWN';
         $fbtypemap = [
             calendar::FREEBUSY_UNKNOWN   => 'UNKNOWN',
             calendar::FREEBUSY_FREE      => 'FREE',
             calendar::FREEBUSY_BUSY      => 'BUSY',
             calendar::FREEBUSY_TENTATIVE => 'TENTATIVE',
             calendar::FREEBUSY_OOF       => 'OUT-OF-OFFICE'
         ];
 
         // if the backend has free-busy information
         $fblist = $this->driver->get_freebusy_list($email, $start, $end);
 
         if (is_array($fblist)) {
             $status = 'FREE';
 
             foreach ($fblist as $slot) {
                 list($from, $to, $type) = $slot;
                 if ($from < $end && $to > $start) {
                     $status = isset($type) && !empty($fbtypemap[$type]) ? $fbtypemap[$type] : 'BUSY';
                     break;
                 }
             }
         }
 
         // let this information be cached for 5min
         $this->rc->output->future_expire_header(300);
 
         echo $status;
         exit;
     }
 
     /**
      * Return a list of free/busy time slots within the given period
      * Echo data in JSON encoding
      */
     public function freebusy_times()
     {
         $email = rcube_utils::get_input_value('email', rcube_utils::INPUT_GPC);
         $start = $this->input_timestamp('start', rcube_utils::INPUT_GPC);
         $end   = $this->input_timestamp('end', rcube_utils::INPUT_GPC);
         $interval  = intval(rcube_utils::get_input_value('interval', rcube_utils::INPUT_GPC));
         $strformat = $interval > 60 ? 'Ymd' : 'YmdHis';
 
         if (!$start) $start = time();
         if (!$end)   $end = $start + 86400 * 30;
         if (!$interval) $interval = 60;  // 1 hour
 
         if (!$dte) {
             $dts = new DateTime('@'.$start);
             $dts->setTimezone($this->timezone);
         }
 
         $fblist = $this->driver->get_freebusy_list($email, $start, $end);
         $slots  = '';
 
         // prepare freebusy list before use (for better performance)
         if (is_array($fblist)) {
             foreach ($fblist as $idx => $slot) {
                 list($from, $to, ) = $slot;
 
                 // check for possible all-day times
                 if (gmdate('His', $from) == '000000' && gmdate('His', $to) == '235959') {
                     // shift into the user's timezone for sane matching
                     $fblist[$idx][0] -= $this->gmt_offset;
                     $fblist[$idx][1] -= $this->gmt_offset;
                 }
             }
         }
 
         // build a list from $start till $end with blocks representing the fb-status
         for ($s = 0, $t = $start; $t <= $end; $s++) {
             $t_end = $t + $interval * 60;
             $dt = new DateTime('@'.$t);
             $dt->setTimezone($this->timezone);
 
             // determine attendee's status
             if (is_array($fblist)) {
                 $status = self::FREEBUSY_FREE;
 
                 foreach ($fblist as $slot) {
                     list($from, $to, $type) = $slot;
 
                     if ($from < $t_end && $to > $t) {
                         $status = isset($type) ? $type : self::FREEBUSY_BUSY;
                         if ($status == self::FREEBUSY_BUSY) {
                             // can't get any worse :-)
                             break;
                         }
                     }
                 }
             }
             else {
                 $status = self::FREEBUSY_UNKNOWN;
             }
 
             // use most compact format, assume $status is one digit/character
             $slots .= $status;
             $t = $t_end;
         }
 
         $dte = new DateTime('@'.$t_end);
         $dte->setTimezone($this->timezone);
 
         // let this information be cached for 5min
         $this->rc->output->future_expire_header(300);
 
         echo rcube_output::json_serialize([
             'email' => $email,
             'start' => $dts->format('c'),
             'end'   => $dte->format('c'),
             'interval' => $interval,
             'slots' => $slots,
         ]);
         exit;
     }
 
     /**
      * Handler for printing calendars
      */
     public function print_view()
     {
         $title = $this->gettext('print');
 
         $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
         if (!in_array($view, ['agendaWeek', 'agendaDay', 'month', 'list'])) {
             $view = 'agendaDay';
         }
 
         $this->rc->output->set_env('view', $view);
 
         if ($date = rcube_utils::get_input_value('date', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('date', $date);
         }
 
         if ($range = rcube_utils::get_input_value('range', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('listRange', intval($range));
         }
 
         if ($search = rcube_utils::get_input_value('search', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('search', $search);
             $title .= ' "' . $search . '"';
         }
 
         // Add JS to the page
         $this->ui->addJS();
 
         $this->register_handler('plugin.calendar_css', [$this->ui, 'calendar_css']);
         $this->register_handler('plugin.calendar_list', [$this->ui, 'calendar_list']);
 
         $this->rc->output->set_pagetitle($title);
         $this->rc->output->send('calendar.print');
     }
 
     /**
      * Compare two event objects and return differing properties
      *
      * @param array Event A
      * @param array Event B
      *
      * @return array List of differing event properties
      */
     public static function event_diff($a, $b)
     {
         $diff   = [];
         $ignore = ['changed' => 1, 'attachments' => 1];
 
         foreach (array_unique(array_merge(array_keys($a), array_keys($b))) as $key) {
             if (empty($ignore[$key]) && $key[0] != '_') {
                 $av = isset($a[$key]) ? $a[$key] : null;
                 $bv = isset($b[$key]) ? $b[$key] : null;
 
                 if ($av != $bv) {
                     $diff[] = $key;
                 }
             }
         }
 
         // only compare number of attachments
         $ac = !empty($a['attachments']) ? count($a['attachments']) : 0;
         $bc = !empty($b['attachments']) ? count($b['attachments']) : 0;
 
         if ($ac != $bc) {
             $diff[] = 'attachments';
         }
 
         return $diff;
     }
 
     /**
      * Update attendee properties on the given event object
      *
      * @param array The event object to be altered
      * @param array List of hash arrays each represeting an updated/added attendee
      */
     public static function merge_attendee_data(&$event, $attendees, $removed = null)
     {
         if (!empty($attendees) && !is_array($attendees[0])) {
             $attendees = [$attendees];
         }
 
         foreach ($attendees as $attendee) {
             $found = false;
 
             foreach ($event['attendees'] as $i => $candidate) {
                 if ($candidate['email'] == $attendee['email']) {
                     $event['attendees'][$i] = $attendee;
                     $found = true;
                     break;
                 }
             }
 
             if (!$found) {
                 $event['attendees'][] = $attendee;
             }
         }
 
         // filter out removed attendees
         if (!empty($removed)) {
             $event['attendees'] = array_filter($event['attendees'], function($attendee) use ($removed) {
                 return !in_array($attendee['email'], $removed);
             });
         }
     }
 
     /****  Resource management functions  ****/
 
     /**
      * Getter for the configured implementation of the resource directory interface
      */
     private function resources_directory()
     {
         if (!empty($this->resources_dir)) {
             return $this->resources_dir;
         }
 
         if ($driver_name = $this->rc->config->get('calendar_resources_driver')) {
             $driver_class = 'resources_driver_' . $driver_name;
 
             require_once($this->home . '/drivers/resources_driver.php');
             require_once($this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php');
 
             $this->resources_dir = new $driver_class($this);
         }
 
         return $this->resources_dir;
     }
 
     /**
      * Handler for resoruce autocompletion requests
      */
     public function resources_autocomplete()
     {
         $search  = rcube_utils::get_input_value('_search', rcube_utils::INPUT_GPC, true);
         $sid     = rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC);
         $maxnum  = (int)$this->rc->config->get('autocomplete_max', 15);
         $results = [];
 
         if ($directory = $this->resources_directory()) {
             foreach ($directory->load_resources($search, $maxnum) as $rec) {
                 $results[]  = [
                     'name'  => $rec['name'],
                     'email' => $rec['email'],
                     'type'  => $rec['_type'],
                 ];
             }
         }
 
         $this->rc->output->command('ksearch_query_results', $results, $search, $sid);
         $this->rc->output->send();
     }
 
     /**
      * Handler for load-requests for resource data
      */
     function resources_list()
     {
         $data = [];
 
         if ($directory = $this->resources_directory()) {
             foreach ($directory->load_resources() as $rec) {
                 $data[] = $rec;
             }
         }
 
         $this->rc->output->command('plugin.resource_data', $data);
         $this->rc->output->send();
     }
 
     /**
      * Handler for requests loading resource owner information
      */
     function resources_owner()
     {
         if ($directory = $this->resources_directory()) {
             $id   = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
             $data = $directory->get_resource_owner($id);
         }
 
         $this->rc->output->command('plugin.resource_owner', $data);
         $this->rc->output->send();
     }
 
     /**
      * Deliver event data for a resource's calendar
      */
     function resources_calendar()
     {
         $events = [];
 
         if ($directory = $this->resources_directory()) {
             $id    = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
             $start = $this->input_timestamp('start', rcube_utils::INPUT_GET);
             $end   = $this->input_timestamp('end', rcube_utils::INPUT_GET);
 
             $events = $directory->get_resource_calendar($id, $start, $end);
         }
 
         echo $this->encode($events);
         exit;
     }
 
     /**
      * List email addressed of owned resources
      */
     private function owned_resources_emails()
     {
         $results = [];
         if ($directory = $this->resources_directory()) {
             foreach ($directory->load_resources($_SESSION['kolab_dn'], 5000, 'owner') as $rec) {
                 $results[] = $rec['email'];
             }
         }
         return $results;
     }
 
 
     /****  Event invitation plugin hooks ****/
 
     /**
      * Find an event in user calendars
      */
     protected function find_event($event, &$mode)
     {
         $this->load_driver();
 
         // We search for writeable calendars in personal namespace by default
         $mode   = calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL;
         $result = $this->driver->get_event($event, $mode);
         // ... now check shared folders if not found
         if (!$result) {
             $result = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_SHARED);
             if ($result) {
                 $mode |= calendar_driver::FILTER_SHARED;
             }
         }
 
         return $result;
     }
 
     /**
      * Handler for calendar/itip-status requests
      */
     function event_itip_status()
     {
         $data = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         $this->load_driver();
 
         // find local copy of the referenced event (in personal namespace)
         $existing  = $this->find_event($data, $mode);
         $is_shared = $mode & calendar_driver::FILTER_SHARED;
         $itip      = $this->load_itip();
         $response  = $itip->get_itip_status($data, $existing);
 
         // get a list of writeable calendars to save new events to
         if (
             (!$existing || $is_shared)
             && empty($data['nosave'])
             && ($response['action'] == 'rsvp' || $response['action'] == 'import')
         ) {
             $calendars       = $this->driver->list_calendars($mode);
             $calendar_select = new html_select([
                 'name'       => 'calendar',
                 'id'         => 'itip-saveto',
                 'is_escaped' => true,
                 'class'      => 'form-control custom-select'
             ]);
 
             $calendar_select->add('--', '');
             $numcals = 0;
             foreach ($calendars as $calendar) {
                 if (!empty($calendar['editable'])) {
                     $calendar_select->add($calendar['name'], $calendar['id']);
                     $numcals++;
                 }
             }
             if ($numcals < 1) {
                 $calendar_select = null;
             }
         }
 
         if (!empty($calendar_select)) {
             $default_calendar   = $this->get_default_calendar($calendars);
             $response['select'] = html::span('folder-select', $this->gettext('saveincalendar')
                 . '&nbsp;'
                 . $calendar_select->show($is_shared ? $existing['calendar'] : $default_calendar['id'])
             );
         }
         else if (!empty($data['nosave'])) {
             $response['select'] = html::tag('input', ['type' => 'hidden', 'name' => 'calendar', 'id' => 'itip-saveto', 'value' => '']);
         }
 
         // render small agenda view for the respective day
         if ($data['method'] == 'REQUEST' && !empty($data['date']) && $response['action'] == 'rsvp') {
             $event_start = rcube_utils::anytodatetime($data['date']);
             $day_start   = new Datetime(gmdate('Y-m-d 00:00', $data['date']), $this->lib->timezone);
             $day_end     = new Datetime(gmdate('Y-m-d 23:59', $data['date']), $this->lib->timezone);
 
             // get events on that day from the user's personal calendars
             $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL);
             $events    = $this->driver->load_events($day_start->format('U'), $day_end->format('U'), null, array_keys($calendars));
 
             usort($events, function($a, $b) { return $a['start'] > $b['start'] ? 1 : -1; });
 
             $before = $after = [];
             foreach ($events as $event) {
                 // TODO: skip events with free_busy == 'free' ?
                 if ($event['uid'] == $data['uid']
                     || $event['end'] < $day_start || $event['start'] > $day_end
                     || $event['status'] == 'CANCELLED'
                     || (!empty($event['className']) && strpos($event['className'], 'declined') !== false)
                 ) {
                     continue;
                 }
 
                 if ($event['start'] < $event_start) {
                     $before[] = $this->mail_agenda_event_row($event);
                 }
                 else {
                     $after[] = $this->mail_agenda_event_row($event);
                 }
             }
 
             $response['append'] = [
                 'selector' => '.calendar-agenda-preview',
                 'replacements' => [
                     '%before%' => !empty($before) ? join("\n", array_slice($before,  -3)) : html::div('event-row no-event', $this->gettext('noearlierevents')),
                     '%after%'  => !empty($after)  ? join("\n", array_slice($after, 0, 3)) : html::div('event-row no-event', $this->gettext('nolaterevents')),
                 ],
             ];
         }
 
         $this->rc->output->command('plugin.update_itip_object_status', $response);
     }
 
     /**
      * Handler for calendar/itip-remove requests
      */
     function event_itip_remove()
     {
         $uid      = rcube_utils::get_input_value('uid', rcube_utils::INPUT_POST);
         $instance = rcube_utils::get_input_value('_instance', rcube_utils::INPUT_POST);
         $savemode = rcube_utils::get_input_value('_savemode', rcube_utils::INPUT_POST);
         $listmode = calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL;
         $success  = false;
 
         // search for event if only UID is given
         if ($event = $this->driver->get_event(['uid' => $uid, '_instance' => $instance], $listmode)) {
             $event['_savemode'] = $savemode;
             $success = $this->driver->remove_event($event, true);
         }
 
         if ($success) {
             $this->rc->output->show_message('calendar.successremoval', 'confirmation');
         }
         else {
             $this->rc->output->show_message('calendar.errorsaving', 'error');
         }
     }
 
     /**
      * Handler for URLs that allow an invitee to respond on his invitation mail
      */
     public function itip_attend_response($p)
     {
         $this->setup();
 
         if ($p['action'] == 'attend') {
             $this->ui->init();
 
             $this->rc->output->set_env('task', 'calendar');  // override some env vars
             $this->rc->output->set_env('refresh_interval', 0);
             $this->rc->output->set_pagetitle($this->gettext('calendar'));
 
             $itip  = $this->load_itip();
             $token = rcube_utils::get_input_value('_t', rcube_utils::INPUT_GPC);
 
             // read event info stored under the given token
             if ($invitation = $itip->get_invitation($token)) {
                 $this->token = $token;
                 $this->event = $invitation['event'];
 
                 // show message about cancellation
                 if (!empty($invitation['cancelled'])) {
                     $this->invitestatus = html::div('rsvp-status declined', $itip->gettext('eventcancelled'));
                 }
                 // save submitted RSVP status
                 else if (!empty($_POST['rsvp'])) {
                     $status = null;
                     foreach (['accepted', 'tentative', 'declined'] as $method) {
                         if ($_POST['rsvp'] == $itip->gettext('itip' . $method)) {
                             $status = $method;
                             break;
                         }
                     }
 
                     // send itip reply to organizer
                     $invitation['event']['comment'] = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
                     if ($status && $itip->update_invitation($invitation, $invitation['attendee'], strtoupper($status))) {
                         $this->invitestatus = html::div('rsvp-status ' . strtolower($status), $itip->gettext('youhave'.strtolower($status)));
                     }
                     else {
                         $this->rc->output->command('display_message', $this->gettext('errorsaving'), 'error', -1);
                     }
 
                     // if user is logged in...
                     // FIXME: we should really consider removing this functionality
                     //        it's confusing that it creates/updates an event only for logged-in user
                     //        what if the logged-in user is not the same as the attendee?
                     if ($this->rc->user->ID) {
                         $this->load_driver();
 
                         $invitation = $itip->get_invitation($token);
                         $existing   = $this->driver->get_event($this->event);
 
                         // save the event to his/her default calendar if not yet present
                         if (!$existing && ($calendar = $this->get_default_calendar())) {
                             $invitation['event']['calendar'] = $calendar['id'];
                             if ($this->driver->new_event($invitation['event'])) {
                                 $msg = $this->gettext(['name' => 'importedsuccessfully', 'vars' => ['calendar' => $calendar['name']]]);
                                 $this->rc->output->command('display_message', $msg, 'confirmation');
                             }
                             else {
                                 $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
                             }
                         }
                         else if ($existing
                             && ($this->event['sequence'] >= $existing['sequence']
                                 || $this->event['changed'] >= $existing['changed'])
                             && ($calendar = $this->driver->get_calendar($existing['calendar']))
                         ) {
                             $this->event       = $invitation['event'];
                             $this->event['id'] = $existing['id'];
 
                             unset($this->event['comment']);
 
                             // merge attendees status
                             // e.g. preserve my participant status for regular updates
                             $this->lib->merge_attendees($this->event, $existing, $status);
 
                             // update attachments list
                             $event['deleted_attachments'] = true;
 
                             // show me as free when declined (#1670)
                             if ($status == 'declined') {
                                 $this->event['free_busy'] = 'free';
                             }
 
                             if ($this->driver->edit_event($this->event)) {
                                 $msg = $this->gettext(['name' => 'updatedsuccessfully', 'vars' => ['calendar' => $calendar->get_name()]]);
                                 $this->rc->output->command('display_message', $msg, 'confirmation');
                             }
                             else {
                                 $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
                             }
                         }
                     }
                 }
 
                 $this->register_handler('plugin.event_inviteform', [$this, 'itip_event_inviteform']);
                 $this->register_handler('plugin.event_invitebox', [$this->ui, 'event_invitebox']);
 
                 if (empty($this->invitestatus)) {
                     $this->itip->set_rsvp_actions(['accepted', 'tentative', 'declined']);
                     $this->register_handler('plugin.event_rsvp_buttons', [$this->ui, 'event_rsvp_buttons']);
                 }
 
                 $this->rc->output->set_pagetitle($itip->gettext('itipinvitation') . ' ' . $this->event['title']);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('itipinvalidrequest'), 'error', -1);
             }
 
             $this->rc->output->send('calendar.itipattend');
         }
     }
 
     /**
      *
      */
     public function itip_event_inviteform($attrib)
     {
         $hidden = new html_hiddenfield(['name' => "_t", 'value' => $this->token]);
 
         return html::tag('form', [
                 'action' => $this->rc->url(['task' => 'calendar', 'action' => 'attend']),
                 'method' => 'post',
                 'noclose' => true
             ] + $attrib
         ) . $hidden->show();
     }
 
     /**
      *
      */
     private function mail_agenda_event_row($event, $class = '')
     {
         if (!empty($event['allday'])) {
             $time = $this->gettext('all-day');
         }
         else {
             $start = is_object($event['start']) ? clone $event['start'] : $event['start'];
             $end = is_object($event['end']) ? clone $event['end'] : $event['end'];
 
             $time = $this->rc->format_date($start, $this->rc->config->get('time_format'))
                 . ' - ' . $this->rc->format_date($end, $this->rc->config->get('time_format'));
         }
 
         return html::div(rtrim('event-row ' . ($class ?: $event['className'])),
             html::span('event-date', $time)
             . html::span('event-title', rcube::Q($event['title']))
         );
     }
 
     /**
      *
      */
     public function mail_messages_list($p)
     {
         if (!empty($p['cols']) && in_array('attachment', (array) $p['cols']) && !empty($p['messages'])) {
             foreach ($p['messages'] as $header) {
                 $part = new StdClass;
                 $part->mimetype = $header->ctype;
 
                 if (libcalendaring::part_is_vcalendar($part)) {
                     $header->list_flags['attachmentClass'] = 'ical';
                 }
                 else if (in_array($header->ctype, ['multipart/alternative', 'multipart/mixed'])) {
                     // TODO: fetch bodystructure and search for ical parts. Maybe too expensive?
                     if (!empty($header->structure) && !empty($header->structure->parts)) {
                         foreach ($header->structure->parts as $part) {
                             if (libcalendaring::part_is_vcalendar($part)
                                 && !empty($part->ctype_parameters['method'])
                             ) {
                                 $header->list_flags['attachmentClass'] = 'ical';
                                 break;
                             }
                         }
                     }
                 }
             }
         }
     }
 
     /**
      * Add UI element to copy event invitations or updates to the calendar
      */
     public function mail_messagebody_html($p)
     {
         // load iCalendar functions (if necessary)
         if (!empty($this->lib->ical_parts)) {
             $this->get_ical();
             $this->load_itip();
         }
 
         $html = '';
         $has_events = false;
         $ical_objects = $this->lib->get_mail_ical_objects();
 
         // show a box for every event in the file
         foreach ($ical_objects as $idx => $event) {
             if ($event['_type'] != 'event') {
                 // skip non-event objects (#2928)
                 continue;
             }
 
             $has_events = true;
 
             // get prepared inline UI for this event object
             if ($ical_objects->method) {
                 $append   = '';
                 $date_str = $this->rc->format_date(clone $event['start'], $this->rc->config->get('date_format'), empty($event['start']->_dateonly));
                 $date     = new DateTime($event['start']->format('Y-m-d') . ' 12:00:00', new DateTimeZone('UTC'));
 
                 // prepare a small agenda preview to be filled with actual event data on async request
                 if ($ical_objects->method == 'REQUEST') {
                     $append = html::div('calendar-agenda-preview',
                         html::tag('h3', 'preview-title', $this->gettext('agenda') . ' ' . html::span('date', $date_str))
                         . '%before%' . $this->mail_agenda_event_row($event, 'current') . '%after%'
                     );
                 }
 
                 $html .= html::div('calendar-invitebox invitebox boxinformation',
                     $this->itip->mail_itip_inline_ui(
                         $event,
                         $ical_objects->method,
                         $ical_objects->mime_id . ':' . $idx,
                         'calendar',
                         rcube_utils::anytodatetime($ical_objects->message_date),
                         $this->rc->url(['task' => 'calendar']) . '&view=agendaDay&date=' . $date->format('U')
                     ) . $append
                 );
             }
 
             // limit listing
             if ($idx >= 3) {
                 break;
             }
         }
 
         // prepend event boxes to message body
         if ($html) {
             $this->ui->init();
             $p['content'] = $html . $p['content'];
             $this->rc->output->add_label('calendar.savingdata','calendar.deleteventconfirm','calendar.declinedeleteconfirm');
         }
 
         // add "Save to calendar" button into attachment menu
         if ($has_events) {
             $this->add_button([
                     'id'         => 'attachmentsavecal',
                     'name'       => 'attachmentsavecal',
                     'type'       => 'link',
                     'wrapper'    => 'li',
                     'command'    => 'attachment-save-calendar',
                     'class'      => 'icon calendarlink disabled',
                     'classact'   => 'icon calendarlink active',
                     'innerclass' => 'icon calendar',
                     'label'      => 'calendar.savetocalendar',
                 ],
                 'attachmentmenu'
             );
         }
 
         return $p;
     }
 
     /**
      * Handler for POST request to import an event attached to a mail message
      */
     public function mail_import_itip()
     {
         $itip_sending = $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $status  = rcube_utils::get_input_value('_status', rcube_utils::INPUT_POST);
         $delete  = intval(rcube_utils::get_input_value('_del', rcube_utils::INPUT_POST));
         $noreply = intval(rcube_utils::get_input_value('_noreply', rcube_utils::INPUT_POST));
         $noreply = $noreply || $status == 'needs-action' || $itip_sending === 0;
         $instance = rcube_utils::get_input_value('_instance', rcube_utils::INPUT_POST);
         $savemode = rcube_utils::get_input_value('_savemode', rcube_utils::INPUT_POST);
         $comment  = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
 
         $error_msg = $this->gettext('errorimportingevent');
         $success   = false;
         $deleted   = false;
 
         if ($status == 'delegated') {
             $to = rcube_utils::get_input_value('_to', rcube_utils::INPUT_POST, true);
             $delegates = rcube_mime::decode_address_list($to, 1, false);
             $delegate  = reset($delegates);
 
             if (empty($delegate) || empty($delegate['mailto'])) {
                 $this->rc->output->command('display_message', $this->rc->gettext('libcalendaring.delegateinvalidaddress'), 'error');
                 return;
             }
         }
 
         // successfully parsed events?
         if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
             // forward iTip request to delegatee
             if (!empty($delegate)) {
                 $rsvpme = rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST);
                 $itip   = $this->load_itip();
 
                 $event['comment'] = $comment;
 
                 if ($itip->delegate_to($event, $delegate, !empty($rsvpme))) {
                     $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
 
                 unset($event['comment']);
 
                 // the delegator is set to non-participant, thus save as non-blocking
                 $event['free_busy'] = 'free';
             }
 
             $mode = calendar_driver::FILTER_PERSONAL
                 | calendar_driver::FILTER_SHARED
                 | calendar_driver::FILTER_WRITEABLE;
 
             // find writeable calendar to store event
             $cal_id    = rcube_utils::get_input_value('_folder', rcube_utils::INPUT_POST);
             $dontsave  = $cal_id === '' && $event['_method'] == 'REQUEST';
             $calendars = $this->driver->list_calendars($mode);
             $calendar  = isset($calendars[$cal_id]) ? $calendars[$cal_id] : null;
 
             // select default calendar except user explicitly selected 'none'
             if (!$calendar && !$dontsave) {
                 $calendar = $this->get_default_calendar($calendars);
             }
 
             $metadata = [
                 'uid'       => $event['uid'],
                 '_instance' => isset($event['_instance']) ? $event['_instance'] : null,
                 'changed'   => is_object($event['changed']) ? $event['changed']->format('U') : 0,
                 'sequence'  => intval($event['sequence']),
                 'fallback'  => strtoupper($status),
                 'method'    => $event['_method'],
                 'task'      => 'calendar',
             ];
 
             // update my attendee status according to submitted method
             if (!empty($status)) {
                 $organizer = null;
                 $emails = $this->get_user_emails();
                 foreach ($event['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                         $event['attendees'][$i]['status'] = strtoupper($status);
                         if (!in_array($event['attendees'][$i]['status'], ['NEEDS-ACTION', 'DELEGATED'])) {
                             $event['attendees'][$i]['rsvp'] = false;  // unset RSVP attribute
                         }
 
                         $metadata['attendee'] = $attendee['email'];
                         $metadata['rsvp']     = $attendee['role'] != 'NON-PARTICIPANT';
 
                         $reply_sender   = $attendee['email'];
                         $event_attendee = $attendee;
                     }
                 }
 
                 // add attendee with this user's default identity if not listed
                 if (!$reply_sender) {
                     $sender_identity = $this->rc->user->list_emails(true);
                     $event['attendees'][] = [
                         'name'   => $sender_identity['name'],
                         'email'  => $sender_identity['email'],
                         'role'   => 'OPT-PARTICIPANT',
                         'status' => strtoupper($status),
                     ];
                     $metadata['attendee'] = $sender_identity['email'];
                 }
             }
 
             // save to calendar
             if ($calendar && !empty($calendar['editable'])) {
                 // check for existing event with the same UID
                 $existing = $this->find_event($event, $mode);
 
                 // we'll create a new copy if user decided to change the calendar
                 if ($existing && $cal_id && $calendar && $calendar['id'] != $existing['calendar']) {
                     $existing = null;
                 }
 
                 if ($existing) {
                     $calendar = $calendars[$existing['calendar']];
 
                     // forward savemode for correct updates of recurring events
                     $existing['_savemode'] = $savemode ?: (!empty($event['_savemode']) ? $event['_savemode'] : null);
 
                     // only update attendee status
                     if ($event['_method'] == 'REPLY') {
                         $existing_attendee_index  = -1;
 
                         $event_attendee   = null;
                         $update_attendees = [];
 
                         if ($attendee = $this->itip->find_reply_attendee($event)) {
                             $event_attendee       = $attendee;
                             $update_attendees[]   = $attendee;
                             $metadata['fallback'] = $attendee['status'];
                             $metadata['attendee'] = $attendee['email'];
                             $metadata['rsvp']     = !empty($attendee['rsvp']) || $attendee['role'] != 'NON-PARTICIPANT';
 
                             $existing_attendee_emails = [];
 
                             // Find the attendee to update
                             foreach ($existing['attendees'] as $i => $existing_attendee) {
                                 $existing_attendee_emails[] = $existing_attendee['email'];
                                 if ($this->itip->compare_email($existing_attendee['email'], $attendee['email'])) {
                                     $existing_attendee_index = $i;
                                 }
                             }
 
                             if ($attendee['status'] == 'DELEGATED') {
                                 //Also find and copy the delegatee
                                 $delegatee_email = $attendee['email'];
                                 $delegatees = array_filter($event['attendees'], function($attendee) use ($delegatee_email){ return $attendee['role'] != 'ORGANIZER' && $this->itip->compare_email($attendee['delegated-from'], $delegatee_email); });
 
                                 if ($delegatee = $this->itip->find_attendee_by_email($event['attendees'], 'delegated-from', $attendee['email'])) {
                                     $update_attendees[] = $delegatee;
                                     if (!in_array_nocase($delegatee['email'], $existing_attendee_emails)) {
                                         $existing['attendees'][] = $delegated_attendee;
                                     }
                                 }
                             }
                         }
 
                         // if delegatee has declined, set delegator's RSVP=True
                         if ($event_attendee
                             && $event_attendee['status'] == 'DECLINED'
                             && !empty($event_attendee['delegated-from'])
                         ) {
                             foreach ($existing['attendees'] as $i => $attendee) {
                                 if ($attendee['email'] == $event_attendee['delegated-from']) {
                                     $existing['attendees'][$i]['rsvp'] = true;
                                     break;
                                 }
                             }
                         }
 
                         // found matching attendee entry in both existing and new events
                         if ($existing_attendee_index >= 0 && $event_attendee) {
                             $existing['attendees'][$existing_attendee_index] = $event_attendee;
                             $success = $this->driver->update_attendees($existing, $update_attendees);
                         }
                         // update the entire attendees block
                         else if (
                             ($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed'])
                             && $event_attendee
                         ) {
                             $existing['attendees'][] = $event_attendee;
                             $success = $this->driver->update_attendees($existing, $update_attendees);
                         }
                         else if (!$event_attendee) {
                             $error_msg = $this->gettext('errorunknownattendee');
                         }
                         else {
                             $error_msg = $this->gettext('newerversionexists');
                         }
                     }
                     // delete the event when declined (#1670)
                     else if ($status == 'declined' && $delete) {
                         $deleted = $this->driver->remove_event($existing, true);
                         $success = true;
                     }
                     // import the (newer) event
                     else if ($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed']) {
                         $event['id']       = $existing['id'];
                         $event['calendar'] = $existing['calendar'];
 
                         // merge attendees status
                         // e.g. preserve my participant status for regular updates
                         $this->lib->merge_attendees($event, $existing, $status);
 
                         // set status=CANCELLED on CANCEL messages
                         if ($event['_method'] == 'CANCEL') {
                             $event['status'] = 'CANCELLED';
                         }
 
                         // update attachments list, allow attachments update only on REQUEST (#5342)
                         if ($event['_method'] == 'REQUEST') {
                             $event['deleted_attachments'] = true;
                         }
                         else {
                             unset($event['attachments']);
                         }
 
                         // show me as free when declined (#1670)
                         if ($status == 'declined'
                             || (!empty($event['status']) && $event['status'] == 'CANCELLED')
                             || $event_attendee['role'] == 'NON-PARTICIPANT'
                         ) {
                             $event['free_busy'] = 'free';
                         }
 
                         $success = $this->driver->edit_event($event);
                     }
                     else if (!empty($status)) {
                         $existing['attendees'] = $event['attendees'];
                         if ($status == 'declined' || $event_attendee['role'] == 'NON-PARTICIPANT') {
                             // show me as free when declined (#1670)
                             $existing['free_busy'] = 'free';
                         }
                         $success = $this->driver->edit_event($existing);
                     }
                     else {
                         $error_msg = $this->gettext('newerversionexists');
                     }
                 }
                 else if (!$existing && ($status != 'declined' || $this->rc->config->get('kolab_invitation_calendars'))) {
                     if ($status == 'declined'
                         || $event['status'] == 'CANCELLED'
                         || $event_attendee['role'] == 'NON-PARTICIPANT'
                     ) {
                         $event['free_busy'] = 'free';
                     }
 
                     // if the RSVP reply only refers to a single instance:
                     // store unmodified master event with current instance as exception
                     if (!empty($instance) && !empty($savemode) && $savemode != 'all') {
                         $master = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event');
                         if ($master['recurrence'] && empty($master['_instance'])) {
                             // compute recurring events until this instance's date
                             if ($recurrence_date = rcube_utils::anytodatetime($instance, $master['start']->getTimezone())) {
                                 $recurrence_date->setTime(23,59,59);
 
                                 foreach ($this->driver->get_recurring_events($master, $master['start'], $recurrence_date) as $recurring) {
                                     if ($recurring['_instance'] == $instance) {
                                         // copy attendees block with my partstat to exception
                                         $recurring['attendees'] = $event['attendees'];
                                         $master['recurrence']['EXCEPTIONS'][] = $recurring;
                                         $event = $recurring;  // set reference for iTip reply
                                         break;
                                     }
                                 }
 
                                 $master['calendar'] = $event['calendar'] = $calendar['id'];
                                 $success = $this->driver->new_event($master);
                             }
                             else {
                                 $master = null;
                             }
                         }
                         else {
                             $master = null;
                         }
                     }
 
                     // save to the selected/default calendar
                     if (!$master) {
                         $event['calendar'] = $calendar['id'];
                         $success = $this->driver->new_event($event);
                     }
                 }
                 else if ($status == 'declined') {
                     $error_msg = null;
                 }
             }
             else if ($status == 'declined' || $dontsave) {
                 $error_msg = null;
             }
             else {
                 $error_msg = $this->gettext('nowritecalendarfound');
             }
         }
 
         if ($success) {
             if ($event['_method'] == 'REPLY') {
                 $message = 'attendeupdateesuccess';
             }
             else {
                 $message = $deleted ? 'successremoval' : ($existing ? 'updatedsuccessfully' : 'importedsuccessfully');
             }
 
             $msg = $this->gettext(['name' => $message, 'vars' => ['calendar' => $calendar['name']]]);
             $this->rc->output->command('display_message', $msg, 'confirmation');
         }
 
         if ($success || $dontsave) {
             $metadata['calendar'] = isset($event['calendar']) ? $event['calendar'] : null;
             $metadata['nosave']   = $dontsave;
             $metadata['rsvp']     = !empty($metadata['rsvp']);
 
             $metadata['after_action'] = $this->rc->config->get('calendar_itip_after_action', $this->defaults['calendar_itip_after_action']);
             $this->rc->output->command('plugin.itip_message_processed', $metadata);
             $error_msg = null;
         }
         else if ($error_msg) {
             $this->rc->output->command('display_message', $error_msg, 'error');
         }
 
         // send iTip reply
         if ($event['_method'] == 'REQUEST' && !empty($organizer) && !$noreply
             && !in_array(strtolower($organizer['email']), $emails) && !$error_msg
         ) {
             $event['comment'] = $comment;
             $itip = $this->load_itip();
             $itip->set_sender_email($reply_sender);
 
             if ($itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status)) {
                 $mailto = $organizer['name'] ? $organizer['name'] : $organizer['email'];
                 $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
                 $this->rc->output->command('display_message', $msg, 'confirmation');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
             }
         }
 
         $this->rc->output->send();
     }
 
     /**
      * Handler for calendar/itip-remove requests
      */
     function mail_itip_decline_reply()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
 
         if (($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event'))
             && $event['_method'] == 'REPLY'
         ) {
             $event['comment'] = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
 
             foreach ($event['attendees'] as $_attendee) {
                 if ($_attendee['role'] != 'ORGANIZER') {
                     $attendee = $_attendee;
                     break;
                 }
             }
 
             $itip = $this->load_itip();
 
             if ($itip->send_itip_message($event, 'CANCEL', $attendee, 'itipsubjectcancel', 'itipmailbodycancel')) {
                 $mailto = !empty($attendee['name']) ? $attendee['name'] : $attendee['email'];
                 $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
                 $this->rc->output->command('display_message', $msg, 'confirmation');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
             }
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
         }
     }
 
     /**
      * Handler for calendar/itip-delegate requests
      */
     function mail_itip_delegate()
     {
         // forward request to mail_import_itip() with the right status
         $_POST['_status'] = $_REQUEST['_status'] = 'delegated';
         $this->mail_import_itip();
     }
 
     /**
      * Import the full payload from a mail message attachment
      */
     public function mail_import_attachment()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             $part = $imap->get_message_part($uid, $mime_id);
             // $headers = $imap->get_message_headers($uid);
 
             if ($part) {
                 if (!empty($part->ctype_parameters['charset'])) {
                     $charset = $part->ctype_parameters['charset'];
                 }
                 $events = $this->get_ical()->import($part, $charset);
             }
         }
 
         $success = $existing = 0;
 
         if (!empty($events)) {
             // find writeable calendar to store event
             $cal_id = !empty($_REQUEST['_calendar']) ? rcube_utils::get_input_value('_calendar', rcube_utils::INPUT_POST) : null;
             $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL);
 
             foreach ($events as $event) {
                 // save to calendar
                 $calendar = !empty($calendars[$cal_id]) ? $calendars[$cal_id] : $this->get_default_calendar();
                 if ($calendar && $calendar['editable'] && $event['_type'] == 'event') {
                     $event['calendar'] = $calendar['id'];
 
                     if (!$this->driver->get_event($event['uid'], calendar_driver::FILTER_WRITEABLE)) {
                         $success += (bool)$this->driver->new_event($event);
                     }
                     else {
                         $existing++;
                     }
                 }
             }
         }
 
         if ($success) {
             $msg = $this->gettext(['name' => 'importsuccess', 'vars' => ['nr' => $success]]);
             $this->rc->output->command('display_message', $msg, 'confirmation');
         }
         else if ($existing) {
             $this->rc->output->command('display_message', $this->gettext('importwarningexists'), 'warning');
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
         }
     }
 
     /**
      * Read email message and return contents for a new event based on that message
      */
     public function mail_message2event()
     {
         $this->ui->init();
         $this->ui->addJS();
         $this->ui->init_templates();
         $this->ui->calendar_list([], true); // set env['calendars']
 
         $uid   = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GET);
         $mbox  = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_GET);
         $event = [];
 
         // establish imap connection
         $imap    = $this->rc->get_storage();
         $message = new rcube_message($uid, $mbox);
 
         if ($message->headers) {
             $event['title']       = trim($message->subject);
             $event['description'] = trim($message->first_text_part());
 
             $this->load_driver();
 
             // add a reference to the email message
             if ($msgref = $this->driver->get_message_reference($message->headers, $mbox)) {
                 $event['links'] = [$msgref];
             }
             // copy mail attachments to event
             else if ($message->attachments) {
                 $eventid = 'cal-';
                 if (empty($_SESSION[self::SESSION_KEY]) || $_SESSION[self::SESSION_KEY]['id'] != $eventid) {
                     $_SESSION[self::SESSION_KEY] = [
                         'id'          => $eventid,
                         'attachments' => [],
                     ];
                 }
 
                 foreach ((array) $message->attachments as $part) {
                     $attachment = [
                         'data' => $imap->get_message_part($uid, $part->mime_id, $part),
                         'size' => $part->size,
                         'name' => $part->filename,
                         'mimetype' => $part->mimetype,
                         'group' => $eventid,
                     ];
 
                     $attachment = $this->rc->plugins->exec_hook('attachment_save', $attachment);
 
                     if (!empty($attachment['status']) && !$attachment['abort']) {
                         $id = $attachment['id'];
                         $attachment['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
                         // store new attachment in session
                         unset($attachment['status'], $attachment['abort'], $attachment['data']);
                         $_SESSION[self::SESSION_KEY]['attachments'][$id] = $attachment;
 
                         $attachment['id'] = 'rcmfile' . $attachment['id'];  // add prefix to consider it 'new'
                         $event['attachments'][] = $attachment;
                     }
                 }
             }
 
             $this->rc->output->set_env('event_prop', $event);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
         }
 
         $this->rc->output->send('calendar.dialog');
     }
 
     /**
      * Handler for the 'message_compose' plugin hook. This will check for
      * a compose parameter 'calendar_event' and create an attachment with the
      * referenced event in iCal format
      */
     public function mail_message_compose($args)
     {
         // set the submitted event ID as attachment
         if (!empty($args['param']['calendar_event'])) {
             $this->load_driver();
 
             list($cal, $id) = explode(':', $args['param']['calendar_event'], 2);
 
             if ($event = $this->driver->get_event(['id' => $id, 'calendar' => $cal])) {
                 $filename = asciiwords($event['title']);
                 if (empty($filename)) {
                     $filename = 'event';
                 }
 
                 // save ics to a temp file and register as attachment
                 $tmp_path = tempnam($this->rc->config->get('temp_dir'), 'rcmAttmntCal');
                 $export   = $this->get_ical()->export([$event], '', false, [$this->driver, 'get_attachment_body']);
 
                 file_put_contents($tmp_path, $export);
 
                 $args['attachments'][] = [
                     'path'     => $tmp_path,
                     'name'     => $filename . '.ics',
                     'mimetype' => 'text/calendar',
                     'size'     => filesize($tmp_path),
                 ];
                 $args['param']['subject'] = $event['title'];
             }
         }
 
         return $args;
     }
 
     /**
      * Create a Nextcould Talk room
      */
     public function talk_room_create()
     {
         require_once __DIR__ . '/lib/calendar_nextcloud_api.php';
 
         $api = new calendar_nextcloud_api();
 
         $name = (string) rcube_utils::get_input_value('_name', rcube_utils::INPUT_POST);
 
         $room_url = $api->talk_room_create($name);
 
         if ($room_url) {
             $this->rc->output->command('plugin.talk_room_created', ['url' => $room_url]);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('talkroomcreateerror'), 'error');
         }
     }
 
     /**
      * Update a Nextcould Talk room
      */
     public function talk_room_update($event)
     {
         // If a room is assigned to the event...
         if (
             ($talk_url = $this->rc->config->get('calendar_nextcloud_url'))
             && isset($event['attendees'])
             && !empty($event['location'])
             && strpos($event['location'], unslashify($talk_url) . '/call/') === 0
         ) {
             $participants = [];
             $organizer = null;
 
             // ollect participants' and organizer's email addresses
             foreach ($event['attendees'] as $attendee) {
                 if (!empty($attendee['email'])) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee['email'];
                     }
                     else if ($attendee['cutype'] == 'INDIVIDUAL') {
                         $participants[] = $attendee['email'];
                     }
                 }
             }
 
             // If the event is owned by the current user update the room
             if ($organizer && in_array($organizer, $this->get_user_emails())) {
                 require_once __DIR__ . '/lib/calendar_nextcloud_api.php';
 
                 $api = new calendar_nextcloud_api();
 
                 $api->talk_room_update($event['location'], $participants);
             }
         }
     }
 
     /**
      * Get a list of email addresses of the current user (from login and identities)
      */
     public function get_user_emails()
     {
         return $this->lib->get_user_emails();
     }
 
     /**
      * Build an absolute URL with the given parameters
      */
     public function get_url($param = [])
     {
         $param += ['task' => 'calendar'];
         return $this->rc->url($param, true, true);
     }
 
     public function ical_feed_hash($source)
     {
         return base64_encode($this->rc->user->get_username() . ':' . $source);
     }
 
     /**
      * Handler for user_delete plugin hook
      */
     public function user_delete($args)
     {
          // delete itipinvitations entries related to this user
          $db = $this->rc->get_dbh();
          $table_itipinvitations = $db->table_name('itipinvitations', true);
 
          $db->query("DELETE FROM $table_itipinvitations WHERE `user_id` = ?", $args['user']->ID);
 
         $this->setup();
         $this->load_driver();
 
         return $this->driver->user_delete($args);
     }
 
     /**
      * Find first occurrence of a recurring event excluding start date
      *
      * @param array $event Event data (with 'start' and 'recurrence')
      *
      * @return DateTime Date of the first occurrence
      */
     public function find_first_occurrence($event)
     {
         // Make sure libkolab plugin is loaded in case of Kolab driver
         $this->load_driver();
 
         // Use libkolab to compute recurring events (and libkolab plugin)
-        // Horde-based fallback has many bugs
         if (class_exists('kolabformat') && class_exists('kolabcalendaring') && class_exists('kolab_date_recurrence')) {
             $object = kolab_format::factory('event', 3.0);
             $object->set($event);
 
             $recurrence = new kolab_date_recurrence($object);
         }
         else {
-            // fallback to libcalendaring (Horde-based) recurrence implementation
-            require_once(__DIR__ . '/lib/calendar_recurrence.php');
-            $recurrence = new calendar_recurrence($this, $event);
+            // fallback to libcalendaring recurrence implementation
+            $recurrence = new libcalendaring_recurrence($this->lib, $event);
         }
 
         return $recurrence->first_occurrence();
     }
 
     /**
      * Get date-time input from UI and convert to unix timestamp
      */
     protected function input_timestamp($name, $type)
     {
         $ts = rcube_utils::get_input_value($name, $type);
 
         if ($ts && (!is_numeric($ts) || strpos($ts, 'T'))) {
             $ts = new DateTime($ts, $this->timezone);
             $ts = $ts->getTimestamp();
         }
 
         return $ts;
     }
 
     /**
      * Magic getter for public access to protected members
      */
     public function __get($name)
     {
         switch ($name) {
         case 'ical':
             return $this->get_ical();
 
         case 'itip':
             return $this->load_itip();
 
         case 'driver':
             $this->load_driver();
             return $this->driver;
         }
 
         return null;
     }
 }
diff --git a/plugins/calendar/drivers/calendar_driver.php b/plugins/calendar/drivers/calendar_driver.php
index 082ed210..8bcd6903 100644
--- a/plugins/calendar/drivers/calendar_driver.php
+++ b/plugins/calendar/drivers/calendar_driver.php
@@ -1,863 +1,860 @@
 <?php
 
 /**
  * Driver interface for the Calendar plugin
  *
  * @version @package_version@
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 /**
  * Struct of an internal event object how it is passed from/to the driver classes:
  *
  *  $event = array(
  *            'id' => 'Event ID used for editing',
  *           'uid' => 'Unique identifier of this event',
  *      'calendar' => 'Calendar identifier to add event to or where the event is stored',
  *         'start' => DateTime,  // Event start date/time as DateTime object
  *           'end' => DateTime,  // Event end date/time as DateTime object
  *        'allday' => true|false,  // Boolean flag if this is an all-day event
  *       'changed' => DateTime,    // Last modification date of event
  *         'title' => 'Event title/summary',
  *      'location' => 'Location string',
  *   'description' => 'Event description',
  *           'url' => 'URL to more information',
  *    'recurrence' => array(   // Recurrence definition according to iCalendar (RFC 2445) specification as list of key-value pairs
  *            'FREQ' => 'DAILY|WEEKLY|MONTHLY|YEARLY',
  *        'INTERVAL' => 1...n,
  *           'UNTIL' => DateTime,
  *           'COUNT' => 1..n,   // number of times
  *                      // + more properties (see http://www.kanzaki.com/docs/ical/recur.html)
  *          'EXDATE' => array(),  // list of DateTime objects of exception Dates/Times
  *      'EXCEPTIONS' => array(<event>),  list of event objects which denote exceptions in the recurrence chain
  *    ),
  * 'recurrence_id' => 'ID of the recurrence group',   // usually the ID of the starting event
  *     '_instance' => 'ID of the recurring instance',   // identifies an instance within a recurrence chain
  *    'categories' => 'Event category',
  *     'free_busy' => 'free|busy|outofoffice|tentative',  // Show time as
  *        'status' => 'TENTATIVE|CONFIRMED|CANCELLED',    // event status according to RFC 2445
  *      'priority' => 0-9,     // Event priority (0=undefined, 1=highest, 9=lowest)
  *   'sensitivity' => 'public|private|confidential',   // Event sensitivity
  *        'alarms' => '-15M:DISPLAY',  // DEPRECATED Reminder settings inspired by valarm definition (e.g. display alert 15 minutes before event)
  *       'valarms' => array(           // List of reminders (new format), each represented as a hash array:
  *                  array(
  *                     'trigger' => '-PT90M',     // ISO 8601 period string prefixed with '+' or '-', or DateTime object
  *                      'action' => 'DISPLAY|EMAIL|AUDIO',
  *                    'duration' => 'PT15M',      // ISO 8601 period string
  *                      'repeat' => 0,            // number of repetitions
  *                 'description' => '',        // text to display for DISPLAY actions
  *                     'summary' => '',        // message text for EMAIL actions
  *                   'attendees' => array(),   // list of email addresses to receive alarm messages
  *                  ),
  *   ),
  *   'attachments' => array(   // List of attachments
  *            'name' => 'File name',
  *        'mimetype' => 'Content type',
  *            'size' => 1..n, // in bytes
  *              'id' => 'Attachment identifier'
  *   ),
  * 'deleted_attachments' => array(), // array of attachment identifiers to delete when event is updated
  *     'attendees' => array(   // List of event participants
  *            'name' => 'Participant name',
  *           'email' => 'Participant e-mail address',  // used as identifier
  *            'role' => 'ORGANIZER|REQ-PARTICIPANT|OPT-PARTICIPANT|CHAIR',
  *          'status' => 'NEEDS-ACTION|UNKNOWN|ACCEPTED|TENTATIVE|DECLINED'
  *            'rsvp' => true|false,
  *    ),
  *
  *     '_savemode' => 'all|future|current|new',   // How changes on recurring event should be handled
  *       '_notify' => true|false,  // whether to notify event attendees about changes
  * '_fromcalendar' => 'Calendar identifier where the event was stored before',
  *  );
  */
 
 /**
  * Interface definition for calendar driver classes
  */
 abstract class calendar_driver
 {
     const FILTER_ALL           = 0;
     const FILTER_WRITEABLE     = 1;
     const FILTER_INSERTABLE    = 2;
     const FILTER_ACTIVE        = 4;
     const FILTER_PERSONAL      = 8;
     const FILTER_PRIVATE       = 16;
     const FILTER_CONFIDENTIAL  = 32;
     const FILTER_SHARED        = 64;
     const BIRTHDAY_CALENDAR_ID = '__bdays__';
 
     // features supported by backend
     public $alarms      = false;
     public $attendees   = false;
     public $freebusy    = false;
     public $attachments = false;
     public $undelete    = false;
     public $history     = false;
     public $alarm_types = ['DISPLAY'];
     public $alarm_absolute      = true;
     public $categoriesimmutable = false;
     public $last_error;
 
     protected $default_categories = [
         'Personal' => 'c0c0c0',
         'Work'     => 'ff0000',
         'Family'   => '00ff00',
         'Holiday'  => 'ff6600',
     ];
 
     /**
      * Get a list of available calendars from this source
      *
      * @param int $filter Bitmask defining filter criterias.
      *                    See FILTER_* constants for possible values.
      *
      * @return array List of calendars
      */
     abstract function list_calendars($filter = 0);
 
     /**
      * Create a new calendar assigned to the current user
      *
      * @param array $prop Hash array with calendar properties
      *        name: Calendar name
      *       color: The color of the calendar
      *  showalarms: True if alarms are enabled
      *
      * @return mixed ID of the calendar on success, False on error
      */
     abstract function create_calendar($prop);
 
     /**
      * Update properties of an existing calendar
      *
      * @param array $prop Hash array with calendar properties
      *          id: Calendar Identifier
      *        name: Calendar name
      *       color: The color of the calendar
      *  showalarms: True if alarms are enabled (if supported)
      *
      * @return bool True on success, Fales on failure
      */
     abstract function edit_calendar($prop);
 
     /**
      * Set active/subscribed state of a calendar
      *
      * @param array $prop Hash array with calendar properties
      *          id: Calendar Identifier
      *      active: True if calendar is active, false if not
      *
      * @return bool True on success, Fales on failure
      */
     abstract function subscribe_calendar($prop);
 
     /**
      * Delete the given calendar with all its contents
      *
      * @param array $prop Hash array with calendar properties
      *      id: Calendar Identifier
      *
      * @return bool True on success, Fales on failure
      */
     abstract function delete_calendar($prop);
 
     /**
      * Search for shared or otherwise not listed calendars the user has access
      *
      * @param string $query  Search string
      * @param string $source Section/source to search
      *
      * @return array List of calendars
      */
     abstract function search_calendars($query, $source);
 
     /**
      * Add a single event to the database
      *
      * @param array $event Hash array with event properties (see header of this file)
      *
      * @return mixed New event ID on success, False on error
      */
     abstract function new_event($event);
 
     /**
      * Update an event entry with the given data
      *
      * @param array $event Hash array with event properties (see header of this file)
      *
      * @return bool True on success, False on error
      */
     abstract function edit_event($event);
 
     /**
      * Extended event editing with possible changes to the argument
      *
      * @param array  &$event    Hash array with event properties
      * @param string $status    New participant status
      * @param array  $attendees List of hash arrays with updated attendees
      *
      * @return bool True on success, False on error
      */
     public function edit_rsvp(&$event, $status, $attendees)
     {
         return $this->edit_event($event);
     }
 
     /**
      * Update the participant status for the given attendee
      *
      * @param array &$event    Hash array with event properties
      * @param array $attendees List of hash arrays each represeting an updated attendee
      *
      * @return bool True on success, False on error
      */
     public function update_attendees(&$event, $attendees)
     {
         return $this->edit_event($event);
     }
 
     /**
      * Move a single event
      *
      * @param array $event Hash array with event properties:
      *      id: Event identifier
      *   start: Event start date/time as DateTime object
      *     end: Event end date/time as DateTime object
      *  allday: Boolean flag if this is an all-day event
      *
      * @return bool True on success, False on error
      */
     abstract function move_event($event);
 
     /**
      * Resize a single event
      *
      * @param array $event Hash array with event properties:
      *      id: Event identifier
      *   start: Event start date/time as DateTime object with timezone
      *     end: Event end date/time as DateTime object with timezone
      *
      * @return bool True on success, False on error
      */
     abstract function resize_event($event);
 
     /**
      * Remove a single event from the database
      *
      * @param array $event Hash array with event properties:
      *                     id: Event identifier
      * @param bool  $force Remove event irreversible (mark as deleted otherwise,
      *                     if supported by the backend)
      *
      * @return bool True on success, False on error
      */
     abstract function remove_event($event, $force = true);
 
     /**
      * Restores a single deleted event (if supported)
      *
      * @param array $event Hash array with event properties:
      *                     id: Event identifier
      *
      * @return bool True on success, False on error
      */
     public function restore_event($event)
     {
         return false;
     }
 
     /**
      * Return data of a single event
      *
      * @param mixed $event UID string or hash array with event properties:
      *         id: Event identifier
      *        uid: Event UID
      *  _instance: Instance identifier in combination with uid (optional)
      *   calendar: Calendar identifier (optional)
      * @param int   $scope Bitmask defining the scope to search events in.
      *                     See FILTER_* constants for possible values.
      * @param bool  $full  If true, recurrence exceptions shall be added
      *
      * @return array Event object as hash array
      */
     abstract function get_event($event, $scope = 0, $full = false);
 
     /**
      * Get events from source.
      *
      * @param int    $start      Date range start (unix timestamp)
      * @param int    $end        Date range end (unix timestamp)
      * @param string $query      Search query (optional)
      * @param mixed  $calendars  List of calendar IDs to load events from (either as array or comma-separated string)
      * @param bool   $virtual    Include virtual/recurring events (optional)
      * @param int    $modifiedsince Only list events modified since this time (unix timestamp)
      *
      * @return array A list of event objects (see header of this file for struct of an event)
      */
     abstract function load_events($start, $end, $query = null, $calendars = null, $virtual = 1, $modifiedsince = null);
 
     /**
      * Get number of events in the given calendar
      *
      * @param mixed $calendars List of calendar IDs to count events (either as array or comma-separated string)
      * @param int   $start     Date range start (unix timestamp)
      * @param int   $end       Date range end (unix timestamp)
      *
      * @return array   Hash array with counts grouped by calendar ID
      */
     abstract function count_events($calendars, $start, $end = null);
 
     /**
      * Get a list of pending alarms to be displayed to the user
      *
      * @param int   $time      Current time (unix timestamp)
      * @param mixed $calendars List of calendar IDs to show alarms for (either as array or comma-separated string)
      *
      * @return array A list of alarms, each encoded as hash array:
      *         id: Event identifier
      *        uid: Unique identifier of this event
      *      start: Event start date/time as DateTime object
      *        end: Event end date/time as DateTime object
      *     allday: Boolean flag if this is an all-day event
      *      title: Event title/summary
      *   location: Location string
      */
     abstract function pending_alarms($time, $calendars = null);
 
     /**
      * (User) feedback after showing an alarm notification
      * This should mark the alarm as 'shown' or snooze it for the given amount of time
      *
      * @param string $event_id Event identifier
      * @param int    $snooze   Suspend the alarm for this number of seconds
      */
     abstract function dismiss_alarm($event_id, $snooze = 0);
 
     /**
      * Check the given event object for validity
      *
      * @param array $event Event object as hash array
      *
      * @return boolean True if valid, false if not
      */
     public function validate($event)
     {
         $valid = true;
 
         if (empty($event['start']) || !is_object($event['start']) || !($event['start'] instanceof DateTimeInterface)) {
             $valid = false;
         }
 
         if (empty($event['end']) || !is_object($event['end']) || !($event['end'] instanceof DateTimeInterface)) {
             $valid = false;
         }
 
         return $valid;
     }
 
     /**
      * Get list of event's attachments.
      * Drivers can return list of attachments as event property.
      * If they will do not do this list_attachments() method will be used.
      *
      * @param array $event Hash array with event properties:
      *         id: Event identifier
      *   calendar: Calendar identifier
      *
      * @return array List of attachments, each as hash array:
      *         id: Attachment identifier
      *       name: Attachment name
      *   mimetype: MIME content type of the attachment
      *       size: Attachment size
      */
     public function list_attachments($event) { }
 
     /**
      * Get attachment properties
      *
      * @param string $id    Attachment identifier
      * @param array  $event Hash array with event properties:
      *         id: Event identifier
      *   calendar: Calendar identifier
      *
      * @return array Hash array with attachment properties:
      *         id: Attachment identifier
      *       name: Attachment name
      *   mimetype: MIME content type of the attachment
      *       size: Attachment size
      */
     public function get_attachment($id, $event) { }
 
     /**
      * Get attachment body
      *
      * @param string $id    Attachment identifier
      * @param array  $event Hash array with event properties:
      *         id: Event identifier
      *   calendar: Calendar identifier
      *
      * @return string Attachment body
      */
     public function get_attachment_body($id, $event) { }
 
     /**
      * Build a struct representing the given message reference
      *
      * @param object|string $uri_or_headers rcube_message_header instance holding the message headers
      *                         or an URI from a stored link referencing a mail message.
      * @param string $folder  IMAP folder the message resides in
      *
      * @return array An struct referencing the given IMAP message
      */
     public function get_message_reference($uri_or_headers, $folder = null)
     {
         // to be implemented by the derived classes
         return false;
     }
 
     /**
      * List availabale categories
      * The default implementation reads them from config/user prefs
      */
     public function list_categories()
     {
         $rcmail = rcube::get_instance();
         return $rcmail->config->get('calendar_categories', $this->default_categories);
     }
 
     /**
      * Create a new category
      */
     public function add_category($name, $color) { }
 
     /**
      * Remove the given category
      */
     public function remove_category($name) { }
 
     /**
      * Update/replace a category
      */
     public function replace_category($oldname, $name, $color) { }
 
     /**
      * Fetch free/busy information from a person within the given range
      *
      * @param string $email E-mail address of attendee
      * @param int    $start Requested period start date/time as unix timestamp
      * @param int    $end   Requested period end date/time as unix timestamp
      *
      * @return array List of busy timeslots within the requested range
      */
     public function get_freebusy_list($email, $start, $end)
     {
         return false;
     }
 
     /**
      * Create instances of a recurring event
      *
      * @param array    $event Hash array with event properties
      * @param DateTime $start Start date of the recurrence window
      * @param DateTime $end   End date of the recurrence window
      *
      * @return array List of recurring event instances
      */
     public function get_recurring_events($event, $start, $end = null)
     {
         $events = [];
 
         if (!empty($event['recurrence'])) {
-            // include library class
-            require_once(dirname(__FILE__) . '/../lib/calendar_recurrence.php');
-
-            $rcmail = rcmail::get_instance();
-            $recurrence = new calendar_recurrence($rcmail->plugins->get_plugin('calendar'), $event);
+            $rcmail     = rcmail::get_instance();
+            $recurrence = new libcalendaring_recurrence($rcmail->plugins->get_plugin('calendar')->lib, $event);
             $recurrence_id_format = libcalendaring::recurrence_id_format($event);
 
             // determine a reasonable end date if none given
             if (!$end) {
                 switch ($event['recurrence']['FREQ']) {
                 case 'YEARLY':  $intvl = 'P100Y'; break;
                 case 'MONTHLY': $intvl = 'P20Y';  break;
                 default:        $intvl = 'P10Y';  break;
                 }
 
                 $end = clone $event['start'];
                 $end->add(new DateInterval($intvl));
             }
 
             $i = 0;
             while ($next_event = $recurrence->next_instance()) {
                 // add to output if in range
                 if (($next_event['start'] <= $end && $next_event['end'] >= $start)) {
                     $next_event['_instance'] = $next_event['start']->format($recurrence_id_format);
                     $next_event['id'] = $next_event['uid'] . '-' . $exception['_instance'];
                     $next_event['recurrence_id'] = $event['uid'];
                     $events[] = $next_event;
                 }
                 else if ($next_event['start'] > $end) {  // stop loop if out of range
                     break;
                 }
 
                 // avoid endless recursion loops
                 if (++$i > 1000) {
                     break;
                 }
             }
         }
 
         return $events;
     }
 
     /**
      * Provide a list of revisions for the given event
      *
      * @param array $event Hash array with event properties:
      *         id: Event identifier
      *   calendar: Calendar identifier
      *
      * @return array List of changes, each as a hash array:
      *         rev: Revision number
      *        type: Type of the change (create, update, move, delete)
      *        date: Change date
      *        user: The user who executed the change
      *          ip: Client IP
      * destination: Destination calendar for 'move' type
      */
     public function get_event_changelog($event)
     {
         return false;
     }
 
     /**
      * Get a list of property changes beteen two revisions of an event
      *
      * @param array $event Hash array with event properties:
      *         id: Event identifier
      *   calendar: Calendar identifier
      * @param mixed $rev1 Old Revision
      * @param mixed $rev2 New Revision
      *
      * @return array List of property changes, each as a hash array:
      *    property: Revision number
      *         old: Old property value
      *         new: Updated property value
      */
     public function get_event_diff($event, $rev1, $rev2)
     {
         return false;
     }
 
     /**
      * Return full data of a specific revision of an event
      *
      * @param mixed $event UID string or hash array with event properties:
      *        id: Event identifier
      *  calendar: Calendar identifier
      * @param mixed  $rev Revision number
      *
      * @return array Event object as hash array
      * @see self::get_event()
      */
     public function get_event_revison($event, $rev)
     {
         return false;
     }
 
     /**
      * Command the backend to restore a certain revision of an event.
      * This shall replace the current event with an older version.
      *
      * @param mixed $event UID string or hash array with event properties:
      *        id: Event identifier
      *  calendar: Calendar identifier
      * @param mixed  $rev Revision number
      *
      * @return boolean True on success, False on failure
      */
     public function restore_event_revision($event, $rev)
     {
         return false;
     }
 
     /**
      * Callback function to produce driver-specific calendar create/edit form
      *
      * @param string $action     Request action 'form-edit|form-new'
      * @param array  $calendar   Calendar properties (e.g. id, color)
      * @param array  $formfields Edit form fields
      *
      * @return string HTML content of the form
      */
     public function calendar_form($action, $calendar, $formfields)
     {
         $table = new html_table(['cols' => 2, 'class' => 'propform']);
 
         foreach ($formfields as $col => $colprop) {
             $label = !empty($colprop['label']) ? $colprop['label'] : $rcmail->gettext("$domain.$col");
 
             $table->add('title', html::label($colprop['id'], rcube::Q($label)));
             $table->add(null, $colprop['value']);
         }
 
         return $table->show();
     }
 
     /**
      * Compose a list of birthday events from the contact records in the user's address books.
      *
      * This is a default implementation using Roundcube's address book API.
      * It can be overriden with a more optimized version by the individual drivers.
      *
      * @param int    $start         Event's new start (unix timestamp)
      * @param int    $end           Event's new end (unix timestamp)
      * @param string $search        Search query (optional)
      * @param int    $modifiedsince Only list events modified since this time (unix timestamp)
      *
      * @return array A list of event records
      */
     public function load_birthday_events($start, $end, $search = null, $modifiedsince = null)
     {
         // ignore update requests for simplicity reasons
         if (!empty($modifiedsince)) {
             return [];
         }
 
         // convert to DateTime for comparisons
         $start  = new DateTime('@'.$start);
         $end    = new DateTime('@'.$end);
         // extract the current year
         $year   = $start->format('Y');
         $year2  = $end->format('Y');
 
         $events = [];
         $search = mb_strtolower($search);
         $rcmail = rcmail::get_instance();
         $cache  = $rcmail->get_cache('calendar.birthdays', 'db', 3600);
         $cache->expunge();
 
         $alarm_type   = $rcmail->config->get('calendar_birthdays_alarm_type', '');
         $alarm_offset = $rcmail->config->get('calendar_birthdays_alarm_offset', '-1D');
         $alarms       = $alarm_type ? $alarm_offset . ':' . $alarm_type : null;
 
         // let the user select the address books to consider in prefs
         $selected_sources = $rcmail->config->get('calendar_birthday_adressbooks');
         $sources = $selected_sources ?: array_keys($rcmail->get_address_sources(false, true));
 
         foreach ($sources as $source) {
             $abook = $rcmail->get_address_book($source);
 
             // skip LDAP address books unless selected by the user
             if (!$abook || ($abook instanceof rcube_ldap && empty($selected_sources))) {
                 continue;
             }
 
             // skip collected recipients/senders addressbooks
             if (is_a($abook, 'rcube_addresses')) {
                 continue;
             }
 
             $abook->set_pagesize(10000);
 
             // check for cached results
             $cache_records = [];
             $cached = $cache->get($source);
 
             // iterate over (cached) contacts
             foreach (($cached ?: $abook->search('*', '', 2, true, true, ['birthday'])) as $contact) {
                 $event = self::parse_contact($contact, $source);
 
                 if (empty($event)) {
                     continue;
                 }
 
                 // add stripped record to cache
                 if (empty($cached)) {
                     $cache_records[] = [
                         'ID'       => $contact['ID'],
                         'name'     => $event['_displayname'],
                         'birthday' => $event['start']->format('Y-m-d'),
                     ];
                 }
 
                 // filter by search term (only name is involved here)
                 if (!empty($search) && strpos(mb_strtolower($event['title']), $search) === false) {
                     continue;
                 }
 
                 $bday  = clone $event['start'];
                 $byear = $bday->format('Y');
 
                 // quick-and-dirty recurrence computation: just replace the year
                 $bday->setDate($year, $bday->format('n'), $bday->format('j'));
                 $bday->setTime(12, 0, 0);
                 $this_year = $year;
 
                 // date range reaches over multiple years: use end year if not in range
                 if (($bday > $end || $bday < $start) && $year2 != $year) {
                     $bday->setDate($year2, $bday->format('n'), $bday->format('j'));
                     $this_year = $year2;
                 }
 
                 // birthday is within requested range
                 if ($bday <= $end && $bday >= $start) {
                     unset($event['_displayname']);
                     $event['alarms'] = $alarms;
 
                     // if this is not the first occurence modify event details
                     // but not when this is "all birthdays feed" request
                     if ($year2 - $year < 10 && ($age = ($this_year - $byear))) {
                         $label = ['name' => 'birthdayage', 'vars' => ['age' => $age]];
 
                         $event['description'] = $rcmail->gettext($label, 'calendar');
                         $event['start']       = $bday;
                         $event['end']         = clone $bday;
 
                         unset($event['recurrence']);
                     }
 
                     // add the main instance
                     $events[] = $event;
                 }
             }
 
             // store collected contacts in cache
             if (empty($cached)) {
                 $cache->write($source, $cache_records);
             }
         }
 
         return $events;
     }
 
     /**
      * Get a single birthday calendar event
      */
     public function get_birthday_event($id)
     {
         // decode $id
         list(, $source, $contact_id, $year) = explode(':', rcube_ldap::dn_decode($id));
 
         $rcmail = rcmail::get_instance();
 
         if (strlen($source) && $contact_id && ($abook = $rcmail->get_address_book($source))) {
             if ($contact = $abook->get_record($contact_id, true)) {
                 return self::parse_contact($contact, $source);
             }
         }
     }
 
     /**
      * Parse contact and create an event for its birthday
      *
      * @param array  $contact Contact data
      * @param string $source  Addressbook source ID
      *
      * @return array|null Birthday event data
      */
     public static function parse_contact($contact, $source)
     {
         if (!is_array($contact)) {
             return;
         }
 
         if (!empty($contact['birthday']) && is_array($contact['birthday'])) {
             $contact['birthday'] = reset($contact['birthday']);
         }
 
         if (empty($contact['birthday'])) {
             return;
         }
 
         try {
             $bday = $contact['birthday'];
             if (!$bday instanceof DateTimeInterface) {
                 $bday = new DateTime($bday, new DateTimeZone('UTC'));
             }
             $bday->_dateonly = true;
         }
         catch (Exception $e) {
             rcube::raise_error([
                     'code' => 600,
                     'file' => __FILE__,
                     'line' => __LINE__,
                     'message' => 'BIRTHDAY PARSE ERROR: ' . $e->getMessage()
                 ],
                 true, false
             );
             return;
         }
 
         $rcmail       = rcmail::get_instance();
         $birthyear    = $bday->format('Y');
         $display_name = rcube_addressbook::compose_display_name($contact);
         $label        = ['name' => 'birthdayeventtitle', 'vars' => ['name' => $display_name]];
         $event_title  = $rcmail->gettext($label, 'calendar');
         $uid          = rcube_ldap::dn_encode('bday:' . $source . ':' . $contact['ID'] . ':' . $birthyear);
 
         return [
             'id'           => $uid,
             'uid'          => $uid,
             'calendar'     => self::BIRTHDAY_CALENDAR_ID,
             'title'        => $event_title,
             'description'  => '',
             'allday'       => true,
             'start'        => $bday,
             'end'          => clone $bday,
             'recurrence'   => ['FREQ' => 'YEARLY', 'INTERVAL' => 1],
             'free_busy'    => 'free',
             '_displayname' => $display_name,
         ];
     }
 
     /**
      * Store alarm dismissal for birtual birthay events
      *
      * @param string $event_id Event identifier
      * @param int    $snooze   Suspend the alarm for this number of seconds
      */
     public function dismiss_birthday_alarm($event_id, $snooze = 0)
     {
         $rcmail = rcmail::get_instance();
         $cache  = $rcmail->get_cache('calendar.birthdayalarms', 'db', 86400 * 30);
         $cache->remove($event_id);
 
         // compute new notification time or disable if not snoozed
         $notifyat = $snooze > 0 ? time() + $snooze : null;
         $cache->set($event_id, ['snooze' => $snooze, 'notifyat' => $notifyat]);
 
         return true;
     }
 
     /**
      * Handler for user_delete plugin hook
      *
      * @param array $args Hash array with hook arguments
      *
      * @return array Return arguments for plugin hooks
      */
     public function user_delete($args)
     {
         // TO BE OVERRIDDEN
         return $args;
     }
 }
diff --git a/plugins/calendar/drivers/database/database_driver.php b/plugins/calendar/drivers/database/database_driver.php
index e1ee1490..85b260ca 100644
--- a/plugins/calendar/drivers/database/database_driver.php
+++ b/plugins/calendar/drivers/database/database_driver.php
@@ -1,1531 +1,1528 @@
 <?php
 
 /**
  * Database driver for the Calendar plugin
  *
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 class database_driver extends calendar_driver
 {
     const DB_DATE_FORMAT = 'Y-m-d H:i:s';
 
     public static $scheduling_properties = array('start', 'end', 'allday', 'recurrence', 'location', 'cancelled');
 
     // features this backend supports
     public $alarms      = true;
     public $attendees   = true;
     public $freebusy    = false;
     public $attachments = true;
     public $alarm_types = array('DISPLAY');
 
     private $rc;
     private $cal;
     private $cache           = array();
     private $calendars       = array();
     private $calendar_ids    = '';
     private $free_busy_map   = array('free' => 0, 'busy' => 1, 'out-of-office' => 2, 'outofoffice' => 2, 'tentative' => 3);
     private $sensitivity_map = array('public' => 0, 'private' => 1, 'confidential' => 2);
     private $server_timezone;
 
     private $db_events      = 'events';
     private $db_calendars   = 'calendars';
     private $db_attachments = 'attachments';
 
 
     /**
      * Default constructor
      */
     public function __construct($cal)
     {
         $this->cal             = $cal;
         $this->rc              = $cal->rc;
         $this->server_timezone = new DateTimeZone(date_default_timezone_get());
 
         // read database config
         $db = $this->rc->get_dbh();
         $this->db_events      = $db->table_name($this->rc->config->get('db_table_events', $this->db_events));
         $this->db_calendars   = $db->table_name($this->rc->config->get('db_table_calendars', $this->db_calendars));
         $this->db_attachments = $db->table_name($this->rc->config->get('db_table_attachments', $this->db_attachments));
 
         $this->_read_calendars();
     }
 
     /**
      * Read available calendars for the current user and store them internally
      */
     private function _read_calendars()
     {
         $hidden = array_filter(explode(',', $this->rc->config->get('hidden_calendars', '')));
 
         if (!empty($this->rc->user->ID)) {
             $calendar_ids = array();
             $result = $this->rc->db->query(
                 "SELECT *, `calendar_id` AS id FROM `{$this->db_calendars}`"
                 . " WHERE `user_id` = ?"
                 . " ORDER BY `name`",
                 $this->rc->user->ID
             );
 
             while ($result && ($arr = $this->rc->db->fetch_assoc($result))) {
                 $arr['showalarms'] = intval($arr['showalarms']);
                 $arr['active']     = !in_array($arr['id'], $hidden);
                 $arr['name']       = html::quote($arr['name']);
                 $arr['listname']   = html::quote($arr['name']);
                 $arr['rights']     = 'lrswikxteav';
                 $arr['editable']  = true;
 
                 $this->calendars[$arr['calendar_id']] = $arr;
                 $calendar_ids[] = $this->rc->db->quote($arr['calendar_id']);
             }
 
             $this->calendar_ids = join(',', $calendar_ids);
         }
     }
 
     /**
      * Get a list of available calendars from this source
      *
      * @param integer Bitmask defining filter criterias
      *
      * @return array List of calendars
      */
     public function list_calendars($filter = 0)
     {
         // attempt to create a default calendar for this user
         if (empty($this->calendars)) {
             if ($this->create_calendar(array('name' => 'Default', 'color' => 'cc0000', 'showalarms' => true))) {
                 $this->_read_calendars();
             }
         }
 
         $calendars = $this->calendars;
 
         // filter active calendars
         if ($filter & self::FILTER_ACTIVE) {
             foreach ($calendars as $idx => $cal) {
                 if (!$cal['active']) {
                     unset($calendars[$idx]);
                 }
             }
         }
 
         // 'personal' is unsupported in this driver
 
         // append the virtual birthdays calendar
         if ($this->rc->config->get('calendar_contact_birthdays', false)) {
             $prefs  = $this->rc->config->get('birthday_calendar', array('color' => '87CEFA'));
             $hidden = array_filter(explode(',', $this->rc->config->get('hidden_calendars', '')));
             $id     = self::BIRTHDAY_CALENDAR_ID;
 
             if (empty($active) || !in_array($id, $hidden)) {
                 $calendars[$id] = array(
                     'id'         => $id,
                     'name'       => $this->cal->gettext('birthdays'),
                     'listname'   => $this->cal->gettext('birthdays'),
                     'color'      => $prefs['color'],
                     'showalarms' => (bool)$this->rc->config->get('calendar_birthdays_alarm_type'),
                     'active'     => !in_array($id, $hidden),
                     'group'      => 'x-birthdays',
                     'editable'  => false,
                     'default'    => false,
                     'children'   => false,
                 );
             }
         }
 
         return $calendars;
     }
 
     /**
      * Create a new calendar assigned to the current user
      *
      * @param array Hash array with calendar properties
      *    name: Calendar name
      *   color: The color of the calendar
      * @return mixed ID of the calendar on success, False on error
      */
     public function create_calendar($prop)
     {
         $result = $this->rc->db->query(
             "INSERT INTO `{$this->db_calendars}`"
             . " (`user_id`, `name`, `color`, `showalarms`)"
             . " VALUES (?, ?, ?, ?)",
             $this->rc->user->ID,
             $prop['name'],
             strval($prop['color']),
             !empty($prop['showalarms']) ? 1 : 0
         );
 
         if ($result) {
             return $this->rc->db->insert_id($this->db_calendars);
         }
 
         return false;
     }
 
     /**
      * Update properties of an existing calendar
      *
      * @see calendar_driver::edit_calendar()
      */
     public function edit_calendar($prop)
     {
         // birthday calendar properties are saved in user prefs
         if ($prop['id'] == self::BIRTHDAY_CALENDAR_ID) {
             $prefs['birthday_calendar'] = $this->rc->config->get('birthday_calendar', array('color' => '87CEFA'));
             if (isset($prop['color'])) {
                 $prefs['birthday_calendar']['color'] = $prop['color'];
             }
             if (isset($prop['showalarms'])) {
                 $prefs['calendar_birthdays_alarm_type'] = $prop['showalarms'] ? $this->alarm_types[0] : '';
             }
 
             $this->rc->user->save_prefs($prefs);
             return true;
         }
 
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_calendars}`"
             . " SET `name` = ?, `color` = ?, `showalarms` = ?"
             . " WHERE `calendar_id` = ? AND `user_id` = ?",
             $prop['name'],
             strval($prop['color']),
             $prop['showalarms'] ? 1 : 0,
             $prop['id'],
             $this->rc->user->ID
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Set active/subscribed state of a calendar
      * Save a list of hidden calendars in user prefs
      *
      * @see calendar_driver::subscribe_calendar()
      */
     public function subscribe_calendar($prop)
     {
         $hidden = array_flip(explode(',', $this->rc->config->get('hidden_calendars', '')));
 
         if ($prop['active']) {
             unset($hidden[$prop['id']]);
         }
         else {
             $hidden[$prop['id']] = 1;
         }
 
         return $this->rc->user->save_prefs(array('hidden_calendars' => join(',', array_keys($hidden))));
     }
 
     /**
      * Delete the given calendar with all its contents
      *
      * @see calendar_driver::delete_calendar()
      */
     public function delete_calendar($prop)
     {
         if (!$this->calendars[$prop['id']]) {
             return false;
         }
 
         // events and attachments will be deleted by foreign key cascade
 
         $query = $this->rc->db->query(
             "DELETE FROM `{$this->db_calendars}` WHERE `calendar_id` = ? AND `user_id` = ?",
             $prop['id'],
             $this->rc->user->ID
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Search for shared or otherwise not listed calendars the user has access
      *
      * @param string Search string
      * @param string Section/source to search
      *
      * @return array List of calendars
      */
     public function search_calendars($query, $source)
     {
         // not implemented
         return array();
     }
 
     /**
      * Add a single event to the database
      *
      * @param array Hash array with event properties
      * @see calendar_driver::new_event()
      */
     public function new_event($event)
     {
         if (!$this->validate($event)) {
             return false;
         }
 
         if (!empty($this->calendars)) {
             if ($event['calendar'] && !$this->calendars[$event['calendar']]) {
                 return false;
             }
 
             if (!$event['calendar']) {
                 $event['calendar'] = reset(array_keys($this->calendars));
             }
 
             if ($event_id = $this->_insert_event($event)) {
                 $this->_update_recurring($event);
             }
 
             return $event_id;
         }
 
         return false;
     }
 
     /**
      *
      */
     private function _insert_event(&$event)
     {
         $event = $this->_save_preprocess($event);
         $now   = $this->rc->db->now();
 
         $this->rc->db->query(
             "INSERT INTO `{$this->db_events}`"
             . " (`calendar_id`, `created`, `changed`, `uid`, `recurrence_id`, `instance`,"
                 . " `isexception`, `start`, `end`, `all_day`, `recurrence`, `title`, `description`,"
                 . " `location`, `categories`, `url`, `free_busy`, `priority`, `sensitivity`,"
                 . " `status`, `attendees`, `alarms`, `notifyat`)"
             . " VALUES (?, $now, $now, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)",
             $event['calendar'],
             strval($event['uid']),
             isset($event['recurrence_id']) ? intval($event['recurrence_id']) : 0,
             isset($event['_instance']) ? strval($event['_instance']) : '',
             isset($event['isexception']) ? intval($event['isexception']) : 0,
             $event['start']->format(self::DB_DATE_FORMAT),
             $event['end']->format(self::DB_DATE_FORMAT),
             intval($event['all_day']),
             $event['_recurrence'],
             strval($event['title']),
             isset($event['description']) ? strval($event['description']) : '',
             isset($event['location']) ? strval($event['location']) : '',
             isset($event['categories']) ? join(',', (array) $event['categories']) : '',
             isset($event['url']) ? strval($event['url']) : '',
             intval($event['free_busy']),
             intval($event['priority']),
             intval($event['sensitivity']),
             isset($event['status']) ? strval($event['status']) : '',
             $event['attendees'],
             isset($event['alarms']) ? $event['alarms'] : null,
             $event['notifyat']
         );
 
         $event_id = $this->rc->db->insert_id($this->db_events);
 
         if ($event_id) {
             $event['id'] = $event_id;
 
             // add attachments
             if (!empty($event['attachments'])) {
                 foreach ($event['attachments'] as $attachment) {
                     $this->add_attachment($attachment, $event_id);
                     unset($attachment);
                 }
             }
 
             return $event_id;
         }
 
         return false;
     }
 
     /**
      * Update an event entry with the given data
      *
      * @param array Hash array with event properties
      * @see calendar_driver::edit_event()
      */
     public function edit_event($event)
     {
         if (!empty($this->calendars)) {
             $update_master    = false;
             $update_recurring = true;
 
             $old = $this->get_event($event);
             $ret = true;
 
             // check if update affects scheduling and update attendee status accordingly
             $reschedule = $this->_check_scheduling($event, $old, true);
 
             // increment sequence number
             if (empty($event['sequence']) && $reschedule) {
                 $event['sequence'] = $old['sequence'] + 1;
             }
 
             // modify a recurring event, check submitted savemode to do the right things
             if ($old['recurrence'] || $old['recurrence_id']) {
                 $master = $old['recurrence_id'] ? $this->get_event(array('id' => $old['recurrence_id'])) : $old;
 
                 // keep saved exceptions (not submitted by the client)
                 if (!empty($old['recurrence']['EXDATE'])) {
                     $event['recurrence']['EXDATE'] = $old['recurrence']['EXDATE'];
                 }
 
                 $savemode = isset($event['_savemode']) ? $event['_savemode'] : null;
                 switch ($savemode) {
                 case 'new':
                     $event['uid'] = $this->cal->generate_uid();
                     return $this->new_event($event);
 
                 case 'current':
                     // save as exception
                     $event['isexception'] = 1;
                     $update_recurring     = false;
 
                     // set exception to first instance (= master)
                     if ($event['id'] == $master['id']) {
                         $event += $old;
                         $event['recurrence_id'] = $master['id'];
                         $event['_instance']     = libcalendaring::recurrence_instance_identifier($old, $master['allday']);
                         $event['isexception']   = 1;
                         $event_id = $this->_insert_event($event);
 
                         return $event_id;
                     }
                     break;
 
                 case 'future':
                     if ($master['id'] != $event['id']) {
                         // set until-date on master event, then save this instance as new recurring event
                         $master['recurrence']['UNTIL'] = clone $event['start'];
                         $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
                         unset($master['recurrence']['COUNT']);
                         $update_master = true;
 
                         // if recurrence COUNT, update value to the correct number of future occurences
                         if ($event['recurrence']['COUNT']) {
                             $fromdate = clone $event['start'];
                             $fromdate->setTimezone($this->server_timezone);
 
                             $query = $this->rc->db->query(
                                 "SELECT `event_id` FROM `{$this->db_events}`"
                                 . " WHERE `calendar_id` IN ({$this->calendar_ids})"
                                     . " AND `start` >= ? AND `recurrence_id` = ?",
                                 $fromdate->format(self::DB_DATE_FORMAT),
                                 $master['id']
                             );
 
                             if ($count = $this->rc->db->num_rows($query)) {
                                 $event['recurrence']['COUNT'] = $count;
                             }
                         }
 
                         $update_recurring       = true;
                         $event['recurrence_id'] = 0;
                         $event['isexception']   = 0;
                         $event['_instance']     = '';
                         break;
                     }
                     // else: 'future' == 'all' if modifying the master event
 
                 default:  // 'all' is default
                     $event['id']            = $master['id'];
                     $event['recurrence_id'] = 0;
 
                     // use start date from master but try to be smart on time or duration changes
                     $old_start_date = $old['start']->format('Y-m-d');
                     $old_start_time = $old['allday'] ? '' : $old['start']->format('H:i');
                     $old_duration   = $old['end']->format('U') - $old['start']->format('U');
 
                     $new_start_date = $event['start']->format('Y-m-d');
                     $new_start_time = $event['allday'] ? '' : $event['start']->format('H:i');
                     $new_duration   = $event['end']->format('U') - $event['start']->format('U');
 
                     $diff = $old_start_date != $new_start_date || $old_start_time != $new_start_time || $old_duration != $new_duration;
                     $date_shift = $old['start']->diff($event['start']);
 
                     // shifted or resized
                     if ($diff && ($old_start_date == $new_start_date || $old_duration == $new_duration)) {
                         $event['start'] = $master['start']->add($old['start']->diff($event['start']));
                         $event['end']   = clone $event['start'];
                         $event['end']->add(new DateInterval('PT'.$new_duration.'S'));
                     }
                     // dates did not change, use the ones from master
                     else if ($new_start_date . $new_start_time == $old_start_date . $old_start_time) {
                         $event['start'] = $master['start'];
                         $event['end']   = $master['end'];
                     }
 
                     // adjust recurrence-id when start changed and therefore the entire recurrence chain changes
                     if (is_array($event['recurrence'])
                         && ($old_start_date != $new_start_date || $old_start_time != $new_start_time)
                         && ($exceptions = $this->_load_exceptions($old))
                     ) {
                         $recurrence_id_format = libcalendaring::recurrence_id_format($event);
 
                         foreach ($exceptions as $exception) {
                             $recurrence_id = rcube_utils::anytodatetime($exception['_instance'], $old['start']->getTimezone());
                             if (is_a($recurrence_id, 'DateTime')) {
                                 $recurrence_id->add($date_shift);
                                 $exception['_instance'] = $recurrence_id->format($recurrence_id_format);
                                 $this->_update_event($exception, false);
                             }
                         }
                     }
 
                     $ret = $event['id'];  // return master ID
                     break;
                 }
             }
 
             $success = $this->_update_event($event, $update_recurring);
 
             if ($success && $update_master) {
                 $this->_update_event($master, true);
             }
 
             return $success ? $ret : false;
         }
 
         return false;
     }
 
     /**
      * Extended event editing with possible changes to the argument
      *
      * @param array  Hash array with event properties
      * @param string New participant status
      * @param array  List of hash arrays with updated attendees
      *
      * @return boolean True on success, False on error
      */
     public function edit_rsvp(&$event, $status, $attendees)
     {
         $update_event = $event;
 
         // apply changes to master (and all exceptions)
         if ($event['_savemode'] == 'all' && $event['recurrence_id']) {
             $update_event = $this->get_event(array('id' => $event['recurrence_id']));
             $update_event['_savemode'] = $event['_savemode'];
             calendar::merge_attendee_data($update_event, $attendees);
         }
 
         if ($ret = $this->update_attendees($update_event, $attendees)) {
             // replace $event with effectively updated event (for iTip reply)
             if ($ret !== true && $ret != $update_event['id'] && ($new_event = $this->get_event(array('id' => $ret)))) {
                 $event = $new_event;
             }
             else {
                 $event = $update_event;
             }
         }
 
         return $ret;
     }
 
     /**
      * Update the participant status for the given attendees
      *
      * @see calendar_driver::update_attendees()
      */
     public function update_attendees(&$event, $attendees)
     {
         $success = $this->edit_event($event, true);
 
         // apply attendee updates to recurrence exceptions too
         if ($success && $event['_savemode'] == 'all'
             && !empty($event['recurrence'])
             && empty($event['recurrence_id'])
             && ($exceptions = $this->_load_exceptions($event))
         ) {
             foreach ($exceptions as $exception) {
                 calendar::merge_attendee_data($exception, $attendees);
                 $this->_update_event($exception, false);
             }
         }
 
         return $success;
     }
 
     /**
      * Determine whether the current change affects scheduling and reset attendee status accordingly
      */
     private function _check_scheduling(&$event, $old, $update = true)
     {
         // skip this check when importing iCal/iTip events
         if (isset($event['sequence']) || !empty($event['_method'])) {
             return false;
         }
 
         $reschedule = false;
 
         // iterate through the list of properties considered 'significant' for scheduling
         foreach (self::$scheduling_properties as $prop) {
             $a = isset($old[$prop]) ? $old[$prop] : null;
             $b = isset($event[$prop]) ? $event[$prop] : null;
 
             if (!empty($event['allday']) && ($prop == 'start' || $prop == 'end')
                 && $a instanceof DateTimeInterface
                 && $b instanceof DateTimeInterface
             ) {
                 $a = $a->format('Y-m-d');
                 $b = $b->format('Y-m-d');
             }
 
             if ($prop == 'recurrence' && is_array($a) && is_array($b)) {
                 unset($a['EXCEPTIONS'], $b['EXCEPTIONS']);
                 $a = array_filter($a);
                 $b = array_filter($b);
 
                 // advanced rrule comparison: no rescheduling if series was shortened
                 if (!empty($a['COUNT']) && !empty($b['COUNT']) && $b['COUNT'] < $a['COUNT']) {
                     unset($a['COUNT'], $b['COUNT']);
                 }
                 else if (!empty($a['UNTIL']) && !empty($b['UNTIL']) && $b['UNTIL'] < $a['UNTIL']) {
                     unset($a['UNTIL'], $b['UNTIL']);
                 }
             }
 
             if ($a != $b) {
                 $reschedule = true;
                 break;
             }
         }
 
         // reset all attendee status to needs-action (#4360)
         if ($update && $reschedule && is_array($event['attendees'])) {
             $is_organizer = false;
             $emails       = $this->cal->get_user_emails();
             $attendees    = $event['attendees'];
 
             foreach ($attendees as $i => $attendee) {
                 if ($attendee['role'] == 'ORGANIZER' && $attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                     $is_organizer = true;
                 }
                 else if ($attendee['role'] != 'ORGANIZER'
                     && $attendee['role'] != 'NON-PARTICIPANT'
                     && $attendee['status'] != 'DELEGATED'
                 ) {
                     $attendees[$i]['status'] = 'NEEDS-ACTION';
                     $attendees[$i]['rsvp'] = true;
                 }
             }
 
             // update attendees only if I'm the organizer
             if ($is_organizer || ($event['organizer'] && in_array(strtolower($event['organizer']['email']), $emails))) {
                 $event['attendees'] = $attendees;
             }
         }
 
         return $reschedule;
     }
 
     /**
      * Convert save data to be used in SQL statements
      */
     private function _save_preprocess($event)
     {
         // shift dates to server's timezone (except for all-day events)
         if (!$event['allday']) {
             $event['start'] = clone $event['start'];
             $event['start']->setTimezone($this->server_timezone);
             $event['end'] = clone $event['end'];
             $event['end']->setTimezone($this->server_timezone);
         }
 
         // compose vcalendar-style recurrencue rule from structured data
         $rrule = !empty($event['recurrence']) ? libcalendaring::to_rrule($event['recurrence']) : '';
 
         $sensitivity = isset($event['sensitivity']) ? strtolower($event['sensitivity']) : '';
         $free_busy   = isset($event['free_busy']) ? strtolower($event['free_busy']) : '';
 
         $event['_recurrence'] = rtrim($rrule, ';');
         $event['free_busy']   = isset($this->free_busy_map[$free_busy]) ? $this->free_busy_map[$free_busy] : null;
         $event['sensitivity'] = isset($this->sensitivity_map[$sensitivity]) ? $this->sensitivity_map[$sensitivity] : null;
         $event['all_day']     = !empty($event['allday']) ? 1 : 0;
 
         if ($event['free_busy'] == 'tentative') {
             $event['status'] = 'TENTATIVE';
         }
 
         // compute absolute time to notify the user
         $event['notifyat'] = $this->_get_notification($event);
 
         if (!empty($event['valarms'])) {
             $event['alarms'] = $this->serialize_alarms($event['valarms']);
         }
 
         // process event attendees
         if (!empty($event['attendees'])) {
             $event['attendees'] = json_encode((array)$event['attendees']);
         }
         else {
             $event['attendees'] = '';
         }
 
         return $event;
     }
 
     /**
      * Compute absolute time to notify the user
      */
     private function _get_notification($event)
     {
         if (!empty($event['valarms']) && $event['start'] > new DateTime()) {
             $alarm = libcalendaring::get_next_alarm($event);
 
             if ($alarm['time'] && in_array($alarm['action'], $this->alarm_types)) {
                 return date('Y-m-d H:i:s', $alarm['time']);
             }
         }
     }
 
     /**
      * Save the given event record to database
      *
      * @param array Event data
      * @param boolean True if recurring events instances should be updated, too
      */
     private function _update_event($event, $update_recurring = true)
     {
         $event    = $this->_save_preprocess($event);
         $sql_args = array();
         $set_cols = array('start', 'end', 'all_day', 'recurrence_id', 'isexception', 'sequence',
             'title', 'description', 'location', 'categories', 'url', 'free_busy', 'priority',
             'sensitivity', 'status', 'attendees', 'alarms', 'notifyat'
         );
 
         foreach ($set_cols as $col) {
             if (!empty($event[$col]) && is_a($event[$col], 'DateTime')) {
                 $sql_args[$col] = $event[$col]->format(self::DB_DATE_FORMAT);
             }
             else if (array_key_exists($col, $event)) {
                 $sql_args[$col] = is_array($event[$col]) ? join(',', $event[$col]) : $event[$col];
             }
         }
 
         if (!empty($event['_recurrence'])) {
             $sql_args['recurrence'] = $event['_recurrence'];
         }
 
         if (!empty($event['_instance'])) {
             $sql_args['instance'] = $event['_instance'];
         }
 
         if (!empty($event['_fromcalendar']) && $event['_fromcalendar'] != $event['calendar']) {
             $sql_args['calendar_id'] = $event['calendar'];
         }
 
         $sql_set = '';
         foreach (array_keys($sql_args) as $col) {
             $sql_set .= ", `$col` = ?";
         }
 
         $sql_args = array_values($sql_args);
         $sql_args[] = $event['id'];
 
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}`"
             . " SET `changed` = " . $this->rc->db->now() . $sql_set
             . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $sql_args
         );
 
         $success = $this->rc->db->affected_rows($query);
 
         // add attachments
         if ($success && !empty($event['attachments'])) {
             foreach ($event['attachments'] as $attachment) {
                 $this->add_attachment($attachment, $event['id']);
                 unset($attachment);
             }
         }
 
         // remove attachments
         if ($success && !empty($event['deleted_attachments']) && is_array($event['deleted_attachments'])) {
             foreach ($event['deleted_attachments'] as $attachment) {
                 $this->remove_attachment($attachment, $event['id']);
             }
         }
 
         if ($success) {
             unset($this->cache[$event['id']]);
             if ($update_recurring) {
                 $this->_update_recurring($event);
             }
         }
 
         return $success;
     }
 
     /**
      * Insert "fake" entries for recurring occurences of this event
      */
     private function _update_recurring($event)
     {
         if (empty($this->calendars)) {
             return;
         }
 
         if (!empty($event['recurrence'])) {
             $exdata     = array();
             $exceptions = $this->_load_exceptions($event);
 
             foreach ($exceptions as $exception) {
                 $exdate = substr($exception['_instance'], 0, 8);
                 $exdata[$exdate] = $exception;
             }
         }
 
         // clear existing recurrence copies
         $this->rc->db->query(
             "DELETE FROM `{$this->db_events}`"
             . " WHERE `recurrence_id` = ? AND `isexception` = 0 AND `calendar_id` IN ({$this->calendar_ids})",
             $event['id']
         );
 
         // create new fake entries
         if (!empty($event['recurrence'])) {
-            // include library class
-            require_once($this->cal->home . '/lib/calendar_recurrence.php');
-
-            $recurrence = new calendar_recurrence($this->cal, $event);
+            $recurrence = new libcalendaring_recurrence($this->cal->lib, $event);
             $count = 0;
             $event['allday'] = $event['all_day'];
             $duration = $event['start']->diff($event['end']);
             $recurrence_id_format = libcalendaring::recurrence_id_format($event);
 
             while ($next_start = $recurrence->next_start()) {
                 $instance = $next_start->format($recurrence_id_format);
                 $datestr  = substr($instance, 0, 8);
 
                 // skip exceptions
                 // TODO: merge updated data from master event
                 if (!empty($exdata[$datestr])) {
                     continue;
                 }
 
                 $next_start->setTimezone($this->server_timezone);
                 $next_end = clone $next_start;
                 $next_end->add($duration);
 
                 $notify_at = $this->_get_notification(array(
                         'alarms' => !empty($event['alarms']) ? $event['alarms'] : null,
                         'start'  => $next_start,
                         'end'    => $next_end,
                         'status' => $event['status']
                 ));
 
                 $now   = $this->rc->db->now();
                 $query = $this->rc->db->query(
                     "INSERT INTO `{$this->db_events}`"
                     . " (`calendar_id`, `recurrence_id`, `created`, `changed`, `uid`, `instance`, `start`, `end`,"
                         . " `all_day`, `sequence`, `recurrence`, `title`, `description`, `location`, `categories`,"
                         . " `url`, `free_busy`, `priority`, `sensitivity`, `status`, `alarms`, `attendees`, `notifyat`)"
                     . " SELECT `calendar_id`, ?, $now, $now, `uid`, ?, ?, ?,"
                         . " `all_day`, `sequence`, `recurrence`, `title`, `description`, `location`, `categories`,"
                         . " `url`, `free_busy`, `priority`, `sensitivity`, `status`, `alarms`, `attendees`, ?"
                     . " FROM `{$this->db_events}` WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids})",
                     $event['id'],
                     $instance,
                     $next_start->format(self::DB_DATE_FORMAT),
                     $next_end->format(self::DB_DATE_FORMAT),
                     $notify_at,
                     $event['id']
                 );
 
                 if (!$this->rc->db->affected_rows($query)) {
                     break;
                 }
 
                 // stop adding events for inifinite recurrence after 20 years
                 if (++$count > 999 || (empty($recurrence->recurEnd) && empty($recurrence->recurCount) && $next_start->format('Y') > date('Y') + 20)) {
                     break;
                 }
             }
 
             // remove all exceptions after recurrence end
             if (!empty($next_end) && !empty($exceptions)) {
                 $this->rc->db->query(
                     "DELETE FROM `{$this->db_events}`"
                     . " WHERE `recurrence_id` = ? AND `isexception` = 1 AND `start` > ?"
                         . " AND `calendar_id` IN ({$this->calendar_ids})",
                     $event['id'],
                     $next_end->format(self::DB_DATE_FORMAT)
                 );
             }
         }
     }
 
     /**
      *
      */
     private function _load_exceptions($event, $instance_id = null)
     {
         $sql_add_where = '';
         if (!empty($instance_id)) {
             $sql_add_where = " AND `instance` = ?";
         }
 
         $result = $this->rc->db->query(
             "SELECT * FROM `{$this->db_events}`"
             . " WHERE `recurrence_id` = ? AND `isexception` = 1"
                 . " AND `calendar_id` IN ({$this->calendar_ids})" . $sql_add_where
             . " ORDER BY `instance`, `start`",
             $event['id'],
             $instance_id
         );
 
         $exceptions = array();
         while (($sql_arr = $this->rc->db->fetch_assoc($result)) && $sql_arr['event_id']) {
             $exception = $this->_read_postprocess($sql_arr);
             $instance  = $exception['_instance'] ?: $exception['start']->format($exception['allday'] ? 'Ymd' : 'Ymd\THis');
             $exceptions[$instance] = $exception;
         }
 
         return $exceptions;
     }
 
     /**
      * Move a single event
      *
      * @param array Hash array with event properties
      * @see calendar_driver::move_event()
      */
     public function move_event($event)
     {
         // let edit_event() do all the magic
         return $this->edit_event($event + (array)$this->get_event($event));
     }
 
     /**
      * Resize a single event
      *
      * @param array Hash array with event properties
      * @see calendar_driver::resize_event()
      */
     public function resize_event($event)
     {
         // let edit_event() do all the magic
         return $this->edit_event($event + (array)$this->get_event($event));
     }
 
     /**
      * Remove a single event from the database
      *
      * @param array   Hash array with event properties
      * @param boolean Remove record irreversible (@TODO)
      *
      * @see calendar_driver::remove_event()
      */
     public function remove_event($event, $force = true)
     {
         if (!empty($this->calendars)) {
             $event += (array)$this->get_event($event);
             $master        = $event;
             $update_master = false;
             $savemode      = 'all';
             $ret           = true;
 
             // read master if deleting a recurring event
             if ($event['recurrence'] || $event['recurrence_id']) {
                 $master   = $event['recurrence_id'] ? $this->get_event(array('id' => $event['recurrence_id'])) : $event;
                 $savemode = $event['_savemode'];
             }
 
             switch ($savemode) {
             case 'current':
                 // add exception to master event
                 $master['recurrence']['EXDATE'][] = $event['start'];
                 $update_master = true;
 
                 // just delete this single occurence
                 $query = $this->rc->db->query(
                     "DELETE FROM `{$this->db_events}`"
                     . " WHERE `calendar_id` IN ({$this->calendar_ids}) AND `event_id` = ?",
                     $event['id']
                 );
                 break;
 
             case 'future':
                 if ($master['id'] != $event['id']) {
                     // set until-date on master event
                     $master['recurrence']['UNTIL'] = clone $event['start'];
                     $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
                     unset($master['recurrence']['COUNT']);
                     $update_master = true;
 
                     // delete this and all future instances
                     $fromdate = clone $event['start'];
                     $fromdate->setTimezone($this->server_timezone);
 
                     $query = $this->rc->db->query(
                         "DELETE FROM `{$this->db_events}`"
                         . " WHERE `calendar_id` IN ({$this->calendar_ids}) AND `start` >= ? AND `recurrence_id` = ?",
                         $fromdate->format(self::DB_DATE_FORMAT),
                         $master['id']
                     );
 
                     $ret = $master['id'];
                     break;
                 }
                 // else: future == all if modifying the master event
 
             default:  // 'all' is default
                 $query = $this->rc->db->query(
                     "DELETE FROM `{$this->db_events}`"
                     . " WHERE (`event_id` = ? OR `recurrence_id` = ?) AND `calendar_id` IN ({$this->calendar_ids})",
                     $master['id'],
                     $master['id']
                 );
                 break;
             }
 
             $success = $this->rc->db->affected_rows($query);
 
             if ($success && $update_master) {
                 $this->_update_event($master, true);
             }
 
             return $success ? $ret : false;
         }
 
         return false;
     }
 
     /**
      * Return data of a specific event
      *
      * @param mixed   Hash array with event properties or event UID
      * @param integer Bitmask defining the scope to search events in
      * @param boolean If true, recurrence exceptions shall be added
      *
      * @return array Hash array with event properties
      */
     public function get_event($event, $scope = 0, $full = false)
     {
         $id  = is_array($event) ? (!empty($event['id']) ? $event['id'] : $event['uid']) : $event;
         $cal = is_array($event) && !empty($event['calendar']) ? $event['calendar'] : null;
         $col = is_array($event) && is_numeric($id) ? 'event_id' : 'uid';
 
         if (!empty($this->cache[$id])) {
             return $this->cache[$id];
         }
 
         // get event from the address books birthday calendar
         if ($cal == self::BIRTHDAY_CALENDAR_ID) {
             return $this->get_birthday_event($id);
         }
 
         $where_add = '';
         if (is_array($event) && empty($event['id']) && !empty($event['_instance'])) {
             $where_add = " AND e.instance = " . $this->rc->db->quote($event['_instance']);
         }
 
         if ($scope & self::FILTER_ACTIVE) {
             $calendars = [];
             foreach ($this->calendars as $idx => $cal) {
                 if (!empty($cal['active'])) {
                     $calendars[] = $idx;
                 }
             }
             $cals = join(',', $calendars);
         }
         else {
             $cals = $this->calendar_ids;
         }
 
         $result = $this->rc->db->query(
             "SELECT e.*, (SELECT COUNT(`attachment_id`) FROM `{$this->db_attachments}`"
                 . " WHERE `event_id` = e.event_id OR `event_id` = e.recurrence_id) AS _attachments"
             . " FROM `{$this->db_events}` AS e"
             . " WHERE e.calendar_id IN ($cals) AND e.$col = ?" . $where_add,
             $id
         );
 
         if ($result && ($sql_arr = $this->rc->db->fetch_assoc($result)) && $sql_arr['event_id']) {
             $event = $this->_read_postprocess($sql_arr);
 
             // also load recurrence exceptions
             if (!empty($event['recurrence']) && $full) {
                 $event['recurrence']['EXCEPTIONS'] = array_values($this->_load_exceptions($event));
             }
 
             $this->cache[$id] = $event;
 
             return $this->cache[$id];
         }
 
         return false;
     }
 
     /**
      * Get event data
      *
      * @see calendar_driver::load_events()
      */
     public function load_events($start, $end, $query = null, $calendars = null, $virtual = 1, $modifiedsince = null)
     {
         if (empty($calendars)) {
             $calendars = array_keys($this->calendars);
         }
         else if (!is_array($calendars)) {
             $calendars = explode(',', strval($calendars));
         }
 
         // only allow to select from calendars of this use
         $calendar_ids = array_map(array($this->rc->db, 'quote'), array_intersect($calendars, array_keys($this->calendars)));
 
         // compose (slow) SQL query for searching
         // FIXME: improve searching using a dedicated col and normalized values
         $sql_add = '';
         if ($query) {
             foreach (array('title','location','description','categories','attendees') as $col) {
                 $sql_query[] = $this->rc->db->ilike($col, '%'.$query.'%');
             }
             $sql_add .= " AND (" . join(' OR ', $sql_query) . ")";
         }
 
         if (!$virtual) {
             $sql_add .= " AND e.recurrence_id = 0";
         }
 
         if ($modifiedsince) {
             $sql_add .= " AND e.changed >= " . $this->rc->db->quote(date('Y-m-d H:i:s', $modifiedsince));
         }
 
         $events = array();
         if (!empty($calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT e.*, (SELECT COUNT(`attachment_id`) FROM `{$this->db_attachments}`"
                     . " WHERE `event_id` = e.event_id OR `event_id` = e.recurrence_id) AS _attachments"
                 . " FROM `{$this->db_events}` e"
                 . " WHERE e.calendar_id IN (" . join(',', $calendar_ids) . ")"
                     . " AND e.start <= " . $this->rc->db->fromunixtime($end)
                     . " AND e.end >= " . $this->rc->db->fromunixtime($start)
                     . $sql_add
             );
 
             while ($result && ($sql_arr = $this->rc->db->fetch_assoc($result))) {
                 $event = $this->_read_postprocess($sql_arr);
                 $add   = true;
 
                 if (!empty($event['recurrence']) && !$event['recurrence_id']) {
                     // load recurrence exceptions (i.e. for export)
                     if (!$virtual) {
                         $event['recurrence']['EXCEPTIONS'] = $this->_load_exceptions($event);
                     }
                     // check for exception on first instance
                     else {
                         $instance   = libcalendaring::recurrence_instance_identifier($event);
                         $exceptions = $this->_load_exceptions($event, $instance);
 
                         if ($exceptions && is_array($exceptions[$instance])) {
                             $event = $exceptions[$instance];
                             $add   = false;
                         }
                     }
                 }
 
                 if ($add) {
                     $events[] = $event;
                 }
             }
         }
 
         // add events from the address books birthday calendar
         if (in_array(self::BIRTHDAY_CALENDAR_ID, $calendars) && empty($query)) {
             $events = array_merge($events, $this->load_birthday_events($start, $end, null, $modifiedsince));
         }
 
         return $events;
     }
 
     /**
      * Get number of events in the given calendar
      *
      * @param  mixed   List of calendar IDs to count events (either as array or comma-separated string)
      * @param  integer Date range start (unix timestamp)
      * @param  integer Date range end (unix timestamp)
      *
      * @return array   Hash array with counts grouped by calendar ID
      */
     public function count_events($calendars, $start, $end = null)
     {
         // not implemented
         return array();
     }
 
     /**
      * Convert sql record into a rcube style event object
      */
     private function _read_postprocess($event)
     {
         $free_busy_map   = array_flip($this->free_busy_map);
         $sensitivity_map = array_flip($this->sensitivity_map);
 
         $event['id']            = $event['event_id'];
         $event['start']         = new DateTime($event['start']);
         $event['end']           = new DateTime($event['end']);
         $event['allday']        = intval($event['all_day']);
         $event['created']       = new DateTime($event['created']);
         $event['changed']       = new DateTime($event['changed']);
         $event['free_busy']     = $free_busy_map[$event['free_busy']];
         $event['sensitivity']   = $sensitivity_map[$event['sensitivity']];
         $event['calendar']      = $event['calendar_id'];
         $event['recurrence_id'] = intval($event['recurrence_id']);
         $event['isexception']   = intval($event['isexception']);
 
         // parse recurrence rule
         if ($event['recurrence'] && preg_match_all('/([A-Z]+)=([^;]+);?/', $event['recurrence'], $m, PREG_SET_ORDER)) {
             $event['recurrence'] = array();
             foreach ($m as $rr) {
                 if (is_numeric($rr[2])) {
                     $rr[2] = intval($rr[2]);
                 }
                 else if ($rr[1] == 'UNTIL') {
                     $rr[2] = date_create($rr[2]);
                 }
                 else if ($rr[1] == 'RDATE') {
                     $rr[2] = array_map('date_create', explode(',', $rr[2]));
                 }
                 else if ($rr[1] == 'EXDATE') {
                     $rr[2] = array_map('date_create', explode(',', $rr[2]));
                 }
 
                 $event['recurrence'][$rr[1]] = $rr[2];
             }
         }
 
         if ($event['recurrence_id']) {
             libcalendaring::identify_recurrence_instance($event);
         }
 
         if (strlen($event['instance'])) {
             $event['_instance'] = $event['instance'];
 
             if (empty($event['recurrence_id'])) {
                 $event['recurrence_date'] = rcube_utils::anytodatetime($event['_instance'], $event['start']->getTimezone());
             }
         }
 
         if (!empty($event['_attachments'])) {
             $event['attachments'] = (array)$this->list_attachments($event);
         }
 
         // decode serialized event attendees
         if (strlen($event['attendees'])) {
             $event['attendees'] = $this->unserialize_attendees($event['attendees']);
         }
         else {
             $event['attendees'] = array();
         }
 
         // decode serialized alarms
         if ($event['alarms']) {
             $event['valarms'] = $this->unserialize_alarms($event['alarms']);
         }
 
         unset($event['event_id'], $event['calendar_id'], $event['notifyat'], $event['all_day'], $event['instance'], $event['_attachments']);
 
         return $event;
     }
 
     /**
      * Get a list of pending alarms to be displayed to the user
      *
      * @see calendar_driver::pending_alarms()
      */
     public function pending_alarms($time, $calendars = null)
     {
         if (empty($calendars)) {
             $calendars = array_keys($this->calendars);
         }
         else if (!is_array($calendars)) {
             $calendars = explode(',', (array) $calendars);
         }
 
         // only allow to select from calendars with activated alarms
         $calendar_ids = array();
         foreach ($calendars as $cid) {
             if ($this->calendars[$cid] && $this->calendars[$cid]['showalarms']) {
                 $calendar_ids[] = $cid;
             }
         }
 
         $calendar_ids = array_map(array($this->rc->db, 'quote'), $calendar_ids);
         $alarms       = array();
 
         if (!empty($calendar_ids)) {
             $stime  = $this->rc->db->fromunixtime($time);
             $result = $this->rc->db->query(
                 "SELECT * FROM `{$this->db_events}`"
                 . " WHERE `calendar_id` IN (" . join(',', $calendar_ids) . ")"
                 . " AND `notifyat` <= $stime AND `end` > $stime"
             );
 
             while ($event = $this->rc->db->fetch_assoc($result)) {
                 $alarms[] = $this->_read_postprocess($event);
             }
         }
 
         return $alarms;
     }
 
     /**
      * Feedback after showing/sending an alarm notification
      *
      * @see calendar_driver::dismiss_alarm()
      */
     public function dismiss_alarm($event_id, $snooze = 0)
     {
         // set new notifyat time or unset if not snoozed
         $notify_at = $snooze > 0 ? date(self::DB_DATE_FORMAT, time() + $snooze) : null;
 
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}`"
             . " SET `changed` = " . $this->rc->db->now() . ", `notifyat` = ?"
             . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $notify_at,
             $event_id
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Save an attachment related to the given event
      */
     private function add_attachment($attachment, $event_id)
     {
         if (isset($attachment['data'])) {
             $data = $attachment['data'];
         }
         else if (!empty($attachment['path'])) {
             $data = file_get_contents($attachment['path']);
         }
         else {
             return false;
         }
 
         $query = $this->rc->db->query(
             "INSERT INTO `{$this->db_attachments}`"
             . " (`event_id`, `filename`, `mimetype`, `size`, `data`)"
             . " VALUES (?, ?, ?, ?, ?)",
             $event_id,
             $attachment['name'],
             $attachment['mimetype'],
             strlen($data),
             base64_encode($data)
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Remove a specific attachment from the given event
      */
     private function remove_attachment($attachment_id, $event_id)
     {
         $query = $this->rc->db->query(
             "DELETE FROM `{$this->db_attachments}`"
             . " WHERE `attachment_id` = ? AND `event_id` IN ("
                 . "SELECT `event_id` FROM `{$this->db_events}`"
                 . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))",
             $attachment_id,
             $event_id
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * List attachments of specified event
      */
     public function list_attachments($event)
     {
         $attachments = array();
 
         if (!empty($this->calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT `attachment_id` AS id, `filename` AS name, `mimetype`, `size`"
                 . " FROM `{$this->db_attachments}`"
                 . " WHERE `event_id` IN ("
                     . "SELECT `event_id` FROM `{$this->db_events}`"
                     . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))"
                 . " ORDER BY `filename`",
                 $event['recurrence_id'] ? $event['recurrence_id'] : $event['event_id']
             );
 
             while ($arr = $this->rc->db->fetch_assoc($result)) {
                 $attachments[] = $arr;
             }
         }
 
         return $attachments;
     }
 
     /**
      * Get attachment properties
      */
     public function get_attachment($id, $event)
     {
         if (!empty($this->calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT `attachment_id` AS id, `filename` AS name, `mimetype`, `size` "
                 . " FROM `{$this->db_attachments}`"
                 . " WHERE `attachment_id` = ? AND `event_id` IN ("
                     . "SELECT `event_id` FROM `{$this->db_events}`"
                     . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))",
                 $id,
                 !empty($event['recurrence_id']) ? $event['recurrence_id'] : $event['id']
             );
 
             if ($result && ($arr = $this->rc->db->fetch_assoc($result))) {
                 return $arr;
             }
         }
     }
 
     /**
      * Get attachment body
      */
     public function get_attachment_body($id, $event)
     {
         if (!empty($this->calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT `data` FROM `{$this->db_attachments}`"
                 . " WHERE `attachment_id` = ? AND `event_id` IN ("
                     . "SELECT `event_id` FROM `{$this->db_events}`"
                     . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))",
                 $id,
                 $event['id']
             );
 
             if ($arr = $this->rc->db->fetch_assoc($result)) {
                 return base64_decode($arr['data']);
             }
         }
     }
 
     /**
      * Remove the given category
      */
     public function remove_category($name)
     {
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}` SET `categories` = ''"
             . " WHERE `categories` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $name
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Update/replace a category
      */
     public function replace_category($oldname, $name, $color)
     {
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}` SET `categories` = ?"
             . " WHERE `categories` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $name,
             $oldname
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Helper method to serialize the list of alarms into a string
      */
     private function serialize_alarms($valarms)
     {
         foreach ((array)$valarms as $i => $alarm) {
             if ($alarm['trigger'] instanceof DateTimeInterface) {
                 $valarms[$i]['trigger'] = '@' . $alarm['trigger']->format('c');
             }
         }
 
         return $valarms ? json_encode($valarms) : null;
     }
 
     /**
      * Helper method to decode a serialized list of alarms
      */
     private function unserialize_alarms($alarms)
     {
         // decode json serialized alarms
         if ($alarms && $alarms[0] == '[') {
             $valarms = json_decode($alarms, true);
             foreach ($valarms as $i => $alarm) {
                 if ($alarm['trigger'][0] == '@') {
                     try {
                         $valarms[$i]['trigger'] = new DateTime(substr($alarm['trigger'], 1));
                     }
                     catch (Exception $e) {
                         unset($valarms[$i]);
                     }
                 }
             }
         }
         // convert legacy alarms data
         else if (strlen($alarms)) {
             list($trigger, $action) = explode(':', $alarms, 2);
             if ($trigger = libcalendaring::parse_alarm_value($trigger)) {
                 $valarms = array(array('action' => $action, 'trigger' => $trigger[3] ?: $trigger[0]));
             }
         }
 
         return $valarms;
     }
 
     /**
      * Helper method to decode the attendees list from string
      */
     private function unserialize_attendees($s_attendees)
     {
         $attendees = array();
 
         // decode json serialized string
         if ($s_attendees[0] == '[') {
             $attendees = json_decode($s_attendees, true);
         }
         // decode the old serialization format
         else {
             foreach (explode("\n", $s_attendees) as $line) {
                 $att = array();
                 foreach (rcube_utils::explode_quoted_string(';', $line) as $prop) {
                     list($key, $value) = explode("=", $prop);
                     $att[strtolower($key)] = stripslashes(trim($value, '""'));
                 }
                 $attendees[] = $att;
             }
         }
 
         return $attendees;
     }
 }
diff --git a/plugins/calendar/lib/calendar_recurrence.php b/plugins/calendar/lib/calendar_recurrence.php
deleted file mode 100644
index 4888fe18..00000000
--- a/plugins/calendar/lib/calendar_recurrence.php
+++ /dev/null
@@ -1,89 +0,0 @@
-<?php
-
-require_once realpath(__DIR__ . '/../../libcalendaring/lib/libcalendaring_recurrence.php');
-
-/**
- * Recurrence computation class for the Calendar plugin
- *
- * Uitility class to compute instances of recurring events.
- *
- * @author Thomas Bruederli <bruederli@kolabsys.com>
- *
- * Copyright (C) 2012-2014, Kolab Systems AG <contact@kolabsys.com>
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as
- * published by the Free Software Foundation, either version 3 of the
- * License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-class calendar_recurrence extends libcalendaring_recurrence
-{
-    private $event;
-    private $duration;
-
-    /**
-     * Default constructor
-     *
-     * @param calendar $cal   The calendar plugin instance
-     * @param array    $event The event object to operate on
-     */
-    function __construct($cal, $event)
-    {
-        parent::__construct($cal->lib);
-
-        $this->event = $event;
-
-        if (is_object($event['start']) && is_object($event['end'])) {
-            $this->duration = $event['start']->diff($event['end']);
-        }
-
-        $event['start']->_dateonly = !empty($event['allday']);
-
-        $this->init($event['recurrence'], $event['start']);
-    }
-
-    /**
-     * Alias of libcalendaring_recurrence::next()
-     *
-     * @return mixed DateTime object or False if recurrence ended
-     */
-    public function next_start()
-    {
-        return $this->next();
-    }
-
-    /**
-     * Get the next recurring instance of this event
-     *
-     * @return mixed Array with event properties or False if recurrence ended
-     */
-    public function next_instance()
-    {
-        if ($next_start = $this->next()) {
-            $next = $this->event;
-            $next['start'] = $next_start;
-
-            if ($this->duration) {
-                $next['end'] = clone $next_start;
-                $next['end']->add($this->duration);
-            }
-
-            $next['recurrence_date'] = clone $next_start;
-            $next['_instance'] = libcalendaring::recurrence_instance_identifier($next, $this->event['allday']);
-
-            unset($next['_formatobj']);
-
-            return $next;
-        }
-
-        return false;
-    }
-}
diff --git a/plugins/libcalendaring/lib/Horde_Date.php b/plugins/libcalendaring/lib/Horde_Date.php
deleted file mode 100644
index faa71ffa..00000000
--- a/plugins/libcalendaring/lib/Horde_Date.php
+++ /dev/null
@@ -1,1304 +0,0 @@
-<?php
-
-/**
- * This is a concatenated copy of the following files:
- *   Horde/Date/Utils.php, Horde/Date/Recurrence.php
- * Pull the latest version of these files from the PEAR channel of the Horde
- * project at http://pear.horde.org by installing the Horde_Date package.
- */
-
-
-/**
- * Horde Date wrapper/logic class, including some calculation
- * functions.
- *
- * @category Horde
- * @package  Date
- *
- * @TODO in format():
- *   http://php.net/intldateformatter
- *
- * @TODO on timezones:
- *   http://trac.agavi.org/ticket/1008
- *   http://trac.agavi.org/changeset/3659
- *
- * @TODO on switching to PHP::DateTime:
- *   The only thing ever stored in the database *IS* Unix timestamps. Doing
- *   anything other than that is unmanageable, yet some frameworks use 'server
- *   based' times in their systems, simply because they do not bother with
- *   daylight saving and only 'serve' one timezone!
- *
- *   The second you have to manage 'real' time across timezones then daylight
- *   saving becomes essential, BUT only on the display side! Since the browser
- *   only provides a time offset, this is useless and to be honest should simply
- *   be ignored ( until it is upgraded to provide the correct information ;)
- *   ). So we need a 'display' function that takes a simple numeric epoch, and a
- *   separate timezone id into which the epoch is to be 'converted'. My W3C
- *   mapping works simply because ADOdb then converts that to it's own simple
- *   offset abbreviation - in my case GMT or BST. As long as DateTime passes the
- *   full 64 bit number the date range from 100AD is also preserved ( and
- *   further back if 2 digit years are disabled ). If I want to display the
- *   'real' timezone with this 'time' then I just add it in place of ADOdb's
- *   'timezone'. I am tempted to simply adjust the ADOdb class to take a
- *   timezone in place of the simple GMT switch it currently uses.
- *
- *   The return path is just the reverse and simply needs to take the client
- *   display offset off prior to storage of the UTC epoch. SO we use
- *   DateTimeZone to get an offset value for the clients timezone and simply add
- *   or subtract this from a timezone agnostic display on the client end when
- *   entering new times.
- *
- *
- *   It's not really feasible to store dates in specific timezone, as most
- *   national/local timezones support DST - and that is a pain to support, as
- *   eg.  sorting breaks when some timestamps get repeated. That's why it's
- *   usually better to store datetimes as either UTC datetime or plain unix
- *   timestamp. I usually go with the former - using database datetime type.
- */
-
-/**
- * @category Horde
- * @package  Date
- */
-class Horde_Date
-{
-    const DATE_SUNDAY = 0;
-    const DATE_MONDAY = 1;
-    const DATE_TUESDAY = 2;
-    const DATE_WEDNESDAY = 3;
-    const DATE_THURSDAY = 4;
-    const DATE_FRIDAY = 5;
-    const DATE_SATURDAY = 6;
-
-    const MASK_SUNDAY = 1;
-    const MASK_MONDAY = 2;
-    const MASK_TUESDAY = 4;
-    const MASK_WEDNESDAY = 8;
-    const MASK_THURSDAY = 16;
-    const MASK_FRIDAY = 32;
-    const MASK_SATURDAY = 64;
-    const MASK_WEEKDAYS = 62;
-    const MASK_WEEKEND = 65;
-    const MASK_ALLDAYS = 127;
-
-    const MASK_SECOND = 1;
-    const MASK_MINUTE = 2;
-    const MASK_HOUR = 4;
-    const MASK_DAY = 8;
-    const MASK_MONTH = 16;
-    const MASK_YEAR = 32;
-    const MASK_ALLPARTS = 63;
-
-    const DATE_DEFAULT = 'Y-m-d H:i:s';
-    const DATE_JSON = 'Y-m-d\TH:i:s';
-
-    /**
-     * Year
-     *
-     * @var integer
-     */
-    protected $_year;
-
-    /**
-     * Month
-     *
-     * @var integer
-     */
-    protected $_month;
-
-    /**
-     * Day
-     *
-     * @var integer
-     */
-    protected $_mday;
-
-    /**
-     * Hour
-     *
-     * @var integer
-     */
-    protected $_hour = 0;
-
-    /**
-     * Minute
-     *
-     * @var integer
-     */
-    protected $_min = 0;
-
-    /**
-     * Second
-     *
-     * @var integer
-     */
-    protected $_sec = 0;
-
-    /**
-     * String representation of the date's timezone.
-     *
-     * @var string
-     */
-    protected $_timezone;
-
-    /**
-     * Default format for __toString()
-     *
-     * @var string
-     */
-    protected $_defaultFormat = self::DATE_DEFAULT;
-
-    /**
-     * Default specs that are always supported.
-     * @var string
-     */
-    protected static $_defaultSpecs = '%CdDeHImMnRStTyY';
-
-    /**
-     * Internally supported strftime() specifiers.
-     * @var string
-     */
-    protected static $_supportedSpecs = '';
-
-    /**
-     * Map of required correction masks.
-     *
-     * @see __set()
-     *
-     * @var array
-     */
-    protected static $_corrections = array(
-        'year'  => self::MASK_YEAR,
-        'month' => self::MASK_MONTH,
-        'mday'  => self::MASK_DAY,
-        'hour'  => self::MASK_HOUR,
-        'min'   => self::MASK_MINUTE,
-        'sec'   => self::MASK_SECOND,
-    );
-
-    protected $_formatCache = array();
-
-    /**
-     * Builds a new date object. If $date contains date parts, use them to
-     * initialize the object.
-     *
-     * Recognized formats:
-     * - arrays with keys 'year', 'month', 'mday', 'day'
-     *   'hour', 'min', 'minute', 'sec'
-     * - objects with properties 'year', 'month', 'mday', 'hour', 'min', 'sec'
-     * - yyyy-mm-dd hh:mm:ss
-     * - yyyymmddhhmmss
-     * - yyyymmddThhmmssZ
-     * - yyyymmdd (might conflict with unix timestamps between 31 Oct 1966 and
-     *   03 Mar 1973)
-     * - unix timestamps
-     * - anything parsed by strtotime()/DateTime.
-     *
-     * @throws Horde_Date_Exception
-     */
-    public function __construct($date = null, $timezone = null)
-    {
-        if (!self::$_supportedSpecs) {
-            self::$_supportedSpecs = self::$_defaultSpecs;
-            if (function_exists('nl_langinfo')) {
-                self::$_supportedSpecs .= 'bBpxX';
-            }
-        }
-
-        if (func_num_args() > 2) {
-            // Handle args in order: year month day hour min sec tz
-            $this->_initializeFromArgs(func_get_args());
-            return;
-        }
-
-        $this->_initializeTimezone($timezone);
-
-        if (is_null($date)) {
-            return;
-        }
-
-        if (is_string($date)) {
-            $date = trim($date, '"');
-        }
-
-        if (is_object($date)) {
-            $this->_initializeFromObject($date);
-        } elseif (is_array($date)) {
-            $this->_initializeFromArray($date);
-        } elseif (preg_match('/^(\d{4})-?(\d{2})-?(\d{2})T? ?(\d{2}):?(\d{2}):?(\d{2})(?:\.\d+)?(Z?)$/', $date, $parts)) {
-            $this->_year  = (int)$parts[1];
-            $this->_month = (int)$parts[2];
-            $this->_mday  = (int)$parts[3];
-            $this->_hour  = (int)$parts[4];
-            $this->_min   = (int)$parts[5];
-            $this->_sec   = (int)$parts[6];
-            if ($parts[7]) {
-                $this->_initializeTimezone('UTC');
-            }
-        } elseif (preg_match('/^(\d{4})-?(\d{2})-?(\d{2})$/', $date, $parts) &&
-                  $parts[2] > 0 && $parts[2] <= 12 &&
-                  $parts[3] > 0 && $parts[3] <= 31) {
-            $this->_year  = (int)$parts[1];
-            $this->_month = (int)$parts[2];
-            $this->_mday  = (int)$parts[3];
-            $this->_hour = $this->_min = $this->_sec = 0;
-        } elseif ((string)(int)$date == $date) {
-            // Try as a timestamp.
-            $parts = @getdate($date);
-            if ($parts) {
-                $this->_year  = $parts['year'];
-                $this->_month = $parts['mon'];
-                $this->_mday  = $parts['mday'];
-                $this->_hour  = $parts['hours'];
-                $this->_min   = $parts['minutes'];
-                $this->_sec   = $parts['seconds'];
-            }
-        } else {
-            // Use date_create() so we can catch errors with PHP 5.2. Use
-            // "new DateTime() once we require 5.3.
-            $parsed = date_create($date);
-            if (!$parsed) {
-                throw new Horde_Date_Exception(sprintf(Horde_Date_Translation::t("Failed to parse time string (%s)"), $date));
-            }
-            $parsed->setTimezone(new DateTimeZone(date_default_timezone_get()));
-            $this->_year  = (int)$parsed->format('Y');
-            $this->_month = (int)$parsed->format('m');
-            $this->_mday  = (int)$parsed->format('d');
-            $this->_hour  = (int)$parsed->format('H');
-            $this->_min   = (int)$parsed->format('i');
-            $this->_sec   = (int)$parsed->format('s');
-            $this->_initializeTimezone(date_default_timezone_get());
-        }
-    }
-
-    /**
-     * Returns a simple string representation of the date object
-     *
-     * @return string  This object converted to a string.
-     */
-    public function __toString()
-    {
-        try {
-            return $this->format($this->_defaultFormat);
-        } catch (Exception $e) {
-            return '';
-        }
-    }
-
-    /**
-     * Returns a DateTime object representing this object.
-     *
-     * @return DateTime
-     */
-    public function toDateTime()
-    {
-        $date = new DateTime('now', new DateTimeZone($this->_timezone));
-        $date->setDate($this->_year, $this->_month, $this->_mday);
-        $date->setTime($this->_hour, $this->_min, $this->_sec);
-        return $date;
-    }
-
-    /**
-     * Converts a date in the proleptic Gregorian calendar to the no of days
-     * since 24th November, 4714 B.C.
-     *
-     * Returns the no of days since Monday, 24th November, 4714 B.C. in the
-     * proleptic Gregorian calendar (which is 24th November, -4713 using
-     * 'Astronomical' year numbering, and 1st January, 4713 B.C. in the
-     * proleptic Julian calendar).  This is also the first day of the 'Julian
-     * Period' proposed by Joseph Scaliger in 1583, and the number of days
-     * since this date is known as the 'Julian Day'.  (It is not directly
-     * to do with the Julian calendar, although this is where the name
-     * is derived from.)
-     *
-     * The algorithm is valid for all years (positive and negative), and
-     * also for years preceding 4714 B.C.
-     *
-     * Algorithm is from PEAR::Date_Calc
-     *
-     * @author Monte Ohrt <monte@ispi.net>
-     * @author Pierre-Alain Joye <pajoye@php.net>
-     * @author Daniel Convissor <danielc@php.net>
-     * @author C.A. Woodcock <c01234@netcomuk.co.uk>
-     *
-     * @return integer  The number of days since 24th November, 4714 B.C.
-     */
-    public function toDays()
-    {
-        if (function_exists('GregorianToJD')) {
-            return gregoriantojd($this->_month, $this->_mday, $this->_year);
-        }
-
-        $day = $this->_mday;
-        $month = $this->_month;
-        $year = $this->_year;
-
-        if ($month > 2) {
-            // March = 0, April = 1, ..., December = 9,
-            // January = 10, February = 11
-            $month -= 3;
-        } else {
-            $month += 9;
-            --$year;
-        }
-
-        $hb_negativeyear = $year < 0;
-        $century         = intval($year / 100);
-        $year            = $year % 100;
-
-        if ($hb_negativeyear) {
-            // Subtract 1 because year 0 is a leap year;
-            // And N.B. that we must treat the leap years as occurring
-            // one year earlier than they do, because for the purposes
-            // of calculation, the year starts on 1st March:
-            //
-            return intval((14609700 * $century + ($year == 0 ? 1 : 0)) / 400) +
-                   intval((1461 * $year + 1) / 4) +
-                   intval((153 * $month + 2) / 5) +
-                   $day + 1721118;
-        } else {
-            return intval(146097 * $century / 4) +
-                   intval(1461 * $year / 4) +
-                   intval((153 * $month + 2) / 5) +
-                   $day + 1721119;
-        }
-    }
-
-    /**
-     * Converts number of days since 24th November, 4714 B.C. (in the proleptic
-     * Gregorian calendar, which is year -4713 using 'Astronomical' year
-     * numbering) to Gregorian calendar date.
-     *
-     * Returned date belongs to the proleptic Gregorian calendar, using
-     * 'Astronomical' year numbering.
-     *
-     * The algorithm is valid for all years (positive and negative), and
-     * also for years preceding 4714 B.C. (i.e. for negative 'Julian Days'),
-     * and so the only limitation is platform-dependent (for 32-bit systems
-     * the maximum year would be something like about 1,465,190 A.D.).
-     *
-     * N.B. Monday, 24th November, 4714 B.C. is Julian Day '0'.
-     *
-     * Algorithm is from PEAR::Date_Calc
-     *
-     * @author Monte Ohrt <monte@ispi.net>
-     * @author Pierre-Alain Joye <pajoye@php.net>
-     * @author Daniel Convissor <danielc@php.net>
-     * @author C.A. Woodcock <c01234@netcomuk.co.uk>
-     *
-     * @param int    $days   the number of days since 24th November, 4714 B.C.
-     * @param string $format the string indicating how to format the output
-     *
-     * @return  Horde_Date  A Horde_Date object representing the date.
-     */
-    public static function fromDays($days)
-    {
-        if (function_exists('jdtogregorian')) {
-            list($month, $day, $year) = explode('/', jdtogregorian($days));
-        } else {
-            $days = intval($days);
-
-            $days   -= 1721119;
-            $century = floor((4 * $days - 1) / 146097);
-            $days    = floor(4 * $days - 1 - 146097 * $century);
-            $day     = floor($days / 4);
-
-            $year = floor((4 * $day +  3) / 1461);
-            $day  = floor(4 * $day +  3 - 1461 * $year);
-            $day  = floor(($day +  4) / 4);
-
-            $month = floor((5 * $day - 3) / 153);
-            $day   = floor(5 * $day - 3 - 153 * $month);
-            $day   = floor(($day +  5) /  5);
-
-            $year = $century * 100 + $year;
-            if ($month < 10) {
-                $month +=3;
-            } else {
-                $month -=9;
-                ++$year;
-            }
-        }
-
-        return new Horde_Date($year, $month, $day);
-    }
-
-    /**
-     * Getter for the date and time properties.
-     *
-     * @param string $name  One of 'year', 'month', 'mday', 'hour', 'min' or
-     *                      'sec'.
-     *
-     * @return integer  The property value, or null if not set.
-     */
-    public function __get($name)
-    {
-        if ($name == 'day') {
-            $name = 'mday';
-        }
-
-        return $this->{'_' . $name};
-    }
-
-    /**
-     * Setter for the date and time properties.
-     *
-     * @param string $name    One of 'year', 'month', 'mday', 'hour', 'min' or
-     *                        'sec'.
-     * @param integer $value  The property value.
-     */
-    public function __set($name, $value)
-    {
-        if ($name == 'timezone') {
-            $this->_initializeTimezone($value);
-            return;
-        }
-        if ($name == 'day') {
-            $name = 'mday';
-        }
-
-        if ($name != 'year' && $name != 'month' && $name != 'mday' &&
-            $name != 'hour' && $name != 'min' && $name != 'sec') {
-            throw new InvalidArgumentException('Undefined property ' . $name);
-        }
-
-        $down = $value < $this->{'_' . $name};
-        $this->{'_' . $name} = $value;
-        $this->_correct(self::$_corrections[$name], $down);
-        $this->_formatCache = array();
-    }
-
-    /**
-     * Returns whether a date or time property exists.
-     *
-     * @param string $name  One of 'year', 'month', 'mday', 'hour', 'min' or
-     *                      'sec'.
-     *
-     * @return boolen  True if the property exists and is set.
-     */
-    public function __isset($name)
-    {
-        if ($name == 'day') {
-            $name = 'mday';
-        }
-        return ($name == 'year' || $name == 'month' || $name == 'mday' ||
-                $name == 'hour' || $name == 'min' || $name == 'sec') &&
-            isset($this->{'_' . $name});
-    }
-
-    /**
-     * Adds a number of seconds or units to this date, returning a new Date
-     * object.
-     */
-    public function add($factor)
-    {
-        $d = clone($this);
-        if (is_array($factor) || is_object($factor)) {
-            foreach ($factor as $property => $value) {
-                $d->$property += $value;
-            }
-        } else {
-            $d->sec += $factor;
-        }
-
-        return $d;
-    }
-
-    /**
-     * Subtracts a number of seconds or units from this date, returning a new
-     * Horde_Date object.
-     */
-    public function sub($factor)
-    {
-        if (is_array($factor)) {
-            foreach ($factor as &$value) {
-                $value *= -1;
-            }
-        } else {
-            $factor *= -1;
-        }
-
-        return $this->add($factor);
-    }
-
-    /**
-     * Converts this object to a different timezone.
-     *
-     * @param string $timezone  The new timezone.
-     *
-     * @return Horde_Date  This object.
-     */
-    public function setTimezone($timezone)
-    {
-        $date = $this->toDateTime();
-        $date->setTimezone(new DateTimeZone($timezone));
-        $this->_timezone = $timezone;
-        $this->_year     = (int)$date->format('Y');
-        $this->_month    = (int)$date->format('m');
-        $this->_mday     = (int)$date->format('d');
-        $this->_hour     = (int)$date->format('H');
-        $this->_min      = (int)$date->format('i');
-        $this->_sec      = (int)$date->format('s');
-        $this->_formatCache = array();
-        return $this;
-    }
-
-    /**
-     * Sets the default date format used in __toString()
-     *
-     * @param string $format
-     */
-    public function setDefaultFormat($format)
-    {
-        $this->_defaultFormat = $format;
-    }
-
-    /**
-     * Returns the day of the week (0 = Sunday, 6 = Saturday) of this date.
-     *
-     * @return integer  The day of the week.
-     */
-    public function dayOfWeek()
-    {
-        if ($this->_month > 2) {
-            $month = $this->_month - 2;
-            $year = $this->_year;
-        } else {
-            $month = $this->_month + 10;
-            $year = $this->_year - 1;
-        }
-
-        $day = (floor((13 * $month - 1) / 5) +
-                $this->_mday + ($year % 100) +
-                floor(($year % 100) / 4) +
-                floor(($year / 100) / 4) - 2 *
-                floor($year / 100) + 77);
-
-        return (int)($day - 7 * floor($day / 7));
-    }
-
-    /**
-     * Returns the day number of the year (1 to 365/366).
-     *
-     * @return integer  The day of the year.
-     */
-    public function dayOfYear()
-    {
-        return $this->format('z') + 1;
-    }
-
-    /**
-     * Returns the week of the month.
-     *
-     * @return integer  The week number.
-     */
-    public function weekOfMonth()
-    {
-        return ceil($this->_mday / 7);
-    }
-
-    /**
-     * Returns the week of the year, first Monday is first day of first week.
-     *
-     * @return integer  The week number.
-     */
-    public function weekOfYear()
-    {
-        return $this->format('W');
-    }
-
-    /**
-     * Returns the number of weeks in the given year (52 or 53).
-     *
-     * @param integer $year  The year to count the number of weeks in.
-     *
-     * @return integer $numWeeks   The number of weeks in $year.
-     */
-    public static function weeksInYear($year)
-    {
-        // Find the last Thursday of the year.
-        $date = new Horde_Date($year . '-12-31');
-        while ($date->dayOfWeek() != self::DATE_THURSDAY) {
-            --$date->mday;
-        }
-        return $date->weekOfYear();
-    }
-
-    /**
-     * Sets the date of this object to the $nth weekday of $weekday.
-     *
-     * @param integer $weekday  The day of the week (0 = Sunday, etc).
-     * @param integer $nth      The $nth $weekday to set to (defaults to 1).
-     */
-    public function setNthWeekday($weekday, $nth = 1)
-    {
-        if ($weekday < self::DATE_SUNDAY || $weekday > self::DATE_SATURDAY) {
-            return;
-        }
-
-        if ($nth < 0) {  // last $weekday of month
-            $this->_mday = $lastday = Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
-            $last = $this->dayOfWeek();
-            $this->_mday += ($weekday - $last);
-            if ($this->_mday > $lastday)
-                $this->_mday -= 7;
-        }
-        else {
-            $this->_mday = 1;
-            $first = $this->dayOfWeek();
-            if ($weekday < $first) {
-                $this->_mday = 8 + $weekday - $first;
-            } else {
-                $this->_mday = $weekday - $first + 1;
-            }
-            $diff = 7 * $nth - 7;
-            $this->_mday += $diff;
-            $this->_correct(self::MASK_DAY, $diff < 0);
-        }
-    }
-
-    /**
-     * Is the date currently represented by this object a valid date?
-     *
-     * @return boolean  Validity, counting leap years, etc.
-     */
-    public function isValid()
-    {
-        return ($this->_year >= 0 && $this->_year <= 9999);
-    }
-
-    /**
-     * Compares this date to another date object to see which one is
-     * greater (later). Assumes that the dates are in the same
-     * timezone.
-     *
-     * @param mixed $other  The date to compare to.
-     *
-     * @return integer  ==  0 if they are on the same date
-     *                  >=  1 if $this is greater (later)
-     *                  <= -1 if $other is greater (later)
-     */
-    public function compareDate($other)
-    {
-        if (!($other instanceof Horde_Date)) {
-            $other = new Horde_Date($other);
-        }
-
-        if ($this->_year != $other->year) {
-            return $this->_year - $other->year;
-        }
-        if ($this->_month != $other->month) {
-            return $this->_month - $other->month;
-        }
-
-        return $this->_mday - $other->mday;
-    }
-
-    /**
-     * Returns whether this date is after the other.
-     *
-     * @param mixed $other  The date to compare to.
-     *
-     * @return boolean  True if this date is after the other.
-     */
-    public function after($other)
-    {
-        return $this->compareDate($other) > 0;
-    }
-
-    /**
-     * Returns whether this date is before the other.
-     *
-     * @param mixed $other  The date to compare to.
-     *
-     * @return boolean  True if this date is before the other.
-     */
-    public function before($other)
-    {
-        return $this->compareDate($other) < 0;
-    }
-
-    /**
-     * Returns whether this date is the same like the other.
-     *
-     * @param mixed $other  The date to compare to.
-     *
-     * @return boolean  True if this date is the same like the other.
-     */
-    public function equals($other)
-    {
-        return $this->compareDate($other) == 0;
-    }
-
-    /**
-     * Compares this to another date object by time, to see which one
-     * is greater (later). Assumes that the dates are in the same
-     * timezone.
-     *
-     * @param mixed $other  The date to compare to.
-     *
-     * @return integer  ==  0 if they are at the same time
-     *                  >=  1 if $this is greater (later)
-     *                  <= -1 if $other is greater (later)
-     */
-    public function compareTime($other)
-    {
-        if (!($other instanceof Horde_Date)) {
-            $other = new Horde_Date($other);
-        }
-
-        if ($this->_hour != $other->hour) {
-            return $this->_hour - $other->hour;
-        }
-        if ($this->_min != $other->min) {
-            return $this->_min - $other->min;
-        }
-
-        return $this->_sec - $other->sec;
-    }
-
-    /**
-     * Compares this to another date object, including times, to see
-     * which one is greater (later). Assumes that the dates are in the
-     * same timezone.
-     *
-     * @param mixed $other  The date to compare to.
-     *
-     * @return integer  ==  0 if they are equal
-     *                  >=  1 if $this is greater (later)
-     *                  <= -1 if $other is greater (later)
-     */
-    public function compareDateTime($other)
-    {
-        if (!($other instanceof Horde_Date)) {
-            $other = new Horde_Date($other);
-        }
-
-        if ($diff = $this->compareDate($other)) {
-            return $diff;
-        }
-
-        return $this->compareTime($other);
-    }
-
-    /**
-     * Returns number of days between this date and another.
-     *
-     * @param Horde_Date $other  The other day to diff with.
-     *
-     * @return integer  The absolute number of days between the two dates.
-     */
-    public function diff($other)
-    {
-        return abs($this->toDays() - $other->toDays());
-    }
-
-    /**
-     * Returns the time offset for local time zone.
-     *
-     * @param boolean $colon  Place a colon between hours and minutes?
-     *
-     * @return string  Timezone offset as a string in the format +HH:MM.
-     */
-    public function tzOffset($colon = true)
-    {
-        return $colon ? $this->format('P') : $this->format('O');
-    }
-
-    /**
-     * Returns the unix timestamp representation of this date.
-     *
-     * @return integer  A unix timestamp.
-     */
-    public function timestamp()
-    {
-        if ($this->_year >= 1970 && $this->_year < 2038) {
-            return mktime($this->_hour, $this->_min, $this->_sec,
-                          $this->_month, $this->_mday, $this->_year);
-        }
-        return $this->format('U');
-    }
-
-    /**
-     * Returns the unix timestamp representation of this date, 12:00am.
-     *
-     * @return integer  A unix timestamp.
-     */
-    public function datestamp()
-    {
-        if ($this->_year >= 1970 && $this->_year < 2038) {
-            return mktime(0, 0, 0, $this->_month, $this->_mday, $this->_year);
-        }
-        $date = new DateTime($this->format('Y-m-d'));
-        return $date->format('U');
-    }
-
-    /**
-     * Formats date and time to be passed around as a short url parameter.
-     *
-     * @return string  Date and time.
-     */
-    public function dateString()
-    {
-        return sprintf('%04d%02d%02d', $this->_year, $this->_month, $this->_mday);
-    }
-
-    /**
-     * Formats date and time to the ISO format used by JSON.
-     *
-     * @return string  Date and time.
-     */
-    public function toJson()
-    {
-        return $this->format(self::DATE_JSON);
-    }
-
-    /**
-     * Formats date and time to the RFC 2445 iCalendar DATE-TIME format.
-     *
-     * @param boolean $floating  Whether to return a floating date-time
-     *                           (without time zone information).
-     *
-     * @return string  Date and time.
-     */
-    public function toiCalendar($floating = false)
-    {
-        if ($floating) {
-            return $this->format('Ymd\THis');
-        }
-        $dateTime = $this->toDateTime();
-        $dateTime->setTimezone(new DateTimeZone('UTC'));
-        return $dateTime->format('Ymd\THis\Z');
-    }
-
-    /**
-     * Formats time using the specifiers available in date() or in the DateTime
-     * class' format() method.
-     *
-     * To format in languages other than English, use strftime() instead.
-     *
-     * @param string $format
-     *
-     * @return string  Formatted time.
-     */
-    public function format($format)
-    {
-        if (!isset($this->_formatCache[$format])) {
-            $this->_formatCache[$format] = $this->toDateTime()->format($format);
-        }
-        return $this->_formatCache[$format];
-    }
-
-    /**
-     * Formats date and time using strftime() format.
-     *
-     * @return string  strftime() formatted date and time.
-     */
-    public function strftime($format)
-    {
-        if (preg_match('/%[^' . self::$_supportedSpecs . ']/', $format)) {
-            return strftime($format, $this->timestamp());
-        } else {
-            return $this->_strftime($format);
-        }
-    }
-
-    /**
-     * Formats date and time using a limited set of the strftime() format.
-     *
-     * @return string  strftime() formatted date and time.
-     */
-    protected function _strftime($format)
-    {
-        return preg_replace(
-            array('/%b/e',
-                  '/%B/e',
-                  '/%C/e',
-                  '/%d/e',
-                  '/%D/e',
-                  '/%e/e',
-                  '/%H/e',
-                  '/%I/e',
-                  '/%m/e',
-                  '/%M/e',
-                  '/%n/',
-                  '/%p/e',
-                  '/%R/e',
-                  '/%S/e',
-                  '/%t/',
-                  '/%T/e',
-                  '/%x/e',
-                  '/%X/e',
-                  '/%y/e',
-                  '/%Y/',
-                  '/%%/'),
-            array('$this->_strftime(Horde_Nls::getLangInfo(constant(\'ABMON_\' . (int)$this->_month)))',
-                  '$this->_strftime(Horde_Nls::getLangInfo(constant(\'MON_\' . (int)$this->_month)))',
-                  '(int)($this->_year / 100)',
-                  'sprintf(\'%02d\', $this->_mday)',
-                  '$this->_strftime(\'%m/%d/%y\')',
-                  'sprintf(\'%2d\', $this->_mday)',
-                  'sprintf(\'%02d\', $this->_hour)',
-                  'sprintf(\'%02d\', $this->_hour == 0 ? 12 : ($this->_hour > 12 ? $this->_hour - 12 : $this->_hour))',
-                  'sprintf(\'%02d\', $this->_month)',
-                  'sprintf(\'%02d\', $this->_min)',
-                  "\n",
-                  '$this->_strftime(Horde_Nls::getLangInfo($this->_hour < 12 ? AM_STR : PM_STR))',
-                  '$this->_strftime(\'%H:%M\')',
-                  'sprintf(\'%02d\', $this->_sec)',
-                  "\t",
-                  '$this->_strftime(\'%H:%M:%S\')',
-                  '$this->_strftime(Horde_Nls::getLangInfo(D_FMT))',
-                  '$this->_strftime(Horde_Nls::getLangInfo(T_FMT))',
-                  'substr(sprintf(\'%04d\', $this->_year), -2)',
-                  (int)$this->_year,
-                  '%'),
-            $format);
-    }
-
-    /**
-     * Corrects any over- or underflows in any of the date's members.
-     *
-     * @param integer $mask  We may not want to correct some overflows.
-     * @param integer $down  Whether to correct the date up or down.
-     */
-    protected function _correct($mask = self::MASK_ALLPARTS, $down = false)
-    {
-        if ($mask & self::MASK_SECOND) {
-            if ($this->_sec < 0 || $this->_sec > 59) {
-                $mask |= self::MASK_MINUTE;
-
-                $this->_min += (int)($this->_sec / 60);
-                $this->_sec %= 60;
-                if ($this->_sec < 0) {
-                    $this->_min--;
-                    $this->_sec += 60;
-                }
-            }
-        }
-
-        if ($mask & self::MASK_MINUTE) {
-            if ($this->_min < 0 || $this->_min > 59) {
-                $mask |= self::MASK_HOUR;
-
-                $this->_hour += (int)($this->_min / 60);
-                $this->_min %= 60;
-                if ($this->_min < 0) {
-                    $this->_hour--;
-                    $this->_min += 60;
-                }
-            }
-        }
-
-        if ($mask & self::MASK_HOUR) {
-            if ($this->_hour < 0 || $this->_hour > 23) {
-                $mask |= self::MASK_DAY;
-
-                $this->_mday += (int)($this->_hour / 24);
-                $this->_hour %= 24;
-                if ($this->_hour < 0) {
-                    $this->_mday--;
-                    $this->_hour += 24;
-                }
-            }
-        }
-
-        if ($mask & self::MASK_MONTH) {
-            $this->_correctMonth($down);
-            /* When correcting the month, always correct the day too. Months
-             * have different numbers of days. */
-            $mask |= self::MASK_DAY;
-        }
-
-        if ($mask & self::MASK_DAY) {
-            while ($this->_mday > 28 &&
-                   $this->_mday > Horde_Date_Utils::daysInMonth($this->_month, $this->_year)) {
-                if ($down) {
-                    $this->_mday -= Horde_Date_Utils::daysInMonth($this->_month + 1, $this->_year) - Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
-                } else {
-                    $this->_mday -= Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
-                    $this->_month++;
-                }
-                $this->_correctMonth($down);
-            }
-            while ($this->_mday < 1) {
-                --$this->_month;
-                $this->_correctMonth($down);
-                $this->_mday += Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
-            }
-        }
-    }
-
-    /**
-     * Corrects the current month.
-     *
-     * This cannot be done in _correct() because that would also trigger a
-     * correction of the day, which would result in an infinite loop.
-     *
-     * @param integer $down  Whether to correct the date up or down.
-     */
-    protected function _correctMonth($down = false)
-    {
-        $this->_year += (int)($this->_month / 12);
-        $this->_month %= 12;
-        if ($this->_month < 1) {
-            $this->_year--;
-            $this->_month += 12;
-        }
-    }
-
-    /**
-     * Handles args in order: year month day hour min sec tz
-     */
-    protected function _initializeFromArgs($args)
-    {
-        $tz = (isset($args[6])) ? array_pop($args) : null;
-        $this->_initializeTimezone($tz);
-
-        $args = array_slice($args, 0, 6);
-        $keys = array('year' => 1, 'month' => 1, 'mday' => 1, 'hour' => 0, 'min' => 0, 'sec' => 0);
-        $date = array_combine(array_slice(array_keys($keys), 0, count($args)), $args);
-        $date = array_merge($keys, $date);
-
-        $this->_initializeFromArray($date);
-    }
-
-    protected function _initializeFromArray($date)
-    {
-        if (isset($date['year']) && is_string($date['year']) && strlen($date['year']) == 2) {
-            if ($date['year'] > 70) {
-                $date['year'] += 1900;
-            } else {
-                $date['year'] += 2000;
-            }
-        }
-
-        foreach ($date as $key => $val) {
-            if (in_array($key, array('year', 'month', 'mday', 'hour', 'min', 'sec'))) {
-                $this->{'_'. $key} = (int)$val;
-            }
-        }
-
-        // If $date['day'] is present and numeric we may have been passed
-        // a Horde_Form_datetime array.
-        if (isset($date['day']) &&
-            (string)(int)$date['day'] == $date['day']) {
-            $this->_mday = (int)$date['day'];
-        }
-        // 'minute' key also from Horde_Form_datetime
-        if (isset($date['minute']) &&
-            (string)(int)$date['minute'] == $date['minute']) {
-            $this->_min = (int)$date['minute'];
-        }
-
-        $this->_correct();
-    }
-
-    protected function _initializeFromObject($date)
-    {
-        if ($date instanceof DateTime) {
-            $this->_year  = (int)$date->format('Y');
-            $this->_month = (int)$date->format('m');
-            $this->_mday  = (int)$date->format('d');
-            $this->_hour  = (int)$date->format('H');
-            $this->_min   = (int)$date->format('i');
-            $this->_sec   = (int)$date->format('s');
-            $this->_initializeTimezone($date->getTimezone()->getName());
-        } else {
-            $is_horde_date = $date instanceof Horde_Date;
-            foreach (array('year', 'month', 'mday', 'hour', 'min', 'sec') as $key) {
-                if ($is_horde_date || isset($date->$key)) {
-                    $this->{'_' . $key} = (int)$date->$key;
-                }
-            }
-            if (!$is_horde_date) {
-                $this->_correct();
-            } else {
-                $this->_initializeTimezone($date->timezone);
-            }
-        }
-    }
-
-    protected function _initializeTimezone($timezone)
-    {
-        if (empty($timezone)) {
-            $timezone = date_default_timezone_get();
-        }
-        $this->_timezone = $timezone;
-    }
-
-}
-
-/**
- * @category Horde
- * @package  Date
- */
-
-/**
- * Horde Date wrapper/logic class, including some calculation
- * functions.
- *
- * @category Horde
- * @package  Date
- */
-class Horde_Date_Utils
-{
-    /**
-     * Returns whether a year is a leap year.
-     *
-     * @param integer $year  The year.
-     *
-     * @return boolean  True if the year is a leap year.
-     */
-    public static function isLeapYear($year)
-    {
-        if (strlen($year) != 4 || preg_match('/\D/', $year)) {
-            return false;
-        }
-
-        return (($year % 4 == 0 && $year % 100 != 0) || $year % 400 == 0);
-    }
-
-    /**
-     * Returns the date of the year that corresponds to the first day of the
-     * given week.
-     *
-     * @param integer $week  The week of the year to find the first day of.
-     * @param integer $year  The year to calculate for.
-     *
-     * @return Horde_Date  The date of the first day of the given week.
-     */
-    public static function firstDayOfWeek($week, $year)
-    {
-        return new Horde_Date(sprintf('%04dW%02d', $year, $week));
-    }
-
-    /**
-     * Returns the number of days in the specified month.
-     *
-     * @param integer $month  The month
-     * @param integer $year   The year.
-     *
-     * @return integer  The number of days in the month.
-     */
-    public static function daysInMonth($month, $year)
-    {
-        static $cache = array();
-        if (!isset($cache[$year][$month])) {
-            $date = new DateTime(sprintf('%04d-%02d-01', $year, $month));
-            $cache[$year][$month] = $date->format('t');
-        }
-        return $cache[$year][$month];
-    }
-
-    /**
-     * Returns a relative, natural language representation of a timestamp
-     *
-     * @todo Wider range of values ... maybe future time as well?
-     * @todo Support minimum resolution parameter.
-     *
-     * @param mixed $time          The time. Any format accepted by Horde_Date.
-     * @param string $date_format  Format to display date if timestamp is
-     *                             more then 1 day old.
-     * @param string $time_format  Format to display time if timestamp is 1
-     *                             day old.
-     *
-     * @return string  The relative time (i.e. 2 minutes ago)
-     */
-    public static function relativeDateTime($time, $date_format = '%x',
-                                            $time_format = '%X')
-    {
-        $date = new Horde_Date($time);
-
-        $delta = time() - $date->timestamp();
-        if ($delta < 60) {
-            return sprintf(Horde_Date_Translation::ngettext("%d second ago", "%d seconds ago", $delta), $delta);
-        }
-
-        $delta = round($delta / 60);
-        if ($delta < 60) {
-            return sprintf(Horde_Date_Translation::ngettext("%d minute ago", "%d minutes ago", $delta), $delta);
-        }
-
-        $delta = round($delta / 60);
-        if ($delta < 24) {
-            return sprintf(Horde_Date_Translation::ngettext("%d hour ago", "%d hours ago", $delta), $delta);
-        }
-
-        if ($delta > 24 && $delta < 48) {
-            $date = new Horde_Date($time);
-            return sprintf(Horde_Date_Translation::t("yesterday at %s"), $date->strftime($time_format));
-        }
-
-        $delta = round($delta / 24);
-        if ($delta < 7) {
-            return sprintf(Horde_Date_Translation::t("%d days ago"), $delta);
-        }
-
-        if (round($delta / 7) < 5) {
-            $delta = round($delta / 7);
-            return sprintf(Horde_Date_Translation::ngettext("%d week ago", "%d weeks ago", $delta), $delta);
-        }
-
-        // Default to the user specified date format.
-        return $date->strftime($date_format);
-    }
-
-    /**
-     * Tries to convert strftime() formatters to date() formatters.
-     *
-     * Unsupported formatters will be removed.
-     *
-     * @param string $format  A strftime() formatting string.
-     *
-     * @return string  A date() formatting string.
-     */
-    public static function strftime2date($format)
-    {
-        $replace = array(
-            '/%a/'  => 'D',
-            '/%A/'  => 'l',
-            '/%d/'  => 'd',
-            '/%e/'  => 'j',
-            '/%j/'  => 'z',
-            '/%u/'  => 'N',
-            '/%w/'  => 'w',
-            '/%U/'  => '',
-            '/%V/'  => 'W',
-            '/%W/'  => '',
-            '/%b/'  => 'M',
-            '/%B/'  => 'F',
-            '/%h/'  => 'M',
-            '/%m/'  => 'm',
-            '/%C/'  => '',
-            '/%g/'  => '',
-            '/%G/'  => 'o',
-            '/%y/'  => 'y',
-            '/%Y/'  => 'Y',
-            '/%H/'  => 'H',
-            '/%I/'  => 'h',
-            '/%i/'  => 'g',
-            '/%M/'  => 'i',
-            '/%p/'  => 'A',
-            '/%P/'  => 'a',
-            '/%r/'  => 'h:i:s A',
-            '/%R/'  => 'H:i',
-            '/%S/'  => 's',
-            '/%T/'  => 'H:i:s',
-            '/%X/e' => 'Horde_Date_Utils::strftime2date(Horde_Nls::getLangInfo(T_FMT))',
-            '/%z/'  => 'O',
-            '/%Z/'  => '',
-            '/%c/'  => '',
-            '/%D/'  => 'm/d/y',
-            '/%F/'  => 'Y-m-d',
-            '/%s/'  => 'U',
-            '/%x/e' => 'Horde_Date_Utils::strftime2date(Horde_Nls::getLangInfo(D_FMT))',
-            '/%n/'  => "\n",
-            '/%t/'  => "\t",
-            '/%%/'  => '%'
-        );
-
-        return preg_replace(array_keys($replace), array_values($replace), $format);
-    }
-
-}
diff --git a/plugins/libcalendaring/lib/Horde_Date_Recurrence.php b/plugins/libcalendaring/lib/Horde_Date_Recurrence.php
deleted file mode 100644
index 4dfdfaf6..00000000
--- a/plugins/libcalendaring/lib/Horde_Date_Recurrence.php
+++ /dev/null
@@ -1,1747 +0,0 @@
-<?php
-
-/**
- * This is a modified copy of Horde/Date/Recurrence.php (2015-01-05)
- * Pull the latest version of this file from the PEAR channel of the Horde
- * project at http://pear.horde.org by installing the Horde_Date package.
- */
-
-if (!class_exists('Horde_Date')) {
-    require_once(__DIR__ . '/Horde_Date.php');
-}
-
-// minimal required implementation of Horde_Date_Translation to avoid a huge dependency nightmare
-class Horde_Date_Translation
-{
-    function t($arg) { return $arg; }
-    function ngettext($sing, $plur, $num) { return ($num > 1 ? $plur : $sing); }
-}
-
-
-/**
- * This file contains the Horde_Date_Recurrence class and according constants.
- *
- * Copyright 2007-2015 Horde LLC (http://www.horde.org/)
- *
- * See the enclosed file COPYING for license information (LGPL). If you
- * did not receive this file, see http://www.horde.org/licenses/lgpl21.
- *
- * @category Horde
- * @package  Date
- */
-
-/**
- * The Horde_Date_Recurrence class implements algorithms for calculating
- * recurrences of events, including several recurrence types, intervals,
- * exceptions, and conversion from and to vCalendar and iCalendar recurrence
- * rules.
- *
- * All methods expecting dates as parameters accept all values that the
- * Horde_Date constructor accepts, i.e. a timestamp, another Horde_Date
- * object, an ISO time string or a hash.
- *
- * @author   Jan Schneider <jan@horde.org>
- * @category Horde
- * @package  Date
- */
-class Horde_Date_Recurrence
-{
-    /** No Recurrence **/
-    const RECUR_NONE = 0;
-
-    /** Recurs daily. */
-    const RECUR_DAILY = 1;
-
-    /** Recurs weekly. */
-    const RECUR_WEEKLY = 2;
-
-    /** Recurs monthly on the same date. */
-    const RECUR_MONTHLY_DATE = 3;
-
-    /** Recurs monthly on the same week day. */
-    const RECUR_MONTHLY_WEEKDAY = 4;
-
-    /** Recurs yearly on the same date. */
-    const RECUR_YEARLY_DATE = 5;
-
-    /** Recurs yearly on the same day of the year. */
-    const RECUR_YEARLY_DAY = 6;
-
-    /** Recurs yearly on the same week day. */
-    const RECUR_YEARLY_WEEKDAY = 7;
-
-    /**
-     * The start time of the event.
-     *
-     * @var Horde_Date
-     */
-    public $start;
-
-    /**
-     * The end date of the recurrence interval.
-     *
-     * @var Horde_Date
-     */
-    public $recurEnd = null;
-
-    /**
-     * The number of recurrences.
-     *
-     * @var integer
-     */
-    public $recurCount = null;
-
-    /**
-     * The type of recurrence this event follows. RECUR_* constant.
-     *
-     * @var integer
-     */
-    public $recurType = self::RECUR_NONE;
-
-    /**
-     * The length of time between recurrences. The time unit depends on the
-     * recurrence type.
-     *
-     * @var integer
-     */
-    public $recurInterval = 1;
-
-    /**
-     * Any additional recurrence data.
-     *
-     * @var integer
-     */
-    public $recurData = null;
-
-    /**
-     * BYDAY recurrence number
-     *
-     * @var integer
-     */
-    public $recurNthDay = null;
-
-    /**
-     * BYMONTH recurrence data
-     *
-     * @var array
-     */
-    public $recurMonths = array();
-
-    /**
-     * RDATE recurrence values
-     *
-     * @var array
-     */
-    public $rdates = array();
-
-    /**
-     * All the exceptions from recurrence for this event.
-     *
-     * @var array
-     */
-    public $exceptions = array();
-
-    /**
-     * All the dates this recurrence has been marked as completed.
-     *
-     * @var array
-     */
-    public $completions = array();
-
-    /**
-     * Constructor.
-     *
-     * @param Horde_Date $start  Start of the recurring event.
-     */
-    public function __construct($start)
-    {
-        $this->start = new Horde_Date($start);
-    }
-
-    /**
-     * Resets the class properties.
-     */
-    public function reset()
-    {
-        $this->recurEnd = null;
-        $this->recurCount = null;
-        $this->recurType = self::RECUR_NONE;
-        $this->recurInterval = 1;
-        $this->recurData = null;
-        $this->exceptions = array();
-        $this->completions = array();
-    }
-
-    /**
-     * Checks if this event recurs on a given day of the week.
-     *
-     * @param integer $dayMask  A mask consisting of Horde_Date::MASK_*
-     *                          constants specifying the day(s) to check.
-     *
-     * @return boolean  True if this event recurs on the given day(s).
-     */
-    public function recurOnDay($dayMask)
-    {
-        return ($this->recurData & $dayMask);
-    }
-
-    /**
-     * Specifies the days this event recurs on.
-     *
-     * @param integer $dayMask  A mask consisting of Horde_Date::MASK_*
-     *                          constants specifying the day(s) to recur on.
-     */
-    public function setRecurOnDay($dayMask)
-    {
-        $this->recurData = $dayMask;
-    }
-
-    /**
-     *
-     * @param integer $nthDay The nth weekday of month to repeat events on
-     */
-    public function setRecurNthWeekday($nth)
-    {
-        $this->recurNthDay = (int)$nth;
-    }
-
-    /**
-     *
-     * @return integer  The nth weekday of month to repeat events.
-     */
-    public function getRecurNthWeekday()
-    {
-        return isset($this->recurNthDay) ? $this->recurNthDay : ceil($this->start->mday / 7);
-    }
-
-    /**
-     * Specifies the months for yearly (weekday) recurrence
-     *
-     * @param array $months  List of months (integers) this event recurs on.
-     */
-    function setRecurByMonth($months)
-    {
-        $this->recurMonths = (array)$months;
-    }
-
-    /**
-     * Returns a list of months this yearly event recurs on
-     *
-     * @return array List of months (integers) this event recurs on.
-     */
-    function getRecurByMonth()
-    {
-        return $this->recurMonths;
-    }
-
-    /**
-     * Returns the days this event recurs on.
-     *
-     * @return integer  A mask consisting of Horde_Date::MASK_* constants
-     *                  specifying the day(s) this event recurs on.
-     */
-    public function getRecurOnDays()
-    {
-        return $this->recurData;
-    }
-
-    /**
-     * Returns whether this event has a specific recurrence type.
-     *
-     * @param integer $recurrence  RECUR_* constant of the
-     *                             recurrence type to check for.
-     *
-     * @return boolean  True if the event has the specified recurrence type.
-     */
-    public function hasRecurType($recurrence)
-    {
-        return ($recurrence == $this->recurType);
-    }
-
-    /**
-     * Sets a recurrence type for this event.
-     *
-     * @param integer $recurrence  A RECUR_* constant.
-     */
-    public function setRecurType($recurrence)
-    {
-        $this->recurType = $recurrence;
-    }
-
-    /**
-     * Returns recurrence type of this event.
-     *
-     * @return integer  A RECUR_* constant.
-     */
-    public function getRecurType()
-    {
-        return $this->recurType;
-    }
-
-    /**
-     * Returns a description of this event's recurring type.
-     *
-     * @return string  Human readable recurring type.
-     */
-    public function getRecurName()
-    {
-        switch ($this->getRecurType()) {
-        case self::RECUR_NONE:
-            return Horde_Date_Translation::t("No recurrence");
-        case self::RECUR_DAILY:
-            return Horde_Date_Translation::t("Daily");
-        case self::RECUR_WEEKLY:
-            return Horde_Date_Translation::t("Weekly");
-        case self::RECUR_MONTHLY_DATE:
-        case self::RECUR_MONTHLY_WEEKDAY:
-            return Horde_Date_Translation::t("Monthly");
-        case self::RECUR_YEARLY_DATE:
-        case self::RECUR_YEARLY_DAY:
-        case self::RECUR_YEARLY_WEEKDAY:
-            return Horde_Date_Translation::t("Yearly");
-        }
-    }
-
-    /**
-     * Sets the length of time between recurrences of this event.
-     *
-     * @param integer $interval  The time between recurrences.
-     */
-    public function setRecurInterval($interval)
-    {
-        if ($interval > 0) {
-            $this->recurInterval = $interval;
-        }
-    }
-
-    /**
-     * Retrieves the length of time between recurrences of this event.
-     *
-     * @return integer  The number of seconds between recurrences.
-     */
-    public function getRecurInterval()
-    {
-        return $this->recurInterval;
-    }
-
-    /**
-     * Sets the number of recurrences of this event.
-     *
-     * @param integer $count  The number of recurrences.
-     */
-    public function setRecurCount($count)
-    {
-        if ($count > 0) {
-            $this->recurCount = (int)$count;
-            // Recurrence counts and end dates are mutually exclusive.
-            $this->recurEnd = null;
-        } else {
-            $this->recurCount = null;
-        }
-    }
-
-    /**
-     * Retrieves the number of recurrences of this event.
-     *
-     * @return integer  The number recurrences.
-     */
-    public function getRecurCount()
-    {
-        return $this->recurCount;
-    }
-
-    /**
-     * Returns whether this event has a recurrence with a fixed count.
-     *
-     * @return boolean  True if this recurrence has a fixed count.
-     */
-    public function hasRecurCount()
-    {
-        return isset($this->recurCount);
-    }
-
-    /**
-     * Sets the start date of the recurrence interval.
-     *
-     * @param Horde_Date $start  The recurrence start.
-     */
-    public function setRecurStart($start)
-    {
-        $this->start = clone $start;
-    }
-
-    /**
-     * Retrieves the start date of the recurrence interval.
-     *
-     * @return Horde_Date  The recurrence start.
-     */
-    public function getRecurStart()
-    {
-        return $this->start;
-    }
-
-    /**
-     * Sets the end date of the recurrence interval.
-     *
-     * @param Horde_Date $end  The recurrence end.
-     */
-    public function setRecurEnd($end)
-    {
-        if (!empty($end)) {
-            // Recurrence counts and end dates are mutually exclusive.
-            $this->recurCount = null;
-            $this->recurEnd = clone $end;
-        } else {
-            $this->recurEnd = $end;
-        }
-    }
-
-    /**
-     * Retrieves the end date of the recurrence interval.
-     *
-     * @return Horde_Date  The recurrence end.
-     */
-    public function getRecurEnd()
-    {
-        return $this->recurEnd;
-    }
-
-    /**
-     * Returns whether this event has a recurrence end.
-     *
-     * @return boolean  True if this recurrence ends.
-     */
-    public function hasRecurEnd()
-    {
-        return isset($this->recurEnd) && isset($this->recurEnd->year) &&
-            $this->recurEnd->year != 9999;
-    }
-
-    /**
-     * Finds the next recurrence of this event that's after $afterDate.
-     *
-     * @param Horde_Date|string $after  Return events after this date.
-     *
-     * @return Horde_Date|boolean  The date of the next recurrence or false
-     *                             if the event does not recur after
-     *                             $afterDate.
-     */
-    public function nextRecurrence($after)
-    {
-        if (!($after instanceof Horde_Date)) {
-            $after = new Horde_Date($after);
-        } else {
-            $after = clone($after);
-        }
-
-        // Make sure $after and $this->start are in the same TZ
-        $after->setTimezone($this->start->timezone);
-        if ($this->start->compareDateTime($after) >= 0) {
-            return clone $this->start;
-        }
-
-        if ($this->recurInterval == 0 && empty($this->rdates)) {
-            return false;
-        }
-
-        switch ($this->getRecurType()) {
-        case self::RECUR_DAILY:
-            $diff = $this->start->diff($after);
-            $recur = ceil($diff / $this->recurInterval);
-            if ($this->recurCount && $recur >= $this->recurCount) {
-                return false;
-            }
-
-            $recur *= $this->recurInterval;
-            $next = $this->start->add(array('day' => $recur));
-            if ((!$this->hasRecurEnd() ||
-                 $next->compareDateTime($this->recurEnd) <= 0) &&
-                $next->compareDateTime($after) >= 0) {
-                return $next;
-            }
-
-            break;
-
-        case self::RECUR_WEEKLY:
-            if (empty($this->recurData)) {
-                return false;
-            }
-
-            $start_week = Horde_Date_Utils::firstDayOfWeek($this->start->format('W'),
-                                                           $this->start->year);
-            $start_week->timezone = $this->start->timezone;
-            $start_week->hour = $this->start->hour;
-            $start_week->min  = $this->start->min;
-            $start_week->sec  = $this->start->sec;
-
-            // Make sure we are not at the ISO-8601 first week of year while
-            // still in month 12...OR in the ISO-8601 last week of year while
-            // in month 1 and adjust the year accordingly.
-            $week = $after->format('W');
-            if ($week == 1 && $after->month == 12) {
-                $theYear = $after->year + 1;
-            } elseif ($week >= 52 && $after->month == 1) {
-                $theYear = $after->year - 1;
-            } else {
-                $theYear = $after->year;
-            }
-
-            $after_week = Horde_Date_Utils::firstDayOfWeek($week, $theYear);
-            $after_week->timezone = $this->start->timezone;
-            $after_week_end = clone $after_week;
-            $after_week_end->mday += 7;
-
-            $diff = $start_week->diff($after_week);
-            $interval = $this->recurInterval * 7;
-            $repeats = floor($diff / $interval);
-            if ($diff % $interval < 7) {
-                $recur = $diff;
-            } else {
-                /**
-                 * If the after_week is not in the first week interval the
-                 * search needs to skip ahead a complete interval. The way it is
-                 * calculated here means that an event that occurs every second
-                 * week on Monday and Wednesday with the event actually starting
-                 * on Tuesday or Wednesday will only have one incidence in the
-                 * first week.
-                 */
-                $recur = $interval * ($repeats + 1);
-            }
-
-            if ($this->hasRecurCount()) {
-                $recurrences = 0;
-                /**
-                 * Correct the number of recurrences by the number of events
-                 * that lay between the start of the start week and the
-                 * recurrence start.
-                 */
-                $next = clone $start_week;
-                while ($next->compareDateTime($this->start) < 0) {
-                    if ($this->recurOnDay((int)pow(2, $next->dayOfWeek()))) {
-                        $recurrences--;
-                    }
-                    ++$next->mday;
-                }
-                if ($repeats > 0) {
-                    $weekdays = $this->recurData;
-                    $total_recurrences_per_week = 0;
-                    while ($weekdays > 0) {
-                        if ($weekdays % 2) {
-                            $total_recurrences_per_week++;
-                        }
-                        $weekdays = ($weekdays - ($weekdays % 2)) / 2;
-                    }
-                    $recurrences += $total_recurrences_per_week * $repeats;
-                }
-            }
-
-            $next = clone $start_week;
-            $next->mday += $recur;
-            while ($next->compareDateTime($after) < 0 &&
-                   $next->compareDateTime($after_week_end) < 0) {
-                if ($this->hasRecurCount()
-                    && $next->compareDateTime($after) < 0
-                    && $this->recurOnDay((int)pow(2, $next->dayOfWeek()))) {
-                    $recurrences++;
-                }
-                ++$next->mday;
-            }
-            if ($this->hasRecurCount() &&
-                $recurrences >= $this->recurCount) {
-                return false;
-            }
-            if (!$this->hasRecurEnd() ||
-                $next->compareDateTime($this->recurEnd) <= 0) {
-                if ($next->compareDateTime($after_week_end) >= 0) {
-                    return $this->nextRecurrence($after_week_end);
-                }
-                while (!$this->recurOnDay((int)pow(2, $next->dayOfWeek())) &&
-                       $next->compareDateTime($after_week_end) < 0) {
-                    ++$next->mday;
-                }
-                if (!$this->hasRecurEnd() ||
-                    $next->compareDateTime($this->recurEnd) <= 0) {
-                    if ($next->compareDateTime($after_week_end) >= 0) {
-                        return $this->nextRecurrence($after_week_end);
-                    } else {
-                        return $next;
-                    }
-                }
-            }
-            break;
-
-        case self::RECUR_MONTHLY_DATE:
-            $start = clone $this->start;
-            if ($after->compareDateTime($start) < 0) {
-                $after = clone $start;
-            } else {
-                $after = clone $after;
-            }
-
-            // If we're starting past this month's recurrence of the event,
-            // look in the next month on the day the event recurs.
-            if ($after->mday > $start->mday) {
-                ++$after->month;
-                $after->mday = $start->mday;
-            }
-
-            // Adjust $start to be the first match.
-            $offset = ($after->month - $start->month) + ($after->year - $start->year) * 12;
-            $offset = floor(($offset + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
-
-            if ($this->recurCount &&
-                ($offset / $this->recurInterval) >= $this->recurCount) {
-                return false;
-            }
-            $start->month += $offset;
-            $count = $offset / $this->recurInterval;
-
-            do {
-                if ($this->recurCount &&
-                    $count++ >= $this->recurCount) {
-                    return false;
-                }
-
-                // Bail if we've gone past the end of recurrence.
-                if ($this->hasRecurEnd() &&
-                    $this->recurEnd->compareDateTime($start) < 0) {
-                    return false;
-                }
-                if ($start->isValid()) {
-                    return $start;
-                }
-
-                // If the interval is 12, and the date isn't valid, then we
-                // need to see if February 29th is an option. If not, then the
-                // event will _never_ recur, and we need to stop checking to
-                // avoid an infinite loop.
-                if ($this->recurInterval == 12 && ($start->month != 2 || $start->mday > 29)) {
-                    return false;
-                }
-
-                // Add the recurrence interval.
-                $start->month += $this->recurInterval;
-            } while (true);
-
-            break;
-
-        case self::RECUR_MONTHLY_WEEKDAY:
-            // Start with the start date of the event.
-            $estart = clone $this->start;
-
-            // What day of the week, and week of the month, do we recur on?
-            if (isset($this->recurNthDay)) {
-                $nth = $this->recurNthDay;
-                $weekday = log($this->recurData, 2);
-            } else {
-                $nth = ceil($this->start->mday / 7);
-                $weekday = $estart->dayOfWeek();
-            }
-
-            // Adjust $estart to be the first candidate.
-            $offset = ($after->month - $estart->month) + ($after->year - $estart->year) * 12;
-            $offset = floor(($offset + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
-
-            // Adjust our working date until it's after $after.
-            $estart->month += $offset - $this->recurInterval;
-
-            $count = $offset / $this->recurInterval;
-            do {
-                if ($this->recurCount &&
-                    $count++ >= $this->recurCount) {
-                    return false;
-                }
-
-                $estart->month += $this->recurInterval;
-
-                $next = clone $estart;
-                $next->setNthWeekday($weekday, $nth);
-
-                if ($next->month != $estart->month) {
-                    // We're already in the next month.
-                    continue;
-                }
-                if ($next->compareDateTime($after) < 0) {
-                    // We haven't made it past $after yet, try again.
-                    continue;
-                }
-                if ($this->hasRecurEnd() &&
-                    $next->compareDateTime($this->recurEnd) > 0) {
-                    // We've gone past the end of recurrence; we can give up
-                    // now.
-                    return false;
-                }
-
-                // We have a candidate to return.
-                break;
-            } while (true);
-
-            return $next;
-
-        case self::RECUR_YEARLY_DATE:
-            // Start with the start date of the event.
-            $estart = clone $this->start;
-            $after = clone $after;
-
-            if ($after->month > $estart->month ||
-                ($after->month == $estart->month && $after->mday > $estart->mday)) {
-                ++$after->year;
-                $after->month = $estart->month;
-                $after->mday = $estart->mday;
-            }
-
-            // Seperate case here for February 29th
-            if ($estart->month == 2 && $estart->mday == 29) {
-                while (!Horde_Date_Utils::isLeapYear($after->year)) {
-                    ++$after->year;
-                }
-            }
-
-            // Adjust $estart to be the first candidate.
-            $offset = $after->year - $estart->year;
-            if ($offset > 0) {
-                $offset = floor(($offset + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
-                $estart->year += $offset;
-            }
-
-            // We've gone past the end of recurrence; give up.
-            if ($this->recurCount &&
-                $offset >= $this->recurCount) {
-                return false;
-            }
-            if ($this->hasRecurEnd() &&
-                $this->recurEnd->compareDateTime($estart) < 0) {
-                return false;
-            }
-
-            return $estart;
-
-        case self::RECUR_YEARLY_DAY:
-            // Check count first.
-            $dayofyear = $this->start->dayOfYear();
-            $count = ($after->year - $this->start->year) / $this->recurInterval + 1;
-            if ($this->recurCount &&
-                ($count > $this->recurCount ||
-                 ($count == $this->recurCount &&
-                  $after->dayOfYear() > $dayofyear))) {
-                return false;
-            }
-
-            // Start with a rough interval.
-            $estart = clone $this->start;
-            $estart->year += floor($count - 1) * $this->recurInterval;
-
-            // Now add the difference to the required day of year.
-            $estart->mday += $dayofyear - $estart->dayOfYear();
-
-            // Add an interval if the estimation was wrong.
-            if ($estart->compareDate($after) < 0) {
-                $estart->year += $this->recurInterval;
-                $estart->mday += $dayofyear - $estart->dayOfYear();
-            }
-
-            // We've gone past the end of recurrence; give up.
-            if ($this->hasRecurEnd() &&
-                $this->recurEnd->compareDateTime($estart) < 0) {
-                return false;
-            }
-
-            return $estart;
-
-        case self::RECUR_YEARLY_WEEKDAY:
-            // Start with the start date of the event.
-            $estart = clone $this->start;
-
-            // What day of the week, and week of the month, do we recur on?
-            if (isset($this->recurNthDay)) {
-                $nth = $this->recurNthDay;
-                $weekday = log($this->recurData, 2);
-            } else {
-                $nth = ceil($this->start->mday / 7);
-                $weekday = $estart->dayOfWeek();
-            }
-
-            // Adjust $estart to be the first candidate.
-            $offset = floor(($after->year - $estart->year + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
-
-            // Adjust our working date until it's after $after.
-            $estart->year += $offset - $this->recurInterval;
-
-            $count = $offset / $this->recurInterval;
-            do {
-                if ($this->recurCount &&
-                    $count++ >= $this->recurCount) {
-                    return false;
-                }
-
-                $estart->year += $this->recurInterval;
-
-                $next = clone $estart;
-                $next->setNthWeekday($weekday, $nth);
-
-                if ($next->compareDateTime($after) < 0) {
-                    // We haven't made it past $after yet, try again.
-                    continue;
-                }
-                if ($this->hasRecurEnd() &&
-                    $next->compareDateTime($this->recurEnd) > 0) {
-                    // We've gone past the end of recurrence; we can give up
-                    // now.
-                    return false;
-                }
-
-                // We have a candidate to return.
-                break;
-            } while (true);
-
-            return $next;
-        }
-
-        // fall-back to RDATE properties
-        if (!empty($this->rdates)) {
-            $next = clone $this->start;
-            foreach ($this->rdates as $rdate) {
-                $next->year  = $rdate->year;
-                $next->month = $rdate->month;
-                $next->mday  = $rdate->mday;
-                if ($next->compareDateTime($after) >= 0) {
-                    return $next;
-                }
-            }
-        }
-
-        // We didn't find anything, the recurType was bad, or something else
-        // went wrong - return false.
-        return false;
-    }
-
-    /**
-     * Returns whether this event has any date that matches the recurrence
-     * rules and is not an exception.
-     *
-     * @return boolean  True if an active recurrence exists.
-     */
-    public function hasActiveRecurrence()
-    {
-        if (!$this->hasRecurEnd()) {
-            return true;
-        }
-
-        $next = $this->nextRecurrence(new Horde_Date($this->start));
-        while (is_object($next)) {
-            if (!$this->hasException($next->year, $next->month, $next->mday) &&
-                !$this->hasCompletion($next->year, $next->month, $next->mday)) {
-                return true;
-            }
-
-            $next = $this->nextRecurrence($next->add(array('day' => 1)));
-        }
-
-        return false;
-    }
-
-    /**
-     * Returns the next active recurrence.
-     *
-     * @param Horde_Date $afterDate  Return events after this date.
-     *
-     * @return Horde_Date|boolean The date of the next active
-     *                             recurrence or false if the event
-     *                             has no active recurrence after
-     *                             $afterDate.
-     */
-    public function nextActiveRecurrence($afterDate)
-    {
-        $next = $this->nextRecurrence($afterDate);
-        while (is_object($next)) {
-            if (!$this->hasException($next->year, $next->month, $next->mday) &&
-                !$this->hasCompletion($next->year, $next->month, $next->mday)) {
-                return $next;
-            }
-            $next->mday++;
-            $next = $this->nextRecurrence($next);
-        }
-
-        return false;
-    }
-
-    /**
-     * Adds an absolute recurrence date.
-     *
-     * @param integer $year   The year of the instance.
-     * @param integer $month  The month of the instance.
-     * @param integer $mday   The day of the month of the instance.
-     */
-    public function addRDate($year, $month, $mday)
-    {
-        $this->rdates[] = new Horde_Date($year, $month, $mday);
-    }
-
-    /**
-     * Adds an exception to a recurring event.
-     *
-     * @param integer $year   The year of the execption.
-     * @param integer $month  The month of the execption.
-     * @param integer $mday   The day of the month of the exception.
-     */
-    public function addException($year, $month, $mday)
-    {
-        $key = sprintf('%04d%02d%02d', $year, $month, $mday);
-        if (array_search($key, $this->exceptions) === false) {
-            $this->exceptions[] = sprintf('%04d%02d%02d', $year, $month, $mday);
-        }
-    }
-
-    /**
-     * Deletes an exception from a recurring event.
-     *
-     * @param integer $year   The year of the execption.
-     * @param integer $month  The month of the execption.
-     * @param integer $mday   The day of the month of the exception.
-     */
-    public function deleteException($year, $month, $mday)
-    {
-        $key = array_search(sprintf('%04d%02d%02d', $year, $month, $mday), $this->exceptions);
-        if ($key !== false) {
-            unset($this->exceptions[$key]);
-        }
-    }
-
-    /**
-     * Checks if an exception exists for a given reccurence of an event.
-     *
-     * @param integer $year   The year of the reucrance.
-     * @param integer $month  The month of the reucrance.
-     * @param integer $mday   The day of the month of the reucrance.
-     *
-     * @return boolean  True if an exception exists for the given date.
-     */
-    public function hasException($year, $month, $mday)
-    {
-        return in_array(sprintf('%04d%02d%02d', $year, $month, $mday),
-                        $this->getExceptions());
-    }
-
-    /**
-     * Retrieves all the exceptions for this event.
-     *
-     * @return array  Array containing the dates of all the exceptions in
-     *                YYYYMMDD form.
-     */
-    public function getExceptions()
-    {
-        return $this->exceptions;
-    }
-
-    /**
-     * Adds a completion to a recurring event.
-     *
-     * @param integer $year   The year of the execption.
-     * @param integer $month  The month of the execption.
-     * @param integer $mday   The day of the month of the completion.
-     */
-    public function addCompletion($year, $month, $mday)
-    {
-        $this->completions[] = sprintf('%04d%02d%02d', $year, $month, $mday);
-    }
-
-    /**
-     * Deletes a completion from a recurring event.
-     *
-     * @param integer $year   The year of the execption.
-     * @param integer $month  The month of the execption.
-     * @param integer $mday   The day of the month of the completion.
-     */
-    public function deleteCompletion($year, $month, $mday)
-    {
-        $key = array_search(sprintf('%04d%02d%02d', $year, $month, $mday), $this->completions);
-        if ($key !== false) {
-            unset($this->completions[$key]);
-        }
-    }
-
-    /**
-     * Checks if a completion exists for a given reccurence of an event.
-     *
-     * @param integer $year   The year of the reucrance.
-     * @param integer $month  The month of the recurrance.
-     * @param integer $mday   The day of the month of the recurrance.
-     *
-     * @return boolean  True if a completion exists for the given date.
-     */
-    public function hasCompletion($year, $month, $mday)
-    {
-        return in_array(sprintf('%04d%02d%02d', $year, $month, $mday),
-                        $this->getCompletions());
-    }
-
-    /**
-     * Retrieves all the completions for this event.
-     *
-     * @return array  Array containing the dates of all the completions in
-     *                YYYYMMDD form.
-     */
-    public function getCompletions()
-    {
-        return $this->completions;
-    }
-
-    /**
-     * Parses a vCalendar 1.0 recurrence rule.
-     *
-     * @link http://www.imc.org/pdi/vcal-10.txt
-     * @link http://www.shuchow.com/vCalAddendum.html
-     *
-     * @param string $rrule  A vCalendar 1.0 conform RRULE value.
-     */
-    public function fromRRule10($rrule)
-    {
-        $this->reset();
-
-        if (!$rrule) {
-            return;
-        }
-
-        if (!preg_match('/([A-Z]+)(\d+)?(.*)/', $rrule, $matches)) {
-            // No recurrence data - event does not recur.
-            $this->setRecurType(self::RECUR_NONE);
-        }
-
-        // Always default the recurInterval to 1.
-        $this->setRecurInterval(!empty($matches[2]) ? $matches[2] : 1);
-
-        $remainder = trim($matches[3]);
-
-        switch ($matches[1]) {
-        case 'D':
-            $this->setRecurType(self::RECUR_DAILY);
-            break;
-
-        case 'W':
-            $this->setRecurType(self::RECUR_WEEKLY);
-            if (!empty($remainder)) {
-                $mask = 0;
-                while (preg_match('/^ ?[A-Z]{2} ?/', $remainder, $matches)) {
-                    $day = trim($matches[0]);
-                    $remainder = substr($remainder, strlen($matches[0]));
-                    $mask |= $maskdays[$day];
-                }
-                $this->setRecurOnDay($mask);
-            } else {
-                // Recur on the day of the week of the original recurrence.
-                $maskdays = array(
-                    Horde_Date::DATE_SUNDAY => Horde_Date::MASK_SUNDAY,
-                    Horde_Date::DATE_MONDAY => Horde_Date::MASK_MONDAY,
-                    Horde_Date::DATE_TUESDAY => Horde_Date::MASK_TUESDAY,
-                    Horde_Date::DATE_WEDNESDAY => Horde_Date::MASK_WEDNESDAY,
-                    Horde_Date::DATE_THURSDAY => Horde_Date::MASK_THURSDAY,
-                    Horde_Date::DATE_FRIDAY => Horde_Date::MASK_FRIDAY,
-                    Horde_Date::DATE_SATURDAY => Horde_Date::MASK_SATURDAY,
-                );
-                $this->setRecurOnDay($maskdays[$this->start->dayOfWeek()]);
-            }
-            break;
-
-        case 'MP':
-            $this->setRecurType(self::RECUR_MONTHLY_WEEKDAY);
-            break;
-
-        case 'MD':
-            $this->setRecurType(self::RECUR_MONTHLY_DATE);
-            break;
-
-        case 'YM':
-            $this->setRecurType(self::RECUR_YEARLY_DATE);
-            break;
-
-        case 'YD':
-            $this->setRecurType(self::RECUR_YEARLY_DAY);
-            break;
-        }
-
-        // We don't support modifiers at the moment, strip them.
-        while ($remainder && !preg_match('/^(#\d+|\d{8})($| |T\d{6})/', $remainder)) {
-               $remainder = substr($remainder, 1);
-        }
-        if (!empty($remainder)) {
-            if (strpos($remainder, '#') === 0) {
-                $this->setRecurCount(substr($remainder, 1));
-            } else {
-                list($year, $month, $mday, $hour, $min, $sec, $tz) =
-                    sscanf($remainder, '%04d%02d%02dT%02d%02d%02d%s');
-                $this->setRecurEnd(new Horde_Date(array('year' => $year,
-                                                        'month' => $month,
-                                                        'mday' => $mday,
-                                                        'hour' => $hour,
-                                                        'min' => $min,
-                                                        'sec' => $sec),
-                                                  $tz == 'Z' ? 'UTC' : $this->start->timezone));
-            }
-        }
-    }
-
-    /**
-     * Creates a vCalendar 1.0 recurrence rule.
-     *
-     * @link http://www.imc.org/pdi/vcal-10.txt
-     * @link http://www.shuchow.com/vCalAddendum.html
-     *
-     * @param Horde_Icalendar $calendar  A Horde_Icalendar object instance.
-     *
-     * @return string  A vCalendar 1.0 conform RRULE value.
-     */
-    public function toRRule10($calendar)
-    {
-        switch ($this->recurType) {
-        case self::RECUR_NONE:
-            return '';
-
-        case self::RECUR_DAILY:
-            $rrule = 'D' . $this->recurInterval;
-            break;
-
-        case self::RECUR_WEEKLY:
-            $rrule = 'W' . $this->recurInterval;
-            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
-
-            for ($i = 0; $i <= 7; ++$i) {
-                if ($this->recurOnDay(pow(2, $i))) {
-                    $rrule .= ' ' . $vcaldays[$i];
-                }
-            }
-            break;
-
-        case self::RECUR_MONTHLY_DATE:
-            $rrule = 'MD' . $this->recurInterval . ' ' . trim($this->start->mday);
-            break;
-
-        case self::RECUR_MONTHLY_WEEKDAY:
-            $nth_weekday = (int)($this->start->mday / 7);
-            if (($this->start->mday % 7) > 0) {
-                $nth_weekday++;
-            }
-
-            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
-            $rrule = 'MP' . $this->recurInterval . ' ' . $nth_weekday . '+ ' . $vcaldays[$this->start->dayOfWeek()];
-
-            break;
-
-        case self::RECUR_YEARLY_DATE:
-            $rrule = 'YM' . $this->recurInterval . ' ' . trim($this->start->month);
-            break;
-
-        case self::RECUR_YEARLY_DAY:
-            $rrule = 'YD' . $this->recurInterval . ' ' . $this->start->dayOfYear();
-            break;
-
-        default:
-            return '';
-        }
-
-        if ($this->hasRecurEnd()) {
-            $recurEnd = clone $this->recurEnd;
-            return $rrule . ' ' . $calendar->_exportDateTime($recurEnd);
-        }
-
-        return $rrule . ' #' . (int)$this->getRecurCount();
-    }
-
-    /**
-     * Parses an iCalendar 2.0 recurrence rule.
-     *
-     * @link http://rfc.net/rfc2445.html#s4.3.10
-     * @link http://rfc.net/rfc2445.html#s4.8.5
-     * @link http://www.shuchow.com/vCalAddendum.html
-     *
-     * @param string $rrule  An iCalendar 2.0 conform RRULE value.
-     */
-    public function fromRRule20($rrule)
-    {
-        $this->reset();
-
-        // Parse the recurrence rule into keys and values.
-        $rdata = array();
-        $parts = explode(';', $rrule);
-        foreach ($parts as $part) {
-            $value = null;
-            if (strpos($part, '=')) {
-                list($part, $value) = explode('=', $part, 2);
-            }
-            $rdata[strtoupper($part)] = $value;
-        }
-
-        if (isset($rdata['FREQ'])) {
-            // Always default the recurInterval to 1.
-            $this->setRecurInterval(isset($rdata['INTERVAL']) ? $rdata['INTERVAL'] : 1);
-
-            $maskdays = array(
-                'SU' => Horde_Date::MASK_SUNDAY,
-                'MO' => Horde_Date::MASK_MONDAY,
-                'TU' => Horde_Date::MASK_TUESDAY,
-                'WE' => Horde_Date::MASK_WEDNESDAY,
-                'TH' => Horde_Date::MASK_THURSDAY,
-                'FR' => Horde_Date::MASK_FRIDAY,
-                'SA' => Horde_Date::MASK_SATURDAY,
-            );
-
-            switch (strtoupper($rdata['FREQ'])) {
-            case 'DAILY':
-                $this->setRecurType(self::RECUR_DAILY);
-                break;
-
-            case 'WEEKLY':
-                $this->setRecurType(self::RECUR_WEEKLY);
-                if (isset($rdata['BYDAY'])) {
-                    $days = explode(',', $rdata['BYDAY']);
-                    $mask = 0;
-                    foreach ($days as $day) {
-                        $mask |= $maskdays[$day];
-                    }
-                    $this->setRecurOnDay($mask);
-                } else {
-                    // Recur on the day of the week of the original
-                    // recurrence.
-                    $maskdays = array(
-                        Horde_Date::DATE_SUNDAY => Horde_Date::MASK_SUNDAY,
-                        Horde_Date::DATE_MONDAY => Horde_Date::MASK_MONDAY,
-                        Horde_Date::DATE_TUESDAY => Horde_Date::MASK_TUESDAY,
-                        Horde_Date::DATE_WEDNESDAY => Horde_Date::MASK_WEDNESDAY,
-                        Horde_Date::DATE_THURSDAY => Horde_Date::MASK_THURSDAY,
-                        Horde_Date::DATE_FRIDAY => Horde_Date::MASK_FRIDAY,
-                        Horde_Date::DATE_SATURDAY => Horde_Date::MASK_SATURDAY);
-                    $this->setRecurOnDay($maskdays[$this->start->dayOfWeek()]);
-                }
-                break;
-
-            case 'MONTHLY':
-                if (isset($rdata['BYDAY'])) {
-                    $this->setRecurType(self::RECUR_MONTHLY_WEEKDAY);
-                    if (preg_match('/(-?[1-4])([A-Z]+)/', $rdata['BYDAY'], $m)) {
-                        $this->setRecurOnDay($maskdays[$m[2]]);
-                        $this->setRecurNthWeekday($m[1]);
-                    }
-                } else {
-                    $this->setRecurType(self::RECUR_MONTHLY_DATE);
-                }
-                break;
-
-            case 'YEARLY':
-                if (isset($rdata['BYYEARDAY'])) {
-                    $this->setRecurType(self::RECUR_YEARLY_DAY);
-                } elseif (isset($rdata['BYDAY'])) {
-                    $this->setRecurType(self::RECUR_YEARLY_WEEKDAY);
-                    if (preg_match('/(-?[1-4])([A-Z]+)/', $rdata['BYDAY'], $m)) {
-                        $this->setRecurOnDay($maskdays[$m[2]]);
-                        $this->setRecurNthWeekday($m[1]);
-                    }
-                    if ($rdata['BYMONTH']) {
-                        $months = explode(',', $rdata['BYMONTH']);
-                        $this->setRecurByMonth($months);
-                    }
-                } else {
-                    $this->setRecurType(self::RECUR_YEARLY_DATE);
-                }
-                break;
-            }
-
-            // MUST take into account the time portion if it is present.
-            // See Bug: 12869 and Bug: 2813
-            if (isset($rdata['UNTIL'])) {
-                if (preg_match('/^(\d{4})-?(\d{2})-?(\d{2})T? ?(\d{2}):?(\d{2}):?(\d{2})(?:\.\d+)?(Z?)$/', $rdata['UNTIL'], $parts)) {
-                    $until = new Horde_Date($rdata['UNTIL'], 'UTC');
-                    $until->setTimezone($this->start->timezone);
-                } else {
-                    list($year, $month, $mday) = sscanf($rdata['UNTIL'],
-                                                        '%04d%02d%02d');
-                    $until = new Horde_Date(
-                        array('year' => $year,
-                              'month' => $month,
-                              'mday' => $mday + 1),
-                        $this->start->timezone
-                    );
-                }
-                $this->setRecurEnd($until);
-            }
-            if (isset($rdata['COUNT'])) {
-                $this->setRecurCount($rdata['COUNT']);
-            }
-        } else {
-            // No recurrence data - event does not recur.
-            $this->setRecurType(self::RECUR_NONE);
-        }
-    }
-
-    /**
-     * Creates an iCalendar 2.0 recurrence rule.
-     *
-     * @link http://rfc.net/rfc2445.html#s4.3.10
-     * @link http://rfc.net/rfc2445.html#s4.8.5
-     * @link http://www.shuchow.com/vCalAddendum.html
-     *
-     * @param Horde_Icalendar $calendar  A Horde_Icalendar object instance.
-     *
-     * @return string  An iCalendar 2.0 conform RRULE value.
-     */
-    public function toRRule20($calendar)
-    {
-        switch ($this->recurType) {
-        case self::RECUR_NONE:
-            return '';
-
-        case self::RECUR_DAILY:
-            $rrule = 'FREQ=DAILY;INTERVAL='  . $this->recurInterval;
-            break;
-
-        case self::RECUR_WEEKLY:
-            $rrule = 'FREQ=WEEKLY;INTERVAL=' . $this->recurInterval;
-            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
-
-            for ($i = $flag = 0; $i <= 7; ++$i) {
-                if ($this->recurOnDay(pow(2, $i))) {
-                    if ($flag == 0) {
-                        $rrule .= ';BYDAY=';
-                        $flag = 1;
-                    } else {
-                        $rrule .= ',';
-                    }
-                    $rrule .= $vcaldays[$i];
-                }
-            }
-            break;
-
-        case self::RECUR_MONTHLY_DATE:
-            $rrule = 'FREQ=MONTHLY;INTERVAL=' . $this->recurInterval;
-            break;
-
-        case self::RECUR_MONTHLY_WEEKDAY:
-            if (isset($this->recurNthDay)) {
-                $nth_weekday = $this->recurNthDay;
-                $day_of_week = log($this->recurData, 2);
-            } else {
-                $day_of_week = $this->start->dayOfWeek();
-                $nth_weekday = (int)($this->start->mday / 7);
-                if (($this->start->mday % 7) > 0) {
-                    $nth_weekday++;
-                }
-            }
-            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
-            $rrule = 'FREQ=MONTHLY;INTERVAL=' . $this->recurInterval
-                . ';BYDAY=' . $nth_weekday . $vcaldays[$day_of_week];
-            break;
-
-        case self::RECUR_YEARLY_DATE:
-            $rrule = 'FREQ=YEARLY;INTERVAL=' . $this->recurInterval;
-            break;
-
-        case self::RECUR_YEARLY_DAY:
-            $rrule = 'FREQ=YEARLY;INTERVAL=' . $this->recurInterval
-                . ';BYYEARDAY=' . $this->start->dayOfYear();
-            break;
-
-        case self::RECUR_YEARLY_WEEKDAY:
-            if (isset($this->recurNthDay)) {
-                $nth_weekday = $this->recurNthDay;
-                $day_of_week = log($this->recurData, 2);
-            } else {
-                $day_of_week = $this->start->dayOfWeek();
-                $nth_weekday = (int)($this->start->mday / 7);
-                if (($this->start->mday % 7) > 0) {
-                    $nth_weekday++;
-                }
-             }
-            $months = !empty($this->recurMonths) ? join(',', $this->recurMonths) : $this->start->month;
-            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
-            $rrule = 'FREQ=YEARLY;INTERVAL=' . $this->recurInterval
-                . ';BYDAY='
-                . $nth_weekday
-                . $vcaldays[$day_of_week]
-                . ';BYMONTH=' . $this->start->month;
-            break;
-        }
-
-        if ($this->hasRecurEnd()) {
-            $recurEnd = clone $this->recurEnd;
-            $rrule .= ';UNTIL=' . $calendar->_exportDateTime($recurEnd);
-        }
-        if ($count = $this->getRecurCount()) {
-            $rrule .= ';COUNT=' . $count;
-        }
-        return $rrule;
-    }
-
-    /**
-     * Parses the recurrence data from a Kolab hash.
-     *
-     * @param array $hash  The hash to convert.
-     *
-     * @return boolean  True if the hash seemed valid, false otherwise.
-     */
-    public function fromKolab($hash)
-    {
-        $this->reset();
-
-        if (!isset($hash['interval']) || !isset($hash['cycle'])) {
-            $this->setRecurType(self::RECUR_NONE);
-            return false;
-        }
-
-        $this->setRecurInterval((int)$hash['interval']);
-
-        $month2number = array(
-            'january'   => 1,
-            'february'  => 2,
-            'march'     => 3,
-            'april'     => 4,
-            'may'       => 5,
-            'june'      => 6,
-            'july'      => 7,
-            'august'    => 8,
-            'september' => 9,
-            'october'   => 10,
-            'november'  => 11,
-            'december'  => 12,
-        );
-
-        $parse_day = false;
-        $set_daymask = false;
-        $update_month = false;
-        $update_daynumber = false;
-        $update_weekday = false;
-        $nth_weekday = -1;
-
-        switch ($hash['cycle']) {
-        case 'daily':
-            $this->setRecurType(self::RECUR_DAILY);
-            break;
-
-        case 'weekly':
-            $this->setRecurType(self::RECUR_WEEKLY);
-            $parse_day = true;
-            $set_daymask = true;
-            break;
-
-        case 'monthly':
-            if (!isset($hash['daynumber'])) {
-                $this->setRecurType(self::RECUR_NONE);
-                return false;
-            }
-
-            switch ($hash['type']) {
-            case 'daynumber':
-                $this->setRecurType(self::RECUR_MONTHLY_DATE);
-                $update_daynumber = true;
-                break;
-
-            case 'weekday':
-                $this->setRecurType(self::RECUR_MONTHLY_WEEKDAY);
-                $this->setRecurNthWeekday($hash['daynumber']);
-                $parse_day = true;
-                $set_daymask = true;
-                break;
-            }
-            break;
-
-        case 'yearly':
-            if (!isset($hash['type'])) {
-                $this->setRecurType(self::RECUR_NONE);
-                return false;
-            }
-
-            switch ($hash['type']) {
-            case 'monthday':
-                $this->setRecurType(self::RECUR_YEARLY_DATE);
-                $update_month = true;
-                $update_daynumber = true;
-                break;
-
-            case 'yearday':
-                if (!isset($hash['daynumber'])) {
-                    $this->setRecurType(self::RECUR_NONE);
-                    return false;
-                }
-
-                $this->setRecurType(self::RECUR_YEARLY_DAY);
-                // Start counting days in January.
-                $hash['month'] = 'january';
-                $update_month = true;
-                $update_daynumber = true;
-                break;
-
-            case 'weekday':
-                if (!isset($hash['daynumber'])) {
-                    $this->setRecurType(self::RECUR_NONE);
-                    return false;
-                }
-
-                $this->setRecurType(self::RECUR_YEARLY_WEEKDAY);
-                $this->setRecurNthWeekday($hash['daynumber']);
-                $parse_day = true;
-                $set_daymask = true;
-
-                if ($hash['month'] && isset($month2number[$hash['month']])) {
-                    $this->setRecurByMonth($month2number[$hash['month']]);
-                }
-                break;
-            }
-        }
-
-        if (isset($hash['range-type']) && isset($hash['range'])) {
-            switch ($hash['range-type']) {
-            case 'number':
-                $this->setRecurCount((int)$hash['range']);
-                break;
-
-            case 'date':
-                $recur_end = new Horde_Date($hash['range']);
-                $recur_end->hour = 23;
-                $recur_end->min = 59;
-                $recur_end->sec = 59;
-                $this->setRecurEnd($recur_end);
-                break;
-            }
-        }
-
-        // Need to parse <day>?
-        $last_found_day = -1;
-        if ($parse_day) {
-            if (!isset($hash['day'])) {
-                $this->setRecurType(self::RECUR_NONE);
-                return false;
-            }
-
-            $mask = 0;
-            $bits = array(
-                'monday' => Horde_Date::MASK_MONDAY,
-                'tuesday' => Horde_Date::MASK_TUESDAY,
-                'wednesday' => Horde_Date::MASK_WEDNESDAY,
-                'thursday' => Horde_Date::MASK_THURSDAY,
-                'friday' => Horde_Date::MASK_FRIDAY,
-                'saturday' => Horde_Date::MASK_SATURDAY,
-                'sunday' => Horde_Date::MASK_SUNDAY,
-            );
-            $days = array(
-                'monday' => Horde_Date::DATE_MONDAY,
-                'tuesday' => Horde_Date::DATE_TUESDAY,
-                'wednesday' => Horde_Date::DATE_WEDNESDAY,
-                'thursday' => Horde_Date::DATE_THURSDAY,
-                'friday' => Horde_Date::DATE_FRIDAY,
-                'saturday' => Horde_Date::DATE_SATURDAY,
-                'sunday' => Horde_Date::DATE_SUNDAY,
-            );
-
-            foreach ($hash['day'] as $day) {
-                // Validity check.
-                if (empty($day) || !isset($bits[$day])) {
-                    continue;
-                }
-
-                $mask |= $bits[$day];
-                $last_found_day = $days[$day];
-            }
-
-            if ($set_daymask) {
-                $this->setRecurOnDay($mask);
-            }
-        }
-
-        if ($update_month || $update_daynumber || $update_weekday) {
-            if ($update_month) {
-                if (isset($month2number[$hash['month']])) {
-                    $this->start->month = $month2number[$hash['month']];
-                }
-            }
-
-            if ($update_daynumber) {
-                if (!isset($hash['daynumber'])) {
-                    $this->setRecurType(self::RECUR_NONE);
-                    return false;
-                }
-
-                $this->start->mday = $hash['daynumber'];
-            }
-
-            if ($update_weekday) {
-                $this->setNthWeekday($nth_weekday);
-            }
-        }
-
-        // Exceptions.
-        if (isset($hash['exclusion'])) {
-            foreach ($hash['exclusion'] as $exception) {
-                if ($exception instanceof DateTime) {
-                    $this->exceptions[] = $exception->format('Ymd');
-                }
-            }
-        }
-
-        if (isset($hash['complete'])) {
-            foreach ($hash['complete'] as $completion) {
-                if ($exception instanceof DateTime) {
-                    $this->completions[] = $completion->format('Ymd');
-                }
-            }
-        }
-
-        return true;
-    }
-
-    /**
-     * Export this object into a Kolab hash.
-     *
-     * @return array  The recurrence hash.
-     */
-    public function toKolab()
-    {
-        if ($this->getRecurType() == self::RECUR_NONE) {
-            return array();
-        }
-
-        $day2number = array(
-            0 => 'sunday',
-            1 => 'monday',
-            2 => 'tuesday',
-            3 => 'wednesday',
-            4 => 'thursday',
-            5 => 'friday',
-            6 => 'saturday'
-        );
-        $month2number = array(
-            1 => 'january',
-            2 => 'february',
-            3 => 'march',
-            4 => 'april',
-            5 => 'may',
-            6 => 'june',
-            7 => 'july',
-            8 => 'august',
-            9 => 'september',
-            10 => 'october',
-            11 => 'november',
-            12 => 'december'
-        );
-
-        $hash = array('interval' => $this->getRecurInterval());
-        $start = $this->getRecurStart();
-
-        switch ($this->getRecurType()) {
-        case self::RECUR_DAILY:
-            $hash['cycle'] = 'daily';
-            break;
-
-        case self::RECUR_WEEKLY:
-            $hash['cycle'] = 'weekly';
-            $bits = array(
-                'monday' => Horde_Date::MASK_MONDAY,
-                'tuesday' => Horde_Date::MASK_TUESDAY,
-                'wednesday' => Horde_Date::MASK_WEDNESDAY,
-                'thursday' => Horde_Date::MASK_THURSDAY,
-                'friday' => Horde_Date::MASK_FRIDAY,
-                'saturday' => Horde_Date::MASK_SATURDAY,
-                'sunday' => Horde_Date::MASK_SUNDAY,
-            );
-            $days = array();
-            foreach ($bits as $name => $bit) {
-                if ($this->recurOnDay($bit)) {
-                    $days[] = $name;
-                }
-            }
-            $hash['day'] = $days;
-            break;
-
-        case self::RECUR_MONTHLY_DATE:
-            $hash['cycle'] = 'monthly';
-            $hash['type'] = 'daynumber';
-            $hash['daynumber'] = $start->mday;
-            break;
-
-        case self::RECUR_MONTHLY_WEEKDAY:
-            $hash['cycle'] = 'monthly';
-            $hash['type'] = 'weekday';
-            $hash['daynumber'] = $start->weekOfMonth();
-            $hash['day'] = array ($day2number[$start->dayOfWeek()]);
-            break;
-
-        case self::RECUR_YEARLY_DATE:
-            $hash['cycle'] = 'yearly';
-            $hash['type'] = 'monthday';
-            $hash['daynumber'] = $start->mday;
-            $hash['month'] = $month2number[$start->month];
-            break;
-
-        case self::RECUR_YEARLY_DAY:
-            $hash['cycle'] = 'yearly';
-            $hash['type'] = 'yearday';
-            $hash['daynumber'] = $start->dayOfYear();
-            break;
-
-        case self::RECUR_YEARLY_WEEKDAY:
-            $hash['cycle'] = 'yearly';
-            $hash['type'] = 'weekday';
-            $hash['daynumber'] = $start->weekOfMonth();
-            $hash['day'] = array ($day2number[$start->dayOfWeek()]);
-            $hash['month'] = $month2number[$start->month];
-        }
-
-        if ($this->hasRecurCount()) {
-            $hash['range-type'] = 'number';
-            $hash['range'] = $this->getRecurCount();
-        } elseif ($this->hasRecurEnd()) {
-            $date = $this->getRecurEnd();
-            $hash['range-type'] = 'date';
-            $hash['range'] = $date->toDateTime();
-        } else {
-            $hash['range-type'] = 'none';
-            $hash['range'] = '';
-        }
-
-        // Recurrence exceptions
-        $hash['exclusion'] = $hash['complete'] = array();
-        foreach ($this->exceptions as $exception) {
-            $hash['exclusion'][] = new DateTime($exception);
-        }
-        foreach ($this->completions as $completionexception) {
-            $hash['complete'][] = new DateTime($completionexception);
-        }
-
-        return $hash;
-    }
-
-    /**
-     * Returns a simple object suitable for json transport representing this
-     * object.
-     *
-     * Possible properties are:
-     * - t: type
-     * - i: interval
-     * - e: end date
-     * - c: count
-     * - d: data
-     * - co: completions
-     * - ex: exceptions
-     *
-     * @return object  A simple object.
-     */
-    public function toJson()
-    {
-        $json = new stdClass;
-        $json->t = $this->recurType;
-        $json->i = $this->recurInterval;
-        if ($this->hasRecurEnd()) {
-            $json->e = $this->recurEnd->toJson();
-        }
-        if ($this->recurCount) {
-            $json->c = $this->recurCount;
-        }
-        if ($this->recurData) {
-            $json->d = $this->recurData;
-        }
-        if ($this->completions) {
-            $json->co = $this->completions;
-        }
-        if ($this->exceptions) {
-            $json->ex = $this->exceptions;
-        }
-        return $json;
-    }
-
-}
diff --git a/plugins/libcalendaring/lib/libcalendaring_recurrence.php b/plugins/libcalendaring/lib/libcalendaring_recurrence.php
index b62ba42f..4aca2861 100644
--- a/plugins/libcalendaring/lib/libcalendaring_recurrence.php
+++ b/plugins/libcalendaring/lib/libcalendaring_recurrence.php
@@ -1,253 +1,278 @@
 <?php
 
+use Sabre\VObject\Recur\EventIterator;
+
 /**
- * Recurrence computation class for shared use
+ * Recurrence computation class for shared use.
  *
- * Uitility class to compute reccurrence dates from the given rules
+ * Uitility class to compute recurrence dates from the given rules.
  *
- * @author Thomas Bruederli <bruederli@kolabsys.com>
+ * @author Aleksander Machniak <machniak@apheleia-it.ch
  *
- * Copyright (C) 2012-2014, Kolab Systems AG <contact@kolabsys.com>
+ * Copyright (C) 2012-2022, Apheleia IT AG <contact@apheleia-it.ch>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 class libcalendaring_recurrence
 {
     protected $lib;
     protected $start;
-    protected $next;
     protected $engine;
     protected $recurrence;
     protected $dateonly = false;
-    protected $hour = 0;
+    protected $event;
+    protected $duration;
 
     /**
      * Default constructor
      *
-     * @param calendar The calendar plugin instance
+     * @param libcalendaring $lib   The libcalendaring plugin instance
+     * @param array          $event The event object to operate on
      */
-    function __construct($lib)
+    function __construct($lib, $event = null)
     {
-        // use Horde classes to compute recurring instances
-        // TODO: replace with something that has less than 6'000 lines of code
-        require_once(__DIR__ . '/Horde_Date_Recurrence.php');
+        $this->lib   = $lib;
+        $this->event = $event;
+
+        if (!empty($event)) {
+            if (!empty($event['start']) && is_object($event['start'])
+                && !empty($event['end']) && is_object($event['end'])
+            ) {
+                $this->duration = $event['start']->diff($event['end']);
+            }
+
+            $event['start']->_dateonly = !empty($event['allday']);
 
-        $this->lib = $lib;
+            $this->init($event['recurrence'], $event['start']);
+        }
     }
 
     /**
      * Initialize recurrence engine
      *
      * @param array    The recurrence properties
      * @param DateTime The recurrence start date
      */
-    public function init($recurrence, $start = null)
+    public function init($recurrence, $start)
     {
+        $this->start      = $start;
+        $this->dateonly   = !empty($start->_dateonly);
         $this->recurrence = $recurrence;
 
-        $this->engine = new Horde_Date_Recurrence($start);
-        $this->engine->fromRRule20(libcalendaring::to_rrule($recurrence));
+        $event = [
+            'uid' => '1',
+            'allday' => $this->dateonly,
+            'recurrence' => $recurrence,
+            'start' => $start,
+            // TODO: END/DURATION ???
+            // TODO: moved occurrences ???
+        ];
 
-        $this->set_start($start);
+        $vcalendar = new libcalendaring_vcalendar($this->lib->timezone);
 
-        if (!empty($recurrence['EXDATE'])) {
-            foreach ((array) $recurrence['EXDATE'] as $exdate) {
-                if ($exdate instanceof DateTimeInterface) {
-                    $this->engine->addException($exdate->format('Y'), $exdate->format('n'), $exdate->format('j'));
-                }
-            }
-        }
-        if (!empty($recurrence['RDATE'])) {
-            foreach ((array) $recurrence['RDATE'] as $rdate) {
-                if ($rdate instanceof DateTimeInterface) {
-                    $this->engine->addRDate($rdate->format('Y'), $rdate->format('n'), $rdate->format('j'));
-                }
-            }
-        }
+        $ve = $vcalendar->toSabreComponent($event);
+
+        $this->engine = new EventIterator($ve, null, $this->lib->timezone);
     }
 
     /**
-     * Setter for (new) recurrence start date
+     * Get date/time of the next occurence of this event, and push the iterator.
      *
-     * @param DateTime The recurrence start date
+     * @return DateTime|false object or False if recurrence ended
      */
-    public function set_start($start)
+    public function next_start()
     {
-        $this->start = $start;
-        $this->dateonly = !empty($start->_dateonly);
-        $this->next = new Horde_Date($start, $this->lib->timezone->getName());
-        $this->hour = $this->next->hour;
-        $this->engine->setRecurStart($this->next);
+        try {
+            $this->engine->next();
+            $current = $this->engine->getDtStart();
+        }
+        catch (Exception $e) {
+            // do nothing
+        }
+
+        return $current ? $this->toDateTime($current) : false;
     }
 
     /**
-     * Get date/time of the next occurence of this event
+     * Get the next recurring instance of this event
      *
-     * @return DateTime|false object or False if recurrence ended
+     * @return array|false Array with event properties or False if recurrence ended
      */
-    public function next()
+    public function next_instance()
     {
-        $time = false;
-        $after = clone $this->next;
-        $after->mday = $after->mday + 1;
-
-        if ($this->next && ($next = $this->engine->nextActiveRecurrence($after))) {
-            // avoid endless loops if recurrence computation fails
-            if (!$next->after($this->next)) {
-                return false;
-            }
+        if ($next_start = $this->next_start()) {
+            $next = $this->event;
+            $next['start'] = $next_start;
 
-            // fix time for all-day events
-            if ($this->dateonly) {
-                $next->hour = $this->hour;
-                $next->min = 0;
+            if ($this->duration) {
+                $next['end'] = clone $next_start;
+                $next['end']->add($this->duration);
             }
 
-            $this->next = $next;
+            $next['recurrence_date'] = clone $next_start;
+            $next['_instance'] = libcalendaring::recurrence_instance_identifier($next, !empty($this->event['allday']));
+
+            unset($next['_formatobj']);
 
-            $time = $this->toDateTime($next);
+            return $next;
         }
 
-        return $time;
+        return false;
     }
 
     /**
-     * Get the end date of the occurence of this recurrence cycle
+     * Get the date of the end of the last occurrence of this recurrence cycle
      *
-     * @return DateTime|bool End datetime of the last occurence or False if recurrence exceeds limit
+     * @return DateTime|false End datetime of the last occurrence or False if there's no end date
      */
     public function end()
     {
         // recurrence end date is given
-        if ($this->recurrence['UNTIL'] instanceof DateTimeInterface) {
+        if (isset($this->recurrence['UNTIL']) && $this->recurrence['UNTIL'] instanceof DateTimeInterface) {
             return $this->recurrence['UNTIL'];
         }
 
-        // take the last RDATE entry if set
-        if (is_array($this->recurrence['RDATE']) && !empty($this->recurrence['RDATE'])) {
-            $last = end($this->recurrence['RDATE']);
-            if ($last instanceof DateTimeInterface) {
-                return $last;
+        if (!$this->engine->isInfinite()) {
+            // run through all items till we reach the end
+            try {
+                foreach ($this->engine as $end) {
+                    // do nothing
+                }
             }
-        }
-
-        // run through all items till we reach the end
-        if ($this->recurrence['COUNT']) {
-            $last = $this->start;
-            $this->next = new Horde_Date($this->start, $this->lib->timezone->getName());
-            while (($next = $this->next()) && $c < 1000) {
-                $last = $next;
-                $c++;
+            catch (Exception $e) {
+                // do nothing
             }
         }
+        else if (isset($this->event['end']) && $this->event['end'] instanceof DateTimeInterface) {
+            // determine a reasonable end date if none given
+            $end = clone $this->event['end'];
+            $end->add(new DateInterval('P100Y'));
+        }
 
-        return $last;
+        return isset($end) ? $this->toDateTime($end, false) : false;
     }
 
     /**
      * Find date/time of the first occurrence (excluding start date)
+     *
+     * @return DateTime|null First occurrence
      */
     public function first_occurrence()
     {
-        $start      = clone $this->start;
-        $orig_start = clone $this->start;
-        $r          = $this->recurrence;
-        $interval   = !empty($r['INTERVAL']) ? intval($r['INTERVAL']) : 1;
-        $frequency  = isset($this->recurrence['FREQ']) ? $this->recurrence['FREQ'] : null;
+        $start    = clone $this->start;
+        $interval = $this->recurrence['INTERVAL'] ?? 1;
+        $freq     = $this->recurrence['FREQ'] ?? null;
 
-        switch ($frequency) {
+        switch ($freq) {
         case 'WEEKLY':
             if (empty($this->recurrence['BYDAY'])) {
                 return $start;
             }
 
             $start->sub(new DateInterval("P{$interval}W"));
             break;
 
         case 'MONTHLY':
             if (empty($this->recurrence['BYDAY']) && empty($this->recurrence['BYMONTHDAY'])) {
                 return $start;
             }
 
             $start->sub(new DateInterval("P{$interval}M"));
             break;
 
         case 'YEARLY':
             if (empty($this->recurrence['BYDAY']) && empty($this->recurrence['BYMONTH'])) {
                 return $start;
             }
 
             $start->sub(new DateInterval("P{$interval}Y"));
             break;
 
+        case 'DAILY':
+            if (!empty($this->recurrence['BYMONTH'])) {
+                break;
+            }
+
         default:
             return $start;
         }
 
-        $r = $this->recurrence;
-        $r['INTERVAL'] = $interval;
-        if (!empty($r['COUNT'])) {
+        $recurrence = $this->recurrence;
+
+        if (!empty($recurrence['COUNT'])) {
             // Increase count so we do not stop the loop to early
-            $r['COUNT'] += 100;
+            $recurrence['COUNT'] += 100;
         }
 
         // Create recurrence that starts in the past
-        $recurrence = new self($this->lib);
-        $recurrence->init($r, $start);
+        $self = new self($this->lib);
+        $self->init($recurrence, $start);
+
+        // TODO: This method does not work the same way as the kolab_date_recurrence based on
+        //       kolabcalendaring. I.e. if an event start date does not match the recurrence rule
+        //       it will be returned, kolab_date_recurrence will return the next occurrence in such a case
+        //       which is the intended result of this function.
+        //       See some commented out test cases in tests/RecurrenceTest.php
 
         // find the first occurrence
         $found = false;
-        while ($next = $recurrence->next()) {
+        while ($next = $self->next_start()) {
             $start = $next;
-            if ($next >= $orig_start) {
+            if ($next >= $this->start) {
                 $found = true;
                 break;
             }
         }
 
         if (!$found) {
-            rcube::raise_error(array(
-                'file' => __FILE__,
-                'line' => __LINE__,
-                'message' => sprintf("Failed to find a first occurrence. Start: %s, Recurrence: %s",
-                    $orig_start->format(DateTime::ISO8601), json_encode($r)),
-            ), true);
+            rcube::raise_error(
+                [
+                    'file' => __FILE__, 'line' => __LINE__,
+                    'message' => sprintf("Failed to find a first occurrence. Start: %s, Recurrence: %s",
+                        $this->start->format(DateTime::ISO8601), json_encode($recurrence)),
+                ],
+                true
+            );
 
             return null;
         }
 
-        $start = $this->toDateTime($start);
-
-        return $start;
+        return $this->toDateTime($start);
     }
 
-    private function toDateTime($date)
+    /**
+     * Convert any DateTime into libcalendaring_datetime
+     */
+    protected function toDateTime($date, $useStart = true)
     {
-        if ($date Instanceof Horde_Date) {
-            $date = $date->toDateTime();
-        }
-
         if ($date instanceof DateTimeInterface) {
             $date = libcalendaring_datetime::createFromFormat(
                 'Y-m-d\\TH:i:s',
                 $date->format('Y-m-d\\TH:i:s'),
-                $date->getTimezone()
+                // Sabre will loose timezone on all-day events, use the event start's timezone
+                $this->start->getTimezone()
             );
         }
 
         $date->_dateonly = $this->dateonly;
 
+        if ($useStart && $this->dateonly) {
+            // Sabre sets time to 00:00:00 for all-day events,
+            // let's copy the time from the event's start
+            $date->setTime((int) $this->start->format('H'), (int) $this->start->format('i'), (int) $this->start->format('s'));
+        }
+
         return $date;
     }
 }
diff --git a/plugins/libcalendaring/lib/libcalendaring_vcalendar.php b/plugins/libcalendaring/lib/libcalendaring_vcalendar.php
index c88fe2cc..b801981b 100644
--- a/plugins/libcalendaring/lib/libcalendaring_vcalendar.php
+++ b/plugins/libcalendaring/lib/libcalendaring_vcalendar.php
@@ -1,1536 +1,1556 @@
 <?php
 
 /**
  * iCalendar functions for the libcalendaring plugin
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2013-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 use \Sabre\VObject;
 use \Sabre\VObject\DateTimeParser;
 
 /**
  * Class to parse and build vCalendar (iCalendar) files
  *
  * Uses the Sabre VObject library, version 3.x.
  *
  */
 class libcalendaring_vcalendar implements Iterator
 {
     private $timezone;
     private $attach_uri = null;
     private $prodid = '-//Roundcube libcalendaring//Sabre//Sabre VObject//EN';
     private $type_component_map = array('event' => 'VEVENT', 'task' => 'VTODO');
     private $attendee_keymap = array(
         'name'   => 'CN',
         'status' => 'PARTSTAT',
         'role'   => 'ROLE',
         'cutype' => 'CUTYPE',
         'rsvp'   => 'RSVP',
         'delegated-from'  => 'DELEGATED-FROM',
         'delegated-to'    => 'DELEGATED-TO',
         'schedule-status' => 'SCHEDULE-STATUS',
         'schedule-agent'  => 'SCHEDULE-AGENT',
         'sent-by'         => 'SENT-BY',
     );
     private $organizer_keymap = array(
         'name'            => 'CN',
         'schedule-status' => 'SCHEDULE-STATUS',
         'schedule-agent'  => 'SCHEDULE-AGENT',
         'sent-by'         => 'SENT-BY',
     );
     private $iteratorkey = 0;
     private $charset;
     private $forward_exceptions;
     private $vhead;
     private $fp;
     private $vtimezones = array();
 
     public $method;
     public $agent = '';
     public $objects = array();
     public $freebusy = array();
 
 
     /**
      * Default constructor
      */
     function __construct($tz = null)
     {
         $this->timezone = $tz;
         $this->prodid = '-//Roundcube libcalendaring ' . RCUBE_VERSION . '//Sabre//Sabre VObject ' . VObject\Version::VERSION . '//EN';
     }
 
     /**
      * Setter for timezone information
      */
     public function set_timezone($tz)
     {
         $this->timezone = $tz;
     }
 
     /**
      * Setter for URI template for attachment links
      */
     public function set_attach_uri($uri)
     {
         $this->attach_uri = $uri;
     }
 
     /**
      * Setter for a custom PRODID attribute
      */
     public function set_prodid($prodid)
     {
         $this->prodid = $prodid;
     }
 
     /**
      * Setter for a user-agent string to tweak input/output accordingly
      */
     public function set_agent($agent)
     {
         $this->agent = $agent;
     }
 
     /**
      * Free resources by clearing member vars
      */
     public function reset()
     {
         $this->vhead = '';
         $this->method = '';
         $this->objects = array();
         $this->freebusy = array();
         $this->vtimezones = array();
         $this->iteratorkey = 0;
 
         if ($this->fp) {
             fclose($this->fp);
             $this->fp = null;
         }
     }
 
     /**
     * Import events from iCalendar format
     *
     * @param  string vCalendar input
     * @param  string Input charset (from envelope)
     * @param  boolean True if parsing exceptions should be forwarded to the caller
     * @return array List of events extracted from the input
     */
     public function import($vcal, $charset = 'UTF-8', $forward_exceptions = false, $memcheck = true)
     {
         // TODO: convert charset to UTF-8 if other
 
         try {
             // estimate the memory usage and try to avoid fatal errors when allowed memory gets exhausted
             if ($memcheck) {
                 $count = substr_count($vcal, 'BEGIN:VEVENT') + substr_count($vcal, 'BEGIN:VTODO');
                 $expected_memory = $count * 70*1024;  // assume ~ 70K per event (empirically determined)
 
                 if (!rcube_utils::mem_check($expected_memory)) {
                     throw new Exception("iCal file too big");
                 }
             }
 
             $vobject = VObject\Reader::read($vcal, VObject\Reader::OPTION_FORGIVING | VObject\Reader::OPTION_IGNORE_INVALID_LINES);
             if ($vobject)
                 return $this->import_from_vobject($vobject);
         }
         catch (Exception $e) {
             if ($forward_exceptions) {
                 throw $e;
             }
             else {
                 rcube::raise_error(array(
                     'code' => 600, 'type' => 'php',
                     'file' => __FILE__, 'line' => __LINE__,
                     'message' => "iCal data parse error: " . $e->getMessage()),
                     true, false);
             }
         }
 
         return array();
     }
 
     /**
     * Read iCalendar events from a file
     *
     * @param  string File path to read from
     * @param  string Input charset (from envelope)
     * @param  boolean True if parsing exceptions should be forwarded to the caller
     * @return array List of events extracted from the file
     */
     public function import_from_file($filepath, $charset = 'UTF-8', $forward_exceptions = false)
     {
         if ($this->fopen($filepath, $charset, $forward_exceptions)) {
             while ($this->_parse_next(false)) {
                 // nop
             }
 
             fclose($this->fp);
             $this->fp = null;
         }
 
         return $this->objects;
     }
 
     /**
      * Open a file to read iCalendar events sequentially
      *
      * @param  string File path to read from
      * @param  string Input charset (from envelope)
      * @param  boolean True if parsing exceptions should be forwarded to the caller
      * @return boolean True if file contents are considered valid
      */
     public function fopen($filepath, $charset = 'UTF-8', $forward_exceptions = false)
     {
         $this->reset();
 
         // just to be sure...
         @ini_set('auto_detect_line_endings', true);
 
         $this->charset = $charset;
         $this->forward_exceptions = $forward_exceptions;
         $this->fp = fopen($filepath, 'r');
 
         // check file content first
         $begin = fread($this->fp, 1024);
         if (!preg_match('/BEGIN:VCALENDAR/i', $begin)) {
             return false;
         }
 
         fseek($this->fp, 0);
         return $this->_parse_next();
     }
 
     /**
      * Parse the next event/todo/freebusy object from the input file
      */
     private function _parse_next($reset = true)
     {
         if ($reset) {
             $this->iteratorkey = 0;
             $this->objects = array();
             $this->freebusy = array();
         }
 
         $next = $this->_next_component();
         $buffer = $next;
 
         // load the next component(s) too, as they could contain recurrence exceptions
         while (preg_match('/(RRULE|RECURRENCE-ID)[:;]/i', $next)) {
             $next = $this->_next_component();
             $buffer .= $next;
         }
 
         // parse the vevent block surrounded with the vcalendar heading
         if (strlen($buffer) && preg_match('/BEGIN:(VEVENT|VTODO|VFREEBUSY)/i', $buffer)) {
             try {
                 $this->import($this->vhead . $buffer . "END:VCALENDAR", $this->charset, true, false);
             }
             catch (Exception $e) {
                 if ($this->forward_exceptions) {
                     throw new VObject\ParseException($e->getMessage() . " in\n" . $buffer);
                 }
                 else {
                     // write the failing section to error log
                     rcube::raise_error(array(
                         'code' => 600, 'type' => 'php',
                         'file' => __FILE__, 'line' => __LINE__,
                         'message' => $e->getMessage() . " in\n" . $buffer),
                         true, false);
                 }
 
                 // advance to next
                 return $this->_parse_next($reset);
             }
 
             return count($this->objects) > 0;
         }
 
         return false;
     }
 
     /**
      * Helper method to read the next calendar component from the file
      */
     private function _next_component()
     {
         $buffer = '';
         $vcalendar_head = false;
         while (($line = fgets($this->fp, 1024)) !== false) {
             // ignore END:VCALENDAR lines
             if (preg_match('/END:VCALENDAR/i', $line)) {
                 continue;
             }
             // read vcalendar header (with timezone defintion)
             if (preg_match('/BEGIN:VCALENDAR/i', $line)) {
                 $this->vhead = '';
                 $vcalendar_head = true;
             }
 
             // end of VCALENDAR header part
             if ($vcalendar_head && preg_match('/BEGIN:(VEVENT|VTODO|VFREEBUSY)/i', $line)) {
                 $vcalendar_head = false;
             }
 
             if ($vcalendar_head) {
                 $this->vhead .= $line;
             }
             else {
                 $buffer .= $line;
                 if (preg_match('/END:(VEVENT|VTODO|VFREEBUSY)/i', $line)) {
                     break;
                 }
             }
         }
 
         return $buffer;
     }
 
     /**
      * Import objects from an already parsed Sabre\VObject\Component object
      *
      * @param object Sabre\VObject\Component to read from
      * @return array List of events extracted from the file
      */
     public function import_from_vobject($vobject)
     {
         $seen = array();
         $exceptions = array();
 
         if ($vobject->name == 'VCALENDAR') {
             $this->method = strval($vobject->METHOD);
             $this->agent  = strval($vobject->PRODID);
 
             foreach ($vobject->getComponents() as $ve) {
                 if ($ve->name == 'VEVENT' || $ve->name == 'VTODO') {
                     // convert to hash array representation
                     $object = $this->_to_array($ve);
 
                     // temporarily store this as exception
                     if (!empty($object['recurrence_date'])) {
                         $exceptions[] = $object;
                     }
                     else if (empty($seen[$object['uid']])) {
                         $seen[$object['uid']] = true;
                         $this->objects[] = $object;
                     }
                 }
                 else if ($ve->name == 'VFREEBUSY') {
                     $this->objects[] = $this->_parse_freebusy($ve);
                 }
             }
 
             // add exceptions to the according master events
             foreach ($exceptions as $exception) {
                 $uid = $exception['uid'];
 
                 // make this exception the master
                 if (empty($seen[$uid])) {
                     $seen[$uid] = true;
                     $this->objects[] = $exception;
                 }
                 else {
                     foreach ($this->objects as $i => $object) {
                         // add as exception to existing entry with a matching UID
                         if ($object['uid'] == $uid) {
                             $this->objects[$i]['exceptions'][] = $exception;
 
                             if (!empty($object['recurrence'])) {
                                 $this->objects[$i]['recurrence']['EXCEPTIONS'] = &$this->objects[$i]['exceptions'];
                             }
                             break;
                         }
                     }
                 }
             }
         }
 
         return $this->objects;
     }
 
     /**
      * Getter for free-busy periods
      */
     public function get_busy_periods()
     {
         $out = array();
         foreach ((array)$this->freebusy['periods'] as $period) {
             if ($period[2] != 'FREE') {
                 $out[] = $period;
             }
         }
 
         return $out;
     }
 
     /**
      * Helper method to determine whether the connected client is an Apple device
      */
     private function is_apple()
     {
         return stripos($this->agent, 'Apple') !== false
             || stripos($this->agent, 'Mac OS X') !== false
             || stripos($this->agent, 'iOS/') !== false;
     }
 
     /**
      * Convert the given VEvent object to a libkolab compatible array representation
      *
      * @param object Vevent object to convert
      * @return array Hash array with object properties
      */
     private function _to_array($ve)
     {
         $event = array(
             'uid'     => self::convert_string($ve->UID),
             'title'   => self::convert_string($ve->SUMMARY),
             '_type'   => $ve->name == 'VTODO' ? 'task' : 'event',
             // set defaults
             'priority' => 0,
             'attendees' => array(),
             'x-custom' => array(),
         );
 
         // Catch possible exceptions when date is invalid (Bug #2144)
         // We can skip these fields, they aren't critical
         foreach (array('CREATED' => 'created', 'LAST-MODIFIED' => 'changed', 'DTSTAMP' => 'changed') as $attr => $field) {
             try {
                 if (empty($event[$field]) && !empty($ve->{$attr})) {
                     $event[$field] = $ve->{$attr}->getDateTime();
                 }
             } catch (Exception $e) {}
         }
 
         // map other attributes to internal fields
         foreach ($ve->children() as $prop) {
             if (!($prop instanceof VObject\Property))
                 continue;
 
             $value = strval($prop);
 
             switch ($prop->name) {
             case 'DTSTART':
             case 'DTEND':
             case 'DUE':
                 $propmap = array('DTSTART' => 'start', 'DTEND' => 'end', 'DUE' => 'due');
                 $event[$propmap[$prop->name]] = self::convert_datetime($prop);
                 break;
 
             case 'TRANSP':
                 $event['free_busy'] = strval($prop) == 'TRANSPARENT' ? 'free' : 'busy';
                 break;
 
             case 'STATUS':
                 if ($value == 'TENTATIVE')
                     $event['free_busy'] = 'tentative';
                 else if ($value == 'CANCELLED')
                     $event['cancelled'] = true;
                 else if ($value == 'COMPLETED')
                     $event['complete'] = 100;
 
                 $event['status'] = $value;
                 break;
 
             case 'COMPLETED':
                 if (self::convert_datetime($prop)) {
                     $event['status'] = 'COMPLETED';
                     $event['complete'] = 100;
                 }
                 break;
 
             case 'PRIORITY':
                 if (is_numeric($value))
                     $event['priority'] = $value;
                 break;
 
             case 'RRULE':
                 $params = !empty($event['recurrence']) && is_array($event['recurrence']) ? $event['recurrence'] : array();
                 // parse recurrence rule attributes
                 foreach ($prop->getParts() as $k => $v) {
                     $params[strtoupper($k)] = is_array($v) ? implode(',', $v) : $v;
                 }
                 if (!empty($params['UNTIL'])) {
                     $params['UNTIL'] = date_create($params['UNTIL']);
                 }
                 if (empty($params['INTERVAL'])) {
                     $params['INTERVAL'] = 1;
                 }
 
                 $event['recurrence'] = array_filter($params);
                 break;
 
             case 'EXDATE':
                 if (!empty($value)) {
                     $exdates = array_map(function($_) { return is_array($_) ? $_[0] : $_; }, self::convert_datetime($prop, true));
                     if (!empty($event['recurrence']['EXDATE'])) {
                         $event['recurrence']['EXDATE'] = array_merge($event['recurrence']['EXDATE'], $exdates);
                     }
                     else {
                         $event['recurrence']['EXDATE'] = $exdates;
                     }
                 }
                 break;
 
             case 'RDATE':
                 if (!empty($value)) {
                     $rdates = array_map(function($_) { return is_array($_) ? $_[0] : $_; }, self::convert_datetime($prop, true));
                     if (!empty($event['recurrence']['RDATE'])) {
                         $event['recurrence']['RDATE'] = array_merge($event['recurrence']['RDATE'], $rdates);
                     }
                     else {
                         $event['recurrence']['RDATE'] = $rdates;
                     }
                 }
                 break;
 
             case 'RECURRENCE-ID':
                 $event['recurrence_date'] = self::convert_datetime($prop);
                 if ($prop->offsetGet('RANGE') == 'THISANDFUTURE' || $prop->offsetGet('THISANDFUTURE') !== null) {
                     $event['thisandfuture'] = true;
                 }
                 break;
 
             case 'RELATED-TO':
                 $reltype = $prop->offsetGet('RELTYPE');
                 if ($reltype == 'PARENT' || $reltype === null) {
                     $event['parent_id'] = $value;
                 }
                 break;
 
             case 'SEQUENCE':
                 $event['sequence'] = intval($value);
                 break;
 
             case 'PERCENT-COMPLETE':
                 $event['complete'] = intval($value);
                 break;
 
             case 'LOCATION':
             case 'DESCRIPTION':
             case 'URL':
             case 'COMMENT':
                 $event[strtolower($prop->name)] = self::convert_string($prop);
                 break;
 
             case 'CATEGORY':
             case 'CATEGORIES':
                 if (!empty($event['categories'])) {
                     $event['categories'] = array_merge((array) $event['categories'], $prop->getParts());
                 }
                 else {
                     $event['categories'] = $prop->getParts();
                 }
                 break;
 
             case 'X-MICROSOFT-CDO-BUSYSTATUS':
                 if ($value == 'OOF') {
                     $event['free_busy'] = 'outofoffice';
                 }
                 else if (in_array($value, array('FREE', 'BUSY', 'TENTATIVE'))) {
                     $event['free_busy'] = strtolower($value);
                 }
                 break;
 
             case 'ATTENDEE':
             case 'ORGANIZER':
                 $params = array('RSVP' => false);
                 foreach ($prop->parameters() as $pname => $pvalue) {
                     switch ($pname) {
                         case 'RSVP': $params[$pname] = strtolower($pvalue) == 'true'; break;
                         case 'CN':   $params[$pname] = self::unescape($pvalue); break;
                         default:     $params[$pname] = strval($pvalue); break;
                     }
                 }
                 $attendee = self::map_keys($params, array_flip($this->attendee_keymap));
                 $attendee['email'] = preg_replace('!^mailto:!i', '', $value);
 
                 if ($prop->name == 'ORGANIZER') {
                     $attendee['role'] = 'ORGANIZER';
                     $attendee['status'] = 'ACCEPTED';
                     $event['organizer'] = $attendee;
 
                     if (array_key_exists('schedule-agent', $attendee)) {
                         $schedule_agent = $attendee['schedule-agent'];
                     }
                 }
                 else if (empty($event['organizer']) || $attendee['email'] != $event['organizer']['email']) {
                     $event['attendees'][] = $attendee;
                 }
                 break;
 
             case 'ATTACH':
                 $params = self::parameters_array($prop);
                 if (substr($value, 0, 4) == 'http' && !strpos($value, ':attachment:')) {
                     $event['links'][] = $value;
                 }
                 else if (strlen($value) && strtoupper($params['VALUE']) == 'BINARY') {
                     $attachment = self::map_keys($params, array('FMTTYPE' => 'mimetype', 'X-LABEL' => 'name', 'X-APPLE-FILENAME' => 'name'));
                     $attachment['data'] = $value;
                     $attachment['size'] = strlen($value);
                     $event['attachments'][] = $attachment;
                 }
                 break;
 
             default:
                 if (substr($prop->name, 0, 2) == 'X-')
                     $event['x-custom'][] = array($prop->name, strval($value));
                 break;
             }
         }
 
         // check DURATION property if no end date is set
         if (empty($event['end']) && $ve->DURATION) {
             try {
                 $duration = new DateInterval(strval($ve->DURATION));
                 $end = clone $event['start'];
                 $end->add($duration);
                 $event['end'] = $end;
             }
             catch (\Exception $e) {
                 trigger_error(strval($e), E_USER_WARNING);
             }
         }
 
         // validate event dates
         if ($event['_type'] == 'event') {
             $event['allday'] = !empty($event['start']->_dateonly);
 
             // events may lack the DTEND property, set it to DTSTART (RFC5545 3.6.1)
             if (empty($event['end'])) {
                 $event['end'] = clone $event['start'];
             }
             // shift end-date by one day (except Thunderbird)
             else if ($event['allday'] && is_object($event['end'])) {
                 $event['end']->sub(new \DateInterval('PT23H'));
             }
 
             // sanity-check and fix end date
             if (!empty($event['end']) && $event['end'] < $event['start']) {
                 $event['end'] = clone $event['start'];
             }
         }
 
         // make organizer part of the attendees list for compatibility reasons
         if (!empty($event['organizer']) && is_array($event['attendees']) && $event['_type'] == 'event') {
             array_unshift($event['attendees'], $event['organizer']);
         }
 
         // find alarms
         foreach ($ve->select('VALARM') as $valarm) {
             $action  = 'DISPLAY';
             $trigger = null;
             $alarm   = array();
 
             foreach ($valarm->children() as $prop) {
                 $value = strval($prop);
 
                 switch ($prop->name) {
                 case 'TRIGGER':
                     foreach ($prop->parameters as $param) {
                         if ($param->name == 'VALUE' && $param->getValue() == 'DATE-TIME') {
                             $trigger = '@' . $prop->getDateTime()->format('U');
                             $alarm['trigger'] = $prop->getDateTime();
                         }
                         else if ($param->name == 'RELATED') {
                             $alarm['related'] = $param->getValue();
                         }
                     }
                     if (!$trigger && ($values = libcalendaring::parse_alarm_value($value))) {
                         $trigger = $values[2];
                     }
 
                     if (empty($alarm['trigger'])) {
                         $alarm['trigger'] = rtrim(preg_replace('/([A-Z])0[WDHMS]/', '\\1', $value), 'T');
                         // if all 0-values have been stripped, assume 'at time'
                         if ($alarm['trigger'] == 'P') {
                             $alarm['trigger'] = 'PT0S';
                         }
                     }
                     break;
 
                 case 'ACTION':
                     $action = $alarm['action'] = strtoupper($value);
                     break;
 
                 case 'SUMMARY':
                 case 'DESCRIPTION':
                 case 'DURATION':
                     $alarm[strtolower($prop->name)] = self::convert_string($prop);
                     break;
 
                 case 'REPEAT':
                     $alarm['repeat'] = intval($value);
                     break;
 
                 case 'ATTENDEE':
                     $alarm['attendees'][] = preg_replace('!^mailto:!i', '', $value);
                     break;
 
                 case 'ATTACH':
                     $params = self::parameters_array($prop);
                     if (strlen($value) && (preg_match('/^[a-z]+:/', $value) || strtoupper($params['VALUE']) == 'URI')) {
                         // we only support URI-type of attachments here
                         $alarm['uri'] = $value;
                     }
                     break;
                 }
             }
 
             if ($action != 'NONE') {
                 // store first alarm in legacy property
                 if ($trigger && empty($event['alarms'])) {
                     $event['alarms'] = $trigger . ':' . $action;
                 }
 
                 if (!empty($alarm['trigger'])) {
                     $event['valarms'][] = $alarm;
                 }
             }
         }
 
         // assign current timezone to event start/end
         if (!empty($event['start']) && $event['start'] instanceof DateTimeInterface) {
             $this->_apply_timezone($event['start']);
         }
         else {
             unset($event['start']);
         }
 
         if (!empty($event['end']) && $event['end'] instanceof DateTimeInterface) {
             $this->_apply_timezone($event['end']);
         }
         else {
             unset($event['end']);
         }
 
         // some iTip CANCEL messages only contain the start date
         if (empty($event['end']) && !empty($event['start']) && $this->method == 'CANCEL') {
             $event['end'] = clone $event['start'];
         }
 
         // T2531: Remember SCHEDULE-AGENT in custom property to properly
         // support event updates via CalDAV when SCHEDULE-AGENT=CLIENT is used
         if (isset($schedule_agent)) {
             $event['x-custom'][] = array('SCHEDULE-AGENT', $schedule_agent);
         }
 
         // minimal validation
         if (empty($event['uid']) || ($event['_type'] == 'event' && empty($event['start']) != empty($event['end']))) {
             throw new VObject\ParseException('Object validation failed: missing mandatory object properties');
         }
 
         return $event;
     }
 
     /**
      * Apply user timezone to DateTime object
      */
     private function _apply_timezone(&$date)
     {
         if (empty($this->timezone)) {
             return;
         }
 
         // For date-only we'll keep the date and time intact
         if (!empty($date->_dateonly)) {
             $dt = new libcalendaring_datetime(null, $this->timezone);
             $dt->setDate($date->format('Y'), $date->format('n'), $date->format('j'));
             $dt->setTime($date->format('G'), $date->format('i'), 0);
             $date = $dt;
         }
         else {
             $date->setTimezone($this->timezone);
         }
     }
 
     /**
      * Parse the given vfreebusy component into an array representation
      */
     private function _parse_freebusy($ve)
     {
         $this->freebusy = array('_type' => 'freebusy', 'periods' => array());
         $seen = array();
 
         foreach ($ve->children() as $prop) {
             if (!($prop instanceof VObject\Property))
                 continue;
 
             $value = strval($prop);
 
             switch ($prop->name) {
             case 'CREATED':
             case 'LAST-MODIFIED':
             case 'DTSTAMP':
             case 'DTSTART':
             case 'DTEND':
                 $propmap = array(
                     'DTSTART' => 'start',
                     'DTEND' => 'end',
                     'CREATED' => 'created',
                     'LAST-MODIFIED' => 'changed',
                     'DTSTAMP' => 'changed'
                 );
                 $this->freebusy[$propmap[$prop->name]] = self::convert_datetime($prop);
                 break;
 
             case 'ORGANIZER':
                 $this->freebusy['organizer'] = preg_replace('!^mailto:!i', '', $value);
                 break;
 
             case 'FREEBUSY':
                 // The freebusy component can hold more than 1 value, separated by commas.
                 $periods = explode(',', $value);
                 $fbtype = strval($prop['FBTYPE']) ?: 'BUSY';
 
                 // skip dupes
                 if (!empty($seen[$value.':'.$fbtype])) {
                     break;
                 }
 
                 $seen[$value.':'.$fbtype] = true;
 
                 foreach ($periods as $period) {
                     // Every period is formatted as [start]/[end]. The start is an
                     // absolute UTC time, the end may be an absolute UTC time, or
                     // duration (relative) value.
                     list($busyStart, $busyEnd) = explode('/', $period);
 
                     $busyStart = DateTimeParser::parse($busyStart);
                     $busyEnd = DateTimeParser::parse($busyEnd);
                     if ($busyEnd instanceof \DateInterval) {
                         $tmp = clone $busyStart;
                         $tmp->add($busyEnd);
                         $busyEnd = $tmp;
                     }
 
                     if ($busyEnd && $busyEnd > $busyStart)
                         $this->freebusy['periods'][] = array($busyStart, $busyEnd, $fbtype);
                 }
                 break;
 
             case 'COMMENT':
                 $this->freebusy['comment'] = $value;
             }
         }
 
         return $this->freebusy;
     }
 
     /**
      *
      */
     public static function convert_string($prop)
     {
         return strval($prop);
     }
 
     /**
      *
      */
     public static function unescape($prop)
     {
         return str_replace('\,', ',', strval($prop));
     }
 
     /**
      * Helper method to correctly interpret an all-day date value
      */
     public static function convert_datetime($prop, $as_array = false)
     {
         if (empty($prop)) {
             return $as_array ? [] : null;
         }
 
         if ($prop instanceof VObject\Property\ICalendar\DateTime) {
             if (count($prop->getDateTimes()) > 1) {
                 $dt = [];
                 $dateonly = !$prop->hasTime();
 
                 foreach ($prop->getDateTimes() as $item) {
                     $item = libcalendaring_datetime::createFromImmutable($item);
                     $item->_dateonly = $dateonly;
                     $dt[] = $item;
                 }
             }
             else {
                 $dt = libcalendaring_datetime::createFromImmutable($prop->getDateTime());
                 if (!$prop->hasTime()) {
                     $dt->_dateonly = true;
                 }
             }
         }
         else if ($prop instanceof VObject\Property\ICalendar\Period) {
             $dt = [];
             foreach ($prop->getParts() as $val) {
                 try {
                     list($start, $end) = explode('/', $val);
                     $start = DateTimeParser::parseDateTime($start);
 
                     // This is a duration value.
                     if ($end[0] === 'P') {
                         $dur = DateTimeParser::parseDuration($end);
                         $end = clone $start;
                         $end->add($dur);
                     }
                     else {
                         $end = DateTimeParser::parseDateTime($end);
                     }
 
                     $dt[] = [libcalendaring_datetime::createFromImmutable($start), libcalendaring_datetime::createFromImmutable($end)];
                 }
                 catch (Exception $e) {
                     // ignore single date parse errors
                 }
             }
         }
         else if ($prop instanceof \DateTimeInterface) {
             $dt = libcalendaring_datetime::createFromImmutable($prop);
         }
 
         // force return value to array if requested
         if ($as_array && !is_array($dt)) {
             $dt = empty($dt) ? [] : [$dt];
         }
 
         return $dt;
     }
 
 
     /**
      * Create a Sabre\VObject\Property instance from a PHP DateTime object
      *
      * @param object  VObject\Document parent node to create property for
      * @param string  Property name
      * @param object  DateTime
      * @param boolean Set as UTC date
      * @param boolean Set as VALUE=DATE property
      */
     public function datetime_prop($cal, $name, $dt, $utc = false, $dateonly = null, $set_type = false)
     {
         if ($utc) {
             $dt->setTimeZone(new \DateTimeZone('UTC'));
             $is_utc = true;
         }
         else {
             $is_utc = ($tz = $dt->getTimezone()) && in_array($tz->getName(), array('UTC','GMT','Z'));
         }
         $is_dateonly = $dateonly === null ? !empty($dt->_dateonly) : (bool) $dateonly;
         $vdt = $cal->createProperty($name, $dt, null, $is_dateonly ? 'DATE' : 'DATE-TIME');
 
         if ($is_dateonly) {
             $vdt['VALUE'] = 'DATE';
         }
         else if ($set_type) {
             $vdt['VALUE'] = 'DATE-TIME';
         }
 
         // register timezone for VTIMEZONE block
         if (!$is_utc && !$dateonly && $tz && ($tzname = $tz->getName())) {
             $ts = $dt->format('U');
             if (!empty($this->vtimezones[$tzname])) {
                 $this->vtimezones[$tzname][0] = min($this->vtimezones[$tzname][0], $ts);
                 $this->vtimezones[$tzname][1] = max($this->vtimezones[$tzname][1], $ts);
             }
             else {
                 $this->vtimezones[$tzname] = array($ts, $ts);
             }
         }
 
         return $vdt;
     }
 
     /**
      * Copy values from one hash array to another using a key-map
      */
     public static function map_keys($values, $map)
     {
         $out = array();
         foreach ($map as $from => $to) {
             if (isset($values[$from]))
                 $out[$to] = is_array($values[$from]) ? join(',', $values[$from]) : $values[$from];
         }
         return $out;
     }
 
     /**
      *
      */
     private static function parameters_array($prop)
     {
         $params = array();
         foreach ($prop->parameters() as $name => $value) {
             $params[strtoupper($name)] = strval($value);
         }
         return $params;
     }
 
 
     /**
      * Export events to iCalendar format
      *
      * @param  array   Events as array
      * @param  string  VCalendar method to advertise
      * @param  boolean Directly send data to stdout instead of returning
      * @param  callable Callback function to fetch attachment contents, false if no attachment export
      * @param  boolean Add VTIMEZONE block with timezone definitions for the included events
      * @return string  Events in iCalendar format (http://tools.ietf.org/html/rfc5545)
      */
     public function export($objects, $method = null, $write = false, $get_attachment = false, $with_timezones = true)
     {
         $this->method = $method;
 
         // encapsulate in VCALENDAR container
         $vcal = new VObject\Component\VCalendar();
         $vcal->VERSION = '2.0';
         $vcal->PRODID = $this->prodid;
         $vcal->CALSCALE = 'GREGORIAN';
 
         if (!empty($method)) {
             $vcal->METHOD = $method;
         }
 
         // write vcalendar header
         if ($write) {
             echo preg_replace('/END:VCALENDAR[\r\n]*$/m', '', $vcal->serialize());
         }
 
         foreach ($objects as $object) {
             $this->_to_ical($object, !$write?$vcal:false, $get_attachment);
         }
 
         // include timezone information
         if ($with_timezones || !empty($method)) {
             foreach ($this->vtimezones as $tzid => $range) {
                 $vt = self::get_vtimezone($tzid, $range[0], $range[1], $vcal);
                 if (empty($vt)) {
                     continue;  // no timezone information found
                 }
 
                 if ($write) {
                     echo $vt->serialize();
                 }
                 else {
                     $vcal->add($vt);
                 }
             }
         }
 
         if ($write) {
             echo "END:VCALENDAR\r\n";
             return true;
         }
         else {
             return $vcal->serialize();
         }
     }
 
+    /**
+     * Converts internal event representation to Sabre component
+     *
+     * @param  array    Event
+     * @param  callable Callback function to fetch attachment contents, false if no attachment export
+     *
+     * @return Sabre\VObject\Component\VEvent Sabre component
+     */
+    public function toSabreComponent($object, $get_attachment = false)
+    {
+        $vcal = new VObject\Component\VCalendar();
+
+        $this->_to_ical($object, $vcal, $get_attachment);
+
+        return $vcal->getBaseComponent();
+    }
+
     /**
      * Build a valid iCal format block from the given event
      *
      * @param  array    Hash array with event/task properties from libkolab
      * @param  object   VCalendar object to append event to or false for directly sending data to stdout
      * @param  callable Callback function to fetch attachment contents, false if no attachment export
      * @param  object   RECURRENCE-ID property when serializing a recurrence exception
      */
     private function _to_ical($event, $vcal, $get_attachment, $recurrence_id = null)
     {
         $type = !empty($event['_type']) ? $event['_type'] : 'event';
 
         $cal = $vcal ?: new VObject\Component\VCalendar();
         $ve = $cal->create($this->type_component_map[$type]);
         $ve->UID = $event['uid'];
 
         // set DTSTAMP according to RFC 5545, 3.8.7.2.
         $dtstamp = !empty($event['changed']) && empty($this->method) ? $event['changed'] : new DateTime('now', new \DateTimeZone('UTC'));
         $ve->DTSTAMP = $this->datetime_prop($cal, 'DTSTAMP', $dtstamp, true);
 
         // all-day events end the next day
         if (!empty($event['allday']) && !empty($event['end'])) {
             $event['end'] = clone $event['end'];
             $event['end']->add(new \DateInterval('P1D'));
             $event['end']->_dateonly = true;
         }
         if (!empty($event['created'])) {
             $ve->add($this->datetime_prop($cal, 'CREATED', $event['created'], true));
         }
         if (!empty($event['changed'])) {
             $ve->add($this->datetime_prop($cal, 'LAST-MODIFIED', $event['changed'], true));
         }
         if (!empty($event['start'])) {
             $ve->add($this->datetime_prop($cal, 'DTSTART', $event['start'], false, !empty($event['allday'])));
         }
         if (!empty($event['end'])) {
             $ve->add($this->datetime_prop($cal, 'DTEND', $event['end'], false, !empty($event['allday'])));
         }
         if (!empty($event['due'])) {
             $ve->add($this->datetime_prop($cal, 'DUE', $event['due'], false));
         }
 
         // we're exporting a recurrence instance only
         if (!$recurrence_id && !empty($event['recurrence_date']) && $event['recurrence_date'] instanceof DateTimeInterface) {
             $recurrence_id = $this->datetime_prop($cal, 'RECURRENCE-ID', $event['recurrence_date'], false, !empty($event['allday']));
             if (!empty($event['thisandfuture'])) {
                 $recurrence_id->add('RANGE', 'THISANDFUTURE');
             }
         }
 
         if ($recurrence_id) {
             $ve->add($recurrence_id);
         }
 
-        $ve->add('SUMMARY', $event['title']);
+        if (!empty($event['title'])) {
+            $ve->add('SUMMARY', $event['title']);
+        }
 
         if (!empty($event['location'])) {
             $ve->add($this->is_apple() ? new vobject_location_property($cal, 'LOCATION', $event['location']) : $cal->create('LOCATION', $event['location']));
         }
+
         if (!empty($event['description'])) {
             $ve->add('DESCRIPTION', strtr($event['description'], array("\r\n" => "\n", "\r" => "\n"))); // normalize line endings
         }
 
         if (isset($event['sequence'])) {
             $ve->add('SEQUENCE', $event['sequence']);
         }
 
         if (!empty($event['recurrence']) && !$recurrence_id) {
             $exdates = $rdates = null;
             if (isset($event['recurrence']['EXDATE'])) {
                 $exdates = $event['recurrence']['EXDATE'];
                 unset($event['recurrence']['EXDATE']);  // don't serialize EXDATEs into RRULE value
             }
             if (isset($event['recurrence']['RDATE'])) {
                 $rdates = $event['recurrence']['RDATE'];
                 unset($event['recurrence']['RDATE']);  // don't serialize RDATEs into RRULE value
             }
 
             if (!empty($event['recurrence']['FREQ'])) {
                 $ve->add('RRULE', libcalendaring::to_rrule($event['recurrence'], !empty($event['allday'])));
             }
 
             // add EXDATEs each one per line (for Thunderbird Lightning)
             if (is_array($exdates)) {
                 foreach ($exdates as $exdate) {
                     if ($exdate instanceof DateTimeInterface) {
                         $ve->add($this->datetime_prop($cal, 'EXDATE', $exdate));
                     }
                 }
             }
             // add RDATEs
             if (is_array($rdates)) {
                 foreach ($rdates as $rdate) {
                     $ve->add($this->datetime_prop($cal, 'RDATE', $rdate));
                 }
             }
         }
 
         if (!empty($event['categories'])) {
             $cat = $cal->create('CATEGORIES');
             $cat->setParts((array)$event['categories']);
             $ve->add($cat);
         }
 
         if (!empty($event['free_busy'])) {
             $ve->add('TRANSP', $event['free_busy'] == 'free' ? 'TRANSPARENT' : 'OPAQUE');
 
             // for Outlook clients we provide the X-MICROSOFT-CDO-BUSYSTATUS property
             if (stripos($this->agent, 'outlook') !== false) {
                 $ve->add('X-MICROSOFT-CDO-BUSYSTATUS', $event['free_busy'] == 'outofoffice' ? 'OOF' : strtoupper($event['free_busy']));
             }
         }
 
         if (!empty($event['priority'])) {
             $ve->add('PRIORITY', $event['priority']);
         }
 
         if (!empty($event['cancelled'])) {
             $ve->add('STATUS', 'CANCELLED');
         }
         else if (!empty($event['free_busy']) && $event['free_busy'] == 'tentative') {
             $ve->add('STATUS', 'TENTATIVE');
         }
         else if (!empty($event['complete']) && $event['complete'] == 100) {
             $ve->add('STATUS', 'COMPLETED');
         }
         else if (!empty($event['status'])) {
             $ve->add('STATUS', $event['status']);
         }
 
         if (!empty($event['complete'])) {
             $ve->add('PERCENT-COMPLETE', intval($event['complete']));
         }
 
         // Apple iCal and BusyCal required the COMPLETED date to be set in order to consider a task complete
         if (
             (!empty($event['status']) && $event['status'] == 'COMPLETED')
             || (!empty($event['complete']) && $event['complete'] == 100)
         ) {
             $completed = !empty($event['changed']) ? $event['changed'] : new DateTime('now - 1 hour');
             $ve->add($this->datetime_prop($cal, 'COMPLETED', $completed, true));
         }
 
         if (!empty($event['valarms'])) {
             foreach ($event['valarms'] as $alarm) {
                 $va = $cal->createComponent('VALARM');
                 $va->action = $alarm['action'];
                 if ($alarm['trigger'] instanceof DateTimeInterface) {
                     $va->add($this->datetime_prop($cal, 'TRIGGER', $alarm['trigger'], true, null, true));
                 }
                 else {
                     $alarm_props = array();
                     if (!empty($alarm['related']) && strtoupper($alarm['related']) == 'END') {
                         $alarm_props['RELATED'] = 'END';
                     }
                     $va->add('TRIGGER', $alarm['trigger'], $alarm_props);
                 }
 
                 if (!empty($alarm['action']) && $alarm['action'] == 'EMAIL') {
                     if (!empty($alarm['attendees'])) {
                         foreach ((array) $alarm['attendees'] as $attendee) {
                             $va->add('ATTENDEE', 'mailto:' . $attendee);
                         }
                     }
                 }
                 if (!empty($alarm['description'])) {
                     $va->add('DESCRIPTION', $alarm['description']);
                 }
                 if (!empty($alarm['summary'])) {
                     $va->add('SUMMARY', $alarm['summary']);
                 }
                 if (!empty($alarm['duration'])) {
                     $va->add('DURATION', $alarm['duration']);
                     $va->add('REPEAT', !empty($alarm['repeat']) ? intval($alarm['repeat']) : 0);
                 }
                 if (!empty($alarm['uri'])) {
                     $va->add('ATTACH', $alarm['uri'], array('VALUE' => 'URI'));
                 }
                 $ve->add($va);
             }
         }
         // legacy support
         else if (!empty($event['alarms'])) {
             $va = $cal->createComponent('VALARM');
             list($trigger, $va->action) = explode(':', $event['alarms']);
             $val = libcalendaring::parse_alarm_value($trigger);
             if (!empty($val[3])) {
                 $va->add('TRIGGER', $val[3]);
             }
             else if ($val[0] instanceof DateTimeInterface) {
                 $va->add($this->datetime_prop($cal, 'TRIGGER', $val[0], true, null, true));
             }
             $ve->add($va);
         }
 
         // Find SCHEDULE-AGENT
         if (!empty($event['x-custom'])) {
             foreach ((array) $event['x-custom'] as $prop) {
                 if ($prop[0] === 'SCHEDULE-AGENT') {
                     $schedule_agent = $prop[1];
                 }
             }
         }
 
         if (!empty($event['attendees'])) {
             foreach ((array) $event['attendees'] as $attendee) {
                 if ($attendee['role'] == 'ORGANIZER') {
                     if (empty($event['organizer']))
                         $event['organizer'] = $attendee;
                 }
                 else if (!empty($attendee['email'])) {
                     if (isset($attendee['rsvp'])) {
                         $attendee['rsvp'] = $attendee['rsvp'] ? 'TRUE' : null;
                     }
 
                     $mailto   = $attendee['email'];
                     $attendee = array_filter(self::map_keys($attendee, $this->attendee_keymap));
 
                     if (isset($schedule_agent) && !isset($attendee['SCHEDULE-AGENT'])) {
                         $attendee['SCHEDULE-AGENT'] = $schedule_agent;
                     }
 
                     $ve->add('ATTENDEE', 'mailto:' . $mailto, $attendee);
                 }
             }
         }
 
         if (!empty($event['organizer'])) {
             $organizer = array_filter(self::map_keys($event['organizer'], $this->organizer_keymap));
 
             if (isset($schedule_agent) && !isset($organizer['SCHEDULE-AGENT'])) {
                 $organizer['SCHEDULE-AGENT'] = $schedule_agent;
             }
 
             $ve->add('ORGANIZER', 'mailto:' . $event['organizer']['email'], $organizer);
         }
 
         if (!empty($event['url'])) {
             foreach ((array) $event['url'] as $url) {
                 if (!empty($url)) {
                     $ve->add('URL', $url);
                 }
             }
         }
 
         if (!empty($event['parent_id'])) {
             $ve->add('RELATED-TO', $event['parent_id'], array('RELTYPE' => 'PARENT'));
         }
 
         if (!empty($event['comment'])) {
             $ve->add('COMMENT', $event['comment']);
         }
 
         $memory_limit = parse_bytes(ini_get('memory_limit'));
 
         // export attachments
         if (!empty($event['attachments'])) {
             foreach ((array)$event['attachments'] as $attach) {
                 // check available memory and skip attachment export if we can't buffer it
                 // @todo: use rcube_utils::mem_check()
                 if (is_callable($get_attachment) && $memory_limit > 0 && ($memory_used = function_exists('memory_get_usage') ? memory_get_usage() : 16*1024*1024)
                     && $attach['size'] && $memory_used + $attach['size'] * 3 > $memory_limit) {
                     continue;
                 }
                 // embed attachments using the given callback function
                 if (is_callable($get_attachment) && ($data = call_user_func($get_attachment, $attach['id'], $event))) {
                     // embed attachments for iCal
                     $ve->add('ATTACH',
                         $data,
                         array_filter(array('VALUE' => 'BINARY', 'ENCODING' => 'BASE64', 'FMTTYPE' => $attach['mimetype'], 'X-LABEL' => $attach['name'])));
                     unset($data);  // attempt to free memory
                 }
                 // list attachments as absolute URIs
                 else if (!empty($this->attach_uri)) {
                     $ve->add('ATTACH',
                         strtr($this->attach_uri, array(
                             '{{id}}'       => urlencode($attach['id']),
                             '{{name}}'     => urlencode($attach['name']),
                             '{{mimetype}}' => urlencode($attach['mimetype']),
                         )),
                         array('FMTTYPE' => $attach['mimetype'], 'VALUE' => 'URI'));
                 }
             }
         }
 
         if (!empty($event['links'])) {
             foreach ((array) $event['links'] as $uri) {
                 $ve->add('ATTACH', $uri);
             }
         }
 
         // add custom properties
         if (!empty($event['x-custom'])) {
             foreach ((array) $event['x-custom'] as $prop) {
                 $ve->add($prop[0], $prop[1]);
             }
         }
 
         // append to vcalendar container
         if ($vcal) {
             $vcal->add($ve);
         }
         else {   // serialize and send to stdout
             echo $ve->serialize();
         }
 
         // append recurrence exceptions
         if (!empty($event['recurrence']) && !empty($event['recurrence']['EXCEPTIONS'])) {
             foreach ($event['recurrence']['EXCEPTIONS'] as $ex) {
                 $exdate = !empty($ex['recurrence_date']) ? $ex['recurrence_date'] : $ex['start'];
                 $recurrence_id = $this->datetime_prop($cal, 'RECURRENCE-ID', $exdate, false, !empty($event['allday']));
                 if (!empty($ex['thisandfuture'])) {
                     $recurrence_id->add('RANGE', 'THISANDFUTURE');
                 }
 
                 $ex['uid'] = $ve->UID;
 
                 $this->_to_ical($ex, $vcal, $get_attachment, $recurrence_id);
             }
         }
     }
 
     /**
      * Returns a VTIMEZONE component for a Olson timezone identifier
      * with daylight transitions covering the given date range.
      *
      * @param string Timezone ID as used in PHP's Date functions
      * @param integer Unix timestamp with first date/time in this timezone
      * @param integer Unix timestap with last date/time in this timezone
      * @param VObject\Component\VCalendar Optional VCalendar component
      *
      * @return mixed A Sabre\VObject\Component object representing a VTIMEZONE definition
      *               or false if no timezone information is available
      */
     public static function get_vtimezone($tzid, $from = 0, $to = 0, $cal = null)
     {
         // TODO: Consider using tzurl.org database for better interoperability e.g. with Outlook
 
         if (!$from) $from = time();
         if (!$to)   $to = $from;
         if (!$cal)  $cal = new VObject\Component\VCalendar();
 
         if (is_string($tzid)) {
             try {
                 $tz = new \DateTimeZone($tzid);
             }
             catch (\Exception $e) {
                 return false;
             }
         }
         else if (is_a($tzid, '\\DateTimeZone')) {
             $tz = $tzid;
         }
 
         if (empty($tz) || !is_a($tz, '\\DateTimeZone')) {
             return false;
         }
 
         $year = 86400 * 360;
         $transitions = $tz->getTransitions($from - $year, $to + $year);
 
         // Make sure VTIMEZONE contains at least one STANDARD/DAYLIGHT component
         // when there's only one transition in specified time period (T5626)
         if (count($transitions) == 1) {
             // Get more transitions and use OFFSET from the previous to last
             $more_transitions = $tz->getTransitions(0, $to + $year);
             if (count($more_transitions) > 1) {
                 $index  = count($more_transitions) - 2;
                 $tzfrom = $more_transitions[$index]['offset'] / 3600;
             }
         }
 
         $vt = $cal->createComponent('VTIMEZONE');
         $vt->TZID = $tz->getName();
 
         $std = null; $dst = null;
         foreach ($transitions as $i => $trans) {
             $cmp = null;
 
             if (!isset($tzfrom)) {
                 $tzfrom = $trans['offset'] / 3600;
                 continue;
             }
 
             if ($trans['isdst']) {
                 $t_dst = $trans['ts'];
                 $dst = $cal->createComponent('DAYLIGHT');
                 $cmp = $dst;
             }
             else {
                 $t_std = $trans['ts'];
                 $std = $cal->createComponent('STANDARD');
                 $cmp = $std;
             }
 
             if ($cmp) {
                 $dt = new DateTime($trans['time']);
                 $offset = $trans['offset'] / 3600;
 
                 $cmp->DTSTART = $dt->format('Ymd\THis');
                 $cmp->TZOFFSETFROM = sprintf('%+03d%02d', floor($tzfrom), ($tzfrom - floor($tzfrom)) * 60);
                 $cmp->TZOFFSETTO   = sprintf('%+03d%02d', floor($offset), ($offset - floor($offset)) * 60);
 
                 if (!empty($trans['abbr'])) {
                     $cmp->TZNAME = $trans['abbr'];
                 }
 
                 $tzfrom = $offset;
                 $vt->add($cmp);
             }
 
             // we covered the entire date range
             if ($std && $dst && min($t_std, $t_dst) < $from && max($t_std, $t_dst) > $to) {
                 break;
             }
         }
 
         // add X-MICROSOFT-CDO-TZID if available
         $microsoftExchangeMap = array_flip(VObject\TimeZoneUtil::$microsoftExchangeMap);
         if (array_key_exists($tz->getName(), $microsoftExchangeMap)) {
             $vt->add('X-MICROSOFT-CDO-TZID', $microsoftExchangeMap[$tz->getName()]);
         }
 
         return $vt;
     }
 
 
     /*** Implement PHP 5 Iterator interface to make foreach work ***/
 
     #[\ReturnTypeWillChange]
     function current()
     {
         return $this->objects[$this->iteratorkey];
     }
 
     #[\ReturnTypeWillChange]
     function key()
     {
         return $this->iteratorkey;
     }
 
     #[\ReturnTypeWillChange]
     function next()
     {
         $this->iteratorkey++;
 
         // read next chunk if we're reading from a file
         if (empty($this->objects[$this->iteratorkey]) && $this->fp) {
             $this->_parse_next(true);
         }
 
         return $this->valid();
     }
 
     #[\ReturnTypeWillChange]
     function rewind()
     {
         $this->iteratorkey = 0;
     }
 
     #[\ReturnTypeWillChange]
     function valid()
     {
         return !empty($this->objects[$this->iteratorkey]);
     }
 
 }
 
 
 /**
  * Override Sabre\VObject\Property\Text that quotes commas in the location property
  * because Apple clients treat that property as list.
  */
 class vobject_location_property extends VObject\Property\Text
 {
     /**
      * List of properties that are considered 'structured'.
      *
      * @var array
      */
     protected $structuredValues = [
         // vCard
         'N',
         'ADR',
         'ORG',
         'GENDER',
         'LOCATION',
         // iCalendar
         'REQUEST-STATUS',
     ];
 }
diff --git a/plugins/libcalendaring/tests/RecurrenceTest.php b/plugins/libcalendaring/tests/RecurrenceTest.php
index 7d191474..cdbb2a8d 100644
--- a/plugins/libcalendaring/tests/RecurrenceTest.php
+++ b/plugins/libcalendaring/tests/RecurrenceTest.php
@@ -1,272 +1,273 @@
 <?php
 
 /**
  * libcalendaring_recurrence tests
  *
  * @author Aleksander Machniak <machniak@apheleia-it.ch>
  *
  * Copyright (C) 2022, Apheleia IT AG <contact@apheleia-it.ch>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class RecurrenceTest extends PHPUnit\Framework\TestCase
 {
     private $plugin;
 
     function setUp(): void
     {
         $rcube = rcmail::get_instance();
         $rcube->plugins->load_plugin('libcalendaring', true, true);
 
         $this->plugin = $rcube->plugins->get_plugin('libcalendaring');
     }
 
     /**
      * Test for libcalendaring_recurrence::first_occurrence()
      *
      * @dataProvider data_first_occurrence
      */
     function test_first_occurrence($recurrence_data, $start, $expected)
     {
         $start = new DateTime($start);
         if (!empty($recurrence_data['UNTIL'])) {
             $recurrence_data['UNTIL'] = new DateTime($recurrence_data['UNTIL']);
         }
 
         $recurrence = $this->plugin->get_recurrence();
 
         $recurrence->init($recurrence_data, $start);
         $first = $recurrence->first_occurrence();
 
         $this->assertEquals($expected, $first ? $first->format('Y-m-d H:i:s') : '');
     }
 
     /**
      * Data for test_first_occurrence()
      */
     function data_first_occurrence()
     {
         // TODO: BYYEARDAY, BYWEEKNO, BYSETPOS, WKST
 
         return array(
             // non-recurring
             array(
                 array(),                                     // recurrence data
                 '2017-08-31 11:00:00',                       // start date
                 '2017-08-31 11:00:00',                       // expected result
             ),
             // daily
             array(
                 array('FREQ' => 'DAILY', 'INTERVAL' => '1'), // recurrence data
                 '2017-08-31 11:00:00',                       // start date
                 '2017-08-31 11:00:00',                       // expected result
             ),
             // TODO: this one is not supported by the Calendar UI
 /*
             array(
                 array('FREQ' => 'DAILY', 'INTERVAL' => '1', 'BYMONTH' => 1),
                 '2017-08-31 11:00:00',
                 '2018-01-01 11:00:00',
             ),
 */
             // weekly
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '1'),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-08-31 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '1', 'BYDAY' => 'WE'),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-09-06 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '1', 'BYDAY' => 'TH'),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-08-31 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '1', 'BYDAY' => 'FR'),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-09-01 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '2'),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-08-31 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '3', 'BYDAY' => 'WE'),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-09-20 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '1', 'BYDAY' => 'WE', 'COUNT' => 1),
                 '2017-08-31 11:00:00', // Thursday
                 '2017-09-06 11:00:00',
             ),
             array(
                 array('FREQ' => 'WEEKLY', 'INTERVAL' => '1', 'BYDAY' => 'WE', 'UNTIL' => '2017-09-01'),
                 '2017-08-31 11:00:00', // Thursday
                 '',
             ),
             // monthly
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '1'),
                 '2017-09-08 11:00:00',
                 '2017-09-08 11:00:00',
             ),
 /*
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '1', 'BYMONTHDAY' => '8,9'),
                 '2017-08-31 11:00:00',
                 '2017-09-08 11:00:00',
             ),
 */
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '1', 'BYMONTHDAY' => '8,9'),
                 '2017-09-08 11:00:00',
                 '2017-09-08 11:00:00',
             ),
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '1', 'BYDAY' => '1WE'),
                 '2017-08-16 11:00:00',
                 '2017-09-06 11:00:00',
             ),
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '1', 'BYDAY' => '-1WE'),
                 '2017-08-16 11:00:00',
                 '2017-08-30 11:00:00',
             ),
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '2'),
                 '2017-09-08 11:00:00',
                 '2017-09-08 11:00:00',
             ),
 /*
             array(
                 array('FREQ' => 'MONTHLY', 'INTERVAL' => '2', 'BYMONTHDAY' => '8'),
                 '2017-08-31 11:00:00',
                 '2017-09-08 11:00:00', // ??????
             ),
 */
             // yearly
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '1'),
                 '2017-08-16 12:00:00',
                 '2017-08-16 12:00:00',
             ),
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '1', 'BYMONTH' => '8'),
                 '2017-08-16 12:00:00',
                 '2017-08-16 12:00:00',
             ),
 /*
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '1', 'BYDAY' => '-1MO'),
                 '2017-08-16 11:00:00',
                 '2017-12-25 11:00:00',
             ),
 */
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '1', 'BYMONTH' => '8', 'BYDAY' => '-1MO'),
                 '2017-08-16 11:00:00',
                 '2017-08-28 11:00:00',
             ),
 /*
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '1', 'BYMONTH' => '1', 'BYDAY' => '1MO'),
                 '2017-08-16 11:00:00',
                 '2018-01-01 11:00:00',
             ),
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '1', 'BYMONTH' => '1,9', 'BYDAY' => '1MO'),
                 '2017-08-16 11:00:00',
                 '2017-09-04 11:00:00',
             ),
 */
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '2'),
                 '2017-08-16 11:00:00',
                 '2017-08-16 11:00:00',
             ),
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '2', 'BYMONTH' => '8'),
                 '2017-08-16 11:00:00',
                 '2017-08-16 11:00:00',
             ),
 /*
             array(
                 array('FREQ' => 'YEARLY', 'INTERVAL' => '2', 'BYDAY' => '-1MO'),
                 '2017-08-16 11:00:00',
                 '2017-12-25 11:00:00',
             ),
 */
             // on dates (FIXME: do we really expect the first occurrence to be on the start date?)
             array(
                 array('RDATE' => array(new DateTime('2017-08-10 11:00:00 Europe/Warsaw'))),
                 '2017-08-01 11:00:00',
                 '2017-08-01 11:00:00',
             ),
         );
     }
 
     /**
      * Test for libcalendaring_recurrence::first_occurrence() for all-day events
      *
      * @dataProvider data_first_occurrence
      */
     function test_first_occurrence_allday($recurrence_data, $start, $expected)
     {
         $start = new libcalendaring_datetime($start);
         $start->_dateonly = true;
 
         if (!empty($recurrence_data['UNTIL'])) {
             $recurrence_data['UNTIL'] = new DateTime($recurrence_data['UNTIL']);
         }
 
         $recurrence = $this->plugin->get_recurrence();
 
         $recurrence->init($recurrence_data, $start);
         $first = $recurrence->first_occurrence();
 
         $this->assertEquals($expected, $first ? $first->format('Y-m-d H:i:s') : '');
 
         if ($expected) {
             $this->assertTrue($first->_dateonly);
         }
     }
 
     /**
-     * Test for libcalendaring_recurrence::next()
+     * Test for libcalendaring_recurrence::next_instance()
      */
     function test_next_instance()
     {
         date_default_timezone_set('America/New_York');
 
         $start = new libcalendaring_datetime('2017-08-31 11:00:00', new DateTimeZone('Europe/Berlin'));
-        $start->_dateonly = true;
-
-        $recurrence = $this->plugin->get_recurrence();
-
-        $recurrence->init(['FREQ' => 'WEEKLY', 'INTERVAL' => '1'], $start);
+        $event = [
+            'start'      => $start,
+            'recurrence' => ['FREQ' => 'WEEKLY', 'INTERVAL' => '1'],
+            'allday'     => true,
+        ];
 
-        $next = $recurrence->next();
+        $recurrence = new libcalendaring_recurrence($this->plugin, $event);
+        $next       = $recurrence->next_instance();
 
-        $this->assertEquals($start->format('2017-09-07 H:i:s'), $next->format('Y-m-d H:i:s'), 'Same time');
-        $this->assertEquals($start->getTimezone()->getName(), $next->getTimezone()->getName(), 'Same timezone');
-        $this->assertTrue($next->_dateonly, '_dateonly flag');
+        $this->assertEquals($start->format('2017-09-07 H:i:s'), $next['start']->format('Y-m-d H:i:s'), 'Same time');
+        $this->assertEquals($start->getTimezone()->getName(), $next['start']->getTimezone()->getName(), 'Same timezone');
+        $this->assertTrue($next['start']->_dateonly, '_dateonly flag');
     }
 }
diff --git a/plugins/libkolab/lib/kolab_date_recurrence.php b/plugins/libkolab/lib/kolab_date_recurrence.php
index 9b09074b..f2110b03 100644
--- a/plugins/libkolab/lib/kolab_date_recurrence.php
+++ b/plugins/libkolab/lib/kolab_date_recurrence.php
@@ -1,239 +1,241 @@
 <?php
 
 /**
  * Recurrence computation class for xcal-based Kolab format objects
  *
  * Utility class to compute instances of recurring events.
  * It requires the libcalendaring PHP extension to be installed and loaded.
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012-2016, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class kolab_date_recurrence
 {
     private /* EventCal */ $engine;
     private /* kolab_format_xcal */ $object;
     private /* DateTime */ $start;
     private /* DateTime */ $next;
     private /* cDateTime */ $cnext;
     private /* DateInterval */ $duration;
     private /* bool */ $allday;
 
 
     /**
      * Default constructor
      *
      * @param kolab_format_xcal The Kolab object to operate on
      */
     function __construct($object)
     {
         $data = $object->to_array();
 
         $this->object = $object;
         $this->engine = $object->to_libcal();
         $this->start  = $this->next = $data['start'];
         $this->allday = !empty($data['allday']);
         $this->cnext  = kolab_format::get_datetime($this->next);
 
         if (is_object($data['start']) && is_object($data['end'])) {
             $this->duration = $data['start']->diff($data['end']);
         }
         else {
             // Prevent from errors when end date is not set (#5307) RFC5545 3.6.1
             $seconds = !empty($data['end']) ? ($data['end'] - $data['start']) : 0;
             $this->duration = new DateInterval('PT' . $seconds . 'S');
         }
     }
 
     /**
      * Get date/time of the next occurence of this event
      *
      * @param bool Return a Unix timestamp instead of a DateTime object
      *
      * @return DateTime|int|false Object/unix timestamp or False if recurrence ended
      */
     public function next_start($timestamp = false)
     {
         $time = false;
 
         if ($this->engine && $this->next) {
             if (($cnext = new cDateTime($this->engine->getNextOccurence($this->cnext))) && $cnext->isValid()) {
                 $next = kolab_format::php_datetime($cnext, $this->start->getTimezone());
                 $time = $timestamp ? $next->format('U') : $next;
 
                 if ($this->allday) {
                     // it looks that for allday events the occurrence time
                     // is reset to 00:00:00, this is causing various issues
                     $next->setTime($this->start->format('G'), $this->start->format('i'), $this->start->format('s'));
                     $next->_dateonly = true;
                 }
 
                 $this->cnext = $cnext;
                 $this->next  = $next;
             }
         }
 
         return $time;
     }
 
     /**
      * Get the next recurring instance of this event
      *
      * @return mixed Array with event properties or False if recurrence ended
      */
     public function next_instance()
     {
         if ($next_start = $this->next_start()) {
             $next_end = clone $next_start;
             $next_end->add($this->duration);
 
             $next                    = $this->object->to_array();
             $recurrence_id_format    = libkolab::recurrence_id_format($next);
             $next['start']           = $next_start;
             $next['end']             = $next_end;
             $next['recurrence_date'] = clone $next_start;
             $next['_instance']       = $next_start->format($recurrence_id_format);
 
             unset($next['_formatobj']);
 
             return $next;
         }
 
         return false;
     }
 
     /**
-     * Get the end date of the occurence of this recurrence cycle
+     * Get the end date of the last occurence of this recurrence cycle
      *
      * @return DateTime|bool End datetime of the last event or False if recurrence exceeds limit
      */
     public function end()
     {
         $event = $this->object->to_array();
 
         // recurrence end date is given
         if ($event['recurrence']['UNTIL'] instanceof DateTimeInterface) {
             return $event['recurrence']['UNTIL'];
         }
 
         // let libkolab do the work
         if ($this->engine && ($cend = $this->engine->getLastOccurrence())
             && ($end_dt = kolab_format::php_datetime(new cDateTime($cend)))
         ) {
             return $end_dt;
         }
 
         // determine a reasonable end date if none given
         if (!$event['recurrence']['COUNT'] && $event['end'] instanceof DateTimeInterface) {
             $end_dt = clone $event['end'];
             $end_dt->add(new DateInterval('P100Y'));
 
             return $end_dt;
         }
 
         return false;
     }
 
     /**
      * Find date/time of the first occurrence
+     *
+     * @return DateTime|null First occurrence
      */
     public function first_occurrence()
     {
         $event      = $this->object->to_array();
         $start      = clone $this->start;
         $orig_start = clone $this->start;
         $interval   = intval($event['recurrence']['INTERVAL'] ?: 1);
 
         switch ($event['recurrence']['FREQ']) {
         case 'WEEKLY':
             if (empty($event['recurrence']['BYDAY'])) {
                 return $orig_start;
             }
 
             $start->sub(new DateInterval("P{$interval}W"));
             break;
 
         case 'MONTHLY':
             if (empty($event['recurrence']['BYDAY']) && empty($event['recurrence']['BYMONTHDAY'])) {
                 return $orig_start;
             }
 
             $start->sub(new DateInterval("P{$interval}M"));
             break;
 
         case 'YEARLY':
             if (empty($event['recurrence']['BYDAY']) && empty($event['recurrence']['BYMONTH'])) {
                 return $orig_start;
             }
 
             $start->sub(new DateInterval("P{$interval}Y"));
             break;
 
         case 'DAILY':
             if (!empty($event['recurrence']['BYMONTH'])) {
                 break;
             }
 
         default:
             return $orig_start;
         }
 
         $event['start'] = $start;
         $event['recurrence']['INTERVAL'] = $interval;
         if ($event['recurrence']['COUNT']) {
             // Increase count so we do not stop the loop to early
             $event['recurrence']['COUNT'] += 100;
         }
 
         // Create recurrence that starts in the past
         $object_type = $this->object instanceof kolab_format_task ? 'task' : 'event';
         $object      = kolab_format::factory($object_type, 3.0);
         $object->set($event);
         $recurrence = new self($object);
 
         $orig_date = $orig_start->format('Y-m-d');
         $found     = false;
 
         // find the first occurrence
         while ($next = $recurrence->next_start()) {
             $start = $next;
             if ($next->format('Y-m-d') >= $orig_date) {
                 $found = true;
                 break;
             }
         }
 
         if (!$found) {
             rcube::raise_error(array(
                 'file' => __FILE__,
                 'line' => __LINE__,
                 'message' => sprintf("Failed to find a first occurrence. Start: %s, Recurrence: %s",
                     $orig_start->format(DateTime::ISO8601), json_encode($event['recurrence'])),
             ), true);
 
             return null;
         }
 
         if ($this->allday) {
             $start->_dateonly = true;
         }
 
         return $start;
     }
 }
diff --git a/plugins/tasklist/tasklist.php b/plugins/tasklist/tasklist.php
index a62d8dda..1ef2e863 100644
--- a/plugins/tasklist/tasklist.php
+++ b/plugins/tasklist/tasklist.php
@@ -1,2523 +1,2523 @@
 <?php
 
 /**
  * Tasks plugin for Roundcube webmail
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class tasklist extends rcube_plugin
 {
     const FILTER_MASK_TODAY = 1;
     const FILTER_MASK_TOMORROW = 2;
     const FILTER_MASK_WEEK = 4;
     const FILTER_MASK_LATER = 8;
     const FILTER_MASK_NODATE = 16;
     const FILTER_MASK_OVERDUE = 32;
     const FILTER_MASK_FLAGGED = 64;
     const FILTER_MASK_COMPLETE = 128;
     const FILTER_MASK_ASSIGNED = 256;
     const FILTER_MASK_MYTASKS = 512;
 
     const SESSION_KEY = 'tasklist_temp';
 
     public static $filter_masks = array(
         'today'    => self::FILTER_MASK_TODAY,
         'tomorrow' => self::FILTER_MASK_TOMORROW,
         'week'     => self::FILTER_MASK_WEEK,
         'later'    => self::FILTER_MASK_LATER,
         'nodate'   => self::FILTER_MASK_NODATE,
         'overdue'  => self::FILTER_MASK_OVERDUE,
         'flagged'  => self::FILTER_MASK_FLAGGED,
         'complete' => self::FILTER_MASK_COMPLETE,
         'assigned' => self::FILTER_MASK_ASSIGNED,
         'mytasks'  => self::FILTER_MASK_MYTASKS,
     );
 
     public $task = '?(?!login|logout).*';
     public $allowed_prefs = array('tasklist_sort_col','tasklist_sort_order');
 
     public $rc;
     public $lib;
     public $timezone;
     public $ui;
     public $home;  // declare public to be used in other classes
 
     // These are handled by __get()
     // public $driver;
     // public $itip;
     // public $ical;
 
     private $collapsed_tasks = array();
     private $message_tasks   = array();
     private $task_titles     = array();
 
 
     /**
      * Plugin initialization.
      */
     function init()
     {
         $this->require_plugin('libcalendaring');
         $this->require_plugin('libkolab');
 
         $this->rc  = rcube::get_instance();
         $this->lib = libcalendaring::get_instance();
 
         $this->register_task('tasks', 'tasklist');
 
         // load plugin configuration
         $this->load_config();
 
         $this->timezone = $this->lib->timezone;
 
         // proceed initialization in startup hook
         $this->add_hook('startup', array($this, 'startup'));
 
         $this->add_hook('user_delete', array($this, 'user_delete'));
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         // the tasks module can be enabled/disabled by the kolab_auth plugin
         if ($this->rc->config->get('tasklist_disabled', false) || !$this->rc->config->get('tasklist_enabled', true))
             return;
 
         // load localizations
         $this->add_texts('localization/', $args['task'] == 'tasks' && (!$args['action'] || $args['action'] == 'print'));
         $this->rc->load_language($_SESSION['language'], array('tasks.tasks' => $this->gettext('navtitle')));  // add label for task title
 
         if ($args['task'] == 'tasks' && $args['action'] != 'save-pref') {
             $this->load_driver();
 
             // register calendar actions
             $this->register_action('index', array($this, 'tasklist_view'));
             $this->register_action('task', array($this, 'task_action'));
             $this->register_action('tasklist', array($this, 'tasklist_action'));
             $this->register_action('counts', array($this, 'fetch_counts'));
             $this->register_action('fetch', array($this, 'fetch_tasks'));
             $this->register_action('print', array($this, 'print_tasks'));
             $this->register_action('dialog-ui', array($this, 'mail_message2task'));
             $this->register_action('get-attachment', array($this, 'attachment_get'));
             $this->register_action('upload', array($this, 'attachment_upload'));
             $this->register_action('import', array($this, 'import_tasks'));
             $this->register_action('export', array($this, 'export_tasks'));
             $this->register_action('mailimportitip', array($this, 'mail_import_itip'));
             $this->register_action('mailimportattach', array($this, 'mail_import_attachment'));
             $this->register_action('itip-status', array($this, 'task_itip_status'));
             $this->register_action('itip-remove', array($this, 'task_itip_remove'));
             $this->register_action('itip-decline-reply', array($this, 'mail_itip_decline_reply'));
             $this->register_action('itip-delegate', array($this, 'mail_itip_delegate'));
             $this->add_hook('refresh', array($this, 'refresh'));
 
             $this->collapsed_tasks = array_filter(explode(',', $this->rc->config->get('tasklist_collapsed_tasks', '')));
         }
         else if ($args['task'] == 'mail') {
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 if ($this->rc->config->get('tasklist_mail_embed', true)) {
                     $this->add_hook('message_load', array($this, 'mail_message_load'));
                 }
                 $this->add_hook('template_object_messagebody', array($this, 'mail_messagebody_html'));
             }
 
             // add 'Create event' item to message menu
             if ($this->api->output->type == 'html' && (empty($_GET['_rel']) || $_GET['_rel'] != 'task')) {
                 $this->api->add_content(html::tag('li', array('role' => 'menuitem'),
                     $this->api->output->button(array(
                         'command'  => 'tasklist-create-from-mail',
                         'label'    => 'tasklist.createfrommail',
                         'type'     => 'link',
                         'classact' => 'icon taskaddlink active',
                         'class'    => 'icon taskaddlink disabled',
                         'innerclass' => 'icon taskadd',
                     ))),
                 'messagemenu');
 
                 $this->api->output->add_label('tasklist.createfrommail');
             }
         }
 
         if (!$this->rc->output->ajax_call && empty($this->rc->output->env['framed'])) {
             $this->load_ui();
             $this->ui->init();
         }
 
         // add hooks for alarms handling
         $this->add_hook('pending_alarms', array($this, 'pending_alarms'));
         $this->add_hook('dismiss_alarms', array($this, 'dismiss_alarms'));
     }
 
     /**
      *
      */
     private function load_ui()
     {
         if (!$this->ui) {
             require_once($this->home . '/tasklist_ui.php');
             $this->ui = new tasklist_ui($this);
         }
     }
 
     /**
      * Helper method to load the backend driver according to local config
      */
     private function load_driver()
     {
         if (!empty($this->driver)) {
             return;
         }
 
         $driver_name  = $this->rc->config->get('tasklist_driver', 'database');
         $driver_class = 'tasklist_' . $driver_name . '_driver';
 
         require_once($this->home . '/drivers/tasklist_driver.php');
         require_once($this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php');
 
         $this->driver = new $driver_class($this);
 
         $this->rc->output->set_env('tasklist_driver', $driver_name);
     }
 
     /**
      * Dispatcher for task-related actions initiated by the client
      */
     public function task_action()
     {
         $filter = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $action = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $rec    = rcube_utils::get_input_value('t', rcube_utils::INPUT_POST, true);
         $oldrec = $rec;
         $success = $refresh = $got_msg = false;
 
         // force notify if hidden + active
         $itip_send_option = (int)$this->rc->config->get('calendar_itip_send_option', 3);
         if ($itip_send_option === 1 && empty($rec['_reportpartstat'])) {
             $rec['_notify'] = 1;
         }
 
         switch ($action) {
         case 'new':
             $oldrec = null;
             $rec = $this->prepare_task($rec);
             $rec['uid'] = $this->generate_uid();
             $temp_id = !empty($rec['tempid']) ? $rec['tempid'] : null;
             if ($success = $this->driver->create_task($rec)) {
                 $refresh = $this->driver->get_task($rec);
                 if ($temp_id) $refresh['tempid'] = $temp_id;
                 $this->cleanup_task($rec);
             }
             break;
 
         case 'complete':
             $complete = intval(rcube_utils::get_input_value('complete', rcube_utils::INPUT_POST));
             if (!($rec = $this->driver->get_task($rec))) {
                 break;
             }
 
             $oldrec = $rec;
             $rec['status'] = $complete ? 'COMPLETED' : ($rec['complete'] > 0 ? 'IN-PROCESS' : 'NEEDS-ACTION');
 
             // sent itip notifications if enabled (no user interaction here)
             if (($itip_send_option & 1)) {
                 if ($this->is_attendee($rec)) {
                     $rec['_reportpartstat'] = $rec['status'];
                 }
                 else if ($this->is_organizer($rec)) {
                     $rec['_notify'] = 1;
                 }
             }
 
         case 'edit':
             $oldrec = $this->driver->get_task($rec);
             $rec = $this->prepare_task($rec);
             $clone = $this->handle_recurrence($rec, $this->driver->get_task($rec));
             if ($success = $this->driver->edit_task($rec)) {
                 $new_task = $this->driver->get_task($rec);
                 $new_task['tempid'] = $rec['id'];
                 $refresh[] = $new_task;
                 $this->cleanup_task($rec);
 
                 // add clone from recurring task
                 if ($clone && $this->driver->create_task($clone)) {
                     $new_clone = $this->driver->get_task($clone);
                     $new_clone['tempid'] = $clone['id'];
                     $refresh[] = $new_clone;
                     $this->driver->clear_alarms($rec['id']);
                 }
 
                 // move all childs if list assignment was changed
                 if (!empty($rec['_fromlist']) && !empty($rec['list']) && $rec['_fromlist'] != $rec['list']) {
                     foreach ($this->driver->get_childs(array('id' => $rec['id'], 'list' => $rec['_fromlist']), true) as $cid) {
                         $child = array('id' => $cid, 'list' => $rec['list'], '_fromlist' => $rec['_fromlist']);
                         if ($this->driver->move_task($child)) {
                             $r = $this->driver->get_task($child);
                             if ((bool)($filter & self::FILTER_MASK_COMPLETE) == $this->driver->is_complete($r)) {
                                 $r['tempid'] = $cid;
                                 $refresh[] = $r;
                             }
                         }
                     }
                 }
             }
             break;
 
           case 'move':
               foreach ((array)$rec['id'] as $id) {
                   $r = $rec;
                   $r['id'] = $id;
                   if ($this->driver->move_task($r)) {
                       $new_task = $this->driver->get_task($r);
                       $new_task['tempid'] = $id;
                       $refresh[] = $new_task;
                       $success = true;
 
                       // move all childs, too
                       foreach ($this->driver->get_childs(array('id' => $id, 'list' => $rec['_fromlist']), true) as $cid) {
                           $child = $rec;
                           $child['id'] = $cid;
                           if ($this->driver->move_task($child)) {
                               $r = $this->driver->get_task($child);
                               if ((bool)($filter & self::FILTER_MASK_COMPLETE) == $this->driver->is_complete($r)) {
                                   $r['tempid'] = $cid;
                                   $refresh[] = $r;
                               }
                           }
                       }
                   }
               }
               break;
 
         case 'delete':
             $mode  = intval(rcube_utils::get_input_value('mode', rcube_utils::INPUT_POST));
             $oldrec = $this->driver->get_task($rec);
             if ($success = $this->driver->delete_task($rec, false)) {
                 // delete/modify all childs
                 foreach ($this->driver->get_childs($rec, $mode) as $cid) {
                     $child = array('id' => $cid, 'list' => $rec['list']);
 
                     if ($mode == 1) {  // delete all childs
                         if ($this->driver->delete_task($child, false)) {
                             if ($this->driver->undelete)
                                 $_SESSION['tasklist_undelete'][$rec['id']][] = $cid;
                         }
                         else
                             $success = false;
                     }
                     else {
                         $child['parent_id'] = strval($oldrec['parent_id']);
                         $this->driver->edit_task($child);
                     }
                 }
                 // update parent task to adjust list of children
                 if (!empty($oldrec['parent_id'])) {
                     $parent = array('id' => $oldrec['parent_id'], 'list' => $rec['list']);
                     if ($parent = $this->driver->get_task()) {
                         $refresh[] = $parent;
                     }
                 }
             }
 
             if (!$success)
                 $this->rc->output->command('plugin.reload_data');
             break;
 
         case 'undelete':
             if ($success = $this->driver->undelete_task($rec)) {
                 $refresh[] = $this->driver->get_task($rec);
                 foreach ((array)$_SESSION['tasklist_undelete'][$rec['id']] as $cid) {
                     if ($this->driver->undelete_task($rec)) {
                         $refresh[] = $this->driver->get_task($rec);
                     }
                 }
             }
             break;
 
         case 'collapse':
             foreach (explode(',', $rec['id']) as $rec_id) {
                 if (intval(rcube_utils::get_input_value('collapsed', rcube_utils::INPUT_GPC))) {
                     $this->collapsed_tasks[] = $rec_id;
                 }
                 else {
                     $i = array_search($rec_id, $this->collapsed_tasks);
                     if ($i !== false)
                         unset($this->collapsed_tasks[$i]);
                 }
             }
 
             $this->rc->user->save_prefs(array('tasklist_collapsed_tasks' => join(',', array_unique($this->collapsed_tasks))));
             return;  // avoid further actions
 
         case 'rsvp':
             $status = rcube_utils::get_input_value('status', rcube_utils::INPUT_GPC);
             $noreply = intval(rcube_utils::get_input_value('noreply', rcube_utils::INPUT_GPC)) || $status == 'needs-action';
             $task = $this->driver->get_task($rec);
             $task['attendees'] = $rec['attendees'];
             $task['_type'] = 'task';
 
             // send invitation to delegatee + add it as attendee
             if ($status == 'delegated' && $rec['to']) {
                 $itip = $this->load_itip();
                 if ($itip->delegate_to($task, $rec['to'], (bool)$rec['rsvp'])) {
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                     $refresh[] = $task;
                     $noreply = false;
                 }
             }
 
             $rec = $task;
 
             if ($success = $this->driver->edit_task($rec)) {
                 if (!$noreply) {
                     // let the reply clause further down send the iTip message
                     $rec['_reportpartstat'] = $status;
                 }
             }
             break;
 
         case 'changelog':
             $data = $this->driver->get_task_changelog($rec);
             if (is_array($data) && !empty($data)) {
                 $lib = $this->lib;
                 $dtformat = $this->rc->config->get('date_format') . ' ' . $this->rc->config->get('time_format');
                 array_walk($data, function(&$change) use ($lib, $dtformat) {
                   if ($change['date']) {
                       $dt = $lib->adjust_timezone($change['date']);
                       if ($dt instanceof DateTime) {
                           $change['date'] = $this->rc->format_date($dt, $dtformat, false);
                       }
                   }
                 });
                 $this->rc->output->command('plugin.task_render_changelog', $data);
             }
             else {
                 $this->rc->output->command('plugin.task_render_changelog', false);
             }
             $got_msg = true;
             break;
 
         case 'diff':
             $data = $this->driver->get_task_diff($rec, $rec['rev1'], $rec['rev2']);
             if (is_array($data)) {
                 // convert some properties, similar to self::_client_event()
                 $lib = $this->lib;
                 $date_format = $this->rc->config->get('date_format', 'Y-m-d');
                 $time_format = $this->rc->config->get('time_format', 'H:i');
                 array_walk($data['changes'], function(&$change, $i) use ($lib, $date_format, $time_format) {
                     // convert date cols
                     if (in_array($change['property'], array('date','start','created','changed'))) {
                         if (!empty($change['old'])) {
                             $dtformat = strlen($change['old']) == 10 ? $date_format : $date_format . ' ' . $time_format;
                             $change['old_'] = $lib->adjust_timezone($change['old'], strlen($change['old']) == 10)->format($dtformat);
                         }
                         if (!empty($change['new'])) {
                             $dtformat = strlen($change['new']) == 10 ? $date_format : $date_format . ' ' . $time_format;
                             $change['new_'] = $lib->adjust_timezone($change['new'], strlen($change['new']) == 10)->format($dtformat);
                         }
                     }
                     // create textual representation for alarms and recurrence
                     if ($change['property'] == 'alarms') {
                         if (is_array($change['old']))
                             $change['old_'] = libcalendaring::alarm_text($change['old']);
                         if (is_array($change['new']))
                             $change['new_'] = libcalendaring::alarm_text(array_merge((array)$change['old'], $change['new']));
                     }
                     if ($change['property'] == 'recurrence') {
                         if (is_array($change['old']))
                             $change['old_'] = $lib->recurrence_text($change['old']);
                         if (is_array($change['new']))
                             $change['new_'] = $lib->recurrence_text(array_merge((array)$change['old'], $change['new']));
                     }
                     if ($change['property'] == 'complete') {
                         $change['old_'] = intval($change['old']) . '%';
                         $change['new_'] = intval($change['new']) . '%';
                     }
                     if ($change['property'] == 'attachments') {
                         if (is_array($change['old']))
                             $change['old']['classname'] = rcube_utils::file2class($change['old']['mimetype'], $change['old']['name']);
                         if (is_array($change['new'])) {
                             $change['new'] = array_merge((array)$change['old'], $change['new']);
                             $change['new']['classname'] = rcube_utils::file2class($change['new']['mimetype'], $change['new']['name']);
                         }
                     }
                     // resolve parent_id to the refered task title for display
                     if ($change['property'] == 'parent_id') {
                         $change['property'] = 'parent-title';
                         if (!empty($change['old']) && ($old_parent = $this->driver->get_task(array('id' => $change['old'], 'list' => $rec['list'])))) {
                             $change['old_'] = $old_parent['title'];
                         }
                         if (!empty($change['new']) && ($new_parent = $this->driver->get_task(array('id' => $change['new'], 'list' => $rec['list'])))) {
                             $change['new_'] = $new_parent['title'];
                         }
                     }
                     // compute a nice diff of description texts
                     if ($change['property'] == 'description') {
                         $change['diff_'] = libkolab::html_diff($change['old'], $change['new']);
                     }
                 });
                 $this->rc->output->command('plugin.task_show_diff', $data);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectdiffnotavailable'), 'error');
             }
             $got_msg = true;
             break;
 
         case 'show':
             if ($rec = $this->driver->get_task_revison($rec, $rec['rev'])) {
                 $this->encode_task($rec);
                 $rec['readonly'] = 1;
                 $this->rc->output->command('plugin.task_show_revision', $rec);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectnotfound'), 'error');
             }
             $got_msg = true;
             break;
 
         case 'restore':
             if ($success = $this->driver->restore_task_revision($rec, $rec['rev'])) {
                 $refresh = $this->driver->get_task($rec);
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'objectrestoresuccess', 'vars' => array('rev' => $rec['rev']))), 'confirmation');
                 $this->rc->output->command('plugin.close_history_dialog');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectrestoreerror'), 'error');
             }
             $got_msg = true;
             break;
 
         }
 
         if ($success) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
             $this->update_counts($oldrec, $refresh);
         }
         else if (!$got_msg) {
             $this->rc->output->show_message('tasklist.errorsaving', 'error');
         }
 
         // send out notifications
         if ($success && !empty($rec['_notify']) && ($rec['attendees'] || $oldrec['attendees'])) {
             // make sure we have the complete record
             $task = $action == 'delete' ? $oldrec : $this->driver->get_task($rec);
 
             // only notify if data really changed (TODO: do diff check on client already)
             if (!$oldrec || $action == 'delete' || self::task_diff($task, $oldrec)) {
                 $sent = $this->notify_attendees($task, $oldrec, $action, $rec['_comment']);
                 if ($sent > 0)
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                 else if ($sent < 0)
                     $this->rc->output->show_message('tasklist.errornotifying', 'error');
             }
         }
 
         if ($success && !empty($rec['_reportpartstat']) && $rec['_reportpartstat'] != 'NEEDS-ACTION') {
             // get the full record after update
             if (!$task) {
                 $task = $this->driver->get_task($rec);
             }
 
             // send iTip REPLY with the updated partstat
             if ($task['organizer'] && ($idx = $this->is_attendee($task)) !== false) {
                 $sender = $task['attendees'][$idx];
                 $status = strtolower($sender['status']);
 
                 if (!empty($_POST['comment']))
                     $task['comment'] = rcube_utils::get_input_value('comment', rcube_utils::INPUT_POST);
 
                 $itip = $this->load_itip();
                 $itip->set_sender_email($sender['email']);
 
                 if ($itip->send_itip_message($this->to_libcal($task), 'REPLY', $task['organizer'], 'itipsubject' . $status, 'itipmailbody' . $status))
                     $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $task['organizer']['name'] ?: $task['organizer']['email']))), 'confirmation');
                 else
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
             }
         }
 
         // unlock client
         $this->rc->output->command('plugin.unlock_saving', $success);
 
         if ($refresh) {
             if (!empty($refresh['id'])) {
                 $this->encode_task($refresh);
             }
             else if (is_array($refresh)) {
                 foreach ($refresh as $i => $r)
                     $this->encode_task($refresh[$i]);
             }
             $this->rc->output->command('plugin.update_task', $refresh);
         }
         else if ($success && ($action == 'delete' || $action == 'undelete')) {
             $this->rc->output->command('plugin.refresh_tagcloud');
         }
     }
 
     /**
      * Load iTIP functions
      */
     private function load_itip()
     {
         if (empty($this->itip)) {
             require_once __DIR__ . '/../libcalendaring/lib/libcalendaring_itip.php';
             $this->itip = new libcalendaring_itip($this, 'tasklist');
             $this->itip->set_rsvp_actions(array('accepted','declined','delegated'));
             $this->itip->set_rsvp_status(array('accepted','tentative','declined','delegated','in-process','completed'));
         }
 
         return $this->itip;
     }
 
     /**
      * repares new/edited task properties before save
      */
     private function prepare_task($rec)
     {
         // try to be smart and extract date from raw input
         if (!empty($rec['raw'])) {
             foreach (array('today','tomorrow','sunday','monday','tuesday','wednesday','thursday','friday','saturday','sun','mon','tue','wed','thu','fri','sat') as $word) {
                 $locwords[] = '/^' . preg_quote(mb_strtolower($this->gettext($word))) . '\b/i';
                 $normwords[] = $word;
                 $datewords[] = $word;
             }
             foreach (array('jan','feb','mar','apr','may','jun','jul','aug','sep','oct','now','dec') as $month) {
                 $locwords[] = '/(' . preg_quote(mb_strtolower($this->gettext('long'.$month))) . '|' . preg_quote(mb_strtolower($this->gettext($month))) . ')\b/i';
                 $normwords[] = $month;
                 $datewords[] = $month;
             }
             foreach (array('on','this','next','at') as $word) {
                 $fillwords[] = preg_quote(mb_strtolower($this->gettext($word)));
                 $fillwords[] = $word;
             }
 
             $raw = trim($rec['raw']);
             $date_str = '';
 
             // translate localized keywords
             $raw = preg_replace('/^(' . join('|', $fillwords) . ')\s*/i', '', $raw);
             $raw = preg_replace($locwords, $normwords, $raw);
 
             // find date pattern
             $date_pattern = '!^(\d+[./-]\s*)?((?:\d+[./-])|' . join('|', $datewords) . ')\.?(\s+\d{4})?[:;,]?\s+!i';
             if (preg_match($date_pattern, $raw, $m)) {
                 $date_str .= $m[1] . $m[2] . $m[3];
                 $raw = preg_replace(array($date_pattern, '/^(' . join('|', $fillwords) . ')\s*/i'), '', $raw);
                 // add year to date string
                 if ($m[1] && !$m[3])
                     $date_str .= date('Y');
             }
 
             // find time pattern
             $time_pattern = '/^(\d+([:.]\d+)?(\s*[hapm.]+)?),?\s+/i';
             if (preg_match($time_pattern, $raw, $m)) {
                 $has_time = true;
                 $date_str .= ($date_str ? ' ' : 'today ') . $m[1];
                 $raw = preg_replace($time_pattern, '', $raw);
             }
 
             // yes, raw input matched a (valid) date
             if (strlen($date_str) && strtotime($date_str) && ($date = new DateTime($date_str, $this->timezone))) {
                 $rec['date'] = $date->format('Y-m-d');
                 if ($has_time)
                     $rec['time'] = $date->format('H:i');
                 $rec['title'] = $raw;
             }
             else
                 $rec['title'] = $rec['raw'];
         }
 
         // normalize input from client
         if (isset($rec['complete'])) {
             $rec['complete'] = floatval($rec['complete']);
             if ($rec['complete'] > 1)
                 $rec['complete'] /= 100;
         }
         if (isset($rec['flagged']))
             $rec['flagged'] = intval($rec['flagged']);
 
         // fix for garbage input
         if ($rec['description'] == 'null')
             $rec['description'] = '';
 
         foreach ($rec as $key => $val) {
             if ($val === 'null')
                 $rec[$key] = null;
         }
 
         if (!empty($rec['date'])) {
             $this->normalize_dates($rec, 'date', 'time');
         }
 
         if (!empty($rec['startdate'])) {
             $this->normalize_dates($rec, 'startdate', 'starttime');
         }
 
         // convert tags to array, filter out empty entries
         if (isset($rec['tags']) && !is_array($rec['tags'])) {
             $rec['tags'] = array_filter((array)$rec['tags']);
         }
 
         // convert the submitted alarm values
         if (!empty($rec['valarms'])) {
             $valarms = array();
             foreach (libcalendaring::from_client_alarms($rec['valarms']) as $alarm) {
                 // alarms can only work with a date (either task start, due or absolute alarm date)
                 if (is_a($alarm['trigger'], 'DateTime') || $rec['date'] || $rec['startdate'])
                     $valarms[] = $alarm;
             }
             $rec['valarms'] = $valarms;
         }
 
         // convert the submitted recurrence settings
         if (is_array($rec['recurrence'])) {
             $refdate = null;
             if (!empty($rec['date'])) {
                 $refdate = new DateTime($rec['date'] . ' ' . $rec['time'], $this->timezone);
             }
             else if (!empty($rec['startdate'])) {
                 $refdate = new DateTime($rec['startdate'] . ' ' . $rec['starttime'], $this->timezone);
             }
 
             if ($refdate) {
                 $rec['recurrence'] = $this->lib->from_client_recurrence($rec['recurrence'], $refdate);
 
                 // translate count into an absolute end date.
-                // why? because when shifting completed tasks to the next recurrence,
+                // why? because when shifting completed tasks to the next occurrence,
                 // the initial start date to count from gets lost.
                 if (!empty($rec['recurrence']['COUNT'])) {
                     $engine = libcalendaring::get_recurrence();
                     $engine->init($rec['recurrence'], $refdate);
                     if ($until = $engine->end()) {
                         $rec['recurrence']['UNTIL'] = $until;
                         unset($rec['recurrence']['COUNT']);
                     }
                 }
             }
             else {  // recurrence requires a reference date
                 $rec['recurrence'] = '';
             }
         }
 
         $attachments = array();
         $taskid = $rec['id'];
         if (!empty($_SESSION[self::SESSION_KEY]) && $_SESSION[self::SESSION_KEY]['id'] == $taskid) {
             if (!empty($_SESSION[self::SESSION_KEY]['attachments'])) {
                 foreach ($_SESSION[self::SESSION_KEY]['attachments'] as $id => $attachment) {
                     if (is_array($rec['attachments']) && in_array($id, $rec['attachments'])) {
                         $attachments[$id] = $this->rc->plugins->exec_hook('attachment_get', $attachment);
                         unset($attachments[$id]['abort'], $attachments[$id]['group']);
                     }
                 }
             }
         }
 
         $rec['attachments'] = $attachments;
 
         // convert link references into simple URIs
         if (array_key_exists('links', $rec)) {
             $rec['links'] = array_map(function($link) { return is_array($link) ? $link['uri'] : strval($link); }, (array)$rec['links']);
         }
 
         // convert invalid data
         if (isset($rec['attendees']) && !is_array($rec['attendees'])) {
             $rec['attendees'] = array();
         }
 
         if (!empty($rec['attendees'])) {
             foreach ((array) $rec['attendees'] as $i => $attendee) {
                 if (is_string($attendee['rsvp'])) {
                     $rec['attendees'][$i]['rsvp'] = $attendee['rsvp'] == 'true' || $attendee['rsvp'] == '1';
                 }
             }
         }
 
         // copy the task status to my attendee partstat
         if (!empty($rec['_reportpartstat'])) {
             if (($idx = $this->is_attendee($rec)) !== false) {
                 if (!($rec['_reportpartstat'] == 'NEEDS-ACTION' && $rec['attendees'][$idx]['status'] == 'ACCEPTED'))
                     $rec['attendees'][$idx]['status'] = $rec['_reportpartstat'];
                 else
                     unset($rec['_reportpartstat']);
             }
         }
 
         // set organizer from identity selector
         if ((isset($rec['_identity']) || (!empty($rec['attendees']) && empty($rec['organizer']))) &&
                 ($identity = $this->rc->user->get_identity($rec['_identity']))) {
             $rec['organizer'] = array('name' => $identity['name'], 'email' => $identity['email']);
         }
 
         if (is_numeric($rec['id']) && $rec['id'] < 0)
             unset($rec['id']);
 
         return $rec;
     }
 
     /**
      * Utility method to convert a tasks date/time values into a normalized format
      */
     private function normalize_dates(&$rec, $date_key, $time_key)
     {
         try {
             // parse date from user format (#2801)
             $date_format = $this->rc->config->get(empty($rec[$time_key]) ? 'date_format' : 'date_long', 'Y-m-d');
             $date = DateTime::createFromFormat($date_format, trim($rec[$date_key] . ' ' . $rec[$time_key]), $this->timezone);
 
             // fall back to default strtotime logic
             if (empty($date)) {
                 $date = new DateTime($rec[$date_key] . ' ' . $rec[$time_key], $this->timezone);
             }
 
             $rec[$date_key] = $date->format('Y-m-d');
             if (!empty($rec[$time_key]))
                 $rec[$time_key] = $date->format('H:i');
 
             return true;
         }
         catch (Exception $e) {
             $rec[$date_key] = $rec[$time_key] = null;
         }
 
         return false;
     }
 
     /**
      * Releases some resources after successful save
      */
     private function cleanup_task(&$rec)
     {
         // remove temp. attachment files
         if (!empty($_SESSION[self::SESSION_KEY]) && ($taskid = $_SESSION[self::SESSION_KEY]['id'])) {
             $this->rc->plugins->exec_hook('attachments_cleanup', array('group' => $taskid));
             $this->rc->session->remove(self::SESSION_KEY);
         }
     }
 
     /**
      * When flagging a recurring task as complete,
      * clone it and shift dates to the next occurrence
      */
     private function handle_recurrence(&$rec, $old)
     {
         $clone = null;
         if ($this->driver->is_complete($rec) && $old && !$this->driver->is_complete($old) && is_array($rec['recurrence'])) {
             $engine = libcalendaring::get_recurrence();
             $rrule = $rec['recurrence'];
             $updates = array();
 
             // compute the next occurrence of date attributes
             foreach (array('date'=>'time', 'startdate'=>'starttime') as $date_key => $time_key) {
                 if (empty($rec[$date_key]))
                     continue;
 
                 $date = new DateTime($rec[$date_key] . ' ' . $rec[$time_key], $this->timezone);
                 $engine->init($rrule, $date);
-                if ($next = $engine->next()) {
+                if ($next = $engine->next_start()) {
                     $updates[$date_key] = $next->format('Y-m-d');
                     if (!empty($rec[$time_key]))
                         $updates[$time_key] = $next->format('H:i');
                 }
             }
 
             // shift absolute alarm dates
             if (!empty($updates) && is_array($rec['valarms'])) {
                 $updates['valarms'] = array();
                 unset($rrule['UNTIL'], $rrule['COUNT']);  // make recurrence rule unlimited
 
                 foreach ($rec['valarms'] as $i => $alarm) {
                     if ($alarm['trigger'] instanceof DateTime) {
                         $engine->init($rrule, $alarm['trigger']);
-                        if ($next = $engine->next()) {
+                        if ($next = $engine->next_start()) {
                             $alarm['trigger'] = $next;
                         }
                     }
                     $updates['valarms'][$i] = $alarm;
                 }
             }
 
             if (!empty($updates)) {
                 // clone task to save a completed copy
                 $clone = $rec;
                 $clone['uid'] = $this->generate_uid();
                 $clone['parent_id'] = $rec['id'];
                 unset($clone['id'], $clone['recurrence'], $clone['attachments']);
 
                 // update the task but unset completed flag
                 $rec = array_merge($rec, $updates);
                 $rec['complete'] = $old['complete'];
                 $rec['status'] = $old['status'];
             }
         }
 
         return $clone;
     }
 
     /**
      * Send out an invitation/notification to all task attendees
      */
     private function notify_attendees($task, $old, $action = 'edit', $comment = null)
     {
         if ($action == 'delete' || ($task['status'] == 'CANCELLED' && $old['status'] != $task['status'])) {
             $task['cancelled'] = true;
             $is_cancelled      = true;
         }
 
         $itip   = $this->load_itip();
         $emails = $this->lib->get_user_emails();
         $itip_notify = (int)$this->rc->config->get('calendar_itip_send_option', 3);
 
         // add comment to the iTip attachment
         $task['comment'] = $comment;
 
         // needed to generate VTODO instead of VEVENT entry
         $task['_type'] = 'task';
 
         // compose multipart message using PEAR:Mail_Mime
         $method  = $action == 'delete' ? 'CANCEL' : 'REQUEST';
         $object = $this->to_libcal($task);
         $message = $itip->compose_itip_message($object, $method, $task['sequence'] > $old['sequence']);
 
         // list existing attendees from the $old task
         $old_attendees = array();
         foreach ((array)$old['attendees'] as $attendee) {
             $old_attendees[] = $attendee['email'];
         }
 
         // send to every attendee
         $sent = 0; $current = array();
         foreach ((array)$task['attendees'] as $attendee) {
             $current[] = strtolower($attendee['email']);
 
             // skip myself for obvious reasons
             if (!$attendee['email'] || in_array(strtolower($attendee['email']), $emails)) {
                 continue;
             }
 
             // skip if notification is disabled for this attendee
             if ($attendee['noreply'] && $itip_notify & 2) {
                 continue;
             }
 
             // skip if this attendee has delegated and set RSVP=FALSE
             if ($attendee['status'] == 'DELEGATED' && $attendee['rsvp'] === false) {
                 continue;
             }
 
             // which template to use for mail text
             $is_new   = !in_array($attendee['email'], $old_attendees);
             $is_rsvp  = $is_new || $task['sequence'] > $old['sequence'];
             $bodytext = $is_cancelled ? 'itipcancelmailbody' : ($is_new ? 'invitationmailbody' : 'itipupdatemailbody');
             $subject  = $is_cancelled ? 'itipcancelsubject'  : ($is_new ? 'invitationsubject' : ($task['title'] ? 'itipupdatesubject' : 'itipupdatesubjectempty'));
 
             // finally send the message
             if ($itip->send_itip_message($object, $method, $attendee, $subject, $bodytext, $message, $is_rsvp))
                 $sent++;
             else
                 $sent = -100;
         }
 
         // send CANCEL message to removed attendees
         foreach ((array)$old['attendees'] as $attendee) {
             if (!$attendee['email'] || in_array(strtolower($attendee['email']), $current)) {
                 continue;
             }
 
             $vtodo = $this->to_libcal($old);
             $vtodo['cancelled'] = $is_cancelled;
             $vtodo['attendees'] = array($attendee);
             $vtodo['comment']   = $comment;
 
             if ($itip->send_itip_message($vtodo, 'CANCEL', $attendee, 'itipcancelsubject', 'itipcancelmailbody'))
                 $sent++;
             else
                 $sent = -100;
         }
 
         return $sent;
     }
 
     /**
      * Compare two task objects and return differing properties
      *
      * @param array Event A
      * @param array Event B
      * @return array List of differing task properties
      */
     public static function task_diff($a, $b)
     {
         $diff   = array();
         $ignore = array('changed' => 1, 'attachments' => 1);
 
         foreach (array_unique(array_merge(array_keys($a), array_keys($b))) as $key) {
             if (!$ignore[$key] && $a[$key] != $b[$key])
                 $diff[] = $key;
         }
 
         // only compare number of attachments
         if (count($a['attachments']) != count($b['attachments']))
             $diff[] = 'attachments';
 
         return $diff;
     }
 
     /**
      * Dispatcher for tasklist actions initiated by the client
      */
     public function tasklist_action()
     {
         $action  = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $list    = rcube_utils::get_input_value('l', rcube_utils::INPUT_GPC, true);
         $success = false;
 
         unset($list['_token']);
 
         if (isset($list['showalarms'])) {
             $list['showalarms'] = intval($list['showalarms']);
         }
 
         switch ($action) {
         case 'form-new':
         case 'form-edit':
             $this->load_ui();
             echo $this->ui->tasklist_editform($action, $list);
             exit;
 
         case 'new':
             $list += array('showalarms' => true, 'active' => true, 'editable' => true);
             if ($insert_id = $this->driver->create_list($list)) {
                 $list['id'] = $insert_id;
                 if (empty($list['_reload'])) {
                     $this->load_ui();
                     $list['html'] = $this->ui->tasklist_list_item($insert_id, $list, $jsenv);
                     $list += (array)$jsenv[$insert_id];
                 }
                 $this->rc->output->command('plugin.insert_tasklist', $list);
                 $success = true;
             }
             break;
 
         case 'edit':
             if ($newid = $this->driver->edit_list($list)) {
                 $list['oldid'] = $list['id'];
                 $list['id'] = $newid;
                 $this->rc->output->command('plugin.update_tasklist', $list);
                 $success = true;
             }
             break;
 
         case 'subscribe':
             $success = $this->driver->subscribe_list($list);
             break;
 
         case 'delete':
             if (($success = $this->driver->delete_list($list)))
                 $this->rc->output->command('plugin.destroy_tasklist', $list);
             break;
 
         case 'search':
             $this->load_ui();
             $results = array();
             $query   = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
             $source  = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
 
             foreach ((array)$this->driver->search_lists($query, $source) as $id => $prop) {
                 $editname = $prop['editname'];
                 unset($prop['editname']);  // force full name to be displayed
                 $prop['active'] = false;
 
                 // let the UI generate HTML and CSS representation for this calendar
                 $html = $this->ui->tasklist_list_item($id, $prop, $jsenv);
                 $prop += (array)$jsenv[$id];
                 $prop['editname'] = $editname;
                 $prop['html'] = $html;
 
                 $results[] = $prop;
             }
             // report more results available
             if (!empty($this->driver->search_more_results)) {
                 $this->rc->output->show_message('autocompletemore', 'notice');
             }
 
             $this->rc->output->command('multi_thread_http_response', $results, rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC));
             return;
         }
 
         if ($success) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $this->rc->output->show_message('tasklist.errorsaving', 'error');
         }
 
         $this->rc->output->command('plugin.unlock_saving');
     }
 
     /**
      * Get counts for active tasks divided into different selectors
      */
     public function fetch_counts()
     {
         if (isset($_REQUEST['lists'])) {
             $lists = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);
         }
         else {
             foreach ($this->driver->get_lists() as $list) {
                 if (!empty($list['active'])) {
                     $lists[] = $list['id'];
                 }
             }
         }
         $counts = $this->driver->count_tasks($lists);
         $this->rc->output->command('plugin.update_counts', $counts);
     }
 
     /**
      * Adjust the cached counts after changing a task
      */
     public function update_counts($oldrec, $newrec)
     {
         // rebuild counts until this function is finally implemented
         $this->fetch_counts();
 
         // $this->rc->output->command('plugin.update_counts', $counts);
     }
 
     /**
      *
      */
     public function fetch_tasks()
     {
         $mask   = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $search = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
         $lists  = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);
         $filter = array('mask' => $mask, 'search' => $search);
 
         $data = $this->tasks_data($this->driver->list_tasks($filter, $lists));
 
         $this->rc->output->command('plugin.data_ready', array(
                 'filter' => $mask,
                 'lists'  => $lists,
                 'search' => $search,
                 'data'   => $data,
                 'tags'   => $this->driver->get_tags(),
         ));
     }
 
     /**
      * Handler for printing calendars
      */
     public function print_tasks()
     {
         // Add CSS stylesheets to the page header
         $skin_path = $this->local_skin_path();
 
         $this->include_stylesheet($skin_path . '/print.css');
         $this->include_script('tasklist.js');
 
         $this->rc->output->add_handlers(array(
             'plugin.tasklist_print' => array($this, 'print_tasks_list'),
         ));
 
         $this->rc->output->set_pagetitle($this->gettext('print'));
         $this->rc->output->send('tasklist.print');
     }
 
     /**
      * Handler for printing calendars
      */
     public function print_tasks_list($attrib)
     {
         $mask   = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $search = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
         $lists  = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);
         $filter = array('mask' => $mask, 'search' => $search);
 
         $data = $this->tasks_data($this->driver->list_tasks($filter, $lists));
 
         // we'll build the tasks table in javascript on page load
         // where we have sorting methods, etc.
         $this->rc->output->set_env('tasks', $data);
         $this->rc->output->set_env('filtermask', $mask);
 
         return $this->ui->tasks_resultview($attrib);
     }
 
     /**
      * Prepare and sort the given task records to be sent to the client
      */
     private function tasks_data($records)
     {
         $data = $this->task_tree = $this->task_titles = array();
 
         foreach ($records as $rec) {
             if (!empty($rec['parent_id'])) {
                 $this->task_tree[$rec['id']] = $rec['parent_id'];
             }
 
             $this->encode_task($rec);
 
             $data[] = $rec;
         }
 
         // assign hierarchy level indicators for later sorting
         array_walk($data, array($this, 'task_walk_tree'));
 
         return $data;
     }
 
     /**
      * Prepare the given task record before sending it to the client
      */
     private function encode_task(&$rec)
     {
         $rec['mask'] = $this->filter_mask($rec);
         $rec['flagged'] = intval($rec['flagged']);
         $rec['complete'] = floatval($rec['complete']);
 
         if (is_object($rec['created'])) {
             $rec['created_'] = $this->rc->format_date($rec['created']);
             $rec['created'] = $rec['created']->format('U');
         }
         if (is_object($rec['changed'])) {
             $rec['changed_'] = $this->rc->format_date($rec['changed']);
             $rec['changed'] = $rec['changed']->format('U');
         }
         else {
             $rec['changed'] = null;
         }
 
         if ($rec['date']) {
             try {
                 $date = new DateTime($rec['date'] . ' ' . $rec['time'], $this->timezone);
                 $rec['datetime'] = intval($date->format('U'));
                 $rec['date'] = $date->format($this->rc->config->get('date_format', 'Y-m-d'));
                 $rec['_hasdate'] = 1;
             }
             catch (Exception $e) {
                 $rec['date'] = $rec['datetime'] = null;
             }
         }
         else {
             $rec['date'] = $rec['datetime'] = null;
             $rec['_hasdate'] = 0;
         }
 
         if ($rec['startdate']) {
             try {
                 $date = new DateTime($rec['startdate'] . ' ' . $rec['starttime'], $this->timezone);
                 $rec['startdatetime'] = intval($date->format('U'));
                 $rec['startdate'] = $date->format($this->rc->config->get('date_format', 'Y-m-d'));
             }
             catch (Exception $e) {
                 $rec['startdate'] = $rec['startdatetime'] = null;
             }
         }
 
         if (!empty($rec['valarms'])) {
             $rec['alarms_text'] = libcalendaring::alarms_text($rec['valarms']);
             $rec['valarms'] = libcalendaring::to_client_alarms($rec['valarms']);
         }
 
         if (!empty($rec['recurrence'])) {
             $rec['recurrence_text'] = $this->lib->recurrence_text($rec['recurrence']);
             $rec['recurrence'] = $this->lib->to_client_recurrence($rec['recurrence'], $rec['time'] || $rec['starttime']);
         }
 
         if (!empty($rec['attachments'])) {
             foreach ((array) $rec['attachments'] as $k => $attachment) {
                 $rec['attachments'][$k]['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
             }
         }
 
         // convert link URIs references into structs
         if (array_key_exists('links', $rec)) {
             foreach ((array) $rec['links'] as $i => $link) {
                 if (strpos($link, 'imap://') === 0 && ($msgref = $this->driver->get_message_reference($link, 'task'))) {
                     $rec['links'][$i] = $msgref;
                 }
             }
         }
 
         // Convert HTML description into plain text
         if ($this->is_html($rec)) {
             $h2t = new rcube_html2text($rec['description'], false, true, 0);
             $rec['description'] = $h2t->get_text();
         }
 
         if (!is_array($rec['tags']))
             $rec['tags'] = (array)$rec['tags'];
         sort($rec['tags'], SORT_LOCALE_STRING);
 
         if (in_array($rec['id'], $this->collapsed_tasks))
           $rec['collapsed'] = true;
 
         if (empty($rec['parent_id']))
             $rec['parent_id'] = null;
 
         $this->task_titles[$rec['id']] = $rec['title'];
     }
 
     /**
      * Determine whether the given task description is HTML formatted
      */
     private function is_html($task)
     {
         // check for opening and closing <html> or <body> tags
         return (preg_match('/<(html|body)(\s+[a-z]|>)/', $task['description'], $m) && strpos($task['description'], '</'.$m[1].'>') > 0);
     }
 
     /**
      * Callback function for array_walk over all tasks.
      * Sets tree depth and parent titles
      */
     private function task_walk_tree(&$rec)
     {
         $rec['_depth'] = 0;
         $parent_titles = array();
         $parent_id = isset($this->task_tree[$rec['id']]) ? $this->task_tree[$rec['id']] : null;
         while ($parent_id) {
             $rec['_depth']++;
             if (isset($this->task_titles[$parent_id])) {
                 array_unshift($parent_titles, $this->task_titles[$parent_id]);
             }
             $parent_id = isset($this->task_tree[$parent_id]) ? $this->task_tree[$parent_id] : null;
         }
 
         if (count($parent_titles)) {
             $rec['parent_title'] = join(' » ', array_filter($parent_titles));
         }
     }
 
     /**
      * Compute the filter mask of the given task
      *
      * @param array Hash array with Task record properties
      * @return int Filter mask
      */
     public function filter_mask($rec)
     {
         static $today, $today_date, $tomorrow, $weeklimit;
 
         if (!$today) {
             $today_date    = new DateTime('now', $this->timezone);
             $today         = $today_date->format('Y-m-d');
             $tomorrow_date = new DateTime('now + 1 day', $this->timezone);
             $tomorrow      = $tomorrow_date->format('Y-m-d');
 
             // In Kolab-mode we hide "Next 7 days" filter, which means
             // "Later" should catch tasks with date after tomorrow (#5353)
             if ($this->rc->output->get_env('tasklist_driver') == 'kolab') {
                 $weeklimit = $tomorrow;
             }
             else {
                 $week_date = new DateTime('now + 7 days', $this->timezone);
                 $weeklimit = $week_date->format('Y-m-d');
             }
         }
 
         $mask    = 0;
         $start   = $rec['startdate'] ?: '1900-00-00';
         $duedate = $rec['date'] ?: '3000-00-00';
 
         if ($rec['flagged'])
             $mask |= self::FILTER_MASK_FLAGGED;
         if ($this->driver->is_complete($rec))
             $mask |= self::FILTER_MASK_COMPLETE;
 
         if (empty($rec['date']))
             $mask |= self::FILTER_MASK_NODATE;
         else if ($rec['date'] < $today)
             $mask |= self::FILTER_MASK_OVERDUE;
 
         if (empty($rec['recurrence']) || $duedate < $today || $start > $weeklimit) {
             if ($duedate <= $today || ($rec['startdate'] && $start <= $today))
                 $mask |= self::FILTER_MASK_TODAY;
             else if (($start > $today && $start <= $tomorrow) || ($duedate > $today && $duedate <= $tomorrow))
                 $mask |= self::FILTER_MASK_TOMORROW;
             else if (($start > $tomorrow && $start <= $weeklimit) || ($duedate > $tomorrow && $duedate <= $weeklimit))
                 $mask |= self::FILTER_MASK_WEEK;
             else if ($start > $weeklimit || $duedate > $weeklimit)
                 $mask |= self::FILTER_MASK_LATER;
         }
         else if ($rec['startdate'] || $rec['date']) {
             $date = new DateTime($rec['startdate'] ?: $rec['date'], $this->timezone);
 
             // set safe recurrence start
             while ($date->format('Y-m-d') >= $today) {
                 switch ($rec['recurrence']['FREQ']) {
                     case 'DAILY':
                         $date = clone $today_date;
                         $date->sub(new DateInterval('P1D'));
                         break;
                     case 'WEEKLY': $date->sub(new DateInterval('P7D')); break;
                     case 'MONTHLY': $date->sub(new DateInterval('P1M')); break;
                     case 'YEARLY': $date->sub(new DateInterval('P1Y')); break;
                     default; break 2;
                 }
             }
 
             $date->_dateonly = true;
 
             $engine = libcalendaring::get_recurrence();
             $engine->init($rec['recurrence'], $date);
 
             // check task occurrences (stop next week)
             // FIXME: is there a faster way of doing this?
-            while ($date = $engine->next()) {
+            while ($date = $engine->next_start()) {
                 $date = $date->format('Y-m-d');
 
                 // break iteration asap
                 if ($date > $duedate || ($mask & self::FILTER_MASK_LATER)) {
                     break;
                 }
 
                 if ($date == $today) {
                     $mask |= self::FILTER_MASK_TODAY;
                 }
                 else if ($date == $tomorrow) {
                     $mask |= self::FILTER_MASK_TOMORROW;
                 }
                 else if ($date > $tomorrow && $date <= $weeklimit) {
                     $mask |= self::FILTER_MASK_WEEK;
                 }
                 else if ($date > $weeklimit) {
                     $mask |= self::FILTER_MASK_LATER;
                     break;
                 }
             }
         }
 
         // add masks for assigned tasks
         if ($this->is_organizer($rec) && !empty($rec['attendees']) && $this->is_attendee($rec) === false)
             $mask |= self::FILTER_MASK_ASSIGNED;
         else if (/*empty($rec['attendees']) ||*/ $this->is_attendee($rec) !== false)
             $mask |= self::FILTER_MASK_MYTASKS;
 
         return $mask;
     }
 
     /**
      * Determine whether the current user is an attendee of the given task
      */
     public function is_attendee($task)
     {
         $emails = $this->lib->get_user_emails();
         foreach ((array)$task['attendees'] as $i => $attendee) {
             if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                 return $i;
             }
         }
 
         return false;
     }
 
     /**
      * Determine whether the current user is the organizer of the given task
      */
     public function is_organizer($task)
     {
         $emails = $this->lib->get_user_emails();
         return (empty($task['organizer']) || in_array(strtolower($task['organizer']['email']), $emails));
     }
 
 
     /*******  UI functions  ********/
 
     /**
      * Render main view of the tasklist task
      */
     public function tasklist_view()
     {
         $this->ui->init();
         $this->ui->init_templates();
 
         // set autocompletion env
         $this->rc->output->set_env('autocomplete_threads', (int)$this->rc->config->get('autocomplete_threads', 0));
         $this->rc->output->set_env('autocomplete_max', (int)$this->rc->config->get('autocomplete_max', 15));
         $this->rc->output->set_env('autocomplete_min_length', $this->rc->config->get('autocomplete_min_length'));
         $this->rc->output->add_label('autocompletechars', 'autocompletemore', 'delete', 'close');
 
         $this->rc->output->set_pagetitle($this->gettext('navtitle'));
         $this->rc->output->send('tasklist.mainview');
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for updated data in active lists and sync them to the client
      */
     public function refresh($attr)
     {
         // refresh the entire list every 10th time to also sync deleted items
         if (rand(0,10) == 10) {
             $this->rc->output->command('plugin.reload_data');
             return;
         }
 
         $filter = array(
             'since'  => $attr['last'],
             'search' => rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC),
             'mask'   => intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC)) & self::FILTER_MASK_COMPLETE,
         );
         $lists = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);;
 
         $updates = $this->driver->list_tasks($filter, $lists);
         if (!empty($updates)) {
             $this->rc->output->command('plugin.refresh_tasks', $this->tasks_data($updates), true);
 
             // update counts
             $counts = $this->driver->count_tasks($lists);
             $this->rc->output->command('plugin.update_counts', $counts);
         }
     }
 
     /**
      * Handler for pending_alarms plugin hook triggered by the calendar module on keep-alive requests.
      * This will check for pending notifications and pass them to the client
      */
     public function pending_alarms($p)
     {
         $this->load_driver();
         if ($alarms = $this->driver->pending_alarms($p['time'] ?: time())) {
             foreach ($alarms as $alarm) {
                 // encode alarm object to suit the expectations of the calendaring code
                 if ($alarm['date'])
                     $alarm['start'] = new DateTime($alarm['date'].' '.$alarm['time'], $this->timezone);
 
                 $alarm['id'] = 'task:' . $alarm['id'];  // prefix ID with task:
                 $alarm['allday'] = empty($alarm['time']) ? 1 : 0;
                 $p['alarms'][] = $alarm;
             }
         }
 
         return $p;
     }
 
     /**
      * Handler for alarm dismiss hook triggered by the calendar module
      */
     public function dismiss_alarms($p)
     {
         $this->load_driver();
         foreach ((array)$p['ids'] as $id) {
             if (strpos($id, 'task:') === 0)
                 $p['success'] |= $this->driver->dismiss_alarm(substr($id, 5), $p['snooze']);
         }
 
         return $p;
     }
 
     /**
      * Handler for importing .ics files
      */
     function import_tasks()
     {
         // Upload progress update
         if (!empty($_GET['_progress'])) {
             $this->rc->upload_progress();
         }
 
         @set_time_limit(0);
 
         // process uploaded file if there is no error
         $err = $_FILES['_data']['error'];
 
         if (!$err && $_FILES['_data']['tmp_name']) {
             $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
             $lists  = $this->driver->get_lists();
             $list   = $lists[$source] ?: $this->get_default_tasklist();
             $source = $list['id'];
 
             // extract zip file
             if ($_FILES['_data']['type'] == 'application/zip') {
                 $count = 0;
                 if (class_exists('ZipArchive', false)) {
                     $zip = new ZipArchive();
                     if ($zip->open($_FILES['_data']['tmp_name'])) {
                         $randname = uniqid('zip-' . session_id(), true);
                         $tmpdir   = slashify($this->rc->config->get('temp_dir', sys_get_temp_dir())) . $randname;
                         mkdir($tmpdir, 0700);
 
                         // extract each ical file from the archive and import it
                         for ($i = 0; $i < $zip->numFiles; $i++) { 
                             $filename = $zip->getNameIndex($i);
                             if (preg_match('/\.ics$/i', $filename)) {
                                 $tmpfile = $tmpdir . '/' . basename($filename);
                                 if (copy('zip://' . $_FILES['_data']['tmp_name'] . '#'.$filename, $tmpfile)) {
                                     $count += $this->import_from_file($tmpfile, $source, $errors);
                                     unlink($tmpfile);
                                 }
                             }
                         }
 
                         rmdir($tmpdir);
                         $zip->close();
                     }
                     else {
                         $errors = 1;
                         $msg = 'Failed to open zip file.';
                     }
                 }
                 else {
                     $errors = 1;
                     $msg = 'Zip files are not supported for import.';
                 }
             }
             else {
                 // attempt to import the uploaded file directly
                 $count = $this->import_from_file($_FILES['_data']['tmp_name'], $source, $errors);
             }
 
             if ($count) {
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'importsuccess', 'vars' => array('nr' => $count))), 'confirmation');
                 $this->rc->output->command('plugin.import_success', array('source' => $source, 'refetch' => true));
             }
             else if (!$errors) {
                 $this->rc->output->command('display_message', $this->gettext('importnone'), 'notice');
                 $this->rc->output->command('plugin.import_success', array('source' => $source));
             }
             else {
                 $this->rc->output->command('plugin.import_error', array('message' => $this->gettext('importerror') . ($msg ? ': ' . $msg : '')));
             }
         }
         else {
             if ($err == UPLOAD_ERR_INI_SIZE || $err == UPLOAD_ERR_FORM_SIZE) {
                 $msg = $this->rc->gettext(array('name' => 'filesizeerror', 'vars' => array(
                     'size' => $this->rc->show_bytes(parse_bytes(ini_get('upload_max_filesize'))))));
             }
             else {
                 $msg = $this->rc->gettext('fileuploaderror');
             }
 
             $this->rc->output->command('plugin.import_error', array('message' => $msg));
         }
 
         $this->rc->output->send('iframe');
     }
 
     /**
      * Helper function to parse and import a single .ics file
      */
     private function import_from_file($filepath, $source, &$errors)
     {
         $user_email = $this->rc->user->get_username();
         $ical       = $this->get_ical();
         $errors     = !$ical->fopen($filepath);
         $count      = $i = 0;
 
         foreach ($ical as $task) {
             // keep the browser connection alive on long import jobs
             if (++$i > 100 && $i % 100 == 0) {
                 echo "<!-- -->";
                 ob_flush();
             }
 
             if ($task['_type'] == 'task') {
                 $task['list'] = $source;
 
                 if ($this->driver->create_task($task)) {
                     $count++;
                 }
                 else {
                     $errors++;
                 }
             }
         }
 
         return $count;
     }
 
     /**
      * Construct the ics file for exporting tasks to iCalendar format
      */
     function export_tasks()
     {
         $source      = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
         $task_id     = rcube_utils::get_input_value('id', rcube_utils::INPUT_GPC);
         $attachments = (bool) rcube_utils::get_input_value('attachments', rcube_utils::INPUT_GPC);
 
         $this->load_driver();
 
         $browser = new rcube_browser;
         $lists   = $this->driver->get_lists();
         $tasks   = array();
         $filter  = array();
 
         // get message UIDs for filter
         if ($source && ($list = $lists[$source])) {
             $filename = html_entity_decode($list['name']) ?: $sorce;
             $filter   = array($source => true);
         }
         else if ($task_id) {
             $filename = 'tasks';
             foreach (explode(',', $task_id) as $id) {
                 list($list_id, $task_id) = explode(':', $id, 2);
                 if ($list_id && $task_id) {
                     $filter[$list_id][] = $task_id;
                 }
             }
         }
 
         // Get tasks
         foreach ($filter as $list_id => $uids) {
             $_filter = is_array($uids) ? array('uid' => $uids) : null;
             $_tasks  = $this->driver->list_tasks($_filter, $list_id);
             if (!empty($_tasks)) {
                 $tasks = array_merge($tasks, $_tasks);
             }
         }
 
         // Set file name
         if ($source && count($tasks) == 1) {
             $filename = $tasks[0]['title'] ?: 'task';
         }
         $filename .= '.ics';
         $filename = $browser->ie ? rawurlencode($filename) : addcslashes($filename, '"');
 
         $tasks = array_map(array($this, 'to_libcal'), $tasks);
 
         // Give plugins a possibility to implement other output formats or modify the result
         $plugin = $this->rc->plugins->exec_hook('tasks_export', array(
                 'result'      => $tasks,
                 'attachments' => $attachments,
                 'filename'    => $filename,
                 'plugin'      => $this,
         ));
 
         if ($plugin['abort']) {
             exit;
         }
 
         $this->rc->output->nocacheing_headers();
 
         // don't kill the connection if download takes more than 30 sec.
         @set_time_limit(0);
         header("Content-Type: text/calendar");
         header("Content-Disposition: inline; filename=\"". $plugin['filename'] ."\"");
 
         $this->get_ical()->export($plugin['result'], '', true,
             !empty($plugin['attachments']) ? array($this->driver, 'get_attachment_body') : null);
         exit;
     }
 
 
     /******* Attachment handling  *******/
 
     /**
      * Handler for attachments upload
     */
     public function attachment_upload()
     {
         $handler = new kolab_attachments_handler();
         $handler->attachment_upload(self::SESSION_KEY);
     }
 
     /**
      * Handler for attachments download/displaying
      */
     public function attachment_get()
     {
         $handler = new kolab_attachments_handler();
 
         // show loading page
         if (!empty($_GET['_preload'])) {
             return $handler->attachment_loading_page();
         }
 
         $task = rcube_utils::get_input_value('_t', rcube_utils::INPUT_GPC);
         $list = rcube_utils::get_input_value('_list', rcube_utils::INPUT_GPC);
         $id   = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
         $rev  = rcube_utils::get_input_value('_rev', rcube_utils::INPUT_GPC);
 
         $task       = array('id' => $task, 'list' => $list, 'rev' => $rev);
         $attachment = $this->driver->get_attachment($id, $task);
 
         // show part page
         if (!empty($_GET['_frame'])) {
             $handler->attachment_page($attachment);
         }
         // deliver attachment content
         else if ($attachment) {
             $attachment['body'] = $this->driver->get_attachment_body($id, $task);
             $handler->attachment_get($attachment);
         }
 
         // if we arrive here, the requested part was not found
         header('HTTP/1.1 404 Not Found');
         exit;
     }
 
 
     /*******  Email related function *******/
 
     public function mail_message2task()
     {
         $this->load_ui();
         $this->ui->init();
         $this->ui->init_templates();
         $this->ui->tasklists();
 
         $uid  = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GET);
         $mbox = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_GET);
         $task = array();
 
         $imap    = $this->rc->get_storage();
         $message = new rcube_message($uid, $mbox);
 
         if ($message->headers) {
             $task['title']       = trim($message->subject);
             $task['description'] = trim($message->first_text_part());
             $task['id']          = -$uid;
 
             $this->load_driver();
 
             // add a reference to the email message
             if ($msgref = $this->driver->get_message_reference($message->headers, $mbox)) {
                 $task['links'] = array($msgref);
             }
             // copy mail attachments to task
             else if ($message->attachments && $this->driver->attachments) {
                 if (!is_array($_SESSION[self::SESSION_KEY]) || $_SESSION[self::SESSION_KEY]['id'] != $task['id']) {
                     $_SESSION[self::SESSION_KEY] = array(
                         'id'          => $task['id'],
                         'attachments' => array(),
                     );
                 }
 
                 foreach ((array)$message->attachments as $part) {
                     $attachment = array(
                         'data'     => $imap->get_message_part($uid, $part->mime_id, $part),
                         'size'     => $part->size,
                         'name'     => $part->filename,
                         'mimetype' => $part->mimetype,
                         'group'    => $task['id'],
                     );
 
                     $attachment = $this->rc->plugins->exec_hook('attachment_save', $attachment);
 
                     if ($attachment['status'] && !$attachment['abort']) {
                         $id = $attachment['id'];
                         $attachment['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
                         // store new attachment in session
                         unset($attachment['status'], $attachment['abort'], $attachment['data']);
                         $_SESSION[self::SESSION_KEY]['attachments'][$id] = $attachment;
 
                         $attachment['id'] = 'rcmfile' . $attachment['id'];  // add prefix to consider it 'new'
                         $task['attachments'][] = $attachment;
                     }
                 }
             }
 
             $this->rc->output->set_env('task_prop', $task);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
         }
 
         $this->rc->output->send('tasklist.dialog');
     }
 
     /**
      * Add UI element to copy task invitations or updates to the tasklist
      */
     public function mail_messagebody_html($p)
     {
         // load iCalendar functions (if necessary)
         if (!empty($this->lib->ical_parts)) {
             $this->get_ical();
             $this->load_itip();
         }
 
         $html = '';
         $has_tasks = false;
         $ical_objects = $this->lib->get_mail_ical_objects();
 
         // show a box for every task in the file
         foreach ($ical_objects as $idx => $task) {
             if ($task['_type'] != 'task') {
                 continue;
             }
 
             $has_tasks = true;
 
             // get prepared inline UI for this event object
             if ($ical_objects->method) {
                 $html .= html::div('tasklist-invitebox invitebox boxinformation',
                     $this->itip->mail_itip_inline_ui(
                         $task,
                         $ical_objects->method,
                         $ical_objects->mime_id . ':' . $idx,
                         'tasks',
                         rcube_utils::anytodatetime($ical_objects->message_date)
                     )
                 );
             }
 
             // limit listing
             if ($idx >= 3) {
                 break;
             }
         }
 
         // list linked tasks
         $links = array();
         foreach ($this->message_tasks as $task) {
             $checkbox = new html_checkbox(array(
                 'name' => 'completed',
                 'class' => 'complete pretty-checkbox',
                 'title' => $this->gettext('complete'),
                 'data-list' => $task['list'],
             ));
             $complete = $this->driver->is_complete($task);
             $links[] = html::tag('li', 'messagetaskref' . ($complete ? ' complete' : ''),
                 $checkbox->show($complete ? $task['id'] : null, array('value' => $task['id'])) . ' ' .
                 html::a(array(
                     'href' => $this->rc->url(array(
                         'task' => 'tasks',
                         'list' => $task['list'],
                         'id' => $task['id'],
                     )),
                     'class' => 'messagetasklink',
                     'rel' => $task['id'] . '@' . $task['list'],
                     'target' => '_blank',
                 ), rcube::Q($task['title']))
             );
         }
         if (count($links)) {
             $html .= html::div('messagetasklinks boxinformation', html::tag('ul', 'tasklist', join("\n", $links)));
         }
 
         // prepend iTip/relation boxes to message body
         if ($html) {
             $this->load_ui();
             $this->ui->init();
 
             $p['content'] = $html . $p['content'];
 
             $this->rc->output->add_label('tasklist.savingdata','tasklist.deletetaskconfirm','tasklist.declinedeleteconfirm');
         }
 
         // add "Save to tasks" button into attachment menu
         if ($has_tasks) {
             $this->add_button(array(
                 'id'         => 'attachmentsavetask',
                 'name'       => 'attachmentsavetask',
                 'type'       => 'link',
                 'wrapper'    => 'li',
                 'command'    => 'attachment-save-task',
                 'class'      => 'icon tasklistlink disabled',
                 'classact'   => 'icon tasklistlink active',
                 'innerclass' => 'icon taskadd',
                 'label'      => 'tasklist.savetotasklist',
             ), 'attachmentmenu');
         }
 
         return $p;
     }
 
     /**
      * Lookup backend storage and find notes associated with the given message
      */
     public function mail_message_load($p)
     {
         if (empty($p['object']->headers->others['x-kolab-type'])) {
             $this->load_driver();
             $this->message_tasks = $this->driver->get_message_related_tasks($p['object']->headers, $p['object']->folder);
 
             // sort message tasks by completeness and due date
             $driver = $this->driver;
             array_walk($this->message_tasks, array($this, 'encode_task'));
             usort($this->message_tasks, function($a, $b) use ($driver) {
                 $a_complete = intval($driver->is_complete($a));
                 $b_complete = intval($driver->is_complete($b));
                 $d = $a_complete - $b_complete;
                 if (!$d) $d = $b['_hasdate'] - $a['_hasdate'];
                 if (!$d) $d = $a['datetime'] - $b['datetime'];
                 return $d;
             });
         }
     }
 
     /**
      * Load iCalendar functions
      */
     public function get_ical()
     {
         if (empty($this->ical)) {
             $this->ical = libcalendaring::get_ical();
         }
 
         return $this->ical;
     }
 
     /**
      * Get properties of the tasklist this user has specified as default
      */
     public function get_default_tasklist($lists = null)
     {
         if ($lists === null) {
             $lists = $this->driver->get_lists(tasklist_driver::FILTER_PERSONAL | tasklist_driver::FILTER_WRITEABLE);
         }
 
         $list = null;
 
         foreach ($lists as $l) {
             if ($l['default']) {
                 $list = $l;
             }
 
             if ($l['editable']) {
                 $first = $l;
             }
         }
 
         return $list ?: $first;
     }
 
     /**
      * Import the full payload from a mail message attachment
      */
     public function mail_import_attachment()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             $part    = $imap->get_message_part($uid, $mime_id);
 //            $headers = $imap->get_message_headers($uid);
 
             if ($part->ctype_parameters['charset']) {
                 $charset = $part->ctype_parameters['charset'];
             }
 
             if ($part) {
                 $tasks = $this->get_ical()->import($part, $charset);
             }
         }
 
         $success = $existing = 0;
 
         if (!empty($tasks)) {
             // find writeable tasklist to store task
             $cal_id = !empty($_REQUEST['_list']) ? rcube_utils::get_input_value('_list', rcube_utils::INPUT_POST) : null;
             $lists  = $this->driver->get_lists();
 
             foreach ($tasks as $task) {
                 // save to tasklist
                 $list   = $lists[$cal_id] ?: $this->get_default_tasklist();
                 if ($list && $list['editable'] && $task['_type'] == 'task') {
                     $task = $this->from_ical($task);
                     $task['list'] = $list['id'];
 
                     if (!$this->driver->get_task($task['uid'])) {
                         $success += (bool) $this->driver->create_task($task);
                     }
                     else {
                         $existing++;
                     }
                 }
             }
         }
 
         if ($success) {
             $this->rc->output->command('display_message', $this->gettext(array(
                 'name' => 'importsuccess',
                 'vars' => array('nr' => $success),
             )), 'confirmation');
         }
         else if ($existing) {
             $this->rc->output->command('display_message', $this->gettext('importwarningexists'), 'warning');
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('errorimportingtask'), 'error');
         }
     }
 
     /**
      * Handler for POST request to import an event attached to a mail message
      */
     public function mail_import_itip()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $status  = rcube_utils::get_input_value('_status', rcube_utils::INPUT_POST);
         $comment = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
         $delete  = intval(rcube_utils::get_input_value('_del', rcube_utils::INPUT_POST));
         $noreply = intval(rcube_utils::get_input_value('_noreply', rcube_utils::INPUT_POST)) || $status == 'needs-action';
 
         $error_msg = $this->gettext('errorimportingtask');
         $success   = false;
 
         if ($status == 'delegated') {
             $delegates = rcube_mime::decode_address_list(rcube_utils::get_input_value('_to', rcube_utils::INPUT_POST, true), 1, false);
             $delegate  = reset($delegates);
 
             if (empty($delegate) || empty($delegate['mailto'])) {
                 $this->rc->output->command('display_message', $this->gettext('libcalendaring.delegateinvalidaddress'), 'error');
                 return;
             }
         }
 
         // successfully parsed tasks?
         if ($task = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'task')) {
             $task = $this->from_ical($task);
 
             // forward iTip request to delegatee
             if ($delegate) {
                 $rsvpme = rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST);
                 $itip   = $this->load_itip();
 
                 $task['comment'] = $comment;
 
                 if ($itip->delegate_to($task, $delegate, !empty($rsvpme))) {
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
 
                 unset($task['comment']);
             }
 
             $mode = tasklist_driver::FILTER_PERSONAL
                 | tasklist_driver::FILTER_SHARED
                 | tasklist_driver::FILTER_WRITEABLE;
 
             // find writeable list to store the task
             $list_id = !empty($_REQUEST['_folder']) ? rcube_utils::get_input_value('_folder', rcube_utils::INPUT_POST) : null;
             $lists   = $this->driver->get_lists($mode);
             $list    = $lists[$list_id];
             $dontsave = ($_REQUEST['_folder'] === '' && $task['_method'] == 'REQUEST');
 
             // select default list except user explicitly selected 'none'
             if (!$list && !$dontsave) {
                 $list = $this->get_default_tasklist($lists);
             }
 
             $metadata = array(
                 'uid'      => $task['uid'],
                 'changed'  => is_object($task['changed']) ? $task['changed']->format('U') : 0,
                 'sequence' => intval($task['sequence']),
                 'fallback' => strtoupper($status),
                 'method'   => $task['_method'],
                 'task'     => 'tasks',
             );
 
             // update my attendee status according to submitted method
             if (!empty($status)) {
                 $organizer = $task['organizer'];
                 $emails    = $this->lib->get_user_emails();
 
                 foreach ($task['attendees'] as $i => $attendee) {
                     if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                         $metadata['attendee'] = $attendee['email'];
                         $metadata['rsvp']     = $attendee['role'] != 'NON-PARTICIPANT';
                         $reply_sender         = $attendee['email'];
 
                         $task['attendees'][$i]['status'] = strtoupper($status);
                         if (!in_array($task['attendees'][$i]['status'], array('NEEDS-ACTION','DELEGATED'))) {
                             $task['attendees'][$i]['rsvp'] = false;  // unset RSVP attribute
                         }
                     }
                 }
 
                 // add attendee with this user's default identity if not listed
                 if (!$reply_sender) {
                     $sender_identity = $this->rc->user->list_emails(true);
                     $task['attendees'][] = array(
                         'name'   => $sender_identity['name'],
                         'email'  => $sender_identity['email'],
                         'role'   => 'OPT-PARTICIPANT',
                         'status' => strtoupper($status),
                     );
                     $metadata['attendee'] = $sender_identity['email'];
                 }
             }
 
             // save to tasklist
             if ($list && $list['editable']) {
                 $task['list'] = $list['id'];
 
                 // check for existing task with the same UID
                 $existing = $this->find_task($task['uid'], $mode);
 
                 if ($existing) {
                     // only update attendee status
                     if ($task['_method'] == 'REPLY') {
                         // try to identify the attendee using the email sender address
                         $existing_attendee = -1;
                         $existing_attendee_emails = array();
                         foreach ($existing['attendees'] as $i => $attendee) {
                             $existing_attendee_emails[] = $attendee['email'];
                             if ($task['_sender'] && ($attendee['email'] == $task['_sender'] || $attendee['email'] == $task['_sender_utf'])) {
                                 $existing_attendee = $i;
                             }
                         }
 
                         $task_attendee = null;
                         foreach ($task['attendees'] as $attendee) {
                             if ($task['_sender'] && ($attendee['email'] == $task['_sender'] || $attendee['email'] == $task['_sender_utf'])) {
                                 $task_attendee        = $attendee;
                                 $metadata['fallback'] = $attendee['status'];
                                 $metadata['attendee'] = $attendee['email'];
                                 $metadata['rsvp']     = $attendee['rsvp'] || $attendee['role'] != 'NON-PARTICIPANT';
                                 if ($attendee['status'] != 'DELEGATED') {
                                     break;
                                 }
                             }
                             // also copy delegate attendee
                             else if (!empty($attendee['delegated-from']) &&
                                      (stripos($attendee['delegated-from'], $task['_sender']) !== false || stripos($attendee['delegated-from'], $task['_sender_utf']) !== false) &&
                                      (!in_array($attendee['email'], $existing_attendee_emails))) {
                                 $existing['attendees'][] = $attendee;
                             }
                         }
 
                         // if delegatee has declined, set delegator's RSVP=True
                         if ($task_attendee && $task_attendee['status'] == 'DECLINED' && $task_attendee['delegated-from']) {
                             foreach ($existing['attendees'] as $i => $attendee) {
                                 if ($attendee['email'] == $task_attendee['delegated-from']) {
                                     $existing['attendees'][$i]['rsvp'] = true;
                                     break;
                                 }
                             }
                         }
 
                         // found matching attendee entry in both existing and new events
                         if ($existing_attendee >= 0 && $task_attendee) {
                             $existing['attendees'][$existing_attendee] = $task_attendee;
                             $success = $this->driver->edit_task($existing);
                         }
                         // update the entire attendees block
                         else if (($task['sequence'] >= $existing['sequence'] || $task['changed'] >= $existing['changed']) && $task_attendee) {
                             $existing['attendees'][] = $task_attendee;
                             $success = $this->driver->edit_task($existing);
                         }
                         else {
                             $error_msg = $this->gettext('newerversionexists');
                         }
                     }
                     // delete the task when declined
                     else if ($status == 'declined' && $delete) {
                         $deleted = $this->driver->delete_task($existing, true);
                         $success = true;
                     }
                     // import the (newer) task
                     else if ($task['sequence'] >= $existing['sequence'] || $task['changed'] >= $existing['changed']) {
                         $task['id']   = $existing['id'];
                         $task['list'] = $existing['list'];
 
                         // preserve my participant status for regular updates
                         if (empty($status)) {
                             $this->lib->merge_attendees($task, $existing);
                         }
 
                         // set status=CANCELLED on CANCEL messages
                         if ($task['_method'] == 'CANCEL') {
                             $task['status'] = 'CANCELLED';
                         }
 
                         // update attachments list, allow attachments update only on REQUEST (#5342)
                         if ($task['_method'] == 'REQUEST') {
                             $task['deleted_attachments'] = true;
                         }
                         else {
                             unset($task['attachments']);
                         }
 
                         // show me as free when declined (#1670)
                         if ($status == 'declined' || $task['status'] == 'CANCELLED') {
                             $task['free_busy'] = 'free';
                         }
 
                         $success = $this->driver->edit_task($task);
                     }
                     else if (!empty($status)) {
                         $existing['attendees'] = $task['attendees'];
                         if ($status == 'declined') { // show me as free when declined (#1670)
                             $existing['free_busy'] = 'free';
                         }
 
                         $success = $this->driver->edit_event($existing);
                     }
                     else {
                         $error_msg = $this->gettext('newerversionexists');
                     }
                 }
                 else if (!$existing && ($status != 'declined' || $this->rc->config->get('kolab_invitation_tasklists'))) {
                     $success = $this->driver->create_task($task);
                 }
                 else if ($status == 'declined') {
                     $error_msg = null;
                 }
             }
             else if ($status == 'declined' || $dontsave) {
                 $error_msg = null;
             }
             else {
                 $error_msg = $this->gettext('nowritetasklistfound');
             }
         }
 
         if ($success || $dontsave) {
             if ($success) {
                 $message = $task['_method'] == 'REPLY' ? 'attendeupdateesuccess' : ($deleted ? 'successremoval' : ($existing ? 'updatedsuccessfully' : 'importedsuccessfully'));
                 $this->rc->output->command('display_message', $this->gettext(array('name' => $message, 'vars' => array('list' => $list['name']))), 'confirmation');
             }
 
             $metadata['rsvp']         = intval($metadata['rsvp']);
             $metadata['after_action'] = $this->rc->config->get('calendar_itip_after_action', 0);
 
             $this->rc->output->command('plugin.itip_message_processed', $metadata);
             $error_msg = null;
         }
         else if ($error_msg) {
             $this->rc->output->command('display_message', $error_msg, 'error');
         }
 
         // send iTip reply
         if ($task['_method'] == 'REQUEST' && $organizer && !$noreply && !in_array(strtolower($organizer['email']), $emails) && !$error_msg) {
             $task['comment'] = $comment;
             $itip = $this->load_itip();
             $itip->set_sender_email($reply_sender);
 
             if ($itip->send_itip_message($this->to_libcal($task), 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status))
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $organizer['name'] ?: $organizer['email']))), 'confirmation');
             else
                 $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
         }
 
         $this->rc->output->send();
     }
 
 
     /****  Task invitation plugin hooks ****/
 
     /**
      * Handler for task/itip-delegate requests
      */
     function mail_itip_delegate()
     {
         // forward request to mail_import_itip() with the right status
         $_POST['_status'] = $_REQUEST['_status'] = 'delegated';
         $this->mail_import_itip();
     }
 
     /**
      * Find a task in user tasklists
      */
     protected function find_task($task, &$mode)
     {
         $this->load_driver();
 
         // We search for writeable folders in personal namespace by default
         $mode   = tasklist_driver::FILTER_WRITEABLE | tasklist_driver::FILTER_PERSONAL;
         $result = $this->driver->get_task($task, $mode);
 
         // ... now check shared folders if not found
         if (!$result) {
             $result = $this->driver->get_task($task, tasklist_driver::FILTER_WRITEABLE | tasklist_driver::FILTER_SHARED);
             if ($result) {
                 $mode |= tasklist_driver::FILTER_SHARED;
             }
         }
 
         return $result;
     }
 
     /**
      * Handler for task/itip-status requests
      */
     public function task_itip_status()
     {
         $data = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         // find local copy of the referenced task
         $existing  = $this->find_task($data, $mode);
         $is_shared = $mode & tasklist_driver::FILTER_SHARED;
         $itip      = $this->load_itip();
         $response  = $itip->get_itip_status($data, $existing);
 
         // get a list of writeable lists to save new tasks to
         if ((!$existing || $is_shared) && $response['action'] == 'rsvp' || $response['action'] == 'import') {
             $lists  = $this->driver->get_lists($mode);
             $select = new html_select(array('name' => 'tasklist', 'id' => 'itip-saveto', 'is_escaped' => true, 'class' => 'form-control'));
             $select->add('--', '');
 
             foreach ($lists as $list) {
                 if ($list['editable']) {
                     $select->add($list['name'], $list['id']);
                 }
             }
         }
 
         if ($select) {
             $default_list = $this->get_default_tasklist($lists);
             $response['select'] = html::span('folder-select', $this->gettext('saveintasklist') . '&nbsp;' .
                 $select->show($is_shared ? $existing['list'] : $default_list['id']));
         }
 
         $this->rc->output->command('plugin.update_itip_object_status', $response);
     }
 
     /**
      * Handler for task/itip-remove requests
      */
     public function task_itip_remove()
     {
         $success = false;
         $uid     = rcube_utils::get_input_value('uid', rcube_utils::INPUT_POST);
 
         // search for event if only UID is given
         if ($task = $this->driver->get_task($uid)) {
             $success = $this->driver->delete_task($task, true);
         }
 
         if ($success) {
             $this->rc->output->show_message('tasklist.successremoval', 'confirmation');
         }
         else {
             $this->rc->output->show_message('tasklist.errorsaving', 'error');
         }
     }
 
 
     /*******  Utility functions  *******/
 
     /**
      * Generate a unique identifier for an event
      */
     public function generate_uid()
     {
       return strtoupper(md5(time() . uniqid(rand())) . '-' . substr(md5($this->rc->user->get_username()), 0, 16));
     }
 
     /**
      * Map task properties for ical exprort using libcalendaring
      */
     public function to_libcal($task)
     {
         $object = $task;
         $object['_type'] = 'task';
         $object['categories'] = (array)$task['tags'];
 
         // convert to datetime objects
         if (!empty($task['date'])) {
             $object['due'] = rcube_utils::anytodatetime($task['date'].' '.$task['time'], $this->timezone);
             if (empty($task['time']))
                 $object['due']->_dateonly = true;
             unset($object['date']);
         }
 
         if (!empty($task['startdate'])) {
             $object['start'] = rcube_utils::anytodatetime($task['startdate'].' '.$task['starttime'], $this->timezone);
             if (empty($task['starttime']))
                 $object['start']->_dateonly = true;
             unset($object['startdate']);
         }
 
         $object['complete'] = $task['complete'] * 100;
         if ($task['complete'] == 1.0 && empty($task['complete'])) {
             $object['status'] = 'COMPLETED';
         }
 
         if ($task['flagged']) {
             $object['priority'] = 1;
         }
         else if (empty($task['priority'])) {
             $object['priority'] = 0;
         }
 
         return $object;
     }
 
     /**
      * Convert task properties from ical parser to the internal format
      */
     public function from_ical($vtodo)
     {
         $task = $vtodo;
 
         $task['tags'] = array_filter((array)$vtodo['categories']);
         $task['flagged'] = $vtodo['priority'] == 1;
         $task['complete'] = floatval($vtodo['complete'] / 100);
 
         // convert from DateTime to internal date format
         if (is_a($vtodo['due'], 'DateTime')) {
             $due = $this->lib->adjust_timezone($vtodo['due']);
             $task['date'] = $due->format('Y-m-d');
             if (!$vtodo['due']->_dateonly)
                 $task['time'] = $due->format('H:i');
         }
         // convert from DateTime to internal date format
         if (is_a($vtodo['start'], 'DateTime')) {
             $start = $this->lib->adjust_timezone($vtodo['start']);
             $task['startdate'] = $start->format('Y-m-d');
             if (!$vtodo['start']->_dateonly)
                 $task['starttime'] = $start->format('H:i');
         }
         if (is_a($vtodo['dtstamp'], 'DateTime')) {
             $task['changed'] = $vtodo['dtstamp'];
         }
 
         unset($task['categories'], $task['due'], $task['start'], $task['dtstamp']);
 
         return $task;
     }
 
     /**
      * Handler for user_delete plugin hook
      */
     public function user_delete($args)
     {
        $this->load_driver();
        return $this->driver->user_delete($args);
     }
 
 
     /**
      * Magic getter for public access to protected members
      */
     public function __get($name)
     {
         switch ($name) {
             case 'ical':
                 return $this->get_ical();
 
             case 'itip':
                 return $this->load_itip();
 
             case 'driver':
                 $this->load_driver();
                 return $this->driver;
         }
 
         return null;
     }
 }