diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index b341b0a4..ab25dfd8 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -1,3944 +1,3945 @@
 <?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_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']);
             $this->add_hook('refresh', [$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($sensitivity = null, $calendars = null)
     {
         if ($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 || $sensitivity) {
             foreach ($calendars as $cal) {
                 if ($sensitivity && $cal['subtype'] == $sensitivity) {
                     $calendar = $cal;
                     break;
                 }
                 if ($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_timeslot';
             $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);
 
             $p['blocks']['view']['options']['timeslots'] = [
                 'title' => html::label($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]);
 
             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', $this->defaults['calendar_itip_after_action']);
             if ($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 (!$this->driver->nocategories && !isset($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) {
                 $active = in_array($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'      => !empty(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 (!$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  = $calendars[$cal['id']];
 
                 // 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['id'] != $cal['id'] && $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');
             }
 
             $regid = 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);
             }
 
             $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);
             }
 
             $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();
                 $organizer = null;
 
                 foreach ($event['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                         $reply_sender = $attendee['email'];
                     }
                 }
 
                 if (!$noreply) {
                     $itip = $this->load_itip();
                     $itip->set_sender_email($reply_sender);
                     $event['thisandfuture'] = $event['_savemode'] == 'future';
 
                     if ($organizer && $itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $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 DateTime) {
                             $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)) {
                 $sent = $this->notify_attendees($event, $old, $action, $event['_comment']);
                 if ($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 $rangestart
             if ($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();
             $settings['identity'] = [
                 'name'   => $identity['name'],
                 'email'  => strtolower($identity['email']),
                 'emails' => ';' . strtolower(join(';', $identity['emails']))
             ];
         }
 
         // 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']);
         }
 
         foreach ((array) $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-event');
 
         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 && $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 && $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, $rsvp = null)
     {
         if ($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
         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] != '_' && $a[$key] != $b[$key]) {
                 $diff[] = $key;
             }
         }
 
         // only compare number of attachments
         if (count((array) $a['attachments']) != count((array) $b['attachments'])) {
             $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;
     }
 
     /****  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 || $is_shared)
             && !$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   = $this->get_default_calendar($data['sensitivity'], $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']['sensitivity']))) {
                             $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 = '')
     {
         $time = !empty($event['allday']) ? $this->gettext('all-day') :
             $this->rc->format_date($event['start'], $this->rc->config->get('time_format'))
             . ' - ' .
             $this->rc->format_date($event['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 = $this->rc->format_date($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;
 
         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, $mime_id, 'event')) {
             // forward iTip request to delegatee
             if ($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  = $calendars[$cal_id];
 
             // select default calendar except user explicitly selected 'none'
             if (!$calendar && !$dontsave) {
                 $calendar = $this->get_default_calendar($event['sensitivity'], $calendars);
             }
 
             $metadata = [
                 'uid'       => $event['uid'],
                 '_instance' => $event['_instance'],
                 'changed'   => is_object($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 ?: $event['_savemode'];
 
                     // only update attendee status
                     if ($event['_method'] == 'REPLY') {
                         // try to identify the attendee using the email sender address
                         $existing_attendee        = -1;
                         $existing_attendee_emails = [];
 
                         foreach ($existing['attendees'] as $i => $attendee) {
                             $existing_attendee_emails[] = $attendee['email'];
                             if ($this->itip->compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                                 $existing_attendee = $i;
                             }
                         }
 
                         $event_attendee   = null;
                         $update_attendees = [];
 
                         foreach ($event['attendees'] as $attendee) {
                             if ($this->itip->compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                                 $event_attendee       = $attendee;
                                 $update_attendees[]   = $attendee;
                                 $metadata['fallback'] = $attendee['status'];
                                 $metadata['attendee'] = $attendee['email'];
                                 $metadata['rsvp']     = !empty($attendee['rsvp']) || $attendee['role'] != 'NON-PARTICIPANT';
 
                                 if ($attendee['status'] != 'DELEGATED') {
                                     break;
                                 }
                             }
                             // also copy delegate attendee
                             else if (!empty($attendee['delegated-from'])
                                 && $this->itip->compare_email($attendee['delegated-from'], $event['_sender'], $event['_sender_utf'])
                             ) {
                                 $update_attendees[] = $attendee;
                                 if (!in_array_nocase($attendee['email'], $existing_attendee_emails)) {
                                     $existing['attendees'][] = $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;
                                 }
                             }
                         }
 
                         // Accept sender as a new participant (different email in From: and the iTip)
                         // Use ATTENDEE entry from the iTip with replaced email address
                         if (!$event_attendee) {
                             // remove the organizer
                             $itip_attendees = array_filter(
                                 $event['attendees'],
                                 function($item) { return $item['role'] != 'ORGANIZER'; }
                             );
 
                             // there must be only one attendee
                             if (is_array($itip_attendees) && count($itip_attendees) == 1) {
                                 $event_attendee          = $itip_attendees[key($itip_attendees)];
                                 $event_attendee['email'] = $event['_sender'];
                                 $update_attendees[]      = $event_attendee;
                                 $metadata['fallback']    = $event_attendee['status'];
                                 $metadata['attendee']    = $event_attendee['email'];
                                 $metadata['rsvp']        = !empty($event_attendee['rsvp']) || $event_attendee['role'] != 'NON-PARTICIPANT';
                             }
                         }
 
                         // found matching attendee entry in both existing and new events
                         if ($existing_attendee >= 0 && $event_attendee) {
                             $existing['attendees'][$existing_attendee] = $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'
                             || $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'] = $event['calendar'];
             $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' && $organizer && !$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] : $this->get_default_calendar($event['sensitivity']);
                 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;
     }
 
     /**
      * 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);
         }
 
         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/database/database_driver.php b/plugins/calendar/drivers/database/database_driver.php
index 699cb88a..5c771c2b 100644
--- a/plugins/calendar/drivers/database/database_driver.php
+++ b/plugins/calendar/drivers/database/database_driver.php
@@ -1,1530 +1,1529 @@
 <?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']),
             $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']),
             intval($event['recurrence_id']),
             strval($event['_instance']),
             intval($event['isexception']),
             $event['start']->format(self::DB_DATE_FORMAT),
             $event['end']->format(self::DB_DATE_FORMAT),
             intval($event['all_day']),
             $event['_recurrence'],
             strval($event['title']),
             strval($event['description']),
             strval($event['location']),
             join(',', (array)$event['categories']),
             strval($event['url']),
             intval($event['free_busy']),
             intval($event['priority']),
             intval($event['sensitivity']),
             strval($event['status']),
             $event['attendees'],
             $event['alarms'],
             $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) {
                 $event['sequence'] = max($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 ($old['recurrence']['EXDATE']) {
+                if (!empty($old['recurrence']['EXDATE'])) {
                     $event['recurrence']['EXDATE'] = $old['recurrence']['EXDATE'];
                 }
 
                 switch ($event['_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 = $old[$prop];
-            $b = $event[$prop];
+            $a = isset($old[$prop]) ? $old[$prop] : null;
+            $b = isset($event[$prop]) ? $event[$prop] : null;
 
-            if ($event['allday'] && ($prop == 'start' || $prop == 'end') && $a instanceof DateTime && $b instanceof DateTime) {
+            if (!empty($event['allday']) && ($prop == 'start' || $prop == 'end')
+                && $a instanceof DateTime && $b instanceof DateTime
+            ) {
                 $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 ($a['COUNT'] && $b['COUNT'] && $b['COUNT'] < $a['COUNT']) {
+                if (!empty($a['COUNT']) && !empty($b['COUNT']) && $b['COUNT'] < $a['COUNT']) {
                     unset($a['COUNT'], $b['COUNT']);
                 }
-                else if ($a['UNTIL'] && $b['UNTIL'] && $b['UNTIL'] < $a['UNTIL']) {
+                else if (!empty($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 = $event['recurrence'] ? libcalendaring::to_rrule($event['recurrence']) : '';
 
         $event['_recurrence'] = rtrim($rrule, ';');
         $event['free_busy']   = intval($this->free_busy_map[strtolower($event['free_busy'])]);
         $event['sensitivity'] = intval($this->sensitivity_map[strtolower($event['sensitivity'])]);
 
         if ($event['free_busy'] == 'tentative') {
             $event['status'] = 'TENTATIVE';
         }
 
         if (isset($event['allday'])) {
             $event['all_day'] = $event['allday'] ? 1 : 0;
         }
 
         // compute absolute time to notify the user
         $event['notifyat'] = $this->_get_notification($event);
 
-        if (is_array($event['valarms'])) {
+        if (!empty($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($event)
     {
-        if ($event['valarms'] && $event['start'] > new DateTime()) {
+        if (!empty($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 $col) {
-            if (is_object($event[$col]) && is_a($event[$col], 'DateTime')) {
+            if (!empty($event[$col]) && is_a($event[$col], 'DateTime')) {
                 $sql_args[$col] = $event[$col]->format(self::DB_DATE_FORMAT);
             }
-            else if (is_array($event[$col])) {
-                $sql_args[$col] = join(',', $event[$col]);
-            }
             else if (array_key_exists($col, $event)) {
-                $sql_args[$col] = $event[$col];
+                $sql_args[$col] = is_array($event[$col]) ? join(',', $event[$col]) : $event[$col];
             }
         }
 
-        if ($event['_recurrence']) {
+        if (!empty($event['_recurrence'])) {
             $sql_args['recurrence'] = $event['_recurrence'];
         }
 
-        if ($event['_instance']) {
+        if (!empty($event['_instance'])) {
             $sql_args['instance'] = $event['_instance'];
         }
 
-        if ($event['_fromcalendar'] && $event['_fromcalendar'] != $event['calendar']) {
+        if (!empty($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'])) {
             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);
             $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 ($exdata[$datestr]) {
+                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' => $event['alarms'],
+                        'alarms' => !empty($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 (++$count > 999 || (!$recurrence->recurEnd && !$recurrence->recurCount && $next_start->format('Y') > date('Y') + 20)) {
+                if (++$count > 999 || (empty($recurrence->recurEnd) && empty($recurrence->recurCount) && $next_start->format('Y') > date('Y') + 20)) {
                     break;
                 }
             }
 
             // remove all exceptions after recurrence end
             if ($next_end && !empty($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) ? ($event['id'] ?: $event['uid']) : $event;
-        $cal = is_array($event) ? $event['calendar'] : null;
+        $cal = is_array($event) && !empty($event['calendar']) ? $event['calendar'] : null;
         $col = is_array($event) && is_numeric($id) ? 'event_id' : 'uid';
 
-        if ($this->cache[$id]) {
+        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) && !$event['id'] && !empty($event['_instance'])) {
             $where_add = " AND e.instance = " . $this->rc->db->quote($event['_instance']);
         }
 
         if ($scope & self::FILTER_ACTIVE) {
             $calendars = $this->calendars;
             foreach ($calendars as $idx => $cal) {
                 if (!$cal['active']) {
                     unset($calendars[$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 ($event['_attachments'] > 0) {
+        if (!empty($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,
-                $event['recurrence_id'] ? $event['recurrence_id'] : $event['id']
+                !empty($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 DateTime) {
                 $valarms[$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/libcalendaring/lib/libcalendaring_recurrence.php b/plugins/libcalendaring/lib/libcalendaring_recurrence.php
index f83d024c..abefe4e5 100644
--- a/plugins/libcalendaring/lib/libcalendaring_recurrence.php
+++ b/plugins/libcalendaring/lib/libcalendaring_recurrence.php
@@ -1,234 +1,234 @@
 <?php
 
 /**
  * Recurrence computation class for shared use
  *
  * Uitility class to compute reccurrence dates from the given rules
  *
  * @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 libcalendaring_recurrence
 {
     protected $lib;
     protected $start;
     protected $next;
     protected $engine;
     protected $recurrence;
     protected $dateonly = false;
     protected $hour = 0;
 
     /**
      * Default constructor
      *
      * @param object calendar The calendar plugin instance
      */
     function __construct($lib)
     {
       // 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;
     }
 
     /**
      * Initialize recurrence engine
      *
      * @param array  The recurrence properties
      * @param object DateTime The recurrence start date
      */
     public function init($recurrence, $start = null)
     {
         $this->recurrence = $recurrence;
 
         $this->engine = new Horde_Date_Recurrence($start);
         $this->engine->fromRRule20(libcalendaring::to_rrule($recurrence));
 
         $this->set_start($start);
 
-        if (is_array($recurrence['EXDATE'])) {
-            foreach ($recurrence['EXDATE'] as $exdate) {
+        if (!empty($recurrence['EXDATE'])) {
+            foreach ((array) $recurrence['EXDATE'] as $exdate) {
                 if (is_a($exdate, 'DateTime')) {
                     $this->engine->addException($exdate->format('Y'), $exdate->format('n'), $exdate->format('j'));
                 }
             }
         }
-        if (is_array($recurrence['RDATE'])) {
-            foreach ($recurrence['RDATE'] as $rdate) {
+        if (!empty($recurrence['RDATE'])) {
+            foreach ((array) $recurrence['RDATE'] as $rdate) {
                 if (is_a($rdate, 'DateTime')) {
                     $this->engine->addRDate($rdate->format('Y'), $rdate->format('n'), $rdate->format('j'));
                 }
             }
         }
     }
 
     /**
      * Setter for (new) recurrence start date
      *
      * @param object DateTime The recurrence start date
      */
     public function set_start($start)
     {
         $this->start = $start;
         $this->dateonly = $start->_dateonly;
         $this->next = new Horde_Date($start, $this->lib->timezone->getName());
         $this->hour = $this->next->hour;
         $this->engine->setRecurStart($this->next);
     }
 
     /**
      * Get date/time of the next occurence of this event
      *
      * @return mixed DateTime object or False if recurrence ended
      */
     public function next()
     {
         $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;
             }
             // fix time for all-day events
             if ($this->dateonly) {
                 $next->hour = $this->hour;
                 $next->min = 0;
             }
 
             $time = $next->toDateTime();
             $this->next = $next;
         }
 
         return $time;
     }
 
     /**
      * Get the end date of the occurence of this recurrence cycle
      *
      * @return DateTime|bool End datetime of the last occurence or False if recurrence exceeds limit
      */
     public function end()
     {
         // recurrence end date is given
         if ($this->recurrence['UNTIL'] instanceof DateTime) {
             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 DateTime) {
               return $last;
             }
         }
 
         // 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++;
             }
         }
 
         return $last;
     }
 
     /**
      * Find date/time of the first occurrence (excluding start date)
      */
     public function first_occurrence()
     {
         $start      = clone $this->start;
         $orig_start = clone $this->start;
         $r          = $this->recurrence;
         $interval   = intval($r['INTERVAL'] ?: 1);
 
         switch ($this->recurrence['FREQ']) {
         case 'WEEKLY':
             if (empty($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;
 
         default:
             return $start;
         }
 
         $r = $this->recurrence;
         $r['INTERVAL'] = $interval;
         if ($r['COUNT']) {
             // Increase count so we do not stop the loop to early
             $r['COUNT'] += 100;
         }
 
         // Create recurrence that starts in the past
         $recurrence = new self($this->lib);
         $recurrence->init($r, $start);
 
         // find the first occurrence
         $found = false;
         while ($next = $recurrence->next()) {
             $start = $next;
             if ($next >= $orig_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);
 
             return null;
         }
 
         if ($start Instanceof Horde_Date) {
             $start = $start->toDateTime();
         }
 
         $start->_dateonly = $this->dateonly;
 
         return $start;
     }
 }
diff --git a/plugins/libcalendaring/libcalendaring.php b/plugins/libcalendaring/libcalendaring.php
index 92f930ac..c6c345cb 100644
--- a/plugins/libcalendaring/libcalendaring.php
+++ b/plugins/libcalendaring/libcalendaring.php
@@ -1,1555 +1,1555 @@
 <?php
 
 /**
  * Library providing common functions for calendaring plugins
  *
  * Provides utility functions for calendar-related modules such as
  * - alarms display and dismissal
  * - attachment handling
  * - recurrence computation and UI elements
  * - ical parsing and exporting
  * - itip scheduling protocol
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * 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 libcalendaring extends rcube_plugin
 {
     public $rc;
     public $timezone;
     public $gmt_offset;
     public $dst_active;
     public $timezone_offset;
     public $ical_parts = array();
     public $ical_message;
 
     public $defaults = array(
         'calendar_date_format'  => "Y-m-d",
         'calendar_date_short'   => "M-j",
         'calendar_date_long'    => "F j Y",
         'calendar_date_agenda'  => "l M-d",
         'calendar_time_format'  => "H:m",
         'calendar_first_day'    => 1,
         'calendar_first_hour'   => 6,
         'calendar_date_format_sets' => array(
             'Y-m-d' => array('d M Y',   'm-d',  'l m-d'),
             'Y/m/d' => array('d M Y',   'm/d',  'l m/d'),
             'Y.m.d' => array('d M Y',   'm.d',  'l m.d'),
             'd-m-Y' => array('d M Y',   'd-m',  'l d-m'),
             'd/m/Y' => array('d M Y',   'd/m',  'l d/m'),
             'd.m.Y' => array('d M Y',  'd.m',  'l d.m'),
             'j.n.Y' => array('d M Y',  'd.m',  'l d.m'),
             'm/d/Y' => array('M d Y',   'm/d',  'l m/d'),
         ),
     );
 
     private static $instance;
 
     private $mail_ical_parser;
 
     /**
      * Singleton getter to allow direct access from other plugins
      */
     public static function get_instance()
     {
         if (!self::$instance) {
             self::$instance = new libcalendaring(rcube::get_instance()->plugins);
             self::$instance->init_instance();
         }
 
         return self::$instance;
     }
 
     /**
      * Initializes class properties
      */
     public function init_instance()
     {
         $this->rc = rcube::get_instance();
 
         // set user's timezone
         try {
             $this->timezone = new DateTimeZone($this->rc->config->get('timezone', 'GMT'));
         }
         catch (Exception $e) {
             $this->timezone = new DateTimeZone('GMT');
         }
 
         $now = new DateTime('now', $this->timezone);
 
         $this->gmt_offset      = $now->getOffset();
         $this->dst_active      = $now->format('I');
         $this->timezone_offset = $this->gmt_offset / 3600 - $this->dst_active;
 
         $this->add_texts('localization/', false);
     }
 
     /**
      * Required plugin startup method
      */
     public function init()
     {
         self::$instance = $this;
 
         $this->rc = rcube::get_instance();
         $this->init_instance();
 
         // include client scripts and styles
         if ($this->rc->output) {
             // add hook to display alarms
             $this->add_hook('refresh', array($this, 'refresh'));
             $this->register_action('plugin.alarms', array($this, 'alarms_action'));
             $this->register_action('plugin.expand_attendee_group', array($this, 'expand_attendee_group'));
         }
 
         // proceed initialization in startup hook
         $this->add_hook('startup', array($this, 'startup'));
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         if ($this->rc->output && $this->rc->output->type == 'html') {
             $this->rc->output->set_env('libcal_settings', $this->load_settings());
             $this->include_script('libcalendaring.js');
             $this->include_stylesheet($this->local_skin_path() . '/libcal.css');
 
             $this->add_label(
                 'itipaccepted', 'itiptentative', 'itipdeclined',
                 'itipdelegated', 'expandattendeegroup', 'expandattendeegroupnodata',
                 'statusorganizer', 'statusaccepted', 'statusdeclined',
                 'statusdelegated', 'statusunknown', 'statusneeds-action',
                 'statustentative', 'statuscompleted', 'statusin-process',
                 'delegatedto', 'delegatedfrom', 'showmore'
             );
         }
 
         if ($args['task'] == 'mail') {
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 $this->add_hook('message_load', array($this, 'mail_message_load'));
             }
         }
     }
 
     /**
      * Load iCalendar functions
      */
     public static function get_ical()
     {
         $self = self::get_instance();
         require_once __DIR__ . '/libvcalendar.php';
         return new libvcalendar();
     }
 
     /**
      * Load iTip functions
      */
     public static function get_itip($domain = 'libcalendaring')
     {
         $self = self::get_instance();
         require_once __DIR__ . '/lib/libcalendaring_itip.php';
         return new libcalendaring_itip($self, $domain);
     }
 
     /**
      * Load recurrence computation engine
      */
     public static function get_recurrence()
     {
         $self = self::get_instance();
         require_once __DIR__ . '/lib/libcalendaring_recurrence.php';
         return new libcalendaring_recurrence($self);
     }
 
     /**
      * Shift dates into user's current timezone
      *
      * @param mixed Any kind of a date representation (DateTime object, string or unix timestamp)
      * @return object DateTime object in user's timezone
      */
     public function adjust_timezone($dt, $dateonly = false)
     {
         if (is_numeric($dt)) {
             $dt = new DateTime('@'.$dt);
         }
         else if (is_string($dt)) {
             $dt = rcube_utils::anytodatetime($dt);
         }
 
-        if ($dt instanceof DateTime && !($dt->_dateonly || $dateonly)) {
+        if ($dt instanceof DateTime && empty($dt->_dateonly) && !$dateonly) {
             $dt->setTimezone($this->timezone);
         }
 
         return $dt;
     }
 
     /**
      *
      */
     public function load_settings()
     {
         $this->date_format_defaults();
 
         $settings = array();
         $keys     = array('date_format', 'time_format', 'date_short', 'date_long', 'date_agenda');
 
         foreach ($keys as $key) {
             $settings[$key] = (string)$this->rc->config->get('calendar_' . $key, $this->defaults['calendar_' . $key]);
             $settings[$key] = self::from_php_date_format($settings[$key]);
         }
 
         $settings['dates_long']  = $settings['date_long'];
         $settings['first_day']   = (int)$this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
         $settings['timezone']    = $this->timezone_offset;
         $settings['dst']         = $this->dst_active;
 
         // localization
         $settings['days'] = array(
             $this->rc->gettext('sunday'),   $this->rc->gettext('monday'),
             $this->rc->gettext('tuesday'),  $this->rc->gettext('wednesday'),
             $this->rc->gettext('thursday'), $this->rc->gettext('friday'),
             $this->rc->gettext('saturday')
         );
         $settings['days_short'] = array(
             $this->rc->gettext('sun'), $this->rc->gettext('mon'),
             $this->rc->gettext('tue'), $this->rc->gettext('wed'),
             $this->rc->gettext('thu'), $this->rc->gettext('fri'),
             $this->rc->gettext('sat')
         );
         $settings['months'] = array(
             $this->rc->gettext('longjan'), $this->rc->gettext('longfeb'),
             $this->rc->gettext('longmar'), $this->rc->gettext('longapr'),
             $this->rc->gettext('longmay'), $this->rc->gettext('longjun'),
             $this->rc->gettext('longjul'), $this->rc->gettext('longaug'),
             $this->rc->gettext('longsep'), $this->rc->gettext('longoct'),
             $this->rc->gettext('longnov'), $this->rc->gettext('longdec')
         );
         $settings['months_short'] = array(
             $this->rc->gettext('jan'), $this->rc->gettext('feb'),
             $this->rc->gettext('mar'), $this->rc->gettext('apr'),
             $this->rc->gettext('may'), $this->rc->gettext('jun'),
             $this->rc->gettext('jul'), $this->rc->gettext('aug'),
             $this->rc->gettext('sep'), $this->rc->gettext('oct'),
             $this->rc->gettext('nov'), $this->rc->gettext('dec')
         );
         $settings['today'] = $this->rc->gettext('today');
 
         return $settings;
     }
 
 
     /**
      * Helper function to set date/time format according to config and user preferences
      */
     private function date_format_defaults()
     {
         static $defaults = array();
 
         // nothing to be done
         if (isset($defaults['date_format']))
           return;
 
         $defaults['date_format'] = $this->rc->config->get('calendar_date_format', $this->rc->config->get('date_format'));
         $defaults['time_format'] = $this->rc->config->get('calendar_time_format', $this->rc->config->get('time_format'));
 
         // override defaults
         if ($defaults['date_format'])
             $this->defaults['calendar_date_format'] = $defaults['date_format'];
         if ($defaults['time_format'])
             $this->defaults['calendar_time_format'] = $defaults['time_format'];
 
         // derive format variants from basic date format
         $format_sets = $this->rc->config->get('calendar_date_format_sets', $this->defaults['calendar_date_format_sets']);
         if ($format_set = $format_sets[$this->defaults['calendar_date_format']]) {
             $this->defaults['calendar_date_long'] = $format_set[0];
             $this->defaults['calendar_date_short'] = $format_set[1];
             $this->defaults['calendar_date_agenda'] = $format_set[2];
         }
     }
 
     /**
      * Compose a date string for the given event
      */
     public function event_date_text($event, $tzinfo = false)
     {
         $fromto = '--';
 
         // handle task objects
         if ($event['_type'] == 'task' && is_object($event['due'])) {
-            $date_format = $event['due']->_dateonly ? self::to_php_date_format($this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format'])) : null;
+            $date_format = !empty($event['due']->_dateonly) ? self::to_php_date_format($this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format'])) : null;
             $fromto = $this->rc->format_date($event['due'], $date_format, false);
 
             // add timezone information
             if ($fromto && $tzinfo && ($tzname = $this->timezone->getName())) {
                 $fromto .= ' (' . strtr($tzname, '_', ' ') . ')';
             }
 
             return $fromto;
         }
 
         // abort if no valid event dates are given
         if (!is_object($event['start']) || !is_a($event['start'], 'DateTime') || !is_object($event['end']) || !is_a($event['end'], 'DateTime')) {
             return $fromto;
         }
 
         $duration = $event['start']->diff($event['end'])->format('s');
 
         $this->date_format_defaults();
         $date_format = self::to_php_date_format($this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format']));
         $time_format = self::to_php_date_format($this->rc->config->get('calendar_time_format', $this->defaults['calendar_time_format']));
 
         if ($event['allday']) {
             $fromto = $this->rc->format_date($event['start'], $date_format, false);
             if (($todate = $this->rc->format_date($event['end'], $date_format, false)) != $fromto)
                 $fromto .= ' - ' . $todate;
         }
         else if ($duration < 86400 && $event['start']->format('d') == $event['end']->format('d')) {
             $fromto = $this->rc->format_date($event['start'], $date_format) . ' ' . $this->rc->format_date($event['start'], $time_format) .
                 ' - ' . $this->rc->format_date($event['end'], $time_format);
         }
         else {
             $fromto = $this->rc->format_date($event['start'], $date_format) . ' ' . $this->rc->format_date($event['start'], $time_format) .
                 ' - ' . $this->rc->format_date($event['end'], $date_format) . ' ' . $this->rc->format_date($event['end'], $time_format);
         }
 
         // add timezone information
         if ($tzinfo && ($tzname = $this->timezone->getName())) {
             $fromto .= ' (' . strtr($tzname, '_', ' ') . ')';
         }
 
         return $fromto;
     }
 
 
     /**
      * Render HTML form for alarm configuration
      */
     public function alarm_select($attrib, $alarm_types, $absolute_time = true)
     {
         unset($attrib['name']);
 
         $input_value    = new html_inputfield(array('name' => 'alarmvalue[]', 'class' => 'edit-alarm-value form-control', 'size' => 3));
         $input_date     = new html_inputfield(array('name' => 'alarmdate[]', 'class' => 'edit-alarm-date form-control', 'size' => 10));
         $input_time     = new html_inputfield(array('name' => 'alarmtime[]', 'class' => 'edit-alarm-time form-control', 'size' => 6));
         $select_type    = new html_select(array('name' => 'alarmtype[]', 'class' => 'edit-alarm-type form-control', 'id' => $attrib['id']));
         $select_offset  = new html_select(array('name' => 'alarmoffset[]', 'class' => 'edit-alarm-offset form-control'));
         $select_related = new html_select(array('name' => 'alarmrelated[]', 'class' => 'edit-alarm-related form-control'));
         $object_type    = !empty($attrib['_type']) ? $attrib['_type'] : 'event';
 
         $select_type->add($this->gettext('none'), '');
         foreach ($alarm_types as $type) {
             $select_type->add($this->gettext(strtolower("alarm{$type}option")), $type);
         }
 
         foreach (array('-M','-H','-D','+M','+H','+D') as $trigger) {
             $select_offset->add($this->gettext('trigger' . $trigger), $trigger);
         }
 
         $select_offset->add($this->gettext('trigger0'), '0');
         if ($absolute_time) {
             $select_offset->add($this->gettext('trigger@'), '@');
         }
 
         $select_related->add($this->gettext('relatedstart'), 'start');
         $select_related->add($this->gettext('relatedend' . $object_type), 'end');
 
         // pre-set with default values from user settings
         $preset = self::parse_alarm_value($this->rc->config->get('calendar_default_alarm_offset', '-15M'));
         $hidden = array('style' => 'display:none');
 
         return html::span('edit-alarm-set',
             $select_type->show($this->rc->config->get('calendar_default_alarm_type', '')) . ' ' .
             html::span(array('class' => 'edit-alarm-values input-group', 'style' => 'display:none'),
                 $input_value->show($preset[0]) . ' ' .
                 $select_offset->show($preset[1]) . ' ' .
                 $select_related->show() . ' ' .
                 $input_date->show('', $hidden) . ' ' .
                 $input_time->show('', $hidden)
             )
         );
     }
 
     /**
      * Get a list of email addresses of the given user (from login and identities)
      *
      * @param string User Email (default to current user)
      *
      * @return array Email addresses related to the user
      */
     public function get_user_emails($user = null)
     {
         static $_emails = array();
 
         if (empty($user)) {
             $user = $this->rc->user->get_username();
         }
 
         // return cached result
-        if (is_array($_emails[$user])) {
+        if (isset($_emails[$user])) {
             return $_emails[$user];
         }
 
         $emails = array($user);
         $plugin = $this->rc->plugins->exec_hook('calendar_user_emails', array('emails' => $emails));
         $emails = array_map('strtolower', $plugin['emails']);
 
         // add all emails from the current user's identities
         if (!$plugin['abort'] && ($user == $this->rc->user->get_username())) {
             foreach ($this->rc->user->list_emails() as $identity) {
                 $emails[] = strtolower($identity['email']);
             }
         }
 
         $_emails[$user] = array_unique($emails);
         return $_emails[$user];
     }
 
     /**
      * Set the given participant status to the attendee matching the current user's identities
      * Unsets 'rsvp' flag too.
      *
      * @param array  &$event    Event data
      * @param string $status    The PARTSTAT value to set
      * @param bool   $recursive Recurive call
      *
      * @return mixed Email address of the updated attendee or False if none matching found
      */
     public function set_partstat(&$event, $status, $recursive = true)
     {
         $success = false;
         $emails = $this->get_user_emails();
         foreach ((array)$event['attendees'] as $i => $attendee) {
             if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                 $event['attendees'][$i]['status'] = strtoupper($status);
                 unset($event['attendees'][$i]['rsvp']);
                 $success = $attendee['email'];
             }
         }
 
         // apply partstat update to each existing exception
         if ($event['recurrence'] && is_array($event['recurrence']['EXCEPTIONS'])) {
             foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
                 $this->set_partstat($event['recurrence']['EXCEPTIONS'][$i], $status, false);
             }
 
             // set link to top-level exceptions
             $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
         }
 
         return $success;
     }
 
 
     /*********  Alarms handling  *********/
 
     /**
      * Helper function to convert alarm trigger strings
      * into two-field values (e.g. "-45M" => 45, "-M")
      */
     public static function parse_alarm_value($val)
     {
         if ($val[0] == '@') {
             return array(new DateTime($val));
         }
         else if (preg_match('/([+-]?)P?(T?\d+[HMSDW])+/', $val, $m) && preg_match_all('/T?(\d+)([HMSDW])/', $val, $m2, PREG_SET_ORDER)) {
             if ($m[1] == '')
                 $m[1] = '+';
             foreach ($m2 as $seg) {
                 $prefix = $seg[2] == 'D' || $seg[2] == 'W' ? 'P' : 'PT';
                 if ($seg[1] > 0) {  // ignore zero values
                     // convert seconds to minutes
                     if ($seg[2] == 'S') {
                         $seg[2] = 'M';
                         $seg[1] = max(1, round($seg[1]/60));
                     }
 
                     return array($seg[1], $m[1].$seg[2], $m[1].$seg[1].$seg[2], $m[1].$prefix.$seg[1].$seg[2]);
                 }
             }
 
             // return zero value nevertheless
             return array($seg[1], $m[1].$seg[2], $m[1].$seg[1].$seg[2], $m[1].$prefix.$seg[1].$seg[2]);
         }
 
         return false;
     }
 
     /**
      * Convert the alarms list items to be processed on the client
      */
     public static function to_client_alarms($valarms)
     {
         return array_map(function($alarm){
             if ($alarm['trigger'] instanceof DateTime) {
                 $alarm['trigger'] = '@' . $alarm['trigger']->format('U');
             }
             else if ($trigger = libcalendaring::parse_alarm_value($alarm['trigger'])) {
                 $alarm['trigger'] = $trigger[2];
             }
             return $alarm;
         }, (array)$valarms);
     }
 
     /**
      * Process the alarms values submitted by the client
      */
     public static function from_client_alarms($valarms)
     {
         return array_map(function($alarm){
             if ($alarm['trigger'][0] == '@') {
                 try {
                     $alarm['trigger'] = new DateTime($alarm['trigger']);
                     $alarm['trigger']->setTimezone(new DateTimeZone('UTC'));
                 }
                 catch (Exception $e) { /* handle this ? */ }
             }
             else if ($trigger = libcalendaring::parse_alarm_value($alarm['trigger'])) {
                 $alarm['trigger'] = $trigger[3];
             }
             return $alarm;
         }, (array)$valarms);
     }
 
     /**
      * Render localized text for alarm settings
      */
     public static function alarms_text($alarms)
     {
         if (is_array($alarms) && is_array($alarms[0])) {
             $texts = array();
             foreach ($alarms as $alarm) {
                 if ($text = self::alarm_text($alarm))
                     $texts[] = $text;
             }
 
             return join(', ', $texts);
         }
         else {
             return self::alarm_text($alarms);
         }
     }
 
     /**
      * Render localized text for a single alarm property
      */
     public static function alarm_text($alarm)
     {
         if (is_string($alarm)) {
             list($trigger, $action) = explode(':', $alarm);
         }
         else {
             $trigger = $alarm['trigger'];
             $action  = $alarm['action'];
             $related = $alarm['related'];
         }
 
         $text  = '';
         $rcube = rcube::get_instance();
 
         switch ($action) {
         case 'EMAIL':
             $text = $rcube->gettext('libcalendaring.alarmemail');
             break;
         case 'DISPLAY':
             $text = $rcube->gettext('libcalendaring.alarmdisplay');
             break;
         case 'AUDIO':
             $text = $rcube->gettext('libcalendaring.alarmaudio');
             break;
         }
 
         if ($trigger instanceof DateTime) {
             $text .= ' ' . $rcube->gettext(array(
                 'name' => 'libcalendaring.alarmat',
                 'vars' => array('datetime' => $rcube->format_date($trigger))
             ));
         }
         else if (preg_match('/@(\d+)/', $trigger, $m)) {
             $text .= ' ' . $rcube->gettext(array(
                 'name' => 'libcalendaring.alarmat',
                 'vars' => array('datetime' => $rcube->format_date($m[1]))
             ));
         }
         else if ($val = self::parse_alarm_value($trigger)) {
             $r = strtoupper($related ?: 'start') == 'END' ? 'end' : '';
             // TODO: for all-day events say 'on date of event at XX' ?
             if ($val[0] == 0) {
                 $text .= ' ' . $rcube->gettext('libcalendaring.triggerattime' . $r);
             }
             else {
                 $label = 'libcalendaring.trigger' . $r . $val[1];
                 $text .= ' ' . intval($val[0]) . ' ' . $rcube->gettext($label);
             }
         }
         else {
             return false;
         }
 
         return $text;
     }
 
     /**
      * Get the next alarm (time & action) for the given event
      *
      * @param array Record data
      * @return array Hash array with alarm time/type or null if no alarms are configured
      */
     public static function get_next_alarm($rec, $type = 'event')
     {
         if (
             (empty($rec['valarms']) && empty($rec['alarms']))
             || !empty($rec['cancelled'])
             || (!empty($rec['status']) && $rec['status'] == 'CANCELLED')
         ) {
             return null;
         }
 
         if ($type == 'task') {
             $timezone = self::get_instance()->timezone;
             if (!empty($rec['startdate'])) {
                 $time = !empty($rec['starttime']) ? $rec['starttime'] : '12:00';
                 $rec['start'] = new DateTime($rec['startdate'] . ' ' . $time, $timezone);
             }
             if (!empty($rec['date'])) {
                 $time = !empty($rec['time']) ? $rec['time'] : '12:00';
                 $rec[!empty($rec['start']) ? 'end' : 'start'] = new DateTime($rec['date'] . ' ' . $time, $timezone);
             }
         }
 
         if (empty($rec['end'])) {
             $rec['end'] = $rec['start'];
         }
 
         // support legacy format
         if (empty($rec['valarms'])) {
             list($trigger, $action) = explode(':', $rec['alarms'], 2);
             if ($alarm = self::parse_alarm_value($trigger)) {
                 $rec['valarms'] = array(array('action' => $action, 'trigger' => $alarm[3] ?: $alarm[0]));
             }
         }
 
         // alarm ID eq. record ID by default to keep backwards compatibility
         $alarm_id   = isset($rec['id']) ? $rec['id'] : null;
         $alarm_prop = null;
         $expires    = new DateTime('now - 12 hours');
         $notify_at  = null;
 
         // handle multiple alarms
         foreach ($rec['valarms'] as $alarm) {
             $notify_time = null;
 
             if ($alarm['trigger'] instanceof DateTime) {
                 $notify_time = $alarm['trigger'];
             }
             else if (is_string($alarm['trigger'])) {
                 $refdate = !empty($alarm['related']) && $alarm['related'] == 'END' ? $rec['end'] : $rec['start'];
 
                 // abort if no reference date is available to compute notification time
                 if (!is_a($refdate, 'DateTime')) {
                     continue;
                 }
 
                 // TODO: for all-day events, take start @ 00:00 as reference date ?
 
                 try {
                     $interval = new DateInterval(trim($alarm['trigger'], '+-'));
                     $interval->invert = $alarm['trigger'][0] == '-';
                     $notify_time = clone $refdate;
                     $notify_time->add($interval);
                 }
                 catch (Exception $e) {
                     rcube::raise_error($e, true);
                     continue;
                 }
             }
 
             if ($notify_time && (!$notify_at || ($notify_time > $notify_at && $notify_time > $expires))) {
                 $notify_at  = $notify_time;
                 $action     = isset($alarm['action']) ? $alarm['action'] : null;
                 $alarm_prop = $alarm;
 
                 // generate a unique alarm ID if multiple alarms are set
                 if (count($rec['valarms']) > 1) {
                     $rec_id = substr(md5(isset($rec['id']) ? $rec['id'] : 'none'), 0, 16);
                     $alarm_id = $rec_id . '-' . $notify_at->format('Ymd\THis');
                 }
             }
         }
 
         return !$notify_at ? null : array(
             'time'   => $notify_at->format('U'),
             'action' => !empty($action) ? strtoupper($action) : 'DISPLAY',
             'id'     => $alarm_id,
             'prop'   => $alarm_prop,
         );
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for pending notifications and pass them to the client
      */
     public function refresh($attr)
     {
         // collect pending alarms from all providers (e.g. calendar, tasks)
         $plugin = $this->rc->plugins->exec_hook('pending_alarms', array(
             'time' => time(),
             'alarms' => array(),
         ));
 
         if (!$plugin['abort'] && !empty($plugin['alarms'])) {
             // make sure texts and env vars are available on client
             $this->add_texts('localization/', true);
             $this->rc->output->add_label('close');
             $this->rc->output->set_env('snooze_select', $this->snooze_select());
             $this->rc->output->command('plugin.display_alarms', $this->_alarms_output($plugin['alarms']));
         }
     }
 
     /**
      * Handler for alarm dismiss/snooze requests
      */
     public function alarms_action()
     {
 //        $action = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $data  = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         $data['ids'] = explode(',', $data['id']);
         $plugin = $this->rc->plugins->exec_hook('dismiss_alarms', $data);
 
         if (!empty($plugin['success'])) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $this->rc->output->show_message('calendar.errorsaving', 'error');
         }
     }
 
     /**
      * Generate reduced and streamlined output for pending alarms
      */
     private function _alarms_output($alarms)
     {
         $out = array();
         foreach ($alarms as $alarm) {
             $out[] = array(
                 'id'       => $alarm['id'],
                 'start'    => !empty($alarm['start']) ? $this->adjust_timezone($alarm['start'])->format('c') : '',
                 'end'      => !empty($alarm['end'])? $this->adjust_timezone($alarm['end'])->format('c') : '',
                 'allDay'   => !empty($alarm['allday']),
                 'action'   => $alarm['action'],
                 'title'    => $alarm['title'],
                 'location' => $alarm['location'],
                 'calendar' => $alarm['calendar'],
             );
         }
 
         return $out;
     }
 
     /**
      * Render a dropdown menu to choose snooze time
      */
     private function snooze_select($attrib = array())
     {
         $steps = array(
              5 => 'repeatinmin',
             10 => 'repeatinmin',
             15 => 'repeatinmin',
             20 => 'repeatinmin',
             30 => 'repeatinmin',
             60 => 'repeatinhr',
             120 => 'repeatinhrs',
             1440 => 'repeattomorrow',
             10080 => 'repeatinweek',
         );
 
         $items = array();
         foreach ($steps as $n => $label) {
             $items[] = html::tag('li', null, html::a(array('href' => "#" . ($n * 60), 'class' => 'active'),
                 $this->gettext(array('name' => $label, 'vars' => array('min' => $n % 60, 'hrs' => intval($n / 60))))));
         }
 
         return html::tag('ul', $attrib + array('class' => 'toolbarmenu menu'), join("\n", $items), html::$common_attrib);
     }
 
 
     /*********  Recurrence rules handling ********/
 
     /**
      * Render localized text describing the recurrence rule of an event
      */
     public function recurrence_text($rrule)
     {
         $limit     = 10;
         $exdates   = array();
         $format    = $this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format']);
         $format    = self::to_php_date_format($format);
         $format_fn = function($dt) use ($format) {
             return rcmail::get_instance()->format_date($dt, $format);
         };
 
         if (is_array($rrule['EXDATE']) && !empty($rrule['EXDATE'])) {
             $exdates = array_map($format_fn, $rrule['EXDATE']);
         }
 
         if (empty($rrule['FREQ']) && !empty($rrule['RDATE'])) {
             $rdates = array_map($format_fn, $rrule['RDATE']);
+            $more   = false;
 
             if (!empty($exdates)) {
                 $rdates = array_diff($rdates, $exdates);
             }
 
             if (count($rdates) > $limit) {
                 $rdates = array_slice($rdates, 0, $limit);
                 $more   = true;
             }
 
-            return $this->gettext('ondate') . ' ' . join(', ', $rdates)
-                . ($more ? '...' : '');
+            return $this->gettext('ondate') . ' ' . join(', ', $rdates) . ($more ? '...' : '');
         }
 
         $output  = sprintf('%s %d ', $this->gettext('every'), $rrule['INTERVAL'] ?: 1);
 
         switch ($rrule['FREQ']) {
         case 'DAILY':
             $output .= $this->gettext('days');
             break;
         case 'WEEKLY':
             $output .= $this->gettext('weeks');
             break;
         case 'MONTHLY':
             $output .= $this->gettext('months');
             break;
         case 'YEARLY':
             $output .= $this->gettext('years');
             break;
         }
 
-        if ($rrule['COUNT']) {
+        if (!empty($rrule['COUNT'])) {
             $until = $this->gettext(array('name' => 'forntimes', 'vars' => array('nr' => $rrule['COUNT'])));
         }
-        else if ($rrule['UNTIL']) {
+        else if (!empty($rrule['UNTIL'])) {
             $until = $this->gettext('recurrencend') . ' ' . $this->rc->format_date($rrule['UNTIL'], $format);
         }
         else {
             $until = $this->gettext('forever');
         }
 
         $output .= ', ' . $until;
 
         if (!empty($exdates)) {
+            $more = false;
             if (count($exdates) > $limit) {
                 $exdates = array_slice($exdates, 0, $limit);
                 $more    = true;
             }
 
-            $output  .= '; ' . $this->gettext('except') . ' ' . join(', ', $exdates)
-                . ($more ? '...' : '');
+            $output  .= '; ' . $this->gettext('except') . ' ' . join(', ', $exdates) . ($more ? '...' : '');
         }
 
         return $output;
     }
 
     /**
      * Generate the form for recurrence settings
      */
     public function recurrence_form($attrib = array())
     {
         switch ($attrib['part']) {
             // frequency selector
             case 'frequency':
                 $select = new html_select(array('name' => 'frequency', 'id' => 'edit-recurrence-frequency', 'class' => 'form-control'));
                 $select->add($this->gettext('never'),   '');
                 $select->add($this->gettext('daily'),   'DAILY');
                 $select->add($this->gettext('weekly'),  'WEEKLY');
                 $select->add($this->gettext('monthly'), 'MONTHLY');
                 $select->add($this->gettext('yearly'),  'YEARLY');
                 $select->add($this->gettext('rdate'),   'RDATE');
                 $html = html::label(array('for' => 'edit-recurrence-frequency', 'class' => 'col-form-label col-sm-2'), $this->gettext('frequency'))
                     . html::div('col-sm-10', $select->show(''));
                 break;
 
             // daily recurrence
             case 'daily':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-daily'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-daily', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('days')))));
                 break;
 
             // weekly recurrence form
             case 'weekly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-weekly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-weekly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('weeks')))));
 
                 // weekday selection
                 $daymap   = array('sun','mon','tue','wed','thu','fri','sat');
                 $checkbox = new html_checkbox(array('name' => 'byday', 'class' => 'edit-recurrence-weekly-byday'));
                 $first    = $this->rc->config->get('calendar_first_day', 1);
 
                 for ($weekdays = '', $j = $first; $j <= $first+6; $j++) {
                     $d = $j % 7;
                     $weekdays .= html::label(array('class' => 'weekday'),
                         $checkbox->show('', array('value' => strtoupper(substr($daymap[$d], 0, 2)))) .
                         $this->gettext($daymap[$d])
                     ) . ' ';
                 }
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bydays'))
                     . html::div('col-sm-10 form-control-plaintext', $weekdays));
                 break;
 
             // monthly recurrence form
             case 'monthly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-monthly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-monthly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('months')))));
 
                 $checkbox = new html_checkbox(array('name' => 'bymonthday', 'class' => 'edit-recurrence-monthly-bymonthday'));
                 for ($monthdays = '', $d = 1; $d <= 31; $d++) {
                     $monthdays .= html::label(array('class' => 'monthday'), $checkbox->show('', array('value' => $d)) . $d);
                     $monthdays .= $d % 7 ? ' ' : html::br();
                 }
 
                 // rule selectors
                 $radio = new html_radiobutton(array('name' => 'repeatmode', 'class' => 'edit-recurrence-monthly-mode'));
                 $table = new html_table(array('cols' => 2, 'border' => 0, 'cellpadding' => 0, 'class' => 'formtable'));
                 $table->add('label', html::label(null, $radio->show('BYMONTHDAY', array('value' => 'BYMONTHDAY')) . ' ' . $this->gettext('each')));
                 $table->add(null, $monthdays);
                 $table->add('label', html::label(null, $radio->show('', array('value' => 'BYDAY')) . ' ' . $this->gettext('every')));
                 $table->add('recurrence-onevery', $this->rrule_selectors($attrib['part']));
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bydays'))
                     . html::div('col-sm-10 form-control-plaintext', $table->show()));
                 break;
 
             // annually recurrence form
             case 'yearly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-yearly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-yearly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('years')))));
 
                 // month selector
                 $monthmap = array('','jan','feb','mar','apr','may','jun','jul','aug','sep','oct','nov','dec');
                 $checkbox = new html_checkbox(array('name' => 'bymonth', 'class' => 'edit-recurrence-yearly-bymonth'));
 
                 for ($months = '', $m = 1; $m <= 12; $m++) {
                     $months .= html::label(array('class' => 'month'), $checkbox->show(null, array('value' => $m)) . $this->gettext($monthmap[$m]));
                     $months .= $m % 4 ? ' ' : html::br();
                 }
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bymonths'))
                     . html::div('col-sm-10 form-control-plaintext',
                         html::div(array('id' => 'edit-recurrence-yearly-bymonthblock'), $months)
                         . html::div('recurrence-onevery', $this->rrule_selectors($attrib['part'], '---'))
                     ));
                 break;
 
             // end of recurrence form
             case 'until':
                 $radio  = new html_radiobutton(array('name' => 'repeat', 'class' => 'edit-recurrence-until'));
                 $select = $this->interval_selector(array('name' => 'times', 'id' => 'edit-recurrence-repeat-times', 'class' => 'form-control'));
                 $input  = new html_inputfield(array('name' => 'untildate', 'id' => 'edit-recurrence-enddate', 'size' => '10', 'class' => 'form-control datepicker'));
 
                 $html = html::div('line first',
                     $radio->show('', array('value' => '', 'id' => 'edit-recurrence-repeat-forever'))
                         . ' ' . html::label('edit-recurrence-repeat-forever', $this->gettext('forever'))
                 );
 
                 $label = $this->gettext('ntimes');
                 if (strpos($label, '$') === 0) {
                     $label = str_replace('$n', '', $label);
                     $group  = $select->show(1)
                         . html::span('input-group-append', html::span('input-group-text', rcube::Q($label)));
                 }
                 else {
                     $label = str_replace('$n', '', $label);
                     $group  = html::span('input-group-prepend', html::span('input-group-text', rcube::Q($label)))
                         . $select->show(1);
                 }
 
                 $html .= html::div('line',
                     $radio->show('', array('value' => 'count', 'id' => 'edit-recurrence-repeat-count'))
                         . ' ' . html::label('edit-recurrence-repeat-count', $this->gettext('for'))
                         . ' ' . html::span('input-group', $group)
                 );
 
                 $html .= html::div('line',
                     $radio->show('', array('value' => 'until', 'id' => 'edit-recurrence-repeat-until', 'aria-label' => $this->gettext('untilenddate')))
                         . ' ' . html::label('edit-recurrence-repeat-until', $this->gettext('untildate'))
                         . ' ' . $input->show('', array('aria-label' => $this->gettext('untilenddate')))
                 );
 
                 $html = html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), ucfirst($this->gettext('recurrencend')))
                     . html::div('col-sm-10', $html));
                 break;
 
             case 'rdate':
                 $ul     = html::tag('ul', array('id' => 'edit-recurrence-rdates', 'class' => 'recurrence-rdates'), '');
                 $input  = new html_inputfield(array('name' => 'rdate', 'id' => 'edit-recurrence-rdate-input', 'size' => "10", 'class' => 'form-control datepicker'));
                 $button = new html_inputfield(array('type' => 'button', 'class' => 'button add', 'value' => $this->gettext('addrdate')));
 
                 $html = html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2', 'for' => 'edit-recurrence-rdate-input'), $this->gettext('bydates'))
                     . html::div('col-sm-10', $ul . html::div('inputform', $input->show() . $button->show())));
                 break;
         }
 
         return $html;
     }
 
     /**
      * Input field for interval selection
      */
     private function interval_selector($attrib)
     {
         $select = new html_select($attrib);
         $select->add(range(1,30), range(1,30));
         return $select;
     }
 
     /**
      * Drop-down menus for recurrence rules like "each last sunday of"
      */
     private function rrule_selectors($part, $noselect = null)
     {
         // rule selectors
         $select_prefix = new html_select(array('name' => 'bydayprefix', 'id' => "edit-recurrence-$part-prefix", 'class' => 'form-control'));
         if ($noselect) $select_prefix->add($noselect, '');
         $select_prefix->add(array(
                 $this->gettext('first'),
                 $this->gettext('second'),
                 $this->gettext('third'),
                 $this->gettext('fourth'),
                 $this->gettext('last')
             ),
             array(1, 2, 3, 4, -1));
 
         $select_wday = new html_select(array('name' => 'byday', 'id' => "edit-recurrence-$part-byday", 'class' => 'form-control'));
         if ($noselect) $select_wday->add($noselect, '');
 
         $daymap = array('sunday','monday','tuesday','wednesday','thursday','friday','saturday');
         $first = $this->rc->config->get('calendar_first_day', 1);
         for ($j = $first; $j <= $first+6; $j++) {
             $d = $j % 7;
             $select_wday->add($this->gettext($daymap[$d]), strtoupper(substr($daymap[$d], 0, 2)));
         }
 
         return $select_prefix->show() . '&nbsp;' . $select_wday->show();
     }
 
     /**
      * Convert the recurrence settings to be processed on the client
      */
     public function to_client_recurrence($recurrence, $allday = false)
     {
-        if ($recurrence['UNTIL']) {
+        if (!empty($recurrence['UNTIL'])) {
             $recurrence['UNTIL'] = $this->adjust_timezone($recurrence['UNTIL'], $allday)->format('c');
         }
 
         // format RDATE values
-        if (is_array($recurrence['RDATE'])) {
+        if (!empty($recurrence['RDATE'])) {
             $libcal = $this;
             $recurrence['RDATE'] = array_map(function($rdate) use ($libcal) {
                 return $libcal->adjust_timezone($rdate, true)->format('c');
-            }, $recurrence['RDATE']);
+            }, (array) $recurrence['RDATE']);
         }
 
         unset($recurrence['EXCEPTIONS']);
 
         return $recurrence;
     }
 
     /**
      * Process the alarms values submitted by the client
      */
     public function from_client_recurrence($recurrence, $start = null)
     {
         if (is_array($recurrence) && !empty($recurrence['UNTIL'])) {
             $recurrence['UNTIL'] = new DateTime($recurrence['UNTIL'], $this->timezone);
         }
 
-        if (is_array($recurrence) && is_array($recurrence['RDATE'])) {
+        if (is_array($recurrence) && !empty($recurrence['RDATE'])) {
             $tz = $this->timezone;
             $recurrence['RDATE'] = array_map(function($rdate) use ($tz, $start) {
                 try {
                     $dt = new DateTime($rdate, $tz);
                     if (is_a($start, 'DateTime'))
                         $dt->setTime($start->format('G'), $start->format('i'));
                     return $dt;
                 }
                 catch (Exception $e) {
                     return null;
                 }
             }, $recurrence['RDATE']);
         }
 
         return $recurrence;
     }
 
 
     /*********  iTip message detection  *********/
 
     /**
      * Check mail message structure of there are .ics files attached
      */
     public function mail_message_load($p)
     {
         $this->ical_message = $p['object'];
         $itip_part          = null;
 
         // check all message parts for .ics files
         foreach ((array)$this->ical_message->mime_parts as $part) {
             if (self::part_is_vcalendar($part, $this->ical_message)) {
                 if ($part->ctype_parameters['method'])
                     $itip_part = $part->mime_id;
                 else
                     $this->ical_parts[] = $part->mime_id;
             }
         }
 
         // priorize part with method parameter
         if ($itip_part) {
             $this->ical_parts = array($itip_part);
         }
     }
 
     /**
      * Getter for the parsed iCal objects attached to the current email message
      *
      * @return object libvcalendar parser instance with the parsed objects
      */
     public function get_mail_ical_objects()
     {
         // create parser and load ical objects
         if (!$this->mail_ical_parser) {
             $this->mail_ical_parser = $this->get_ical();
 
             foreach ($this->ical_parts as $mime_id) {
                 $part    = $this->ical_message->mime_parts[$mime_id];
                 $charset = $part->ctype_parameters['charset'] ?: RCUBE_CHARSET;
                 $this->mail_ical_parser->import($this->ical_message->get_part_body($mime_id, true), $charset);
 
                 // check if the parsed object is an instance of a recurring event/task
                 array_walk($this->mail_ical_parser->objects, 'libcalendaring::identify_recurrence_instance');
 
                 // stop on the part that has an iTip method specified
                 if (count($this->mail_ical_parser->objects) && $this->mail_ical_parser->method) {
                     $this->mail_ical_parser->message_date = $this->ical_message->headers->date;
                     $this->mail_ical_parser->mime_id = $mime_id;
 
                     // store the message's sender address for comparisons
                     $from = rcube_mime::decode_address_list($this->ical_message->headers->from, 1, true, null, true);
                     $this->mail_ical_parser->sender = !empty($from) ? $from[1] : '';
 
                     if (!empty($this->mail_ical_parser->sender)) {
                         foreach ($this->mail_ical_parser->objects as $i => $object) {
                             $this->mail_ical_parser->objects[$i]['_sender'] = $this->mail_ical_parser->sender;
                             $this->mail_ical_parser->objects[$i]['_sender_utf'] = rcube_utils::idn_to_utf8($this->mail_ical_parser->sender);
                         }
                     }
 
                     break;
                 }
             }
         }
 
         return $this->mail_ical_parser;
     }
 
     /**
      * Read the given mime message from IMAP and parse ical data
      *
      * @param string Mailbox name
      * @param string Message UID
      * @param string Message part ID and object index (e.g. '1.2:0')
      * @param string Object type filter (optional)
      *
      * @return array Hash array with the parsed iCal 
      */
     public function mail_get_itip_object($mbox, $uid, $mime_id, $type = null)
     {
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             list($mime_id, $index) = explode(':', $mime_id);
 
             $part    = $imap->get_message_part($uid, $mime_id);
             $headers = $imap->get_message_headers($uid);
             $parser  = $this->get_ical();
 
             if ($part->ctype_parameters['charset']) {
                 $charset = $part->ctype_parameters['charset'];
             }
 
             if ($part) {
                 $objects = $parser->import($part, $charset);
             }
         }
 
         // successfully parsed events/tasks?
         if (!empty($objects) && ($object = $objects[$index]) && (!$type || $object['_type'] == $type)) {
             if ($parser->method)
                 $object['_method'] = $parser->method;
 
             // store the message's sender address for comparisons
             $from = rcube_mime::decode_address_list($headers->from, 1, true, null, true);
             $object['_sender'] = !empty($from) ? $from[1] : '';
             $object['_sender_utf'] = rcube_utils::idn_to_utf8($object['_sender']);
 
             // check if this is an instance of a recurring event/task
             self::identify_recurrence_instance($object);
 
             return $object;
         }
 
         return null;
     }
 
     /**
      * Checks if specified message part is a vcalendar data
      *
      * @param rcube_message_part Part object
      * @param rcube_message      Message object
      *
      * @return boolean True if part is of type vcard
      */
     public static function part_is_vcalendar($part, $message = null)
     {
         // First check if the message is "valid" (i.e. not multipart/report)
         if ($message) {
             $level = explode('.', $part->mime_id);
 
             while (array_pop($level) !== null) {
                 $id     = join('.', $level) ?: 0;
                 $parent = !empty($message->mime_parts[$id]) ? $message->mime_parts[$id] : null;
                 if ($parent && $parent->mimetype == 'multipart/report') {
                     return false;
                 }
             }
         }
 
         return (
             in_array($part->mimetype, array('text/calendar', 'text/x-vcalendar', 'application/ics')) ||
             // Apple sends files as application/x-any (!?)
             ($part->mimetype == 'application/x-any' && !empty($part->filename) && preg_match('/\.ics$/i', $part->filename))
         );
     }
 
     /**
      * Single occourrences of recurring events are identified by their RECURRENCE-ID property
      * in iCal which is represented as 'recurrence_date' in our internal data structure.
      *
      * Check if such a property exists and derive the '_instance' identifier and '_savemode'
      * attributes which are used in the storage backend to identify the nested exception item.
      */
     public static function identify_recurrence_instance(&$object)
     {
         // for savemode=all, remove recurrence instance identifiers
         if (!empty($object['_savemode']) && $object['_savemode'] == 'all' && $object['recurrence']) {
             unset($object['_instance'], $object['recurrence_date']);
         }
         // set instance and 'savemode' according to recurrence-id
         else if (!empty($object['recurrence_date']) && is_a($object['recurrence_date'], 'DateTime')) {
             $object['_instance'] = self::recurrence_instance_identifier($object);
             $object['_savemode'] = $object['thisandfuture'] ? 'future' : 'current';
         }
         else if (!empty($object['recurrence_id']) && !empty($object['_instance'])) {
             if (strlen($object['_instance']) > 4) {
                 $object['recurrence_date'] = rcube_utils::anytodatetime($object['_instance'], $object['start']->getTimezone());
             }
             else {
                 $object['recurrence_date'] = clone $object['start'];
             }
         }
     }
 
     /**
      * Return a date() format string to render identifiers for recurrence instances
      *
      * @param array Hash array with event properties
      * @return string Format string
      */
     public static function recurrence_id_format($event)
     {
-        return $event['allday'] ? 'Ymd' : 'Ymd\THis';
+        return !empty($event['allday']) ? 'Ymd' : 'Ymd\THis';
     }
 
     /**
      * Return the identifer for the given instance of a recurring event
      *
      * @param array Hash array with event properties
      * @param bool  All-day flag from the main event
      *
      * @return mixed Format string or null if identifier cannot be generated
      */
     public static function recurrence_instance_identifier($event, $allday = null)
     {
-        $instance_date = $event['recurrence_date'] ?: $event['start'];
+        $instance_date = !empty($event['recurrence_date']) ? $event['recurrence_date'] : $event['start'];
 
-        if ($instance_date && is_a($instance_date, 'DateTime')) {
+        if ($instance_date instanceof DateTime) {
             // According to RFC5545 (3.8.4.4) RECURRENCE-ID format should
             // be date/date-time depending on the main event type, not the exception
             if ($allday === null) {
-                $allday = $event['allday'];
+                $allday = !empty($event['allday']);
             }
 
             return $instance_date->format($allday ? 'Ymd' : 'Ymd\THis');
         }
     }
 
 
     /*********  Attendee handling functions  *********/
 
     /**
      * Handler for attendee group expansion requests
      */
     public function expand_attendee_group()
     {
         $id     = rcube_utils::get_input_value('id', rcube_utils::INPUT_POST);
         $data   = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
         $result = array('id' => $id, 'members' => array());
         $maxnum = 500;
 
         // iterate over all autocomplete address books (we don't know the source of the group)
         foreach ((array)$this->rc->config->get('autocomplete_addressbooks', 'sql') as $abook_id) {
             if (($abook = $this->rc->get_address_book($abook_id)) && $abook->groups) {
                 foreach ($abook->list_groups($data['name'], 1) as $group) {
                     // this is the matching group to expand
                     if (in_array($data['email'], (array)$group['email'])) {
                         $abook->set_pagesize($maxnum);
                         $abook->set_group($group['ID']);
 
                         // get all members
                         $res = $abook->list_records($this->rc->config->get('contactlist_fields'));
 
                         // handle errors (e.g. sizelimit, timelimit)
                         if ($abook->get_error()) {
                             $result['error'] = $this->rc->gettext('expandattendeegrouperror', 'libcalendaring');
                             $res = false;
                         }
                         // check for maximum number of members (we don't wanna bloat the UI too much)
                         else if ($res->count > $maxnum) {
                             $result['error'] = $this->rc->gettext('expandattendeegroupsizelimit', 'libcalendaring');
                             $res = false;
                         }
 
                         while ($res && ($member = $res->iterate())) {
                             $emails = (array)$abook->get_col_values('email', $member, true);
                             if (!empty($emails) && ($email = array_shift($emails))) {
                                 $result['members'][] = array(
                                     'email' => $email,
                                     'name' => rcube_addressbook::compose_list_name($member),
                                 );
                             }
                         }
 
                         break 2;
                     }
                 }
             }
         }
 
         $this->rc->output->command('plugin.expand_attendee_callback', $result);
     }
 
     /**
      * Merge attendees of the old and new event version
      * with keeping current user and his delegatees status
      *
      * @param array &$new   New object data
      * @param array $old    Old object data
      * @param bool  $status New status of the current user
      */
     public function merge_attendees(&$new, $old, $status = null)
     {
         if (empty($status)) {
             $emails    = $this->get_user_emails();
             $delegates = array();
             $attendees = array();
 
             // keep attendee status of the current user
             foreach ((array) $new['attendees'] as $i => $attendee) {
                 if (empty($attendee['email'])) {
                     continue;
                 }
 
                 $attendees[] = $email = strtolower($attendee['email']);
 
                 if (in_array($email, $emails)) {
                     foreach ($old['attendees'] as $_attendee) {
                         if ($attendee['email'] == $_attendee['email']) {
                             $new['attendees'][$i] = $_attendee;
                             if ($_attendee['status'] == 'DELEGATED' && ($email = $_attendee['delegated-to'])) {
                                 $delegates[] = strtolower($email);
                             }
 
                             break;
                         }
                     }
                 }
             }
 
             // make sure delegated attendee is not lost
             foreach ($delegates as $delegatee) {
                 if (!in_array($delegatee, $attendees)) {
                     foreach ((array) $old['attendees'] as $attendee) {
                         if ($attendee['email'] && ($email = strtolower($attendee['email'])) && $email == $delegatee) {
                             $new['attendees'][] = $attendee;
                             break;
                         }
                     }
                 }
             }
         }
 
         // We also make sure that status of any attendee
         // is not overriden by NEEDS-ACTION if it was already set
         // which could happen if you work with shared events
         foreach ((array) $new['attendees'] as $i => $attendee) {
             if ($attendee['email'] && $attendee['status'] == 'NEEDS-ACTION') {
                 foreach ($old['attendees'] as $_attendee) {
                     if ($attendee['email'] == $_attendee['email']) {
                         $new['attendees'][$i]['status'] = $_attendee['status'];
                         unset($new['attendees'][$i]['rsvp']);
                         break;
                     }
                 }
             }
         }
     }
 
 
     /*********  Static utility functions  *********/
 
     /**
      * Convert the internal structured data into a vcalendar rrule 2.0 string
      */
     public static function to_rrule($recurrence, $allday = false)
     {
         if (is_string($recurrence)) {
             return $recurrence;
         }
 
         $rrule = '';
         foreach ((array)$recurrence as $k => $val) {
             $k = strtoupper($k);
             switch ($k) {
             case 'UNTIL':
                 // convert to UTC according to RFC 5545
                 if (is_a($val, 'DateTime')) {
                     if (!$allday && empty($val->_dateonly)) {
                         $until = clone $val;
                         $until->setTimezone(new DateTimeZone('UTC'));
                         $val = $until->format('Ymd\THis\Z');
                     }
                     else {
                         $val = $val->format('Ymd');
                     }
                 }
                 break;
             case 'RDATE':
             case 'EXDATE':
                 foreach ((array)$val as $i => $ex) {
                     if (is_a($ex, 'DateTime')) {
                         $val[$i] = $ex->format('Ymd\THis');
                     }
                 }
                 $val = join(',', (array)$val);
                 break;
             case 'EXCEPTIONS':
                 continue 2;
             }
 
             if (strlen($val)) {
                 $rrule .= $k . '=' . $val . ';';
             }
         }
 
         return rtrim($rrule, ';');
     }
 
     /**
      * Convert from fullcalendar date format to PHP date() format string
      */
     public static function to_php_date_format($from)
     {
         // "dd.MM.yyyy HH:mm:ss" => "d.m.Y H:i:s"
         return strtr(strtr($from, array(
             'YYYY' => 'Y',
             'YY'   => 'y',
             'yyyy' => 'Y',
             'yy'   => 'y',
             'MMMM' => 'F',
             'MMM'  => 'M',
             'MM'   => 'm',
             'M'    => 'n',
             'dddd' => 'l',
             'ddd'  => 'D',
             'DD'   => 'd',
             'D'    => 'j',
             'HH'   => '**',
             'hh'   => '%%',
             'H'    => 'G',
             'h'    => 'g',
             'mm'   => 'i',
             'ss'   => 's',
             'TT'   => 'A',
             'tt'   => 'a',
             'T'    => 'A',
             't'    => 'a',
             'u'    => 'c',
         )), array(
             '**'   => 'H',
             '%%'   => 'h',
         ));
     }
 
     /**
      * Convert from PHP date() format to fullcalendar (MomentJS) format string
      */
     public static function from_php_date_format($from)
     {
         // "d.m.Y H:i:s" => "dd.MM.yyyy HH:mm:ss"
         return strtr($from, array(
             'y' => 'YY',
             'Y' => 'YYYY',
             'M' => 'MMM',
             'F' => 'MMMM',
             'm' => 'MM',
             'n' => 'M',
             'j' => 'D',
             'd' => 'DD',
             'D' => 'ddd',
             'l' => 'dddd',
             'H' => 'HH',
             'h' => 'hh',
             'G' => 'H',
             'g' => 'h',
             'i' => 'mm',
             's' => 'ss',
             'c' => '',
         ));
     }
 }
diff --git a/plugins/libcalendaring/libvcalendar.php b/plugins/libcalendaring/libvcalendar.php
index 3dda65d4..ea311b23 100644
--- a/plugins/libcalendaring/libvcalendar.php
+++ b/plugins/libcalendaring/libvcalendar.php
@@ -1,1532 +1,1532 @@
 <?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 libvcalendar 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 'CLASS':
             case 'X-CALENDARSERVER-ACCESS':
                 $event['sensitivity'] = strtolower($value);
                 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 = $attendee['schedule-agent'];
                     }
                 }
                 else if ($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 DateTime) {
             $this->_apply_timezone($event['start']);
         }
         else {
             unset($event['start']);
         }
 
         if (!empty($event['end']) && $event['end'] instanceof DateTime) {
             $this->_apply_timezone($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 ($date->_dateonly) {
+        if (!empty($date->_dateonly)) {
             $dt = new 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 $as_array ? array() : null;
         }
         else if ($prop instanceof VObject\Property\iCalendar\DateTime) {
             if (count($prop->getDateTimes()) > 1) {
                 $dt = array();
                 $dateonly = !$prop->hasTime();
                 foreach ($prop->getDateTimes() as $item) {
                     $item->_dateonly = $dateonly;
                     $dt[] = $item;
                 }
             }
             else {
                 $dt = $prop->getDateTime();
                 if (!$prop->hasTime()) {
                     $dt->_dateonly = true;
                 }
             }
         }
         else if ($prop instanceof VObject\Property\iCalendar\Period) {
             $dt = array();
             foreach ($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);
                     }
                     $dt[] = array($start, $end);
                 }
                 catch (Exception $e) {
                     // ignore single date parse errors
                 }
             }
         }
         else if ($prop instanceof \DateTime) {
             $dt = $prop;
         }
 
         // force return value to array if requested
         if ($as_array && !is_array($dt)) {
             $dt = empty($dt) ? array() : array($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();
         }
     }
 
     /**
      * 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 DateTime) {
             $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['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 DateTime) {
                         $ve->add($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['sensitivity']))
             $ve->add('CLASS', strtoupper($event['sensitivity']));
 
         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 DateTime) {
                     $va->add($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 DateTime) {
                 $va->add($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');
                 }
                 $this->_to_ical($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 ***/
 
     function current()
     {
         return $this->objects[$this->iteratorkey];
     }
 
     function key()
     {
         return $this->iteratorkey;
     }
 
     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();
     }
 
     function rewind()
     {
         $this->iteratorkey = 0;
     }
 
     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 = array(
         // vCard
         'N',
         'ADR',
         'ORG',
         'GENDER',
         'LOCATION',
         // iCalendar
         'REQUEST-STATUS',
     );
 }