diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index 8e031a41..552bafc8 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -1,4014 +1,4014 @@
 <?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/>.
  */
 
 #[AllowDynamicProperties]
 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 $dst_active;
     public $ui;
 
     public $defaults = [
         'calendar_default_view' => "agendaWeek",
         'calendar_timeslots'    => 2,
         'calendar_work_start'   => 6,
         'calendar_work_end'     => 18,
         'calendar_agenda_range' => 60,
         'calendar_show_weekno'  => 0,
         'calendar_first_day'    => 1,
         'calendar_first_hour'   => 6,
         'calendar_time_format'  => null,
         'calendar_event_coloring'      => 0,
         'calendar_time_indicator'      => true,
         'calendar_allow_invite_shared' => false,
         'calendar_itip_send_option'    => 3,
         'calendar_itip_after_action'   => 0,
     ];
 
     // These are implemented with __get()
     //  private $ical;
     //  private $itip;
     //  private $driver;
 
 
     /**
      * Plugin initialization.
      */
     function init()
     {
         $this->rc = rcube::get_instance();
 
         $this->register_task('calendar', 'calendar');
 
         // load calendar configuration
         $this->load_config();
 
         // catch iTIP confirmation requests that don're require a valid session
         if ($this->rc->action == 'attend' && !empty($_REQUEST['_t'])) {
             $this->add_hook('startup', [$this, 'itip_attend_response']);
         }
         else if ($this->rc->action == 'feed' && !empty($_REQUEST['_cal'])) {
             $this->add_hook('startup', [$this, 'ical_feed_export']);
         }
         else if ($this->rc->task != 'login') {
             // default startup routine
             $this->add_hook('startup', [$this, 'startup']);
         }
 
         $this->add_hook('user_delete', [$this, 'user_delete']);
     }
 
     /**
      * Setup basic plugin environment and UI
      */
     protected function setup()
     {
         $this->require_plugin('libcalendaring');
         $this->require_plugin('libkolab');
 
         require $this->home . '/lib/calendar_ui.php';
 
         // load localizations
         $this->add_texts('localization/', $this->rc->task == 'calendar' && (!$this->rc->action || $this->rc->action == 'print'));
 
         $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;
         $this->ui              = new calendar_ui($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());
             }
 
-            // A hack to replace "Edit/Share Calendar" label with "Edit calendar", for CalDAV driver
-            if ($args['task'] == 'calendar' && $this->rc->config->get('calendar_driver', 'database') === 'caldav') {
+            // A hack to replace "Edit/Share Calendar" label with "Edit calendar", for non-Kolab driver
+            if ($args['task'] == 'calendar' && $this->rc->config->get('calendar_driver', 'database') !== 'kolab') {
                 $merge = ['calendar.editcalendar' => $this->gettext('edcalendar')];
                 $this->rc->load_language(null, [], $merge);
                 $this->rc->output->command('add_label', $merge);
             }
         }
 
         if ($args['task'] == 'calendar' && $args['action'] != 'save-pref') {
             if ($args['action'] != 'upload') {
                 $this->load_driver();
             }
 
             // register calendar actions
             $this->register_action('index', [$this, 'calendar_view']);
             $this->register_action('event', [$this, 'event_action']);
             $this->register_action('calendar', [$this, 'calendar_action']);
             $this->register_action('count', [$this, 'count_events']);
             $this->register_action('load_events', [$this, 'load_events']);
             $this->register_action('export_events', [$this, 'export_events']);
             $this->register_action('import_events', [$this, 'import_events']);
             $this->register_action('upload', [$this, 'attachment_upload']);
             $this->register_action('get-attachment', [$this, 'attachment_get']);
             $this->register_action('freebusy-status', [$this, 'freebusy_status']);
             $this->register_action('freebusy-times', [$this, 'freebusy_times']);
             $this->register_action('randomdata', [$this, 'generate_randomdata']);
             $this->register_action('print', [$this,'print_view']);
             $this->register_action('mailimportitip', [$this, 'mail_import_itip']);
             $this->register_action('mailimportattach', [$this, 'mail_import_attachment']);
             $this->register_action('dialog-ui', [$this, 'mail_message2event']);
             $this->register_action('check-recent', [$this, 'check_recent']);
             $this->register_action('itip-status', [$this, 'event_itip_status']);
             $this->register_action('itip-remove', [$this, 'event_itip_remove']);
             $this->register_action('itip-decline-reply', [$this, 'mail_itip_decline_reply']);
             $this->register_action('itip-delegate', [$this, 'mail_itip_delegate']);
             $this->register_action('resources-list', [$this, 'resources_list']);
             $this->register_action('resources-owner', [$this, 'resources_owner']);
             $this->register_action('resources-calendar', [$this, 'resources_calendar']);
             $this->register_action('resources-autocomplete', [$this, 'resources_autocomplete']);
             $this->register_action('talk-room-create', [$this, 'talk_room_create']);
 
             $this->add_hook('refresh', [$this, 'refresh']);
 
             // remove undo information...
             if (!empty($_SESSION['calendar_event_undo'])) {
                 $undo = $_SESSION['calendar_event_undo'];
                 // ...after timeout
                 $undo_time = $this->rc->config->get('undo_timeout', 0);
                 if ($undo['ts'] < time() - $undo_time) {
                     $this->rc->session->remove('calendar_event_undo');
                     // @TODO: do EXPUNGE on kolab objects?
                 }
             }
         }
         else if ($args['task'] == 'settings') {
             // add hooks for Calendar settings
             $this->add_hook('preferences_sections_list', [$this, 'preferences_sections_list']);
             $this->add_hook('preferences_list', [$this, 'preferences_list']);
             $this->add_hook('preferences_save', [$this, 'preferences_save']);
         }
         else if ($args['task'] == 'mail') {
             // hooks to catch event invitations on incoming mails
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 $this->add_hook('template_object_messagebody', [$this, 'mail_messagebody_html']);
             }
 
             // add 'Create event' item to message menu
             if ($this->api->output->type == 'html' && (empty($_GET['_rel']) || $_GET['_rel'] != 'event')) {
                 $this->api->output->add_label('calendar.createfrommail');
                 $this->api->add_content(
                     html::tag('li', ['role' => 'menuitem'],
                         $this->api->output->button([
                             'command'  => 'calendar-create-from-mail',
                             'label'    => 'calendar.createfrommail',
                             'type'     => 'link',
                             'classact' => 'icon calendarlink active',
                             'class'    => 'icon calendarlink disabled',
                             'innerclass' => 'icon calendar',
                         ])
                     ),
                     'messagemenu'
                 );
             }
 
             $this->add_hook('messages_list', [$this, 'mail_messages_list']);
             $this->add_hook('message_compose', [$this, 'mail_message_compose']);
         }
         else if ($args['task'] == 'addressbook') {
             if ($this->rc->config->get('calendar_contact_birthdays')) {
                 $this->add_hook('contact_update', [$this, 'contact_update']);
                 $this->add_hook('contact_create', [$this, 'contact_update']);
             }
         }
 
         // add hooks to display alarms
         $this->add_hook('pending_alarms', [$this, 'pending_alarms']);
         $this->add_hook('dismiss_alarms', [$this, 'dismiss_alarms']);
     }
 
     /**
      * Helper method to load the backend driver according to local config
      */
     private function load_driver()
     {
         if (!empty($this->driver)) {
             return;
         }
 
         $driver_name = $this->rc->config->get('calendar_driver', 'database');
         $driver_class = $driver_name . '_driver';
 
         require_once $this->home . '/drivers/calendar_driver.php';
         require_once $this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php';
 
         $this->driver = new $driver_class($this);
 
         if ($this->driver->undelete) {
             $this->driver->undelete = $this->rc->config->get('undo_timeout', 0) > 0;
         }
     }
 
     /**
      * Load iTIP functions
      */
     private function load_itip()
     {
         if (empty($this->itip)) {
             require_once $this->home . '/lib/calendar_itip.php';
 
             $this->itip = new calendar_itip($this);
 
             if ($this->rc->config->get('kolab_invitation_calendars')) {
                 $this->itip->set_rsvp_actions(['accepted','tentative','declined','delegated','needs-action']);
             }
         }
 
         return $this->itip;
     }
 
     /**
      * Load iCalendar functions
      */
     public function get_ical()
     {
         if (empty($this->ical)) {
             $this->ical = libcalendaring::get_ical();
         }
 
         return $this->ical;
     }
 
     /**
      * Get properties of the calendar this user has specified as default
      */
     public function get_default_calendar($calendars = null)
     {
         if ($calendars === null) {
             $filter    = calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_WRITEABLE;
             $calendars = $this->driver->list_calendars($filter);
         }
 
         $default_id = $this->rc->config->get('calendar_default_calendar');
         $calendar   = !empty($calendars[$default_id]) ? $calendars[$default_id] : null;
         $first      = null;
 
         if (!$calendar) {
             foreach ($calendars as $cal) {
                 if (!empty($cal['default']) && $cal['editable']) {
                     $calendar = $cal;
                 }
                 if ($cal['editable']) {
                     $first = $cal;
                 }
             }
         }
 
         return $calendar ?: $first;
     }
 
     /**
      * Render the main calendar view from skin template
      */
     function calendar_view()
     {
         $this->rc->output->set_pagetitle($this->gettext('calendar'));
 
         // Add JS files to the page header
         $this->ui->addJS();
 
         $this->ui->init_templates();
         $this->rc->output->add_label('lowest','low','normal','high','highest','delete',
             'cancel','uploading','noemailwarning','close'
         );
 
         // initialize attendees autocompletion
         $this->rc->autocomplete_init();
 
         $this->rc->output->set_env('timezone', $this->timezone->getName());
         $this->rc->output->set_env('calendar_driver', $this->rc->config->get('calendar_driver'), false);
         $this->rc->output->set_env('calendar_resources', (bool)$this->rc->config->get('calendar_resources_driver'));
         $this->rc->output->set_env('identities-selector', $this->ui->identity_select([
                 'id'         => 'edit-identities-list',
                 'aria-label' => $this->gettext('roleorganizer'),
                 'class'      => 'form-control custom-select',
         ]));
 
         $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
         if (in_array($view, ['agendaWeek', 'agendaDay', 'month', 'list'])) {
             $this->rc->output->set_env('view', $view);
         }
 
         if ($date = rcube_utils::get_input_value('date', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('date', $date);
         }
 
         if ($msgref = rcube_utils::get_input_value('itip', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('itip_events', $this->itip_events($msgref));
         }
 
         $this->rc->output->send('calendar.calendar');
     }
 
     /**
      * Handler for preferences_sections_list hook.
      * Adds Calendar settings sections into preferences sections list.
      *
      * @param array Original parameters
      *
      * @return array Modified parameters
      */
     function preferences_sections_list($p)
     {
         $p['list']['calendar'] = [
             'id'      => 'calendar',
             'section' => $this->gettext('calendar'),
         ];
 
         return $p;
     }
 
     /**
      * Handler for preferences_list hook.
      * Adds options blocks into Calendar settings sections in Preferences.
      *
      * @param array Original parameters
      *
      * @return array Modified parameters
      */
     function preferences_list($p)
     {
         if ($p['section'] != 'calendar') {
             return $p;
         }
 
         $no_override = array_flip((array) $this->rc->config->get('dont_override'));
 
         $p['blocks']['view']['name'] = $this->gettext('mainoptions');
 
         if (!isset($no_override['calendar_default_view'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_default_view';
             $view = $this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view']);
 
             $select = new html_select(['name' => '_default_view', 'id' => $field_id]);
             $select->add($this->gettext('day'), "agendaDay");
             $select->add($this->gettext('week'), "agendaWeek");
             $select->add($this->gettext('month'), "month");
             $select->add($this->gettext('agenda'), "list");
 
             $p['blocks']['view']['options']['default_view'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('default_view'))),
                 'content' => $select->show($view == 'table' ? 'list' : $view),
             ];
         }
 
         if (!isset($no_override['calendar_timeslots'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id  = 'rcmfd_timeslots';
             $choices   = ['1', '2', '3', '4', '6'];
             $timeslots = $this->rc->config->get('calendar_timeslots', $this->defaults['calendar_timeslots']);
 
             $select = new html_select(['name' => '_timeslots', 'id' => $field_id]);
             $select->add($choices, $choices);
 
             $p['blocks']['view']['options']['timeslots'] = [
                 'title' => html::label($field_id, rcube::Q($this->gettext('timeslots'))),
                 'content' => $select->show(strval($timeslots)),
             ];
         }
 
         if (!isset($no_override['calendar_first_day'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id  = 'rcmfd_firstday';
             $first_day = $this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
 
             $select = new html_select(['name' => '_first_day', 'id' => $field_id]);
             $select->add($this->gettext('sunday'), '0');
             $select->add($this->gettext('monday'), '1');
             $select->add($this->gettext('tuesday'), '2');
             $select->add($this->gettext('wednesday'), '3');
             $select->add($this->gettext('thursday'), '4');
             $select->add($this->gettext('friday'), '5');
             $select->add($this->gettext('saturday'), '6');
 
             $p['blocks']['view']['options']['first_day'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('first_day'))),
                 'content' => $select->show(strval($first_day)),
             ];
         }
 
         if (!isset($no_override['calendar_first_hour'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $first_hour  = $this->rc->config->get('calendar_first_hour', $this->defaults['calendar_first_hour']);
             $time_format = $this->rc->config->get('calendar_time_format', $this->defaults['calendar_time_format']);
             $time_format = $this->rc->config->get('time_format', libcalendaring::to_php_date_format($time_format));
             $field_id    = 'rcmfd_firsthour';
 
             $select_hours = new html_select(['name' => '_first_hour', 'id' => $field_id]);
             for ($h = 0; $h < 24; $h++) {
                 $select_hours->add(date($time_format, mktime($h, 0, 0)), $h);
             }
 
             $p['blocks']['view']['options']['first_hour'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('first_hour'))),
                 'content' => $select_hours->show($first_hour),
             ];
         }
 
         if (!isset($no_override['calendar_work_start'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id   = 'rcmfd_workstart';
             $work_start = $this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']);
             $work_end   = $this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']);
 
             $p['blocks']['view']['options']['workinghours'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('workinghours'))),
                 'content' => html::div('input-group',
                     $select_hours->show($work_start, ['name' => '_work_start', 'id' => $field_id])
                     . html::span('input-group-append input-group-prepend', html::span('input-group-text',' &mdash; '))
                     . $select_hours->show($work_end, ['name' => '_work_end', 'id' => $field_id])
                 )
             ];
         }
 
         if (!isset($no_override['calendar_event_coloring'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_coloring';
             $mode     = $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
 
             $select_colors = new html_select(['name' => '_event_coloring', 'id' => $field_id]);
             $select_colors->add($this->gettext('coloringmode0'), 0);
             $select_colors->add($this->gettext('coloringmode1'), 1);
             $select_colors->add($this->gettext('coloringmode2'), 2);
             $select_colors->add($this->gettext('coloringmode3'), 3);
 
             $p['blocks']['view']['options']['eventcolors'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('eventcoloring'))),
                 'content' => $select_colors->show($mode),
             ];
         }
 
         // loading driver is expensive, don't do it if not needed
         $this->load_driver();
 
         if (!isset($no_override['calendar_default_alarm_type']) || !isset($no_override['calendar_default_alarm_offset'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $alarm_type = $alarm_offset = '';
 
             if (!isset($no_override['calendar_default_alarm_type'])) {
                 $field_id    = 'rcmfd_alarm';
                 $select_type = new html_select(['name' => '_alarm_type', 'id' => $field_id]);
                 $select_type->add($this->gettext('none'), '');
 
                 foreach ($this->driver->alarm_types as $type) {
                     $select_type->add($this->rc->gettext(strtolower("alarm{$type}option"), 'libcalendaring'), $type);
                 }
 
                 $alarm_type = $select_type->show($this->rc->config->get('calendar_default_alarm_type', ''));
             }
 
             if (!isset($no_override['calendar_default_alarm_offset'])) {
                 $field_id      = 'rcmfd_alarm';
                 $input_value   = new html_inputfield(['name' => '_alarm_value', 'id' => $field_id . 'value', 'size' => 3]);
                 $select_offset = new html_select(['name' => '_alarm_offset', 'id' => $field_id . 'offset']);
 
                 foreach (['-M','-H','-D','+M','+H','+D'] as $trigger) {
                     $select_offset->add($this->rc->gettext('trigger' . $trigger, 'libcalendaring'), $trigger);
                 }
 
                 $preset = libcalendaring::parse_alarm_value($this->rc->config->get('calendar_default_alarm_offset', '-15M'));
                 $alarm_offset = $input_value->show($preset[0]) . ' ' . $select_offset->show($preset[1]);
             }
 
             $p['blocks']['view']['options']['alarmtype'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('defaultalarmtype'))),
                 'content' => html::div('input-group', $alarm_type . ' ' . $alarm_offset),
             ];
         }
 
         if (!isset($no_override['calendar_default_calendar'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             // default calendar selection
             $field_id   = 'rcmfd_default_calendar';
             $filter     = calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_ACTIVE | calendar_driver::FILTER_INSERTABLE;
             $select_cal = new html_select(['name' => '_default_calendar', 'id' => $field_id, 'is_escaped' => true]);
 
             $default_calendar = null;
             foreach ((array) $this->driver->list_calendars($filter) as $id => $prop) {
                 $select_cal->add($prop['name'], strval($id));
                 if (!empty($prop['default'])) {
                     $default_calendar = $id;
                 }
             }
 
             $p['blocks']['view']['options']['defaultcalendar'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('defaultcalendar'))),
                 'content' => $select_cal->show($this->rc->config->get('calendar_default_calendar', $default_calendar)),
             ];
         }
 
         if (!isset($no_override['calendar_show_weekno'])) {
             if (empty($p['current'])) {
                 $p['blocks']['view']['content'] = true;
                 return $p;
             }
 
             $field_id   = 'rcmfd_show_weekno';
             $select = new html_select(['name' => '_show_weekno', 'id' => $field_id]);
             $select->add($this->gettext('weeknonone'), -1);
             $select->add($this->gettext('weeknodatepicker'), 0);
             $select->add($this->gettext('weeknoall'), 1);
 
             $p['blocks']['view']['options']['show_weekno'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('showweekno'))),
                 'content' => $select->show(intval($this->rc->config->get('calendar_show_weekno'))),
             ];
         }
 
         $p['blocks']['itip']['name'] = $this->gettext('itipoptions');
 
         // Invitations handling
         if (!isset($no_override['calendar_itip_after_action'])) {
             if (empty($p['current'])) {
                 $p['blocks']['itip']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_after_action';
             $select   = new html_select([
                     'name'     => '_after_action',
                     'id'       => $field_id,
                     'onchange' => "\$('#{$field_id}_select')[this.value == 4 ? 'show' : 'hide']()"
             ]);
 
             $select->add($this->gettext('afternothing'), '');
             $select->add($this->gettext('aftertrash'), 1);
             $select->add($this->gettext('afterdelete'), 2);
             $select->add($this->gettext('afterflagdeleted'), 3);
             $select->add($this->gettext('aftermoveto'), 4);
 
             $val    = $this->rc->config->get('calendar_itip_after_action', $this->defaults['calendar_itip_after_action']);
             $folder = null;
 
             if ($val !== null && $val !== '' && !is_int($val)) {
                 $folder = $val;
                 $val    = 4;
             }
 
             $folders = $this->rc->folder_selector([
                     'id'            => $field_id . '_select',
                     'name'          => '_after_action_folder',
                     'maxlength'     => 30,
                     'folder_filter' => 'mail',
                     'folder_rights' => 'w',
                     'style'         => $val !== 4 ? 'display:none' : '',
             ]);
 
             $p['blocks']['itip']['options']['after_action'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('afteraction'))),
                 'content' => html::div(
                     'input-group input-group-combo',
                     $select->show($val) . $folders->show($folder)
                 ),
             ];
         }
 
         // category definitions
         if (empty($this->driver->nocategories) && !isset($no_override['calendar_categories'])) {
             $p['blocks']['categories']['name'] = $this->gettext('categories');
 
             if (empty($p['current'])) {
                 $p['blocks']['categories']['content'] = true;
                 return $p;
             }
 
             $categories      = (array) $this->driver->list_categories();
             $categories_list = '';
 
             foreach ($categories as $name => $color) {
                 $key = md5($name);
                 $field_class = 'rcmfd_category_' . str_replace(' ', '_', $name);
                 $category_remove = html::span('input-group-append',
                     html::a([
                             'class'   => 'button icon delete input-group-text',
                             'onclick' => '$(this).parent().parent().remove()',
                             'title'   => $this->gettext('remove_category'),
                             'href'    => '#rcmfd_new_category',
                         ],
                         html::span('inner', $this->gettext('delete'))
                     )
                 );
 
                 $category_name  = new html_inputfield(array('name' => "_categories[$key]", 'class' => $field_class, 'size' => 30, 'disabled' => $this->driver->categoriesimmutable));
                 $category_color = new html_inputfield(array('name' => "_colors[$key]", 'class' => "$field_class colors", 'size' => 6));
                 $hidden         = '';
 
                 if (!empty($this->driver->categoriesimmutable)) {
                     $hidden =  html::tag('input', ['type' => 'hidden', 'name' => "_categories[$key]", 'value' => $name]);
                 }
 
                 $categories_list .= $hidden
                     . html::div('input-group', $category_name->show($name) . $category_color->show($color) . $category_remove);
             }
 
             $p['blocks']['categories']['options']['category_' . $name] = [
                 'content' => html::div(['id' => 'calendarcategories'], $categories_list),
             ];
 
             $field_id = 'rcmfd_new_category';
             $new_category = new html_inputfield(['name' => '_new_category', 'id' => $field_id, 'size' => 30]);
             $add_category = html::span('input-group-append',
                 html::a(
                     [
                         'type'    => 'button',
                         'class'   => 'button create input-group-text',
                         'title'   => $this->gettext('add_category'),
                         'onclick' => 'rcube_calendar_add_category()',
                         'href'    => '#rcmfd_new_category',
                     ],
                     html::span('inner', $this->gettext('add_category'))
                 )
             );
 
             $p['blocks']['categories']['options']['categories'] = [
                 'content' => html::div('input-group', $new_category->show('') . $add_category),
             ];
 
             $this->rc->output->add_label('delete', 'calendar.remove_category');
             $this->rc->output->add_script('
 function rcube_calendar_add_category() {
     var name = $("#rcmfd_new_category").val();
     if (name.length) {
         var button_label = rcmail.gettext("calendar.remove_category");
         var input = $("<input>").attr({type: "text", name: "_categories[]", size: 30, "class": "form-control"}).val(name);
         var color = $("<input>").attr({type: "text", name: "_colors[]", size: 6, "class": "colors form-control"}).val("000000");
         var button = $("<a>").attr({"class": "button icon delete input-group-text", title: button_label, href: "#rcmfd_new_category"})
             .click(function() { $(this).parent().parent().remove(); })
             .append($("<span>").addClass("inner").text(rcmail.gettext("delete")));
 
         $("<div>").addClass("input-group").append(input).append(color).append($("<span class=\'input-group-append\'>").append(button))
             .appendTo("#calendarcategories");
         color.minicolors(rcmail.env.minicolors_config || {});
         $("#rcmfd_new_category").val("");
     }
 }',
                 'foot'
             );
 
             $this->rc->output->add_script('
 $("#rcmfd_new_category").keypress(function(event) {
     if (event.which == 13) {
         rcube_calendar_add_category();
         event.preventDefault();
     }
 });',
                 'docready'
             );
 
             // load miniColors js/css files
             jqueryui::miniColors();
         }
 
         // virtual birthdays calendar
         if (!isset($no_override['calendar_contact_birthdays'])) {
             $p['blocks']['birthdays']['name'] = $this->gettext('birthdayscalendar');
 
             if (empty($p['current'])) {
                 $p['blocks']['birthdays']['content'] = true;
                 return $p;
             }
 
             $field_id = 'rcmfd_contact_birthdays';
             $input    = new html_checkbox([
                     'name'    => '_contact_birthdays',
                     'id'      => $field_id,
                     'value'   => 1,
                     'onclick' => '$(".calendar_birthday_props").prop("disabled",!this.checked)'
             ]);
 
             $p['blocks']['birthdays']['options']['contact_birthdays'] = [
                 'title'   => html::label($field_id, $this->gettext('displaybirthdayscalendar')),
                 'content' => $input->show($this->rc->config->get('calendar_contact_birthdays') ? 1 : 0),
             ];
 
             $input_attrib = [
                 'class'    => 'calendar_birthday_props',
                 'disabled' => !$this->rc->config->get('calendar_contact_birthdays'),
             ];
 
             $sources  = [];
             $checkbox = new html_checkbox(['name' => '_birthday_adressbooks[]'] + $input_attrib);
 
             foreach ($this->rc->get_address_sources(false, true) as $source) {
                 // Roundcube >= 1.5, Ignore Collected Recipients and Trusted Senders sources
                 if ((defined('rcube_addressbook::TYPE_RECIPIENT') && $source['id'] == (string) rcube_addressbook::TYPE_RECIPIENT)
                     || (defined('rcube_addressbook::TYPE_TRUSTED_SENDER') && $source['id'] == (string) rcube_addressbook::TYPE_TRUSTED_SENDER)
                 ) {
                     continue;
                 }
 
                 $active = in_array($source['id'], (array) $this->rc->config->get('calendar_birthday_adressbooks')) ? $source['id'] : '';
                 $sources[] = html::tag('li', null,
                     html::label(null,
                         $checkbox->show($active, ['value' => $source['id']])
                         . rcube::Q(!empty($source['realname']) ? $source['realname'] : $source['name'])
                     )
                 );
             }
 
             $p['blocks']['birthdays']['options']['birthday_adressbooks'] = [
                 'title'   => rcube::Q($this->gettext('birthdayscalendarsources')),
                 'content' => html::tag('ul', 'proplist', implode("\n", $sources)),
             ];
 
             $field_id = 'rcmfd_birthdays_alarm';
             $select_type = new html_select(['name' => '_birthdays_alarm_type', 'id' => $field_id] + $input_attrib);
             $select_type->add($this->gettext('none'), '');
 
             foreach ($this->driver->alarm_types as $type) {
                 $select_type->add($this->rc->gettext(strtolower("alarm{$type}option"), 'libcalendaring'), $type);
             }
 
             $input_value   = new html_inputfield(['name' => '_birthdays_alarm_value', 'id' => $field_id . 'value', 'size' => 3] + $input_attrib);
             $select_offset = new html_select(['name' => '_birthdays_alarm_offset', 'id' => $field_id . 'offset'] + $input_attrib);
 
             foreach (['-M','-H','-D'] as $trigger) {
                 $select_offset->add($this->rc->gettext('trigger' . $trigger, 'libcalendaring'), $trigger);
             }
 
             $preset      = libcalendaring::parse_alarm_value($this->rc->config->get('calendar_birthdays_alarm_offset', '-1D'));
             $preset_type = $this->rc->config->get('calendar_birthdays_alarm_type', '');
 
             $p['blocks']['birthdays']['options']['birthdays_alarmoffset'] = [
                 'title'   => html::label($field_id, rcube::Q($this->gettext('showalarms'))),
                 'content' => html::div('input-group',
                     $select_type->show($preset_type)
                     . $input_value->show($preset[0]) . ' ' . $select_offset->show($preset[1])
                 ),
             ];
         }
 
         return $p;
     }
 
     /**
      * Handler for preferences_save hook.
      * Executed on Calendar settings form submit.
      *
      * @param array Original parameters
      *
      * @return array Modified parameters
      */
     function preferences_save($p)
     {
         if ($p['section'] == 'calendar') {
             $this->load_driver();
 
             // compose default alarm preset value
             $alarm_offset  = rcube_utils::get_input_value('_alarm_offset', rcube_utils::INPUT_POST);
             $alarm_value   = rcube_utils::get_input_value('_alarm_value', rcube_utils::INPUT_POST);
             $default_alarm = $alarm_offset[0] . intval($alarm_value) . $alarm_offset[1];
 
             $birthdays_alarm_offset = rcube_utils::get_input_value('_birthdays_alarm_offset', rcube_utils::INPUT_POST);
             $birthdays_alarm_value  = rcube_utils::get_input_value('_birthdays_alarm_value', rcube_utils::INPUT_POST);
             $birthdays_alarm_value  = $birthdays_alarm_offset[0] . intval($birthdays_alarm_value) . $birthdays_alarm_offset[1];
 
             $p['prefs'] = [
                 'calendar_default_view' => rcube_utils::get_input_value('_default_view', rcube_utils::INPUT_POST),
                 'calendar_timeslots'    => intval(rcube_utils::get_input_value('_timeslots', rcube_utils::INPUT_POST)),
                 'calendar_first_day'    => intval(rcube_utils::get_input_value('_first_day', rcube_utils::INPUT_POST)),
                 'calendar_first_hour'   => intval(rcube_utils::get_input_value('_first_hour', rcube_utils::INPUT_POST)),
                 'calendar_work_start'   => intval(rcube_utils::get_input_value('_work_start', rcube_utils::INPUT_POST)),
                 'calendar_work_end'     => intval(rcube_utils::get_input_value('_work_end', rcube_utils::INPUT_POST)),
                 'calendar_show_weekno'  => intval(rcube_utils::get_input_value('_show_weekno', rcube_utils::INPUT_POST)),
                 'calendar_event_coloring'       => intval(rcube_utils::get_input_value('_event_coloring', rcube_utils::INPUT_POST)),
                 'calendar_default_alarm_type'   => rcube_utils::get_input_value('_alarm_type', rcube_utils::INPUT_POST),
                 'calendar_default_alarm_offset' => $default_alarm,
                 'calendar_default_calendar'     => rcube_utils::get_input_value('_default_calendar', rcube_utils::INPUT_POST),
                 'calendar_date_format'          => null,  // clear previously saved values
                 'calendar_time_format'          => null,
                 'calendar_contact_birthdays'      => (bool) rcube_utils::get_input_value('_contact_birthdays', rcube_utils::INPUT_POST),
                 'calendar_birthday_adressbooks'   => (array) rcube_utils::get_input_value('_birthday_adressbooks', rcube_utils::INPUT_POST),
                 'calendar_birthdays_alarm_type'   => rcube_utils::get_input_value('_birthdays_alarm_type', rcube_utils::INPUT_POST),
                 'calendar_birthdays_alarm_offset' => $birthdays_alarm_value ?: null,
                 'calendar_itip_after_action'      => intval(rcube_utils::get_input_value('_after_action', rcube_utils::INPUT_POST)),
             ];
 
             if ($p['prefs']['calendar_itip_after_action'] == 4) {
                 $p['prefs']['calendar_itip_after_action'] = rcube_utils::get_input_value('_after_action_folder', rcube_utils::INPUT_POST, true);
             }
 
             // categories
             if (empty($this->driver->nocategories)) {
                 $old_categories = $new_categories = [];
 
                 foreach ($this->driver->list_categories() as $name => $color) {
                     $old_categories[md5($name)] = $name;
                 }
 
                 $categories = (array) rcube_utils::get_input_value('_categories', rcube_utils::INPUT_POST);
                 $colors     = (array) rcube_utils::get_input_value('_colors', rcube_utils::INPUT_POST);
 
                 foreach ($categories as $key => $name) {
                     if (!isset($colors[$key])) {
                         continue;
                     }
 
                     $color = preg_replace('/^#/', '', strval($colors[$key]));
 
                     // rename categories in existing events -> driver's job
                     if (!empty($old_categories[$key])) {
                         $oldname = $old_categories[$key];
                         $this->driver->replace_category($oldname, $name, $color);
                         unset($old_categories[$key]);
                     }
                     else {
                         $this->driver->add_category($name, $color);
                     }
 
                     $new_categories[$name] = $color;
                 }
 
                 // these old categories have been removed, alter events accordingly -> driver's job
                 foreach ((array) $old_categories as $key => $name) {
                     $this->driver->remove_category($name);
                 }
 
                 $p['prefs']['calendar_categories'] = $new_categories;
             }
         }
 
         return $p;
     }
 
     /**
      * Dispatcher for calendar actions initiated by the client
      */
     function calendar_action()
     {
         $action  = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $cal     = rcube_utils::get_input_value('c', rcube_utils::INPUT_GPC);
         $success = false;
         $reload  = false;
 
         if (isset($cal['showalarms'])) {
             $cal['showalarms'] = intval($cal['showalarms']);
         }
 
         switch ($action) {
         case "form-new":
         case "form-edit":
             echo $this->ui->calendar_editform($action, $cal);
             exit;
 
         case "new":
             $success = $this->driver->create_calendar($cal);
             $reload  = true;
             break;
 
         case "edit":
             $success = $this->driver->edit_calendar($cal);
             $reload  = true;
             break;
 
         case "delete":
             if ($success = $this->driver->delete_calendar($cal)) {
                 $this->rc->output->command('plugin.destroy_source', ['id' => $cal['id']]);
             }
             break;
 
         case "subscribe":
             if (!$this->driver->subscribe_calendar($cal)) {
                 $this->rc->output->show_message($this->gettext('errorsaving'), 'error');
             }
             else {
                 $calendars = $this->driver->list_calendars();
                 $calendar  = !empty($calendars[$cal['id']]) ? $calendars[$cal['id']] : null;
 
                 // find parent folder and check if it's a "user calendar"
                 // if it's also activated we need to refresh it (#5340)
                 while (!empty($calendar['parent'])) {
                     if (isset($calendars[$calendar['parent']])) {
                         $calendar = $calendars[$calendar['parent']];
                     }
                     else {
                         break;
                     }
                 }
 
                 if ($calendar && $calendar['id'] != $cal['id']
                     && !empty($calendar['active'])
                     && $calendar['group'] == "other user"
                 ) {
                     $this->rc->output->command('plugin.refresh_source', $calendar['id']);
                 }
             }
             return;
 
         case "search":
             $results    = [];
             $color_mode = $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
             $query      = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
             $source     = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
 
             foreach ((array) $this->driver->search_calendars($query, $source) as $id => $prop) {
                 $editname = $prop['editname'];
                 unset($prop['editname']);  // force full name to be displayed
                 $prop['active'] = false;
 
                 // let the UI generate HTML and CSS representation for this calendar
                 $html = $this->ui->calendar_list_item($id, $prop, $jsenv);
                 $cal  = $jsenv[$id];
                 $cal['editname'] = $editname;
                 $cal['html']     = $html;
 
                 if (!empty($prop['color'])) {
                     $cal['css'] = $this->ui->calendar_css_classes($id, $prop, $color_mode);
                 }
 
                 $results[] = $cal;
             }
 
             // report more results available
             if (!empty($this->driver->search_more_results)) {
                 $this->rc->output->show_message('autocompletemore', 'notice');
             }
 
             $reqid = rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC);
             $this->rc->output->command('multi_thread_http_response', $results, $reqid);
             return;
         }
 
         if ($success) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $error_msg = $this->gettext('errorsaving');
             if (!empty($this->driver->last_error)) {
                 $error_msg .= ': ' . $this->driver->last_error;
             }
             $this->rc->output->show_message($error_msg, 'error');
         }
 
         $this->rc->output->command('plugin.unlock_saving');
 
         if ($success && $reload) {
             $this->rc->output->command('plugin.reload_view');
         }
     }
 
     /**
      * Dispatcher for event actions initiated by the client
      */
     function event_action()
     {
         $action  = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $event   = rcube_utils::get_input_value('e', rcube_utils::INPUT_POST, true);
         $success = $reload = $got_msg = false;
         $old     = null;
 
         // read old event data in order to find changes
         if ((!empty($event['_notify']) || !empty($event['_decline'])) && $action != 'new') {
             $old = $this->driver->get_event($event);
 
             // load main event if savemode is 'all' or if deleting 'future' events
             if (!empty($old['recurrence_id'])
                 && !empty($event['_savemode'])
                 && ($event['_savemode'] == 'all' || ($event['_savemode'] == 'future' && $action == 'remove' && empty($event['_decline'])))
             ) {
                 $old['id'] = $old['recurrence_id'];
                 $old = $this->driver->get_event($old);
             }
         }
 
         switch ($action) {
         case "new":
             // create UID for new event
             $event['uid'] = $this->generate_uid();
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->new_event($event)) {
                 $event['id']        = $event['uid'];
                 $event['_savemode'] = 'all';
 
                 $this->cleanup_event($event);
                 $this->event_save_success($event, null, $action, true);
                 $this->talk_room_update($event);
             }
 
             $reload = $success && !empty($event['recurrence']) ? 2 : 1;
             break;
 
         case "edit":
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->edit_event($event)) {
                 $this->cleanup_event($event);
                 $this->event_save_success($event, $old, $action, $success);
                 $this->talk_room_update($event);
             }
 
             $reload = $success && (!empty($event['recurrence']) || !empty($event['_savemode']) || !empty($event['_fromcalendar'])) ? 2 : 1;
             break;
 
         case "resize":
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->resize_event($event)) {
                 $this->event_save_success($event, $old, $action, $success);
             }
 
             $reload = !empty($event['_savemode']) ? 2 : 1;
             break;
 
         case "move":
             if (!$this->write_preprocess($event, $action)) {
                 $got_msg = true;
             }
             else if ($success = $this->driver->move_event($event)) {
                 $this->event_save_success($event, $old, $action, $success);
             }
 
             $reload = $success && !empty($event['_savemode']) ? 2 : 1;
             break;
 
         case "remove":
             // remove previous deletes
             $undo_time = $this->driver->undelete ? $this->rc->config->get('undo_timeout', 0) : 0;
 
             // search for event if only UID is given
             if (!isset($event['calendar']) && !empty($event['uid'])) {
                 if (!($event = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE))) {
                     break;
                 }
                 $undo_time = 0;
             }
 
             // Note: the driver is responsible for setting $_SESSION['calendar_event_undo']
             //       containing 'ts' and 'data' elements
             $success = $this->driver->remove_event($event, $undo_time < 1);
             $reload = (!$success || !empty($event['_savemode'])) ? 2 : 1;
 
             if ($undo_time > 0 && $success) {
                 // display message with Undo link.
                 $onclick = sprintf("%s.http_request('event', 'action=undo', %s.display_message('', 'loading'))",
                     rcmail_output::JS_OBJECT_NAME,
                     rcmail_output::JS_OBJECT_NAME
                 );
                 $msg = html::span(null, $this->gettext('successremoval'))
                     . ' ' . html::a(['onclick' => $onclick], $this->gettext('undo'));
 
                 $this->rc->output->show_message($msg, 'confirmation', null, true, $undo_time);
                 $got_msg = true;
             }
             else if ($success) {
                 $this->rc->output->show_message('calendar.successremoval', 'confirmation');
                 $got_msg = true;
             }
 
             // send cancellation for the main event
             if (isset($event['_savemode']) && $event['_savemode'] == 'all') {
                 unset($old['_instance'], $old['recurrence_date'], $old['recurrence_id']);
             }
             // send an update for the main event's recurrence rule instead of a cancellation message
             else if (isset($event['_savemode']) && $event['_savemode'] == 'future' && !is_bool($success)) {
                 $event['_savemode'] = 'all';  // force event_save_success() to load master event
                 $action  = 'edit';
                 $success = true;
             }
 
             // send iTIP reply that participant has declined the event
             if ($success && !empty($event['_decline'])) {
                 $emails    = $this->get_user_emails();
                 $organizer = null;
 
                 foreach ($old['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                         $old['attendees'][$i]['status'] = 'DECLINED';
                         $reply_sender = $attendee['email'];
                     }
                 }
 
                 if ($event['_savemode'] == 'future' && $event['id'] != $old['id']) {
                     $old['thisandfuture'] = true;
                 }
 
                 $itip = $this->load_itip();
                 $itip->set_sender_email($reply_sender);
 
                 if ($organizer && $itip->send_itip_message($old, 'REPLY', $organizer, 'itipsubjectdeclined', 'itipmailbodydeclined')) {
                     $mailto = !empty($organizer['name']) ? $organizer['name'] : $organizer['email'];
                     $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
 
                     $this->rc->output->command('display_message', $msg, 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
             }
             else if ($success) {
                 $this->event_save_success($event, $old, $action, $success);
             }
 
             break;
 
         case "undo":
             // Restore deleted event
             if (!empty($_SESSION['calendar_event_undo']['data'])) {
                 $event   = $_SESSION['calendar_event_undo']['data'];
                 $success = $this->driver->restore_event($event);
             }
 
             if ($success) {
                 $this->rc->session->remove('calendar_event_undo');
                 $this->rc->output->show_message('calendar.successrestore', 'confirmation');
                 $got_msg = true;
                 $reload  = 2;
             }
 
             break;
 
         case "rsvp":
             $itip_sending  = $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
             $status        = rcube_utils::get_input_value('status', rcube_utils::INPUT_POST);
             $attendees     = rcube_utils::get_input_value('attendees', rcube_utils::INPUT_POST);
             $reply_comment = $event['comment'];
 
             $this->write_preprocess($event, 'edit');
             $ev = $this->driver->get_event($event);
             $ev['attendees'] = $event['attendees'];
             $ev['free_busy'] = $event['free_busy'];
             $ev['_savemode'] = $event['_savemode'];
             $ev['comment']   = $reply_comment;
 
             // send invitation to delegatee + add it as attendee
             if ($status == 'delegated' && !empty($event['to'])) {
                 $itip = $this->load_itip();
                 if ($itip->delegate_to($ev, $event['to'], !empty($event['rsvp']), $attendees)) {
                     $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
                     $noreply = false;
                 }
             }
 
             $event = $ev;
 
             // compose a list of attendees affected by this change
             $updated_attendees = array_filter(array_map(function($j) use ($event) {
                     return $event['attendees'][$j];
                 },
                 $attendees
             ));
 
             if ($success = $this->driver->edit_rsvp($event, $status, $updated_attendees)) {
                 $noreply = rcube_utils::get_input_value('noreply', rcube_utils::INPUT_GPC);
                 $noreply = intval($noreply) || $status == 'needs-action' || $itip_sending === 0;
                 $reload  = $event['calendar'] != $ev['calendar'] || !empty($event['recurrence']) ? 2 : 1;
                 $emails  = $this->get_user_emails();
                 $ownedResourceEmails = $this->owned_resources_emails();
                 $organizer = null;
                 $resourceConfirmation = false;
 
                 foreach ($event['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array_nocase($attendee['email'], $emails)) {
                         $reply_sender = $attendee['email'];
                     }
                     else if (!empty($attendee['cutype']) && $attendee['cutype'] == 'RESOURCE' && !empty($attendee['email']) && in_array_nocase($attendee['email'], $ownedResourceEmails)) {
                         $resourceConfirmation = true;
                         // Note on behalf of which resource this update is going to be sent out
                         $event['_resource'] = $attendee['email'];
                     }
                 }
 
                 if (!$noreply) {
                     $itip = $this->load_itip();
                     $itip->set_sender_email($reply_sender);
                     $event['thisandfuture'] = $event['_savemode'] == 'future';
                     $bodytextprefix = $resourceConfirmation ? 'itipmailbodyresource' : 'itipmailbody';
 
                     if ($organizer && $itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, $bodytextprefix . $status)) {
                         $mailto = !empty($organizer['name']) ? $organizer['name'] : $organizer['email'];
                         $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
 
                         $this->rc->output->command('display_message', $msg, 'confirmation');
                     }
                     else {
                         $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                     }
                 }
 
                 // refresh all calendars
                 if ($event['calendar'] != $ev['calendar']) {
                     $this->rc->output->command('plugin.refresh_calendar', ['source' => null, 'refetch' => true]);
                     $reload = 0;
                 }
             }
 
             break;
 
         case "dismiss":
             $event['ids'] = explode(',', $event['id']);
             $plugin  = $this->rc->plugins->exec_hook('dismiss_alarms', $event);
             $success = $plugin['success'];
 
             foreach ($event['ids'] as $id) {
                 if (strpos($id, 'cal:') === 0) {
                     $success |= $this->driver->dismiss_alarm(substr($id, 4), $event['snooze']);
                 }
             }
 
             break;
 
         case "changelog":
             $data = $this->driver->get_event_changelog($event);
             if (is_array($data) && !empty($data)) {
                 $lib = $this->lib;
                 $dtformat = $this->rc->config->get('date_format') . ' ' . $this->rc->config->get('time_format');
                 array_walk($data, function(&$change) use ($lib, $dtformat) {
                     if (!empty($change['date'])) {
                         $dt = $lib->adjust_timezone($change['date']);
 
                         if ($dt instanceof DateTimeInterface) {
                             $change['date'] = $this->rc->format_date($dt, $dtformat, false);
                         }
                     }
                 });
 
                 $this->rc->output->command('plugin.render_event_changelog', $data);
             }
             else {
                 $this->rc->output->command('plugin.render_event_changelog', false);
             }
 
             $got_msg = true;
             $reload  = false;
 
             break;
 
         case "diff":
             $data = $this->driver->get_event_diff($event, $event['rev1'], $event['rev2']);
             if (is_array($data)) {
                 // convert some properties, similar to self::_client_event()
                 $lib = $this->lib;
                 array_walk($data['changes'], function(&$change, $i) use ($event, $lib) {
                     // convert date cols
                     foreach (['start', 'end', 'created', 'changed'] as $col) {
                         if ($change['property'] == $col) {
                             $change['old'] = $lib->adjust_timezone($change['old'], strlen($change['old']) == 10)->format('c');
                             $change['new'] = $lib->adjust_timezone($change['new'], strlen($change['new']) == 10)->format('c');
                         }
                     }
                     // create textual representation for alarms and recurrence
                     if ($change['property'] == 'alarms') {
                         if (is_array($change['old'])) {
                             $change['old_'] = libcalendaring::alarm_text($change['old']);
                         }
                         if (is_array($change['new'])) {
                             $change['new_'] = libcalendaring::alarm_text(array_merge((array)$change['old'], $change['new']));
                         }
                     }
                     if ($change['property'] == 'recurrence') {
                         if (is_array($change['old'])) {
                             $change['old_'] = $lib->recurrence_text($change['old']);
                         }
                         if (is_array($change['new'])) {
                             $change['new_'] = $lib->recurrence_text(array_merge((array)$change['old'], $change['new']));
                         }
                     }
                     if ($change['property'] == 'attachments') {
                         if (is_array($change['old'])) {
                             $change['old']['classname'] = rcube_utils::file2class($change['old']['mimetype'], $change['old']['name']);
                         }
                         if (is_array($change['new'])) {
                             $change['new']['classname'] = rcube_utils::file2class($change['new']['mimetype'], $change['new']['name']);
                         }
                     }
                     // compute a nice diff of description texts
                     if ($change['property'] == 'description') {
                         $change['diff_'] = libkolab::html_diff($change['old'], $change['new']);
                     }
                 });
 
                 $this->rc->output->command('plugin.event_show_diff', $data);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectdiffnotavailable'), 'error');
             }
 
             $got_msg = true;
             $reload  = false;
 
             break;
 
         case "show":
             if ($event = $this->driver->get_event_revison($event, $event['rev'])) {
                 $this->rc->output->command('plugin.event_show_revision', $this->_client_event($event));
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectnotfound'), 'error');
             }
 
             $got_msg = true;
             $reload  = false;
             break;
 
         case "restore":
             if ($success = $this->driver->restore_event_revision($event, $event['rev'])) {
                 $_event = $this->driver->get_event($event);
                 $reload = $_event['recurrence'] ? 2 : 1;
                 $msg = $this->gettext(['name' => 'objectrestoresuccess', 'vars' => ['rev' => $event['rev']]]);
                 $this->rc->output->command('display_message', $msg, 'confirmation');
                 $this->rc->output->command('plugin.close_history_dialog');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectrestoreerror'), 'error');
                 $reload = 0;
             }
 
             $got_msg = true;
             break;
         }
 
         // show confirmation/error message
         if (!$got_msg) {
             if ($success) {
                 $this->rc->output->show_message('successfullysaved', 'confirmation');
             }
             else {
                 $this->rc->output->show_message('calendar.errorsaving', 'error');
             }
         }
 
         // unlock client
         $this->rc->output->command('plugin.unlock_saving', $success);
 
         // update event object on the client or trigger a complete refresh if too complicated
         if ($reload && empty($_REQUEST['_framed'])) {
             $args = ['source' => $event['calendar']];
             if ($reload > 1) {
                 $args['refetch'] = true;
             }
             else if ($success && $action != 'remove') {
                 $args['update'] = $this->_client_event($this->driver->get_event($event), true);
             }
             $this->rc->output->command('plugin.refresh_calendar', $args);
         }
     }
 
     /**
      * Helper method sending iTip notifications after successful event updates
      */
     private function event_save_success(&$event, $old, $action, $success)
     {
         // $success is a new event ID
         if ($success !== true) {
             // send update notification on the main event
             if (!empty($event['_savemode']) && $event['_savemode'] == 'future' && !empty($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 (!empty($event['_savemode']) && ($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'] ?? null;
 
             // send notification for the main event when savemode is 'all'
             if ($action != 'remove' && $_savemode == 'all'
                 && (!empty($event['recurrence_id']) || !empty($old['recurrence_id']) || ($old && $old['id'] != $event['id']))
             ) {
                 if (!empty($event['recurrence_id'])) {
                     $event['id'] = $event['recurrence_id'];
                 }
                 else if (!empty($old['recurrence_id'])) {
                     $event['id'] = $old['recurrence_id'];
                 }
                 else {
                     $event['id'] = $old['id'];
                 }
                 $event = $this->driver->get_event($event, 0, true);
                 unset($event['_instance'], $event['recurrence_date']);
             }
             else {
                 // make sure we have the complete record
                 $event = $action == 'remove' ? $old : $this->driver->get_event($event, 0, true);
             }
 
             $event['_savemode'] = $_savemode;
 
             if ($old) {
                 $old['thisandfuture'] = $_savemode == 'future';
             }
 
             // only notify if data really changed (TODO: do diff check on client already)
             if (!$old || $action == 'remove' || self::event_diff($event, $old)) {
                 $comment = isset($event['_comment']) ? $event['_comment'] : null;
                 $sent    = $this->notify_attendees($event, $old, $action, $comment);
 
                 if ($sent > 0) {
                     $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
                 }
                 else if ($sent < 0) {
                     $this->rc->output->show_message('calendar.errornotifying', 'error');
                 }
             }
         }
     }
 
     /**
      * Handler for load-requests from fullcalendar
      * This will return pure JSON formatted output
      */
     function load_events()
     {
         $start  = $this->input_timestamp('start', rcube_utils::INPUT_GET);
         $end    = $this->input_timestamp('end', rcube_utils::INPUT_GET);
         $query  = rcube_utils::get_input_value('q', rcube_utils::INPUT_GET);
         $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
 
         $events = $this->driver->load_events($start, $end, $query, $source);
         echo $this->encode($events, !empty($query));
         exit;
     }
 
     /**
      * Handler for requests fetching event counts for calendars
      */
     public function count_events()
     {
         // don't update session on these requests (avoiding race conditions)
         $this->rc->session->nowrite = true;
 
         $start  = rcube_utils::get_input_value('start', rcube_utils::INPUT_GET);
         $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
         $end    = rcube_utils::get_input_value('end', rcube_utils::INPUT_GET);
 
         if (!$start) {
             $start = new DateTime('today 00:00:00', $this->timezone);
             $start = $start->format('U');
         }
 
         $counts = $this->driver->count_events($source, $start, $end);
 
         $this->rc->output->command('plugin.update_counts', ['counts' => $counts]);
     }
 
     /**
      * Load event data from an iTip message attachment
      */
     public function itip_events($msgref)
     {
         $path = explode('/', $msgref);
         $msg  = array_pop($path);
         $mbox = join('/', $path);
         list($uid, $mime_id) = explode('#', $msg);
         $events = [];
 
         if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
             $partstat = 'NEEDS-ACTION';
 
             $event['id']        = $event['uid'];
             $event['temporary'] = true;
             $event['readonly']  = true;
             $event['calendar']  = '--invitation--itip';
             $event['className'] = 'fc-invitation-' . strtolower($partstat);
             $event['_mbox']     = $mbox;
             $event['_uid']      = $uid;
             $event['_part']     = $mime_id;
 
             $events[] = $this->_client_event($event, true);
 
             // add recurring instances
             if (!empty($event['recurrence'])) {
                 // Some installations can't handle all occurrences (aborting the request w/o an error in log)
                 $freq = !empty($event['recurrence']['FREQ']) ? $event['recurrence']['FREQ'] : null;
                 $end  = clone $event['start'];
                 $end->add(new DateInterval($freq == 'DAILY' ? 'P1Y' : 'P10Y'));
 
                 foreach ($this->driver->get_recurring_events($event, $event['start'], $end) as $recurring) {
                     $recurring['temporary'] = true;
                     $recurring['readonly']  = true;
                     $recurring['calendar']  = '--invitation--itip';
 
                     $events[] = $this->_client_event($recurring, true);
                 }
             }
         }
 
         return $events;
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for updated data in active calendars and sync them to the client
      */
     public function refresh($attr)
     {
         // refresh the entire calendar every 10th time to also sync deleted events
         if (rand(0, 10) == 10) {
             $this->rc->output->command('plugin.refresh_calendar', ['refetch' => true]);
             return;
         }
 
         $counts = [];
 
         foreach ($this->driver->list_calendars(calendar_driver::FILTER_ACTIVE) as $cal) {
             $events = $this->driver->load_events(
                 rcube_utils::get_input_value('start', rcube_utils::INPUT_GPC),
                 rcube_utils::get_input_value('end', rcube_utils::INPUT_GPC),
                 rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC),
                 $cal['id'],
                 1,
                 $attr['last']
             );
 
             foreach ($events as $event) {
                 $this->rc->output->command(
                     'plugin.refresh_calendar',
                     ['source' => $cal['id'], 'update' => $this->_client_event($event)]
                 );
             }
 
             // refresh count for this calendar
             if (!empty($cal['counts'])) {
                 $today = new DateTime('today 00:00:00', $this->timezone);
                 $counts += $this->driver->count_events($cal['id'], $today->format('U'));
             }
         }
 
         if (!empty($counts)) {
             $this->rc->output->command('plugin.update_counts', ['counts' => $counts]);
         }
     }
 
     /**
      * Handler for pending_alarms plugin hook triggered by the calendar module on keep-alive requests.
      * This will check for pending notifications and pass them to the client
      */
     public function pending_alarms($p)
     {
         $this->load_driver();
 
         $time = !empty($p['time']) ? $p['time'] : time();
 
         if ($alarms = $this->driver->pending_alarms($time)) {
             foreach ($alarms as $alarm) {
                 $alarm['id'] = 'cal:' . $alarm['id'];  // prefix ID with cal:
                 $p['alarms'][] = $alarm;
             }
         }
 
         // get alarms for birthdays calendar
         if (
             $this->rc->config->get('calendar_contact_birthdays')
             && $this->rc->config->get('calendar_birthdays_alarm_type') == 'DISPLAY'
         ) {
             $cache = $this->rc->get_cache('calendar.birthdayalarms', 'db');
 
             foreach ($this->driver->load_birthday_events($time, $time + 86400 * 60) as $e) {
                 $alarm = libcalendaring::get_next_alarm($e);
 
                 // overwrite alarm time with snooze value (or null if dismissed)
                 if ($dismissed = $cache->get($e['id'])) {
                     $alarm['time'] = $dismissed['notifyat'];
                 }
 
                 // add to list if alarm is set
                 if ($alarm && !empty($alarm['time']) && $alarm['time'] <= $time) {
                     $e['id']       = 'cal:bday:' . $e['id'];
                     $e['notifyat'] = $alarm['time'];
                     $p['alarms'][] = $e;
                 }
             }
         }
 
         return $p;
     }
 
     /**
      * Handler for alarm dismiss hook triggered by libcalendaring
      */
     public function dismiss_alarms($p)
     {
         $this->load_driver();
 
         foreach ((array) $p['ids'] as $id) {
             if (strpos($id, 'cal:bday:') === 0) {
                 $p['success'] |= $this->driver->dismiss_birthday_alarm(substr($id, 9), $p['snooze']);
             }
             else if (strpos($id, 'cal:') === 0) {
                 $p['success'] |= $this->driver->dismiss_alarm(substr($id, 4), $p['snooze']);
             }
         }
 
         return $p;
     }
 
     /**
      * Handler for check-recent requests which are accidentally sent to calendar
      */
     function check_recent()
     {
         // NOP
         $this->rc->output->send();
     }
 
     /**
      * Hook triggered when a contact is saved
      */
     function contact_update($p)
     {
         // clear birthdays calendar cache
         if (!empty($p['record']['birthday'])) {
             $cache = $this->rc->get_cache('calendar.birthdays', 'db');
             $cache->remove();
         }
     }
 
     /**
      *
      */
     function import_events()
     {
         // Upload progress update
         if (!empty($_GET['_progress'])) {
             $this->rc->upload_progress();
         }
 
         @set_time_limit(0);
 
         // process uploaded file if there is no error
         $err = $_FILES['_data']['error'];
 
         if (!$err && !empty($_FILES['_data']['tmp_name'])) {
             $calendar   = rcube_utils::get_input_value('calendar', rcube_utils::INPUT_GPC);
             $rangestart = !empty($_REQUEST['_range']) ? date_create("now -" . intval($_REQUEST['_range']) . " months") : 0;
 
             // extract zip file
             if ($_FILES['_data']['type'] == 'application/zip') {
                 $count = 0;
                 if (class_exists('ZipArchive', false)) {
                     $zip = new ZipArchive();
                     if ($zip->open($_FILES['_data']['tmp_name'])) {
                         $randname = uniqid('zip-' . session_id(), true);
                         $tmpdir = slashify($this->rc->config->get('temp_dir', sys_get_temp_dir())) . $randname;
                         mkdir($tmpdir, 0700);
 
                         // extract each ical file from the archive and import it
                         for ($i = 0; $i < $zip->numFiles; $i++) {
                             $filename = $zip->getNameIndex($i);
                             if (preg_match('/\.ics$/i', $filename)) {
                                 $tmpfile = $tmpdir . '/' . basename($filename);
                                 if (copy('zip://' . $_FILES['_data']['tmp_name'] . '#'.$filename, $tmpfile)) {
                                     $count += $this->import_from_file($tmpfile, $calendar, $rangestart, $errors);
                                     unlink($tmpfile);
                                 }
                             }
                         }
 
                         rmdir($tmpdir);
                         $zip->close();
                     }
                     else {
                         $errors = 1;
                         $msg = 'Failed to open zip file.';
                     }
                 }
                 else {
                     $errors = 1;
                     $msg = 'Zip files are not supported for import.';
                 }
             }
             else {
                 // attempt to import teh uploaded file directly
                 $count = $this->import_from_file($_FILES['_data']['tmp_name'], $calendar, $rangestart, $errors);
             }
 
             if ($count) {
                 $this->rc->output->command('display_message', $this->gettext(['name' => 'importsuccess', 'vars' => ['nr' => $count]]), 'confirmation');
                 $this->rc->output->command('plugin.import_success', ['source' => $calendar, 'refetch' => true]);
             }
             else if (!$errors) {
                 $this->rc->output->command('display_message', $this->gettext('importnone'), 'notice');
                 $this->rc->output->command('plugin.import_success', ['source' => $calendar]);
             }
             else {
                 $this->rc->output->command('plugin.import_error', ['message' => $this->gettext('importerror') . ($msg ? ': ' . $msg : '')]);
             }
         }
         else {
             if ($err == UPLOAD_ERR_INI_SIZE || $err == UPLOAD_ERR_FORM_SIZE) {
                 $max = $this->rc->show_bytes(parse_bytes(ini_get('upload_max_filesize')));
                 $msg = $this->rc->gettext(['name' => 'filesizeerror', 'vars' => ['size' => $max]]);
             }
             else {
                 $msg = $this->rc->gettext('fileuploaderror');
             }
 
             $this->rc->output->command('plugin.import_error', ['message' => $msg]);
         }
 
         $this->rc->output->send('iframe');
     }
 
     /**
      * Helper function to parse and import a single .ics file
      */
     private function import_from_file($filepath, $calendar, $rangestart, &$errors)
     {
         $user_email = $this->rc->user->get_username();
         $ical       = $this->get_ical();
         $errors     = !$ical->fopen($filepath);
 
         $count = $i = 0;
 
         foreach ($ical as $event) {
             // keep the browser connection alive on long import jobs
             if (++$i > 100 && $i % 100 == 0) {
                 echo "<!-- -->";
                 ob_flush();
             }
 
             // TODO: correctly handle recurring events which start before $rangestart
             if ($rangestart && $event['end'] < $rangestart
                 && (empty($event['recurrence']) || (!empty($event['recurrence']['until']) && $event['recurrence']['until'] < $rangestart))
             ) {
                 continue;
             }
 
             $event['_owner']   = $user_email;
             $event['calendar'] = $calendar;
 
             if ($this->driver->new_event($event)) {
                 $count++;
             }
             else {
                 $errors++;
             }
         }
 
         return $count;
     }
 
     /**
      * Construct the ics file for exporting events to iCalendar format;
      */
     function export_events($terminate = true)
     {
         $start       = rcube_utils::get_input_value('start', rcube_utils::INPUT_GET);
         $end         = rcube_utils::get_input_value('end', rcube_utils::INPUT_GET);
         $event_id    = rcube_utils::get_input_value('id', rcube_utils::INPUT_GET);
         $attachments = rcube_utils::get_input_value('attachments', rcube_utils::INPUT_GET);
         $calid       = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
 
         if (!isset($start)) {
             $start = 'today -1 year';
         }
         if (!is_numeric($start)) {
             $start = strtotime($start . ' 00:00:00');
         }
         if (!$end) {
             $end = 'today +10 years';
         }
         if (!is_numeric($end)) {
             $end = strtotime($end . ' 23:59:59');
         }
 
         $filename  = $calid;
         $calendars = $this->driver->list_calendars();
         $events    = [];
 
         if (!empty($calendars[$calid])) {
             $filename = !empty($calendars[$calid]['name']) ? $calendars[$calid]['name'] : $calid;
             $filename = asciiwords(html_entity_decode($filename));  // to 7bit ascii
 
             if (!empty($event_id)) {
                 if ($event = $this->driver->get_event(['calendar' => $calid, 'id' => $event_id], 0, true)) {
                     if (!empty($event['recurrence_id'])) {
                         $event = $this->driver->get_event(['calendar' => $calid, 'id' => $event['recurrence_id']], 0, true);
                     }
 
                     $events   = [$event];
                     $filename = asciiwords($event['title']);
 
                     if (empty($filename)) {
                         $filename = 'event';
                     }
                 }
             }
             else {
                 $events = $this->driver->load_events($start, $end, null, $calid, 0);
                 if (empty($filename)) {
                     $filename = $calid;
                 }
             }
         }
 
         header("Content-Type: text/calendar");
         header("Content-Disposition: inline; filename=".$filename.'.ics');
 
         $this->get_ical()->export($events, '', true, $attachments ? [$this->driver, 'get_attachment_body'] : null);
 
         if ($terminate) {
             exit;
         }
     }
 
     /**
      * Handler for iCal feed requests
      */
     function ical_feed_export()
     {
         $session_exists = !empty($_SESSION['user_id']);
 
         // process HTTP auth info
         if (!empty($_SERVER['PHP_AUTH_USER']) && isset($_SERVER['PHP_AUTH_PW'])) {
             $_POST['_user'] = $_SERVER['PHP_AUTH_USER']; // used for rcmail::autoselect_host()
             $auth = $this->rc->plugins->exec_hook('authenticate', [
                 'host' => $this->rc->autoselect_host(),
                 'user' => trim($_SERVER['PHP_AUTH_USER']),
                 'pass' => $_SERVER['PHP_AUTH_PW'],
                 'cookiecheck' => true,
                 'valid'       => true,
             ]);
 
             if ($auth['valid'] && !$auth['abort']) {
                 $this->rc->login($auth['user'], $auth['pass'], $auth['host']);
             }
         }
 
         // require HTTP auth
         if (empty($_SESSION['user_id'])) {
             header('WWW-Authenticate: Basic realm="Kolab Calendar"');
             header('HTTP/1.0 401 Unauthorized');
             exit;
         }
 
         // decode calendar feed hash
         $format  = 'ics';
         $calhash = rcube_utils::get_input_value('_cal', rcube_utils::INPUT_GET);
 
         if (preg_match(($suff_regex = '/\.([a-z0-9]{3,5})$/i'), $calhash, $m)) {
             $format  = strtolower($m[1]);
             $calhash = preg_replace($suff_regex, '', $calhash);
         }
 
         if (!strpos($calhash, ':')) {
             $calhash = base64_decode($calhash);
         }
 
         list($user, $_GET['source']) = explode(':', $calhash, 2);
 
         // sanity check user
         if ($this->rc->user->get_username() == $user) {
             $this->setup();
             $this->load_driver();
             $this->export_events(false);
         }
         else {
             header('HTTP/1.0 404 Not Found');
         }
 
         // don't save session data
         if (!$session_exists) {
             session_destroy();
         }
 
         exit;
     }
 
     /**
      *
      */
     function load_settings()
     {
         $this->lib->load_settings();
         $this->defaults += $this->lib->defaults;
 
         $settings = [];
 
         // configuration
         $settings['default_view']     = (string) $this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view']);
         $settings['timeslots']        = (int) $this->rc->config->get('calendar_timeslots', $this->defaults['calendar_timeslots']);
         $settings['first_day']        = (int) $this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
         $settings['first_hour']       = (int) $this->rc->config->get('calendar_first_hour', $this->defaults['calendar_first_hour']);
         $settings['work_start']       = (int) $this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']);
         $settings['work_end']         = (int) $this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']);
         $settings['agenda_range']     = (int) $this->rc->config->get('calendar_agenda_range', $this->defaults['calendar_agenda_range']);
         $settings['event_coloring']   = (int) $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
         $settings['time_indicator']   = (int) $this->rc->config->get('calendar_time_indicator', $this->defaults['calendar_time_indicator']);
         $settings['invite_shared']    = (int) $this->rc->config->get('calendar_allow_invite_shared', $this->defaults['calendar_allow_invite_shared']);
         $settings['itip_notify']      = (int) $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
         $settings['show_weekno']      = (int) $this->rc->config->get('calendar_show_weekno', $this->defaults['calendar_show_weekno']);
         $settings['default_calendar'] = $this->rc->config->get('calendar_default_calendar');
         $settings['invitation_calendars'] = (bool) $this->rc->config->get('kolab_invitation_calendars', false);
 
         // 'table' view has been replaced by 'list' view
         if ($settings['default_view'] == 'table') {
             $settings['default_view'] = 'list';
         }
 
         // get user identity to create default attendee
         if ($this->ui->screen == 'calendar') {
             foreach ($this->rc->user->list_emails() as $rec) {
                 if (empty($identity)) {
                     $identity = $rec;
                 }
 
                 $identity['emails'][] = $rec['email'];
                 $settings['identities'][$rec['identity_id']] = $rec['email'];
             }
 
             $identity['emails'][] = $this->rc->user->get_username();
             $identity['ownedResources'] = $this->owned_resources_emails();
             $settings['identity'] = [
                 'name'   => $identity['name'],
                 'email'  => strtolower($identity['email']),
                 'emails' => ';' . strtolower(join(';', $identity['emails'])),
                 'ownedResources' => ';' . strtolower(join(';', $identity['ownedResources']))
             ];
         }
 
         // freebusy token authentication URL
         if (($url = $this->rc->config->get('calendar_freebusy_session_auth_url'))
             && ($uniqueid = $this->rc->config->get('kolab_uniqueid'))
         ) {
             if ($url === true) {
                 $url = '/freebusy';
             }
             $url = rtrim(rcube_utils::resolve_url($url), '/ ');
             $url .= '/' . urlencode($this->rc->get_user_name());
             $url .= '/' . urlencode($uniqueid);
 
             $settings['freebusy_url'] = $url;
         }
 
         return $settings;
     }
 
     /**
      * Encode events as JSON
      *
      * @param array Events as array
      * @param bool  Add CSS class names according to calendar and categories
      *
      * @return string JSON encoded events
      */
     function encode($events, $addcss = false)
     {
         $json = [];
         foreach ($events as $event) {
             $json[] = $this->_client_event($event, $addcss);
         }
         return rcube_output::json_serialize($json);
     }
 
     /**
      * Convert an event object to be used on the client
      */
     private function _client_event($event, $addcss = false)
     {
         // compose a human readable strings for alarms_text and recurrence_text
         if (!empty($event['valarms'])) {
             $event['alarms_text'] = libcalendaring::alarms_text($event['valarms']);
             $event['valarms'] = libcalendaring::to_client_alarms($event['valarms']);
         }
 
         if (!empty($event['recurrence'])) {
             $event['recurrence_text'] = $this->lib->recurrence_text($event['recurrence']);
             $event['recurrence'] = $this->lib->to_client_recurrence($event['recurrence'], $event['allday']);
             unset($event['recurrence_date']);
         }
 
         if (!empty($event['attachments'])) {
             foreach ($event['attachments'] as $k => $attachment) {
                 $event['attachments'][$k]['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
                 unset($event['attachments'][$k]['data'], $event['attachments'][$k]['content']);
 
                 if (empty($attachment['id'])) {
                     $event['attachments'][$k]['id'] = $k;
                 }
             }
         }
 
         // convert link URIs references into structs
         if (array_key_exists('links', $event)) {
             foreach ((array) $event['links'] as $i => $link) {
                 if (strpos($link, 'imap://') === 0 && ($msgref = $this->driver->get_message_reference($link))) {
                     $event['links'][$i] = $msgref;
                 }
             }
         }
 
         // check for organizer in attendees list
         $organizer = null;
         foreach ((array) $event['attendees'] as $i => $attendee) {
             if ($attendee['role'] == 'ORGANIZER') {
                 $organizer = $attendee;
             }
             if (!empty($attendee['status']) && $attendee['status'] == 'DELEGATED' && empty($attendee['rsvp'])) {
                 $event['attendees'][$i]['noreply'] = true;
             }
             else {
                 unset($event['attendees'][$i]['noreply']);
             }
         }
 
         if ($organizer === null && !empty($event['organizer'])) {
             $organizer = $event['organizer'];
             $organizer['role'] = 'ORGANIZER';
             if (!is_array($event['attendees'])) {
                 $event['attendees'] = [$organizer];
             }
         }
 
         // Convert HTML description into plain text
         if ($this->is_html($event)) {
             $h2t = new rcube_html2text($event['description'], false, true, 0);
             $event['description'] = trim($h2t->get_text());
         }
 
         // mapping url => vurl, allday => allDay because of the fullcalendar client script
         $event['vurl']   = $event['url'] ?? null;
         $event['allDay'] = !empty($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($event['title'] ?? null),
             'description' => strval($event['description'] ?? null),
             'location'    => strval($event['location'] ?? null),
         ] + $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($event)
     {
           // check for opening and closing <html> or <body> tags
         return !empty($event['description'])
             && 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']);
         }
 
         $eventid = 'cal-' . (!empty($event['id']) ? $event['id'] : 'new');
         $handler = new kolab_attachments_handler();
         $event['attachments'] = $handler->attachments_set(self::SESSION_KEY, $eventid, $event['attachments'] ?? []);
 
         // convert link references into simple URIs
         if (array_key_exists('links', $event)) {
             $event['links'] = array_map(function($link) {
                     return is_array($link) ? $link['uri'] : strval($link);
                 },
                 (array) $event['links']
             );
         }
 
         // check for organizer in attendees
         if ($action == 'new' || $action == 'edit') {
             if (empty($event['attendees'])) {
                 $event['attendees'] = [];
             }
 
             $emails = $this->get_user_emails();
             $organizer = $owner = false;
 
             foreach ((array) $event['attendees'] as $i => $attendee) {
                 if ($attendee['role'] == 'ORGANIZER') {
                     $organizer = $i;
                 }
                 if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                     $owner = $i;
                 }
                 if (!isset($attendee['rsvp'])) {
                     $event['attendees'][$i]['rsvp'] = true;
                 }
                 else if (is_string($attendee['rsvp'])) {
                     $event['attendees'][$i]['rsvp'] = $attendee['rsvp'] == 'true' || $attendee['rsvp'] == '1';
                 }
             }
 
             if (!empty($event['_identity'])) {
                 $identity = $this->rc->user->get_identity($event['_identity']);
             }
 
             // set new organizer identity
             if ($organizer !== false && !empty($identity)) {
                 $event['attendees'][$organizer]['name']  = $identity['name'];
                 $event['attendees'][$organizer]['email'] = $identity['email'];
             }
             // set owner as organizer if yet missing
             else if ($organizer === false && $owner !== false) {
                 $event['attendees'][$owner]['role'] = 'ORGANIZER';
                 unset($event['attendees'][$owner]['rsvp']);
             }
             // fallback to the selected identity
             else if ($organizer === false && !empty($identity)) {
                 $event['attendees'][] = [
                     'role'  => 'ORGANIZER',
                     'name'  => $identity['name'],
                     'email' => $identity['email'],
                 ];
             }
         }
 
         // mapping url => vurl because of the fullcalendar client script
         if (array_key_exists('vurl', $event)) {
             $event['url'] = $event['vurl'];
             unset($event['vurl']);
         }
 
         return true;
     }
 
     /**
      * Releases some resources after successful event save
      */
     private function cleanup_event(&$event)
     {
         $handler = new kolab_attachments_handler();
         $handler->attachments_cleanup(self::SESSION_KEY);
     }
 
     /**
      * Send out an invitation/notification to all event attendees
      */
     private function notify_attendees($event, $old, $action = 'edit', $comment = null, $rsvp = null)
     {
         $is_cancelled = $action == 'remove'
             || (!empty($event['status']) && $event['status'] == 'CANCELLED' && ($old['status'] ?? '') != $event['status']);
 
         $event['cancelled'] = $is_cancelled;
 
         if ($rsvp === null) {
             $rsvp = !$old || ($event['sequence'] ?? 0) > ($old['sequence'] ?? 0);
         }
 
         $itip        = $this->load_itip();
         $emails      = $this->get_user_emails();
         $itip_notify = (int) $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
         // add comment to the iTip attachment
         $event['comment'] = $comment;
 
         // set a valid recurrence-id if this is a recurrence instance
         libcalendaring::identify_recurrence_instance($event);
 
         // compose multipart message using PEAR:Mail_Mime
         $method  = $action == 'remove' ? 'CANCEL' : 'REQUEST';
         $message = $itip->compose_itip_message($event, $method, $rsvp);
 
         // list existing attendees from $old event
         $old_attendees = [];
         if (!empty($old['attendees'])) {
             foreach ((array) $old['attendees'] as $attendee) {
                 $old_attendees[] = $attendee['email'];
             }
         }
 
         // send to every attendee
         $sent    = 0;
         $current = [];
         foreach ((array) $event['attendees'] as $attendee) {
             // skip myself for obvious reasons
             if (empty($attendee['email']) || in_array(strtolower($attendee['email']), $emails)) {
                 continue;
             }
 
             $current[] = strtolower($attendee['email']);
 
             // skip if notification is disabled for this attendee
             if (!empty($attendee['noreply']) && $itip_notify & 2) {
                 continue;
             }
 
             // skip if this attendee has delegated and set RSVP=FALSE
             if ($attendee['status'] == 'DELEGATED' && $attendee['rsvp'] === false) {
                 continue;
             }
 
             // which template to use for mail text
             $is_new   = !in_array($attendee['email'], $old_attendees);
             $is_rsvp  = $is_new || $event['sequence'] > $old['sequence'];
             $bodytext = $is_cancelled ? 'eventcancelmailbody' : ($is_new ? 'invitationmailbody' : 'eventupdatemailbody');
             $subject  = $is_cancelled ? 'eventcancelsubject'  : ($is_new ? 'invitationsubject' : ($event['title'] ? 'eventupdatesubject' : 'eventupdatesubjectempty'));
 
             $event['comment'] = $comment;
 
             // finally send the message
             if ($itip->send_itip_message($event, $method, $attendee, $subject, $bodytext, $message, $is_rsvp)) {
                 $sent++;
             }
             else {
                 $sent = -100;
             }
         }
 
         // TODO: on change of a recurring (main) event, also send updates to differing attendess of recurrence exceptions
 
         // send CANCEL message to removed attendees
         if (!empty($old['attendees'])) {
             foreach ($old['attendees'] as $attendee) {
                 if ($attendee['role'] == 'ORGANIZER'
                     || empty($attendee['email'])
                     || in_array(strtolower($attendee['email']), $current)
                 ) {
                     continue;
                 }
 
                 $vevent = $old;
                 $vevent['cancelled'] = $is_cancelled;
                 $vevent['attendees'] = [$attendee];
                 $vevent['comment']   = $comment;
 
                 if ($itip->send_itip_message($vevent, 'CANCEL', $attendee, 'eventcancelsubject', 'eventcancelmailbody')) {
                     $sent++;
                 }
                 else {
                     $sent = -100;
                 }
             }
         }
 
         return $sent;
     }
 
     /**
      * Echo simple free/busy status text for the given user and time range
      */
     public function freebusy_status()
     {
         $email = rcube_utils::get_input_value('email', rcube_utils::INPUT_GPC);
         $start = $this->input_timestamp('start', rcube_utils::INPUT_GPC);
         $end   = $this->input_timestamp('end', rcube_utils::INPUT_GPC);
 
         if (!$start) $start = time();
         if (!$end) $end = $start + 3600;
 
         $status = 'UNKNOWN';
         $fbtypemap = [
             calendar::FREEBUSY_UNKNOWN   => 'UNKNOWN',
             calendar::FREEBUSY_FREE      => 'FREE',
             calendar::FREEBUSY_BUSY      => 'BUSY',
             calendar::FREEBUSY_TENTATIVE => 'TENTATIVE',
             calendar::FREEBUSY_OOF       => 'OUT-OF-OFFICE'
         ];
 
         // if the backend has free-busy information
         $fblist = $this->driver->get_freebusy_list($email, $start, $end);
 
         if (is_array($fblist)) {
             $status = 'FREE';
 
             foreach ($fblist as $slot) {
                 list($from, $to, $type) = $slot;
                 if ($from < $end && $to > $start) {
                     $status = isset($type) && !empty($fbtypemap[$type]) ? $fbtypemap[$type] : 'BUSY';
                     break;
                 }
             }
         }
 
         // let this information be cached for 5min
         $this->rc->output->future_expire_header(300);
 
         echo $status;
         exit;
     }
 
     /**
      * Return a list of free/busy time slots within the given period
      * Echo data in JSON encoding
      */
     public function freebusy_times()
     {
         $email = rcube_utils::get_input_value('email', rcube_utils::INPUT_GPC);
         $start = $this->input_timestamp('start', rcube_utils::INPUT_GPC);
         $end   = $this->input_timestamp('end', rcube_utils::INPUT_GPC);
         $interval  = intval(rcube_utils::get_input_value('interval', rcube_utils::INPUT_GPC));
         $strformat = $interval > 60 ? 'Ymd' : 'YmdHis';
 
         if (!$start) $start = time();
         if (!$end)   $end = $start + 86400 * 30;
         if (!$interval) $interval = 60;  // 1 hour
 
         $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;
         }
 
         $dts = new DateTime('@' . $start);
         $dts->setTimezone($this->timezone);
         $dte = new DateTime('@' . $t_end);
         $dte->setTimezone($this->timezone);
 
         // let this information be cached for 5min
         $this->rc->output->future_expire_header(300);
 
         echo rcube_output::json_serialize([
             'email' => $email,
             'start' => $dts->format('c'),
             'end'   => $dte->format('c'),
             'interval' => $interval,
             'slots' => $slots,
         ]);
         exit;
     }
 
     /**
      * Handler for printing calendars
      */
     public function print_view()
     {
         $title = $this->gettext('print');
 
         $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
         if (!in_array($view, ['agendaWeek', 'agendaDay', 'month', 'list'])) {
             $view = 'agendaDay';
         }
 
         $this->rc->output->set_env('view', $view);
 
         if ($date = rcube_utils::get_input_value('date', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('date', $date);
         }
 
         if ($range = rcube_utils::get_input_value('range', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('listRange', intval($range));
         }
 
         if ($search = rcube_utils::get_input_value('search', rcube_utils::INPUT_GPC)) {
             $this->rc->output->set_env('search', $search);
             $title .= ' "' . $search . '"';
         }
 
         // Add JS to the page
         $this->ui->addJS();
 
         $this->register_handler('plugin.calendar_css', [$this->ui, 'calendar_css']);
         $this->register_handler('plugin.calendar_list', [$this->ui, 'calendar_list']);
 
         $this->rc->output->set_pagetitle($title);
         $this->rc->output->send('calendar.print');
     }
 
     /**
      * Compare two event objects and return differing properties
      *
      * @param array Event A
      * @param array Event B
      *
      * @return array List of differing event properties
      */
     public static function event_diff($a, $b)
     {
         $diff   = [];
         $ignore = ['changed' => 1, 'attachments' => 1];
 
         foreach (array_unique(array_merge(array_keys($a), array_keys($b))) as $key) {
             if (empty($ignore[$key]) && $key[0] != '_') {
                 $av = isset($a[$key]) ? $a[$key] : null;
                 $bv = isset($b[$key]) ? $b[$key] : null;
 
                 if ($av != $bv) {
                     $diff[] = $key;
                 }
             }
         }
 
         // only compare number of attachments
         $ac = !empty($a['attachments']) ? count($a['attachments']) : 0;
         $bc = !empty($b['attachments']) ? count($b['attachments']) : 0;
 
         if ($ac != $bc) {
             $diff[] = 'attachments';
         }
 
         return $diff;
     }
 
     /**
      * Update attendee properties on the given event object
      *
      * @param array The event object to be altered
      * @param array List of hash arrays each represeting an updated/added attendee
      */
     public static function merge_attendee_data(&$event, $attendees, $removed = null)
     {
         if (!empty($attendees) && !is_array($attendees[0])) {
             $attendees = [$attendees];
         }
 
         foreach ($attendees as $attendee) {
             $found = false;
 
             foreach ($event['attendees'] as $i => $candidate) {
                 if ($candidate['email'] == $attendee['email']) {
                     $event['attendees'][$i] = $attendee;
                     $found = true;
                     break;
                 }
             }
 
             if (!$found) {
                 $event['attendees'][] = $attendee;
             }
         }
 
         // filter out removed attendees
         if (!empty($removed)) {
             $event['attendees'] = array_filter($event['attendees'], function($attendee) use ($removed) {
                 return !in_array($attendee['email'], $removed);
             });
         }
     }
 
     /****  Resource management functions  ****/
 
     /**
      * Getter for the configured implementation of the resource directory interface
      */
     private function resources_directory()
     {
         if (!empty($this->resources_dir)) {
             return $this->resources_dir;
         }
 
         if ($driver_name = $this->rc->config->get('calendar_resources_driver')) {
             $driver_class = 'resources_driver_' . $driver_name;
 
             require_once $this->home . '/drivers/resources_driver.php';
             require_once $this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php';
 
             $this->resources_dir = new $driver_class($this);
         }
 
         return $this->resources_dir;
     }
 
     /**
      * Handler for resoruce autocompletion requests
      */
     public function resources_autocomplete()
     {
         $search  = rcube_utils::get_input_value('_search', rcube_utils::INPUT_GPC, true);
         $sid     = rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC);
         $maxnum  = (int)$this->rc->config->get('autocomplete_max', 15);
         $results = [];
 
         if ($directory = $this->resources_directory()) {
             foreach ($directory->load_resources($search, $maxnum) as $rec) {
                 $results[]  = [
                     'name'  => $rec['name'],
                     'email' => $rec['email'],
                     'type'  => $rec['_type'],
                 ];
             }
         }
 
         $this->rc->output->command('ksearch_query_results', $results, $search, $sid);
         $this->rc->output->send();
     }
 
     /**
      * Handler for load-requests for resource data
      */
     function resources_list()
     {
         $data = [];
 
         if ($directory = $this->resources_directory()) {
             foreach ($directory->load_resources() as $rec) {
                 $data[] = $rec;
             }
         }
 
         $this->rc->output->command('plugin.resource_data', $data);
         $this->rc->output->send();
     }
 
     /**
      * Handler for requests loading resource owner information
      */
     function resources_owner()
     {
         if ($directory = $this->resources_directory()) {
             $id   = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
             $data = $directory->get_resource_owner($id);
         }
 
         $this->rc->output->command('plugin.resource_owner', $data);
         $this->rc->output->send();
     }
 
     /**
      * Deliver event data for a resource's calendar
      */
     function resources_calendar()
     {
         $events = [];
 
         if ($directory = $this->resources_directory()) {
             $id    = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
             $start = $this->input_timestamp('start', rcube_utils::INPUT_GET);
             $end   = $this->input_timestamp('end', rcube_utils::INPUT_GET);
 
             $events = $directory->get_resource_calendar($id, $start, $end);
         }
 
         echo $this->encode($events);
         exit;
     }
 
     /**
      * List email addressed of owned resources
      */
     private function owned_resources_emails()
     {
         $results = [];
         if ($directory = $this->resources_directory()) {
             foreach ($directory->load_resources($_SESSION['kolab_dn'], 5000, 'owner') as $rec) {
                 $results[] = $rec['email'];
             }
         }
         return $results;
     }
 
 
     /****  Event invitation plugin hooks ****/
 
     /**
      * Find an event in user calendars
      */
     protected function find_event($event, &$mode)
     {
         $this->load_driver();
 
         // We search for writeable calendars in personal namespace by default
         $mode   = calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL;
         $result = $this->driver->get_event($event, $mode);
         // ... now check shared folders if not found
         if (!$result) {
             $result = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_SHARED);
             if ($result) {
                 $mode |= calendar_driver::FILTER_SHARED;
             }
         }
 
         return $result;
     }
 
     /**
      * Handler for calendar/itip-status requests
      */
     function event_itip_status()
     {
         $data = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         $this->load_driver();
 
         // find local copy of the referenced event (in personal namespace)
         $existing  = $this->find_event($data, $mode);
         $is_shared = $mode & calendar_driver::FILTER_SHARED;
         $itip      = $this->load_itip();
         $response  = $itip->get_itip_status($data, $existing);
 
         // get a list of writeable calendars to save new events to
         if (
             (!$existing || $is_shared)
             && empty($data['nosave'])
             && ($response['action'] == 'rsvp' || $response['action'] == 'import')
         ) {
             $calendars       = $this->driver->list_calendars($mode);
             $calendar_select = new html_select([
                 'name'       => 'calendar',
                 'id'         => 'itip-saveto',
                 'is_escaped' => true,
                 'class'      => 'form-control custom-select'
             ]);
 
             $calendar_select->add('--', '');
             $numcals = 0;
             foreach ($calendars as $calendar) {
                 if (!empty($calendar['editable'])) {
                     $calendar_select->add($calendar['name'], $calendar['id']);
                     $numcals++;
                 }
             }
             if ($numcals < 1) {
                 $calendar_select = null;
             }
         }
 
         if (!empty($calendar_select)) {
             $default_calendar   = $this->get_default_calendar($calendars);
             $response['select'] = html::span('folder-select', $this->gettext('saveincalendar')
                 . '&nbsp;'
                 . $calendar_select->show($is_shared ? $existing['calendar'] : $default_calendar['id'])
             );
         }
         else if (!empty($data['nosave'])) {
             $response['select'] = html::tag('input', ['type' => 'hidden', 'name' => 'calendar', 'id' => 'itip-saveto', 'value' => '']);
         }
 
         // render small agenda view for the respective day
         if ($data['method'] == 'REQUEST' && !empty($data['date']) && $response['action'] == 'rsvp') {
             $event_start = rcube_utils::anytodatetime($data['date']);
             $day_start   = new Datetime(gmdate('Y-m-d 00:00', $data['date']), $this->lib->timezone);
             $day_end     = new Datetime(gmdate('Y-m-d 23:59', $data['date']), $this->lib->timezone);
 
             // get events on that day from the user's personal calendars
             $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL);
             $events    = $this->driver->load_events($day_start->format('U'), $day_end->format('U'), null, array_keys($calendars));
 
             usort($events, function($a, $b) { return $a['start'] > $b['start'] ? 1 : -1; });
 
             $before = $after = [];
             foreach ($events as $event) {
                 // TODO: skip events with free_busy == 'free' ?
                 if ($event['uid'] == $data['uid']
                     || $event['end'] < $day_start || $event['start'] > $day_end
                     || $event['status'] == 'CANCELLED'
                     || (!empty($event['className']) && strpos($event['className'], 'declined') !== false)
                 ) {
                     continue;
                 }
 
                 if ($event['start'] < $event_start) {
                     $before[] = $this->mail_agenda_event_row($event);
                 }
                 else {
                     $after[] = $this->mail_agenda_event_row($event);
                 }
             }
 
             $response['append'] = [
                 'selector' => '.calendar-agenda-preview',
                 'replacements' => [
                     '%before%' => !empty($before) ? join("\n", array_slice($before,  -3)) : html::div('event-row no-event', $this->gettext('noearlierevents')),
                     '%after%'  => !empty($after)  ? join("\n", array_slice($after, 0, 3)) : html::div('event-row no-event', $this->gettext('nolaterevents')),
                 ],
             ];
         }
 
         $this->rc->output->command('plugin.update_itip_object_status', $response);
     }
 
     /**
      * Handler for calendar/itip-remove requests
      */
     function event_itip_remove()
     {
         $uid      = rcube_utils::get_input_value('uid', rcube_utils::INPUT_POST);
         $instance = rcube_utils::get_input_value('_instance', rcube_utils::INPUT_POST);
         $savemode = rcube_utils::get_input_value('_savemode', rcube_utils::INPUT_POST);
         $listmode = calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL;
         $success  = false;
 
         // search for event if only UID is given
         if ($event = $this->driver->get_event(['uid' => $uid, '_instance' => $instance], $listmode)) {
             $event['_savemode'] = $savemode;
             $success = $this->driver->remove_event($event, true);
         }
 
         if ($success) {
             $this->rc->output->show_message('calendar.successremoval', 'confirmation');
         }
         else {
             $this->rc->output->show_message('calendar.errorsaving', 'error');
         }
     }
 
     /**
      * Handler for URLs that allow an invitee to respond on his invitation mail
      */
     public function itip_attend_response($p)
     {
         $this->setup();
 
         if ($p['action'] == 'attend') {
             $this->ui->init();
 
             $this->rc->output->set_env('task', 'calendar');  // override some env vars
             $this->rc->output->set_env('refresh_interval', 0);
             $this->rc->output->set_pagetitle($this->gettext('calendar'));
 
             $itip  = $this->load_itip();
             $token = rcube_utils::get_input_value('_t', rcube_utils::INPUT_GPC);
 
             // read event info stored under the given token
             if ($invitation = $itip->get_invitation($token)) {
                 $this->token = $token;
                 $this->event = $invitation['event'];
 
                 // show message about cancellation
                 if (!empty($invitation['cancelled'])) {
                     $this->invitestatus = html::div('rsvp-status declined', $itip->gettext('eventcancelled'));
                 }
                 // save submitted RSVP status
                 else if (!empty($_POST['rsvp'])) {
                     $status = null;
                     foreach (['accepted', 'tentative', 'declined'] as $method) {
                         if ($_POST['rsvp'] == $itip->gettext('itip' . $method)) {
                             $status = $method;
                             break;
                         }
                     }
 
                     // send itip reply to organizer
                     $invitation['event']['comment'] = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
                     if ($status && $itip->update_invitation($invitation, $invitation['attendee'], strtoupper($status))) {
                         $this->invitestatus = html::div('rsvp-status ' . strtolower($status), $itip->gettext('youhave'.strtolower($status)));
                     }
                     else {
                         $this->rc->output->command('display_message', $this->gettext('errorsaving'), 'error', -1);
                     }
 
                     // if user is logged in...
                     // FIXME: we should really consider removing this functionality
                     //        it's confusing that it creates/updates an event only for logged-in user
                     //        what if the logged-in user is not the same as the attendee?
                     if ($this->rc->user->ID) {
                         $this->load_driver();
 
                         $invitation = $itip->get_invitation($token);
                         $existing   = $this->driver->get_event($this->event);
 
                         // save the event to his/her default calendar if not yet present
                         if (!$existing && ($calendar = $this->get_default_calendar())) {
                             $invitation['event']['calendar'] = $calendar['id'];
                             if ($this->driver->new_event($invitation['event'])) {
                                 $msg = $this->gettext(['name' => 'importedsuccessfully', 'vars' => ['calendar' => $calendar['name']]]);
                                 $this->rc->output->command('display_message', $msg, 'confirmation');
                             }
                             else {
                                 $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
                             }
                         }
                         else if ($existing
                             && ($this->event['sequence'] >= $existing['sequence']
                                 || $this->event['changed'] >= $existing['changed'])
                             && ($calendar = $this->driver->get_calendar($existing['calendar']))
                         ) {
                             $this->event       = $invitation['event'];
                             $this->event['id'] = $existing['id'];
 
                             unset($this->event['comment']);
 
                             // merge attendees status
                             // e.g. preserve my participant status for regular updates
                             $this->lib->merge_attendees($this->event, $existing, $status);
 
                             // update attachments list
                             $event['deleted_attachments'] = true;
 
                             // show me as free when declined (#1670)
                             if ($status == 'declined') {
                                 $this->event['free_busy'] = 'free';
                             }
 
                             if ($this->driver->edit_event($this->event)) {
                                 $msg = $this->gettext(['name' => 'updatedsuccessfully', 'vars' => ['calendar' => $calendar->get_name()]]);
                                 $this->rc->output->command('display_message', $msg, 'confirmation');
                             }
                             else {
                                 $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
                             }
                         }
                     }
                 }
 
                 $this->register_handler('plugin.event_inviteform', [$this, 'itip_event_inviteform']);
                 $this->register_handler('plugin.event_invitebox', [$this->ui, 'event_invitebox']);
 
                 if (empty($this->invitestatus)) {
                     $this->itip->set_rsvp_actions(['accepted', 'tentative', 'declined']);
                     $this->register_handler('plugin.event_rsvp_buttons', [$this->ui, 'event_rsvp_buttons']);
                 }
 
                 $this->rc->output->set_pagetitle($itip->gettext('itipinvitation') . ' ' . $this->event['title']);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('itipinvalidrequest'), 'error', -1);
             }
 
             $this->rc->output->send('calendar.itipattend');
         }
     }
 
     /**
      *
      */
     public function itip_event_inviteform($attrib)
     {
         $hidden = new html_hiddenfield(['name' => "_t", 'value' => $this->token]);
 
         return html::tag('form', [
                 'action' => $this->rc->url(['task' => 'calendar', 'action' => 'attend']),
                 'method' => 'post',
                 'noclose' => true
             ] + $attrib
         ) . $hidden->show();
     }
 
     /**
      *
      */
     private function mail_agenda_event_row($event, $class = '')
     {
         if (!empty($event['allday'])) {
             $time = $this->gettext('all-day');
         }
         else {
             $start = is_object($event['start']) ? clone $event['start'] : $event['start'];
             $end = is_object($event['end']) ? clone $event['end'] : $event['end'];
 
             $time = $this->rc->format_date($start, $this->rc->config->get('time_format'))
                 . ' - ' . $this->rc->format_date($end, $this->rc->config->get('time_format'));
         }
 
         return html::div(rtrim('event-row ' . ($class ?: $event['className'])),
             html::span('event-date', $time)
             . html::span('event-title', rcube::Q($event['title']))
         );
     }
 
     /**
      *
      */
     public function mail_messages_list($p)
     {
         if (!empty($p['cols']) && in_array('attachment', (array) $p['cols']) && !empty($p['messages'])) {
             foreach ($p['messages'] as $header) {
                 $part = new StdClass;
                 $part->mimetype = $header->ctype;
 
                 if (libcalendaring::part_is_vcalendar($part)) {
                     $header->list_flags['attachmentClass'] = 'ical';
                 }
                 else if (in_array($header->ctype, ['multipart/alternative', 'multipart/mixed'])) {
                     // TODO: fetch bodystructure and search for ical parts. Maybe too expensive?
                     if (!empty($header->structure) && !empty($header->structure->parts)) {
                         foreach ($header->structure->parts as $part) {
                             if (libcalendaring::part_is_vcalendar($part)
                                 && !empty($part->ctype_parameters['method'])
                             ) {
                                 $header->list_flags['attachmentClass'] = 'ical';
                                 break;
                             }
                         }
                     }
                 }
             }
         }
     }
 
     /**
      * Add UI element to copy event invitations or updates to the calendar
      */
     public function mail_messagebody_html($p)
     {
         // load iCalendar functions (if necessary)
         if (!empty($this->lib->ical_parts)) {
             $this->get_ical();
             $this->load_itip();
         }
 
         $html = '';
         $has_events = false;
         $ical_objects = $this->lib->get_mail_ical_objects();
 
         // show a box for every event in the file
         foreach ($ical_objects as $idx => $event) {
             if ($event['_type'] != 'event') {
                 // skip non-event objects (#2928)
                 continue;
             }
 
             $has_events = true;
 
             // get prepared inline UI for this event object
             if ($ical_objects->method) {
                 $append   = '';
                 $date_str = $this->rc->format_date(clone $event['start'], $this->rc->config->get('date_format'), empty($event['start']->_dateonly));
                 $date     = new DateTime($event['start']->format('Y-m-d') . ' 12:00:00', new DateTimeZone('UTC'));
 
                 // prepare a small agenda preview to be filled with actual event data on async request
                 if ($ical_objects->method == 'REQUEST') {
                     $append = html::div('calendar-agenda-preview',
                         html::tag('h3', 'preview-title', $this->gettext('agenda') . ' ' . html::span('date', $date_str))
                         . '%before%' . $this->mail_agenda_event_row($event, 'current') . '%after%'
                     );
                 }
 
                 $html .= html::div('calendar-invitebox invitebox boxinformation',
                     $this->itip->mail_itip_inline_ui(
                         $event,
                         $ical_objects->method,
                         $ical_objects->mime_id . ':' . $idx,
                         'calendar',
                         rcube_utils::anytodatetime($ical_objects->message_date),
                         $this->rc->url(['task' => 'calendar']) . '&view=agendaDay&date=' . $date->format('U')
                     ) . $append
                 );
             }
 
             // limit listing
             if ($idx >= 3) {
                 break;
             }
         }
 
         // prepend event boxes to message body
         if ($html) {
             $this->ui->init();
             $p['content'] = $html . $p['content'];
             $this->rc->output->add_label('calendar.savingdata','calendar.deleteventconfirm','calendar.declinedeleteconfirm');
         }
 
         // add "Save to calendar" button into attachment menu
         if ($has_events) {
             $this->add_button([
                     'id'         => 'attachmentsavecal',
                     'name'       => 'attachmentsavecal',
                     'type'       => 'link',
                     'wrapper'    => 'li',
                     'command'    => 'attachment-save-calendar',
                     'class'      => 'icon calendarlink disabled',
                     'classact'   => 'icon calendarlink active',
                     'innerclass' => 'icon calendar',
                     'label'      => 'calendar.savetocalendar',
                 ],
                 'attachmentmenu'
             );
         }
 
         return $p;
     }
 
     /**
      * Handler for POST request to import an event attached to a mail message
      */
     public function mail_import_itip()
     {
         $itip_sending = $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $status  = rcube_utils::get_input_value('_status', rcube_utils::INPUT_POST);
         $delete  = intval(rcube_utils::get_input_value('_del', rcube_utils::INPUT_POST));
         $noreply = intval(rcube_utils::get_input_value('_noreply', rcube_utils::INPUT_POST));
         $noreply = $noreply || $status == 'needs-action' || $itip_sending === 0;
         $instance = rcube_utils::get_input_value('_instance', rcube_utils::INPUT_POST);
         $savemode = rcube_utils::get_input_value('_savemode', rcube_utils::INPUT_POST);
         $comment  = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
 
         $error_msg = $this->gettext('errorimportingevent');
         $success   = false;
         $deleted   = false;
 
         if ($status == 'delegated') {
             $to = rcube_utils::get_input_value('_to', rcube_utils::INPUT_POST, true);
             $delegates = rcube_mime::decode_address_list($to, 1, false);
             $delegate  = reset($delegates);
 
             if (empty($delegate) || empty($delegate['mailto'])) {
                 $this->rc->output->command('display_message', $this->rc->gettext('libcalendaring.delegateinvalidaddress'), 'error');
                 return;
             }
         }
 
         // successfully parsed events?
         if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
             // forward iTip request to delegatee
             if (!empty($delegate)) {
                 $rsvpme = rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST);
                 $itip   = $this->load_itip();
 
                 $event['comment'] = $comment;
 
                 if ($itip->delegate_to($event, $delegate, !empty($rsvpme))) {
                     $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
 
                 unset($event['comment']);
 
                 // the delegator is set to non-participant, thus save as non-blocking
                 $event['free_busy'] = 'free';
             }
 
             $mode = calendar_driver::FILTER_PERSONAL
                 | calendar_driver::FILTER_SHARED
                 | calendar_driver::FILTER_WRITEABLE;
 
             // find writeable calendar to store event
             $cal_id    = rcube_utils::get_input_value('_folder', rcube_utils::INPUT_POST);
             $dontsave  = $cal_id === '' && $event['_method'] == 'REQUEST';
             $calendars = $this->driver->list_calendars($mode);
             $calendar  = isset($calendars[$cal_id]) ? $calendars[$cal_id] : null;
 
             // select default calendar except user explicitly selected 'none'
             if (!$calendar && !$dontsave) {
                 $calendar = $this->get_default_calendar($calendars);
             }
 
             $metadata = [
                 'uid'       => $event['uid'],
                 '_instance' => isset($event['_instance']) ? $event['_instance'] : null,
                 'changed'   => is_object($event['changed']) ? $event['changed']->format('U') : 0,
                 'sequence'  => intval($event['sequence']),
                 'fallback'  => strtoupper($status),
                 'method'    => $event['_method'],
                 'task'      => 'calendar',
             ];
 
             // update my attendee status according to submitted method
             if (!empty($status)) {
                 $organizer = null;
                 $emails = $this->get_user_emails();
                 foreach ($event['attendees'] as $i => $attendee) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee;
                     }
                     else if (!empty($attendee['email']) && in_array(strtolower($attendee['email']), $emails)) {
                         $event['attendees'][$i]['status'] = strtoupper($status);
                         if (!in_array($event['attendees'][$i]['status'], ['NEEDS-ACTION', 'DELEGATED'])) {
                             $event['attendees'][$i]['rsvp'] = false;  // unset RSVP attribute
                         }
 
                         $metadata['attendee'] = $attendee['email'];
                         $metadata['rsvp']     = $attendee['role'] != 'NON-PARTICIPANT';
 
                         $reply_sender   = $attendee['email'];
                         $event_attendee = $attendee;
                     }
                 }
 
                 // add attendee with this user's default identity if not listed
                 if (!$reply_sender) {
                     $sender_identity = $this->rc->user->list_emails(true);
                     $event['attendees'][] = [
                         'name'   => $sender_identity['name'],
                         'email'  => $sender_identity['email'],
                         'role'   => 'OPT-PARTICIPANT',
                         'status' => strtoupper($status),
                     ];
                     $metadata['attendee'] = $sender_identity['email'];
                 }
             }
 
             // save to calendar
             if ($calendar && !empty($calendar['editable'])) {
                 // check for existing event with the same UID
                 $existing = $this->find_event($event, $mode);
 
                 // we'll create a new copy if user decided to change the calendar
                 if ($existing && $cal_id && $calendar && $calendar['id'] != $existing['calendar']) {
                     $existing = null;
                 }
 
                 if ($existing) {
                     $calendar = $calendars[$existing['calendar']];
 
                     // forward savemode for correct updates of recurring events
                     $existing['_savemode'] = $savemode ?: (!empty($event['_savemode']) ? $event['_savemode'] : null);
 
                     // only update attendee status
                     if ($event['_method'] == 'REPLY') {
                         $existing_attendee_index  = -1;
 
                         $event_attendee   = null;
                         $update_attendees = [];
 
                         if ($attendee = $this->itip->find_reply_attendee($event)) {
                             $event_attendee       = $attendee;
                             $update_attendees[]   = $attendee;
                             $metadata['fallback'] = $attendee['status'];
                             $metadata['attendee'] = $attendee['email'];
                             $metadata['rsvp']     = !empty($attendee['rsvp']) || $attendee['role'] != 'NON-PARTICIPANT';
 
                             $existing_attendee_emails = [];
 
                             // Find the attendee to update
                             foreach ($existing['attendees'] as $i => $existing_attendee) {
                                 $existing_attendee_emails[] = $existing_attendee['email'];
                                 if ($this->itip->compare_email($existing_attendee['email'], $attendee['email'])) {
                                     $existing_attendee_index = $i;
                                 }
                             }
 
                             if ($attendee['status'] == 'DELEGATED') {
                                 //Also find and copy the delegatee
                                 $delegatee_email = $attendee['email'];
                                 $delegatees = array_filter($event['attendees'], function($attendee) use ($delegatee_email){ return $attendee['role'] != 'ORGANIZER' && $this->itip->compare_email($attendee['delegated-from'], $delegatee_email); });
 
                                 if ($delegatee = $this->itip->find_attendee_by_email($event['attendees'], 'delegated-from', $attendee['email'])) {
                                     $update_attendees[] = $delegatee;
                                     if (!in_array_nocase($delegatee['email'], $existing_attendee_emails)) {
                                         $existing['attendees'][] = $delegated_attendee;
                                     }
                                 }
                             }
                         }
 
                         // if delegatee has declined, set delegator's RSVP=True
                         if ($event_attendee
                             && $event_attendee['status'] == 'DECLINED'
                             && !empty($event_attendee['delegated-from'])
                         ) {
                             foreach ($existing['attendees'] as $i => $attendee) {
                                 if ($attendee['email'] == $event_attendee['delegated-from']) {
                                     $existing['attendees'][$i]['rsvp'] = true;
                                     break;
                                 }
                             }
                         }
 
                         // found matching attendee entry in both existing and new events
                         if ($existing_attendee_index >= 0 && $event_attendee) {
                             $existing['attendees'][$existing_attendee_index] = $event_attendee;
                             $success = $this->driver->update_attendees($existing, $update_attendees);
                         }
                         // update the entire attendees block
                         else if (
                             ($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed'])
                             && $event_attendee
                         ) {
                             $existing['attendees'][] = $event_attendee;
                             $success = $this->driver->update_attendees($existing, $update_attendees);
                         }
                         else if (!$event_attendee) {
                             $error_msg = $this->gettext('errorunknownattendee');
                         }
                         else {
                             $error_msg = $this->gettext('newerversionexists');
                         }
                     }
                     // delete the event when declined (#1670)
                     else if ($status == 'declined' && $delete) {
                         $deleted = $this->driver->remove_event($existing, true);
                         $success = true;
                     }
                     // import the (newer) event
                     else if ($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed']) {
                         $event['id']       = $existing['id'];
                         $event['calendar'] = $existing['calendar'];
 
                         // merge attendees status
                         // e.g. preserve my participant status for regular updates
                         $this->lib->merge_attendees($event, $existing, $status);
 
                         // set status=CANCELLED on CANCEL messages
                         if ($event['_method'] == 'CANCEL') {
                             $event['status'] = 'CANCELLED';
                         }
 
                         // update attachments list, allow attachments update only on REQUEST (#5342)
                         if ($event['_method'] == 'REQUEST') {
                             $event['deleted_attachments'] = true;
                         }
                         else {
                             unset($event['attachments']);
                         }
 
                         // show me as free when declined (#1670)
                         if ($status == 'declined'
                             || (!empty($event['status']) && $event['status'] == 'CANCELLED')
                             || $event_attendee['role'] == 'NON-PARTICIPANT'
                         ) {
                             $event['free_busy'] = 'free';
                         }
 
                         $success = $this->driver->edit_event($event);
                     }
                     else if (!empty($status)) {
                         $existing['attendees'] = $event['attendees'];
                         if ($status == 'declined' || $event_attendee['role'] == 'NON-PARTICIPANT') {
                             // show me as free when declined (#1670)
                             $existing['free_busy'] = 'free';
                         }
                         $success = $this->driver->edit_event($existing);
                     }
                     else {
                         $error_msg = $this->gettext('newerversionexists');
                     }
                 }
                 else if (!$existing && ($status != 'declined' || $this->rc->config->get('kolab_invitation_calendars'))) {
                     if ($status == 'declined'
                         || $event['status'] == 'CANCELLED'
                         || $event_attendee['role'] == 'NON-PARTICIPANT'
                     ) {
                         $event['free_busy'] = 'free';
                     }
 
                     // if the RSVP reply only refers to a single instance:
                     // store unmodified master event with current instance as exception
                     if (!empty($instance) && !empty($savemode) && $savemode != 'all') {
                         $master = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event');
                         if ($master['recurrence'] && empty($master['_instance'])) {
                             // compute recurring events until this instance's date
                             if ($recurrence_date = rcube_utils::anytodatetime($instance, $master['start']->getTimezone())) {
                                 $recurrence_date->setTime(23,59,59);
 
                                 foreach ($this->driver->get_recurring_events($master, $master['start'], $recurrence_date) as $recurring) {
                                     if ($recurring['_instance'] == $instance) {
                                         // copy attendees block with my partstat to exception
                                         $recurring['attendees'] = $event['attendees'];
                                         $master['recurrence']['EXCEPTIONS'][] = $recurring;
                                         $event = $recurring;  // set reference for iTip reply
                                         break;
                                     }
                                 }
 
                                 $master['calendar'] = $event['calendar'] = $calendar['id'];
                                 $success = $this->driver->new_event($master);
                             }
                             else {
                                 $master = null;
                             }
                         }
                         else {
                             $master = null;
                         }
                     }
 
                     // save to the selected/default calendar
                     if (!$master) {
                         $event['calendar'] = $calendar['id'];
                         $success = $this->driver->new_event($event);
                     }
                 }
                 else if ($status == 'declined') {
                     $error_msg = null;
                 }
             }
             else if ($status == 'declined' || $dontsave) {
                 $error_msg = null;
             }
             else {
                 $error_msg = $this->gettext('nowritecalendarfound');
             }
         }
 
         if ($success) {
             if ($event['_method'] == 'REPLY') {
                 $message = 'attendeupdateesuccess';
             }
             else {
                 $message = $deleted ? 'successremoval' : ($existing ? 'updatedsuccessfully' : 'importedsuccessfully');
             }
 
             $msg = $this->gettext(['name' => $message, 'vars' => ['calendar' => $calendar['name']]]);
             $this->rc->output->command('display_message', $msg, 'confirmation');
         }
 
         if ($success || $dontsave) {
             $metadata['calendar'] = isset($event['calendar']) ? $event['calendar'] : null;
             $metadata['nosave']   = $dontsave;
             $metadata['rsvp']     = !empty($metadata['rsvp']);
 
             $metadata['after_action'] = $this->rc->config->get('calendar_itip_after_action', $this->defaults['calendar_itip_after_action']);
             $this->rc->output->command('plugin.itip_message_processed', $metadata);
             $error_msg = null;
         }
         else if ($error_msg) {
             $this->rc->output->command('display_message', $error_msg, 'error');
         }
 
         // send iTip reply
         if ($event['_method'] == 'REQUEST' && !empty($organizer) && !$noreply
             && !in_array(strtolower($organizer['email']), $emails) && !$error_msg
         ) {
             $event['comment'] = $comment;
             $itip = $this->load_itip();
             $itip->set_sender_email($reply_sender);
 
             if ($itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status)) {
                 $mailto = $organizer['name'] ? $organizer['name'] : $organizer['email'];
                 $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
                 $this->rc->output->command('display_message', $msg, 'confirmation');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
             }
         }
 
         $this->rc->output->send();
     }
 
     /**
      * Handler for calendar/itip-remove requests
      */
     function mail_itip_decline_reply()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
 
         if (($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event'))
             && $event['_method'] == 'REPLY'
         ) {
             $event['comment'] = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
 
             foreach ($event['attendees'] as $_attendee) {
                 if ($_attendee['role'] != 'ORGANIZER') {
                     $attendee = $_attendee;
                     break;
                 }
             }
 
             $itip = $this->load_itip();
 
             if ($itip->send_itip_message($event, 'CANCEL', $attendee, 'itipsubjectcancel', 'itipmailbodycancel')) {
                 $mailto = !empty($attendee['name']) ? $attendee['name'] : $attendee['email'];
                 $msg    = $this->gettext(['name' => 'sentresponseto', 'vars' => ['mailto' => $mailto]]);
                 $this->rc->output->command('display_message', $msg, 'confirmation');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
             }
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
         }
     }
 
     /**
      * Handler for calendar/itip-delegate requests
      */
     function mail_itip_delegate()
     {
         // forward request to mail_import_itip() with the right status
         $_POST['_status'] = $_REQUEST['_status'] = 'delegated';
         $this->mail_import_itip();
     }
 
     /**
      * Import the full payload from a mail message attachment
      */
     public function mail_import_attachment()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             $part = $imap->get_message_part($uid, $mime_id);
             // $headers = $imap->get_message_headers($uid);
 
             if ($part) {
                 if (!empty($part->ctype_parameters['charset'])) {
                     $charset = $part->ctype_parameters['charset'];
                 }
                 $events = $this->get_ical()->import($part, $charset);
             }
         }
 
         $success = $existing = 0;
 
         if (!empty($events)) {
             // find writeable calendar to store event
             $cal_id = !empty($_REQUEST['_calendar']) ? rcube_utils::get_input_value('_calendar', rcube_utils::INPUT_POST) : null;
             $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL);
 
             foreach ($events as $event) {
                 // save to calendar
                 $calendar = !empty($calendars[$cal_id]) ? $calendars[$cal_id] : $this->get_default_calendar();
                 if ($calendar && $calendar['editable'] && $event['_type'] == 'event') {
                     $event['calendar'] = $calendar['id'];
 
                     if (!$this->driver->get_event($event['uid'], calendar_driver::FILTER_WRITEABLE)) {
                         $success += (bool)$this->driver->new_event($event);
                     }
                     else {
                         $existing++;
                     }
                 }
             }
         }
 
         if ($success) {
             $msg = $this->gettext(['name' => 'importsuccess', 'vars' => ['nr' => $success]]);
             $this->rc->output->command('display_message', $msg, 'confirmation');
         }
         else if ($existing) {
             $this->rc->output->command('display_message', $this->gettext('importwarningexists'), 'warning');
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
         }
     }
 
     /**
      * Read email message and return contents for a new event based on that message
      */
     public function mail_message2event()
     {
         $this->ui->init();
         $this->ui->addJS();
         $this->ui->init_templates();
         $this->ui->calendar_list([], true); // set env['calendars']
 
         $uid   = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GET);
         $mbox  = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_GET);
         $event = [];
 
         // establish imap connection
         $imap    = $this->rc->get_storage();
         $message = new rcube_message($uid, $mbox);
 
         if ($message->headers) {
             $event['title']       = trim($message->subject);
             $event['description'] = trim($message->first_text_part());
 
             $this->load_driver();
 
             // add a reference to the email message
             if ($msgref = $this->driver->get_message_reference($message->headers, $mbox)) {
                 $event['links'] = [$msgref];
             }
             // copy mail attachments to event
             else if (!empty($message->attachments) && !empty($this->driver->attachments)) {
                 $handler = new kolab_attachments_handler();
                 $event['attachments'] = $handler->copy_mail_attachments(self::SESSION_KEY, 'cal-', $message);
             }
 
             $this->rc->output->set_env('event_prop', $event);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
         }
 
         $this->rc->output->send('calendar.dialog');
     }
 
     /**
      * Handler for the 'message_compose' plugin hook. This will check for
      * a compose parameter 'calendar_event' and create an attachment with the
      * referenced event in iCal format
      */
     public function mail_message_compose($args)
     {
         // set the submitted event ID as attachment
         if (!empty($args['param']['calendar_event'])) {
             $this->load_driver();
 
             list($cal, $id) = explode(':', $args['param']['calendar_event'], 2);
 
             if ($event = $this->driver->get_event(['id' => $id, 'calendar' => $cal])) {
                 $filename = asciiwords($event['title']);
                 if (empty($filename)) {
                     $filename = 'event';
                 }
 
                 // save ics to a temp file and register as attachment
                 $tmp_path = tempnam($this->rc->config->get('temp_dir'), 'rcmAttmntCal');
                 $export   = $this->get_ical()->export([$event], '', false, [$this->driver, 'get_attachment_body']);
 
                 file_put_contents($tmp_path, $export);
 
                 $args['attachments'][] = [
                     'path'     => $tmp_path,
                     'name'     => $filename . '.ics',
                     'mimetype' => 'text/calendar',
                     'size'     => filesize($tmp_path),
                 ];
                 $args['param']['subject'] = $event['title'];
             }
         }
 
         return $args;
     }
 
     /**
      * Create a Nextcould Talk room
      */
     public function talk_room_create()
     {
         require_once __DIR__ . '/lib/calendar_nextcloud_api.php';
 
         $api = new calendar_nextcloud_api();
 
         $name = (string) rcube_utils::get_input_value('_name', rcube_utils::INPUT_POST);
 
         $room_url = $api->talk_room_create($name);
 
         if ($room_url) {
             $this->rc->output->command('plugin.talk_room_created', ['url' => $room_url]);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('talkroomcreateerror'), 'error');
         }
     }
 
     /**
      * Update a Nextcould Talk room
      */
     public function talk_room_update($event)
     {
         // If a room is assigned to the event...
         if (
             ($talk_url = $this->rc->config->get('calendar_nextcloud_url'))
             && isset($event['attendees'])
             && !empty($event['location'])
             && strpos($event['location'], unslashify($talk_url) . '/call/') === 0
         ) {
             $participants = [];
             $organizer = null;
 
             // ollect participants' and organizer's email addresses
             foreach ($event['attendees'] as $attendee) {
                 if (!empty($attendee['email'])) {
                     if ($attendee['role'] == 'ORGANIZER') {
                         $organizer = $attendee['email'];
                     }
                     else if ($attendee['cutype'] == 'INDIVIDUAL') {
                         $participants[] = $attendee['email'];
                     }
                 }
             }
 
             // If the event is owned by the current user update the room
             if ($organizer && in_array($organizer, $this->get_user_emails())) {
                 require_once __DIR__ . '/lib/calendar_nextcloud_api.php';
 
                 $api = new calendar_nextcloud_api();
 
                 $api->talk_room_update($event['location'], $participants);
             }
         }
     }
 
     /**
      * Get a list of email addresses of the current user (from login and identities)
      */
     public function get_user_emails()
     {
         return $this->lib->get_user_emails();
     }
 
     /**
      * Build an absolute URL with the given parameters
      */
     public function get_url($param = [])
     {
         $param += ['task' => 'calendar'];
         return $this->rc->url($param, true, true);
     }
 
     public function ical_feed_hash($source)
     {
         return base64_encode($this->rc->user->get_username() . ':' . $source);
     }
 
     /**
      * Handler for user_delete plugin hook
      */
     public function user_delete($args)
     {
          // delete itipinvitations entries related to this user
          $db = $this->rc->get_dbh();
          $table_itipinvitations = $db->table_name('itipinvitations', true);
 
          $db->query("DELETE FROM $table_itipinvitations WHERE `user_id` = ?", $args['user']->ID);
 
         $this->setup();
         $this->load_driver();
 
         return $this->driver->user_delete($args);
     }
 
     /**
      * Find first occurrence of a recurring event excluding start date
      *
      * @param array $event Event data (with 'start' and 'recurrence')
      *
      * @return DateTime Date of the first occurrence
      */
     public function find_first_occurrence($event)
     {
         // Make sure libkolab/libcalendaring plugins are loaded
         $this->load_driver();
 
         $driver_name = $this->rc->config->get('calendar_driver', 'database');
 
         // Use kolabcalendaring/kolabformat to compute recurring events only with the Kolab driver
         if ($driver_name == 'kolab' && 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 recurrence implementation
             $recurrence = new libcalendaring_recurrence($this->lib, $event);
         }
 
         return $recurrence->first_occurrence();
     }
 
     /**
      * Get date-time input from UI and convert to unix timestamp
      */
     protected function input_timestamp($name, $type)
     {
         $ts = rcube_utils::get_input_value($name, $type);
 
         if ($ts && (!is_numeric($ts) || strpos($ts, 'T'))) {
             $ts = new DateTime($ts, $this->timezone);
             $ts = $ts->getTimestamp();
         }
 
         return $ts;
     }
 
     /**
      * Magic getter for public access to protected members
      */
     public function __get($name)
     {
         switch ($name) {
         case 'ical':
             return $this->get_ical();
 
         case 'itip':
             return $this->load_itip();
 
         case 'driver':
             $this->load_driver();
             return $this->driver;
         }
 
         return null;
     }
 }
diff --git a/plugins/tasklist/tasklist.php b/plugins/tasklist/tasklist.php
index f57848c4..e17aa635 100644
--- a/plugins/tasklist/tasklist.php
+++ b/plugins/tasklist/tasklist.php
@@ -1,2506 +1,2506 @@
 <?php
 
 /**
  * Tasks plugin for Roundcube webmail
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #[AllowDynamicProperties]
 class tasklist extends rcube_plugin
 {
     const FILTER_MASK_TODAY = 1;
     const FILTER_MASK_TOMORROW = 2;
     const FILTER_MASK_WEEK = 4;
     const FILTER_MASK_LATER = 8;
     const FILTER_MASK_NODATE = 16;
     const FILTER_MASK_OVERDUE = 32;
     const FILTER_MASK_FLAGGED = 64;
     const FILTER_MASK_COMPLETE = 128;
     const FILTER_MASK_ASSIGNED = 256;
     const FILTER_MASK_MYTASKS = 512;
 
     const SESSION_KEY = 'tasklist_temp';
 
     public static $filter_masks = array(
         'today'    => self::FILTER_MASK_TODAY,
         'tomorrow' => self::FILTER_MASK_TOMORROW,
         'week'     => self::FILTER_MASK_WEEK,
         'later'    => self::FILTER_MASK_LATER,
         'nodate'   => self::FILTER_MASK_NODATE,
         'overdue'  => self::FILTER_MASK_OVERDUE,
         'flagged'  => self::FILTER_MASK_FLAGGED,
         'complete' => self::FILTER_MASK_COMPLETE,
         'assigned' => self::FILTER_MASK_ASSIGNED,
         'mytasks'  => self::FILTER_MASK_MYTASKS,
     );
 
     public $task = '?(?!login|logout).*';
     public $allowed_prefs = array('tasklist_sort_col','tasklist_sort_order');
 
     public $rc;
     public $lib;
     public $timezone;
     public $ui;
     public $home;  // declare public to be used in other classes
 
     // These are handled by __get()
     // public $driver;
     // public $itip;
     // public $ical;
 
     private $collapsed_tasks = array();
     private $message_tasks   = array();
     private $task_titles     = array();
 
 
     /**
      * Plugin initialization.
      */
     function init()
     {
         $this->require_plugin('libcalendaring');
         $this->require_plugin('libkolab');
 
         // load plugin configuration
         $this->load_config();
 
         $this->rc       = rcube::get_instance();
         $this->lib      = libcalendaring::get_instance();
         $this->timezone = $this->lib->timezone;
 
         $this->register_task('tasks', 'tasklist');
 
         $this->add_hook('startup', array($this, 'startup'));
         $this->add_hook('user_delete', array($this, 'user_delete'));
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         // the tasks module can be enabled/disabled by the kolab_auth plugin
         if ($this->rc->config->get('tasklist_disabled', false) || !$this->rc->config->get('tasklist_enabled', true)) {
             return;
         }
 
         // load localizations
         $this->add_texts('localization/', $args['task'] == 'tasks' && (!$args['action'] || $args['action'] == 'print'));
         $this->rc->load_language($_SESSION['language'], array('tasks.tasks' => $this->gettext('navtitle')));  // add label for task title
 
         if ($args['task'] == 'tasks' && $args['action'] != 'save-pref') {
             $this->load_driver();
 
             // register calendar actions
             $this->register_action('index', array($this, 'tasklist_view'));
             $this->register_action('task', array($this, 'task_action'));
             $this->register_action('tasklist', array($this, 'tasklist_action'));
             $this->register_action('counts', array($this, 'fetch_counts'));
             $this->register_action('fetch', array($this, 'fetch_tasks'));
             $this->register_action('print', array($this, 'print_tasks'));
             $this->register_action('dialog-ui', array($this, 'mail_message2task'));
             $this->register_action('get-attachment', array($this, 'attachment_get'));
             $this->register_action('upload', array($this, 'attachment_upload'));
             $this->register_action('import', array($this, 'import_tasks'));
             $this->register_action('export', array($this, 'export_tasks'));
             $this->register_action('mailimportitip', array($this, 'mail_import_itip'));
             $this->register_action('mailimportattach', array($this, 'mail_import_attachment'));
             $this->register_action('itip-status', array($this, 'task_itip_status'));
             $this->register_action('itip-remove', array($this, 'task_itip_remove'));
             $this->register_action('itip-decline-reply', array($this, 'mail_itip_decline_reply'));
             $this->register_action('itip-delegate', array($this, 'mail_itip_delegate'));
             $this->add_hook('refresh', array($this, 'refresh'));
 
             $this->collapsed_tasks = array_filter(explode(',', $this->rc->config->get('tasklist_collapsed_tasks', '')));
         }
         else if ($args['task'] == 'mail') {
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 if ($this->rc->config->get('tasklist_mail_embed', true)) {
                     $this->add_hook('message_load', array($this, 'mail_message_load'));
                 }
                 $this->add_hook('template_object_messagebody', array($this, 'mail_messagebody_html'));
             }
 
             // add 'Create event' item to message menu
             if ($this->api->output->type == 'html' && (empty($_GET['_rel']) || $_GET['_rel'] != 'task')) {
                 $this->api->add_content(html::tag('li', array('role' => 'menuitem'),
                     $this->api->output->button(array(
                         'command'  => 'tasklist-create-from-mail',
                         'label'    => 'tasklist.createfrommail',
                         'type'     => 'link',
                         'classact' => 'icon taskaddlink active',
                         'class'    => 'icon taskaddlink disabled',
                         'innerclass' => 'icon taskadd',
                     ))),
                 'messagemenu');
 
                 $this->api->output->add_label('tasklist.createfrommail');
             }
         }
 
         if (!$this->rc->output->ajax_call && empty($this->rc->output->env['framed'])) {
-            // A hack to replace "Edit/Share List" label with "Edit list", for CalDAV driver
-            if ($args['task'] == 'tasks' && $this->rc->config->get('tasklist_driver', 'database') === 'caldav') {
+            // A hack to replace "Edit/Share List" label with "Edit list", for non-Kolab drivers
+            if ($args['task'] == 'tasks' && $this->rc->config->get('tasklist_driver', 'database') !== 'kolab') {
                 $merge = ['tasklist.editlist' => $this->gettext('edlist')];
                 $this->rc->load_language(null, [], $merge);
                 $this->rc->output->command('add_label', $merge);
             }
 
             $this->load_ui();
             $this->ui->init();
         }
 
         // add hooks for alarms handling
         $this->add_hook('pending_alarms', array($this, 'pending_alarms'));
         $this->add_hook('dismiss_alarms', array($this, 'dismiss_alarms'));
     }
 
     /**
      *
      */
     private function load_ui()
     {
         if (!$this->ui) {
             require_once($this->home . '/tasklist_ui.php');
             $this->ui = new tasklist_ui($this);
         }
     }
 
     /**
      * Helper method to load the backend driver according to local config
      */
     private function load_driver()
     {
         if (!empty($this->driver)) {
             return;
         }
 
         $driver_name  = $this->rc->config->get('tasklist_driver', 'database');
         $driver_class = 'tasklist_' . $driver_name . '_driver';
 
         require_once $this->home . '/drivers/tasklist_driver.php';
         require_once $this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php';
 
         $this->driver = new $driver_class($this);
 
         $this->rc->output->set_env('tasklist_driver', $driver_name);
     }
 
     /**
      * Dispatcher for task-related actions initiated by the client
      */
     public function task_action()
     {
         $filter = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $action = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $rec    = rcube_utils::get_input_value('t', rcube_utils::INPUT_POST, true);
         $oldrec = $rec;
         $success = $got_msg = false;
         $refresh = [];
 
         // force notify if hidden + active
         $itip_send_option = (int)$this->rc->config->get('calendar_itip_send_option', 3);
         if ($itip_send_option === 1 && empty($rec['_reportpartstat'])) {
             $rec['_notify'] = 1;
         }
 
         switch ($action) {
         case 'new':
             $oldrec = null;
             $rec = $this->prepare_task($rec);
             $rec['uid'] = $this->generate_uid();
             $temp_id = !empty($rec['tempid']) ? $rec['tempid'] : null;
             if ($success = $this->driver->create_task($rec)) {
                 $refresh = $this->driver->get_task($rec);
                 if ($temp_id) $refresh['tempid'] = $temp_id;
                 $this->cleanup_task($rec);
             }
             break;
 
         case 'complete':
             $complete = intval(rcube_utils::get_input_value('complete', rcube_utils::INPUT_POST));
             if (!($rec = $this->driver->get_task($rec))) {
                 break;
             }
 
             $oldrec = $rec;
             $rec['status'] = $complete ? 'COMPLETED' : ($rec['complete'] > 0 ? 'IN-PROCESS' : 'NEEDS-ACTION');
 
             // sent itip notifications if enabled (no user interaction here)
             if (($itip_send_option & 1)) {
                 if ($this->is_attendee($rec)) {
                     $rec['_reportpartstat'] = $rec['status'];
                 }
                 else if ($this->is_organizer($rec)) {
                     $rec['_notify'] = 1;
                 }
             }
 
         case 'edit':
             $oldrec = $this->driver->get_task($rec);
             $rec = $this->prepare_task($rec);
             $clone = $this->handle_recurrence($rec, $this->driver->get_task($rec));
             if ($success = $this->driver->edit_task($rec)) {
                 $new_task = $this->driver->get_task($rec);
                 $new_task['tempid'] = $rec['id'];
                 $refresh[] = $new_task;
                 $this->cleanup_task($rec);
 
                 // add clone from recurring task
                 if ($clone && $this->driver->create_task($clone)) {
                     $new_clone = $this->driver->get_task($clone);
                     $new_clone['tempid'] = $clone['id'];
                     $refresh[] = $new_clone;
                     $this->driver->clear_alarms($rec['id']);
                 }
 
                 // move all childs if list assignment was changed
                 if (!empty($rec['_fromlist']) && !empty($rec['list']) && $rec['_fromlist'] != $rec['list']) {
                     foreach ($this->driver->get_childs(array('id' => $rec['id'], 'list' => $rec['_fromlist']), true) as $cid) {
                         $child = array('id' => $cid, 'list' => $rec['list'], '_fromlist' => $rec['_fromlist']);
                         if ($this->driver->move_task($child)) {
                             $r = $this->driver->get_task($child);
                             if ((bool)($filter & self::FILTER_MASK_COMPLETE) == $this->driver->is_complete($r)) {
                                 $r['tempid'] = $cid;
                                 $refresh[] = $r;
                             }
                         }
                     }
                 }
             }
             break;
 
           case 'move':
               foreach ((array)$rec['id'] as $id) {
                   $r = $rec;
                   $r['id'] = $id;
                   if ($this->driver->move_task($r) && ($new_task = $this->driver->get_task($r))) {
                       $new_task['tempid'] = $id;
                       $refresh[] = $new_task;
                       $success = true;
 
                       // move all childs, too
                       foreach ($this->driver->get_childs(array('id' => $id, 'list' => $rec['_fromlist']), true) as $cid) {
                           $child = $rec;
                           $child['id'] = $cid;
                           if ($this->driver->move_task($child)) {
                               $r = $this->driver->get_task($child);
                               if ((bool)($filter & self::FILTER_MASK_COMPLETE) == $this->driver->is_complete($r)) {
                                   $r['tempid'] = $cid;
                                   $refresh[] = $r;
                               }
                           }
                       }
                   }
               }
               break;
 
         case 'delete':
             $mode  = intval(rcube_utils::get_input_value('mode', rcube_utils::INPUT_POST));
             $oldrec = $this->driver->get_task($rec);
             if ($success = $this->driver->delete_task($rec, false)) {
                 // delete/modify all childs
                 foreach ($this->driver->get_childs($rec, $mode) as $cid) {
                     $child = array('id' => $cid, 'list' => $rec['list']);
 
                     if ($mode == 1) {  // delete all childs
                         if ($this->driver->delete_task($child, false)) {
                             if ($this->driver->undelete)
                                 $_SESSION['tasklist_undelete'][$rec['id']][] = $cid;
                         }
                         else
                             $success = false;
                     }
                     else {
                         $child['parent_id'] = strval($oldrec['parent_id']);
                         $this->driver->edit_task($child);
                     }
                 }
                 // update parent task to adjust list of children
                 if (!empty($oldrec['parent_id'])) {
                     $parent = array('id' => $oldrec['parent_id'], 'list' => $rec['list']);
                     if ($parent = $this->driver->get_task($parent)) {
                         $refresh[] = $parent;
                     }
                 }
             }
 
             if (!$success)
                 $this->rc->output->command('plugin.reload_data');
             break;
 
         case 'undelete':
             if ($success = $this->driver->undelete_task($rec)) {
                 $refresh[] = $this->driver->get_task($rec);
                 foreach ((array)$_SESSION['tasklist_undelete'][$rec['id']] as $cid) {
                     if ($this->driver->undelete_task($rec)) {
                         $refresh[] = $this->driver->get_task($rec);
                     }
                 }
             }
             break;
 
         case 'collapse':
             foreach (explode(',', $rec['id']) as $rec_id) {
                 if (intval(rcube_utils::get_input_value('collapsed', rcube_utils::INPUT_GPC))) {
                     $this->collapsed_tasks[] = $rec_id;
                 }
                 else {
                     $i = array_search($rec_id, $this->collapsed_tasks);
                     if ($i !== false)
                         unset($this->collapsed_tasks[$i]);
                 }
             }
 
             $this->rc->user->save_prefs(array('tasklist_collapsed_tasks' => join(',', array_unique($this->collapsed_tasks))));
             return;  // avoid further actions
 
         case 'rsvp':
             $status = rcube_utils::get_input_value('status', rcube_utils::INPUT_GPC);
             $noreply = intval(rcube_utils::get_input_value('noreply', rcube_utils::INPUT_GPC)) || $status == 'needs-action';
             $task = $this->driver->get_task($rec);
             $task['attendees'] = $rec['attendees'];
             $task['_type'] = 'task';
 
             // send invitation to delegatee + add it as attendee
             if ($status == 'delegated' && $rec['to']) {
                 $itip = $this->load_itip();
                 if ($itip->delegate_to($task, $rec['to'], (bool)$rec['rsvp'])) {
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                     $refresh[] = $task;
                     $noreply = false;
                 }
             }
 
             $rec = $task;
 
             if ($success = $this->driver->edit_task($rec)) {
                 if (!$noreply) {
                     // let the reply clause further down send the iTip message
                     $rec['_reportpartstat'] = $status;
                 }
             }
             break;
 
         case 'changelog':
             $data = $this->driver->get_task_changelog($rec);
             if (is_array($data) && !empty($data)) {
                 $lib = $this->lib;
                 $dtformat = $this->rc->config->get('date_format') . ' ' . $this->rc->config->get('time_format');
                 array_walk($data, function(&$change) use ($lib, $dtformat) {
                   if ($change['date']) {
                       $dt = $lib->adjust_timezone($change['date']);
                       if ($dt instanceof DateTime) {
                           $change['date'] = $this->rc->format_date($dt, $dtformat, false);
                       }
                   }
                 });
                 $this->rc->output->command('plugin.task_render_changelog', $data);
             }
             else {
                 $this->rc->output->command('plugin.task_render_changelog', false);
             }
             $got_msg = true;
             break;
 
         case 'diff':
             $data = $this->driver->get_task_diff($rec, $rec['rev1'], $rec['rev2']);
             if (is_array($data)) {
                 // convert some properties, similar to self::_client_event()
                 $lib = $this->lib;
                 $date_format = $this->rc->config->get('date_format', 'Y-m-d');
                 $time_format = $this->rc->config->get('time_format', 'H:i');
                 array_walk($data['changes'], function(&$change, $i) use ($lib, $date_format, $time_format) {
                     // convert date cols
                     if (in_array($change['property'], array('date','start','created','changed'))) {
                         if (!empty($change['old'])) {
                             $dtformat = strlen($change['old']) == 10 ? $date_format : $date_format . ' ' . $time_format;
                             $change['old_'] = $lib->adjust_timezone($change['old'], strlen($change['old']) == 10)->format($dtformat);
                         }
                         if (!empty($change['new'])) {
                             $dtformat = strlen($change['new']) == 10 ? $date_format : $date_format . ' ' . $time_format;
                             $change['new_'] = $lib->adjust_timezone($change['new'], strlen($change['new']) == 10)->format($dtformat);
                         }
                     }
                     // create textual representation for alarms and recurrence
                     if ($change['property'] == 'alarms') {
                         if (is_array($change['old']))
                             $change['old_'] = libcalendaring::alarm_text($change['old']);
                         if (is_array($change['new']))
                             $change['new_'] = libcalendaring::alarm_text(array_merge((array)$change['old'], $change['new']));
                     }
                     if ($change['property'] == 'recurrence') {
                         if (is_array($change['old']))
                             $change['old_'] = $lib->recurrence_text($change['old']);
                         if (is_array($change['new']))
                             $change['new_'] = $lib->recurrence_text(array_merge((array)$change['old'], $change['new']));
                     }
                     if ($change['property'] == 'complete') {
                         $change['old_'] = intval($change['old']) . '%';
                         $change['new_'] = intval($change['new']) . '%';
                     }
                     if ($change['property'] == 'attachments') {
                         if (is_array($change['old']))
                             $change['old']['classname'] = rcube_utils::file2class($change['old']['mimetype'], $change['old']['name']);
                         if (is_array($change['new'])) {
                             $change['new'] = array_merge((array)$change['old'], $change['new']);
                             $change['new']['classname'] = rcube_utils::file2class($change['new']['mimetype'], $change['new']['name']);
                         }
                     }
                     // resolve parent_id to the refered task title for display
                     if ($change['property'] == 'parent_id') {
                         $change['property'] = 'parent-title';
                         if (!empty($change['old']) && ($old_parent = $this->driver->get_task(array('id' => $change['old'], 'list' => $rec['list'])))) {
                             $change['old_'] = $old_parent['title'];
                         }
                         if (!empty($change['new']) && ($new_parent = $this->driver->get_task(array('id' => $change['new'], 'list' => $rec['list'])))) {
                             $change['new_'] = $new_parent['title'];
                         }
                     }
                     // compute a nice diff of description texts
                     if ($change['property'] == 'description') {
                         $change['diff_'] = libkolab::html_diff($change['old'], $change['new']);
                     }
                 });
                 $this->rc->output->command('plugin.task_show_diff', $data);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectdiffnotavailable'), 'error');
             }
             $got_msg = true;
             break;
 
         case 'show':
             if ($rec = $this->driver->get_task_revison($rec, $rec['rev'])) {
                 $this->encode_task($rec);
                 $rec['readonly'] = 1;
                 $this->rc->output->command('plugin.task_show_revision', $rec);
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectnotfound'), 'error');
             }
             $got_msg = true;
             break;
 
         case 'restore':
             if ($success = $this->driver->restore_task_revision($rec, $rec['rev'])) {
                 $refresh = $this->driver->get_task($rec);
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'objectrestoresuccess', 'vars' => array('rev' => $rec['rev']))), 'confirmation');
                 $this->rc->output->command('plugin.close_history_dialog');
             }
             else {
                 $this->rc->output->command('display_message', $this->gettext('objectrestoreerror'), 'error');
             }
             $got_msg = true;
             break;
 
         }
 
         if ($success) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
             $this->update_counts($oldrec, $refresh);
         }
         else if (!$got_msg) {
             $this->rc->output->show_message('tasklist.errorsaving', 'error');
         }
 
         // send out notifications
         if ($success && !empty($rec['_notify']) && ($rec['attendees'] || $oldrec['attendees'])) {
             // make sure we have the complete record
             $task = $action == 'delete' ? $oldrec : $this->driver->get_task($rec);
 
             // only notify if data really changed (TODO: do diff check on client already)
             if (!$oldrec || $action == 'delete' || self::task_diff($task, $oldrec)) {
                 $sent = $this->notify_attendees($task, $oldrec, $action, $rec['_comment']);
                 if ($sent > 0)
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                 else if ($sent < 0)
                     $this->rc->output->show_message('tasklist.errornotifying', 'error');
             }
         }
 
         if ($success && !empty($rec['_reportpartstat']) && $rec['_reportpartstat'] != 'NEEDS-ACTION') {
             // get the full record after update
             if (!$task) {
                 $task = $this->driver->get_task($rec);
             }
 
             // send iTip REPLY with the updated partstat
             if ($task['organizer'] && ($idx = $this->is_attendee($task)) !== false) {
                 $sender = $task['attendees'][$idx];
                 $status = strtolower($sender['status']);
 
                 if (!empty($_POST['comment']))
                     $task['comment'] = rcube_utils::get_input_value('comment', rcube_utils::INPUT_POST);
 
                 $itip = $this->load_itip();
                 $itip->set_sender_email($sender['email']);
 
                 if ($itip->send_itip_message($this->to_libcal($task), 'REPLY', $task['organizer'], 'itipsubject' . $status, 'itipmailbody' . $status)) {
                     $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $task['organizer']['name'] ?: $task['organizer']['email']))), 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
             }
         }
 
         // unlock client
         $this->rc->output->command('plugin.unlock_saving', $success);
 
         if (!empty($refresh)) {
             if (!empty($refresh['id'])) {
                 $this->encode_task($refresh);
             }
             else if (is_array($refresh)) {
                 foreach ($refresh as $i => $r) {
                     $this->encode_task($refresh[$i]);
                 }
             }
             $this->rc->output->command('plugin.update_task', $refresh);
         }
         else if ($success && ($action == 'delete' || $action == 'undelete')) {
             $this->rc->output->command('plugin.refresh_tagcloud');
         }
     }
 
     /**
      * Load iTIP functions
      */
     private function load_itip()
     {
         if (empty($this->itip)) {
             require_once __DIR__ . '/../libcalendaring/lib/libcalendaring_itip.php';
             $this->itip = new libcalendaring_itip($this, 'tasklist');
             $this->itip->set_rsvp_actions(array('accepted','declined','delegated'));
             $this->itip->set_rsvp_status(array('accepted','tentative','declined','delegated','in-process','completed'));
         }
 
         return $this->itip;
     }
 
     /**
      * repares new/edited task properties before save
      */
     private function prepare_task($rec)
     {
         // try to be smart and extract date from raw input
         if (!empty($rec['raw'])) {
             foreach (array('today','tomorrow','sunday','monday','tuesday','wednesday','thursday','friday','saturday','sun','mon','tue','wed','thu','fri','sat') as $word) {
                 $locwords[] = '/^' . preg_quote(mb_strtolower($this->gettext($word))) . '\b/i';
                 $normwords[] = $word;
                 $datewords[] = $word;
             }
             foreach (array('jan','feb','mar','apr','may','jun','jul','aug','sep','oct','now','dec') as $month) {
                 $locwords[] = '/(' . preg_quote(mb_strtolower($this->gettext('long'.$month))) . '|' . preg_quote(mb_strtolower($this->gettext($month))) . ')\b/i';
                 $normwords[] = $month;
                 $datewords[] = $month;
             }
             foreach (array('on','this','next','at') as $word) {
                 $fillwords[] = preg_quote(mb_strtolower($this->gettext($word)));
                 $fillwords[] = $word;
             }
 
             $raw = trim($rec['raw']);
             $date_str = '';
 
             // translate localized keywords
             $raw = preg_replace('/^(' . join('|', $fillwords) . ')\s*/i', '', $raw);
             $raw = preg_replace($locwords, $normwords, $raw);
 
             // find date pattern
             $date_pattern = '!^(\d+[./-]\s*)?((?:\d+[./-])|' . join('|', $datewords) . ')\.?(\s+\d{4})?[:;,]?\s+!i';
             if (preg_match($date_pattern, $raw, $m)) {
                 $date_str .= $m[1] . $m[2] . $m[3];
                 $raw = preg_replace(array($date_pattern, '/^(' . join('|', $fillwords) . ')\s*/i'), '', $raw);
                 // add year to date string
                 if ($m[1] && !$m[3])
                     $date_str .= date('Y');
             }
 
             // find time pattern
             $time_pattern = '/^(\d+([:.]\d+)?(\s*[hapm.]+)?),?\s+/i';
             if (preg_match($time_pattern, $raw, $m)) {
                 $has_time = true;
                 $date_str .= ($date_str ? ' ' : 'today ') . $m[1];
                 $raw = preg_replace($time_pattern, '', $raw);
             }
 
             // yes, raw input matched a (valid) date
             if (strlen($date_str) && strtotime($date_str) && ($date = new DateTime($date_str, $this->timezone))) {
                 $rec['date'] = $date->format('Y-m-d');
                 if ($has_time)
                     $rec['time'] = $date->format('H:i');
                 $rec['title'] = $raw;
             }
             else
                 $rec['title'] = $rec['raw'];
         }
 
         // normalize input from client
         if (isset($rec['complete'])) {
             $rec['complete'] = floatval($rec['complete']);
             if ($rec['complete'] > 1)
                 $rec['complete'] /= 100;
         }
         if (isset($rec['flagged']))
             $rec['flagged'] = intval($rec['flagged']);
 
         // fix for garbage input
         if ($rec['description'] == 'null')
             $rec['description'] = '';
 
         foreach ($rec as $key => $val) {
             if ($val === 'null')
                 $rec[$key] = null;
         }
 
         if (!empty($rec['date'])) {
             $this->normalize_dates($rec, 'date', 'time');
         }
 
         if (!empty($rec['startdate'])) {
             $this->normalize_dates($rec, 'startdate', 'starttime');
         }
 
         // convert tags to array, filter out empty entries
         if (isset($rec['tags']) && !is_array($rec['tags'])) {
             $rec['tags'] = array_filter((array)$rec['tags']);
         }
 
         // convert the submitted alarm values
         if (!empty($rec['valarms'])) {
             $valarms = array();
             foreach (libcalendaring::from_client_alarms($rec['valarms']) as $alarm) {
                 // alarms can only work with a date (either task start, due or absolute alarm date)
                 if (is_a($alarm['trigger'], 'DateTime') || $rec['date'] || $rec['startdate'])
                     $valarms[] = $alarm;
             }
             $rec['valarms'] = $valarms;
         }
 
         // convert the submitted recurrence settings
         if (isset($rec['recurrence']) && is_array($rec['recurrence'])) {
             $refdate = null;
             if (!empty($rec['date'])) {
                 $refdate = new DateTime($rec['date'] . ' ' . ($rec['time'] ?? ''), $this->timezone);
             }
             else if (!empty($rec['startdate'])) {
                 $refdate = new DateTime($rec['startdate'] . ' ' . ($rec['starttime'] ?? ''), $this->timezone);
             }
 
             if ($refdate) {
                 $rec['recurrence'] = $this->lib->from_client_recurrence($rec['recurrence'], $refdate);
 
                 // translate count into an absolute end date.
                 // why? because when shifting completed tasks to the next occurrence,
                 // the initial start date to count from gets lost.
                 if (!empty($rec['recurrence']['COUNT'])) {
                     $engine = libcalendaring::get_recurrence();
                     $engine->init($rec['recurrence'], $refdate);
                     if ($until = $engine->end()) {
                         $rec['recurrence']['UNTIL'] = $until;
                         unset($rec['recurrence']['COUNT']);
                     }
                 }
             }
             else {  // recurrence requires a reference date
                 $rec['recurrence'] = '';
             }
         }
 
         $handler = new kolab_attachments_handler();
         $rec['attachments'] = $handler->attachments_set(self::SESSION_KEY, $rec['id'], $rec['attachments'] ?? []);
 
         // convert link references into simple URIs
         if (array_key_exists('links', $rec)) {
             $rec['links'] = array_map(function($link) { return is_array($link) ? $link['uri'] : strval($link); }, (array)$rec['links']);
         }
 
         // convert invalid data
         if (isset($rec['attendees']) && !is_array($rec['attendees'])) {
             $rec['attendees'] = array();
         }
 
         if (!empty($rec['attendees'])) {
             foreach ((array) $rec['attendees'] as $i => $attendee) {
                 if (isset($attendee['rsvp']) && is_string($attendee['rsvp'])) {
                     $rec['attendees'][$i]['rsvp'] = $attendee['rsvp'] == 'true' || $attendee['rsvp'] == '1';
                 }
             }
         }
 
         // copy the task status to my attendee partstat
         if (!empty($rec['_reportpartstat'])) {
             if (($idx = $this->is_attendee($rec)) !== false) {
                 if (!($rec['_reportpartstat'] == 'NEEDS-ACTION' && $rec['attendees'][$idx]['status'] == 'ACCEPTED'))
                     $rec['attendees'][$idx]['status'] = $rec['_reportpartstat'];
                 else
                     unset($rec['_reportpartstat']);
             }
         }
 
         // set organizer from identity selector
         if ((isset($rec['_identity']) || (!empty($rec['attendees']) && empty($rec['organizer']))) &&
                 ($identity = $this->rc->user->get_identity($rec['_identity']))) {
             $rec['organizer'] = array('name' => $identity['name'], 'email' => $identity['email']);
         }
 
         if (is_numeric($rec['id']) && $rec['id'] < 0)
             unset($rec['id']);
 
         return $rec;
     }
 
     /**
      * Utility method to convert a tasks date/time values into a normalized format
      */
     private function normalize_dates(&$rec, $date_key, $time_key)
     {
         try {
             // parse date from user format (#2801)
             $date_format = $this->rc->config->get(empty($rec[$time_key]) ? 'date_format' : 'date_long', 'Y-m-d');
             $date = DateTime::createFromFormat($date_format, trim(($rec[$date_key] ?? '') . ' ' . ($rec[$time_key] ?? '')), $this->timezone);
 
             // fall back to default strtotime logic
             if (empty($date)) {
                 $date = new DateTime(($rec[$date_key] ?? '') . ' ' . ($rec[$time_key] ?? ''), $this->timezone);
             }
 
             $rec[$date_key] = $date->format('Y-m-d');
             if (!empty($rec[$time_key])) {
                 $rec[$time_key] = $date->format('H:i');
             }
 
             return true;
         }
         catch (Exception $e) {
             $rec[$date_key] = $rec[$time_key] = null;
         }
 
         return false;
     }
 
     /**
      * Releases some resources after successful save
      */
     private function cleanup_task(&$rec)
     {
         $handler = new kolab_attachments_handler();
         $handler->attachments_cleanup(self::SESSION_KEY);
     }
 
     /**
      * When flagging a recurring task as complete,
      * clone it and shift dates to the next occurrence
      */
     private function handle_recurrence(&$rec, $old)
     {
         $clone = null;
         if ($this->driver->is_complete($rec) && $old && !$this->driver->is_complete($old) && !empty($rec['recurrence'])) {
             $engine = libcalendaring::get_recurrence();
             $rrule = $rec['recurrence'];
             $updates = array();
 
             // compute the next occurrence of date attributes
             foreach (array('date'=>'time', 'startdate'=>'starttime') as $date_key => $time_key) {
                 if (empty($rec[$date_key]))
                     continue;
 
                 $date = new DateTime($rec[$date_key] . ' ' . ($rec[$time_key] ?? ''), $this->timezone);
                 $engine->init($rrule, $date);
                 if ($next = $engine->next_start()) {
                     $updates[$date_key] = $next->format('Y-m-d');
                     if (!empty($rec[$time_key])) {
                         $updates[$time_key] = $next->format('H:i');
                     }
                 }
             }
 
             // shift absolute alarm dates
             if (!empty($updates) && is_array($rec['valarms'])) {
                 $updates['valarms'] = array();
                 unset($rrule['UNTIL'], $rrule['COUNT']);  // make recurrence rule unlimited
 
                 foreach ($rec['valarms'] as $i => $alarm) {
                     if ($alarm['trigger'] instanceof DateTime) {
                         $engine->init($rrule, $alarm['trigger']);
                         if ($next = $engine->next_start()) {
                             $alarm['trigger'] = $next;
                         }
                     }
                     $updates['valarms'][$i] = $alarm;
                 }
             }
 
             if (!empty($updates)) {
                 // clone task to save a completed copy
                 $clone = $rec;
                 $clone['uid'] = $this->generate_uid();
                 $clone['parent_id'] = $rec['id'];
                 unset($clone['id'], $clone['recurrence'], $clone['attachments']);
 
                 // update the task but unset completed flag
                 $rec = array_merge($rec, $updates);
                 $rec['complete'] = $old['complete'];
                 $rec['status'] = $old['status'];
             }
         }
 
         return $clone;
     }
 
     /**
      * Send out an invitation/notification to all task attendees
      */
     private function notify_attendees($task, $old, $action = 'edit', $comment = null)
     {
         if ($action == 'delete' || ($task['status'] == 'CANCELLED' && $old['status'] != $task['status'])) {
             $task['cancelled'] = true;
             $is_cancelled      = true;
         }
 
         $itip   = $this->load_itip();
         $emails = $this->lib->get_user_emails();
         $itip_notify = (int)$this->rc->config->get('calendar_itip_send_option', 3);
 
         // add comment to the iTip attachment
         $task['comment'] = $comment;
 
         // needed to generate VTODO instead of VEVENT entry
         $task['_type'] = 'task';
 
         // compose multipart message using PEAR:Mail_Mime
         $method  = $action == 'delete' ? 'CANCEL' : 'REQUEST';
         $object = $this->to_libcal($task);
         $message = $itip->compose_itip_message($object, $method, $task['sequence'] > $old['sequence']);
 
         // list existing attendees from the $old task
         $old_attendees = array();
         foreach ((array)$old['attendees'] as $attendee) {
             $old_attendees[] = $attendee['email'];
         }
 
         // send to every attendee
         $sent = 0; $current = array();
         foreach ((array)$task['attendees'] as $attendee) {
             $current[] = strtolower($attendee['email']);
 
             // skip myself for obvious reasons
             if (!$attendee['email'] || in_array(strtolower($attendee['email']), $emails)) {
                 continue;
             }
 
             // skip if notification is disabled for this attendee
             if ($attendee['noreply'] && $itip_notify & 2) {
                 continue;
             }
 
             // skip if this attendee has delegated and set RSVP=FALSE
             if ($attendee['status'] == 'DELEGATED' && $attendee['rsvp'] === false) {
                 continue;
             }
 
             // which template to use for mail text
             $is_new   = !in_array($attendee['email'], $old_attendees);
             $is_rsvp  = $is_new || $task['sequence'] > $old['sequence'];
             $bodytext = $is_cancelled ? 'itipcancelmailbody' : ($is_new ? 'invitationmailbody' : 'itipupdatemailbody');
             $subject  = $is_cancelled ? 'itipcancelsubject'  : ($is_new ? 'invitationsubject' : ($task['title'] ? 'itipupdatesubject' : 'itipupdatesubjectempty'));
 
             // finally send the message
             if ($itip->send_itip_message($object, $method, $attendee, $subject, $bodytext, $message, $is_rsvp))
                 $sent++;
             else
                 $sent = -100;
         }
 
         // send CANCEL message to removed attendees
         foreach ((array)$old['attendees'] as $attendee) {
             if (!$attendee['email'] || in_array(strtolower($attendee['email']), $current)) {
                 continue;
             }
 
             $vtodo = $this->to_libcal($old);
             $vtodo['cancelled'] = $is_cancelled;
             $vtodo['attendees'] = array($attendee);
             $vtodo['comment']   = $comment;
 
             if ($itip->send_itip_message($vtodo, 'CANCEL', $attendee, 'itipcancelsubject', 'itipcancelmailbody'))
                 $sent++;
             else
                 $sent = -100;
         }
 
         return $sent;
     }
 
     /**
      * Compare two task objects and return differing properties
      *
      * @param array Event A
      * @param array Event B
      * @return array List of differing task properties
      */
     public static function task_diff($a, $b)
     {
         $diff   = array();
         $ignore = array('changed' => 1, 'attachments' => 1);
 
         foreach (array_unique(array_merge(array_keys($a), array_keys($b))) as $key) {
             if (!$ignore[$key] && $a[$key] != $b[$key])
                 $diff[] = $key;
         }
 
         // only compare number of attachments
         if (count($a['attachments']) != count($b['attachments']))
             $diff[] = 'attachments';
 
         return $diff;
     }
 
     /**
      * Dispatcher for tasklist actions initiated by the client
      */
     public function tasklist_action()
     {
         $action  = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $list    = rcube_utils::get_input_value('l', rcube_utils::INPUT_GPC, true);
         $success = false;
 
         unset($list['_token']);
 
         if (isset($list['showalarms'])) {
             $list['showalarms'] = intval($list['showalarms']);
         }
 
         switch ($action) {
         case 'form-new':
         case 'form-edit':
             $this->load_ui();
             echo $this->ui->tasklist_editform($action, $list);
             exit;
 
         case 'new':
             $list += array('showalarms' => true, 'active' => true, 'editable' => true);
             if ($insert_id = $this->driver->create_list($list)) {
                 $list['id'] = $insert_id;
                 if (empty($list['_reload'])) {
                     $this->load_ui();
                     $list['html'] = $this->ui->tasklist_list_item($insert_id, $list, $jsenv);
                     $list += (array)$jsenv[$insert_id];
                 }
                 $this->rc->output->command('plugin.insert_tasklist', $list);
                 $success = true;
             }
             break;
 
         case 'edit':
             if ($newid = $this->driver->edit_list($list)) {
                 $list['oldid'] = $list['id'];
                 $list['id'] = $newid;
                 $this->rc->output->command('plugin.update_tasklist', $list);
                 $success = true;
             }
             break;
 
         case 'subscribe':
             $success = $this->driver->subscribe_list($list);
             break;
 
         case 'delete':
             if (($success = $this->driver->delete_list($list)))
                 $this->rc->output->command('plugin.destroy_tasklist', $list);
             break;
 
         case 'search':
             $this->load_ui();
             $results = array();
             $query   = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
             $source  = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
 
             foreach ((array)$this->driver->search_lists($query, $source) as $id => $prop) {
                 $editname = $prop['editname'];
                 unset($prop['editname']);  // force full name to be displayed
                 $prop['active'] = false;
 
                 // let the UI generate HTML and CSS representation for this calendar
                 $html = $this->ui->tasklist_list_item($id, $prop, $jsenv);
                 $prop += (array)$jsenv[$id];
                 $prop['editname'] = $editname;
                 $prop['html'] = $html;
 
                 $results[] = $prop;
             }
             // report more results available
             if (!empty($this->driver->search_more_results)) {
                 $this->rc->output->show_message('autocompletemore', 'notice');
             }
 
             $this->rc->output->command('multi_thread_http_response', $results, rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC));
             return;
         }
 
         if ($success) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $this->rc->output->show_message('tasklist.errorsaving', 'error');
         }
 
         $this->rc->output->command('plugin.unlock_saving');
     }
 
     /**
      * Get counts for active tasks divided into different selectors
      */
     public function fetch_counts()
     {
         if (isset($_REQUEST['lists'])) {
             $lists = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);
         }
         else {
             foreach ($this->driver->get_lists() as $list) {
                 if (!empty($list['active'])) {
                     $lists[] = $list['id'];
                 }
             }
         }
         $counts = $this->driver->count_tasks($lists);
         $this->rc->output->command('plugin.update_counts', $counts);
     }
 
     /**
      * Adjust the cached counts after changing a task
      */
     public function update_counts($oldrec, $newrec)
     {
         // rebuild counts until this function is finally implemented
         $this->fetch_counts();
 
         // $this->rc->output->command('plugin.update_counts', $counts);
     }
 
     /**
      *
      */
     public function fetch_tasks()
     {
         $mask   = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $search = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
         $lists  = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);
         $filter = array('mask' => $mask, 'search' => $search);
 
         $data = $this->tasks_data($this->driver->list_tasks($filter, $lists));
 
         $this->rc->output->command('plugin.data_ready', array(
                 'filter' => $mask,
                 'lists'  => $lists,
                 'search' => $search,
                 'data'   => $data,
                 'tags'   => $this->driver->get_tags(),
         ));
     }
 
     /**
      * Handler for printing calendars
      */
     public function print_tasks()
     {
         // Add CSS stylesheets to the page header
         $skin_path = $this->local_skin_path();
 
         $this->include_stylesheet($skin_path . '/print.css');
         $this->include_script('tasklist.js');
 
         $this->rc->output->add_handlers(array(
             'plugin.tasklist_print' => array($this, 'print_tasks_list'),
         ));
 
         $this->rc->output->set_pagetitle($this->gettext('print'));
         $this->rc->output->send('tasklist.print');
     }
 
     /**
      * Handler for printing calendars
      */
     public function print_tasks_list($attrib)
     {
         $mask   = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $search = rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC);
         $lists  = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);
         $filter = array('mask' => $mask, 'search' => $search);
 
         $data = $this->tasks_data($this->driver->list_tasks($filter, $lists));
 
         // we'll build the tasks table in javascript on page load
         // where we have sorting methods, etc.
         $this->rc->output->set_env('tasks', $data);
         $this->rc->output->set_env('filtermask', $mask);
 
         return $this->ui->tasks_resultview($attrib);
     }
 
     /**
      * Prepare and sort the given task records to be sent to the client
      */
     private function tasks_data($records)
     {
         $data = $this->task_tree = $this->task_titles = array();
 
         foreach ($records as $rec) {
             if (!empty($rec['parent_id'])) {
                 $this->task_tree[$rec['id']] = $rec['parent_id'];
             }
 
             $this->encode_task($rec);
 
             $data[] = $rec;
         }
 
         // assign hierarchy level indicators for later sorting
         array_walk($data, array($this, 'task_walk_tree'));
 
         return $data;
     }
 
     /**
      * Prepare the given task record before sending it to the client
      */
     private function encode_task(&$rec)
     {
         $rec['mask']     = $this->filter_mask($rec);
         $rec['flagged']  = intval($rec['flagged'] ?? 0);
         $rec['complete'] = floatval($rec['complete'] ?? 0);
 
         if (!empty($rec['created']) && is_object($rec['created'])) {
             $rec['created_'] = $this->rc->format_date($rec['created']);
             $rec['created'] = $rec['created']->format('U');
         }
         if (!empty($rec['changed']) && is_object($rec['changed'])) {
             $rec['changed_'] = $this->rc->format_date($rec['changed']);
             $rec['changed'] = $rec['changed']->format('U');
         }
         else {
             $rec['changed'] = null;
         }
 
         if (!empty($rec['date'])) {
             try {
                 $date = new DateTime($rec['date'] . ' ' . ($rec['time'] ?? ''), $this->timezone);
                 $rec['datetime'] = intval($date->format('U'));
                 $rec['date'] = $date->format($this->rc->config->get('date_format', 'Y-m-d'));
                 $rec['_hasdate'] = 1;
             }
             catch (Exception $e) {
                 $rec['date'] = $rec['datetime'] = null;
             }
         }
         else {
             $rec['date'] = $rec['datetime'] = null;
             $rec['_hasdate'] = 0;
         }
 
         if (!empty($rec['startdate'])) {
             try {
                 $date = new DateTime($rec['startdate'] . ' ' . ($rec['starttime'] ?? ''), $this->timezone);
                 $rec['startdatetime'] = intval($date->format('U'));
                 $rec['startdate'] = $date->format($this->rc->config->get('date_format', 'Y-m-d'));
             }
             catch (Exception $e) {
                 $rec['startdate'] = $rec['startdatetime'] = null;
             }
         }
 
         if (!empty($rec['valarms'])) {
             $rec['alarms_text'] = libcalendaring::alarms_text($rec['valarms']);
             $rec['valarms'] = libcalendaring::to_client_alarms($rec['valarms']);
         }
 
         if (!empty($rec['recurrence'])) {
             $rec['recurrence_text'] = $this->lib->recurrence_text($rec['recurrence']);
             $rec['recurrence'] = $this->lib->to_client_recurrence($rec['recurrence'], !empty($rec['time']) || !empty($rec['starttime']));
         }
 
         if (!empty($rec['attachments'])) {
             foreach ((array) $rec['attachments'] as $k => $attachment) {
                 $rec['attachments'][$k]['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
                 unset($rec['attachments'][$k]['data']);
             }
         }
 
         // convert link URIs references into structs
         if (array_key_exists('links', $rec)) {
             foreach ((array) $rec['links'] as $i => $link) {
                 if (strpos($link, 'imap://') === 0 && ($msgref = $this->driver->get_message_reference($link, 'task'))) {
                     $rec['links'][$i] = $msgref;
                 }
             }
         }
 
         // Convert HTML description into plain text
         if ($this->is_html($rec)) {
             $h2t = new rcube_html2text($rec['description'], false, true, 0);
             $rec['description'] = $h2t->get_text();
         }
 
         if (!isset($rec['tags']) || !is_array($rec['tags'])) {
             $rec['tags'] = (array) ($rec['tags'] ?? '');
         }
 
         sort($rec['tags'], SORT_LOCALE_STRING);
 
         if (in_array($rec['id'], $this->collapsed_tasks)) {
             $rec['collapsed'] = true;
         }
 
         if (empty($rec['parent_id'])) {
             $rec['parent_id'] = null;
         }
 
         $this->task_titles[$rec['id']] = $rec['title'] ?? '';
     }
 
     /**
      * Determine whether the given task description is HTML formatted
      */
     private function is_html($task)
     {
         // check for opening and closing <html> or <body> tags
         return isset($task['description'])
             && preg_match('/<(html|body)(\s+[a-z]|>)/', $task['description'], $m)
             && strpos($task['description'], '</' . $m[1] . '>') > 0;
     }
 
     /**
      * Callback function for array_walk over all tasks.
      * Sets tree depth and parent titles
      */
     private function task_walk_tree(&$rec)
     {
         $rec['_depth'] = 0;
         $parent_titles = array();
         $parent_id = isset($this->task_tree[$rec['id']]) ? $this->task_tree[$rec['id']] : null;
         while ($parent_id) {
             $rec['_depth']++;
             if (isset($this->task_titles[$parent_id])) {
                 array_unshift($parent_titles, $this->task_titles[$parent_id]);
             }
             $parent_id = isset($this->task_tree[$parent_id]) ? $this->task_tree[$parent_id] : null;
         }
 
         if (count($parent_titles)) {
             $rec['parent_title'] = join(' ยป ', array_filter($parent_titles));
         }
     }
 
     /**
      * Compute the filter mask of the given task
      *
      * @param array Hash array with Task record properties
      * @return int Filter mask
      */
     public function filter_mask($rec)
     {
         static $today, $today_date, $tomorrow, $weeklimit;
 
         if (!$today) {
             $today_date    = new libcalendaring_datetime('now', $this->timezone);
             $today         = $today_date->format('Y-m-d');
             $tomorrow_date = new libcalendaring_datetime('now + 1 day', $this->timezone);
             $tomorrow      = $tomorrow_date->format('Y-m-d');
 
             // In Kolab-mode we hide "Next 7 days" filter, which means
             // "Later" should catch tasks with date after tomorrow (#5353)
             if ($this->rc->output->get_env('tasklist_driver') == 'kolab') {
                 $weeklimit = $tomorrow;
             }
             else {
                 $week_date = new DateTime('now + 7 days', $this->timezone);
                 $weeklimit = $week_date->format('Y-m-d');
             }
         }
 
         $mask    = 0;
         $start   = !empty($rec['startdate']) ? $rec['startdate'] : '1900-00-00';
         $duedate = !empty($rec['date']) ? $rec['date'] : '3000-00-00';
 
         if (!empty($rec['flagged'])) {
             $mask |= self::FILTER_MASK_FLAGGED;
         }
         if ($this->driver->is_complete($rec)) {
             $mask |= self::FILTER_MASK_COMPLETE;
         }
 
         if (empty($rec['date'])) {
             $mask |= self::FILTER_MASK_NODATE;
         }
         else if ($rec['date'] < $today) {
             $mask |= self::FILTER_MASK_OVERDUE;
         }
 
         if (empty($rec['recurrence']) || $duedate < $today || $start > $weeklimit) {
             if ($duedate <= $today || (!empty($rec['startdate']) && $start <= $today))
                 $mask |= self::FILTER_MASK_TODAY;
             else if (($start > $today && $start <= $tomorrow) || ($duedate > $today && $duedate <= $tomorrow))
                 $mask |= self::FILTER_MASK_TOMORROW;
             else if (($start > $tomorrow && $start <= $weeklimit) || ($duedate > $tomorrow && $duedate <= $weeklimit))
                 $mask |= self::FILTER_MASK_WEEK;
             else if ($start > $weeklimit || $duedate > $weeklimit)
                 $mask |= self::FILTER_MASK_LATER;
         }
         else if (!empty($rec['startdate']) || !empty($rec['date'])) {
             $date = new libcalendaring_datetime(!empty($rec['startdate']) ? $rec['startdate'] : $rec['date'], $this->timezone);
 
             // set safe recurrence start
             while ($date->format('Y-m-d') >= $today) {
                 switch ($rec['recurrence']['FREQ']) {
                     case 'DAILY':
                         $date = clone $today_date;
                         $date->sub(new DateInterval('P1D'));
                         break;
                     case 'WEEKLY': $date->sub(new DateInterval('P7D')); break;
                     case 'MONTHLY': $date->sub(new DateInterval('P1M')); break;
                     case 'YEARLY': $date->sub(new DateInterval('P1Y')); break;
                     default; break 2;
                 }
             }
 
             $date->_dateonly = true;
 
             $engine = libcalendaring::get_recurrence();
             $engine->init($rec['recurrence'], $date);
 
             // check task occurrences (stop next week)
             // FIXME: is there a faster way of doing this?
             while ($date = $engine->next_start()) {
                 $date = $date->format('Y-m-d');
 
                 // break iteration asap
                 if ($date > $duedate || ($mask & self::FILTER_MASK_LATER)) {
                     break;
                 }
 
                 if ($date == $today) {
                     $mask |= self::FILTER_MASK_TODAY;
                 }
                 else if ($date == $tomorrow) {
                     $mask |= self::FILTER_MASK_TOMORROW;
                 }
                 else if ($date > $tomorrow && $date <= $weeklimit) {
                     $mask |= self::FILTER_MASK_WEEK;
                 }
                 else if ($date > $weeklimit) {
                     $mask |= self::FILTER_MASK_LATER;
                     break;
                 }
             }
         }
 
         // add masks for assigned tasks
         if ($this->is_organizer($rec) && !empty($rec['attendees']) && $this->is_attendee($rec) === false) {
             $mask |= self::FILTER_MASK_ASSIGNED;
         }
         else if (/*empty($rec['attendees']) ||*/ $this->is_attendee($rec) !== false) {
             $mask |= self::FILTER_MASK_MYTASKS;
         }
 
         return $mask;
     }
 
     /**
      * Determine whether the current user is an attendee of the given task
      */
     public function is_attendee($task)
     {
         $emails = $this->lib->get_user_emails();
         foreach ((array) ($task['attendees'] ?? []) as $i => $attendee) {
             if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                 return $i;
             }
         }
 
         return false;
     }
 
     /**
      * Determine whether the current user is the organizer of the given task
      */
     public function is_organizer($task)
     {
         $emails = $this->lib->get_user_emails();
         return (empty($task['organizer']) || in_array(strtolower($task['organizer']['email']), $emails));
     }
 
 
     /*******  UI functions  ********/
 
     /**
      * Render main view of the tasklist task
      */
     public function tasklist_view()
     {
         $this->ui->init();
         $this->ui->init_templates();
 
         // set autocompletion env
         $this->rc->output->set_env('autocomplete_threads', (int)$this->rc->config->get('autocomplete_threads', 0));
         $this->rc->output->set_env('autocomplete_max', (int)$this->rc->config->get('autocomplete_max', 15));
         $this->rc->output->set_env('autocomplete_min_length', $this->rc->config->get('autocomplete_min_length'));
         $this->rc->output->add_label('autocompletechars', 'autocompletemore', 'delete', 'close');
 
         $this->rc->output->set_pagetitle($this->gettext('navtitle'));
         $this->rc->output->send('tasklist.mainview');
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for updated data in active lists and sync them to the client
      */
     public function refresh($attr)
     {
         // refresh the entire list every 10th time to also sync deleted items
         if (rand(0,10) == 10) {
             $this->rc->output->command('plugin.reload_data');
             return;
         }
 
         $filter = array(
             'since'  => $attr['last'],
             'search' => rcube_utils::get_input_value('q', rcube_utils::INPUT_GPC),
             'mask'   => intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC)) & self::FILTER_MASK_COMPLETE,
         );
         $lists = rcube_utils::get_input_value('lists', rcube_utils::INPUT_GPC);;
 
         $updates = $this->driver->list_tasks($filter, $lists);
         if (!empty($updates)) {
             $this->rc->output->command('plugin.refresh_tasks', $this->tasks_data($updates), true);
 
             // update counts
             $counts = $this->driver->count_tasks($lists);
             $this->rc->output->command('plugin.update_counts', $counts);
         }
     }
 
     /**
      * Handler for pending_alarms plugin hook triggered by the calendar module on keep-alive requests.
      * This will check for pending notifications and pass them to the client
      */
     public function pending_alarms($p)
     {
         $this->load_driver();
         if ($alarms = $this->driver->pending_alarms($p['time'] ?: time())) {
             foreach ($alarms as $alarm) {
                 // encode alarm object to suit the expectations of the calendaring code
                 if ($alarm['date'])
                     $alarm['start'] = new DateTime($alarm['date'].' '.$alarm['time'], $this->timezone);
 
                 $alarm['id'] = 'task:' . $alarm['id'];  // prefix ID with task:
                 $alarm['allday'] = empty($alarm['time']) ? 1 : 0;
                 $p['alarms'][] = $alarm;
             }
         }
 
         return $p;
     }
 
     /**
      * Handler for alarm dismiss hook triggered by the calendar module
      */
     public function dismiss_alarms($p)
     {
         $this->load_driver();
         foreach ((array)$p['ids'] as $id) {
             if (strpos($id, 'task:') === 0)
                 $p['success'] |= $this->driver->dismiss_alarm(substr($id, 5), $p['snooze']);
         }
 
         return $p;
     }
 
     /**
      * Handler for importing .ics files
      */
     function import_tasks()
     {
         // Upload progress update
         if (!empty($_GET['_progress'])) {
             $this->rc->upload_progress();
         }
 
         @set_time_limit(0);
 
         // process uploaded file if there is no error
         $err = $_FILES['_data']['error'];
 
         if (!$err && $_FILES['_data']['tmp_name']) {
             $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
             $lists  = $this->driver->get_lists();
             $list   = $lists[$source] ?: $this->get_default_tasklist();
             $source = $list['id'];
 
             // extract zip file
             if ($_FILES['_data']['type'] == 'application/zip') {
                 $count = 0;
                 if (class_exists('ZipArchive', false)) {
                     $zip = new ZipArchive();
                     if ($zip->open($_FILES['_data']['tmp_name'])) {
                         $randname = uniqid('zip-' . session_id(), true);
                         $tmpdir   = slashify($this->rc->config->get('temp_dir', sys_get_temp_dir())) . $randname;
                         mkdir($tmpdir, 0700);
 
                         // extract each ical file from the archive and import it
                         for ($i = 0; $i < $zip->numFiles; $i++) { 
                             $filename = $zip->getNameIndex($i);
                             if (preg_match('/\.ics$/i', $filename)) {
                                 $tmpfile = $tmpdir . '/' . basename($filename);
                                 if (copy('zip://' . $_FILES['_data']['tmp_name'] . '#'.$filename, $tmpfile)) {
                                     $count += $this->import_from_file($tmpfile, $source, $errors);
                                     unlink($tmpfile);
                                 }
                             }
                         }
 
                         rmdir($tmpdir);
                         $zip->close();
                     }
                     else {
                         $errors = 1;
                         $msg = 'Failed to open zip file.';
                     }
                 }
                 else {
                     $errors = 1;
                     $msg = 'Zip files are not supported for import.';
                 }
             }
             else {
                 // attempt to import the uploaded file directly
                 $count = $this->import_from_file($_FILES['_data']['tmp_name'], $source, $errors);
             }
 
             if ($count) {
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'importsuccess', 'vars' => array('nr' => $count))), 'confirmation');
                 $this->rc->output->command('plugin.import_success', array('source' => $source, 'refetch' => true));
             }
             else if (!$errors) {
                 $this->rc->output->command('display_message', $this->gettext('importnone'), 'notice');
                 $this->rc->output->command('plugin.import_success', array('source' => $source));
             }
             else {
                 $this->rc->output->command('plugin.import_error', array('message' => $this->gettext('importerror') . ($msg ? ': ' . $msg : '')));
             }
         }
         else {
             if ($err == UPLOAD_ERR_INI_SIZE || $err == UPLOAD_ERR_FORM_SIZE) {
                 $msg = $this->rc->gettext(array('name' => 'filesizeerror', 'vars' => array(
                     'size' => $this->rc->show_bytes(parse_bytes(ini_get('upload_max_filesize'))))));
             }
             else {
                 $msg = $this->rc->gettext('fileuploaderror');
             }
 
             $this->rc->output->command('plugin.import_error', array('message' => $msg));
         }
 
         $this->rc->output->send('iframe');
     }
 
     /**
      * Helper function to parse and import a single .ics file
      */
     private function import_from_file($filepath, $source, &$errors)
     {
         $user_email = $this->rc->user->get_username();
         $ical       = $this->get_ical();
         $errors     = !$ical->fopen($filepath);
         $count      = $i = 0;
 
         foreach ($ical as $task) {
             // keep the browser connection alive on long import jobs
             if (++$i > 100 && $i % 100 == 0) {
                 echo "<!-- -->";
                 ob_flush();
             }
 
             if ($task['_type'] == 'task') {
                 $task['list'] = $source;
 
                 if ($this->driver->create_task($task)) {
                     $count++;
                 }
                 else {
                     $errors++;
                 }
             }
         }
 
         return $count;
     }
 
     /**
      * Construct the ics file for exporting tasks to iCalendar format
      */
     function export_tasks()
     {
         $source      = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
         $task_id     = rcube_utils::get_input_value('id', rcube_utils::INPUT_GPC);
         $attachments = (bool) rcube_utils::get_input_value('attachments', rcube_utils::INPUT_GPC);
 
         $this->load_driver();
 
         $browser = new rcube_browser;
         $lists   = $this->driver->get_lists();
         $tasks   = array();
         $filter  = array();
 
         // get message UIDs for filter
         if ($source && ($list = $lists[$source])) {
             $filename = html_entity_decode($list['name']) ?: $sorce;
             $filter   = array($source => true);
         }
         else if ($task_id) {
             $filename = 'tasks';
             foreach (explode(',', $task_id) as $id) {
                 list($list_id, $task_id) = explode(':', $id, 2);
                 if ($list_id && $task_id) {
                     $filter[$list_id][] = $task_id;
                 }
             }
         }
 
         // Get tasks
         foreach ($filter as $list_id => $uids) {
             $_filter = is_array($uids) ? array('uid' => $uids) : null;
             $_tasks  = $this->driver->list_tasks($_filter, $list_id);
             if (!empty($_tasks)) {
                 $tasks = array_merge($tasks, $_tasks);
             }
         }
 
         // Set file name
         if ($source && count($tasks) == 1) {
             $filename = $tasks[0]['title'] ?: 'task';
         }
         $filename .= '.ics';
         $filename = $browser->ie ? rawurlencode($filename) : addcslashes($filename, '"');
 
         $tasks = array_map(array($this, 'to_libcal'), $tasks);
 
         // Give plugins a possibility to implement other output formats or modify the result
         $plugin = $this->rc->plugins->exec_hook('tasks_export', array(
                 'result'      => $tasks,
                 'attachments' => $attachments,
                 'filename'    => $filename,
                 'plugin'      => $this,
         ));
 
         if ($plugin['abort']) {
             exit;
         }
 
         $this->rc->output->nocacheing_headers();
 
         // don't kill the connection if download takes more than 30 sec.
         @set_time_limit(0);
         header("Content-Type: text/calendar");
         header("Content-Disposition: inline; filename=\"". $plugin['filename'] ."\"");
 
         $this->get_ical()->export($plugin['result'], '', true,
             !empty($plugin['attachments']) ? array($this->driver, 'get_attachment_body') : null);
         exit;
     }
 
 
     /******* Attachment handling  *******/
 
     /**
      * Handler for attachments upload
     */
     public function attachment_upload()
     {
         $handler = new kolab_attachments_handler();
         $handler->attachment_upload(self::SESSION_KEY);
     }
 
     /**
      * Handler for attachments download/displaying
      */
     public function attachment_get()
     {
         $handler = new kolab_attachments_handler();
 
         // show loading page
         if (!empty($_GET['_preload'])) {
             return $handler->attachment_loading_page();
         }
 
         $task = rcube_utils::get_input_value('_t', rcube_utils::INPUT_GPC);
         $list = rcube_utils::get_input_value('_list', rcube_utils::INPUT_GPC);
         $id   = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
         $rev  = rcube_utils::get_input_value('_rev', rcube_utils::INPUT_GPC);
 
         $task       = ['id' => $task, 'list' => $list, 'rev' => $rev];
         $attachment = $this->driver->get_attachment($id, $task);
 
         // show part page
         if (!empty($_GET['_frame'])) {
             $handler->attachment_page($attachment);
         }
         // deliver attachment content
         else if ($attachment) {
             if (empty($attachment['body'])) {
                 $attachment['body'] = $this->driver->get_attachment_body($id, $task);
             }
             $handler->attachment_get($attachment);
         }
 
         // if we arrive here, the requested part was not found
         header('HTTP/1.1 404 Not Found');
         exit;
     }
 
 
     /*******  Email related function *******/
 
     public function mail_message2task()
     {
         $this->load_ui();
         $this->ui->init();
         $this->ui->init_templates();
         $this->ui->tasklists();
 
         $uid  = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GET);
         $mbox = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_GET);
         $task = array();
 
         $imap    = $this->rc->get_storage();
         $message = new rcube_message($uid, $mbox);
 
         if ($message->headers) {
             $task['title']       = trim($message->subject);
             $task['description'] = trim($message->first_text_part());
             $task['id']          = -$uid;
 
             $this->load_driver();
 
             // add a reference to the email message
             if ($msgref = $this->driver->get_message_reference($message->headers, $mbox)) {
                 $task['links'] = array($msgref);
             }
             // copy mail attachments to task
             else if (!empty($message->attachments) && $this->driver->attachments) {
                 $handler = new kolab_attachments_handler();
                 $task['attachments'] = $handler->copy_mail_attachments(self::SESSION_KEY, $task['id'], $message);
             }
 
             $this->rc->output->set_env('task_prop', $task);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
         }
 
         $this->rc->output->send('tasklist.dialog');
     }
 
     /**
      * Add UI element to copy task invitations or updates to the tasklist
      */
     public function mail_messagebody_html($p)
     {
         // load iCalendar functions (if necessary)
         if (!empty($this->lib->ical_parts)) {
             $this->get_ical();
             $this->load_itip();
         }
 
         $html = '';
         $has_tasks = false;
         $ical_objects = $this->lib->get_mail_ical_objects();
 
         // show a box for every task in the file
         foreach ($ical_objects as $idx => $task) {
             if ($task['_type'] != 'task') {
                 continue;
             }
 
             $has_tasks = true;
 
             // get prepared inline UI for this event object
             if ($ical_objects->method) {
                 $html .= html::div('tasklist-invitebox invitebox boxinformation',
                     $this->itip->mail_itip_inline_ui(
                         $task,
                         $ical_objects->method,
                         $ical_objects->mime_id . ':' . $idx,
                         'tasks',
                         rcube_utils::anytodatetime($ical_objects->message_date)
                     )
                 );
             }
 
             // limit listing
             if ($idx >= 3) {
                 break;
             }
         }
 
         // list linked tasks
         $links = array();
         foreach ($this->message_tasks as $task) {
             $checkbox = new html_checkbox(array(
                 'name' => 'completed',
                 'class' => 'complete pretty-checkbox',
                 'title' => $this->gettext('complete'),
                 'data-list' => $task['list'],
             ));
             $complete = $this->driver->is_complete($task);
             $links[] = html::tag('li', 'messagetaskref' . ($complete ? ' complete' : ''),
                 $checkbox->show($complete ? $task['id'] : null, array('value' => $task['id'])) . ' ' .
                 html::a(array(
                     'href' => $this->rc->url(array(
                         'task' => 'tasks',
                         'list' => $task['list'],
                         'id' => $task['id'],
                     )),
                     'class' => 'messagetasklink',
                     'rel' => $task['id'] . '@' . $task['list'],
                     'target' => '_blank',
                 ), rcube::Q($task['title']))
             );
         }
         if (count($links)) {
             $html .= html::div('messagetasklinks boxinformation', html::tag('ul', 'tasklist', join("\n", $links)));
         }
 
         // prepend iTip/relation boxes to message body
         if ($html) {
             $this->load_ui();
             $this->ui->init();
 
             $p['content'] = $html . $p['content'];
 
             $this->rc->output->add_label('tasklist.savingdata','tasklist.deletetaskconfirm','tasklist.declinedeleteconfirm');
         }
 
         // add "Save to tasks" button into attachment menu
         if ($has_tasks) {
             $this->add_button(array(
                 'id'         => 'attachmentsavetask',
                 'name'       => 'attachmentsavetask',
                 'type'       => 'link',
                 'wrapper'    => 'li',
                 'command'    => 'attachment-save-task',
                 'class'      => 'icon tasklistlink disabled',
                 'classact'   => 'icon tasklistlink active',
                 'innerclass' => 'icon taskadd',
                 'label'      => 'tasklist.savetotasklist',
             ), 'attachmentmenu');
         }
 
         return $p;
     }
 
     /**
      * Lookup backend storage and find notes associated with the given message
      */
     public function mail_message_load($p)
     {
         if (empty($p['object']->headers->others['x-kolab-type'])) {
             $this->load_driver();
             $this->message_tasks = $this->driver->get_message_related_tasks($p['object']->headers, $p['object']->folder);
 
             // sort message tasks by completeness and due date
             $driver = $this->driver;
             array_walk($this->message_tasks, array($this, 'encode_task'));
             usort($this->message_tasks, function($a, $b) use ($driver) {
                 $a_complete = intval($driver->is_complete($a));
                 $b_complete = intval($driver->is_complete($b));
                 $d = $a_complete - $b_complete;
                 if (!$d) $d = $b['_hasdate'] - $a['_hasdate'];
                 if (!$d) $d = $a['datetime'] - $b['datetime'];
                 return $d;
             });
         }
     }
 
     /**
      * Load iCalendar functions
      */
     public function get_ical()
     {
         if (empty($this->ical)) {
             $this->ical = libcalendaring::get_ical();
         }
 
         return $this->ical;
     }
 
     /**
      * Get properties of the tasklist this user has specified as default
      */
     public function get_default_tasklist($lists = null)
     {
         if ($lists === null) {
             $lists = $this->driver->get_lists(tasklist_driver::FILTER_PERSONAL | tasklist_driver::FILTER_WRITEABLE);
         }
 
         $list = null;
 
         foreach ($lists as $l) {
             if ($l['default']) {
                 $list = $l;
             }
 
             if ($l['editable']) {
                 $first = $l;
             }
         }
 
         return $list ?: $first;
     }
 
     /**
      * Import the full payload from a mail message attachment
      */
     public function mail_import_attachment()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             $part    = $imap->get_message_part($uid, $mime_id);
 //            $headers = $imap->get_message_headers($uid);
 
             if ($part->ctype_parameters['charset']) {
                 $charset = $part->ctype_parameters['charset'];
             }
 
             if ($part) {
                 $tasks = $this->get_ical()->import($part, $charset);
             }
         }
 
         $success = $existing = 0;
 
         if (!empty($tasks)) {
             // find writeable tasklist to store task
             $cal_id = !empty($_REQUEST['_list']) ? rcube_utils::get_input_value('_list', rcube_utils::INPUT_POST) : null;
             $lists  = $this->driver->get_lists();
 
             foreach ($tasks as $task) {
                 // save to tasklist
                 $list   = $lists[$cal_id] ?: $this->get_default_tasklist();
                 if ($list && $list['editable'] && $task['_type'] == 'task') {
                     $task = $this->from_ical($task);
                     $task['list'] = $list['id'];
 
                     if (!$this->driver->get_task($task['uid'])) {
                         $success += (bool) $this->driver->create_task($task);
                     }
                     else {
                         $existing++;
                     }
                 }
             }
         }
 
         if ($success) {
             $this->rc->output->command('display_message', $this->gettext(array(
                 'name' => 'importsuccess',
                 'vars' => array('nr' => $success),
             )), 'confirmation');
         }
         else if ($existing) {
             $this->rc->output->command('display_message', $this->gettext('importwarningexists'), 'warning');
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('errorimportingtask'), 'error');
         }
     }
 
     /**
      * Handler for POST request to import an event attached to a mail message
      */
     public function mail_import_itip()
     {
         $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
         $status  = rcube_utils::get_input_value('_status', rcube_utils::INPUT_POST);
         $comment = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
         $delete  = intval(rcube_utils::get_input_value('_del', rcube_utils::INPUT_POST));
         $noreply = intval(rcube_utils::get_input_value('_noreply', rcube_utils::INPUT_POST)) || $status == 'needs-action';
 
         $error_msg = $this->gettext('errorimportingtask');
         $success   = false;
 
         if ($status == 'delegated') {
             $delegates = rcube_mime::decode_address_list(rcube_utils::get_input_value('_to', rcube_utils::INPUT_POST, true), 1, false);
             $delegate  = reset($delegates);
 
             if (empty($delegate) || empty($delegate['mailto'])) {
                 $this->rc->output->command('display_message', $this->gettext('libcalendaring.delegateinvalidaddress'), 'error');
                 return;
             }
         }
 
         // successfully parsed tasks?
         if ($task = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'task')) {
             $task = $this->from_ical($task);
 
             // forward iTip request to delegatee
             if ($delegate) {
                 $rsvpme = rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST);
                 $itip   = $this->load_itip();
 
                 $task['comment'] = $comment;
 
                 if ($itip->delegate_to($task, $delegate, !empty($rsvpme))) {
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
 
                 unset($task['comment']);
             }
 
             $mode = tasklist_driver::FILTER_PERSONAL
                 | tasklist_driver::FILTER_SHARED
                 | tasklist_driver::FILTER_WRITEABLE;
 
             // find writeable list to store the task
             $list_id = !empty($_REQUEST['_folder']) ? rcube_utils::get_input_value('_folder', rcube_utils::INPUT_POST) : null;
             $lists   = $this->driver->get_lists($mode);
             $list    = $lists[$list_id];
             $dontsave = ($_REQUEST['_folder'] === '' && $task['_method'] == 'REQUEST');
 
             // select default list except user explicitly selected 'none'
             if (!$list && !$dontsave) {
                 $list = $this->get_default_tasklist($lists);
             }
 
             $metadata = array(
                 'uid'      => $task['uid'],
                 'changed'  => is_object($task['changed']) ? $task['changed']->format('U') : 0,
                 'sequence' => intval($task['sequence']),
                 'fallback' => strtoupper($status),
                 'method'   => $task['_method'],
                 'task'     => 'tasks',
             );
 
             // update my attendee status according to submitted method
             if (!empty($status)) {
                 $organizer = $task['organizer'];
                 $emails    = $this->lib->get_user_emails();
 
                 foreach ($task['attendees'] as $i => $attendee) {
                     if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                         $metadata['attendee'] = $attendee['email'];
                         $metadata['rsvp']     = $attendee['role'] != 'NON-PARTICIPANT';
                         $reply_sender         = $attendee['email'];
 
                         $task['attendees'][$i]['status'] = strtoupper($status);
                         if (!in_array($task['attendees'][$i]['status'], array('NEEDS-ACTION','DELEGATED'))) {
                             $task['attendees'][$i]['rsvp'] = false;  // unset RSVP attribute
                         }
                     }
                 }
 
                 // add attendee with this user's default identity if not listed
                 if (!$reply_sender) {
                     $sender_identity = $this->rc->user->list_emails(true);
                     $task['attendees'][] = array(
                         'name'   => $sender_identity['name'],
                         'email'  => $sender_identity['email'],
                         'role'   => 'OPT-PARTICIPANT',
                         'status' => strtoupper($status),
                     );
                     $metadata['attendee'] = $sender_identity['email'];
                 }
             }
 
             // save to tasklist
             if ($list && $list['editable']) {
                 $task['list'] = $list['id'];
 
                 // check for existing task with the same UID
                 $existing = $this->find_task($task['uid'], $mode);
 
                 if ($existing) {
                     // only update attendee status
                     if ($task['_method'] == 'REPLY') {
                         // try to identify the attendee using the email sender address
                         $existing_attendee = -1;
                         $existing_attendee_emails = array();
                         foreach ($existing['attendees'] as $i => $attendee) {
                             $existing_attendee_emails[] = $attendee['email'];
                             if ($task['_sender'] && ($attendee['email'] == $task['_sender'] || $attendee['email'] == $task['_sender_utf'])) {
                                 $existing_attendee = $i;
                             }
                         }
 
                         $task_attendee = null;
                         foreach ($task['attendees'] as $attendee) {
                             if ($task['_sender'] && ($attendee['email'] == $task['_sender'] || $attendee['email'] == $task['_sender_utf'])) {
                                 $task_attendee        = $attendee;
                                 $metadata['fallback'] = $attendee['status'];
                                 $metadata['attendee'] = $attendee['email'];
                                 $metadata['rsvp']     = $attendee['rsvp'] || $attendee['role'] != 'NON-PARTICIPANT';
                                 if ($attendee['status'] != 'DELEGATED') {
                                     break;
                                 }
                             }
                             // also copy delegate attendee
                             else if (!empty($attendee['delegated-from']) &&
                                      (stripos($attendee['delegated-from'], $task['_sender']) !== false || stripos($attendee['delegated-from'], $task['_sender_utf']) !== false) &&
                                      (!in_array($attendee['email'], $existing_attendee_emails))) {
                                 $existing['attendees'][] = $attendee;
                             }
                         }
 
                         // if delegatee has declined, set delegator's RSVP=True
                         if ($task_attendee && $task_attendee['status'] == 'DECLINED' && $task_attendee['delegated-from']) {
                             foreach ($existing['attendees'] as $i => $attendee) {
                                 if ($attendee['email'] == $task_attendee['delegated-from']) {
                                     $existing['attendees'][$i]['rsvp'] = true;
                                     break;
                                 }
                             }
                         }
 
                         // found matching attendee entry in both existing and new events
                         if ($existing_attendee >= 0 && $task_attendee) {
                             $existing['attendees'][$existing_attendee] = $task_attendee;
                             $success = $this->driver->edit_task($existing);
                         }
                         // update the entire attendees block
                         else if (($task['sequence'] >= $existing['sequence'] || $task['changed'] >= $existing['changed']) && $task_attendee) {
                             $existing['attendees'][] = $task_attendee;
                             $success = $this->driver->edit_task($existing);
                         }
                         else {
                             $error_msg = $this->gettext('newerversionexists');
                         }
                     }
                     // delete the task when declined
                     else if ($status == 'declined' && $delete) {
                         $deleted = $this->driver->delete_task($existing, true);
                         $success = true;
                     }
                     // import the (newer) task
                     else if ($task['sequence'] >= $existing['sequence'] || $task['changed'] >= $existing['changed']) {
                         $task['id']   = $existing['id'];
                         $task['list'] = $existing['list'];
 
                         // preserve my participant status for regular updates
                         if (empty($status)) {
                             $this->lib->merge_attendees($task, $existing);
                         }
 
                         // set status=CANCELLED on CANCEL messages
                         if ($task['_method'] == 'CANCEL') {
                             $task['status'] = 'CANCELLED';
                         }
 
                         // update attachments list, allow attachments update only on REQUEST (#5342)
                         if ($task['_method'] == 'REQUEST') {
                             $task['deleted_attachments'] = true;
                         }
                         else {
                             unset($task['attachments']);
                         }
 
                         // show me as free when declined (#1670)
                         if ($status == 'declined' || $task['status'] == 'CANCELLED') {
                             $task['free_busy'] = 'free';
                         }
 
                         $success = $this->driver->edit_task($task);
                     }
                     else if (!empty($status)) {
                         $existing['attendees'] = $task['attendees'];
                         if ($status == 'declined') { // show me as free when declined (#1670)
                             $existing['free_busy'] = 'free';
                         }
 
                         $success = $this->driver->edit_event($existing);
                     }
                     else {
                         $error_msg = $this->gettext('newerversionexists');
                     }
                 }
                 else if (!$existing && ($status != 'declined' || $this->rc->config->get('kolab_invitation_tasklists'))) {
                     $success = $this->driver->create_task($task);
                 }
                 else if ($status == 'declined') {
                     $error_msg = null;
                 }
             }
             else if ($status == 'declined' || $dontsave) {
                 $error_msg = null;
             }
             else {
                 $error_msg = $this->gettext('nowritetasklistfound');
             }
         }
 
         if ($success || $dontsave) {
             if ($success) {
                 $message = $task['_method'] == 'REPLY' ? 'attendeupdateesuccess' : ($deleted ? 'successremoval' : ($existing ? 'updatedsuccessfully' : 'importedsuccessfully'));
                 $this->rc->output->command('display_message', $this->gettext(array('name' => $message, 'vars' => array('list' => $list['name']))), 'confirmation');
             }
 
             $metadata['rsvp']         = intval($metadata['rsvp']);
             $metadata['after_action'] = $this->rc->config->get('calendar_itip_after_action', 0);
 
             $this->rc->output->command('plugin.itip_message_processed', $metadata);
             $error_msg = null;
         }
         else if ($error_msg) {
             $this->rc->output->command('display_message', $error_msg, 'error');
         }
 
         // send iTip reply
         if ($task['_method'] == 'REQUEST' && $organizer && !$noreply && !in_array(strtolower($organizer['email']), $emails) && !$error_msg) {
             $task['comment'] = $comment;
             $itip = $this->load_itip();
             $itip->set_sender_email($reply_sender);
 
             if ($itip->send_itip_message($this->to_libcal($task), 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status))
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $organizer['name'] ?: $organizer['email']))), 'confirmation');
             else
                 $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
         }
 
         $this->rc->output->send();
     }
 
 
     /****  Task invitation plugin hooks ****/
 
     /**
      * Handler for task/itip-delegate requests
      */
     function mail_itip_delegate()
     {
         // forward request to mail_import_itip() with the right status
         $_POST['_status'] = $_REQUEST['_status'] = 'delegated';
         $this->mail_import_itip();
     }
 
     /**
      * Find a task in user tasklists
      */
     protected function find_task($task, &$mode)
     {
         $this->load_driver();
 
         // We search for writeable folders in personal namespace by default
         $mode   = tasklist_driver::FILTER_WRITEABLE | tasklist_driver::FILTER_PERSONAL;
         $result = $this->driver->get_task($task, $mode);
 
         // ... now check shared folders if not found
         if (!$result) {
             $result = $this->driver->get_task($task, tasklist_driver::FILTER_WRITEABLE | tasklist_driver::FILTER_SHARED);
             if ($result) {
                 $mode |= tasklist_driver::FILTER_SHARED;
             }
         }
 
         return $result;
     }
 
     /**
      * Handler for task/itip-status requests
      */
     public function task_itip_status()
     {
         $data = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         // find local copy of the referenced task
         $existing  = $this->find_task($data, $mode);
         $is_shared = $mode & tasklist_driver::FILTER_SHARED;
         $itip      = $this->load_itip();
         $response  = $itip->get_itip_status($data, $existing);
 
         // get a list of writeable lists to save new tasks to
         if ((!$existing || $is_shared) && $response['action'] == 'rsvp' || $response['action'] == 'import') {
             $lists  = $this->driver->get_lists($mode);
             $select = new html_select(array('name' => 'tasklist', 'id' => 'itip-saveto', 'is_escaped' => true, 'class' => 'form-control'));
             $select->add('--', '');
 
             foreach ($lists as $list) {
                 if ($list['editable']) {
                     $select->add($list['name'], $list['id']);
                 }
             }
         }
 
         if ($select) {
             $default_list = $this->get_default_tasklist($lists);
             $response['select'] = html::span('folder-select', $this->gettext('saveintasklist') . '&nbsp;' .
                 $select->show($is_shared ? $existing['list'] : $default_list['id']));
         }
 
         $this->rc->output->command('plugin.update_itip_object_status', $response);
     }
 
     /**
      * Handler for task/itip-remove requests
      */
     public function task_itip_remove()
     {
         $success = false;
         $uid     = rcube_utils::get_input_value('uid', rcube_utils::INPUT_POST);
 
         // search for event if only UID is given
         if ($task = $this->driver->get_task($uid)) {
             $success = $this->driver->delete_task($task, true);
         }
 
         if ($success) {
             $this->rc->output->show_message('tasklist.successremoval', 'confirmation');
         }
         else {
             $this->rc->output->show_message('tasklist.errorsaving', 'error');
         }
     }
 
 
     /*******  Utility functions  *******/
 
     /**
      * Generate a unique identifier for an event
      */
     public function generate_uid()
     {
       return strtoupper(md5(time() . uniqid(rand())) . '-' . substr(md5($this->rc->user->get_username()), 0, 16));
     }
 
     /**
      * Map task properties for ical exprort using libcalendaring
      */
     public function to_libcal($task)
     {
         $object = $task;
         $object['_type'] = 'task';
         $object['categories'] = (array)$task['tags'];
 
         // convert to datetime objects
         if (!empty($task['date'])) {
             $object['due'] = rcube_utils::anytodatetime($task['date'].' '.$task['time'], $this->timezone);
             if (empty($task['time']))
                 $object['due']->_dateonly = true;
             unset($object['date']);
         }
 
         if (!empty($task['startdate'])) {
             $object['start'] = rcube_utils::anytodatetime($task['startdate'].' '.$task['starttime'], $this->timezone);
             if (empty($task['starttime']))
                 $object['start']->_dateonly = true;
             unset($object['startdate']);
         }
 
         $object['complete'] = $task['complete'] * 100;
         if ($task['complete'] == 1.0 && empty($task['complete'])) {
             $object['status'] = 'COMPLETED';
         }
 
         if ($task['flagged']) {
             $object['priority'] = 1;
         }
         else if (empty($task['priority'])) {
             $object['priority'] = 0;
         }
 
         return $object;
     }
 
     /**
      * Convert task properties from ical parser to the internal format
      */
     public function from_ical($vtodo)
     {
         $task = $vtodo;
 
         $task['tags'] = array_filter((array)$vtodo['categories']);
         $task['flagged'] = $vtodo['priority'] == 1;
         $task['complete'] = floatval($vtodo['complete'] / 100);
 
         // convert from DateTime to internal date format
         if (is_a($vtodo['due'], 'DateTime')) {
             $due = $this->lib->adjust_timezone($vtodo['due']);
             $task['date'] = $due->format('Y-m-d');
             if (!$vtodo['due']->_dateonly)
                 $task['time'] = $due->format('H:i');
         }
         // convert from DateTime to internal date format
         if (is_a($vtodo['start'], 'DateTime')) {
             $start = $this->lib->adjust_timezone($vtodo['start']);
             $task['startdate'] = $start->format('Y-m-d');
             if (!$vtodo['start']->_dateonly)
                 $task['starttime'] = $start->format('H:i');
         }
         if (is_a($vtodo['dtstamp'], 'DateTime')) {
             $task['changed'] = $vtodo['dtstamp'];
         }
 
         unset($task['categories'], $task['due'], $task['start'], $task['dtstamp']);
 
         return $task;
     }
 
     /**
      * Handler for user_delete plugin hook
      */
     public function user_delete($args)
     {
        $this->load_driver();
        return $this->driver->user_delete($args);
     }
 
 
     /**
      * Magic getter for public access to protected members
      */
     public function __get($name)
     {
         switch ($name) {
             case 'ical':
                 return $this->get_ical();
 
             case 'itip':
                 return $this->load_itip();
 
             case 'driver':
                 $this->load_driver();
                 return $this->driver;
         }
 
         return null;
     }
 }