diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index b6c5e234..d46b7229 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -1,3353 +1,3360 @@
 <?php
 
 /**
  * Calendar plugin for Roundcube webmail
  *
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2014-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class calendar extends rcube_plugin
 {
   const FREEBUSY_UNKNOWN = 0;
   const FREEBUSY_FREE = 1;
   const FREEBUSY_BUSY = 2;
   const FREEBUSY_TENTATIVE = 3;
   const FREEBUSY_OOF = 4;
 
   const SESSION_KEY = 'calendar_temp';
 
   public $task = '?(?!login|logout).*';
   public $rc;
   public $lib;
   public $resources_dir;
   public $home;  // declare public to be used in other classes
   public $urlbase;
   public $timezone;
   public $timezone_offset;
   public $gmt_offset;
   public $ui;
 
   public $defaults = array(
     'calendar_default_view' => "agendaWeek",
     'calendar_timeslots'    => 2,
     'calendar_work_start'   => 6,
     'calendar_work_end'     => 18,
     'calendar_agenda_range' => 60,
     'calendar_agenda_sections' => 'smart',
     'calendar_event_coloring'  => 0,
     'calendar_time_indicator'  => true,
     'calendar_allow_invite_shared' => false,
     'calendar_itip_send_option'    => 3,
     'calendar_itip_after_action'   => 0,
   );
 
   private $ical;
   private $itip;
   private $driver;
 
 
   /**
    * Plugin initialization.
    */
   function init()
   {
     $this->require_plugin('libcalendaring');
 
     $this->rc = rcube::get_instance();
     $this->lib = libcalendaring::get_instance();
 
     $this->register_task('calendar', 'calendar');
 
     // load calendar configuration
     $this->load_config();
 
     // load localizations
     $this->add_texts('localization/', $this->rc->task == 'calendar' && (!$this->rc->action || $this->rc->action == 'print'));
 
     $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;
 
     require($this->home . '/lib/calendar_ui.php');
     $this->ui = new calendar_ui($this);
 
     // catch iTIP confirmation requests that don're require a valid session
     if ($this->rc->action == 'attend' && !empty($_REQUEST['_t'])) {
       $this->add_hook('startup', array($this, 'itip_attend_response'));
     }
     else if ($this->rc->action == 'feed' && !empty($_REQUEST['_cal'])) {
       $this->add_hook('startup', array($this, 'ical_feed_export'));
     }
     else {
       // default startup routine
       $this->add_hook('startup', array($this, 'startup'));
     }
 
     $this->add_hook('user_delete', array($this, 'user_delete'));
   }
 
   /**
    * 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;
 
     // load Calendar user interface
     if (!$this->rc->output->ajax_call && (!$this->rc->output->env['framed'] || $args['action'] == 'preview')) {
       $this->ui->init();
 
       // settings are required in (almost) every GUI step
       if ($args['action'] != 'attend')
         $this->rc->output->set_env('calendar_settings', $this->load_settings());
     }
 
     if ($args['task'] == 'calendar' && $args['action'] != 'save-pref') {
       if ($args['action'] != 'upload') {
         $this->load_driver();
       }
 
       // register calendar actions
       $this->register_action('index', array($this, 'calendar_view'));
       $this->register_action('event', array($this, 'event_action'));
       $this->register_action('calendar', array($this, 'calendar_action'));
       $this->register_action('count', array($this, 'count_events'));
       $this->register_action('load_events', array($this, 'load_events'));
       $this->register_action('export_events', array($this, 'export_events'));
       $this->register_action('import_events', array($this, 'import_events'));
       $this->register_action('upload', array($this, 'attachment_upload'));
       $this->register_action('get-attachment', array($this, 'attachment_get'));
       $this->register_action('freebusy-status', array($this, 'freebusy_status'));
       $this->register_action('freebusy-times', array($this, 'freebusy_times'));
       $this->register_action('randomdata', array($this, 'generate_randomdata'));
       $this->register_action('print', array($this,'print_view'));
       $this->register_action('mailimportitip', array($this, 'mail_import_itip'));
       $this->register_action('mailimportattach', array($this, 'mail_import_attachment'));
       $this->register_action('mailtoevent', array($this, 'mail_message2event'));
       $this->register_action('inlineui', array($this, 'get_inline_ui'));
       $this->register_action('check-recent', array($this, 'check_recent'));
       $this->register_action('itip-status', array($this, 'event_itip_status'));
       $this->register_action('itip-remove', array($this, 'event_itip_remove'));
       $this->register_action('itip-decline-reply', array($this, 'mail_itip_decline_reply'));
       $this->register_action('itip-delegate', array($this, 'mail_itip_delegate'));
       $this->register_action('resources-list', array($this, 'resources_list'));
       $this->register_action('resources-owner', array($this, 'resources_owner'));
       $this->register_action('resources-calendar', array($this, 'resources_calendar'));
       $this->register_action('resources-autocomplete', array($this, 'resources_autocomplete'));
       $this->add_hook('refresh', array($this, 'refresh'));
 
       // remove undo information...
       if ($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
       $this->add_hook('preferences_sections_list', array($this, 'preferences_sections_list'));
       $this->add_hook('preferences_list', array($this, 'preferences_list'));
       $this->add_hook('preferences_save', array($this, 'preferences_save')); 
     }
     else if ($args['task'] == 'mail') {
       // hooks to catch event invitations on incoming mails
       if ($args['action'] == 'show' || $args['action'] == 'preview') {
         $this->add_hook('template_object_messagebody', array($this, 'mail_messagebody_html'));
       }
 
       // add 'Create event' item to message menu
       if ($this->api->output->type == 'html') {
         $this->api->add_content(html::tag('li', null, 
           $this->api->output->button(array(
             'command'  => 'calendar-create-from-mail',
             'label'    => 'calendar.createfrommail',
             'type'     => 'link',
             'classact' => 'icon calendarlink active',
             'class'    => 'icon calendarlink',
             'innerclass' => 'icon calendar',
           ))),
           'messagemenu');
 
         $this->api->output->add_label('calendar.createfrommail');
       }
 
       $this->add_hook('messages_list', array($this, 'mail_messages_list'));
       $this->add_hook('message_compose', array($this, 'mail_message_compose'));
     }
     else if ($args['task'] == 'addressbook') {
       if ($this->rc->config->get('calendar_contact_birthdays')) {
         $this->add_hook('contact_update', array($this, 'contact_update'));
         $this->add_hook('contact_create', array($this, 'contact_update'));
       }
     }
 
     // add hooks to display alarms
     $this->add_hook('pending_alarms', array($this, 'pending_alarms'));
     $this->add_hook('dismiss_alarms', array($this, 'dismiss_alarms'));
   }
 
   /**
    * Helper method to load the backend driver according to local config
    */
   private function load_driver()
   {
     if (is_object($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 (!$this->itip) {
       require_once($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(array('accepted','tentative','declined','delegated','needs-action'));
     }
 
     return $this->itip;
   }
 
   /**
    * Load iCalendar functions
    */
   public function get_ical()
   {
     if (!$this->ical) {
       $this->ical = libcalendaring::get_ical();
     }
     
     return $this->ical;
   }
 
   /**
    * Get properties of the calendar this user has specified as default
    */
   public function get_default_calendar($sensitivity = null)
   {
     $default_id = $this->rc->config->get('calendar_default_calendar');
     $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_WRITEABLE);
     $calendar = $calendars[$default_id] ?: null;
     if (!$calendar || $sensitivity) {
       foreach ($calendars as $cal) {
         if ($sensitivity && $cal['subtype'] == $sensitivity) {
           $calendar = $cal;
           break;
         }
         if ($cal['default'] && $cal['editable']) {
           $calendar = $cal;
         }
         if ($cal['editable']) {
           $first = $cal;
         }
       }
     }
 
     return $calendar ?: $first;
   }
 
 
   /**
    * Render the main calendar view from skin template
    */
   function calendar_view()
   {
     $this->rc->output->set_pagetitle($this->gettext('calendar'));
 
     // Add CSS stylesheets to the page header
     $this->ui->addCSS();
 
     // 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');
     $this->rc->output->add_label('libcalendaring.itipaccepted','libcalendaring.itiptentative','libcalendaring.itipdeclined','libcalendaring.itipdelegated','libcalendaring.expandattendeegroup','libcalendaring.expandattendeegroupnodata');
 
     // 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('mscolors', jqueryui::get_color_values());
     $this->rc->output->set_env('identities-selector', $this->ui->identity_select(array('id' => 'edit-identities-list', 'aria-label' => $this->gettext('roleorganizer'))));
 
     $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
     if (in_array($view, array('agendaWeek', 'agendaDay', 'month', 'table')))
       $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'] = array(
       '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($no_override['calendar_default_view'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_default_view';
       $select = new html_select(array('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'), "table");
       $p['blocks']['view']['options']['default_view'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('default_view'))),
         'content' => $select->show($this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view'])),
       );
     }
 
     if (!isset($no_override['calendar_timeslots'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_timeslot';
       $choices = array('1', '2', '3', '4', '6');
       $select = new html_select(array('name' => '_timeslots', 'id' => $field_id));
       $select->add($choices);
       $p['blocks']['view']['options']['timeslots'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('timeslots'))),
         'content' => $select->show(strval($this->rc->config->get('calendar_timeslots', $this->defaults['calendar_timeslots']))),
       );
     }
 
     if (!isset($no_override['calendar_first_day'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_firstday';
       $select = new html_select(array('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');
       $p['blocks']['view']['options']['first_day'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('first_day'))),
         'content' => $select->show(strval($this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']))),
       );
     }
 
     if (!isset($no_override['calendar_first_hour'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $time_format = $this->rc->config->get('time_format', libcalendaring::to_php_date_format($this->rc->config->get('calendar_time_format', $this->defaults['calendar_time_format'])));
       $select_hours = new html_select();
       for ($h = 0; $h < 24; $h++)
         $select_hours->add(date($time_format, mktime($h, 0, 0)), $h);
 
       $field_id = 'rcmfd_firsthour';
       $p['blocks']['view']['options']['first_hour'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('first_hour'))),
         'content' => $select_hours->show($this->rc->config->get('calendar_first_hour', $this->defaults['calendar_first_hour']), array('name' => '_first_hour', 'id' => $field_id)),
       );
     }
 
     if (!isset($no_override['calendar_work_start'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_workstart';
       $p['blocks']['view']['options']['workinghours'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('workinghours'))),
         'content' => $select_hours->show($this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']), array('name' => '_work_start', 'id' => $field_id)) .
         ' &mdash; ' . $select_hours->show($this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']), array('name' => '_work_end', 'id' => $field_id)),
       );
     }
 
     if (!isset($no_override['calendar_event_coloring'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_coloring';
       $select_colors = new html_select(array('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);
 
       $p['blocks']['view']['options']['eventcolors'] = array(
         'title' => html::label($field_id . 'value', rcube::Q($this->gettext('eventcoloring'))),
         'content' => $select_colors->show($this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring'])),
       );
     }
 
     // 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 (!$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(array('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(array('name' => '_alarm_value', 'id' => $field_id . 'value', 'size' => 3));
         $select_offset = new html_select(array('name' => '_alarm_offset', 'id' => $field_id . 'offset'));
 
         foreach (array('-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]);
       }
 
       $p['blocks']['view']['options']['alarmtype'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('defaultalarmtype'))),
         'content' => $alarm_type . ' ' . $alarm_offset,
       );
     }
 
     if (!isset($no_override['calendar_default_calendar'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
       // default calendar selection
       $field_id = 'rcmfd_default_calendar';
       $select_cal = new html_select(array('name' => '_default_calendar', 'id' => $field_id, 'is_escaped' => true));
       foreach ((array)$this->driver->list_calendars(calendar_driver::FILTER_PERSONAL) as $id => $prop) {
         $select_cal->add($prop['name'], strval($id));
         if ($prop['default'])
           $default_calendar = $id;
       }
       $p['blocks']['view']['options']['defaultcalendar'] = array(
         'title' => html::label($field_id . 'value', rcube::Q($this->gettext('defaultcalendar'))),
         'content' => $select_cal->show($this->rc->config->get('calendar_default_calendar', $default_calendar)),
       );
     }
 
     $p['blocks']['itip']['name'] = $this->gettext('itipoptions');
 
     // Invitations handling
     if (!isset($no_override['calendar_itip_after_action'])) {
       if (!$p['current']) {
         $p['blocks']['itip']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_after_action';
       $select   = new html_select(array('name' => '_after_action', 'id' => $field_id,
         'onchange' => "\$('#{$field_id}_select')[this.value == 4 ? 'show' : 'hide']()"));
 
       $select->add($this->gettext('afternothing'), '');
       $select->add($this->gettext('aftertrash'), 1);
       $select->add($this->gettext('afterdelete'), 2);
       $select->add($this->gettext('afterflagdeleted'), 3);
       $select->add($this->gettext('aftermoveto'), 4);
 
       $val = $this->rc->config->get('calendar_itip_after_action', $this->defaults['calendar_itip_after_action']);
       if ($val !== null && $val !== '' && !is_int($val)) {
         $folder = $val;
         $val    = 4;
       }
 
       $folders = $this->rc->folder_selector(array(
           'id'            => $field_id . '_select',
           'name'          => '_after_action_folder',
           'maxlength'     => 30,
           'folder_filter' => 'mail',
           'folder_rights' => 'w',
           'style'         => $val !== 4 ? 'display:none' : '',
       ));
 
       $p['blocks']['itip']['options']['after_action'] = array(
         'title'   => html::label($field_id, rcube::Q($this->gettext('afteraction'))),
         'content' => $select->show($val) . $folders->show($folder),
       );
     }
 
     // category definitions
     if (!$this->driver->nocategories && !isset($no_override['calendar_categories'])) {
         $p['blocks']['categories']['name'] = $this->gettext('categories');
 
         if (!$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);
           $category_remove = new html_inputfield(array('type' => 'button', 'value' => 'X', 'class' => 'button', 'onclick' => '$(this).parent().remove()', 'title' => $this->gettext('remove_category')));
           $category_name  = new html_inputfield(array('name' => "_categories[$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 = $this->driver->categoriesimmutable ? html::tag('input', array('type' => 'hidden', 'name' => "_categories[$key]", 'value' => $name)) : '';
           $categories_list .= html::div(null, $hidden . $category_name->show($name) . '&nbsp;' . $category_color->show($color) . '&nbsp;' . $category_remove->show());
         }
 
         $p['blocks']['categories']['options']['category_' . $name] = array(
           'content' => html::div(array('id' => 'calendarcategories'), $categories_list),
         );
 
         $field_id = 'rcmfd_new_category';
         $new_category = new html_inputfield(array('name' => '_new_category', 'id' => $field_id, 'size' => 30));
         $add_category = new html_inputfield(array('type' => 'button', 'class' => 'button', 'value' => $this->gettext('add_category'),  'onclick' => "rcube_calendar_add_category()"));
         $p['blocks']['categories']['options']['categories'] = array(
           'content' => $new_category->show('') . '&nbsp;' . $add_category->show(),
         );
 
         $this->rc->output->add_script('function rcube_calendar_add_category(){
           var name = $("#rcmfd_new_category").val();
           if (name.length) {
             var input = $("<input>").attr("type", "text").attr("name", "_categories[]").attr("size", 30).val(name);
             var color = $("<input>").attr("type", "text").attr("name", "_colors[]").attr("size", 6).addClass("colors").val("000000");
             var button = $("<input>").attr("type", "button").attr("value", "X").addClass("button").click(function(){ $(this).parent().remove() });
             $("<div>").append(input).append("&nbsp;").append(color).append("&nbsp;").append(button).appendTo("#calendarcategories");
             color.miniColors({ colorValues:(rcmail.env.mscolors || []) });
             $("#rcmfd_new_category").val("");
           }
         }');
 
         $this->rc->output->add_script('$("#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 (!$p['current']) {
         $p['blocks']['birthdays']['content'] = true;
         return $p;
       }
 
       $field_id = 'rcmfd_contact_birthdays';
       $input    = new html_checkbox(array('name' => '_contact_birthdays', 'id' => $field_id, 'value' => 1, 'onclick' => '$(".calendar_birthday_props").prop("disabled",!this.checked)'));
 
       $p['blocks']['birthdays']['options']['contact_birthdays'] = array(
         'title'   => html::label($field_id, $this->gettext('displaybirthdayscalendar')),
         'content' => $input->show($this->rc->config->get('calendar_contact_birthdays')?1:0),
       );
 
       $input_attrib = array(
         'class' => 'calendar_birthday_props',
         'disabled' => !$this->rc->config->get('calendar_contact_birthdays'),
       );
 
       $sources = array();
       $checkbox = new html_checkbox(array('name' => '_birthday_adressbooks[]') + $input_attrib);
       foreach ($this->rc->get_address_sources(false, true) as $source) {
         $active = in_array($source['id'], (array)$this->rc->config->get('calendar_birthday_adressbooks', array())) ? $source['id'] : '';
         $sources[] = html::label(null, $checkbox->show($active, array('value' => $source['id'])) . '&nbsp;' . rcube::Q($source['realname'] ?: $source['name']));
       }
 
       $p['blocks']['birthdays']['options']['birthday_adressbooks'] = array(
         'title'   => rcube::Q($this->gettext('birthdayscalendarsources')),
         'content' => join(html::br(), $sources),
       );
 
       $field_id = 'rcmfd_birthdays_alarm';
       $select_type = new html_select(array('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(array('name' => '_birthdays_alarm_value', 'id' => $field_id . 'value', 'size' => 3) + $input_attrib);
       $select_offset = new html_select(array('name' => '_birthdays_alarm_offset', 'id' => $field_id . 'offset') + $input_attrib);
       foreach (array('-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'));
       $p['blocks']['birthdays']['options']['birthdays_alarmoffset'] = array(
         'title' => html::label($field_id . 'value', rcube::Q($this->gettext('showalarms'))),
         'content' => $select_type->show($this->rc->config->get('calendar_birthdays_alarm_type', '')) . ' ' . $input_value->show($preset[0]) . '&nbsp;' . $select_offset->show($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'] = array(
         '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_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'    => rcube_utils::get_input_value('_contact_birthdays', rcube_utils::INPUT_POST) ? true : false,
         'calendar_birthday_adressbooks' => (array) rcube_utils::get_input_value('_birthday_adressbooks', rcube_utils::INPUT_POST),
         'calendar_birthdays_alarm_type'   => rcube_utils::get_input_value('_birthdays_alarm_type', rcube_utils::INPUT_POST),
         'calendar_birthdays_alarm_offset' => $birthdays_alarm_value ?: null,
         'calendar_itip_after_action'      => intval(rcube_utils::get_input_value('_after_action', rcube_utils::INPUT_POST)),
       );
 
       if ($p['prefs']['calendar_itip_after_action'] == 4) {
         $p['prefs']['calendar_itip_after_action'] = rcube_utils::get_input_value('_after_action_folder', rcube_utils::INPUT_POST, true);
       }
 
       // categories
       if (!$this->driver->nocategories) {
         $old_categories = $new_categories = array();
         foreach ($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) {
           $color = preg_replace('/^#/', '', strval($colors[$key]));
 
           // rename categories in existing events -> driver's job
           if ($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)$old_categories[$key] 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 = $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', array('id' => $cal['id']));
         break;
       case "subscribe":
         if (!$this->driver->subscribe_calendar($cal))
           $this->rc->output->show_message($this->gettext('errorsaving'), 'error');
         else {
           $calendars = $this->driver->list_calendars();
           $calendar  = $calendars[$cal['id']];
 
           // find parent folder and check if it's a "user calendar"
           // if it's also activated we need to refresh it (#5340)
           while ($calendar['parent']) {
             if (isset($calendars[$calendar['parent']]))
               $calendar = $calendars[$calendar['parent']];
             else
               break;
           }
 
           if ($calendar['id'] != $cal['id'] && $calendar['active'] && $calendar['group'] == "other user")
             $this->rc->output->command('plugin.refresh_source', $calendar['id']);
         }
         return;
       case "search":
         $results    = array();
         $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[] = $cal;
         }
         // report more results available
         if ($this->driver->search_more_results)
           $this->rc->output->show_message('autocompletemore', 'info');
 
         $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 {
       $error_msg = $this->gettext('errorsaving') . ($this->driver->last_error ? ': ' . $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;
     
     // force notify if hidden + active
     if ((int)$this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']) === 1)
       $event['_notify'] = 1;
 
     // read old event data in order to find changes
     if (($event['_notify'] || $event['_decline']) && $action != 'new') {
       $old = $this->driver->get_event($event);
 
       // load main event if savemode is 'all' or if deleting 'future' events
       if (($event['_savemode'] == 'all' || ($event['_savemode'] == 'future' && $action == 'remove' && !$event['_decline'])) && $old['recurrence_id']) {
         $old['id'] = $old['recurrence_id'];
         $old = $this->driver->get_event($old);
       }
     }
 
     switch ($action) {
       case "new":
         // create UID for new event
         $event['uid'] = $this->generate_uid();
         $this->write_preprocess($event, $action);
         if ($success = $this->driver->new_event($event)) {
           $event['id'] = $event['uid'];
           $event['_savemode'] = 'all';
           $this->cleanup_event($event);
           $this->event_save_success($event, null, $action, true);
         }
         $reload = $success && $event['recurrence'] ? 2 : 1;
         break;
         
       case "edit":
         $this->write_preprocess($event, $action);
         if ($success = $this->driver->edit_event($event)) {
           $this->cleanup_event($event);
           $this->event_save_success($event, $old, $action, $success);
         }
         $reload = $success && ($event['recurrence'] || $event['_savemode'] || $event['_fromcalendar']) ? 2 : 1;
         break;
       
       case "resize":
         $this->write_preprocess($event, $action);
         if ($success = $this->driver->resize_event($event)) {
           $this->event_save_success($event, $old, $action, $success);
         }
         $reload = $event['_savemode'] ? 2 : 1;
         break;
       
       case "move":
         $this->write_preprocess($event, $action);
         if ($success = $this->driver->move_event($event)) {
           $this->event_save_success($event, $old, $action, $success);
         }
         $reload  = $success && $event['_savemode'] ? 2 : 1;
         break;
       
       case "remove":
         // remove previous deletes
         $undo_time = $this->driver->undelete ? $this->rc->config->get('undo_timeout', 0) : 0;
         $this->rc->session->remove('calendar_event_undo');
         
         // search for event if only UID is given
         if (!isset($event['calendar']) && $event['uid']) {
           if (!($event = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE))) {
             break;
           }
           $undo_time = 0;
         }
 
         $success = $this->driver->remove_event($event, $undo_time < 1);
         $reload = (!$success || $event['_savemode']) ? 2 : 1;
 
         if ($undo_time > 0 && $success) {
           $_SESSION['calendar_event_undo'] = array('ts' => time(), 'data' => $event);
           // display message with Undo link.
           $msg = html::span(null, $this->gettext('successremoval'))
             . ' ' . html::a(array('onclick' => sprintf("%s.http_request('event', 'action=undo', %s.display_message('', 'loading'))",
               rcmail_output::JS_OBJECT_NAME, rcmail_output::JS_OBJECT_NAME)), $this->gettext('undo'));
           $this->rc->output->show_message($msg, 'confirmation', null, true, $undo_time);
           $got_msg = true;
         }
         else if ($success) {
           $this->rc->output->show_message('calendar.successremoval', 'confirmation');
           $got_msg = true;
         }
 
         // send cancellation for the main event
         if ($event['_savemode'] == 'all') {
           unset($old['_instance'], $old['recurrence_date'], $old['recurrence_id']);
         }
         // send an update for the main event's recurrence rule instead of a cancellation message
         else if ($event['_savemode'] == 'future' && $success !== false && $success !== true) {
           $event['_savemode'] = 'all';  // force event_save_success() to load master event
           $action = 'edit';
           $success = true;
         }
 
         // send iTIP reply that participant has declined the event
         if ($success && $event['_decline']) {
           $emails = $this->get_user_emails();
           foreach ($old['attendees'] as $i => $attendee) {
             if ($attendee['role'] == 'ORGANIZER')
               $organizer = $attendee;
             else if ($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'))
             $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $organizer['name'] ? $organizer['name'] : $organizer['email']))), '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
         $event  = $_SESSION['calendar_event_undo']['data'];
 
         if ($event)
           $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'];
 
         // send invitation to delegatee + add it as attendee
         if ($status == 'delegated' && $event['to']) {
           $itip = $this->load_itip();
           if ($itip->delegate_to($ev, $event['to'], (bool)$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'] || $event['recurrence'] ? 2 : 1;
           $organizer = null;
           $emails = $this->get_user_emails();
 
           foreach ($event['attendees'] as $i => $attendee) {
             if ($attendee['role'] == 'ORGANIZER') {
               $organizer = $attendee;
             }
             else if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
               $reply_sender = $attendee['email'];
             }
           }
 
           if (!$noreply) {
             $itip = $this->load_itip();
             $itip->set_sender_email($reply_sender);
             $event['comment'] = $reply_comment;
             $event['thisandfuture'] = $event['_savemode'] == 'future';
             if ($organizer && $itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status))
               $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $organizer['name'] ? $organizer['name'] : $organizer['email']))), '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', array('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, $dtformat) {
             if ($change['date']) {
               $dt = $lib->adjust_timezone($change['date']);
               if ($dt instanceof DateTime)
                 $change['date'] = $this->rc->format_date($dt, $dtformat, false);
             }
           });
           $this->rc->output->command('plugin.render_event_changelog', $data);
         }
         else {
           $this->rc->output->command('plugin.render_event_changelog', false);
         }
         $got_msg = true;
         $reload = false;
         break;
 
       case "diff":
         $data = $this->driver->get_event_diff($event, $event['rev1'], $event['rev2']);
         if (is_array($data)) {
           // convert some properties, similar to self::_client_event()
           $lib = $this->lib;
           array_walk($data['changes'], function(&$change, $i) use ($event, $lib) {
             // convert date cols
             foreach (array('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;
           $this->rc->output->command('display_message', $this->gettext(array('name' => 'objectrestoresuccess', 'vars' => array('rev' => $event['rev']))), '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');
 
     // update event object on the client or trigger a complete refretch if too complicated
     if ($reload) {
       $args = array('source' => $event['calendar']);
       if ($reload > 1)
         $args['refetch'] = true;
       else if ($success && $action != 'remove')
         $args['update'] = $this->_client_event($this->driver->get_event($event), true);
       $this->rc->output->command('plugin.refresh_calendar', $args);
     }
   }
 
   /**
    * Helper method sending iTip notifications after successful event updates
    */
   private function event_save_success(&$event, $old, $action, $success)
   {
     // $success is a new event ID
     if ($success !== true) {
       // send update notification on the main event
       if ($event['_savemode'] == 'future' && $event['_notify'] && $old['attendees'] && $old['recurrence_id']) {
         $master = $this->driver->get_event(array('id' => $old['recurrence_id'], 'calendar' => $old['calendar']), 0, true);
         unset($master['_instance'], $master['recurrence_date']);
 
         $sent = $this->notify_attendees($master, null, $action, $event['_comment'], false);
         if ($sent < 0)
           $this->rc->output->show_message('calendar.errornotifying', 'error');
 
         $event['attendees'] = $master['attendees'];  // this tricks us into the next if clause
       }
 
       // delete old reference if saved as new
       if ($event['_savemode'] == 'future' || $event['_savemode'] == 'new') {
         $old = null;
       }
 
       $event['id'] = $success;
       $event['_savemode'] = 'all';
     }
 
     // send out notifications
     if ($event['_notify'] && ($event['attendees'] || $old['attendees'])) {
       $_savemode = $event['_savemode'];
 
       // send notification for the main event when savemode is 'all'
       if ($action != 'remove' && $_savemode == 'all' && ($event['recurrence_id'] || $old['recurrence_id'] || ($old && $old['id'] != $event['id']))) {
         $event['id'] = $event['recurrence_id'] ?: ($old['recurrence_id'] ?: $old['id']);
         $event = $this->driver->get_event($event, 0, true);
         unset($event['_instance'], $event['recurrence_date']);
       }
       else {
         // make sure we have the complete record
         $event = $action == 'remove' ? $old : $this->driver->get_event($event, 0, true);
       }
 
       $event['_savemode'] = $_savemode;
 
       if ($old) {
         $old['thisandfuture'] = $_savemode == 'future';
       }
 
       // only notify if data really changed (TODO: do diff check on client already)
       if (!$old || $action == 'remove' || self::event_diff($event, $old)) {
         $sent = $this->notify_attendees($event, $old, $action, $event['_comment']);
         if ($sent > 0)
           $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
         else if ($sent < 0)
           $this->rc->output->show_message('calendar.errornotifying', 'error');
       }
     }
   }
 
   /**
    * Handler for load-requests from fullcalendar
    * This will return pure JSON formatted output
    */
   function load_events()
   {
     $events = $this->driver->load_events(
       rcube_utils::get_input_value('start', rcube_utils::INPUT_GET),
       rcube_utils::get_input_value('end', rcube_utils::INPUT_GET),
       ($query = rcube_utils::get_input_value('q', rcube_utils::INPUT_GET)),
       rcube_utils::get_input_value('source', rcube_utils::INPUT_GET)
     );
     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;
 
     $start = rcube_utils::get_input_value('start', rcube_utils::INPUT_GET);
     if (!$start) {
       $start = new DateTime('today 00:00:00', $this->timezone);
       $start = $start->format('U');
     }
 
     $counts = $this->driver->count_events(
       rcube_utils::get_input_value('source', rcube_utils::INPUT_GET),
       $start,
       rcube_utils::get_input_value('end', rcube_utils::INPUT_GET)
     );
 
     $this->rc->output->command('plugin.update_counts', array('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 = array();
 
     if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
       $partstat = 'NEEDS-ACTION';
 /*
       $user_emails = $this->lib->get_user_emails();
       foreach ($event['attendees'] as $attendee) {
         if (in_array($attendee['email'], $user_emails)) {
           $partstat = $attendee['status'];
           break;
         }
       }
 */
       $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($event['recurrence'])) {
         foreach ($this->driver->get_recurring_events($event, $event['start']) 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', array('refetch' => true));
         return;
     }
 
     $counts = array();
 
     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',
           array('source' => $cal['id'], 'update' => $this->_client_event($event)));
       }
 
       // refresh count for this calendar
       if ($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', array('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 = $p['time'] ?: time();
     if ($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 && $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 && $_FILES['_data']['tmp_name']) {
       $calendar   = rcube_utils::get_input_value('calendar', rcube_utils::INPUT_GPC);
       $rangestart = $_REQUEST['_range'] ? date_create("now -" . intval($_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(array('name' => 'importsuccess', 'vars' => array('nr' => $count))), 'confirmation');
         $this->rc->output->command('plugin.import_success', array('source' => $calendar, 'refetch' => true));
       }
       else if (!$errors) {
         $this->rc->output->command('display_message', $this->gettext('importnone'), 'notice');
         $this->rc->output->command('plugin.import_success', array('source' => $calendar));
       }
       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, $calendar, $rangestart, &$errors)
   {
     $user_email = $this->rc->user->get_username();
 
     $ical = $this->get_ical();
     $errors = !$ical->fopen($filepath);
     $count = $i = 0;
     foreach ($ical as $event) {
       // keep the browser connection alive on long import jobs
       if (++$i > 100 && $i % 100 == 0) {
           echo "<!-- -->";
           ob_flush();
       }
 
       // TODO: correctly handle recurring events which start before $rangestart
       if ($event['end'] < $rangestart && (!$event['recurrence'] || ($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);
 
     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');
 
     $event_id    = rcube_utils::get_input_value('id', rcube_utils::INPUT_GET);
     $attachments = rcube_utils::get_input_value('attachments', rcube_utils::INPUT_GET);
     $calid = $filename = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
 
     $calendars = $this->driver->list_calendars();
     $events = array();
 
     if ($calendars[$calid]) {
       $filename = $calendars[$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(array('calendar' => $calid, 'id' => $event_id), 0, true)) {
           if ($event['recurrence_id']) {
             $event = $this->driver->get_event(array('calendar' => $calid, 'id' => $event['recurrence_id']), 0, true);
           }
           $events = array($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, $attachments ? array($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', array(
         '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="Roundcube 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->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 = array();
 
     // configuration
     $settings['default_calendar'] = $this->rc->config->get('calendar_default_calendar');
     $settings['default_view'] = (string)$this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view']);
     $settings['date_agenda'] = (string)$this->rc->config->get('calendar_date_agenda', $this->defaults['calendar_date_agenda']);
 
     $settings['timeslots'] = (int)$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['agenda_sections'] = $this->rc->config->get('calendar_agenda_sections', $this->defaults['calendar_agenda_sections']);
     $settings['event_coloring'] = (int)$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']);
     $settings['invitation_calendars'] = (bool)$this->rc->config->get('kolab_invitation_calendars', false);
     $settings['itip_notify'] = (int)$this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
     // get user identity to create default attendee
     if ($this->ui->screen == 'calendar') {
       foreach ($this->rc->user->list_emails() as $rec) {
         if (!$identity)
           $identity = $rec;
         $identity['emails'][] = $rec['email'];
         $settings['identities'][$rec['identity_id']] = $rec['email'];
       }
       $identity['emails'][] = $this->rc->user->get_username();
       $settings['identity'] = array('name' => $identity['name'], 'email' => strtolower($identity['email']), 'emails' => ';' . strtolower(join(';', $identity['emails'])));
     }
 
     return $settings;
   }
 
   /**
    * Encode events as JSON
    *
    * @param  array  Events as array
    * @param  boolean Add CSS class names according to calendar and categories
    * @return string JSON encoded events
    */
   function encode($events, $addcss = false)
   {
     $json = array();
     foreach ($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, $addcss = false)
   {
     // compose a human readable strings for alarms_text and recurrence_text
     if ($event['valarms']) {
       $event['alarms_text'] = libcalendaring::alarms_text($event['valarms']);
       $event['valarms'] = libcalendaring::to_client_alarms($event['valarms']);
     }
     if ($event['recurrence']) {
       $event['recurrence_text'] = $this->lib->recurrence_text($event['recurrence']);
       $event['recurrence'] = $this->lib->to_client_recurrence($event['recurrence'], $event['allday']);
       unset($event['recurrence_date']);
     }
 
     foreach ((array)$event['attachments'] as $k => $attachment) {
       $event['attachments'][$k]['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
       unset($event['attachments'][$k]['data'], $event['attachments'][$k]['content']);
 
       if (!$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 = $attendee;
       }
       if ($attendee['status'] == 'DELEGATED' && $attendee['rsvp'] == false) {
         $event['attendees'][$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']))
         $event['attendees'] = array();
       array_unshift($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 because of the fullcalendar client script
     $event['vurl'] = $event['url'];
     unset($event['url']);
 
     return array(
       '_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' => $event['changed'] ? $this->lib->adjust_timezone($event['changed'])->format('c') : null,
       'created' => $event['created'] ? $this->lib->adjust_timezone($event['created'])->format('c') : null,
       'title'       => strval($event['title']),
       'description' => strval($event['description']),
       'location'    => strval($event['location']),
       'className'   => ($addcss ? 'fc-event-cal-'.asciiwords($event['calendar'], true).' ' : '') .
           'fc-event-cat-' . asciiwords(strtolower(join('-', (array)$event['categories'])), true) .
           rtrim(' ' . $event['className']),
       'allDay'      => ($event['allday'] == 1),
     ) + $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   = $_REQUEST['_num'] ? intval($_REQUEST['_num']) : 100;
     $date  = $_REQUEST['_date'] ?: 'now';
     $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(array(
         '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()
   {
     $this->lib->attachment_upload(self::SESSION_KEY, 'cal-');
   }
 
   /**
    * Handler for attachments download/displaying
    */
   public function attachment_get()
   {
     // show loading page
     if (!empty($_GET['_preload'])) {
         return $this->lib->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 = array('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'])) {
         $this->lib->attachment = $attachment;
         $this->register_handler('plugin.attachmentframe', array($this->lib, 'attachment_frame'));
         $this->register_handler('plugin.attachmentcontrols', array($this->lib, 'attachment_header'));
         $this->rc->output->send('calendar.attachment');
     }
     // deliver attachment content
     else if ($attachment) {
         if ($calendar != '--invitation--itip') {
             $attachment['body'] = $this->driver->get_attachment_body($id, $event);
         }
 
         $this->lib->attachment_get($attachment);
     }
 
     // if we arrive here, the requested part was not found
     header('HTTP/1.1 404 Not Found');
     exit;
   }
 
   /**
    * Determine whether the given event description is HTML formatted
    */
   private function is_html($event)
   {
       // check for opening and closing <html> or <body> tags
       return (preg_match('/<(html|body)(\s+[a-z]|>)/', $event['description'], $m) && strpos($event['description'], '</'.$m[1].'>') > 0);
   }
 
   /**
    * Prepares new/edited event properties before save
    */
   private function write_preprocess(&$event, $action)
   {
     // 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);
     $event['allday'] = (bool)$event['allday'];
 
     // start/end is all we need for 'move' action (#1480)
     if ($action == 'move') {
       return;
     }
 
     // convert the submitted recurrence settings
     if (is_array($event['recurrence'])) {
       $event['recurrence'] = $this->lib->from_client_recurrence($event['recurrence'], $event['start']);
     }
 
     // convert the submitted alarm values
     if ($event['valarms']) {
       $event['valarms'] = libcalendaring::from_client_alarms($event['valarms']);
     }
 
     $attachments = array();
     $eventid     = 'cal-'.$event['id'];
 
     if (is_array($_SESSION[self::SESSION_KEY]) && $_SESSION[self::SESSION_KEY]['id'] == $eventid) {
       if (!empty($_SESSION[self::SESSION_KEY]['attachments'])) {
         foreach ($_SESSION[self::SESSION_KEY]['attachments'] as $id => $attachment) {
           if (is_array($event['attachments']) && in_array($id, $event['attachments'])) {
             $attachments[$id] = $this->rc->plugins->exec_hook('attachment_get', $attachment);
           }
         }
       }
     }
 
     $event['attachments'] = $attachments;
 
     // convert link references into simple URIs
     if (array_key_exists('links', $event)) {
       $event['links'] = array_map(function($link) {
           return is_array($link) ? $link['uri'] : strval($link);
         }, (array)$event['links']);
     }
 
     // check for organizer in attendees
     if ($action == 'new' || $action == 'edit') {
       if (!$event['attendees'])
         $event['attendees'] = array();
 
       $emails = $this->get_user_emails();
       $organizer = $owner = false;
       foreach ((array)$event['attendees'] as $i => $attendee) {
         if ($attendee['role'] == 'ORGANIZER')
           $organizer = $i;
         if ($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';
       }
 
       // set new organizer identity
       if ($organizer !== false && !empty($event['_identity']) && ($identity = $this->rc->user->get_identity($event['_identity']))) {
         $event['attendees'][$organizer]['name'] = $identity['name'];
         $event['attendees'][$organizer]['email'] = $identity['email'];
       }
 
       // set owner as organizer if yet missing
       if ($organizer === false && $owner !== false) {
         $event['attendees'][$owner]['role'] = 'ORGANIZER';
         unset($event['attendees'][$owner]['rsvp']);
       }
     }
 
     // mapping url => vurl because of the fullcalendar client script
     if (array_key_exists('vurl', $event)) {
       $event['url'] = $event['vurl'];
       unset($event['vurl']);
     }
   }
 
   /**
    * Releases some resources after successful event save
    */
   private function cleanup_event(&$event)
   {
     // remove temp. attachment files
     if (!empty($_SESSION[self::SESSION_KEY]) && ($eventid = $_SESSION[self::SESSION_KEY]['id'])) {
       $this->rc->plugins->exec_hook('attachments_cleanup', array('group' => $eventid));
       $this->rc->session->remove(self::SESSION_KEY);
     }
   }
 
   /**
    * Send out an invitation/notification to all event attendees
    */
   private function notify_attendees($event, $old, $action = 'edit', $comment = null, $rsvp = null)
   {
     if ($action == 'remove' || ($event['status'] == 'CANCELLED' && $old['status'] != $event['status'])) {
       $event['cancelled'] = true;
       $is_cancelled = true;
     }
 
     if ($rsvp === null)
       $rsvp = !$old || $event['sequence'] > $old['sequence'];
 
     $itip = $this->load_itip();
     $emails = $this->get_user_emails();
     $itip_notify = (int)$this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
     // add comment to the iTip attachment
     $event['comment'] = $comment;
 
     // set a valid recurrence-id if this is a recurrence instance
     libcalendaring::identify_recurrence_instance($event);
 
     // compose multipart message using PEAR:Mail_Mime
     $method = $action == 'remove' ? 'CANCEL' : 'REQUEST';
     $message = $itip->compose_itip_message($event, $method, $rsvp);
 
     // list existing attendees from $old event
     $old_attendees = array();
     foreach ((array)$old['attendees'] as $attendee) {
       $old_attendees[] = $attendee['email'];
     }
 
     // send to every attendee
     $sent = 0; $current = array();
     foreach ((array)$event['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 || $event['sequence'] > $old['sequence'];
       $bodytext = $is_cancelled ? 'eventcancelmailbody' : ($is_new ? 'invitationmailbody' : 'eventupdatemailbody');
       $subject  = $is_cancelled ? 'eventcancelsubject'  : ($is_new ? 'invitationsubject' : ($event['title'] ? 'eventupdatesubject':'eventupdatesubjectempty'));
 
       $event['comment'] = $comment;
 
       // finally send the message
       if ($itip->send_itip_message($event, $method, $attendee, $subject, $bodytext, $message, $is_rsvp))
         $sent++;
       else
         $sent = -100;
     }
 
     // TODO: on change of a recurring (main) event, also send updates to differing attendess of recurrence exceptions
 
     // send CANCEL message to removed attendees
     foreach ((array)$old['attendees'] as $attendee) {
       if ($attendee['role'] == 'ORGANIZER' || !$attendee['email'] || in_array(strtolower($attendee['email']), $current))
         continue;
 
       $vevent = $old;
       $vevent['cancelled'] = $is_cancelled;
       $vevent['attendees'] = array($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 = rcube_utils::get_input_value('start', rcube_utils::INPUT_GPC);
     $end   = rcube_utils::get_input_value('end', rcube_utils::INPUT_GPC);
 
     // convert dates into unix timestamps
     if (!empty($start) && !is_numeric($start)) {
       $dts = new DateTime($start, $this->timezone);
       $start = $dts->format('U');
     }
     if (!empty($end) && !is_numeric($end)) {
       $dte = new DateTime($end, $this->timezone);
       $end = $dte->format('U');
     }
     
     if (!$start) $start = time();
     if (!$end) $end = $start + 3600;
     
     $fbtypemap = array(calendar::FREEBUSY_UNKNOWN => 'UNKNOWN', calendar::FREEBUSY_FREE => 'FREE', calendar::FREEBUSY_BUSY => 'BUSY', calendar::FREEBUSY_TENTATIVE => 'TENTATIVE', calendar::FREEBUSY_OOF => 'OUT-OF-OFFICE');
     $status = 'UNKNOWN';
     
     // 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) && $fbtypemap[$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 = rcube_utils::get_input_value('start', rcube_utils::INPUT_GPC);
     $end   = rcube_utils::get_input_value('end', rcube_utils::INPUT_GPC);
     $interval  = intval(rcube_utils::get_input_value('interval', rcube_utils::INPUT_GPC));
     $strformat = $interval > 60 ? 'Ymd' : 'YmdHis';
 
     // convert dates into unix timestamps
     if (!empty($start) && !is_numeric($start)) {
       $dts = rcube_utils::anytodatetime($start, $this->timezone);
       $start = $dts ? $dts->format('U') : null;
     }
     if (!empty($end) && !is_numeric($end)) {
       $dte = rcube_utils::anytodatetime($end, $this->timezone);
       $end = $dte ? $dte->format('U') : null;
     }
 
     if (!$start) $start = time();
     if (!$end)   $end = $start + 86400 * 30;
     if (!$interval) $interval = 60;  // 1 hour
     
     if (!$dte) {
       $dts = new DateTime('@'.$start);
       $dts->setTimezone($this->timezone);
     }
     
     $fblist = $this->driver->get_freebusy_list($email, $start, $end);
     $slots = array();
     
     // build a list from $start till $end with blocks representing the fb-status
     for ($s = 0, $t = $start; $t <= $end; $s++) {
       $status = self::FREEBUSY_UNKNOWN;
       $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;
 
           // check for possible all-day times
           if (gmdate('His', $from) == '000000' && gmdate('His', $to) == '235959') {
               // shift into the user's timezone for sane matching
               $from -= $this->gmt_offset;
               $to   -= $this->gmt_offset;
           }
 
           if ($from < $t_end && $to > $t) {
             $status = isset($type) ? $type : self::FREEBUSY_BUSY;
             if ($status == self::FREEBUSY_BUSY)  // can't get any worse :-)
               break;
           }
         }
       }
       
       $slots[$s] = $status;
       $times[$s] = intval($dt->format($strformat));
       $t = $t_end;
     }
     
     $dte = new DateTime('@'.$t_end);
     $dte->setTimezone($this->timezone);
     
     // let this information be cached for 5min
     $this->rc->output->future_expire_header(300);
     
     echo rcube_output::json_serialize(array(
       'email' => $email,
       'start' => $dts->format('c'),
       'end'   => $dte->format('c'),
       'interval' => $interval,
       'slots' => $slots,
       'times' => $times,
     ));
     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, array('agendaWeek', 'agendaDay', 'month', 'table')))
       $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 (isset($_REQUEST['sections']))
       $this->rc->output->set_env('listSections', rcube_utils::get_input_value('sections', rcube_utils::INPUT_GPC));
 
     if ($search = rcube_utils::get_input_value('search', rcube_utils::INPUT_GPC)) {
       $this->rc->output->set_env('search', $search);
       $title .= ' "' . $search . '"';
     }
 
     // Add CSS stylesheets to the page header
     $skin_path = $this->local_skin_path();
     $this->include_stylesheet($skin_path . '/fullcalendar.css');
     $this->include_stylesheet($skin_path . '/print.css');
     
     // Add JS files to the page header
     $this->include_script('print.js');
     $this->include_script('lib/js/fullcalendar.js');
     
     $this->register_handler('plugin.calendar_css', array($this->ui, 'calendar_css'));
     $this->register_handler('plugin.calendar_list', array($this->ui, 'calendar_list'));
     
     $this->rc->output->set_pagetitle($title);
     $this->rc->output->send("calendar.print");
   }
 
   /**
    *
    */
   public function get_inline_ui()
   {
     foreach (array('save','cancel','savingdata') as $label)
       $texts['calendar.'.$label] = $this->gettext($label);
     
     $texts['calendar.new_event'] = $this->gettext('createfrommail');
     
     $this->ui->init_templates();
     $this->ui->calendar_list();  # set env['calendars']
     echo $this->api->output->parse('calendar.eventedit', false, false);
     echo html::tag('script', array('type' => 'text/javascript'),
       "rcmail.set_env('calendars', " . rcube_output::json_serialize($this->api->output->env['calendars']) . ");\n".
       "rcmail.set_env('deleteicon', '" . $this->api->output->env['deleteicon'] . "');\n".
       "rcmail.set_env('cancelicon', '" . $this->api->output->env['cancelicon'] . "');\n".
       "rcmail.set_env('loadingicon', '" . $this->api->output->env['loadingicon'] . "');\n".
       "rcmail.gui_object('attachmentlist', '"  . $this->ui->attachmentlist_id . "');\n".
       "rcmail.add_label(" . rcube_output::json_serialize($texts) . ");\n"
     );
     exit;
   }
 
   /**
    * 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 = array();
     $ignore = array('changed' => 1, 'attachments' => 1);
     foreach (array_unique(array_merge(array_keys($a), array_keys($b))) as $key) {
       if (!$ignore[$key] && $key[0] != '_' && $a[$key] != $b[$key])
         $diff[] = $key;
     }
     
     // only compare number of attachments
     if (count($a['attachments']) != count($b['attachments']))
       $diff[] = 'attachments';
     
     return $diff;
   }
 
   /**
    * Update attendee properties on the given event object
    *
    * @param array The event object to be altered
    * @param array List of hash arrays each represeting an updated/added attendee
    */
   public static function merge_attendee_data(&$event, $attendees, $removed = null)
   {
     if (!empty($attendees) && !is_array($attendees[0])) {
       $attendees = array($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 (is_object($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 = array();
 
     if ($directory = $this->resources_directory()) {
       foreach ($directory->load_resources($search, $maxnum) as $rec) {
         $results[]  = array(
             '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 = array();
 
     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 = array();
 
     if ($directory = $this->resources_directory()) {
       $events = $directory->get_resource_calendar(
         rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC),
         rcube_utils::get_input_value('start', rcube_utils::INPUT_GET),
         rcube_utils::get_input_value('end', rcube_utils::INPUT_GET));
     }
 
     echo $this->encode($events);
     exit;
   }
 
 
   /****  Event invitation plugin hooks ****/
 
   /**
    * Handler for calendar/itip-status requests
    */
   function event_itip_status()
   {
     $data = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
     // find local copy of the referenced event
     $this->load_driver();
     $existing = $this->driver->get_event($data, calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL);
 
     $itip = $this->load_itip();
     $response = $itip->get_itip_status($data, $existing);
 
     // get a list of writeable calendars to save new events to
     if (!$existing && !$data['nosave'] && $response['action'] == 'rsvp' || $response['action'] == 'import') {
       $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL);
       $calendar_select = new html_select(array('name' => 'calendar', 'id' => 'itip-saveto', 'is_escaped' => true));
       $calendar_select->add('--', '');
       $numcals = 0;
       foreach ($calendars as $calendar) {
         if ($calendar['editable']) {
           $calendar_select->add($calendar['name'], $calendar['id']);
           $numcals++;
         }
       }
       if ($numcals <= 1)
         $calendar_select = null;
     }
 
     if ($calendar_select) {
       $default_calendar = $this->get_default_calendar($data['sensitivity']);
       $response['select'] = html::span('folder-select', $this->gettext('saveincalendar') . '&nbsp;' .
         $calendar_select->show($default_calendar['id']));
     }
     else if ($data['nosave']) {
       $response['select'] = html::tag('input', array('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 = $after = array();
       foreach ($events as $event) {
         // TODO: skip events with free_busy == 'free' ?
         if ($event['uid'] == $data['uid'] || $event['end'] < $day_start || $event['start'] > $day_end)
           continue;
         else if ($event['start'] < $event_start)
           $before[] = $this->mail_agenda_event_row($event);
         else
           $after[] = $this->mail_agenda_event_row($event);
       }
 
       $response['append'] = array(
         'selector' => '.calendar-agenda-preview',
         'replacements' => array(
           '%before%' => !empty($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()
   {
     $success  = false;
     $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);
 
     // search for event if only UID is given
     if ($event = $this->driver->get_event(array('uid' => $uid, '_instance' => $instance), calendar_driver::FILTER_WRITEABLE)) {
       $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($p)
   {
     if ($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 ($invitation['cancelled']) {
           $this->invitestatus = html::div('rsvp-status declined', $itip->gettext('eventcancelled'));
         }
         // save submitted RSVP status
         else if (!empty($_POST['rsvp'])) {
           $status = null;
           foreach (array('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...
           if ($this->rc->user->ID) {
             $this->load_driver();
             $invitation = $itip->get_invitation($token);
 
             // save the event to his/her default calendar if not yet present
             if (!$this->driver->get_event($this->event) && ($calendar = $this->get_default_calendar($invitation['event']['sensitivity']))) {
               $invitation['event']['calendar'] = $calendar['id'];
               if ($this->driver->new_event($invitation['event']))
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'importedsuccessfully', 'vars' => array('calendar' => $calendar['name']))), 'confirmation');
             }
           }
         }
         
         $this->register_handler('plugin.event_inviteform', array($this, 'itip_event_inviteform'));
         $this->register_handler('plugin.event_invitebox', array($this->ui, 'event_invitebox'));
         
         if (!$this->invitestatus) {
           $this->itip->set_rsvp_actions(array('accepted','tentative','declined'));
           $this->register_handler('plugin.event_rsvp_buttons', array($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(array('name' => "_t", 'value' => $this->token));
     return html::tag('form', array('action' => $this->rc->url(array('task' => 'calendar', 'action' => 'attend')), 'method' => 'post', 'noclose' => true) + $attrib) . $hidden->show();
   }
 
   /**
    * 
    */
   private function mail_agenda_event_row($event, $class = '')
   {
     $time = $event['allday'] ? $this->gettext('all-day') :
       $this->rc->format_date($event['start'], $this->rc->config->get('time_format')) . ' - ' .
         $this->rc->format_date($event['end'], $this->rc->config->get('time_format'));
 
     return html::div(rtrim('event-row ' . $class),
       html::span('event-date', $time) .
       html::span('event-title', rcube::Q($event['title']))
     );
   }
   
   /**
    * 
    */
   public function mail_messages_list($p)
   {
     if (in_array('attachment', (array)$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, array('multipart/alternative', 'multipart/mixed'))) {
           // TODO: fetch bodystructure and search for ical parts. Maybe too expensive?
 
           if (!empty($header->structure) && is_array($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 = '';
 
         // 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', $this->rc->format_date($event['start'], $this->rc->config->get('date_format')))
             ) . '%before%' . $this->mail_agenda_event_row($event, 'current') . '%after%');
         }
 
         $html .= html::div('calendar-invitebox',
           $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(array('task' => 'calendar')) . '&view=agendaDay&date=' . $event['start']->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(array(
         'id'         => 'attachmentsavecal',
         'name'       => 'attachmentsavecal',
         'type'       => 'link',
         'wrapper'    => 'li',
         'command'    => 'attachment-save-calendar',
         'class'      => 'icon calendarlink',
         '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);
 
     $error_msg = $this->gettext('errorimportingevent');
     $success = false;
     $delegate = null;
 
     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 events?
     if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
       // forward iTip request to delegatee
       if ($delegate) {
         $rsvpme  = (bool) intval(rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST));
         $comment = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
 
         $d_event = $comment ? array_merge($event, array('comment' => $comment)) : $event;
         $itip    = $this->load_itip();
 
         if ($itip->delegate_to($d_event, $delegate, $rsvpme)) {
           $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
         }
         else {
           $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
         }
 
         // the delegator is set to non-participant, thus save as non-blocking
         $event['free_busy'] = 'free';
       }
 
       // find writeable calendar to store event
       $cal_id = !empty($_REQUEST['_folder']) ? rcube_utils::get_input_value('_folder', rcube_utils::INPUT_POST) : null;
       $dontsave = ($_REQUEST['_folder'] === '' && $event['_method'] == 'REQUEST');
       $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL);
       $calendar = $calendars[$cal_id];
 
       // select default calendar except user explicitly selected 'none'
       if (!$calendar && !$dontsave)
          $calendar = $this->get_default_calendar($event['sensitivity']);
 
       $metadata = array(
         'uid' => $event['uid'],
         '_instance' => $event['_instance'],
         'changed' => is_object($event['changed']) ? $event['changed']->format('U') : 0,
         'sequence' => intval($event['sequence']),
         'fallback' => strtoupper($status),
         'method' => $event['_method'],
         'task' => 'calendar',
       );
 
       // update my attendee status according to submitted method
       if (!empty($status)) {
         $organizer = null;
         $emails = $this->get_user_emails();
         foreach ($event['attendees'] as $i => $attendee) {
           if ($attendee['role'] == 'ORGANIZER') {
             $organizer = $attendee;
           }
           else if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
             $event['attendees'][$i]['status'] = strtoupper($status);
             if (!in_array($event['attendees'][$i]['status'], array('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'][] = array(
             'name' => $sender_identity['name'],
             'email' => $sender_identity['email'],
             'role' => 'OPT-PARTICIPANT',
             'status' => strtoupper($status),
           );
           $metadata['attendee'] = $sender_identity['email'];
         }
       }
       
       // save to calendar
       if ($calendar && $calendar['editable']) {
         // check for existing event with the same UID
         $existing = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL);
 
         if ($existing) {
           // forward savemode for correct updates of recurring events
           $existing['_savemode'] = $savemode ?: $event['_savemode'];
 
           // only update attendee status
           if ($event['_method'] == 'REPLY') {
             // try to identify the attendee using the email sender address
             $existing_attendee = -1;
             $existing_attendee_emails = array();
             foreach ($existing['attendees'] as $i => $attendee) {
               $existing_attendee_emails[] = $attendee['email'];
               if ($event['_sender'] && ($attendee['email'] == $event['_sender'] || $attendee['email'] == $event['_sender_utf'])) {
                 $existing_attendee = $i;
               }
             }
             $event_attendee = null;
             $update_attendees = array();
             foreach ($event['attendees'] as $attendee) {
               if ($event['_sender'] && ($attendee['email'] == $event['_sender'] || $attendee['email'] == $event['_sender_utf'])) {
                 $event_attendee = $attendee;
                 $update_attendees[] = $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'], $event['_sender']) !== false ||
                         stripos($attendee['delegated-from'], $event['_sender_utf']) !== false)) {
                 $update_attendees[] = $attendee;
                 if (!in_array($attendee['email'], $existing_attendee_emails)) {
                   $existing['attendees'][] = $attendee;
                 }
               }
             }
 
             // if delegatee has declined, set delegator's RSVP=True
             if ($event_attendee && $event_attendee['status'] == 'DECLINED' && $event_attendee['delegated-from']) {
               foreach ($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 >= 0 && $event_attendee) {
               $existing['attendees'][$existing_attendee] = $event_attendee;
               $success = $this->driver->update_attendees($existing, $update_attendees);
             }
             // update the entire attendees block
             else if (($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed']) && $event_attendee) {
               $existing['attendees'][] = $event_attendee;
               $success = $this->driver->update_attendees($existing, $update_attendees);
             }
             else {
               $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'];
 
             // preserve my participant status for regular updates
             if (empty($status)) {
               $emails = $this->get_user_emails();
               foreach ($event['attendees'] as $i => $attendee) {
                 if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                   foreach ($existing['attendees'] as $j => $_attendee) {
                     if ($attendee['email'] == $_attendee['email']) {
                       $event['attendees'][$i] = $existing['attendees'][$j];
                       break;
                     }
                   }
                 }
               }
             }
 
             // set status=CANCELLED on CANCEL messages
             if ($event['_method'] == 'CANCEL')
               $event['status'] = 'CANCELLED';
+
+            // update attachments list, allow attachments update only on REQUEST (#5342)
+            if ($event['_method'] == 'REQUEST')
+              $event['deleted_attachments'] = true;
+            else
+              unset($event['attachments']);
+
             // show me as free when declined (#1670)
             if ($status == 'declined' || $event['status'] == 'CANCELLED' || $event_attendee['role'] == 'NON-PARTICIPANT')
               $event['free_busy'] = 'free';
 
             $success = $this->driver->edit_event($event);
           }
           else if (!empty($status)) {
             $existing['attendees'] = $event['attendees'];
             if ($status == 'declined' || $event_attendee['role'] == 'NON-PARTICIPANT')  // show me as free when declined (#1670)
               $existing['free_busy'] = 'free';
             $success = $this->driver->edit_event($existing);
           }
           else
             $error_msg = $this->gettext('newerversionexists');
         }
         else if (!$existing && ($status != 'declined' || $this->rc->config->get('kolab_invitation_calendars'))) {
           if ($status == 'declined' || $event['status'] == 'CANCELLED' || $event_attendee['role'] == 'NON-PARTICIPANT') {
             $event['free_busy'] = 'free';
           }
 
           // if the RSVP reply only refers to a single instance:
           // store unmodified master event with current instance as exception
           if (!empty($instance) && !empty($savemode) && $savemode != 'all') {
             $master = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event');
             if ($master['recurrence'] && !$master['_instance']) {
               // compute recurring events until this instance's date
               if ($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) {
       $message = $event['_method'] == 'REPLY' ? 'attendeupdateesuccess' : ($deleted ? 'successremoval' : ($existing ? 'updatedsuccessfully' : 'importedsuccessfully'));
       $this->rc->output->command('display_message', $this->gettext(array('name' => $message, 'vars' => array('calendar' => $calendar['name']))), 'confirmation');
     }
 
     if ($success || $dontsave) {
       $metadata['calendar'] = $event['calendar'];
       $metadata['nosave'] = $dontsave;
       $metadata['rsvp'] = intval($metadata['rsvp']);
       $metadata['after_action'] = $this->rc->config->get('calendar_itip_after_action', $this->defaults['calendar_itip_after_action']);
       $this->rc->output->command('plugin.itip_message_processed', $metadata);
       $error_msg = null;
     }
     else if ($error_msg) {
       $this->rc->output->command('display_message', $error_msg, 'error');
     }
 
     // send iTip reply
     if ($event['_method'] == 'REQUEST' && $organizer && !$noreply && !in_array(strtolower($organizer['email']), $emails) && !$error_msg) {
       $event['comment'] = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
       $itip = $this->load_itip();
       $itip->set_sender_email($reply_sender);
       if ($itip->send_itip_message($event, 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status))
         $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $organizer['name'] ? $organizer['name'] : $organizer['email']))), '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'))
         $this->rc->output->command('display_message', $this->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $attendee['name'] ? $attendee['name'] : $attendee['email']))), '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, $mime_id);
       if ($part->ctype_parameters['charset'])
         $charset = $part->ctype_parameters['charset'];
 //      $headers = $imap->get_message_headers($uid);
 
       if ($part) {
         $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 = $calendars[$cal_id] ?: $this->get_default_calendar($event['sensitivity']);
         if ($calendar && $calendar['editable'] && $event['_type'] == 'event') {
           $event['calendar'] = $calendar['id'];
 
           if (!$this->driver->get_event($event['uid'], calendar_driver::FILTER_WRITEABLE)) {
             $success += (bool)$this->driver->new_event($event);
           }
           else {
             $existing++;
           }
         }
       }
     }
 
     if ($success) {
       $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('errorimportingevent'), 'error');
     }
   }
 
   /**
    * Read email message and return contents for a new event based on that message
    */
   public function mail_message2event()
   {
     $uid   = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
     $mbox  = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
     $event = array();
 
     // establish imap connection
     $imap = $this->rc->get_storage();
     $imap->set_folder($mbox);
     $message = new rcube_message($uid);
 
     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)) {
         $event['links'] = array($msgref);
       }
       // copy mail attachments to event
       else if ($message->attachments) {
         $eventid = 'cal-';
         if (!is_array($_SESSION[self::SESSION_KEY]) || $_SESSION[self::SESSION_KEY]['id'] != $eventid) {
           $_SESSION[self::SESSION_KEY] = array();
           $_SESSION[self::SESSION_KEY]['id'] = $eventid;
           $_SESSION[self::SESSION_KEY]['attachments'] = array();
         }
 
         foreach ((array)$message->attachments as $part) {
           $attachment = array(
             'data' => $imap->get_message_part($uid, $part->mime_id, $part),
             'size' => $part->size,
             'name' => $part->filename,
             'mimetype' => $part->mimetype,
             'group' => $eventid,
           );
 
           $attachment = $this->rc->plugins->exec_hook('attachment_save', $attachment);
 
           if ($attachment['status'] && !$attachment['abort']) {
             $id = $attachment['id'];
             $attachment['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
             // store new attachment in session
             unset($attachment['status'], $attachment['abort'], $attachment['data']);
             $_SESSION[self::SESSION_KEY]['attachments'][$id] = $attachment;
 
             $attachment['id'] = 'rcmfile' . $attachment['id'];  // add prefix to consider it 'new'
             $event['attachments'][] = $attachment;
           }
         }
       }
       
       $this->rc->output->command('plugin.mail2event_dialog', $event);
     }
     else {
       $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
     }
     
     $this->rc->output->send();
   }
 
   /**
    * 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(array('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');
         file_put_contents($tmp_path, $this->get_ical()->export(array($event), '', false, array($this->driver, 'get_attachment_body')));
 
         $args['attachments'][] = array('path' => $tmp_path, 'name' => $filename . '.ics', 'mimetype' => 'text/calendar');
         $args['param']['subject'] = $event['title'];
       }
     }
 
     return $args;
   }
 
 
   /**
    * Get a list of email addresses of the current user (from login and identities)
    */
   public function get_user_emails()
   {
     return $this->lib->get_user_emails();
   }
 
 
   /**
    * Build an absolute URL with the given parameters
    */
   public function get_url($param = array())
   {
     $param += array('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->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;
   }
 
 }
diff --git a/plugins/calendar/drivers/kolab/kolab_driver.php b/plugins/calendar/drivers/kolab/kolab_driver.php
index 0eafc3bd..4b7861b7 100644
--- a/plugins/calendar/drivers/kolab/kolab_driver.php
+++ b/plugins/calendar/drivers/kolab/kolab_driver.php
@@ -1,2546 +1,2507 @@
 <?php
 
 /**
  * Kolab driver for the Calendar plugin
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  * @author Aleksander Machniak <machniak@kolabsys.com>
  *
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class kolab_driver extends calendar_driver
 {
   const INVITATIONS_CALENDAR_PENDING  = '--invitation--pending';
   const INVITATIONS_CALENDAR_DECLINED = '--invitation--declined';
 
   // features this backend supports
   public $alarms = true;
   public $attendees = true;
   public $freebusy = true;
   public $attachments = true;
   public $undelete = true;
   public $alarm_types = array('DISPLAY','AUDIO');
   public $categoriesimmutable = true;
 
   private $rc;
   private $cal;
   private $calendars;
   private $has_writeable = false;
   private $freebusy_trigger = false;
   private $bonnie_api = false;
 
   /**
    * Default constructor
    */
   public function __construct($cal)
   {
     $cal->require_plugin('libkolab');
 
     // load helper classes *after* libkolab has been loaded (#3248)
     require_once(dirname(__FILE__) . '/kolab_calendar.php');
     require_once(dirname(__FILE__) . '/kolab_user_calendar.php');
     require_once(dirname(__FILE__) . '/kolab_invitation_calendar.php');
 
     $this->cal = $cal;
     $this->rc  = $cal->rc;
 
     $this->cal->register_action('push-freebusy', array($this, 'push_freebusy'));
     $this->cal->register_action('calendar-acl', array($this, 'calendar_acl'));
 
     $this->freebusy_trigger = $this->rc->config->get('calendar_freebusy_trigger', false);
 
     if (kolab_storage::$version == '2.0') {
         $this->alarm_types = array('DISPLAY');
         $this->alarm_absolute = false;
     }
 
     // get configuration for the Bonnie API
     $this->bonnie_api = libkolab::get_bonnie_api();
 
     // calendar uses fully encoded identifiers
     kolab_storage::$encode_ids = true;
   }
 
 
   /**
    * Read available calendars from server
    */
   private function _read_calendars()
   {
     // already read sources
     if (isset($this->calendars))
       return $this->calendars;
 
     // get all folders that have "event" type, sorted by namespace/name
     $folders = kolab_storage::sort_folders(kolab_storage::get_folders('event') + kolab_storage::get_user_folders('event', true));
 
     $this->calendars = array();
     foreach ($folders as $folder) {
       if ($folder instanceof kolab_storage_folder_user) {
         $calendar = new kolab_user_calendar($folder, $this->cal);
         $calendar->subscriptions = count($folder->children) > 0;
       }
       else {
         $calendar = new kolab_calendar($folder->name, $this->cal);
       }
 
       if ($calendar->ready) {
         $this->calendars[$calendar->id] = $calendar;
         if ($calendar->editable)
           $this->has_writeable = true;
       }
     }
 
     return $this->calendars;
   }
 
   /**
    * Get a list of available calendars from this source
    *
    * @param integer $filter Bitmask defining filter criterias
    * @param object $tree   Reference to hierarchical folder tree object
    *
    * @return array List of calendars
    */
   public function list_calendars($filter = 0, &$tree = null)
   {
     $this->_read_calendars();
 
     // attempt to create a default calendar for this user
     if (!$this->has_writeable) {
       if ($this->create_calendar(array('name' => 'Calendar', 'color' => 'cc0000'))) {
         unset($this->calendars);
         $this->_read_calendars();
       }
     }
 
     $delim = $this->rc->get_storage()->get_hierarchy_delimiter();
     $folders = $this->filter_calendars($filter);
     $calendars = array();
 
     // include virtual folders for a full folder tree
     if (!is_null($tree))
       $folders = kolab_storage::folder_hierarchy($folders, $tree);
 
     foreach ($folders as $id => $cal) {
       $fullname = $cal->get_name();
       $listname = $cal->get_foldername();
       $imap_path = explode($delim, $cal->name);
 
       // find parent
       do {
         array_pop($imap_path);
         $parent_id = kolab_storage::folder_id(join($delim, $imap_path));
       }
       while (count($imap_path) > 1 && !$this->calendars[$parent_id]);
 
       // restore "real" parent ID
       if ($parent_id && !$this->calendars[$parent_id]) {
           $parent_id = kolab_storage::folder_id($cal->get_parent());
       }
 
       // turn a kolab_storage_folder object into a kolab_calendar
       if ($cal instanceof kolab_storage_folder) {
           $cal = new kolab_calendar($cal->name, $this->cal);
           $this->calendars[$cal->id] = $cal;
       }
 
       // special handling for user or virtual folders
       if ($cal instanceof kolab_storage_folder_user) {
         $calendars[$cal->id] = array(
           'id'       => $cal->id,
           'name'     => $fullname,
           'listname' => $listname,
           'editname' => $cal->get_foldername(),
           'color'    => $cal->get_color(),
           'active'   => $cal->is_active(),
           'title'    => $cal->get_owner(),
           'owner'    => $cal->get_owner(),
           'history'  => false,
           'virtual'  => false,
           'editable' => false,
           'group'     => 'other',
           'class'     => 'user',
           'removable' => true,
         );
       }
       else if ($cal->virtual) {
         $calendars[$cal->id] = array(
           'id' => $cal->id,
           'name' => $fullname,
           'listname' => $listname,
           'editname' => $cal->get_foldername(),
           'virtual'  => true,
           'editable' => false,
           'group'     => $cal->get_namespace(),
           'class'     => 'folder',
         );
       }
       else {
         $calendars[$cal->id] = array(
           'id'       => $cal->id,
           'name'     => $fullname,
           'listname' => $listname,
           'editname' => $cal->get_foldername(),
           'title'    => $cal->get_title(),
           'color'    => $cal->get_color(),
           'editable' => $cal->editable,
           'rights'    => $cal->rights,
           'showalarms' => $cal->alarms,
           'history'  => !empty($this->bonnie_api),
           'group'    => $cal->get_namespace(),
           'default'  => $cal->default,
           'active'   => $cal->is_active(),
           'owner'    => $cal->get_owner(),
           'children' => true,  // TODO: determine if that folder indeed has child folders
           'parent'   => $parent_id,
           'subtype'  => $cal->subtype,
           'caldavurl' => $cal->get_caldav_url(),
           'removable' => !$cal->default,
         );
       }
 
       if ($cal->subscriptions) {
         $calendars[$cal->id]['subscribed'] = $cal->is_subscribed();
       }
     }
 
     // list virtual calendars showing invitations
     if ($this->rc->config->get('kolab_invitation_calendars')) {
       foreach (array(self::INVITATIONS_CALENDAR_PENDING, self::INVITATIONS_CALENDAR_DECLINED) as $id) {
         $cal = new kolab_invitation_calendar($id, $this->cal);
         $this->calendars[$cal->id] = $cal;
         if (!($filter & self::FILTER_ACTIVE) || $cal->is_active()) {
           $calendars[$id] = array(
             'id'       => $cal->id,
             'name'     => $cal->get_name(),
             'listname' => $cal->get_name(),
             'editname' => $cal->get_foldername(),
             'title'    => $cal->get_title(),
             'color'    => $cal->get_color(),
             'editable' => $cal->editable,
             'rights'    => $cal->rights,
             'showalarms' => $cal->alarms,
             'history'  => !empty($this->bonnie_api),
             'group'    => 'x-invitations',
             'default'  => false,
             'active'   => $cal->is_active(),
             'owner'    => $cal->get_owner(),
             'children' => false,
           );
 
           if ($id == self::INVITATIONS_CALENDAR_PENDING) {
             $calendars[$id]['counts'] = true;
           }
 
           if (is_object($tree)) {
             $tree->children[] = $cal;
           }
         }
       }
     }
 
     // append the virtual birthdays calendar
     if ($this->rc->config->get('calendar_contact_birthdays', false)) {
       $id = self::BIRTHDAY_CALENDAR_ID;
       $prefs = $this->rc->config->get('kolab_calendars', array());  // read local prefs
       if (!($filter & self::FILTER_ACTIVE) || $prefs[$id]['active']) {
         $calendars[$id] = array(
           'id'         => $id,
           'name'       => $this->cal->gettext('birthdays'),
           'listname'   => $this->cal->gettext('birthdays'),
           'color'      => $prefs[$id]['color'] ?: '87CEFA',
           'active'     => (bool)$prefs[$id]['active'],
           'showalarms' => (bool)$this->rc->config->get('calendar_birthdays_alarm_type'),
           'group'      => 'x-birthdays',
           'editable'  => false,
           'default'    => false,
           'children'   => false,
           'history'    => false,
         );
       }
     }
 
     return $calendars;
   }
 
   /**
    * Get list of calendars according to specified filters
    *
    * @param integer Bitmask defining restrictions. See FILTER_* constants for possible values.
    *
    * @return array List of calendars
    */
   protected function filter_calendars($filter)
   {
     $this->_read_calendars();
 
     $calendars = array();
 
     $plugin = $this->rc->plugins->exec_hook('calendar_list_filter', array(
       'list'      => $this->calendars,
       'calendars' => $calendars,
       'filter'    => $filter,
       'editable'  => ($filter & self::FILTER_WRITEABLE),
       'insert'    => ($filter & self::FILTER_INSERTABLE),
       'active'    => ($filter & self::FILTER_ACTIVE),
       'personal'  => ($filter & self::FILTER_PERSONAL)
     ));
 
     if ($plugin['abort']) {
       return $plugin['calendars'];
     }
 
     foreach ($this->calendars as $cal) {
       if (!$cal->ready) {
         continue;
       }
       if (($filter & self::FILTER_WRITEABLE) && !$cal->editable) {
         continue;
       }
       if (($filter & self::FILTER_INSERTABLE) && !$cal->insert) {
         continue;
       }
       if (($filter & self::FILTER_ACTIVE) && !$cal->is_active()) {
         continue;
       }
       if (($filter & self::FILTER_PRIVATE) && $cal->subtype != 'private') {
         continue;
       }
       if (($filter & self::FILTER_CONFIDENTIAL) && $cal->subtype != 'confidential') {
         continue;
       }
       if (($filter & self::FILTER_PERSONAL) && $cal->get_namespace() != 'personal') {
         continue;
       }
       $calendars[$cal->id] = $cal;
     }
 
     return $calendars;
   }
 
 
   /**
    * Get the kolab_calendar instance for the given calendar ID
    *
    * @param string Calendar identifier (encoded imap folder name)
    * @return object kolab_calendar Object nor null if calendar doesn't exist
    */
   public function get_calendar($id)
   {
     $this->_read_calendars();
 
     // create calendar object if necesary
     if (!$this->calendars[$id]) {
       if (in_array($id, array(self::INVITATIONS_CALENDAR_PENDING, self::INVITATIONS_CALENDAR_DECLINED))) {
         $this->calendars[$id] = new kolab_invitation_calendar($id, $this->cal);
       }
       else if ($id !== self::BIRTHDAY_CALENDAR_ID) {
         $calendar = kolab_calendar::factory($id, $this->cal);
         if ($calendar->ready) {
           $this->calendars[$calendar->id] = $calendar;
         }
       }
     }
 
     return $this->calendars[$id];
   }
 
   /**
    * Create a new calendar assigned to the current user
    *
    * @param array Hash array with calendar properties
    *    name: Calendar name
    *   color: The color of the calendar
    * @return mixed ID of the calendar on success, False on error
    */
   public function create_calendar($prop)
   {
     $prop['type'] = 'event';
     $prop['active'] = true;
     $prop['subscribed'] = true;
     $folder = kolab_storage::folder_update($prop);
 
     if ($folder === false) {
       $this->last_error = $this->cal->gettext(kolab_storage::$last_error);
       return false;
     }
 
     // create ID
     $id = kolab_storage::folder_id($folder);
 
     // save color in user prefs (temp. solution)
     $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
 
     if (isset($prop['color']))
       $prefs['kolab_calendars'][$id]['color'] = $prop['color'];
     if (isset($prop['showalarms']))
       $prefs['kolab_calendars'][$id]['showalarms'] = $prop['showalarms'] ? true : false;
 
     if ($prefs['kolab_calendars'][$id])
       $this->rc->user->save_prefs($prefs);
 
     return $id;
   }
 
 
   /**
    * Update properties of an existing calendar
    *
    * @see calendar_driver::edit_calendar()
    */
   public function edit_calendar($prop)
   {
     if ($prop['id'] && ($cal = $this->get_calendar($prop['id']))) {
       $id = $cal->update($prop);
     }
     else {
       $id = $prop['id'];
     }
 
     // fallback to local prefs
     $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
     unset($prefs['kolab_calendars'][$prop['id']]['color'], $prefs['kolab_calendars'][$prop['id']]['showalarms']);
 
     if (isset($prop['color']))
       $prefs['kolab_calendars'][$id]['color'] = $prop['color'];
 
     if (isset($prop['showalarms']) && $id == self::BIRTHDAY_CALENDAR_ID)
       $prefs['calendar_birthdays_alarm_type'] = $prop['showalarms'] ? $this->alarm_types[0] : '';
     else if (isset($prop['showalarms']))
       $prefs['kolab_calendars'][$id]['showalarms'] = $prop['showalarms'] ? true : false;
 
     if (!empty($prefs['kolab_calendars'][$id]))
       $this->rc->user->save_prefs($prefs);
 
     return true;
   }
 
 
   /**
    * Set active/subscribed state of a calendar
    *
    * @see calendar_driver::subscribe_calendar()
    */
   public function subscribe_calendar($prop)
   {
     if ($prop['id'] && ($cal = $this->get_calendar($prop['id'])) && is_object($cal->storage)) {
       $ret = false;
       if (isset($prop['permanent']))
         $ret |= $cal->storage->subscribe(intval($prop['permanent']));
       if (isset($prop['active']))
         $ret |= $cal->storage->activate(intval($prop['active']));
 
       // apply to child folders, too
       if ($prop['recursive']) {
         foreach ((array)kolab_storage::list_folders($cal->storage->name, '*', 'event') as $subfolder) {
           if (isset($prop['permanent']))
             ($prop['permanent'] ? kolab_storage::folder_subscribe($subfolder) : kolab_storage::folder_unsubscribe($subfolder));
           if (isset($prop['active']))
             ($prop['active'] ? kolab_storage::folder_activate($subfolder) : kolab_storage::folder_deactivate($subfolder));
         }
       }
       return $ret;
     }
     else {
       // save state in local prefs
       $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
       $prefs['kolab_calendars'][$prop['id']]['active'] = (bool)$prop['active'];
       $this->rc->user->save_prefs($prefs);
       return true;
     }
 
     return false;
   }
 
 
   /**
    * Delete the given calendar with all its contents
    *
    * @see calendar_driver::delete_calendar()
    */
   public function delete_calendar($prop)
   {
     if ($prop['id'] && ($cal = $this->get_calendar($prop['id']))) {
       $folder = $cal->get_realname();
       // TODO: unsubscribe if no admin rights
       if (kolab_storage::folder_delete($folder)) {
         // remove color in user prefs (temp. solution)
         $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
         unset($prefs['kolab_calendars'][$prop['id']]);
 
         $this->rc->user->save_prefs($prefs);
         return true;
       }
       else
         $this->last_error = kolab_storage::$last_error;
     }
 
     return false;
   }
 
 
   /**
    * Search for shared or otherwise not listed calendars the user has access
    *
    * @param string Search string
    * @param string Section/source to search
    * @return array List of calendars
    */
   public function search_calendars($query, $source)
   {
     if (!kolab_storage::setup())
       return array();
 
     $this->calendars = array();
     $this->search_more_results = false;
 
     // find unsubscribed IMAP folders that have "event" type
     if ($source == 'folders') {
       foreach ((array)kolab_storage::search_folders('event', $query, array('other')) as $folder) {
         $calendar = new kolab_calendar($folder->name, $this->cal);
         $this->calendars[$calendar->id] = $calendar;
       }
     }
     // find other user's virtual calendars
     else if ($source == 'users') {
       $limit = $this->rc->config->get('autocomplete_max', 15) * 2;  // we have slightly more space, so display twice the number
       foreach (kolab_storage::search_users($query, 0, array(), $limit, $count) as $user) {
         $calendar = new kolab_user_calendar($user, $this->cal);
         $this->calendars[$calendar->id] = $calendar;
 
         // search for calendar folders shared by this user
         foreach (kolab_storage::list_user_folders($user, 'event', false) as $foldername) {
           $cal = new kolab_calendar($foldername, $this->cal);
           $this->calendars[$cal->id] = $cal;
           $calendar->subscriptions = true;
         }
       }
 
       if ($count > $limit) {
         $this->search_more_results = true;
       }
     }
 
     // don't list the birthday calendar
     $this->rc->config->set('calendar_contact_birthdays', false);
     $this->rc->config->set('kolab_invitation_calendars', false);
 
     return $this->list_calendars();
   }
 
 
   /**
    * Fetch a single event
    *
    * @see calendar_driver::get_event()
    * @return array Hash array with event properties, false if not found
    */
   public function get_event($event, $scope = 0, $full = false)
   {
     if (is_array($event)) {
       $id = $event['id'] ?: $event['uid'];
       $cal = $event['calendar'];
 
       // we're looking for a recurring instance: expand the ID to our internal convention for recurring instances
       if (!$event['id'] && $event['_instance']) {
         $id .= '-' . $event['_instance'];
       }
     }
     else {
       $id = $event;
     }
 
     if ($cal) {
       if ($storage = $this->get_calendar($cal)) {
         $result = $storage->get_event($id);
         return self::to_rcube_event($result);
       }
       // get event from the address books birthday calendar
       else if ($cal == self::BIRTHDAY_CALENDAR_ID) {
         return $this->get_birthday_event($id);
       }
     }
     // iterate over all calendar folders and search for the event ID
     else {
       foreach ($this->filter_calendars($scope) as $calendar) {
         if ($result = $calendar->get_event($id)) {
           return self::to_rcube_event($result);
         }
       }
     }
 
     return false;
   }
 
   /**
    * Add a single event to the database
    *
    * @see calendar_driver::new_event()
    */
   public function new_event($event)
   {
     if (!$this->validate($event))
       return false;
 
     $event = self::from_rcube_event($event);
 
     if (!$event['calendar']) {
       $this->_read_calendars();
       $event['calendar'] = reset(array_keys($this->calendars));
     }
 
     if ($storage = $this->get_calendar($event['calendar'])) {
       // if this is a recurrence instance, append as exception to an already existing object for this UID
       if (!empty($event['recurrence_date']) && ($master = $storage->get_event($event['uid']))) {
         self::add_exception($master, $event);
         $success = $storage->update_event($master);
       }
       else {
         $success = $storage->insert_event($event);
       }
 
       if ($success && $this->freebusy_trigger) {
         $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
         $this->freebusy_trigger = false; // disable after first execution (#2355)
       }
       
       return $success;
     }
 
     return false;
   }
 
   /**
    * Update an event entry with the given data
    *
    * @see calendar_driver::new_event()
    * @return boolean True on success, False on error
    */
   public function edit_event($event)
   {
      if (!($storage = $this->get_calendar($event['calendar'])))
        return false;
 
     return $this->update_event(self::from_rcube_event($event, $storage->get_event($event['id'])));
   }
 
   /**
    * Extended event editing with possible changes to the argument
    *
    * @param array  Hash array with event properties
    * @param string New participant status
    * @param array  List of hash arrays with updated attendees
    * @return boolean True on success, False on error
    */
   public function edit_rsvp(&$event, $status, $attendees)
   {
     $update_event = $event;
 
     // apply changes to master (and all exceptions)
     if ($event['_savemode'] == 'all' && $event['recurrence_id']) {
       if ($storage = $this->get_calendar($event['calendar'])) {
         $update_event = $storage->get_event($event['recurrence_id']);
         $update_event['_savemode'] = $event['_savemode'];
         $update_event['id'] = $update_event['uid'];
         unset($update_event['recurrence_id']);
         calendar::merge_attendee_data($update_event, $attendees);
       }
     }
 
     if ($ret = $this->update_attendees($update_event, $attendees)) {
       // replace with master event (for iTip reply)
       $event = self::to_rcube_event($update_event);
 
       // re-assign to the according (virtual) calendar
       if ($this->rc->config->get('kolab_invitation_calendars')) {
         if (strtoupper($status) == 'DECLINED')
           $event['calendar'] = self::INVITATIONS_CALENDAR_DECLINED;
         else if (strtoupper($status) == 'NEEDS-ACTION')
           $event['calendar'] = self::INVITATIONS_CALENDAR_PENDING;
         else if ($event['_folder_id'])
           $event['calendar'] = $event['_folder_id'];
       }
     }
 
     return $ret;
   }
 
   /**
    * Update the participant status for the given attendees
    *
    * @see calendar_driver::update_attendees()
    */
   public function update_attendees(&$event, $attendees)
   {
     // for this-and-future updates, merge the updated attendees onto all exceptions in range
     if (($event['_savemode'] == 'future' && $event['recurrence_id']) || (!empty($event['recurrence']) && !$event['recurrence_id'])) {
       if (!($storage = $this->get_calendar($event['calendar'])))
         return false;
 
       // load master event
       $master = $event['recurrence_id'] ? $storage->get_event($event['recurrence_id']) : $event;
 
       // apply attendee update to each existing exception
       if ($master['recurrence'] && !empty($master['recurrence']['EXCEPTIONS'])) {
         $saved = false;
         foreach ($master['recurrence']['EXCEPTIONS'] as $i => $exception) {
           // merge the new event properties onto future exceptions
           if ($exception['_instance'] >= strval($event['_instance'])) {
             calendar::merge_attendee_data($master['recurrence']['EXCEPTIONS'][$i], $attendees);
           }
           // update a specific instance
           if ($exception['_instance'] == $event['_instance'] && $exception['thisandfuture']) {
             $saved = true;
           }
         }
 
         // add the given event as new exception
         if (!$saved && $event['id'] != $master['id']) {
           $event['thisandfuture'] = true;
           $master['recurrence']['EXCEPTIONS'][] = $event;
         }
 
         // set link to top-level exceptions
         $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];
 
         return $this->update_event($master);
       }
     }
 
     // just update the given event (instance)
     return $this->update_event($event);
   }
 
   /**
    * Move a single event
    *
    * @see calendar_driver::move_event()
    * @return boolean True on success, False on error
    */
   public function move_event($event)
   {
     if (($storage = $this->get_calendar($event['calendar'])) && ($ev = $storage->get_event($event['id']))) {
       unset($ev['sequence']);
       self::clear_attandee_noreply($ev);
       return $this->update_event($event + $ev);
     }
 
     return false;
   }
 
   /**
    * Resize a single event
    *
    * @see calendar_driver::resize_event()
    * @return boolean True on success, False on error
    */
   public function resize_event($event)
   {
     if (($storage = $this->get_calendar($event['calendar'])) && ($ev = $storage->get_event($event['id']))) {
       unset($ev['sequence']);
       self::clear_attandee_noreply($ev);
       return $this->update_event($event + $ev);
     }
 
     return false;
   }
 
   /**
    * Remove a single event
    *
    * @param array   Hash array with event properties:
    *      id: Event identifier
    * @param boolean Remove record(s) irreversible (mark as deleted otherwise)
    *
    * @return boolean True on success, False on error
    */
   public function remove_event($event, $force = true)
   {
     $ret = true;
     $success = false;
     $savemode = $event['_savemode'];
     $decline  = $event['_decline'];
 
     if (($storage = $this->get_calendar($event['calendar'])) && ($event = $storage->get_event($event['id']))) {
       $event['_savemode'] = $savemode;
       $savemode = 'all';
       $master = $event;
 
       $this->rc->session->remove('calendar_restore_event_data');
 
       // read master if deleting a recurring event
       if ($event['recurrence'] || $event['recurrence_id'] || $event['isexception']) {
         $master = $storage->get_event($event['uid']);
         $savemode = $event['_savemode'] ?: ($event['_instance'] || $event['isexception'] ? 'current' : 'all');
 
         // force 'current' mode for single occurrences stored as exception
         if (!$event['recurrence'] && !$event['recurrence_id'] && $event['isexception'])
           $savemode = 'current';
       }
 
       // removing an exception instance
       if (($event['recurrence_id'] || $event['isexception']) && is_array($master['exceptions'])) {
         foreach ($master['exceptions'] as $i => $exception) {
           if ($exception['_instance'] == $event['_instance']) {
             unset($master['exceptions'][$i]);
             // set event date back to the actual occurrence
             if ($exception['recurrence_date'])
               $event['start'] = $exception['recurrence_date'];
           }
         }
 
         if (is_array($master['recurrence'])) {
           $master['recurrence']['EXCEPTIONS'] = &$master['exceptions'];
         }
       }
 
       switch ($savemode) {
         case 'current':
           $_SESSION['calendar_restore_event_data'] = $master;
 
           // removing the first instance => just move to next occurence
           if ($master['recurrence'] && $event['_instance'] == libcalendaring::recurrence_instance_identifier($master)) {
             $recurring = reset($storage->get_recurring_events($event, $event['start'], null, $event['id'].'-1'));
 
             // no future instances found: delete the master event (bug #1677)
             if (!$recurring['start']) {
               $success = $storage->delete_event($master, $force);
               break;
             }
 
             $master['start'] = $recurring['start'];
             $master['end'] = $recurring['end'];
             if ($master['recurrence']['COUNT'])
               $master['recurrence']['COUNT']--;
           }
           // remove the matching RDATE entry
           else if ($master['recurrence']['RDATE']) {
             foreach ($master['recurrence']['RDATE'] as $j => $rdate) {
               if ($rdate->format('Ymd') == $event['start']->format('Ymd')) {
                 unset($master['recurrence']['RDATE'][$j]);
                 break;
               }
             }
           }
           else {  // add exception to master event
             $master['recurrence']['EXDATE'][] = $event['start'];
           }
           $success = $storage->update_event($master);
           break;
 
         case 'future':
           $master['_instance'] = libcalendaring::recurrence_instance_identifier($master);
           if ($master['_instance'] != $event['_instance']) {
             $_SESSION['calendar_restore_event_data'] = $master;
             
             // set until-date on master event
             $master['recurrence']['UNTIL'] = clone $event['start'];
             $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
             unset($master['recurrence']['COUNT']);
 
             // if all future instances are deleted, remove recurrence rule entirely (bug #1677)
             if ($master['recurrence']['UNTIL']->format('Ymd') == $master['start']->format('Ymd')) {
               $master['recurrence'] = array();
             }
             // remove matching RDATE entries
             else if ($master['recurrence']['RDATE']) {
               foreach ($master['recurrence']['RDATE'] as $j => $rdate) {
                 if ($rdate->format('Ymd') == $event['start']->format('Ymd')) {
                   $master['recurrence']['RDATE'] = array_slice($master['recurrence']['RDATE'], 0, $j);
                   break;
                 }
               }
             }
 
             $success = $storage->update_event($master);
             $ret = $master['uid'];
             break;
           }
 
         default:  // 'all' is default
           // removing the master event with loose exceptions (not recurring though)
           if (!empty($event['recurrence_date']) && empty($master['recurrence']) && !empty($master['exceptions'])) {
             // make the first exception the new master
             $newmaster = array_shift($master['exceptions']);
             $newmaster['exceptions'] = $master['exceptions'];
             $newmaster['_attachments'] = $master['_attachments'];
             $newmaster['_mailbox'] = $master['_mailbox'];
             $newmaster['_msguid'] = $master['_msguid'];
 
             $success = $storage->update_event($newmaster);
           }
           else if ($decline && $this->rc->config->get('kolab_invitation_calendars')) {
             // don't delete but set PARTSTAT=DECLINED
             if ($this->cal->lib->set_partstat($master, 'DECLINED')) {
               $success = $storage->update_event($master);
             }
           }
 
           if (!$success)
             $success = $storage->delete_event($master, $force);
           break;
       }
     }
     
     if ($success && $this->freebusy_trigger)
       $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
 
     return $success ? $ret : false;
   }
 
   /**
    * Restore a single deleted event
    *
    * @param array Hash array with event properties:
    *      id: Event identifier
    * @return boolean True on success, False on error
    */
   public function restore_event($event)
   {
     if ($storage = $this->get_calendar($event['calendar'])) {
       if (!empty($_SESSION['calendar_restore_event_data']))
         $success = $storage->update_event($_SESSION['calendar_restore_event_data']);
       else
         $success = $storage->restore_event($event);
       
       if ($success && $this->freebusy_trigger)
         $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
       
       return $success;
     }
 
     return false;
   }
 
   /**
    * Wrapper to update an event object depending on the given savemode
    */
   private function update_event($event)
   {
     if (!($storage = $this->get_calendar($event['calendar'])))
       return false;
 
     // move event to another folder/calendar
     if ($event['_fromcalendar'] && $event['_fromcalendar'] != $event['calendar']) {
       if (!($fromcalendar = $this->get_calendar($event['_fromcalendar'])))
         return false;
 
       $old = $fromcalendar->get_event($event['id']);
 
       if ($event['_savemode'] != 'new') {
         if (!$fromcalendar->storage->move($old['uid'], $storage->storage)) {
           return false;
         }
 
         $fromcalendar = $storage;
       }
     }
     else
       $fromcalendar = $storage;
 
     $success = false;
     $savemode = 'all';
     $attachments = array();
     $old = $master = $storage->get_event($event['id']);
 
     if (!$old || !$old['start']) {
       rcube::raise_error(array(
         'code' => 600, 'type' => 'php',
         'file' => __FILE__, 'line' => __LINE__,
         'message' => "Failed to load event object to update: id=" . $event['id']),
         true, false);
       return false;
     }
 
     // modify a recurring event, check submitted savemode to do the right things
     if ($old['recurrence'] || $old['recurrence_id'] || $old['isexception']) {
       $master = $storage->get_event($old['uid']);
       $savemode = $event['_savemode'] ?: ($old['recurrence_id'] || $old['isexception'] ? 'current' : 'all');
 
       // this-and-future on the first instance equals to 'all'
       if ($savemode == 'future' && $master['start'] && $old['_instance'] == libcalendaring::recurrence_instance_identifier($master))
         $savemode = 'all';
       // force 'current' mode for single occurrences stored as exception
       else if (!$old['recurrence'] && !$old['recurrence_id'] && $old['isexception'])
         $savemode = 'current';
     }
 
     // check if update affects scheduling and update attendee status accordingly
     $reschedule = $this->check_scheduling($event, $old, true);
 
     // keep saved exceptions (not submitted by the client)
     if ($old['recurrence']['EXDATE'] && !isset($event['recurrence']['EXDATE']))
       $event['recurrence']['EXDATE'] = $old['recurrence']['EXDATE'];
     if (isset($event['recurrence']['EXCEPTIONS']))
       $with_exceptions = true;  // exceptions already provided (e.g. from iCal import)
     else if ($old['recurrence']['EXCEPTIONS'])
       $event['recurrence']['EXCEPTIONS'] = $old['recurrence']['EXCEPTIONS'];
     else if ($old['exceptions'])
       $event['exceptions'] = $old['exceptions'];
 
     // remove some internal properties which should not be saved
     unset($event['_savemode'], $event['_fromcalendar'], $event['_identity'], $event['_owner'],
         $event['_notify'], $event['_method'], $event['_sender'], $event['_sender_utf'], $event['_size']);
 
     switch ($savemode) {
       case 'new':
         // save submitted data as new (non-recurring) event
         $event['recurrence'] = array();
         $event['_copyfrom'] = $master['_msguid'];
         $event['_mailbox'] = $master['_mailbox'];
         $event['uid'] = $this->cal->generate_uid();
         unset($event['recurrence_id'], $event['recurrence_date'], $event['_instance'], $event['id']);
 
         // copy attachment metadata to new event
         $event = self::from_rcube_event($event, $master);
 
         self::clear_attandee_noreply($event);
         if ($success = $storage->insert_event($event))
           $success = $event['uid'];
         break;
 
       case 'future':
         // create a new recurring event
         $event['_copyfrom'] = $master['_msguid'];
         $event['_mailbox'] = $master['_mailbox'];
         $event['uid'] = $this->cal->generate_uid();
         unset($event['recurrence_id'], $event['recurrence_date'], $event['_instance'], $event['id']);
 
         // copy attachment metadata to new event
         $event = self::from_rcube_event($event, $master);
 
         // remove recurrence exceptions on re-scheduling
         if ($reschedule) {
           unset($event['recurrence']['EXCEPTIONS'], $event['exceptions'], $master['recurrence']['EXDATE']);
         }
         else if (is_array($event['recurrence']['EXCEPTIONS'])) {
           // only keep relevant exceptions
           $event['recurrence']['EXCEPTIONS'] = array_filter($event['recurrence']['EXCEPTIONS'], function($exception) use ($event) {
             return $exception['start'] > $event['start'];
           });
           if (is_array($event['recurrence']['EXDATE'])) {
             $event['recurrence']['EXDATE'] = array_filter($event['recurrence']['EXDATE'], function($exdate) use ($event) {
               return $exdate > $event['start'];
             });
           }
           // set link to top-level exceptions
           $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
         }
 
         // compute remaining occurrences
         if ($event['recurrence']['COUNT']) {
           if (!$old['_count'])
             $old['_count'] = $this->get_recurrence_count($master, $old['start']);
           $event['recurrence']['COUNT'] -= intval($old['_count']);
         }
 
         // remove fixed weekday when date changed
         if ($old['start']->format('Y-m-d') != $event['start']->format('Y-m-d')) {
           if (strlen($event['recurrence']['BYDAY']) == 2)
             unset($event['recurrence']['BYDAY']);
           if ($old['recurrence']['BYMONTH'] == $old['start']->format('n'))
             unset($event['recurrence']['BYMONTH']);
         }
 
         // set until-date on master event
         $master['recurrence']['UNTIL'] = clone $old['start'];
         $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
         unset($master['recurrence']['COUNT']);
 
         // remove all exceptions after $event['start']
         if (is_array($master['recurrence']['EXCEPTIONS'])) {
           $master['recurrence']['EXCEPTIONS'] = array_filter($master['recurrence']['EXCEPTIONS'], function($exception) use ($event) {
             return $exception['start'] < $event['start'];
           });
           // set link to top-level exceptions
           $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];
         }
         if (is_array($master['recurrence']['EXDATE'])) {
           $master['recurrence']['EXDATE'] = array_filter($master['recurrence']['EXDATE'], function($exdate) use ($event) {
             return $exdate < $event['start'];
           });
         }
 
         // save new event
         if ($success = $storage->insert_event($event)) {
           $success = $event['uid'];
 
           // update master event (no rescheduling!)
           self::clear_attandee_noreply($master);
           $storage->update_event($master);
         }
         break;
 
       case 'current':
         // recurring instances shall not store recurrence rules and attachments
         $event['recurrence'] = array();
         $event['thisandfuture'] = $savemode == 'future';
         unset($event['attachments'], $event['id']);
 
         // increment sequence of this instance if scheduling is affected
         if ($reschedule) {
           $event['sequence'] = max($old['sequence'], $master['sequence']) + 1;
         }
         else if (!isset($event['sequence'])) {
           $event['sequence'] = $old['sequence'] ?: $master['sequence'];
         }
 
         // save properties to a recurrence exception instance
         if ($old['_instance'] && is_array($master['recurrence']['EXCEPTIONS'])) {
           if ($this->update_recurrence_exceptions($master, $event, $old, $savemode)) {
             $success = $storage->update_event($master, $old['id']);
             break;
           }
         }
 
         $add_exception = true;
 
         // adjust matching RDATE entry if dates changed
         if (is_array($master['recurrence']['RDATE']) && ($old_date = $old['start']->format('Ymd')) != $event['start']->format('Ymd')) {
           foreach ($master['recurrence']['RDATE'] as $j => $rdate) {
             if ($rdate->format('Ymd') == $old_date) {
               $master['recurrence']['RDATE'][$j] = $event['start'];
               sort($master['recurrence']['RDATE']);
               $add_exception = false;
               break;
             }
           }
         }
 
         // save as new exception to master event
         if ($add_exception) {
           self::add_exception($master, $event, $old);
         }
 
         $success = $storage->update_event($master);
         break;
 
       default:  // 'all' is default
         $event['id'] = $master['uid'];
         $event['uid'] = $master['uid'];
 
         // use start date from master but try to be smart on time or duration changes
         $old_start_date = $old['start']->format('Y-m-d');
         $old_start_time = $old['allday'] ? '' : $old['start']->format('H:i');
         $old_duration = $old['end']->format('U') - $old['start']->format('U');
         
         $new_start_date = $event['start']->format('Y-m-d');
         $new_start_time = $event['allday'] ? '' : $event['start']->format('H:i');
         $new_duration = $event['end']->format('U') - $event['start']->format('U');
         
         $diff = $old_start_date != $new_start_date || $old_start_time != $new_start_time || $old_duration != $new_duration;
         $date_shift = $old['start']->diff($event['start']);
         
         // shifted or resized
         if ($diff && ($old_start_date == $new_start_date || $old_duration == $new_duration)) {
           $event['start'] = $master['start']->add($date_shift);
           $event['end'] = clone $event['start'];
           $event['end']->add(new DateInterval('PT'.$new_duration.'S'));
           
           // remove fixed weekday, will be re-set to the new weekday in kolab_calendar::update_event()
           if ($old_start_date != $new_start_date) {
             if (strlen($event['recurrence']['BYDAY']) == 2)
               unset($event['recurrence']['BYDAY']);
             if ($old['recurrence']['BYMONTH'] == $old['start']->format('n'))
               unset($event['recurrence']['BYMONTH']);
           }
         }
         // dates did not change, use the ones from master
         else if ($new_start_date . $new_start_time == $old_start_date . $old_start_time) {
           $event['start'] = $master['start'];
           $event['end'] = $master['end'];
         }
 
         // when saving an instance in 'all' mode, copy recurrence exceptions over
         if ($old['recurrence_id']) {
           $event['recurrence']['EXCEPTIONS'] = $master['recurrence']['EXCEPTIONS'];
         }
         else if ($master['_instance']) {
           $event['_instance'] = $master['_instance'];
           $event['recurrence_date'] = $master['recurrence_date'];
         }
 
         // TODO: forward changes to exceptions (which do not yet have differing values stored)
         if (is_array($event['recurrence']) && is_array($event['recurrence']['EXCEPTIONS']) && !$with_exceptions) {
           // determine added and removed attendees
           $old_attendees = $current_attendees = $added_attendees = array();
           foreach ((array)$old['attendees'] as $attendee) {
             $old_attendees[] = $attendee['email'];
           }
           foreach ((array)$event['attendees'] as $attendee) {
             $current_attendees[] = $attendee['email'];
             if (!in_array($attendee['email'], $old_attendees)) {
               $added_attendees[] = $attendee;
             }
           }
           $removed_attendees = array_diff($old_attendees, $current_attendees);
 
           foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
             calendar::merge_attendee_data($event['recurrence']['EXCEPTIONS'][$i], $added_attendees, $removed_attendees);
           }
 
           // adjust recurrence-id when start changed and therefore the entire recurrence chain changes
           if ($old_start_date != $new_start_date || $old_start_time != $new_start_time) {
             $recurrence_id_format = libcalendaring::recurrence_id_format($event);
             foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
               $recurrence_id = is_a($exception['recurrence_date'], 'DateTime') ? $exception['recurrence_date'] :
                   rcube_utils::anytodatetime($exception['_instance'], $old['start']->getTimezone());
               if (is_a($recurrence_id, 'DateTime')) {
                 $recurrence_id->add($date_shift);
                 $event['recurrence']['EXCEPTIONS'][$i]['recurrence_date'] = $recurrence_id;
                 $event['recurrence']['EXCEPTIONS'][$i]['_instance'] = $recurrence_id->format($recurrence_id_format);
               }
             }
           }
 
           // set link to top-level exceptions
           $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
         }
 
         // unset _dateonly flags in (cached) date objects
         unset($event['start']->_dateonly, $event['end']->_dateonly);
 
         $success = $storage->update_event($event) ? $event['id'] : false;  // return master UID
         break;
     }
 
     if ($success && $this->freebusy_trigger)
       $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
     
     return $success;
   }
 
   /**
    * Determine whether the current change affects scheduling and reset attendee status accordingly
    */
   public function check_scheduling(&$event, $old, $update = true)
   {
     // skip this check when importing iCal/iTip events
     if (isset($event['sequence']) || !empty($event['_method'])) {
       return false;
     }
 
     // iterate through the list of properties considered 'significant' for scheduling
     $kolab_event = $old['_formatobj'] ?: new kolab_format_event();
     $reschedule = $kolab_event->check_rescheduling($event, $old);
 
     // reset all attendee status to needs-action (#4360)
     if ($update && $reschedule && is_array($event['attendees'])) {
       $is_organizer = false;
       $emails = $this->cal->get_user_emails();
       $attendees = $event['attendees'];
       foreach ($attendees as $i => $attendee) {
         if ($attendee['role'] == 'ORGANIZER' && $attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
           $is_organizer = true;
         }
         else if ($attendee['role'] != 'ORGANIZER' && $attendee['role'] != 'NON-PARTICIPANT' && $attendee['status'] != 'DELEGATED') {
           $attendees[$i]['status'] = 'NEEDS-ACTION';
           $attendees[$i]['rsvp'] = true;
         }
       }
 
       // update attendees only if I'm the organizer
       if ($is_organizer || ($event['organizer'] && in_array(strtolower($event['organizer']['email']), $emails))) {
         $event['attendees'] = $attendees;
       }
     }
 
     return $reschedule;
   }
 
   /**
    * Apply the given changes to already existing exceptions
    */
   protected function update_recurrence_exceptions(&$master, $event, $old, $savemode)
   {
     $saved = false;
     $existing = null;
 
     // determine added and removed attendees
     $added_attendees = $removed_attendees = array();
     if ($savemode == 'future') {
       $old_attendees = $current_attendees = array();
       foreach ((array)$old['attendees'] as $attendee) {
         $old_attendees[] = $attendee['email'];
       }
       foreach ((array)$event['attendees'] as $attendee) {
         $current_attendees[] = $attendee['email'];
         if (!in_array($attendee['email'], $old_attendees)) {
           $added_attendees[] = $attendee;
         }
       }
       $removed_attendees = array_diff($old_attendees, $current_attendees);
     }
 
     foreach ($master['recurrence']['EXCEPTIONS'] as $i => $exception) {
       // update a specific instance
       if ($exception['_instance'] == $old['_instance']) {
         $existing = $i;
 
         // check savemode against existing exception mode.
         // if matches, we can update this existing exception
         if ((bool)$exception['thisandfuture'] === ($savemode == 'future')) {
           $event['_instance'] = $old['_instance'];
           $event['thisandfuture'] = $old['thisandfuture'];
           $event['recurrence_date'] = $old['recurrence_date'];
           $master['recurrence']['EXCEPTIONS'][$i] = $event;
           $saved = true;
         }
       }
       // merge the new event properties onto future exceptions
       if ($savemode == 'future' && $exception['_instance'] >= $old['_instance']) {
         unset($event['thisandfuture']);
         self::merge_exception_data($master['recurrence']['EXCEPTIONS'][$i], $event, array('attendees'));
 
         if (!empty($added_attendees) || !empty($removed_attendees)) {
           calendar::merge_attendee_data($master['recurrence']['EXCEPTIONS'][$i], $added_attendees, $removed_attendees);
         }
       }
     }
 /*
     // we could not update the existing exception due to savemode mismatch...
     if (!$saved && $existing !== null && $master['recurrence']['EXCEPTIONS'][$existing]['thisandfuture']) {
       // ... try to move the existing this-and-future exception to the next occurrence
       foreach ($this->get_recurring_events($master, $existing['start']) as $candidate) {
         // our old this-and-future exception is obsolete
         if ($candidate['thisandfuture']) {
           unset($master['recurrence']['EXCEPTIONS'][$existing]);
           $saved = true;
           break;
         }
         // this occurrence doesn't yet have an exception
         else if (!$candidate['isexception']) {
           $event['_instance'] = $candidate['_instance'];
           $event['recurrence_date'] = $candidate['recurrence_date'];
           $master['recurrence']['EXCEPTIONS'][$i] = $event;
           $saved = true;
           break;
         }
       }
     }
 */
 
     // set link to top-level exceptions
     $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];
 
     // returning false here will add a new exception
     return $saved;
   }
 
   /**
    * Add or update the given event as an exception to $master
    */
   public static function add_exception(&$master, $event, $old = null)
   {
     if ($old) {
       $event['_instance'] = $old['_instance'];
       if (!$event['recurrence_date'])
         $event['recurrence_date'] = $old['recurrence_date'] ?: $old['start'];
     }
     else if (!$event['recurrence_date']) {
       $event['recurrence_date'] = $event['start'];
     }
 
     if (!$event['_instance'] && is_a($event['recurrence_date'], 'DateTime')) {
       $event['_instance'] = libcalendaring::recurrence_instance_identifier($event);
     }
 
     if (!is_array($master['exceptions']) && is_array($master['recurrence']['EXCEPTIONS'])) {
       $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];
     }
 
     $existing = false;
     foreach ((array)$master['exceptions'] as $i => $exception) {
       if ($exception['_instance'] == $event['_instance']) {
         $master['exceptions'][$i] = $event;
         $existing = true;
       }
     }
 
     if (!$existing) {
       $master['exceptions'][] = $event;
     }
 
     return true;
   }
 
   /**
    * Remove the noreply flags from attendees
    */
   public static function clear_attandee_noreply(&$event)
   {
     foreach ((array)$event['attendees'] as $i => $attendee) {
       unset($event['attendees'][$i]['noreply']);
     }
   }
 
 
   /**
    * Merge certain properties from the overlay event to the base event object
    *
    * @param array The event object to be altered
    * @param array The overlay event object to be merged over $event
    * @param array List of properties not allowed to be overwritten
    */
   public static function merge_exception_data(&$event, $overlay, $blacklist = null)
   {
     $forbidden = array('id','uid','recurrence','recurrence_date','thisandfuture','organizer','_attachments');
 
     if (is_array($blacklist))
       $forbidden = array_merge($forbidden, $blacklist);
 
     // compute date offset from the exception
     if ($overlay['start'] instanceof DateTime && $overlay['recurrence_date'] instanceof DateTime) {
       $date_offset = $overlay['recurrence_date']->diff($overlay['start']);
     }
 
     foreach ($overlay as $prop => $value) {
       if ($prop == 'start' || $prop == 'end') {
         if (is_object($event[$prop]) && $event[$prop] instanceof DateTime) {
           // set date value if overlay is an exception of the current instance
           if (substr($overlay['_instance'], 0, 8) == substr($event['_instance'], 0, 8)) {
             $event[$prop]->setDate(intval($value->format('Y')), intval($value->format('n')), intval($value->format('j')));
           }
           // apply date offset
           else if ($date_offset) {
             $event[$prop]->add($date_offset);
           }
           // adjust time of the recurring event instance
           $event[$prop]->setTime($value->format('G'), intval($value->format('i')), intval($value->format('s')));
         }
       }
       else if ($prop == 'thisandfuture' && $overlay['_instance'] == $event['_instance']) {
         $event[$prop] = $value;
       }
       else if ($prop[0] != '_' && !in_array($prop, $forbidden))
         $event[$prop] = $value;
     }
   }
 
   /**
    * Get events from source.
    *
    * @param  integer Event's new start (unix timestamp)
    * @param  integer Event's new end (unix timestamp)
    * @param  string  Search query (optional)
    * @param  mixed   List of calendar IDs to load events from (either as array or comma-separated string)
    * @param  boolean Include virtual events (optional)
    * @param  integer Only list events modified since this time (unix timestamp)
    * @return array A list of event records
    */
   public function load_events($start, $end, $search = null, $calendars = null, $virtual = 1, $modifiedsince = null)
   {
     if ($calendars && is_string($calendars))
       $calendars = explode(',', $calendars);
     else if (!$calendars) {
       $this->_read_calendars();
       $calendars = array_keys($this->calendars);
     }
 
     $query = array();
     if ($modifiedsince)
       $query[] = array('changed', '>=', $modifiedsince);
 
     $events = $categories = array();
     foreach ($calendars as $cid) {
       if ($storage = $this->get_calendar($cid)) {
         $events = array_merge($events, $storage->list_events($start, $end, $search, $virtual, $query));
         $categories += $storage->categories;
       }
     }
 
     // add events from the address books birthday calendar
     if (in_array(self::BIRTHDAY_CALENDAR_ID, $calendars)) {
       $events = array_merge($events, $this->load_birthday_events($start, $end, $search, $modifiedsince));
     }
 
     // add new categories to user prefs
     $old_categories = $this->rc->config->get('calendar_categories', $this->default_categories);
     if ($newcats = array_udiff(array_keys($categories), array_keys($old_categories), function($a, $b){ return strcasecmp($a, $b); })) {
       foreach ($newcats as $category)
         $old_categories[$category] = '';  // no color set yet
       $this->rc->user->save_prefs(array('calendar_categories' => $old_categories));
     }
 
     array_walk($events, 'kolab_driver::to_rcube_event');
     return $events;
   }
 
   /**
    * Get number of events in the given calendar
    *
    * @param  mixed   List of calendar IDs to count events (either as array or comma-separated string)
    * @param  integer Date range start (unix timestamp)
    * @param  integer Date range end (unix timestamp)
    * @return array   Hash array with counts grouped by calendar ID
    */
   public function count_events($calendars, $start, $end = null)
   {
       $counts = array();
 
       if ($calendars && is_string($calendars))
         $calendars = explode(',', $calendars);
       else if (!$calendars) {
         $this->_read_calendars();
         $calendars = array_keys($this->calendars);
       }
 
       foreach ($calendars as $cid) {
         if ($storage = $this->get_calendar($cid)) {
             $counts[$cid] = $storage->count_events($start, $end);
         }
       }
 
       return $counts;
   }
 
   /**
    * Get a list of pending alarms to be displayed to the user
    *
    * @see calendar_driver::pending_alarms()
    */
   public function pending_alarms($time, $calendars = null)
   {
     $interval = 300;
     $time -= $time % 60;
     
     $slot = $time;
     $slot -= $slot % $interval;
     
     $last = $time - max(60, $this->rc->config->get('refresh_interval', 0));
     $last -= $last % $interval;
     
     // only check for alerts once in 5 minutes
     if ($last == $slot)
       return array();
     
     if ($calendars && is_string($calendars))
       $calendars = explode(',', $calendars);
     
     $time = $slot + $interval;
     
     $candidates = array();
     $query = array(array('tags', '=', 'x-has-alarms'));
 
     $this->_read_calendars();
 
     foreach ($this->calendars as $cid => $calendar) {
       // skip calendars with alarms disabled
       if (!$calendar->alarms || ($calendars && !in_array($cid, $calendars)))
         continue;
 
       foreach ($calendar->list_events($time, $time + 86400 * 365, null, 1, $query) as $e) {
         // add to list if alarm is set
         $alarm = libcalendaring::get_next_alarm($e);
         if ($alarm && $alarm['time'] && $alarm['time'] >= $last && in_array($alarm['action'], $this->alarm_types)) {
           $id = $alarm['id'];  // use alarm-id as primary identifier
           $candidates[$id] = array(
             'id'       => $id,
             'title'    => $e['title'],
             'location' => $e['location'],
             'start'    => $e['start'],
             'end'      => $e['end'],
             'notifyat' => $alarm['time'],
             'action'   => $alarm['action'],
           );
         }
       }
     }
 
     // get alarm information stored in local database
     if (!empty($candidates)) {
       $alarm_ids = array_map(array($this->rc->db, 'quote'), array_keys($candidates));
       $result = $this->rc->db->query("SELECT *"
         . " FROM " . $this->rc->db->table_name('kolab_alarms', true)
         . " WHERE `alarm_id` IN (" . join(',', $alarm_ids) . ")"
           . " AND `user_id` = ?",
         $this->rc->user->ID
       );
 
       while ($result && ($e = $this->rc->db->fetch_assoc($result))) {
         $dbdata[$e['alarm_id']] = $e;
       }
     }
     
     $alarms = array();
     foreach ($candidates as $id => $alarm) {
       // skip dismissed alarms
       if ($dbdata[$id]['dismissed'])
         continue;
       
       // snooze function may have shifted alarm time
       $notifyat = $dbdata[$id]['notifyat'] ? strtotime($dbdata[$id]['notifyat']) : $alarm['notifyat'];
       if ($notifyat <= $time)
         $alarms[] = $alarm;
     }
     
     return $alarms;
   }
 
   /**
    * Feedback after showing/sending an alarm notification
    *
    * @see calendar_driver::dismiss_alarm()
    */
   public function dismiss_alarm($alarm_id, $snooze = 0)
   {
     $alarms_table = $this->rc->db->table_name('kolab_alarms', true);
     // delete old alarm entry
     $this->rc->db->query("DELETE FROM $alarms_table"
       . " WHERE `alarm_id` = ? AND `user_id` = ?",
       $alarm_id,
       $this->rc->user->ID
     );
 
     // set new notifyat time or unset if not snoozed
     $notifyat = $snooze > 0 ? date('Y-m-d H:i:s', time() + $snooze) : null;
 
     $query = $this->rc->db->query("INSERT INTO $alarms_table"
       . " (`alarm_id`, `user_id`, `dismissed`, `notifyat`)"
       . " VALUES (?, ?, ?, ?)",
       $alarm_id,
       $this->rc->user->ID,
       $snooze > 0 ? 0 : 1,
       $notifyat
     );
 
     return $this->rc->db->affected_rows($query);
   }
 
   /**
    * List attachments from the given event
    */
   public function list_attachments($event)
   {
     if (!($storage = $this->get_calendar($event['calendar'])))
       return false;
 
     $event = $storage->get_event($event['id']);
 
     return $event['attachments'];
   }
 
   /**
    * Get attachment properties
    */
   public function get_attachment($id, $event)
   {
     if (!($storage = $this->get_calendar($event['calendar'])))
       return false;
 
     // get old revision of event
     if ($event['rev']) {
       $event = $this->get_event_revison($event, $event['rev'], true);
     }
     else {
       $event = $storage->get_event($event['id']);
     }
 
     if ($event && !empty($event['_attachments'])) {
       foreach ($event['_attachments'] as $att) {
         if ($att['id'] == $id) {
           return $att;
         }
       }
     }
 
     return null;
   }
 
   /**
    * Get attachment body
    * @see calendar_driver::get_attachment_body()
    */
   public function get_attachment_body($id, $event)
   {
     if (!($cal = $this->get_calendar($event['calendar'])))
       return false;
 
     // get old revision of event
     if ($event['rev']) {
       if (empty($this->bonnie_api)) {
         return false;
       }
 
       $cid = substr($id, 4);
 
       // call Bonnie API and get the raw mime message
       list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
       if ($msg_raw = $this->bonnie_api->rawdata('event', $uid, $event['rev'], $mailbox, $msguid)) {
         // parse the message and find the part with the matching content-id
         $message = rcube_mime::parse_message($msg_raw);
         foreach ((array)$message->parts as $part) {
           if ($part->headers['content-id'] && trim($part->headers['content-id'], '<>') == $cid) {
             return $part->body;
           }
         }
       }
 
       return false;
     }
 
     return $cal->get_attachment_body($id, $event);
   }
 
   /**
    * Build a struct representing the given message reference
    *
    * @see calendar_driver::get_message_reference()
    */
   public function get_message_reference($uri_or_headers, $folder = null)
   {
       if (is_object($uri_or_headers)) {
           $uri_or_headers = kolab_storage_config::get_message_uri($uri_or_headers, $folder);
       }
 
       if (is_string($uri_or_headers)) {
           return kolab_storage_config::get_message_reference($uri_or_headers, 'event');
       }
 
       return false;
   }
 
   /**
    * List availabale categories
    * The default implementation reads them from config/user prefs
    */
   public function list_categories()
   {
     // FIXME: complete list with categories saved in config objects (KEP:12)
     return $this->rc->config->get('calendar_categories', $this->default_categories);
   }
 
   /**
    * Create instances of a recurring event
    *
    * @param array  Hash array with event properties
    * @param object DateTime Start date of the recurrence window
    * @param object DateTime End date of the recurrence window
    * @return array List of recurring event instances
    */
   public function get_recurring_events($event, $start, $end = null)
   {
     // load the given event data into a libkolabxml container
     if (!$event['_formatobj']) {
       $event_xml = new kolab_format_event();
       $event_xml->set($event);
       $event['_formatobj'] = $event_xml;
     }
 
     $this->_read_calendars();
     $storage = reset($this->calendars);
     return $storage->get_recurring_events($event, $start, $end);
   }
 
   /**
    *
    */
   private function get_recurrence_count($event, $dtstart)
   {
     // use libkolab to compute recurring events
     if (class_exists('kolabcalendaring') && $event['_formatobj']) {
         $recurrence = new kolab_date_recurrence($event['_formatobj']);
     }
     else {
       // fallback to local recurrence implementation
       require_once($this->cal->home . '/lib/calendar_recurrence.php');
       $recurrence = new calendar_recurrence($this->cal, $event);
     }
 
     $count = 0;
     while (($next_event = $recurrence->next_instance()) && $next_event['start'] <= $dtstart && $count < 1000) {
       $count++;
     }
 
     return $count;
   }
 
   /**
    * Fetch free/busy information from a person within the given range
    */
   public function get_freebusy_list($email, $start, $end)
   {
     if (empty($email)/* || $end < time()*/)
       return false;
 
     // map vcalendar fbtypes to internal values
     $fbtypemap = array(
       'FREE' => calendar::FREEBUSY_FREE,
       'BUSY-TENTATIVE' => calendar::FREEBUSY_TENTATIVE,
       'X-OUT-OF-OFFICE' => calendar::FREEBUSY_OOF,
       'OOF' => calendar::FREEBUSY_OOF);
 
     // ask kolab server first
     try {
       $request_config = array(
         'store_body'       => true,
         'follow_redirects' => true,
       );
       $request  = libkolab::http_request(kolab_storage::get_freebusy_url($email), 'GET', $request_config);
       $response = $request->send();
 
       // authentication required
       if ($response->getStatus() == 401) {
         $request->setAuth($this->rc->user->get_username(), $this->rc->decrypt($_SESSION['password']));
         $response = $request->send();
       }
 
       if ($response->getStatus() == 200)
         $fbdata = $response->getBody();
 
       unset($request, $response);
     }
     catch (Exception $e) {
       PEAR::raiseError("Error fetching free/busy information: " . $e->getMessage());
     }
 
     // get free-busy url from contacts
     if (!$fbdata) {
       $fburl = null;
       foreach ((array)$this->rc->config->get('autocomplete_addressbooks', 'sql') as $book) {
         $abook = $this->rc->get_address_book($book);
 
         if ($result = $abook->search(array('email'), $email, true, true, true/*, 'freebusyurl'*/)) {
           while ($contact = $result->iterate()) {
             if ($fburl = $contact['freebusyurl']) {
               $fbdata = @file_get_contents($fburl);
               break;
             }
           }
         }
 
         if ($fbdata)
           break;
       }
     }
 
     // parse free-busy information using Horde classes
     if ($fbdata) {
       $ical = $this->cal->get_ical();
       $ical->import($fbdata);
       if ($fb = $ical->freebusy) {
         $result = array();
         foreach ($fb['periods'] as $tuple) {
           list($from, $to, $type) = $tuple;
           $result[] = array($from->format('U'), $to->format('U'), isset($fbtypemap[$type]) ? $fbtypemap[$type] : calendar::FREEBUSY_BUSY);
         }
 
         // we take 'dummy' free-busy lists as "unknown"
         if (empty($result) && !empty($fb['comment']) && stripos($fb['comment'], 'dummy'))
           return false;
 
         // set period from $start till the begin of the free-busy information as 'unknown'
         if ($fb['start'] && ($fbstart = $fb['start']->format('U')) && $start < $fbstart) {
           array_unshift($result, array($start, $fbstart, calendar::FREEBUSY_UNKNOWN));
         }
         // pad period till $end with status 'unknown'
         if ($fb['end'] && ($fbend = $fb['end']->format('U')) && $fbend < $end) {
           $result[] = array($fbend, $end, calendar::FREEBUSY_UNKNOWN);
         }
 
         return $result;
       }
     }
 
     return false;
   }
 
   /**
    * Handler to push folder triggers when sent from client.
    * Used to push free-busy changes asynchronously after updating an event
    */
   public function push_freebusy()
   {
     // make shure triggering completes
     set_time_limit(0);
     ignore_user_abort(true);
 
     $cal = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
     if (!($cal = $this->get_calendar($cal)))
       return false;
 
     // trigger updates on folder
     $trigger = $cal->storage->trigger();
     if (is_object($trigger) && is_a($trigger, 'PEAR_Error')) {
       rcube::raise_error(array(
         'code' => 900, 'type' => 'php',
         'file' => __FILE__, 'line' => __LINE__,
         'message' => "Failed triggering folder. Error was " . $trigger->getMessage()),
         true, false);
     }
 
     exit;
   }
 
 
   /**
    * Convert from driver format to external caledar app data
    */
   public static function to_rcube_event(&$record)
   {
     if (!is_array($record))
       return $record;
 
     $record['id'] = $record['uid'];
 
     if ($record['_instance']) {
       $record['id'] .= '-' . $record['_instance'];
 
       if (!$record['recurrence_id'] && !empty($record['recurrence']))
         $record['recurrence_id'] = $record['uid'];
     }
 
     // all-day events go from 12:00 - 13:00
     if (is_a($record['start'], 'DateTime') && $record['end'] <= $record['start'] && $record['allday']) {
       $record['end'] = clone $record['start'];
       $record['end']->add(new DateInterval('PT1H'));
     }
 
     // translate internal '_attachments' to external 'attachments' list
     if (!empty($record['_attachments'])) {
       foreach ($record['_attachments'] as $key => $attachment) {
         if ($attachment !== false) {
           if (!$attachment['name'])
             $attachment['name'] = $key;
 
           unset($attachment['path'], $attachment['content']);
           $attachments[] = $attachment;
         }
       }
 
       $record['attachments'] = $attachments;
     }
 
     if (!empty($record['attendees'])) {
       foreach ((array)$record['attendees'] as $i => $attendee) {
         if (is_array($attendee['delegated-from'])) {
           $record['attendees'][$i]['delegated-from'] = join(', ', $attendee['delegated-from']);
         }
         if (is_array($attendee['delegated-to'])) {
           $record['attendees'][$i]['delegated-to'] = join(', ', $attendee['delegated-to']);
         }
       }
     }
 
     // Roundcube only supports one category assignment
     if (is_array($record['categories']))
       $record['categories'] = $record['categories'][0];
 
     // the cancelled flag transltes into status=CANCELLED
     if ($record['cancelled'])
       $record['status'] = 'CANCELLED';
 
     // The web client only supports DISPLAY type of alarms
     if (!empty($record['alarms']))
       $record['alarms'] = preg_replace('/:[A-Z]+$/', ':DISPLAY', $record['alarms']);
 
     // remove empty recurrence array
     if (empty($record['recurrence']))
       unset($record['recurrence']);
 
     // clean up exception data
     if (is_array($record['recurrence']['EXCEPTIONS'])) {
       array_walk($record['recurrence']['EXCEPTIONS'], function(&$exception) {
         unset($exception['_mailbox'], $exception['_msguid'], $exception['_formatobj'], $exception['_attachments']);
       });
     }
 
     unset($record['_mailbox'], $record['_msguid'], $record['_type'], $record['_size'],
       $record['_formatobj'], $record['_attachments'], $record['exceptions'], $record['x-custom']);
 
     return $record;
   }
 
   /**
    *
    */
   public static function from_rcube_event($event, $old = array())
   {
-    // in kolab_storage attachments are indexed by content-id
-    if (is_array($event['attachments']) || !empty($event['deleted_attachments'])) {
-      $event['_attachments'] = array();
-
-      foreach ($event['attachments'] as $attachment) {
-        $key = null;
-        // Roundcube ID has nothing to do with the storage ID, remove it
-        if ($attachment['content'] || $attachment['path']) {
-          unset($attachment['id']);
-        }
-        else {
-          foreach ((array)$old['_attachments'] as $cid => $oldatt) {
-            if ($attachment['id'] == $oldatt['id'])
-              $key = $cid;
-          }
-        }
-
-        // flagged for deletion => set to false
-        if ($attachment['_deleted'] || in_array($attachment['id'], (array)$event['deleted_attachments'])) {
-          $event['_attachments'][$key] = false;
-        }
-        // replace existing entry
-        else if ($key) {
-          $event['_attachments'][$key] = $attachment;
-        }
-        // append as new attachment
-        else {
-          $event['_attachments'][] = $attachment;
-        }
-      }
-
-      $event['_attachments'] = array_merge((array)$old['_attachments'], $event['_attachments']);
-
-      // attachments flagged for deletion => set to false
-      foreach ($event['_attachments'] as $key => $attachment) {
-        if ($attachment['_deleted'] || in_array($attachment['id'], (array)$event['deleted_attachments'])) {
-          $event['_attachments'][$key] = false;
-        }
-      }
-    }
+    kolab_format::merge_attachments($event, $old);
 
     return $event;
   }
 
 
   /**
    * Set CSS class according to the event's attendde partstat
    */
   public static function add_partstat_class($event, $partstats, $user = null)
   {
     // set classes according to PARTSTAT
     if (is_array($event['attendees'])) {
       $user_emails = libcalendaring::get_instance()->get_user_emails($user);
       $partstat = 'UNKNOWN';
       foreach ($event['attendees'] as $attendee) {
         if (in_array($attendee['email'], $user_emails)) {
           $partstat = $attendee['status'];
           break;
         }
       }
 
       if (in_array($partstat, $partstats)) {
         $event['className'] = trim($event['className'] . ' fc-invitation-' . strtolower($partstat));
       }
     }
 
     return $event;
   }
 
   /**
    * Provide a list of revisions for the given event
    *
    * @param array  $event Hash array with event properties
    *
    * @return array List of changes, each as a hash array
    * @see calendar_driver::get_event_changelog()
    */
   public function get_event_changelog($event)
   {
     if (empty($this->bonnie_api)) {
       return false;
     }
 
     list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
 
     $result = $this->bonnie_api->changelog('event', $uid, $mailbox, $msguid);
     if (is_array($result) && $result['uid'] == $uid) {
       return $result['changes'];
     }
 
     return false;
   }
 
   /**
    * Get a list of property changes beteen two revisions of an event
    *
    * @param array  $event Hash array with event properties
    * @param mixed  $rev1  Old Revision
    * @param mixed  $rev2  New Revision
    *
    * @return array List of property changes, each as a hash array
    * @see calendar_driver::get_event_diff()
    */
   public function get_event_diff($event, $rev1, $rev2)
   {
     if (empty($this->bonnie_api)) {
       return false;
     }
 
     list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
 
     // get diff for the requested recurrence instance
     $instance_id = $event['id'] != $uid ? substr($event['id'], strlen($uid) + 1) : null;
 
     // call Bonnie API
     $result = $this->bonnie_api->diff('event', $uid, $rev1, $rev2, $mailbox, $msguid, $instance_id);
     if (is_array($result) && $result['uid'] == $uid) {
       $result['rev1'] = $rev1;
       $result['rev2'] = $rev2;
 
       $keymap = array(
         'dtstart'  => 'start',
         'dtend'    => 'end',
         'dstamp'   => 'changed',
         'summary'  => 'title',
         'alarm'    => 'alarms',
         'attendee' => 'attendees',
         'attach'   => 'attachments',
         'rrule'    => 'recurrence',
         'transparency' => 'free_busy',
         'classification' => 'sensitivity',
         'lastmodified-date' => 'changed',
       );
       $prop_keymaps = array(
         'attachments' => array('fmttype' => 'mimetype', 'label' => 'name'),
         'attendees'   => array('partstat' => 'status'),
       );
       $special_changes = array();
 
       // map kolab event properties to keys the client expects
       array_walk($result['changes'], function(&$change, $i) use ($keymap, $prop_keymaps, $special_changes) {
         if (array_key_exists($change['property'], $keymap)) {
           $change['property'] = $keymap[$change['property']];
         }
         // translate free_busy values
         if ($change['property'] == 'free_busy') {
           $change['old'] = $old['old'] ? 'free' : 'busy';
           $change['new'] = $old['new'] ? 'free' : 'busy';
         }
         // map alarms trigger value
         if ($change['property'] == 'alarms') {
           if (is_array($change['old']) && is_array($change['old']['trigger']))
             $change['old']['trigger'] = $change['old']['trigger']['value'];
           if (is_array($change['new']) && is_array($change['new']['trigger']))
             $change['new']['trigger'] = $change['new']['trigger']['value'];
         }
         // make all property keys uppercase
         if ($change['property'] == 'recurrence') {
           $special_changes['recurrence'] = $i;
           foreach (array('old','new') as $m) {
             if (is_array($change[$m])) {
               $props = array();
               foreach ($change[$m] as $k => $v)
                 $props[strtoupper($k)] = $v;
               $change[$m] = $props;
             }
           }
         }
         // map property keys names
         if (is_array($prop_keymaps[$change['property']])) {
           foreach ($prop_keymaps[$change['property']] as $k => $dest) {
             if (is_array($change['old']) && array_key_exists($k, $change['old'])) {
               $change['old'][$dest] = $change['old'][$k];
               unset($change['old'][$k]);
             }
             if (is_array($change['new']) && array_key_exists($k, $change['new'])) {
               $change['new'][$dest] = $change['new'][$k];
               unset($change['new'][$k]);
             }
           }
         }
 
         if ($change['property'] == 'exdate') {
           $special_changes['exdate'] = $i;
         }
         else if ($change['property'] == 'rdate') {
           $special_changes['rdate'] = $i;
         }
       });
 
       // merge some recurrence changes
       foreach (array('exdate','rdate') as $prop) {
         if (array_key_exists($prop, $special_changes)) {
           $exdate = $result['changes'][$special_changes[$prop]];
           if (array_key_exists('recurrence', $special_changes)) {
             $recurrence = &$result['changes'][$special_changes['recurrence']];
           }
           else {
             $i = count($result['changes']);
             $result['changes'][$i] = array('property' => 'recurrence', 'old' => array(), 'new' => array());
             $recurrence = &$result['changes'][$i]['recurrence'];
           }
           $key = strtoupper($prop);
           $recurrence['old'][$key] = $exdate['old'];
           $recurrence['new'][$key] = $exdate['new'];
           unset($result['changes'][$special_changes[$prop]]);
         }
       }
 
       return $result;
     }
 
     return false;
   }
 
   /**
    * Return full data of a specific revision of an event
    *
    * @param array  Hash array with event properties
    * @param mixed  $rev Revision number
    *
    * @return array Event object as hash array
    * @see calendar_driver::get_event_revison()
    */
   public function get_event_revison($event, $rev, $internal = false)
   {
     if (empty($this->bonnie_api)) {
       return false;
     }
 
     $eventid = $event['id'];
     $calid = $event['calendar'];
     list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
 
     // call Bonnie API
     $result = $this->bonnie_api->get('event', $uid, $rev, $mailbox, $msguid);
     if (is_array($result) && $result['uid'] == $uid && !empty($result['xml'])) {
       $format = kolab_format::factory('event');
       $format->load($result['xml']);
       $event = $format->to_array();
       $format->get_attachments($event, true);
 
       // get the right instance from a recurring event
       if ($eventid != $event['uid']) {
         $instance_id = substr($eventid, strlen($event['uid']) + 1);
 
         // check for recurrence exception first
         if ($instance = $format->get_instance($instance_id)) {
           $event = $instance;
         }
         else {
           // not a exception, compute recurrence...
           $event['_formatobj'] = $format;
           $recurrence_date = rcube_utils::anytodatetime($instance_id, $event['start']->getTimezone());
           foreach ($this->get_recurring_events($event, $event['start'], $recurrence_date) as $instance) {
             if ($instance['id'] == $eventid) {
               $event = $instance;
               break;
             }
           }
         }
       }
 
       if ($format->is_valid()) {
         $event['calendar'] = $calid;
         $event['rev'] = $result['rev'];
         return $internal ? $event : self::to_rcube_event($event);
       }
     }
 
     return false;
   }
 
   /**
    * Command the backend to restore a certain revision of an event.
    * This shall replace the current event with an older version.
    *
    * @param mixed  UID string or hash array with event properties:
    *        id: Event identifier
    *  calendar: Calendar identifier
    * @param mixed  $rev Revision number
    *
    * @return boolean True on success, False on failure
    */
   public function restore_event_revision($event, $rev)
   {
     if (empty($this->bonnie_api)) {
       return false;
     }
 
     list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
     $calendar = $this->get_calendar($event['calendar']);
     $success = false;
 
     if ($calendar && $calendar->storage && $calendar->editable) {
       if ($raw_msg = $this->bonnie_api->rawdata('event', $uid, $rev, $mailbox)) {
         $imap = $this->rc->get_storage();
 
         // insert $raw_msg as new message
         if ($imap->save_message($calendar->storage->name, $raw_msg, null, false)) {
           $success = true;
 
           // delete old revision from imap and cache
           $imap->delete_message($msguid, $calendar->storage->name);
           $calendar->storage->cache->set($msguid, false);
         }
       }
     }
 
     return $success;
   }
 
   /**
    * Helper method to resolved the given event identifier into uid and folder
    *
    * @return array (uid,folder,msguid) tuple
    */
   private function _resolve_event_identity($event)
   {
     $mailbox = $msguid = null;
     if (is_array($event)) {
       $uid = $event['uid'] ?: $event['id'];
       if (($cal = $this->get_calendar($event['calendar'])) && !($cal instanceof kolab_invitation_calendar)) {
         $mailbox = $cal->get_mailbox_id();
 
         // get event object from storage in order to get the real object uid an msguid
         if ($ev = $cal->get_event($event['id'])) {
           $msguid = $ev['_msguid'];
           $uid = $ev['uid'];
         }
       }
     }
     else {
       $uid = $event;
 
       // get event object from storage in order to get the real object uid an msguid
       if ($ev = $this->get_event($event)) {
         $mailbox = $ev['_mailbox'];
         $msguid = $ev['_msguid'];
         $uid = $ev['uid'];
       }
     }
 
     return array($uid, $mailbox, $msguid);
   }
 
   /**
    * Callback function to produce driver-specific calendar create/edit form
    *
    * @param string Request action 'form-edit|form-new'
    * @param array  Calendar properties (e.g. id, color)
    * @param array  Edit form fields
    *
    * @return string HTML content of the form
    */
   public function calendar_form($action, $calendar, $formfields)
   {
     // show default dialog for birthday calendar
     if (in_array($calendar['id'], array(self::BIRTHDAY_CALENDAR_ID, self::INVITATIONS_CALENDAR_PENDING, self::INVITATIONS_CALENDAR_DECLINED))) {
       if ($calendar['id'] != self::BIRTHDAY_CALENDAR_ID)
         unset($formfields['showalarms']);
       return parent::calendar_form($action, $calendar, $formfields);
     }
 
     $this->_read_calendars();
 
     if ($calendar['id'] && ($cal = $this->calendars[$calendar['id']])) {
       $folder = $cal->get_realname(); // UTF7
       $color  = $cal->get_color();
     }
     else {
       $folder = '';
       $color  = '';
     }
 
     $hidden_fields[] = array('name' => 'oldname', 'value' => $folder);
 
     $storage = $this->rc->get_storage();
     $delim   = $storage->get_hierarchy_delimiter();
     $form   = array();
 
     if (strlen($folder)) {
       $path_imap = explode($delim, $folder);
       array_pop($path_imap);  // pop off name part
       $path_imap = implode($path_imap, $delim);
 
       $options = $storage->folder_info($folder);
     }
     else {
       $path_imap = '';
     }
 
     // General tab
     $form['props'] = array(
       'name' => $this->rc->gettext('properties'),
     );
 
     // Disable folder name input
     if (!empty($options) && ($options['norename'] || $options['protected'])) {
       $input_name = new html_hiddenfield(array('name' => 'name', 'id' => 'calendar-name'));
       $formfields['name']['value'] = kolab_storage::object_name($folder)
         . $input_name->show($folder);
     }
 
     // calendar name (default field)
     $form['props']['fieldsets']['location'] = array(
       'name'  => $this->rc->gettext('location'),
       'content' => array(
         'name' => $formfields['name']
       ),
     );
 
     if (!empty($options) && ($options['norename'] || $options['protected'])) {
       // prevent user from moving folder
       $hidden_fields[] = array('name' => 'parent', 'value' => $path_imap);
     }
     else {
       $select = kolab_storage::folder_selector('event', array('name' => 'parent', 'id' => 'calendar-parent'), $folder);
       $form['props']['fieldsets']['location']['content']['path'] = array(
         'id' => 'calendar-parent',
         'label' => $this->cal->gettext('parentcalendar'),
         'value' => $select->show(strlen($folder) ? $path_imap : ''),
       );
     }
 
     // calendar color (default field)
     $form['props']['fieldsets']['settings'] = array(
       'name'  => $this->rc->gettext('settings'),
       'content' => array(
         'color' => $formfields['color'],
         'showalarms' => $formfields['showalarms'],
       ),
     );
     
     
     if ($action != 'form-new') {
       $form['sharing'] = array(
           'name'    => rcube::Q($this->cal->gettext('tabsharing')),
           'content' => html::tag('iframe', array(
             'src' => $this->cal->rc->url(array('_action' => 'calendar-acl', 'id' => $calendar['id'], 'framed' => 1)),
             'width' => '100%',
             'height' => 350,
             'border' => 0,
             'style' => 'border:0'),
         ''),
       );
     }
 
     $this->form_html = '';
     if (is_array($hidden_fields)) {
         foreach ($hidden_fields as $field) {
             $hiddenfield = new html_hiddenfield($field);
             $this->form_html .= $hiddenfield->show() . "\n";
         }
     }
 
     // Create form output
     foreach ($form as $tab) {
       if (!empty($tab['fieldsets']) && is_array($tab['fieldsets'])) {
         $content = '';
         foreach ($tab['fieldsets'] as $fieldset) {
           $subcontent = $this->get_form_part($fieldset);
           if ($subcontent) {
             $content .= html::tag('fieldset', null, html::tag('legend', null, rcube::Q($fieldset['name'])) . $subcontent) ."\n";
           }
         }
       }
       else {
         $content = $this->get_form_part($tab);
       }
 
       if ($content) {
         $this->form_html .= html::tag('fieldset', null, html::tag('legend', null, rcube::Q($tab['name'])) . $content) ."\n";
       }
     }
 
     // Parse form template for skin-dependent stuff
     $this->rc->output->add_handler('calendarform', array($this, 'calendar_form_html'));
     return $this->rc->output->parse('calendar.kolabform', false, false);
   }
 
   /**
    * Handler for template object
    */
   public function calendar_form_html()
   {
     return $this->form_html;
   }
 
   /**
    * Helper function used in calendar_form_content(). Creates a part of the form.
    */
   private function get_form_part($form)
   {
     $content = '';
 
     if (is_array($form['content']) && !empty($form['content'])) {
       $table = new html_table(array('cols' => 2));
       foreach ($form['content'] as $col => $colprop) {
         $label = !empty($colprop['label']) ? $colprop['label'] : $this->cal->gettext($col);
 
         $table->add('title', html::label($colprop['id'], rcube::Q($label)));
         $table->add(null, $colprop['value']);
       }
       $content = $table->show();
     }
     else {
       $content = $form['content'];
     }
 
     return $content;
   }
 
 
   /**
    * Handler to render ACL form for a calendar folder
    */
   public function calendar_acl()
   {
     $this->rc->output->add_handler('folderacl', array($this, 'calendar_acl_form'));
     $this->rc->output->send('calendar.kolabacl');
   }
 
   /**
    * Handler for ACL form template object
    */
   public function calendar_acl_form()
   {
     $calid = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
     if ($calid && ($cal = $this->get_calendar($calid))) {
       $folder = $cal->get_realname(); // UTF7
       $color  = $cal->get_color();
     }
     else {
       $folder = '';
       $color  = '';
     }
 
     $storage = $this->rc->get_storage();
     $delim   = $storage->get_hierarchy_delimiter();
     $form   = array();
 
     if (strlen($folder)) {
       $path_imap = explode($delim, $folder);
       array_pop($path_imap);  // pop off name part
       $path_imap = implode($path_imap, $delim);
 
       $options = $storage->folder_info($folder);
 
       // Allow plugins to modify the form content (e.g. with ACL form)
       $plugin = $this->rc->plugins->exec_hook('calendar_form_kolab',
         array('form' => $form, 'options' => $options, 'name' => $folder));
     }
 
     if (!$plugin['form']['sharing']['content'])
         $plugin['form']['sharing']['content'] = html::div('hint', $this->cal->gettext('aclnorights'));
 
     return $plugin['form']['sharing']['content'];
   }
 
   /**
    * Handler for user_delete plugin hook
    */
   public function user_delete($args)
   {
     $db = $this->rc->get_dbh();
     foreach (array('kolab_alarms', 'itipinvitations') as $table) {
       $db->query("DELETE FROM " . $this->rc->db->table_name($table, true)
         . " WHERE `user_id` = ?", $args['user']->ID);
     }
   }
 }
diff --git a/plugins/libkolab/lib/kolab_format.php b/plugins/libkolab/lib/kolab_format.php
index 5041dd38..27b8956e 100644
--- a/plugins/libkolab/lib/kolab_format.php
+++ b/plugins/libkolab/lib/kolab_format.php
@@ -1,707 +1,771 @@
 <?php
 
 /**
  * Kolab format model class wrapping libkolabxml bindings
  *
  * Abstract base class for different Kolab groupware objects read from/written
  * to the new Kolab 3 format using the PHP bindings of libkolabxml.
  *
  * @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/>.
  */
 
 abstract class kolab_format
 {
     public static $timezone;
 
     public /*abstract*/ $CTYPE;
     public /*abstract*/ $CTYPEv2;
 
     protected /*abstract*/ $objclass;
     protected /*abstract*/ $read_func;
     protected /*abstract*/ $write_func;
 
     protected $obj;
     protected $data;
     protected $xmldata;
     protected $xmlobject;
     protected $formaterror;
     protected $loaded = false;
     protected $version = '3.0';
 
     const KTYPE_PREFIX = 'application/x-vnd.kolab.';
     const PRODUCT_ID   = 'Roundcube-libkolab-1.1';
 
     // mapping table for valid PHP timezones not supported by libkolabxml
     // basically the entire list of ftp://ftp.iana.org/tz/data/backward
     protected static $timezone_map = array(
         'Africa/Asmera' => 'Africa/Asmara',
         'Africa/Timbuktu' => 'Africa/Abidjan',
         'America/Argentina/ComodRivadavia' => 'America/Argentina/Catamarca',
         'America/Atka' => 'America/Adak',
         'America/Buenos_Aires' => 'America/Argentina/Buenos_Aires',
         'America/Catamarca' => 'America/Argentina/Catamarca',
         'America/Coral_Harbour' => 'America/Atikokan',
         'America/Cordoba' => 'America/Argentina/Cordoba',
         'America/Ensenada' => 'America/Tijuana',
         'America/Fort_Wayne' => 'America/Indiana/Indianapolis',
         'America/Indianapolis' => 'America/Indiana/Indianapolis',
         'America/Jujuy' => 'America/Argentina/Jujuy',
         'America/Knox_IN' => 'America/Indiana/Knox',
         'America/Louisville' => 'America/Kentucky/Louisville',
         'America/Mendoza' => 'America/Argentina/Mendoza',
         'America/Porto_Acre' => 'America/Rio_Branco',
         'America/Rosario' => 'America/Argentina/Cordoba',
         'America/Virgin' => 'America/Port_of_Spain',
         'Asia/Ashkhabad' => 'Asia/Ashgabat',
         'Asia/Calcutta' => 'Asia/Kolkata',
         'Asia/Chungking' => 'Asia/Shanghai',
         'Asia/Dacca' => 'Asia/Dhaka',
         'Asia/Katmandu' => 'Asia/Kathmandu',
         'Asia/Macao' => 'Asia/Macau',
         'Asia/Saigon' => 'Asia/Ho_Chi_Minh',
         'Asia/Tel_Aviv' => 'Asia/Jerusalem',
         'Asia/Thimbu' => 'Asia/Thimphu',
         'Asia/Ujung_Pandang' => 'Asia/Makassar',
         'Asia/Ulan_Bator' => 'Asia/Ulaanbaatar',
         'Atlantic/Faeroe' => 'Atlantic/Faroe',
         'Atlantic/Jan_Mayen' => 'Europe/Oslo',
         'Australia/ACT' => 'Australia/Sydney',
         'Australia/Canberra' => 'Australia/Sydney',
         'Australia/LHI' => 'Australia/Lord_Howe',
         'Australia/NSW' => 'Australia/Sydney',
         'Australia/North' => 'Australia/Darwin',
         'Australia/Queensland' => 'Australia/Brisbane',
         'Australia/South' => 'Australia/Adelaide',
         'Australia/Tasmania' => 'Australia/Hobart',
         'Australia/Victoria' => 'Australia/Melbourne',
         'Australia/West' => 'Australia/Perth',
         'Australia/Yancowinna' => 'Australia/Broken_Hill',
         'Brazil/Acre' => 'America/Rio_Branco',
         'Brazil/DeNoronha' => 'America/Noronha',
         'Brazil/East' => 'America/Sao_Paulo',
         'Brazil/West' => 'America/Manaus',
         'Canada/Atlantic' => 'America/Halifax',
         'Canada/Central' => 'America/Winnipeg',
         'Canada/East-Saskatchewan' => 'America/Regina',
         'Canada/Eastern' => 'America/Toronto',
         'Canada/Mountain' => 'America/Edmonton',
         'Canada/Newfoundland' => 'America/St_Johns',
         'Canada/Pacific' => 'America/Vancouver',
         'Canada/Saskatchewan' => 'America/Regina',
         'Canada/Yukon' => 'America/Whitehorse',
         'Chile/Continental' => 'America/Santiago',
         'Chile/EasterIsland' => 'Pacific/Easter',
         'Cuba' => 'America/Havana',
         'Egypt' => 'Africa/Cairo',
         'Eire' => 'Europe/Dublin',
         'Europe/Belfast' => 'Europe/London',
         'Europe/Tiraspol' => 'Europe/Chisinau',
         'GB' => 'Europe/London',
         'GB-Eire' => 'Europe/London',
         'Greenwich' => 'Etc/GMT',
         'Hongkong' => 'Asia/Hong_Kong',
         'Iceland' => 'Atlantic/Reykjavik',
         'Iran' => 'Asia/Tehran',
         'Israel' => 'Asia/Jerusalem',
         'Jamaica' => 'America/Jamaica',
         'Japan' => 'Asia/Tokyo',
         'Kwajalein' => 'Pacific/Kwajalein',
         'Libya' => 'Africa/Tripoli',
         'Mexico/BajaNorte' => 'America/Tijuana',
         'Mexico/BajaSur' => 'America/Mazatlan',
         'Mexico/General' => 'America/Mexico_City',
         'NZ' => 'Pacific/Auckland',
         'NZ-CHAT' => 'Pacific/Chatham',
         'Navajo' => 'America/Denver',
         'PRC' => 'Asia/Shanghai',
         'Pacific/Ponape' => 'Pacific/Pohnpei',
         'Pacific/Samoa' => 'Pacific/Pago_Pago',
         'Pacific/Truk' => 'Pacific/Chuuk',
         'Pacific/Yap' => 'Pacific/Chuuk',
         'Poland' => 'Europe/Warsaw',
         'Portugal' => 'Europe/Lisbon',
         'ROC' => 'Asia/Taipei',
         'ROK' => 'Asia/Seoul',
         'Singapore' => 'Asia/Singapore',
         'Turkey' => 'Europe/Istanbul',
         'UCT' => 'Etc/UCT',
         'US/Alaska' => 'America/Anchorage',
         'US/Aleutian' => 'America/Adak',
         'US/Arizona' => 'America/Phoenix',
         'US/Central' => 'America/Chicago',
         'US/East-Indiana' => 'America/Indiana/Indianapolis',
         'US/Eastern' => 'America/New_York',
         'US/Hawaii' => 'Pacific/Honolulu',
         'US/Indiana-Starke' => 'America/Indiana/Knox',
         'US/Michigan' => 'America/Detroit',
         'US/Mountain' => 'America/Denver',
         'US/Pacific' => 'America/Los_Angeles',
         'US/Samoa' => 'Pacific/Pago_Pago',
         'Universal' => 'Etc/UTC',
         'W-SU' => 'Europe/Moscow',
         'Zulu' => 'Etc/UTC',
     );
 
     /**
      * Factory method to instantiate a kolab_format object of the given type and version
      *
      * @param string Object type to instantiate
      * @param float  Format version
      * @param string Cached xml data to initialize with
      * @return object kolab_format
      */
     public static function factory($type, $version = '3.0', $xmldata = null)
     {
         if (!isset(self::$timezone))
             self::$timezone = new DateTimeZone('UTC');
 
         if (!self::supports($version))
             return PEAR::raiseError("No support for Kolab format version " . $version);
 
         $type = preg_replace('/configuration\.[a-z._]+$/', 'configuration', $type);
         $suffix = preg_replace('/[^a-z]+/', '', $type);
         $classname = 'kolab_format_' . $suffix;
         if (class_exists($classname))
             return new $classname($xmldata, $version);
 
         return PEAR::raiseError("Failed to load Kolab Format wrapper for type " . $type);
     }
 
     /**
      * Determine support for the given format version
      *
      * @param float Format version to check
      * @return boolean True if supported, False otherwise
      */
     public static function supports($version)
     {
         if ($version == '2.0')
             return class_exists('kolabobject');
         // default is version 3
         return class_exists('kolabformat');
     }
 
     /**
      * Convert the given date/time value into a cDateTime object
      *
      * @param mixed         Date/Time value either as unix timestamp, date string or PHP DateTime object
      * @param DateTimeZone  The timezone the date/time is in. Use global default if Null, local time if False
      * @param boolean       True of the given date has no time component
      * @return object       The libkolabxml date/time object
      */
     public static function get_datetime($datetime, $tz = null, $dateonly = false)
     {
         // use timezone information from datetime of global setting
         if (!$tz && $tz !== false) {
             if ($datetime instanceof DateTime)
                 $tz = $datetime->getTimezone();
             if (!$tz)
                 $tz = self::$timezone;
         }
         $result = new cDateTime();
 
         try {
             // got a unix timestamp (in UTC)
             if (is_numeric($datetime)) {
                 $datetime = new DateTime('@'.$datetime, new DateTimeZone('UTC'));
                 if ($tz) $datetime->setTimezone($tz);
             }
             else if (is_string($datetime) && strlen($datetime)) {
                 $datetime = $tz ? new DateTime($datetime, $tz) : new DateTime($datetime);
             }
         }
         catch (Exception $e) {}
 
         if ($datetime instanceof DateTime) {
             $result->setDate($datetime->format('Y'), $datetime->format('n'), $datetime->format('j'));
 
             if (!$dateonly)
                 $result->setTime($datetime->format('G'), $datetime->format('i'), $datetime->format('s'));
 
             if ($tz && in_array($tz->getName(), array('UTC', 'GMT', '+00:00', 'Z'))) {
                 $result->setUTC(true);
             }
             else if ($tz !== false) {
                 $tzid = $tz->getName();
                 if (array_key_exists($tzid, self::$timezone_map))
                     $tzid = self::$timezone_map[$tzid];
                 $result->setTimezone($tzid);
             }
         }
 
         return $result;
     }
 
     /**
      * Convert the given cDateTime into a PHP DateTime object
      *
      * @param object cDateTime  The libkolabxml datetime object
      * @return object DateTime  PHP datetime instance
      */
     public static function php_datetime($cdt)
     {
         if (!is_object($cdt) || !$cdt->isValid())
             return null;
 
         $d = new DateTime;
         $d->setTimezone(self::$timezone);
 
         try {
             if ($tzs = $cdt->timezone()) {
                 $tz = new DateTimeZone($tzs);
                 $d->setTimezone($tz);
             }
             else if ($cdt->isUTC()) {
                 $d->setTimezone(new DateTimeZone('UTC'));
             }
         }
         catch (Exception $e) { }
 
         $d->setDate($cdt->year(), $cdt->month(), $cdt->day());
 
         if ($cdt->isDateOnly()) {
             $d->_dateonly = true;
             $d->setTime(12, 0, 0);  // set time to noon to avoid timezone troubles
         }
         else {
             $d->setTime($cdt->hour(), $cdt->minute(), $cdt->second());
         }
 
         return $d;
     }
 
     /**
      * Convert a libkolabxml vector to a PHP array
      *
      * @param object vector Object
      * @return array Indexed array containing vector elements
      */
     public static function vector2array($vec, $max = PHP_INT_MAX)
     {
         $arr = array();
         for ($i=0; $i < $vec->size() && $i < $max; $i++)
             $arr[] = $vec->get($i);
         return $arr;
     }
 
     /**
      * Build a libkolabxml vector (string) from a PHP array
      *
      * @param array Array with vector elements
      * @return object vectors
      */
     public static function array2vector($arr)
     {
         $vec = new vectors;
         foreach ((array)$arr as $val) {
             if (strlen($val))
                 $vec->push($val);
         }
         return $vec;
     }
 
     /**
      * Parse the X-Kolab-Type header from MIME messages and return the object type in short form
      *
      * @param string X-Kolab-Type header value
      * @return string Kolab object type (contact,event,task,note,etc.)
      */
     public static function mime2object_type($x_kolab_type)
     {
         return preg_replace(
             array('/dictionary.[a-z.]+$/', '/contact.distlist$/'),
             array( 'dictionary',            'distribution-list'),
             substr($x_kolab_type, strlen(self::KTYPE_PREFIX))
         );
     }
 
 
     /**
      * Default constructor of all kolab_format_* objects
      */
     public function __construct($xmldata = null, $version = null)
     {
         $this->obj = new $this->objclass;
         $this->xmldata = $xmldata;
 
         if ($version)
             $this->version = $version;
 
         // use libkolab module if available
         if (class_exists('kolabobject'))
             $this->xmlobject = new XMLObject();
     }
 
     /**
      * Check for format errors after calling kolabformat::write*()
      *
      * @return boolean True if there were errors, False if OK
      */
     protected function format_errors()
     {
         $ret = $log = false;
         switch (kolabformat::error()) {
             case kolabformat::NoError:
                 $ret = false;
                 break;
             case kolabformat::Warning:
                 $ret = false;
                 $uid = is_object($this->obj) ? $this->obj->uid() : $this->data['uid'];
                 $log = "Warning @ $uid";
                 break;
             default:
                 $ret = true;
                 $log = "Error";
         }
 
         if ($log && !isset($this->formaterror)) {
             rcube::raise_error(array(
                 'code' => 660,
                 'type' => 'php',
                 'file' => __FILE__,
                 'line' => __LINE__,
                 'message' => "kolabformat $log: " . kolabformat::errorMessage(),
             ), true);
 
             $this->formaterror = $ret;
         }
 
         return $ret;
     }
 
     /**
      * Save the last generated UID to the object properties.
      * Should be called after kolabformat::writeXXXX();
      */
     protected function update_uid()
     {
         // get generated UID
         if (!$this->data['uid']) {
             if ($this->xmlobject) {
                 $this->data['uid'] = $this->xmlobject->getSerializedUID();
             }
             if (empty($this->data['uid'])) {
                 $this->data['uid'] = kolabformat::getSerializedUID();
             }
             $this->obj->setUid($this->data['uid']);
         }
     }
 
     /**
      * Initialize libkolabxml object with cached xml data
      */
     protected function init()
     {
         if (!$this->loaded) {
             if ($this->xmldata) {
                 $this->load($this->xmldata);
                 $this->xmldata = null;
             }
             $this->loaded = true;
         }
     }
 
     /**
      * Get constant value for libkolab's version parameter
      *
      * @param float Version value to convert
      * @return int Constant value of either kolabobject::KolabV2 or kolabobject::KolabV3 or false if kolabobject module isn't available
      */
     protected function libversion($v = null)
     {
         if (class_exists('kolabobject')) {
             $version = $v ?: $this->version;
             if ($version <= '2.0')
                 return kolabobject::KolabV2;
             else
                 return kolabobject::KolabV3;
         }
 
         return false;
     }
 
     /**
      * Determine the correct libkolab(xml) wrapper function for the given call
      * depending on the available PHP modules
      */
     protected function libfunc($func)
     {
         if (is_array($func) || strpos($func, '::'))
             return $func;
         else if (class_exists('kolabobject'))
             return array($this->xmlobject, $func);
         else
             return 'kolabformat::' . $func;
     }
 
     /**
      * Direct getter for object properties
      */
     public function __get($var)
     {
         return $this->data[$var];
     }
 
     /**
      * Load Kolab object data from the given XML block
      *
      * @param string XML data
      * @return boolean True on success, False on failure
      */
     public function load($xml)
     {
         $this->formaterror = null;
         $read_func = $this->libfunc($this->read_func);
 
         if (is_array($read_func))
             $r = call_user_func($read_func, $xml, $this->libversion());
         else
             $r = call_user_func($read_func, $xml, false);
 
         if (is_resource($r))
             $this->obj = new $this->objclass($r);
         else if (is_a($r, $this->objclass))
             $this->obj = $r;
 
         $this->loaded = !$this->format_errors();
     }
 
     /**
      * Write object data to XML format
      *
      * @param float Format version to write
      * @return string XML data
      */
     public function write($version = null)
     {
         $this->formaterror = null;
 
         $this->init();
         $write_func = $this->libfunc($this->write_func);
         if (is_array($write_func))
             $this->xmldata = call_user_func($write_func, $this->obj, $this->libversion($version), self::PRODUCT_ID);
         else
             $this->xmldata = call_user_func($write_func, $this->obj, self::PRODUCT_ID);
 
         if (!$this->format_errors())
             $this->update_uid();
         else
             $this->xmldata = null;
 
         return $this->xmldata;
     }
 
     /**
      * Set properties to the kolabformat object
      *
      * @param array  Object data as hash array
      */
     public function set(&$object)
     {
         $this->init();
 
         if (!empty($object['uid']))
             $this->obj->setUid($object['uid']);
 
         // set some automatic values if missing
         if (empty($object['created']) && method_exists($this->obj, 'setCreated')) {
             $cdt = $this->obj->created();
             $object['created'] = $cdt && $cdt->isValid() ? self::php_datetime($cdt) : new DateTime('now', new DateTimeZone('UTC'));
             if (!$cdt || !$cdt->isValid())
                 $this->obj->setCreated(self::get_datetime($object['created']));
         }
 
         $object['changed'] = new DateTime('now', new DateTimeZone('UTC'));
         $this->obj->setLastModified(self::get_datetime($object['changed']));
 
         // Save custom properties of the given object
         if (isset($object['x-custom']) && method_exists($this->obj, 'setCustomProperties')) {
             $vcustom = new vectorcs;
             foreach ((array)$object['x-custom'] as $cp) {
                 if (is_array($cp))
                     $vcustom->push(new CustomProperty($cp[0], $cp[1]));
             }
             $this->obj->setCustomProperties($vcustom);
         }
         // load custom properties from XML for caching (#2238) if method exists (#3125)
         else if (method_exists($this->obj, 'customProperties')) {
             $object['x-custom'] = array();
             $vcustom = $this->obj->customProperties();
             for ($i=0; $i < $vcustom->size(); $i++) {
                 $cp = $vcustom->get($i);
                 $object['x-custom'][] = array($cp->identifier, $cp->value);
             }
         }
     }
 
     /**
      * Convert the Kolab object into a hash array data structure
      *
      * @param array Additional data for merge
      *
      * @return array  Kolab object data as hash array
      */
     public function to_array($data = array())
     {
         $this->init();
 
         // read object properties into local data object
         $object = array(
             'uid'     => $this->obj->uid(),
             'changed' => self::php_datetime($this->obj->lastModified()),
         );
 
         // not all container support the created property
         if (method_exists($this->obj, 'created')) {
             $object['created'] = self::php_datetime($this->obj->created());
         }
 
         // read custom properties
         if (method_exists($this->obj, 'customProperties')) {
             $vcustom = $this->obj->customProperties();
             for ($i=0; $i < $vcustom->size(); $i++) {
                 $cp = $vcustom->get($i);
                 $object['x-custom'][] = array($cp->identifier, $cp->value);
             }
         }
 
         // merge with additional data, e.g. attachments from the message
         if ($data) {
             foreach ($data as $idx => $value) {
                 if (is_array($value)) {
                     $object[$idx] = array_merge((array)$object[$idx], $value);
                 }
                 else {
                     $object[$idx] = $value;
                 }
             }
         }
 
         return $object;
     }
 
     /**
      * Object validation method to be implemented by derived classes
      */
     abstract public function is_valid();
 
     /**
      * Callback for kolab_storage_cache to get object specific tags to cache
      *
      * @return array List of tags to save in cache
      */
     public function get_tags()
     {
         return array();
     }
 
     /**
      * Callback for kolab_storage_cache to get words to index for fulltext search
      *
      * @return array List of words to save in cache
      */
     public function get_words()
     {
         return array();
     }
 
     /**
      * Utility function to extract object attachment data
      *
      * @param array Hash array reference to append attachment data into
      */
     public function get_attachments(&$object, $all = false)
     {
         $this->init();
 
         // handle attachments
         $vattach = $this->obj->attachments();
         for ($i=0; $i < $vattach->size(); $i++) {
             $attach = $vattach->get($i);
 
             // skip cid: attachments which are mime message parts handled by kolab_storage_folder
             if (substr($attach->uri(), 0, 4) != 'cid:' && $attach->label()) {
                 $name    = $attach->label();
                 $key     = $name . (isset($object['_attachments'][$name]) ? '.'.$i : '');
                 $content = $attach->data();
                 $object['_attachments'][$key] = array(
                     'id'       => 'i:'.$i,
                     'name'     => $name,
                     'mimetype' => $attach->mimetype(),
                     'size'     => strlen($content),
                     'content'  => $content,
                 );
             }
             else if ($all && substr($attach->uri(), 0, 4) == 'cid:') {
                 $key = $attach->uri();
                 $object['_attachments'][$key] = array(
                     'id'       => $key,
                     'name'     => $attach->label(),
                     'mimetype' => $attach->mimetype(),
                 );
             }
             else if (in_array(substr($attach->uri(), 0, 4), array('http','imap'))) {
                 $object['links'][] = $attach->uri();
             }
         }
     }
 
     /**
      * Utility function to set attachment properties to the kolabformat object
      *
      * @param array  Object data as hash array
      * @param boolean True to always overwrite attachment information
      */
     protected function set_attachments($object, $write = true)
     {
         // save attachments
         $vattach = new vectorattachment;
         foreach ((array) $object['_attachments'] as $cid => $attr) {
             if (empty($attr))
                 continue;
             $attach = new Attachment;
             $attach->setLabel((string)$attr['name']);
             $attach->setUri('cid:' . $cid, $attr['mimetype'] ?: 'application/octet-stream');
             if ($attach->isValid()) {
                 $vattach->push($attach);
                 $write = true;
             }
             else {
                 rcube::raise_error(array(
                     'code' => 660,
                     'type' => 'php',
                     'file' => __FILE__,
                     'line' => __LINE__,
                     'message' => "Invalid attributes for attachment $cid: " . var_export($attr, true),
                 ), true);
             }
         }
 
         foreach ((array) $object['links'] as $link) {
             $attach = new Attachment;
             $attach->setUri($link, 'unknown');
             $vattach->push($attach);
             $write = true;
         }
 
         if ($write) {
             $this->obj->setAttachments($vattach);
         }
     }
+
+    /**
+     * Unified way of updating/deleting attachments of edited object
+     *
+     * @param array $object Kolab object data
+     * @param array $old    Old version of Kolab object
+     */
+    public static function merge_attachments(&$object, $old)
+    {
+        $object['_attachments'] = (array) $old['_attachments'];
+
+        // delete existing attachment(s)
+        if (!empty($object['deleted_attachments'])) {
+            foreach ($object['_attachments'] as $idx => $att) {
+                if ($object['deleted_attachments'] === true || in_array($att['id'], $object['deleted_attachments'])) {
+                    $object['_attachments'][$idx] = false;
+                }
+            }
+        }
+
+        // in kolab_storage attachments are indexed by content-id
+        foreach ((array) $object['attachments'] as $attachment) {
+            $key = null;
+
+            // Roundcube ID has nothing to do with the storage ID, remove it
+            // for uploaded/new attachments
+            // FIXME: Roundcube uses 'data', kolab_format uses 'content'
+            if ($attachment['content'] || $attachment['path'] || $attachment['data']) {
+                unset($attachment['id']);
+            }
+
+            if ($attachment['id']) {
+                foreach ((array) $object['_attachments'] as $cid => $att) {
+                    if ($att && $attachment['id'] == $att['id']) {
+                        $key = $cid;
+                    }
+                }
+            }
+            else {
+                // find attachment by name, so we can update it if exists
+                // and make sure there are no duplicates
+                foreach ((array) $object['_attachments'] as $cid => $att) {
+                    if ($att && $attachment['name'] == $att['name']) {
+                        $key = $cid;
+                    }
+                }
+            }
+
+            if ($key && $attachment['_deleted']) {
+                $object['_attachments'][$key] = false;
+            }
+            // replace existing entry
+            else if ($key) {
+                $object['_attachments'][$key] = $attachment;
+            }
+            // append as new attachment
+            else {
+                $object['_attachments'][] = $attachment;
+            }
+        }
+
+        unset($object['attachments']);
+        unset($object['deleted_attachments']);
+    }
 }
diff --git a/plugins/tasklist/drivers/kolab/tasklist_kolab_driver.php b/plugins/tasklist/drivers/kolab/tasklist_kolab_driver.php
index fe1af558..6f62819b 100644
--- a/plugins/tasklist/drivers/kolab/tasklist_kolab_driver.php
+++ b/plugins/tasklist/drivers/kolab/tasklist_kolab_driver.php
@@ -1,1754 +1,1716 @@
 <?php
 
 /**
  * Kolab Groupware driver for the Tasklist plugin
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class tasklist_kolab_driver extends tasklist_driver
 {
     // features supported by the backend
     public $alarms      = false;
     public $attachments = true;
     public $attendees   = true;
     public $undelete    = false; // task undelete action
     public $alarm_types = array('DISPLAY','AUDIO');
     public $search_more_results;
 
     private $rc;
     private $plugin;
     private $lists;
     private $folders = array();
     private $tasks   = array();
     private $tags    = array();
     private $bonnie_api = false;
 
 
     /**
      * Default constructor
      */
     public function __construct($plugin)
     {
         $this->rc     = $plugin->rc;
         $this->plugin = $plugin;
 
         if (kolab_storage::$version == '2.0') {
             $this->alarm_absolute = false;
         }
 
         // tasklist use fully encoded identifiers
         kolab_storage::$encode_ids = true;
 
         // get configuration for the Bonnie API
         $this->bonnie_api = libkolab::get_bonnie_api();
 
         $this->plugin->register_action('folder-acl', array($this, 'folder_acl'));
     }
 
     /**
      * Read available calendars for the current user and store them internally
      */
     private function _read_lists($force = false)
     {
         // already read sources
         if (isset($this->lists) && !$force) {
             return $this->lists;
         }
 
         // get all folders that have type "task"
         $folders = kolab_storage::sort_folders(kolab_storage::get_folders('task'));
         $this->lists = $this->folders = array();
 
         $delim = $this->rc->get_storage()->get_hierarchy_delimiter();
 
         // find default folder
         $default_index = 0;
         foreach ($folders as $i => $folder) {
             if ($folder->default && strpos($folder->name, $delim) === false)
                 $default_index = $i;
         }
 
         // put default folder (aka INBOX) on top of the list
         if ($default_index > 0) {
             $default_folder = $folders[$default_index];
             unset($folders[$default_index]);
             array_unshift($folders, $default_folder);
         }
 
         $prefs = $this->rc->config->get('kolab_tasklists', array());
 
         foreach ($folders as $folder) {
             $tasklist = $this->folder_props($folder, $prefs);
 
             $this->lists[$tasklist['id']] = $tasklist;
             $this->folders[$tasklist['id']] = $folder;
             $this->folders[$folder->name] = $folder;
         }
 
         return $this->lists;
     }
 
     /**
      * Derive list properties from the given kolab_storage_folder object
      */
     protected function folder_props($folder, $prefs)
     {
         if ($folder->get_namespace() == 'personal') {
             $norename = false;
             $editable = true;
             $rights = 'lrswikxtea';
             $alarms = true;
         }
         else {
             $alarms = false;
             $rights = 'lr';
             $editable = false;
             if (($myrights = $folder->get_myrights()) && !PEAR::isError($myrights)) {
                 $rights = $myrights;
                 if (strpos($rights, 't') !== false || strpos($rights, 'd') !== false)
                     $editable = strpos($rights, 'i');
             }
             $info = $folder->get_folder_info();
             $norename = $readonly || $info['norename'] || $info['protected'];
         }
 
         $list_id = $folder->id; #kolab_storage::folder_id($folder->name);
         $old_id = kolab_storage::folder_id($folder->name, false);
 
         if (!isset($prefs[$list_id]['showalarms']) && isset($prefs[$old_id]['showalarms'])) {
             $prefs[$list_id]['showalarms'] = $prefs[$old_id]['showalarms'];
         }
 
         return array(
             'id' => $list_id,
             'name' => $folder->get_name(),
             'listname' => $folder->get_foldername(),
             'editname' => $folder->get_foldername(),
             'color' => $folder->get_color('0000CC'),
             'showalarms' => isset($prefs[$list_id]['showalarms']) ? $prefs[$list_id]['showalarms'] : $alarms,
             'editable' => $editable,
             'rights'    => $rights,
             'norename' => $norename,
             'active' => $folder->is_active(),
             'parentfolder' => $folder->get_parent(),
             'default' => $folder->default,
             'virtual' => $folder->virtual,
             'children' => true,  // TODO: determine if that folder indeed has child folders
             'subscribed' => (bool)$folder->is_subscribed(),
             'removable' => !$folder->default,
             'subtype'  => $folder->subtype,
             'group' => $folder->default ? 'default' : $folder->get_namespace(),
             'class' => trim($folder->get_namespace() . ($folder->default ? ' default' : '')),
             'caldavuid' => $folder->get_uid(),
             'history' => !empty($this->bonnie_api),
         );
     }
 
     /**
      * Get a list of available task lists from this source
      */
     public function get_lists(&$tree = null)
     {
         $this->_read_lists();
 
         // attempt to create a default list for this user
         if (empty($this->lists) && !isset($this->search_more_results)) {
             $prop = array('name' => 'Tasks', 'color' => '0000CC', 'default' => true);
             if ($this->create_list($prop))
                 $this->_read_lists(true);
         }
 
         $folders = array();
         foreach ($this->lists as $id => $list) {
             if (!empty($this->folders[$id])) {
                 $folders[] = $this->folders[$id];
             }
         }
 
         // include virtual folders for a full folder tree
         if (!is_null($tree)) {
             $folders = kolab_storage::folder_hierarchy($folders, $tree);
         }
 
         $delim = $this->rc->get_storage()->get_hierarchy_delimiter();
         $prefs = $this->rc->config->get('kolab_tasklists', array());
 
         $lists = array();
         foreach ($folders as $folder) {
             $list_id   = $folder->id; // kolab_storage::folder_id($folder->name);
             $imap_path = explode($delim, $folder->name);
 
             // find parent
             do {
               array_pop($imap_path);
               $parent_id = kolab_storage::folder_id(join($delim, $imap_path));
             }
             while (count($imap_path) > 1 && !$this->folders[$parent_id]);
 
             // restore "real" parent ID
             if ($parent_id && !$this->folders[$parent_id]) {
                 $parent_id = kolab_storage::folder_id($folder->get_parent());
             }
 
             $fullname = $folder->get_name();
             $listname = $folder->get_foldername();
 
             // special handling for virtual folders
             if ($folder instanceof kolab_storage_folder_user) {
                 $lists[$list_id] = array(
                     'id'       => $list_id,
                     'name'     => $fullname,
                     'listname' => $listname,
                     'title'    => $folder->get_title(),
                     'virtual'  => true,
                     'editable' => false,
                     'rights'   => 'l',
                     'group'    => 'other virtual',
                     'class'    => 'user',
                     'parent'   => $parent_id,
                 );
             }
             else if ($folder->virtual) {
                 $lists[$list_id] = array(
                     'id'       => $list_id,
                     'name'     => $fullname,
                     'listname' => $listname,
                     'virtual'  => true,
                     'editable' => false,
                     'rights'   => 'l',
                     'group'    => $folder->get_namespace(),
                     'class'    => 'folder',
                     'parent'   => $parent_id,
                 );
             }
             else {
                 if (!$this->lists[$list_id]) {
                     $this->lists[$list_id] = $this->folder_props($folder, $prefs);
                     $this->folders[$list_id] = $folder;
                 }
                 $this->lists[$list_id]['parent'] = $parent_id;
                 $lists[$list_id] = $this->lists[$list_id];
             }
         }
 
         return $lists;
     }
 
     /**
      * Get the kolab_calendar instance for the given calendar ID
      *
      * @param string List identifier (encoded imap folder name)
      * @return object kolab_storage_folder Object nor null if list doesn't exist
      */
     protected function get_folder($id)
     {
         $this->_read_lists();
 
         // create list and folder instance if necesary
         if (!$this->lists[$id]) {
             $folder = kolab_storage::get_folder(kolab_storage::id_decode($id));
             if ($folder->type) {
                 $this->folders[$id] = $folder;
                 $this->lists[$id] = $this->folder_props($folder, $this->rc->config->get('kolab_tasklists', array()));
             }
         }
 
         return $this->folders[$id];
     }
 
 
     /**
      * Create a new list assigned to the current user
      *
      * @param array Hash array with list properties
      *        name: List name
      *       color: The color of the list
      *  showalarms: True if alarms are enabled
      * @return mixed ID of the new list on success, False on error
      */
     public function create_list(&$prop)
     {
         $prop['type'] = 'task' . ($prop['default'] ? '.default' : '');
         $prop['active'] = true; // activate folder by default
         $prop['subscribed'] = true;
         $folder = kolab_storage::folder_update($prop);
 
         if ($folder === false) {
             $this->last_error = kolab_storage::$last_error;
             return false;
         }
 
         // create ID
         $id = kolab_storage::folder_id($folder);
 
         $prefs['kolab_tasklists'] = $this->rc->config->get('kolab_tasklists', array());
 
         if (isset($prop['showalarms']))
             $prefs['kolab_tasklists'][$id]['showalarms'] = $prop['showalarms'] ? true : false;
 
         if ($prefs['kolab_tasklists'][$id])
             $this->rc->user->save_prefs($prefs);
 
         // force page reload to properly render folder hierarchy
         if (!empty($prop['parent'])) {
             $prop['_reload'] = true;
         }
         else {
             $folder = kolab_storage::get_folder($folder);
             $prop += $this->folder_props($folder, array());
         }
 
         return $id;
     }
 
     /**
      * Update properties of an existing tasklist
      *
      * @param array Hash array with list properties
      *          id: List Identifier
      *        name: List name
      *       color: The color of the list
      *  showalarms: True if alarms are enabled (if supported)
      * @return boolean True on success, Fales on failure
      */
     public function edit_list(&$prop)
     {
         if ($prop['id'] && ($folder = $this->get_folder($prop['id']))) {
             $prop['oldname'] = $folder->name;
             $prop['type'] = 'task';
             $newfolder = kolab_storage::folder_update($prop);
 
             if ($newfolder === false) {
                 $this->last_error = kolab_storage::$last_error;
                 return false;
             }
 
             // create ID
             $id = kolab_storage::folder_id($newfolder);
 
             // fallback to local prefs
             $prefs['kolab_tasklists'] = $this->rc->config->get('kolab_tasklists', array());
             unset($prefs['kolab_tasklists'][$prop['id']]);
 
             if (isset($prop['showalarms']))
                 $prefs['kolab_tasklists'][$id]['showalarms'] = $prop['showalarms'] ? true : false;
 
             if ($prefs['kolab_tasklists'][$id])
                 $this->rc->user->save_prefs($prefs);
 
             // force page reload if folder name/hierarchy changed
             if ($newfolder != $prop['oldname'])
                 $prop['_reload'] = true;
 
             return $id;
         }
 
         return false;
     }
 
     /**
      * Set active/subscribed state of a list
      *
      * @param array Hash array with list properties
      *          id: List Identifier
      *      active: True if list is active, false if not
      *   permanent: True if list is to be subscribed permanently
      * @return boolean True on success, Fales on failure
      */
     public function subscribe_list($prop)
     {
         if ($prop['id'] && ($folder = $this->get_folder($prop['id']))) {
             $ret = false;
             if (isset($prop['permanent']))
                 $ret |= $folder->subscribe(intval($prop['permanent']));
             if (isset($prop['active']))
                 $ret |= $folder->activate(intval($prop['active']));
 
             // apply to child folders, too
             if ($prop['recursive']) {
                 foreach ((array)kolab_storage::list_folders($folder->name, '*', 'task') as $subfolder) {
                     if (isset($prop['permanent']))
                         ($prop['permanent'] ? kolab_storage::folder_subscribe($subfolder) : kolab_storage::folder_unsubscribe($subfolder));
                     if (isset($prop['active']))
                         ($prop['active'] ? kolab_storage::folder_activate($subfolder) : kolab_storage::folder_deactivate($subfolder));
                 }
             }
 
             return $ret;
         }
 
         return false;
     }
 
     /**
      * Delete the given list with all its contents
      *
      * @param array Hash array with list properties
      *      id: list Identifier
      * @return boolean True on success, Fales on failure
      */
     public function delete_list($prop)
     {
         if ($prop['id'] && ($folder = $this->get_folder($prop['id']))) {
             if (kolab_storage::folder_delete($folder->name)) {
                 return true;
             }
 
             $this->last_error = kolab_storage::$last_error;
         }
 
         return false;
     }
 
     /**
      * Search for shared or otherwise not listed tasklists the user has access
      *
      * @param string Search string
      * @param string Section/source to search
      * @return array List of tasklists
      */
     public function search_lists($query, $source)
     {
         if (!kolab_storage::setup()) {
             return array();
         }
 
         $this->search_more_results = false;
         $this->lists = $this->folders = array();
 
         // find unsubscribed IMAP folders that have "event" type
         if ($source == 'folders') {
             foreach ((array)kolab_storage::search_folders('task', $query, array('other')) as $folder) {
                 $this->folders[$folder->id] = $folder;
                 $this->lists[$folder->id] = $this->folder_props($folder, array());
             }
         }
         // search other user's namespace via LDAP
         else if ($source == 'users') {
             $limit = $this->rc->config->get('autocomplete_max', 15) * 2;  // we have slightly more space, so display twice the number
             foreach (kolab_storage::search_users($query, 0, array(), $limit * 10) as $user) {
                 $folders = array();
                 // search for tasks folders shared by this user
                 foreach (kolab_storage::list_user_folders($user, 'task', false) as $foldername) {
                     $folders[] = new kolab_storage_folder($foldername, 'task');
                 }
 
                 if (count($folders)) {
                     $userfolder = new kolab_storage_folder_user($user['kolabtargetfolder'], '', $user);
                     $this->folders[$userfolder->id] = $userfolder;
                     $this->lists[$userfolder->id] = $this->folder_props($userfolder, array());
 
                     foreach ($folders as $folder) {
                         $this->folders[$folder->id] = $folder;
                         $this->lists[$folder->id] = $this->folder_props($folder, array());
                         $count++;
                     }
                 }
 
                 if ($count >= $limit) {
                     $this->search_more_results = true;
                     break;
                 }
             }
         }
 
         return $this->get_lists();
     }
 
     /**
      * Get a list of tags to assign tasks to
      *
      * @return array List of tags
      */
     public function get_tags()
     {
         $config = kolab_storage_config::get_instance();
         $tags   = $config->get_tags();
         $backend_tags = array_map(function($v) { return $v['name']; }, $tags);
 
         return array_values(array_unique(array_merge($this->tags, $backend_tags)));
     }
 
     /**
      * Get number of tasks matching the given filter
      *
      * @param array List of lists to count tasks of
      * @return array Hash array with counts grouped by status (all|flagged|completed|today|tomorrow|nodate)
      */
     public function count_tasks($lists = null)
     {
         if (empty($lists)) {
             $lists = $this->_read_lists();
             $lists = array_keys($lists);
         }
         else if (is_string($lists)) {
             $lists = explode(',', $lists);
         }
 
         $today_date    = new DateTime('now', $this->plugin->timezone);
         $today         = $today_date->format('Y-m-d');
         $tomorrow_date = new DateTime('now + 1 day', $this->plugin->timezone);
         $tomorrow      = $tomorrow_date->format('Y-m-d');
 
         $counts = array('all' => 0, 'flagged' => 0, 'today' => 0, 'tomorrow' => 0, 'overdue' => 0, 'nodate' => 0, 'mytasks' => 0);
 
         foreach ($lists as $list_id) {
             if (!$folder = $this->get_folder($list_id)) {
                 continue;
             }
 
             foreach ($folder->select(array(array('tags','!~','x-complete'))) as $record) {
                 $rec = $this->_to_rcube_task($record, $list_id, false);
 
                 if ($this->is_complete($rec))  // don't count complete tasks
                     continue;
 
                 $counts['all']++;
                 if ($rec['flagged'])
                     $counts['flagged']++;
                 if (empty($rec['date']))
                     $counts['nodate']++;
                 else if ($rec['date'] == $today)
                     $counts['today']++;
                 else if ($rec['date'] == $tomorrow)
                     $counts['tomorrow']++;
                 else if ($rec['date'] < $today)
                     $counts['overdue']++;
                 if ($this->plugin->is_attendee($rec) !== false)
                     $counts['mytasks']++;
             }
         }
 
         // avoid session race conditions that will loose temporary subscriptions
         $this->plugin->rc->session->nowrite = true;
 
         return $counts;
     }
 
     /**
      * Get all task records matching the given filter
      *
      * @param array Hash array with filter criterias:
      *  - mask:  Bitmask representing the filter selection (check against tasklist::FILTER_MASK_* constants)
      *  - from:  Date range start as string (Y-m-d)
      *  - to:    Date range end as string (Y-m-d)
      *  - search: Search query string
      * @param array List of lists to get tasks from
      * @return array List of tasks records matchin the criteria
      */
     public function list_tasks($filter, $lists = null)
     {
         if (empty($lists)) {
             $lists = $this->_read_lists();
             $lists = array_keys($lists);
         }
         else if (is_string($lists)) {
             $lists = explode(',', $lists);
         }
 
         $config  = kolab_storage_config::get_instance();
         $results = array();
 
         // query Kolab storage
         $query = array();
         if ($filter['mask'] & tasklist::FILTER_MASK_COMPLETE)
             $query[] = array('tags','~','x-complete');
         else if (empty($filter['since']))
             $query[] = array('tags','!~','x-complete');
 
         // full text search (only works with cache enabled)
         if ($filter['search']) {
             $search = mb_strtolower($filter['search']);
             foreach (rcube_utils::normalize_string($search, true) as $word) {
                 $query[] = array('words', '~', $word);
             }
         }
 
         if ($filter['since']) {
             $query[] = array('changed', '>=', $filter['since']);
         }
 
         foreach ($lists as $list_id) {
             if (!$folder = $this->get_folder($list_id)) {
                 continue;
             }
 
             foreach ($folder->select($query) as $record) {
                 // TODO: post-filter tasks returned from storage
                 $record['list_id'] = $list_id;
                 $results[] = $record;
             }
         }
 
         $config->apply_tags($results, true);
         $config->apply_links($results);
 
         foreach (array_keys($results) as $idx) {
             $results[$idx] = $this->_to_rcube_task($results[$idx], $results[$idx]['list_id']);
         }
 
         // avoid session race conditions that will loose temporary subscriptions
         $this->plugin->rc->session->nowrite = true;
 
         return $results;
     }
 
     /**
      * Return data of a specific task
      *
      * @param mixed  Hash array with task properties or task UID
      * @return array Hash array with task properties or false if not found
      */
     public function get_task($prop)
     {
         $this->_read_lists();
         $this->_parse_id($prop);
 
         $id      = $prop['uid'];
         $list_id = $prop['list'];
         $folders = $list_id ? array($list_id => $this->get_folder($list_id)) : $this->folders;
 
         // find task in the available folders
         foreach ($folders as $list_id => $folder) {
             if (is_numeric($list_id) || !$folder)
                 continue;
             if (!$this->tasks[$id] && ($object = $folder->get_object($id))) {
                 $this->load_tags($object);
                 $this->tasks[$id] = $this->_to_rcube_task($object, $list_id);
                 break;
             }
         }
 
         return $this->tasks[$id];
     }
 
     /**
      * Get all decendents of the given task record
      *
      * @param mixed  Hash array with task properties or task UID
      * @param boolean True if all childrens children should be fetched
      * @return array List of all child task IDs
      */
     public function get_childs($prop, $recursive = false)
     {
         if (is_string($prop)) {
             $task = $this->get_task($prop);
             $prop = array('uid' => $task['uid'], 'list' => $task['list']);
         }
         else {
             $this->_parse_id($prop);
         }
 
         $childs = array();
         $list_id = $prop['list'];
         $task_ids = array($prop['uid']);
         $folder = $this->get_folder($list_id);
 
         // query for childs (recursively)
         while ($folder && !empty($task_ids)) {
             $query_ids = array();
             foreach ($task_ids as $task_id) {
                 $query = array(array('tags','=','x-parent:' . $task_id));
                 foreach ($folder->select($query) as $record) {
                     // don't rely on kolab_storage_folder filtering
                     if ($record['parent_id'] == $task_id) {
                         $childs[] = $list_id . ':' . $record['uid'];
                         $query_ids[] = $record['uid'];
                     }
                 }
             }
 
             if (!$recursive)
                 break;
 
             $task_ids = $query_ids;
         }
 
         return $childs;
     }
 
     /**
      * Provide a list of revisions for the given task
      *
      * @param array  $task Hash array with task properties
      * @return array List of changes, each as a hash array
      * @see tasklist_driver::get_task_changelog()
      */
     public function get_task_changelog($prop)
     {
         if (empty($this->bonnie_api)) {
             return false;
         }
 
         list($uid, $mailbox, $msguid) = $this->_resolve_task_identity($prop);
 
         $result = $uid && $mailbox ? $this->bonnie_api->changelog('task', $uid, $mailbox, $msguid) : null;
         if (is_array($result) && $result['uid'] == $uid) {
             return $result['changes'];
         }
 
         return false;
     }
 
     /**
      * Return full data of a specific revision of an event
      *
      * @param mixed  $task UID string or hash array with task properties
      * @param mixed  $rev Revision number
      *
      * @return array Task object as hash array
      * @see tasklist_driver::get_task_revision()
      */
     public function get_task_revison($prop, $rev)
     {
         if (empty($this->bonnie_api)) {
             return false;
         }
 
         $this->_parse_id($prop);
         $uid     = $prop['uid'];
         $list_id = $prop['list'];
         list($uid, $mailbox, $msguid) = $this->_resolve_task_identity($prop);
 
         // call Bonnie API
         $result = $this->bonnie_api->get('task', $uid, $rev, $mailbox, $msguid);
         if (is_array($result) && $result['uid'] == $uid && !empty($result['xml'])) {
             $format = kolab_format::factory('task');
             $format->load($result['xml']);
             $rec = $format->to_array();
             $format->get_attachments($rec, true);
 
             if ($format->is_valid()) {
                 $rec = self::_to_rcube_task($rec, $list_id, false);
                 $rec['rev'] = $result['rev'];
                 return $rec;
             }
         }
 
         return false;
     }
 
     /**
      * Command the backend to restore a certain revision of a task.
      * This shall replace the current object with an older version.
      *
      * @param mixed  $task UID string or hash array with task properties
      * @param mixed  $rev Revision number
      *
      * @return boolean True on success, False on failure
      * @see tasklist_driver::restore_task_revision()
      */
     public function restore_task_revision($prop, $rev)
     {
         if (empty($this->bonnie_api)) {
             return false;
         }
 
         $this->_parse_id($prop);
         $uid     = $prop['uid'];
         $list_id = $prop['list'];
         list($uid, $mailbox, $msguid) = $this->_resolve_task_identity($prop);
 
         $folder  = $this->get_folder($list_id);
         $success = false;
 
         if ($folder && ($raw_msg = $this->bonnie_api->rawdata('task', $uid, $rev, $mailbox))) {
             $imap = $this->rc->get_storage();
 
             // insert $raw_msg as new message
             if ($imap->save_message($folder->name, $raw_msg, null, false)) {
                 $success = true;
 
                 // delete old revision from imap and cache
                 $imap->delete_message($msguid, $folder->name);
                 $folder->cache->set($msguid, false);
             }
         }
 
         return $success;
     }
 
     /**
      * Get a list of property changes beteen two revisions of a task object
      *
      * @param array  $task Hash array with task properties
      * @param mixed  $rev   Revisions: "from:to"
      *
      * @return array List of property changes, each as a hash array
      * @see tasklist_driver::get_task_diff()
      */
     public function get_task_diff($prop, $rev1, $rev2)
     {
         $this->_parse_id($prop);
         $uid     = $prop['uid'];
         $list_id = $prop['list'];
         list($uid, $mailbox, $msguid) = $this->_resolve_task_identity($prop);
 
         // call Bonnie API
         $result = $this->bonnie_api->diff('task', $uid, $rev1, $rev2, $mailbox, $msguid, $instance_id);
         if (is_array($result) && $result['uid'] == $uid) {
             $result['rev1'] = $rev1;
             $result['rev2'] = $rev2;
 
             $keymap = array(
                 'start'    => 'start',
                 'due'      => 'date',
                 'dstamp'   => 'changed',
                 'summary'  => 'title',
                 'alarm'    => 'alarms',
                 'attendee' => 'attendees',
                 'attach'   => 'attachments',
                 'rrule'    => 'recurrence',
                 'related-to' => 'parent_id',
                 'percent-complete' => 'complete',
                 'lastmodified-date' => 'changed',
             );
             $prop_keymaps = array(
                 'attachments' => array('fmttype' => 'mimetype', 'label' => 'name'),
                 'attendees'   => array('partstat' => 'status'),
             );
             $special_changes = array();
 
             // map kolab event properties to keys the client expects
             array_walk($result['changes'], function(&$change, $i) use ($keymap, $prop_keymaps, $special_changes) {
                 if (array_key_exists($change['property'], $keymap)) {
                     $change['property'] = $keymap[$change['property']];
                 }
                 if ($change['property'] == 'priority') {
                     $change['property'] = 'flagged';
                     $change['old'] = $change['old'] == 1 ? $this->plugin->gettext('yes') : null;
                     $change['new'] = $change['new'] == 1 ? $this->plugin->gettext('yes') : null;
                 }
                 // map alarms trigger value
                 if ($change['property'] == 'alarms') {
                     if (is_array($change['old']) && is_array($change['old']['trigger']))
                         $change['old']['trigger'] = $change['old']['trigger']['value'];
                     if (is_array($change['new']) && is_array($change['new']['trigger']))
                         $change['new']['trigger'] = $change['new']['trigger']['value'];
                 }
                 // make all property keys uppercase
                 if ($change['property'] == 'recurrence') {
                     $special_changes['recurrence'] = $i;
                     foreach (array('old','new') as $m) {
                         if (is_array($change[$m])) {
                             $props = array();
                             foreach ($change[$m] as $k => $v) {
                                 $props[strtoupper($k)] = $v;
                             }
                             $change[$m] = $props;
                         }
                     }
                 }
                 // map property keys names
                 if (is_array($prop_keymaps[$change['property']])) {
                   foreach ($prop_keymaps[$change['property']] as $k => $dest) {
                     if (is_array($change['old']) && array_key_exists($k, $change['old'])) {
                         $change['old'][$dest] = $change['old'][$k];
                         unset($change['old'][$k]);
                     }
                     if (is_array($change['new']) && array_key_exists($k, $change['new'])) {
                         $change['new'][$dest] = $change['new'][$k];
                         unset($change['new'][$k]);
                     }
                   }
                 }
 
                 if ($change['property'] == 'exdate') {
                     $special_changes['exdate'] = $i;
                 }
                 else if ($change['property'] == 'rdate') {
                     $special_changes['rdate'] = $i;
                 }
             });
 
             // merge some recurrence changes
             foreach (array('exdate','rdate') as $prop) {
                 if (array_key_exists($prop, $special_changes)) {
                     $exdate = $result['changes'][$special_changes[$prop]];
                     if (array_key_exists('recurrence', $special_changes)) {
                         $recurrence = &$result['changes'][$special_changes['recurrence']];
                     }
                     else {
                         $i = count($result['changes']);
                         $result['changes'][$i] = array('property' => 'recurrence', 'old' => array(), 'new' => array());
                         $recurrence = &$result['changes'][$i]['recurrence'];
                     }
                     $key = strtoupper($prop);
                     $recurrence['old'][$key] = $exdate['old'];
                     $recurrence['new'][$key] = $exdate['new'];
                     unset($result['changes'][$special_changes[$prop]]);
                 }
             }
 
             return $result;
         }
 
         return false;
     }
 
     /**
      * Helper method to resolved the given task identifier into uid and folder
      *
      * @return array (uid,folder,msguid) tuple
      */
     private function _resolve_task_identity($prop)
     {
         $mailbox = $msguid = null;
 
         $this->_parse_id($prop);
         $uid     = $prop['uid'];
         $list_id = $prop['list'];
 
         if ($folder = $this->get_folder($list_id)) {
             $mailbox = $folder->get_mailbox_id();
 
             // get task object from storage in order to get the real object uid an msguid
             if ($rec = $folder->get_object($uid)) {
                 $msguid = $rec['_msguid'];
                 $uid = $rec['uid'];
             }
         }
 
         return array($uid, $mailbox, $msguid);
     }
 
     /**
      * Get a list of pending alarms to be displayed to the user
      *
      * @param  integer Current time (unix timestamp)
      * @param  mixed   List of list IDs to show alarms for (either as array or comma-separated string)
      * @return array   A list of alarms, each encoded as hash array with task properties
      * @see tasklist_driver::pending_alarms()
      */
     public function pending_alarms($time, $lists = null)
     {
         $interval = 300;
         $time -= $time % 60;
 
         $slot = $time;
         $slot -= $slot % $interval;
 
         $last = $time - max(60, $this->rc->config->get('refresh_interval', 0));
         $last -= $last % $interval;
 
         // only check for alerts once in 5 minutes
         if ($last == $slot)
             return array();
 
         if ($lists && is_string($lists))
             $lists = explode(',', $lists);
 
         $time = $slot + $interval;
 
         $candidates = array();
         $query      = array(
             array('tags', '=', 'x-has-alarms'),
             array('tags', '!=', 'x-complete')
         );
 
         $this->_read_lists();
 
         foreach ($this->lists as $lid => $list) {
             // skip lists with alarms disabled
             if (!$list['showalarms'] || ($lists && !in_array($lid, $lists)))
                 continue;
 
             $folder = $this->get_folder($lid);
             foreach ($folder->select($query) as $record) {
                 if (!($record['valarms'] || $record['alarms']) || $record['status'] == 'COMPLETED' || $record['complete'] == 100)  // don't trust query :-)
                     continue;
 
                 $task = $this->_to_rcube_task($record, $lid, false);
 
                 // add to list if alarm is set
                 $alarm = libcalendaring::get_next_alarm($task, 'task');
                 if ($alarm && $alarm['time'] && $alarm['time'] <= $time && in_array($alarm['action'], $this->alarm_types)) {
                     $id = $alarm['id'];  // use alarm-id as primary identifier
                     $candidates[$id] = array(
                         'id'       => $id,
                         'title'    => $task['title'],
                         'date'     => $task['date'],
                         'time'     => $task['time'],
                         'notifyat' => $alarm['time'],
                         'action'   => $alarm['action'],
                     );
                 }
             }
         }
 
         // get alarm information stored in local database
         if (!empty($candidates)) {
             $alarm_ids = array_map(array($this->rc->db, 'quote'), array_keys($candidates));
             $result = $this->rc->db->query("SELECT *"
                 . " FROM " . $this->rc->db->table_name('kolab_alarms', true)
                 . " WHERE `alarm_id` IN (" . join(',', $alarm_ids) . ")"
                     . " AND `user_id` = ?",
                 $this->rc->user->ID
             );
 
             while ($result && ($rec = $this->rc->db->fetch_assoc($result))) {
                 $dbdata[$rec['alarm_id']] = $rec;
             }
         }
 
         $alarms = array();
         foreach ($candidates as $id => $task) {
           // skip dismissed
           if ($dbdata[$id]['dismissed'])
               continue;
 
           // snooze function may have shifted alarm time
           $notifyat = $dbdata[$id]['notifyat'] ? strtotime($dbdata[$id]['notifyat']) : $task['notifyat'];
           if ($notifyat <= $time)
               $alarms[] = $task;
         }
 
         return $alarms;
     }
 
     /**
      * (User) feedback after showing an alarm notification
      * This should mark the alarm as 'shown' or snooze it for the given amount of time
      *
      * @param  string  Task identifier
      * @param  integer Suspend the alarm for this number of seconds
      */
     public function dismiss_alarm($id, $snooze = 0)
     {
         // delete old alarm entry
         $this->rc->db->query(
             "DELETE FROM " . $this->rc->db->table_name('kolab_alarms', true) . "
              WHERE `alarm_id` = ? AND `user_id` = ?",
             $id,
             $this->rc->user->ID
         );
 
         // set new notifyat time or unset if not snoozed
         $notifyat = $snooze > 0 ? date('Y-m-d H:i:s', time() + $snooze) : null;
 
         $query = $this->rc->db->query(
             "INSERT INTO " . $this->rc->db->table_name('kolab_alarms', true) . "
              (`alarm_id`, `user_id`, `dismissed`, `notifyat`)
              VALUES (?, ?, ?, ?)",
             $id,
             $this->rc->user->ID,
             $snooze > 0 ? 0 : 1,
             $notifyat
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Remove alarm dismissal or snooze state
      *
      * @param  string  Task identifier
      */
     public function clear_alarms($id)
     {
         // delete alarm entry
         $this->rc->db->query(
             "DELETE FROM " . $this->rc->db->table_name('kolab_alarms', true) . "
              WHERE `alarm_id` = ? AND `user_id` = ?",
             $id,
             $this->rc->user->ID
         );
 
         return true;
     }
 
     /**
      * Get task tags
      */
     private function load_tags(&$object)
     {
         // this task hasn't been migrated yet
         if (!empty($object['categories'])) {
             // OPTIONAL: call kolab_storage_config::apply_tags() to migrate the object
             $object['tags'] = (array)$object['categories'];
             if (!empty($object['tags'])) {
                 $this->tags = array_merge($this->tags, $object['tags']);
             }
         }
         else {
             $config = kolab_storage_config::get_instance();
             $tags   = $config->get_tags($object['uid']);
             $object['tags'] = array_map(function($v) { return $v['name']; }, $tags);
         }
     }
 
     /**
      * Update task tags
      */
     private function save_tags($uid, $tags)
     {
         $config = kolab_storage_config::get_instance();
         $config->save_tags($uid, $tags);
     }
 
     /**
      * Find messages linked with a task record
      */
     private function get_links($uid)
     {
         $config = kolab_storage_config::get_instance();
         return $config->get_object_links($uid);
     }
 
     /**
      *
      */
     private function save_links($uid, $links)
     {
         $config = kolab_storage_config::get_instance();
         return $config->save_object_links($uid, (array) $links);
     }
 
     /**
      * Extract uid + list identifiers from the given input
      *
      * @param mixed array or string with task identifier(s)
      */
     private function _parse_id(&$prop)
     {
         $id_ = null;
         if (is_array($prop)) {
             // 'uid' + 'list' available, nothing to be done
             if (!empty($prop['uid']) && !empty($prop['list'])) {
                 return;
             }
 
             // 'id' is given
             if (!empty($prop['id'])) {
                 if (!empty($prop['list'])) {
                     $list_id = $prop['_fromlist'] ?: $prop['list'];
                     if (strpos($prop['id'], $list_id.':') === 0) {
                         $prop['uid'] = substr($prop['id'], strlen($list_id)+1);
                     }
                     else {
                         $prop['uid'] = $prop['id'];
                     }
                 }
                 else {
                     $id_ = $prop['id'];
                 }
             }
         }
         else {
             $id_ = strval($prop);
             $prop = array();
         }
 
         // split 'id' into list + uid
         if (!empty($id_)) {
             list($list, $uid) = explode(':', $id_, 2);
             if (!empty($uid)) {
                 $prop['uid'] = $uid;
                 $prop['list'] = $list;
             }
             else {
                 $prop['uid'] = $id_;
             }
         }
     }
 
     /**
      * Convert from Kolab_Format to internal representation
      */
     private function _to_rcube_task($record, $list_id, $all = true)
     {
         $id_prefix = $list_id . ':';
         $task = array(
             'id' => $id_prefix . $record['uid'],
             'uid' => $record['uid'],
             'title' => $record['title'],
 //            'location' => $record['location'],
             'description' => $record['description'],
             'flagged' => $record['priority'] == 1,
             'complete' => floatval($record['complete'] / 100),
             'status' => $record['status'],
             'parent_id' => $record['parent_id'] ? $id_prefix . $record['parent_id'] : null,
             'recurrence' => $record['recurrence'],
             'attendees' => $record['attendees'],
             'organizer' => $record['organizer'],
             'sequence' => $record['sequence'],
             'tags' => $record['tags'],
             'list' => $list_id,
             'links' => $record['links'],
         );
 
         // we can sometimes skip this expensive operation
         if ($all && !array_key_exists('links', $task)) {
             $task['links'] = $this->get_links($task['uid']);
         }
 
         // convert from DateTime to internal date format
         if (is_a($record['due'], 'DateTime')) {
             $due = $this->plugin->lib->adjust_timezone($record['due']);
             $task['date'] = $due->format('Y-m-d');
             if (!$record['due']->_dateonly)
                 $task['time'] = $due->format('H:i');
         }
         // convert from DateTime to internal date format
         if (is_a($record['start'], 'DateTime')) {
             $start = $this->plugin->lib->adjust_timezone($record['start']);
             $task['startdate'] = $start->format('Y-m-d');
             if (!$record['start']->_dateonly)
                 $task['starttime'] = $start->format('H:i');
         }
         if (is_a($record['changed'], 'DateTime')) {
             $task['changed'] = $record['changed'];
         }
         if (is_a($record['created'], 'DateTime')) {
             $task['created'] = $record['created'];
         }
 
         if ($record['valarms']) {
             $task['valarms'] = $record['valarms'];
         }
         else if ($record['alarms']) {
             $task['alarms'] = $record['alarms'];
         }
 
         if (!empty($task['attendees'])) {
             foreach ((array)$task['attendees'] as $i => $attendee) {
                 if (is_array($attendee['delegated-from'])) {
                     $task['attendees'][$i]['delegated-from'] = join(', ', $attendee['delegated-from']);
                 }
                 if (is_array($attendee['delegated-to'])) {
                     $task['attendees'][$i]['delegated-to'] = join(', ', $attendee['delegated-to']);
                 }
             }
         }
 
         if (!empty($record['_attachments'])) {
             foreach ($record['_attachments'] as $key => $attachment) {
                 if ($attachment !== false) {
                     if (!$attachment['name'])
                         $attachment['name'] = $key;
                     $attachments[] = $attachment;
                 }
             }
 
             $task['attachments'] = $attachments;
         }
 
         return $task;
     }
 
     /**
      * Convert the given task record into a data structure that can be passed to kolab_storage backend for saving
      * (opposite of self::_to_rcube_event())
      */
     private function _from_rcube_task($task, $old = array())
     {
         $object    = $task;
         $id_prefix = $task['list'] . ':';
 
         if (!empty($task['date'])) {
             $object['due'] = rcube_utils::anytodatetime($task['date'].' '.$task['time'], $this->plugin->timezone);
             if (empty($task['time']))
                 $object['due']->_dateonly = true;
             unset($object['date']);
         }
 
         if (!empty($task['startdate'])) {
             $object['start'] = rcube_utils::anytodatetime($task['startdate'].' '.$task['starttime'], $this->plugin->timezone);
             if (empty($task['starttime']))
                 $object['start']->_dateonly = true;
             unset($object['startdate']);
         }
 
         // as per RFC (and the Kolab schema validation), start and due dates need to be of the same type (#3614)
         // this should be catched in the client already but just make sure we don't write invalid objects
         if (!empty($object['start']) && !empty($object['due']) && $object['due']->_dateonly != $object['start']->_dateonly) {
             $object['start']->_dateonly = true;
             $object['due']->_dateonly = true;
         }
 
         $object['complete'] = $task['complete'] * 100;
         if ($task['complete'] == 1.0 && empty($task['complete']))
             $object['status'] = 'COMPLETED';
 
         if ($task['flagged'])
             $object['priority'] = 1;
         else
             $object['priority'] = $old['priority'] > 1 ? $old['priority'] : 0;
 
         // remove list: prefix from parent_id
         if (!empty($task['parent_id']) && strpos($task['parent_id'], $id_prefix) === 0) {
             $object['parent_id'] = substr($task['parent_id'], strlen($id_prefix));
         }
 
         // copy meta data (starting with _) from old object
         foreach ((array)$old as $key => $val) {
             if (!isset($object[$key]) && $key[0] == '_')
                 $object[$key] = $val;
         }
 
         // copy recurrence rules if the client didn't submit it (#2713)
         if (!array_key_exists('recurrence', $object) && $old['recurrence']) {
             $object['recurrence'] = $old['recurrence'];
         }
 
-        // delete existing attachment(s)
-        if (!empty($task['deleted_attachments'])) {
-            foreach ($task['deleted_attachments'] as $attachment) {
-                if (is_array($object['_attachments'])) {
-                    foreach ($object['_attachments'] as $idx => $att) {
-                        if ($att['id'] == $attachment)
-                            $object['_attachments'][$idx] = false;
-                    }
-                }
-            }
-            unset($task['deleted_attachments']);
-        }
-
-        // in kolab_storage attachments are indexed by content-id
-        if (is_array($task['attachments'])) {
-            foreach ($task['attachments'] as $idx => $attachment) {
-                $key = null;
-                // Roundcube ID has nothing to do with the storage ID, remove it
-                if ($attachment['content'] || $attachment['path']) {
-                    unset($attachment['id']);
-                }
-                else {
-                    foreach ((array)$old['_attachments'] as $cid => $oldatt) {
-                        if ($oldatt && $attachment['id'] == $oldatt['id'])
-                            $key = $cid;
-                    }
-                }
-
-                // replace existing entry
-                if ($key) {
-                    $object['_attachments'][$key] = $attachment;
-                }
-                // append as new attachment
-                else {
-                    $object['_attachments'][] = $attachment;
-                }
-            }
-
-            unset($object['attachments']);
-        }
+        unset($task['attachments']);
+        kolab_format::merge_attachments($object, $old);
 
         // allow sequence increments if I'm the organizer
         if ($this->plugin->is_organizer($object) && empty($object['_method'])) {
             unset($object['sequence']);
         }
         else if (isset($old['sequence']) && empty($object['_method'])) {
             $object['sequence'] = $old['sequence'];
         }
 
         unset($object['tempid'], $object['raw'], $object['list'], $object['flagged'], $object['tags'], $object['created']);
         return $object;
     }
 
     /**
      * Add a single task to the database
      *
      * @param array Hash array with task properties (see header of tasklist_driver.php)
      * @return mixed New task ID on success, False on error
      */
     public function create_task($task)
     {
         return $this->edit_task($task);
     }
 
     /**
      * Update an task entry with the given data
      *
      * @param array Hash array with task properties (see header of tasklist_driver.php)
      * @return boolean True on success, False on error
      */
     public function edit_task($task)
     {
         $this->_parse_id($task);
         $list_id = $task['list'];
         if (!$list_id || !($folder = $this->get_folder($list_id))) {
             rcube::raise_error(array(
                 'code' => 600, 'type' => 'php',
                 'file' => __FILE__, 'line' => __LINE__,
                 'message' => "Invalid list identifer to save task: " . print_r($list_id, true)),
                 true, false);
             return false;
         }
 
         // email links and tags are stored separately
         $links = $task['links'];
         $tags  = $task['tags'];
         unset($task['tags'], $task['links']);
 
         // moved from another folder
         if ($task['_fromlist'] && ($fromfolder = $this->get_folder($task['_fromlist']))) {
             if (!$fromfolder->move($task['uid'], $folder))
                 return false;
 
             unset($task['_fromlist']);
         }
 
         // load previous version of this task to merge
         if ($task['id']) {
             $old = $folder->get_object($task['uid']);
             if (!$old || PEAR::isError($old))
                 return false;
 
             // merge existing properties if the update isn't complete
             if (!isset($task['title']) || !isset($task['complete']))
                 $task += $this->_to_rcube_task($old, $list_id);
         }
 
         // generate new task object from RC input
         $object = $this->_from_rcube_task($task, $old);
         $saved  = $folder->save($object, 'task', $task['uid']);
 
         if (!$saved) {
             rcube::raise_error(array(
                 'code' => 600, 'type' => 'php',
                 'file' => __FILE__, 'line' => __LINE__,
                 'message' => "Error saving task object to Kolab server"),
                 true, false);
             $saved = false;
         }
         else {
             // save links in configuration.relation object
             $this->save_links($object['uid'], $links);
             // save tags in configuration.relation object
             $this->save_tags($object['uid'], $tags);
 
             $task = $this->_to_rcube_task($object, $list_id);
             $task['tags'] = (array) $tags;
             $this->tasks[$task['uid']] = $task;
         }
 
         return $saved;
     }
 
     /**
      * Move a single task to another list
      *
      * @param array   Hash array with task properties:
      * @return boolean True on success, False on error
      * @see tasklist_driver::move_task()
      */
     public function move_task($task)
     {
         $this->_parse_id($task);
         $list_id = $task['list'];
         if (!$list_id || !($folder = $this->get_folder($list_id)))
             return false;
 
         // execute move command
         if ($task['_fromlist'] && ($fromfolder = $this->get_folder($task['_fromlist']))) {
             return $fromfolder->move($task['uid'], $folder);
         }
 
         return false;
     }
 
     /**
      * Remove a single task from the database
      *
      * @param array   Hash array with task properties:
      *      id: Task identifier
      * @param boolean Remove record irreversible (mark as deleted otherwise, if supported by the backend)
      * @return boolean True on success, False on error
      */
     public function delete_task($task, $force = true)
     {
         $this->_parse_id($task);
         $list_id = $task['list'];
         if (!$list_id || !($folder = $this->get_folder($list_id)))
             return false;
 
         $status = $folder->delete($task['uid']);
 
         if ($status) {
             // remove tag assignments
             // @TODO: don't do this when undelete feature will be implemented
             $this->save_tags($task['uid'], null);
         }
 
         return $status;
     }
 
     /**
      * Restores a single deleted task (if supported)
      *
      * @param array Hash array with task properties:
      *      id: Task identifier
      * @return boolean True on success, False on error
      */
     public function undelete_task($prop)
     {
         // TODO: implement this
         return false;
     }
 
 
     /**
      * Get attachment properties
      *
      * @param string $id    Attachment identifier
      * @param array  $task  Hash array with event properties:
      *         id: Task identifier
      *       list: List identifier
      *        rev: Revision (optional)
      *
      * @return array Hash array with attachment properties:
      *         id: Attachment identifier
      *       name: Attachment name
      *   mimetype: MIME content type of the attachment
      *       size: Attachment size
      */
     public function get_attachment($id, $task)
     {
         // get old revision of the object
         if ($task['rev']) {
             $task = $this->get_task_revison($task, $task['rev']);
         }
         else {
             $task = $this->get_task($task);
         }
 
         if ($task && !empty($task['attachments'])) {
             foreach ($task['attachments'] as $att) {
                 if ($att['id'] == $id)
                     return $att;
             }
         }
 
         return null;
     }
 
     /**
      * Get attachment body
      *
      * @param string $id    Attachment identifier
      * @param array  $task  Hash array with event properties:
      *         id: Task identifier
      *       list: List identifier
      *        rev: Revision (optional)
      *
      * @return string Attachment body
      */
     public function get_attachment_body($id, $task)
     {
         $this->_parse_id($task);
 
         // get old revision of event
         if ($task['rev']) {
             if (empty($this->bonnie_api)) {
                 return false;
             }
 
             $cid = substr($id, 4);
 
             // call Bonnie API and get the raw mime message
             list($uid, $mailbox, $msguid) = $this->_resolve_task_identity($task);
             if ($msg_raw = $this->bonnie_api->rawdata('task', $uid, $task['rev'], $mailbox, $msguid)) {
                 // parse the message and find the part with the matching content-id
                 $message = rcube_mime::parse_message($msg_raw);
                 foreach ((array)$message->parts as $part) {
                     if ($part->headers['content-id'] && trim($part->headers['content-id'], '<>') == $cid) {
                         return $part->body;
                     }
                 }
             }
 
             return false;
         }
 
 
         if ($storage = $this->get_folder($task['list'])) {
             return $storage->get_attachment($task['uid'], $id);
         }
 
         return false;
     }
 
     /**
      * Build a struct representing the given message reference
      *
      * @see tasklist_driver::get_message_reference()
      */
     public function get_message_reference($uri_or_headers, $folder = null)
     {
         if (is_object($uri_or_headers)) {
             $uri_or_headers = kolab_storage_config::get_message_uri($uri_or_headers, $folder);
         }
 
         if (is_string($uri_or_headers)) {
             return kolab_storage_config::get_message_reference($uri_or_headers, 'task');
         }
 
         return false;
     }
 
     /**
      * Find tasks assigned to a specified message
      *
      * @see tasklist_driver::get_message_related_tasks()
      */
     public function get_message_related_tasks($headers, $folder)
     {
         $config = kolab_storage_config::get_instance();
         $result = $config->get_message_relations($headers, $folder, 'task');
 
         foreach ($result as $idx => $rec) {
             $result[$idx] = $this->_to_rcube_task($rec, kolab_storage::folder_id($rec['_mailbox']));
         }
 
         return $result;
     }
 
     /**
      * 
      */
     public function tasklist_edit_form($action, $list, $fieldprop)
     {
         $this->_read_lists();
 
         if ($list['id'] && ($list = $this->lists[$list['id']])) {
             $folder_name = $this->get_folder($list['id'])->name; // UTF7
         }
         else {
             $folder_name = '';
         }
 
         $storage = $this->rc->get_storage();
         $delim   = $storage->get_hierarchy_delimiter();
         $form    = array();
 
         if (strlen($folder_name)) {
             $path_imap = explode($delim, $folder_name);
             array_pop($path_imap);  // pop off name part
             $path_imap = implode($path_imap, $delim);
 
             $options = $storage->folder_info($folder_name);
         }
         else {
             $path_imap = '';
         }
 
         $hidden_fields[] = array('name' => 'oldname', 'value' => $folder_name);
 
         // folder name (default field)
         $input_name = new html_inputfield(array('name' => 'name', 'id' => 'taskedit-tasklistame', 'size' => 20));
         $fieldprop['name']['value'] = $input_name->show($list['editname'], array('disabled' => ($options['norename'] || $options['protected'])));
 
         // prevent user from moving folder
         if (!empty($options) && ($options['norename'] || $options['protected'])) {
             $hidden_fields[] = array('name' => 'parent', 'value' => $path_imap);
         }
         else {
             $select = kolab_storage::folder_selector('task', array('name' => 'parent', 'id' => 'taskedit-parentfolder'), $folder_name);
             $fieldprop['parent'] = array(
                 'id'    => 'taskedit-parentfolder',
                 'label' => $this->plugin->gettext('parentfolder'),
                 'value' => $select->show($path_imap),
             );
         }
 
         // General tab
         $form['properties'] = array(
             'name' => $this->rc->gettext('properties'),
             'fields' => array(),
         );
 
         foreach (array('name','parent','showalarms') as $f) {
             $form['properties']['fields'][$f] = $fieldprop[$f];
         }
 
         // add folder ACL tab
         if ($action != 'form-new') {
             $form['sharing'] = array(
                 'name'    => rcube::Q($this->plugin->gettext('tabsharing')),
                 'content' => html::tag('iframe', array(
                     'src' => $this->rc->url(array('_action' => 'folder-acl', '_folder' => $folder_name, 'framed' => 1)),
                     'width' => '100%',
                     'height' => 280,
                     'border' => 0,
                     'style' => 'border:0'),
                 '')
             );
         }
 
         $form_html = '';
         if (is_array($hidden_fields)) {
             foreach ($hidden_fields as $field) {
                 $hiddenfield = new html_hiddenfield($field);
                 $form_html .= $hiddenfield->show() . "\n";
             }
         }
 
         // create form output
         foreach ($form as $tab) {
             if (is_array($tab['fields']) && empty($tab['content'])) {
                 $table = new html_table(array('cols' => 2));
                 foreach ($tab['fields'] as $col => $colprop) {
                     $label = !empty($colprop['label']) ? $colprop['label'] : $this->plugin->gettext($col);
 
                     $table->add('title', html::label($colprop['id'], rcube::Q($label)));
                     $table->add(null, $colprop['value']);
                 }
                 $content = $table->show();
             }
             else {
                 $content = $tab['content'];
             }
 
             if (!empty($content)) {
                 $form_html .= html::tag('fieldset', null, html::tag('legend', null, rcube::Q($tab['name'])) . $content) . "\n";
             }
         }
 
         return $form_html;
     }
 
     /**
      * Handler to render ACL form for a notes folder
      */
     public function folder_acl()
     {
         $this->plugin->require_plugin('acl');
         $this->rc->output->add_handler('folderacl', array($this, 'folder_acl_form'));
         $this->rc->output->send('tasklist.kolabacl');
     }
 
     /**
      * Handler for ACL form template object
      */
     public function folder_acl_form()
     {
         $folder = rcube_utils::get_input_value('_folder', rcube_utils::INPUT_GPC);
 
         if (strlen($folder)) {
             $storage = $this->rc->get_storage();
             $options = $storage->folder_info($folder);
 
             // get sharing UI from acl plugin
             $acl = $this->rc->plugins->exec_hook('folder_form',
                 array('form' => array(), 'options' => $options, 'name' => $folder));
         }
 
         return $acl['form']['sharing']['content'] ?: html::div('hint', $this->plugin->gettext('aclnorights'));
     }
 }
diff --git a/plugins/tasklist/tasklist.php b/plugins/tasklist/tasklist.php
index c4305abb..16518a57 100644
--- a/plugins/tasklist/tasklist.php
+++ b/plugins/tasklist/tasklist.php
@@ -1,2337 +1,2346 @@
 <?php
 
 /**
  * Tasks plugin for Roundcube webmail
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class tasklist extends rcube_plugin
 {
     const FILTER_MASK_TODAY = 1;
     const FILTER_MASK_TOMORROW = 2;
     const FILTER_MASK_WEEK = 4;
     const FILTER_MASK_LATER = 8;
     const FILTER_MASK_NODATE = 16;
     const FILTER_MASK_OVERDUE = 32;
     const FILTER_MASK_FLAGGED = 64;
     const FILTER_MASK_COMPLETE = 128;
     const FILTER_MASK_ASSIGNED = 256;
     const FILTER_MASK_MYTASKS = 512;
 
     const SESSION_KEY = 'tasklist_temp';
 
     public static $filter_masks = array(
         'today'    => self::FILTER_MASK_TODAY,
         'tomorrow' => self::FILTER_MASK_TOMORROW,
         'week'     => self::FILTER_MASK_WEEK,
         'later'    => self::FILTER_MASK_LATER,
         'nodate'   => self::FILTER_MASK_NODATE,
         'overdue'  => self::FILTER_MASK_OVERDUE,
         'flagged'  => self::FILTER_MASK_FLAGGED,
         'complete' => self::FILTER_MASK_COMPLETE,
         'assigned' => self::FILTER_MASK_ASSIGNED,
         'mytasks'  => self::FILTER_MASK_MYTASKS,
     );
 
     public $task = '?(?!login|logout).*';
     public $allowed_prefs = array('tasklist_sort_col','tasklist_sort_order');
 
     public $rc;
     public $lib;
     public $driver;
     public $timezone;
     public $ui;
     public $home;  // declare public to be used in other classes
 
     private $collapsed_tasks = array();
     private $message_tasks = array();
     private $itip;
     private $ical;
 
 
     /**
      * Plugin initialization.
      */
     function init()
     {
         $this->require_plugin('libcalendaring');
         $this->require_plugin('jqueryui');
 
         $this->rc  = rcube::get_instance();
         $this->lib = libcalendaring::get_instance();
 
         $this->register_task('tasks', 'tasklist');
 
         // load plugin configuration
         $this->load_config();
 
         $this->timezone = $this->lib->timezone;
 
         // proceed initialization in startup hook
         $this->add_hook('startup', array($this, 'startup'));
 
         $this->add_hook('user_delete', array($this, 'user_delete'));
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         // the tasks module can be enabled/disabled by the kolab_auth plugin
         if ($this->rc->config->get('tasklist_disabled', false) || !$this->rc->config->get('tasklist_enabled', true))
             return;
 
         // load localizations
         $this->add_texts('localization/', $args['task'] == 'tasks' && (!$args['action'] || $args['action'] == 'print'));
         $this->rc->load_language($_SESSION['language'], array('tasks.tasks' => $this->gettext('navtitle')));  // add label for task title
 
         if ($args['task'] == 'tasks' && $args['action'] != 'save-pref') {
             $this->load_driver();
 
             // register calendar actions
             $this->register_action('index', array($this, 'tasklist_view'));
             $this->register_action('task', array($this, 'task_action'));
             $this->register_action('tasklist', array($this, 'tasklist_action'));
             $this->register_action('counts', array($this, 'fetch_counts'));
             $this->register_action('fetch', array($this, 'fetch_tasks'));
             $this->register_action('print', array($this, 'print_tasks'));
             $this->register_action('inlineui', array($this, 'get_inline_ui'));
             $this->register_action('mail2task', array($this, 'mail_message2task'));
             $this->register_action('get-attachment', array($this, 'attachment_get'));
             $this->register_action('upload', array($this, 'attachment_upload'));
             $this->register_action('mailimportitip', array($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') {
                 $this->api->add_content(html::tag('li', null, 
                     $this->api->output->button(array(
                         'command'  => 'tasklist-create-from-mail',
                         'label'    => 'tasklist.createfrommail',
                         'type'     => 'link',
                         'classact' => 'icon taskaddlink active',
                         'class'    => 'icon taskaddlink',
                         'innerclass' => 'icon taskadd',
                     ))),
                 'messagemenu');
 
                 $this->api->output->add_label('tasklist.createfrommail');
             }
         }
 
         if (!$this->rc->output->ajax_call && !$this->rc->output->env['framed']) {
             $this->load_ui();
             $this->ui->init();
         }
 
         // add hooks for alarms handling
         $this->add_hook('pending_alarms', array($this, 'pending_alarms'));
         $this->add_hook('dismiss_alarms', array($this, 'dismiss_alarms'));
     }
 
     /**
      *
      */
     private function load_ui()
     {
         if (!$this->ui) {
             require_once($this->home . '/tasklist_ui.php');
             $this->ui = new tasklist_ui($this);
         }
     }
 
     /**
      * Helper method to load the backend driver according to local config
      */
     private function load_driver()
     {
         if (is_object($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');
 
         switch ($driver_name) {
         case "kolab":
             $this->require_plugin('libkolab');
         default:
             $this->driver = new $driver_class($this);
             break;
         }
 
         $this->rc->output->set_env('tasklist_driver', $driver_name);
     }
 
 
     /**
      * Dispatcher for task-related actions initiated by the client
      */
     public function task_action()
     {
         $filter = intval(rcube_utils::get_input_value('filter', rcube_utils::INPUT_GPC));
         $action = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $rec    = rcube_utils::get_input_value('t', rcube_utils::INPUT_POST, true);
         $oldrec = $rec;
         $success = $refresh = $got_msg = false;
 
         // force notify if hidden + active
         $itip_send_option = (int)$this->rc->config->get('calendar_itip_send_option', 3);
         if ($itip_send_option === 1 && empty($rec['_reportpartstat']))
             $rec['_notify'] = 1;
 
         switch ($action) {
         case 'new':
             $oldrec = null;
             $rec = $this->prepare_task($rec);
             $rec['uid'] = $this->generate_uid();
             $temp_id = $rec['tempid'];
             if ($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'])) {
                     $refresh[] = $this->driver->get_task(array('id' => $oldrec['parent_id'], 'list' => $rec['list']));
                 }
             }
 
             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 && $rec['_notify'] && ($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)
                     $this->rc->output->show_message('tasklist.errornotifying', 'error');
             }
         }
         else if ($success && $rec['_reportpartstat'] && $rec['_reportpartstat'] != 'NEEDS-ACTION') {
             // get the full record after update
             $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');
 
         if ($refresh) {
             if ($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 (!$this->itip) {
             require_once realpath(__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($rec)
     {
         // try to be smart and extract date from raw input
         if ($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 ($rec['valarms']) {
             $valarms = array();
             foreach (libcalendaring::from_client_alarms($rec['valarms']) as $alarm) {
                 // alarms can only work with a date (either task start, due or absolute alarm date)
                 if (is_a($alarm['trigger'], 'DateTime') || $rec['date'] || $rec['startdate'])
                     $valarms[] = $alarm;
             }
             $rec['valarms'] = $valarms;
         }
 
         // convert the submitted recurrence settings
         if (is_array($rec['recurrence'])) {
             $refdate = null;
             if (!empty($rec['date'])) {
                 $refdate = new DateTime($rec['date'] . ' ' . $rec['time'], $this->timezone);
             }
             else if (!empty($rec['startdate'])) {
                 $refdate = new DateTime($rec['startdate'] . ' ' . $rec['starttime'], $this->timezone);
             }
 
             if ($refdate) {
                 $rec['recurrence'] = $this->lib->from_client_recurrence($rec['recurrence'], $refdate);
 
                 // translate count into an absolute end date.
                 // why? because when shifting completed tasks to the next recurrence,
                 // the initial start date to count from gets lost.
                 if ($rec['recurrence']['COUNT']) {
                     $engine = libcalendaring::get_recurrence();
                     $engine->init($rec['recurrence'], $refdate);
                     if ($until = $engine->end()) {
                         $rec['recurrence']['UNTIL'] = $until;
                         unset($rec['recurrence']['COUNT']);
                     }
                 }
             }
             else {  // recurrence requires a reference date
                 $rec['recurrence'] = '';
             }
         }
 
         $attachments = array();
         $taskid = $rec['id'];
         if (is_array($_SESSION[self::SESSION_KEY]) && $_SESSION[self::SESSION_KEY]['id'] == $taskid) {
             if (!empty($_SESSION[self::SESSION_KEY]['attachments'])) {
                 foreach ($_SESSION[self::SESSION_KEY]['attachments'] as $id => $attachment) {
                     if (is_array($rec['attachments']) && in_array($id, $rec['attachments'])) {
                         $attachments[$id] = $this->rc->plugins->exec_hook('attachment_get', $attachment);
                         unset($attachments[$id]['abort'], $attachments[$id]['group']);
                     }
                 }
             }
         }
 
         $rec['attachments'] = $attachments;
 
         // convert link references into simple URIs
         if (array_key_exists('links', $rec)) {
             $rec['links'] = array_map(function($link) { return is_array($link) ? $link['uri'] : strval($link); }, (array)$rec['links']);
         }
 
         // convert invalid data
         if (isset($rec['attendees']) && !is_array($rec['attendees']))
             $rec['attendees'] = array();
 
         foreach ((array)$rec['attendees'] as $i => $attendee) {
             if (is_string($attendee['rsvp'])) {
                 $rec['attendees'][$i]['rsvp'] = $attendee['rsvp'] == 'true' || $attendee['rsvp'] == '1';
             }
         }
 
         // copy the task status to my attendee partstat
         if (!empty($rec['_reportpartstat'])) {
             if (($idx = $this->is_attendee($rec)) !== false) {
                 if (!($rec['_reportpartstat'] == 'NEEDS-ACTION' && $rec['attendees'][$idx]['status'] == 'ACCEPTED'))
                     $rec['attendees'][$idx]['status'] = $rec['_reportpartstat'];
                 else
                     unset($rec['_reportpartstat']);
             }
         }
 
         // set organizer from identity selector
         if ((isset($rec['_identity']) || (!empty($rec['attendees']) && empty($rec['organizer']))) &&
                 ($identity = $this->rc->user->get_identity($rec['_identity']))) {
             $rec['organizer'] = array('name' => $identity['name'], 'email' => $identity['email']);
         }
 
         if (is_numeric($rec['id']) && $rec['id'] < 0)
             unset($rec['id']);
 
         return $rec;
     }
 
     /**
      * Utility method to convert a tasks date/time values into a normalized format
      */
     private function normalize_dates(&$rec, $date_key, $time_key)
     {
         try {
             // parse date from user format (#2801)
             $date_format = $this->rc->config->get(empty($rec[$time_key]) ? 'date_format' : 'date_long', 'Y-m-d');
             $date = DateTime::createFromFormat($date_format, trim($rec[$date_key] . ' ' . $rec[$time_key]), $this->timezone);
 
             // fall back to default strtotime logic
             if (empty($date)) {
                 $date = new DateTime($rec[$date_key] . ' ' . $rec[$time_key], $this->timezone);
             }
 
             $rec[$date_key] = $date->format('Y-m-d');
             if (!empty($rec[$time_key]))
                 $rec[$time_key] = $date->format('H:i');
 
             return true;
         }
         catch (Exception $e) {
             $rec[$date_key] = $rec[$time_key] = null;
         }
 
         return false;
     }
 
     /**
      * Releases some resources after successful save
      */
     private function cleanup_task(&$rec)
     {
         // remove temp. attachment files
         if (!empty($_SESSION[self::SESSION_KEY]) && ($taskid = $_SESSION[self::SESSION_KEY]['id'])) {
             $this->rc->plugins->exec_hook('attachments_cleanup', array('group' => $taskid));
             $this->rc->session->remove(self::SESSION_KEY);
         }
     }
 
     /**
      * When flagging a recurring task as complete,
      * clone it and shift dates to the next occurrence
      */
     private function handle_recurrence(&$rec, $old)
     {
         $clone = null;
         if ($this->driver->is_complete($rec) && $old && !$this->driver->is_complete($old) && is_array($rec['recurrence'])) {
             $engine = libcalendaring::get_recurrence();
             $rrule = $rec['recurrence'];
             $updates = array();
 
             // compute the next occurrence of date attributes
             foreach (array('date'=>'time', 'startdate'=>'starttime') as $date_key => $time_key) {
                 if (empty($rec[$date_key]))
                     continue;
 
                 $date = new DateTime($rec[$date_key] . ' ' . $rec[$time_key], $this->timezone);
                 $engine->init($rrule, $date);
                 if ($next = $engine->next()) {
                     $updates[$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()) {
                             $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;
 
         if (isset($list['showalarms']))
           $list['showalarms'] = intval($list['showalarms']);
 
         switch ($action) {
         case 'form-new':
         case 'form-edit':
             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'] = $insert_id;
                 if (!$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[] = $prop;
             }
             // report more results available
             if ($this->driver->search_more_results) {
                 $this->rc->output->show_message('autocompletemore', 'info');
             }
 
             $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 $list) {
                 if ($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()
     {
         $f = 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' => $f, 'search' => $search);
 /*
         // convert magic date filters into a real date range
         switch ($f) {
         case self::FILTER_MASK_TODAY:
             $today = new DateTime('now', $this->timezone);
             $filter['from'] = $filter['to'] = $today->format('Y-m-d');
             break;
 
         case self::FILTER_MASK_TOMORROW:
             $tomorrow = new DateTime('now + 1 day', $this->timezone);
             $filter['from'] = $filter['to'] = $tomorrow->format('Y-m-d');
             break;
 
         case self::FILTER_MASK_OVERDUE:
             $yesterday = new DateTime('yesterday', $this->timezone);
             $filter['to'] = $yesterday->format('Y-m-d');
             break;
 
         case self::FILTER_MASK_WEEK:
             $today = new DateTime('now', $this->timezone);
             $filter['from'] = $today->format('Y-m-d');
             $weekend = new DateTime('now + 7 days', $this->timezone);
             $filter['to'] = $weekend->format('Y-m-d');
             break;
 
         case self::FILTER_MASK_LATER:
             $date = new DateTime('now + 8 days', $this->timezone);
             $filter['from'] = $date->format('Y-m-d');
             break;
 
         }
 */
         $data = $this->tasks_data($this->driver->list_tasks($filter, $lists), $f);
         $this->rc->output->command('plugin.data_ready', array(
             'filter' => $f,
             '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)
     {
         $f      = 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' => $f, 'search' => $search);
 
         $data = $this->tasks_data($this->driver->list_tasks($filter, $lists), $f);
 
         // we'll build the tasks table in javascript on page load
         // where we have sorting methods, etc.
         $this->rc->output->set_env('tasks', $data);
 
         return $this->ui->tasks_resultview($attrib);
     }
 
     /**
      * Prepare and sort the given task records to be sent to the client
      */
     private function tasks_data($records, $f)
     {
         $data = $this->task_tree = $this->task_titles = array();
 
         foreach ($records as $rec) {
             if ($rec['parent_id']) {
                 $this->task_tree[$rec['id']] = $rec['parent_id'];
             }
 
             $this->encode_task($rec);
 
             // apply filter; don't trust the driver on this :-)
             if ((!$f && !$this->driver->is_complete($rec)) || ($rec['mask'] & $f))
                 $data[] = $rec;
         }
 
         // assign hierarchy level indicators for later sorting
         array_walk($data, array($this, 'task_walk_tree'));
 
         return $data;
     }
 
     /**
      * Prepare the given task record before sending it to the client
      */
     private function encode_task(&$rec)
     {
         $rec['mask'] = $this->filter_mask($rec);
         $rec['flagged'] = intval($rec['flagged']);
         $rec['complete'] = floatval($rec['complete']);
 
         if (is_object($rec['created'])) {
             $rec['created_'] = $this->rc->format_date($rec['created']);
             $rec['created'] = $rec['created']->format('U');
         }
         if (is_object($rec['changed'])) {
             $rec['changed_'] = $this->rc->format_date($rec['changed']);
             $rec['changed'] = $rec['changed']->format('U');
         }
         else {
             $rec['changed'] = null;
         }
 
         if ($rec['date']) {
             try {
                 $date = new DateTime($rec['date'] . ' ' . $rec['time'], $this->timezone);
                 $rec['datetime'] = intval($date->format('U'));
                 $rec['date'] = $date->format($this->rc->config->get('date_format', 'Y-m-d'));
                 $rec['_hasdate'] = 1;
             }
             catch (Exception $e) {
                 $rec['date'] = $rec['datetime'] = null;
             }
         }
         else {
             $rec['date'] = $rec['datetime'] = null;
             $rec['_hasdate'] = 0;
         }
 
         if ($rec['startdate']) {
             try {
                 $date = new DateTime($rec['startdate'] . ' ' . $rec['starttime'], $this->timezone);
                 $rec['startdatetime'] = intval($date->format('U'));
                 $rec['startdate'] = $date->format($this->rc->config->get('date_format', 'Y-m-d'));
             }
             catch (Exception $e) {
                 $rec['startdate'] = $rec['startdatetime'] = null;
             }
         }
 
         if ($rec['valarms']) {
             $rec['alarms_text'] = libcalendaring::alarms_text($rec['valarms']);
             $rec['valarms'] = libcalendaring::to_client_alarms($rec['valarms']);
         }
 
         if ($rec['recurrence']) {
             $rec['recurrence_text'] = $this->lib->recurrence_text($rec['recurrence']);
             $rec['recurrence'] = $this->lib->to_client_recurrence($rec['recurrence'], $rec['time'] || $rec['starttime']);
         }
 
         foreach ((array)$rec['attachments'] as $k => $attachment) {
             $rec['attachments'][$k]['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
         }
 
         // convert link URIs references into structs
         if (array_key_exists('links', $rec)) {
             foreach ((array) $rec['links'] as $i => $link) {
                 if (strpos($link, 'imap://') === 0 && ($msgref = $this->driver->get_message_reference($link, 'task'))) {
                     $rec['links'][$i] = $msgref;
                 }
             }
         }
 
         // Convert HTML description into plain text
         if ($this->is_html($rec)) {
             $h2t = new rcube_html2text($rec['description'], false, true, 0);
             $rec['description'] = $h2t->get_text();
         }
 
         if (!is_array($rec['tags']))
             $rec['tags'] = (array)$rec['tags'];
         sort($rec['tags'], SORT_LOCALE_STRING);
 
         if (in_array($rec['id'], $this->collapsed_tasks))
           $rec['collapsed'] = true;
 
         if (empty($rec['parent_id']))
             $rec['parent_id'] = null;
 
         $this->task_titles[$rec['id']] = $rec['title'];
     }
 
     /**
      * Determine whether the given task description is HTML formatted
      */
     private function is_html($task)
     {
         // check for opening and closing <html> or <body> tags
         return (preg_match('/<(html|body)(\s+[a-z]|>)/', $task['description'], $m) && strpos($task['description'], '</'.$m[1].'>') > 0);
     }
 
     /**
      * Callback function for array_walk over all tasks.
      * Sets tree depth and parent titles
      */
     private function task_walk_tree(&$rec)
     {
         $rec['_depth'] = 0;
         $parent_titles = array();
         $parent_id = $this->task_tree[$rec['id']];
         while ($parent_id) {
             $rec['_depth']++;
             array_unshift($parent_titles, $this->task_titles[$parent_id]);
             $parent_id = $this->task_tree[$parent_id];
         }
 
         if (count($parent_titles)) {
             $rec['parent_title'] = join(' » ', array_filter($parent_titles));
         }
     }
 
     /**
      * Compute the filter mask of the given task
      *
      * @param array Hash array with Task record properties
      * @return int Filter mask
      */
     public function filter_mask($rec)
     {
         static $today, $tomorrow, $weeklimit;
 
         if (!$today) {
             $today_date = new DateTime('now', $this->timezone);
             $today = $today_date->format('Y-m-d');
             $tomorrow_date = new DateTime('now + 1 day', $this->timezone);
             $tomorrow = $tomorrow_date->format('Y-m-d');
             $week_date = new DateTime('now + 7 days', $this->timezone);
             $weeklimit = $week_date->format('Y-m-d');
         }
 
         $mask = 0;
         $start = $rec['startdate'] ?: '1900-00-00';
         $duedate = $rec['date'] ?: '3000-00-00';
 
         if ($rec['flagged'])
             $mask |= self::FILTER_MASK_FLAGGED;
         if ($this->driver->is_complete($rec))
             $mask |= self::FILTER_MASK_COMPLETE;
 
         if (empty($rec['date']))
             $mask |= self::FILTER_MASK_NODATE;
         else if ($rec['date'] < $today)
             $mask |= self::FILTER_MASK_OVERDUE;
 
         if (empty($rec['recurrence']) || $duedate < $today || $start > $weeklimit) {
             if ($duedate <= $today || ($rec['startdate'] && $start <= $today))
                 $mask |= self::FILTER_MASK_TODAY;
             if ($duedate <= $tomorrow || ($rec['startdate'] && $start <= $tomorrow))
                 $mask |= self::FILTER_MASK_TOMORROW;
             if (($start > $tomorrow && $start <= $weeklimit) || ($duedate > $tomorrow && $duedate <= $weeklimit))
                 $mask |= self::FILTER_MASK_WEEK;
             else if ($start > $weeklimit || $duedate > $weeklimit)
                 $mask |= self::FILTER_MASK_LATER;
         }
         else if ($rec['startdate'] || $rec['date']) {
             $date = new DateTime($rec['startdate'] ?: $rec['date'], $this->timezone);
 
             // set safe recurrence start
             while ($date->format('Y-m-d') >= $today) {
                 switch ($rec['recurrence']['FREQ']) {
                     case 'DAILY':
                         $date = clone $today_date;
                         $date->sub(new DateInterval('P1D'));
                         break;
                     case 'WEEKLY': $date->sub(new DateInterval('P7D')); break;
                     case 'MONTHLY': $date->sub(new DateInterval('P1M')); break;
                     case 'YEARLY': $date->sub(new DateInterval('P1Y')); break;
                     default; break 2;
                 }
             }
 
             $date->_dateonly = true;
 
             $engine = libcalendaring::get_recurrence();
             $engine->init($rec['recurrence'], $date);
 
             // check task occurrences (stop next week)
             // FIXME: is there a faster way of doing this?
             while ($date = $engine->next()) {
                 $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', 'libcalendaring.expandattendeegroup', 'libcalendaring.expandattendeegroupnodata');
 
         $this->rc->output->set_pagetitle($this->gettext('navtitle'));
         $this->rc->output->send('tasklist.mainview');
     }
 
 
     /**
      *
      */
     public function get_inline_ui()
     {
         foreach (array('save','cancel','savingdata') as $label)
             $texts['tasklist.'.$label] = $this->gettext($label);
 
         $texts['tasklist.newtask'] = $this->gettext('createfrommail');
 
 
         $this->ui->init_templates();
         $this->ui->tasklists();
 
         // collect env variables
         $env = array(
             'tasklists' => $this->rc->output->get_env('tasklists'),
             'tasklist_settings' => $this->ui->load_settings(),
         );
 
         echo $this->api->output->parse('tasklist.taskedit', false, false);
 
         $script_add = '';
         foreach ($this->ui->get_gui_objects() as $obj => $id) {
             $script_add .= rcmail_output::JS_OBJECT_NAME . ".gui_object('$obj', '$id');\n";
         }
 
         echo html::tag('script', array('type' => 'text/javascript'),
             rcmail_output::JS_OBJECT_NAME . ".set_env(" . json_encode($env) . ");\n".
             rcmail_output::JS_OBJECT_NAME . ".add_label(" . json_encode($texts) . ");\n".
             $script_add
         );
         exit;
     }
 
     /**
      * 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, 255), 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;
     }
 
 
     /******* Attachment handling  *******/
 
     /**
      * Handler for attachments upload
     */
     public function attachment_upload()
     {
         $this->lib->attachment_upload(self::SESSION_KEY);
     }
 
     /**
      * Handler for attachments download/displaying
      */
     public function attachment_get()
     {
         // show loading page
         if (!empty($_GET['_preload'])) {
             return $this->lib->attachment_loading_page();
         }
 
         $task = rcube_utils::get_input_value('_t', rcube_utils::INPUT_GPC);
         $list = rcube_utils::get_input_value('_list', rcube_utils::INPUT_GPC);
         $id   = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
         $rev  = rcube_utils::get_input_value('_rev', rcube_utils::INPUT_GPC);
 
         $task = array('id' => $task, 'list' => $list, 'rev' => $rev);
         $attachment = $this->driver->get_attachment($id, $task);
 
         // show part page
         if (!empty($_GET['_frame'])) {
             $this->lib->attachment = $attachment;
             $this->register_handler('plugin.attachmentframe', array($this->lib, 'attachment_frame'));
             $this->register_handler('plugin.attachmentcontrols', array($this->lib, 'attachment_header'));
             $this->rc->output->send('tasklist.attachment');
         }
         // deliver attachment content
         else if ($attachment) {
             $attachment['body'] = $this->driver->get_attachment_body($id, $task);
             $this->lib->attachment_get($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()
     {
         $uid  = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
         $mbox = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
         $task = array();
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
         $message = new rcube_message($uid);
 
         if ($message->headers) {
             $task['title'] = trim($message->subject);
             $task['description'] = trim($message->first_text_part());
             $task['id'] = -$uid;
 
             $this->load_driver();
 
             // add a reference to the email message
             if ($msgref = $this->driver->get_message_reference($message->headers, $mbox)) {
                 $task['links'] = array($msgref);
             }
             // copy mail attachments to task
             else if ($message->attachments && $this->driver->attachments) {
                 if (!is_array($_SESSION[self::SESSION_KEY]) || $_SESSION[self::SESSION_KEY]['id'] != $task['id']) {
                     $_SESSION[self::SESSION_KEY] = array();
                     $_SESSION[self::SESSION_KEY]['id'] = $task['id'];
                     $_SESSION[self::SESSION_KEY]['attachments'] = array();
                 }
 
                 foreach ((array)$message->attachments as $part) {
                     $attachment = array(
                         'data' => $imap->get_message_part($uid, $part->mime_id, $part),
                         'size' => $part->size,
                         'name' => $part->filename,
                         'mimetype' => $part->mimetype,
                         'group' => $task['id'],
                     );
 
                     $attachment = $this->rc->plugins->exec_hook('attachment_save', $attachment);
 
                     if ($attachment['status'] && !$attachment['abort']) {
                         $id = $attachment['id'];
                         $attachment['classname'] = rcube_utils::file2class($attachment['mimetype'], $attachment['name']);
 
                         // store new attachment in session
                         unset($attachment['status'], $attachment['abort'], $attachment['data']);
                         $_SESSION[self::SESSION_KEY]['attachments'][$id] = $attachment;
 
                         $attachment['id'] = 'rcmfile' . $attachment['id'];  // add prefix to consider it 'new'
                         $task['attachments'][] = $attachment;
                     }
                 }
             }
 
             $this->rc->output->command('plugin.mail2taskdialog', $task);
         }
         else {
             $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
         }
 
         $this->rc->output->send();
     }
 
     /**
      * 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',
                     $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',
                 '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', 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',
                 '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($p)
     {
         if (!$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 (!$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($sensitivity = null)
     {
         $lists = $this->driver->get_lists();
         $list = null;
 
         foreach ($lists as $l) {
             if ($sensitivity && $l['subtype'] == $sensitivity) {
                 $list = $l;
                 break;
             }
             if ($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] ?: $this->get_default_tasklist($task['sensitivity']);
                 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);
         $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;
         $delegate = null;
 
         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 = intval(rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST));
 
                 $itip = $this->load_itip();
                 if ($itip->delegate_to($task, $delegate, $rsvpme ? true : false)) {
                     $this->rc->output->show_message('tasklist.itipsendsuccess', 'confirmation');
                 }
                 else {
                     $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
                 }
             }
 
             // 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();
             $list    = $lists[$list_id];
             $dontsave = ($_REQUEST['_folder'] === '' && $task['_method'] == 'REQUEST');
 
             // select default list except user explicitly selected 'none'
             if (!$list && !$dontsave) {
                 $list = $this->get_default_tasklist($task['sensitivity']);
             }
 
             $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 = $this->driver->get_task($task['uid']);
 
                 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)) {
                             $emails = $this->lib->get_user_emails();
                             foreach ($task['attendees'] as $i => $attendee) {
                                 if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                                     foreach ($existing['attendees'] as $j => $_attendee) {
                                         if ($attendee['email'] == $_attendee['email']) {
                                             $task['attendees'][$i] = $existing['attendees'][$j];
                                             break;
                                         }
                                     }
                                 }
                             }
                         }
 
                         // 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'] = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
             $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();
     }
 
     /**
      * 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 = $this->driver->get_task($data);
         $itip     = $this->load_itip();
         $response = $itip->get_itip_status($data, $existing);
 
         // get a list of writeable lists to save new tasks to
         if (!$existing && $response['action'] == 'rsvp' || $response['action'] == 'import') {
             $lists  = $this->driver->get_lists();
             $select = new html_select(array('name' => 'tasklist', 'id' => 'itip-saveto', 'is_escaped' => true));
             $select->add('--', '');
 
             foreach ($lists as $list) {
                 if ($list['editable']) {
                     $select->add($list['name'], $list['id']);
                 }
             }
         }
 
         if ($select) {
             $default_list = $this->get_default_tasklist($data['sensitivity']);
             $response['select'] = html::span('folder-select', $this->gettext('saveintasklist') . '&nbsp;' .
                 $select->show($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']) {
             $object['priority'] = 1;
         }
         else if (!$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;
     }
 }