diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index ee87251d..f6bacbf2 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -1,3597 +1,3602 @@
 <?php
 
 /**
  * Calendar plugin for Roundcube webmail
  *
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2014-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class calendar extends rcube_plugin
 {
   const FREEBUSY_UNKNOWN = 0;
   const FREEBUSY_FREE = 1;
   const FREEBUSY_BUSY = 2;
   const FREEBUSY_TENTATIVE = 3;
   const FREEBUSY_OOF = 4;
 
   const SESSION_KEY = 'calendar_temp';
 
   public $task = '?(?!logout).*';
   public $rc;
   public $lib;
   public $resources_dir;
   public $home;  // declare public to be used in other classes
   public $urlbase;
   public $timezone;
   public $timezone_offset;
   public $gmt_offset;
   public $ui;
 
   public $defaults = array(
     'calendar_default_view' => "agendaWeek",
     'calendar_timeslots'    => 2,
     'calendar_work_start'   => 6,
     'calendar_work_end'     => 18,
     'calendar_agenda_range' => 60,
+    'calendar_show_weekno'  => 0,
     'calendar_event_coloring'  => 0,
     'calendar_time_indicator'  => true,
     'calendar_allow_invite_shared' => false,
     'calendar_itip_send_option'    => 3,
     'calendar_itip_after_action'   => 0,
   );
 
 // These are implemented with __get()
 //  private $ical;
 //  private $itip;
 //  private $driver;
 
 
   /**
    * Plugin initialization.
    */
   function init()
   {
     $this->rc = rcube::get_instance();
 
     $this->register_task('calendar', 'calendar');
 
     // load calendar configuration
     $this->load_config();
 
     // catch iTIP confirmation requests that don're require a valid session
     if ($this->rc->action == 'attend' && !empty($_REQUEST['_t'])) {
       $this->add_hook('startup', array($this, 'itip_attend_response'));
     }
     else if ($this->rc->action == 'feed' && !empty($_REQUEST['_cal'])) {
       $this->add_hook('startup', array($this, 'ical_feed_export'));
     }
     else if ($this->rc->task != 'login') {
       // default startup routine
       $this->add_hook('startup', array($this, 'startup'));
     }
 
     $this->add_hook('user_delete', array($this, 'user_delete'));
   }
 
   /**
    * Setup basic plugin environment and UI
    */
   protected function setup()
   {
     $this->require_plugin('libcalendaring');
     $this->require_plugin('libkolab');
 
     $this->lib             = libcalendaring::get_instance();
     $this->timezone        = $this->lib->timezone;
     $this->gmt_offset      = $this->lib->gmt_offset;
     $this->dst_active      = $this->lib->dst_active;
     $this->timezone_offset = $this->gmt_offset / 3600 - $this->dst_active;
 
     // load localizations
     $this->add_texts('localization/', $this->rc->task == 'calendar' && (!$this->rc->action || $this->rc->action == 'print'));
 
     require($this->home . '/lib/calendar_ui.php');
     $this->ui = new calendar_ui($this);
   }
 
   /**
    * Startup hook
    */
   public function startup($args)
   {
     // the calendar module can be enabled/disabled by the kolab_auth plugin
     if ($this->rc->config->get('calendar_disabled', false) || !$this->rc->config->get('calendar_enabled', true))
         return;
 
     $this->setup();
 
     // load Calendar user interface
-    if (!$this->rc->output->ajax_call && (!$this->rc->output->env['framed'] || $args['action'] == 'preview')) {
+    if (!$this->rc->output->ajax_call && (empty($this->rc->output->env['framed']) || $args['action'] == 'preview')) {
       $this->ui->init();
 
       // settings are required in (almost) every GUI step
       if ($args['action'] != 'attend')
         $this->rc->output->set_env('calendar_settings', $this->load_settings());
     }
 
     if ($args['task'] == 'calendar' && $args['action'] != 'save-pref') {
       if ($args['action'] != 'upload') {
         $this->load_driver();
       }
 
       // register calendar actions
       $this->register_action('index', array($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'));
       $this->register_action('dialog-ui', array($this, 'mail_message2event'));
       $this->register_action('check-recent', array($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 = $_SESSION['calendar_event_undo']) {
+      if (!empty($_SESSION['calendar_event_undo'])) {
+        $undo = $_SESSION['calendar_event_undo'];
         // ...after timeout
         $undo_time = $this->rc->config->get('undo_timeout', 0);
         if ($undo['ts'] < time() - $undo_time) {
           $this->rc->session->remove('calendar_event_undo');
           // @TODO: do EXPUNGE on kolab objects?
         }
       }
     }
     else if ($args['task'] == 'settings') {
       // add hooks for Calendar settings
       $this->add_hook('preferences_sections_list', array($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' && $_GET['_rel'] != 'event') {
         $this->api->add_content(html::tag('li', array('role' => 'menuitem'),
           $this->api->output->button(array(
             'command'  => 'calendar-create-from-mail',
             'label'    => 'calendar.createfrommail',
             'type'     => 'link',
             'classact' => 'icon calendarlink active',
             'class'    => 'icon calendarlink disabled',
             '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($this->driver))
+    if (!empty($this->driver)) {
       return;
+    }
 
     $driver_name = $this->rc->config->get('calendar_driver', 'database');
     $driver_class = $driver_name . '_driver';
 
     require_once($this->home . '/drivers/calendar_driver.php');
     require_once($this->home . '/drivers/' . $driver_name . '/' . $driver_class . '.php');
 
     $this->driver = new $driver_class($this);
 
-    if ($this->driver->undelete)
+    if ($this->driver->undelete) {
       $this->driver->undelete = $this->rc->config->get('undo_timeout', 0) > 0;
+    }
   }
 
   /**
    * Load iTIP functions
    */
   private function load_itip()
   {
-    if (!$this->itip) {
+    if (empty($this->itip)) {
       require_once($this->home . '/lib/calendar_itip.php');
       $this->itip = new calendar_itip($this);
-      
+
       if ($this->rc->config->get('kolab_invitation_calendars'))
         $this->itip->set_rsvp_actions(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, $calendars = null)
   {
     if ($calendars === null) {
       $calendars = $this->driver->list_calendars(calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_WRITEABLE);
     }
 
     $default_id = $this->rc->config->get('calendar_default_calendar');
     $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 JS files to the page header
     $this->ui->addJS();
 
     $this->ui->init_templates();
     $this->rc->output->add_label('lowest','low','normal','high','highest','delete','cancel','uploading','noemailwarning','close');
 
     // initialize attendees autocompletion
     $this->rc->autocomplete_init();
 
     $this->rc->output->set_env('timezone', $this->timezone->getName());
     $this->rc->output->set_env('calendar_driver', $this->rc->config->get('calendar_driver'), false);
     $this->rc->output->set_env('calendar_resources', (bool)$this->rc->config->get('calendar_resources_driver'));
     $this->rc->output->set_env('identities-selector', $this->ui->identity_select(array(
         'id'         => 'edit-identities-list',
         'aria-label' => $this->gettext('roleorganizer'),
         'class'      => 'form-control custom-select',
     )));
 
     $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
     if (in_array($view, array('agendaWeek', 'agendaDay', 'month', 'list')))
       $this->rc->output->set_env('view', $view);
 
     if ($date = rcube_utils::get_input_value('date', rcube_utils::INPUT_GPC))
       $this->rc->output->set_env('date', $date);
 
     if ($msgref = rcube_utils::get_input_value('itip', rcube_utils::INPUT_GPC))
       $this->rc->output->set_env('itip_events', $this->itip_events($msgref));
 
     $this->rc->output->send("calendar.calendar");
   }
 
   /**
    * Handler for preferences_sections_list hook.
    * Adds Calendar settings sections into preferences sections list.
    *
    * @param array Original parameters
    * @return array Modified parameters
    */
   function preferences_sections_list($p)
   {
     $p['list']['calendar'] = 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';
       $view = $this->rc->config->get('calendar_default_view', $this->defaults['calendar_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'), "list");
       $p['blocks']['view']['options']['default_view'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('default_view'))),
         'content' => $select->show($view == 'table' ? 'list' : $view),
       );
     }
 
     if (!isset($no_override['calendar_timeslots'])) {
       if (!$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';
       $work_start = $this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']);
       $work_end   = $this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']);
       $p['blocks']['view']['options']['workinghours'] = array(
         'title'   => html::label($field_id, rcube::Q($this->gettext('workinghours'))),
         'content' => html::div('input-group',
           $select_hours->show($work_start, array('name' => '_work_start', 'id' => $field_id))
           . html::span('input-group-append input-group-prepend', html::span('input-group-text',' &mdash; '))
           . $select_hours->show($work_end, 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, 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' => html::div('input-group', $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';
       $filter     = calendar_driver::FILTER_PERSONAL | calendar_driver::FILTER_ACTIVE | calendar_driver::FILTER_INSERTABLE;
       $select_cal = new html_select(array('name' => '_default_calendar', 'id' => $field_id, 'is_escaped' => true));
       foreach ((array)$this->driver->list_calendars($filter) as $id => $prop) {
         $select_cal->add($prop['name'], strval($id));
         if ($prop['default'])
           $default_calendar = $id;
       }
       $p['blocks']['view']['options']['defaultcalendar'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('defaultcalendar'))),
         'content' => $select_cal->show($this->rc->config->get('calendar_default_calendar', $default_calendar)),
       );
     }
 
     if (!isset($no_override['calendar_show_weekno'])) {
       if (!$p['current']) {
         $p['blocks']['view']['content'] = true;
         return $p;
       }
 
       $field_id   = 'rcmfd_show_weekno';
       $select = new html_select(array('name' => '_show_weekno', 'id' => $field_id));
       $select->add($this->gettext('weeknonone'), -1);
       $select->add($this->gettext('weeknodatepicker'), 0);
       $select->add($this->gettext('weeknoall'), 1);
 
       $p['blocks']['view']['options']['show_weekno'] = array(
         'title' => html::label($field_id, rcube::Q($this->gettext('showweekno'))),
         'content' => $select->show(intval($this->rc->config->get('calendar_show_weekno'))),
       );
     }
 
     $p['blocks']['itip']['name'] = $this->gettext('itipoptions');
 
     // Invitations handling
     if (!isset($no_override['calendar_itip_after_action'])) {
       if (!$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' => html::div('input-group input-group-combo', $select->show($val) . $folders->show($folder)),
       );
     }
 
     // category definitions
     if (!$this->driver->nocategories && !isset($no_override['calendar_categories'])) {
         $p['blocks']['categories']['name'] = $this->gettext('categories');
 
         if (!$p['current']) {
           $p['blocks']['categories']['content'] = true;
           return $p;
         }
 
         $categories = (array) $this->driver->list_categories();
         $categories_list = '';
         foreach ($categories as $name => $color) {
           $key = md5($name);
           $field_class = 'rcmfd_category_' . str_replace(' ', '_', $name);
           $category_remove = html::span('input-group-append', html::a(array(
               'class'   => 'button icon delete input-group-text',
               'onclick' => '$(this).parent().parent().remove()',
               'title'   => $this->gettext('remove_category'),
               'href'    => '#rcmfd_new_category',
             ), html::span('inner', $this->gettext('delete'))
           ));
           $category_name  = new html_inputfield(array('name' => "_categories[$key]", 'class' => $field_class, 'size' => 30, 'disabled' => $this->driver->categoriesimmutable));
           $category_color = new html_inputfield(array('name' => "_colors[$key]", 'class' => "$field_class colors", 'size' => 6));
           $hidden = $this->driver->categoriesimmutable ? html::tag('input', array('type' => 'hidden', 'name' => "_categories[$key]", 'value' => $name)) : '';
           $categories_list .= $hidden . html::div('input-group', $category_name->show($name) . $category_color->show($color) . $category_remove);
         }
 
         $p['blocks']['categories']['options']['category_' . $name] = 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 = html::span('input-group-append', html::a(array(
             'type'    => 'button',
             'class'   => 'button create input-group-text',
             'title'   => $this->gettext('add_category'),
             'onclick' => 'rcube_calendar_add_category()',
             'href'    => '#rcmfd_new_category',
           ), html::span('inner', $this->gettext('add_category'))
         ));
         $p['blocks']['categories']['options']['categories'] = array(
           'content' => html::div('input-group', $new_category->show('') . $add_category),
         );
 
         $this->rc->output->add_label('delete', 'calendar.remove_category');
         $this->rc->output->add_script('function rcube_calendar_add_category() {
           var name = $("#rcmfd_new_category").val();
           if (name.length) {
             var button_label = rcmail.gettext("calendar.remove_category");
             var input = $("<input>").attr({type: "text", name: "_categories[]", size: 30, "class": "form-control"}).val(name);
             var color = $("<input>").attr({type: "text", name: "_colors[]", size: 6, "class": "colors form-control"}).val("000000");
             var button = $("<a>").attr({"class": "button icon delete input-group-text", title: button_label, href: "#rcmfd_new_category"})
               .click(function() { $(this).parent().parent().remove(); })
               .append($("<span>").addClass("inner").text(rcmail.gettext("delete")));
 
             $("<div>").addClass("input-group").append(input).append(color).append($("<span class=\'input-group-append\'>").append(button))
               .appendTo("#calendarcategories");
             color.minicolors(rcmail.env.minicolors_config || {});
             $("#rcmfd_new_category").val("");
           }
         }', 'foot');
 
         $this->rc->output->add_script('$("#rcmfd_new_category").keypress(function(event) {
           if (event.which == 13) {
             rcube_calendar_add_category();
             event.preventDefault();
           }
         });
         ', 'docready');
 
         // load miniColors js/css files
         jqueryui::miniColors();
     }
 
     // virtual birthdays calendar
     if (!isset($no_override['calendar_contact_birthdays'])) {
       $p['blocks']['birthdays']['name'] = $this->gettext('birthdayscalendar');
 
       if (!$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::tag('li', null, html::label(null, $checkbox->show($active, array('value' => $source['id'])) . rcube::Q($source['realname'] ?: $source['name'])));
       }
 
       $p['blocks']['birthdays']['options']['birthday_adressbooks'] = array(
         'title'   => rcube::Q($this->gettext('birthdayscalendarsources')),
         'content' => html::tag('ul', 'proplist', implode("\n", $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'));
       $preset_type = $this->rc->config->get('calendar_birthdays_alarm_type', '');
 
       $p['blocks']['birthdays']['options']['birthdays_alarmoffset'] = array(
         'title'   => html::label($field_id, rcube::Q($this->gettext('showalarms'))),
         'content' => html::div('input-group', $select_type->show($preset_type) . $input_value->show($preset[0]) . ' ' . $select_offset->show($preset[1])),
       );
     }
 
     return $p;
   }
 
   /**
    * Handler for preferences_save hook.
    * Executed on Calendar settings form submit.
    *
    * @param array Original parameters
    * @return array Modified parameters
    */
   function preferences_save($p)
   {
     if ($p['section'] == 'calendar') {
       $this->load_driver();
 
       // compose default alarm preset value
       $alarm_offset  = rcube_utils::get_input_value('_alarm_offset', rcube_utils::INPUT_POST);
       $alarm_value   = rcube_utils::get_input_value('_alarm_value', rcube_utils::INPUT_POST);
       $default_alarm = $alarm_offset[0] . intval($alarm_value) . $alarm_offset[1];
 
       $birthdays_alarm_offset = rcube_utils::get_input_value('_birthdays_alarm_offset', rcube_utils::INPUT_POST);
       $birthdays_alarm_value  = rcube_utils::get_input_value('_birthdays_alarm_value', rcube_utils::INPUT_POST);
       $birthdays_alarm_value  = $birthdays_alarm_offset[0] . intval($birthdays_alarm_value) . $birthdays_alarm_offset[1];
 
       $p['prefs'] = 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_show_weekno'  => intval(rcube_utils::get_input_value('_show_weekno', rcube_utils::INPUT_POST)),
         'calendar_event_coloring'       => intval(rcube_utils::get_input_value('_event_coloring', rcube_utils::INPUT_POST)),
         'calendar_default_alarm_type'   => rcube_utils::get_input_value('_alarm_type', rcube_utils::INPUT_POST),
         'calendar_default_alarm_offset' => $default_alarm,
         'calendar_default_calendar'     => rcube_utils::get_input_value('_default_calendar', rcube_utils::INPUT_POST),
         'calendar_date_format' => null,  // clear previously saved values
         'calendar_time_format' => null,
         'calendar_contact_birthdays'    => 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 => $name) {
           if (!isset($colors[$key])) {
             continue;
           }
 
           $color = preg_replace('/^#/', '', strval($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', 'notice');
 
         $this->rc->output->command('multi_thread_http_response', $results, rcube_utils::get_input_value('_reqid', rcube_utils::INPUT_GPC));
         return;
     }
 
     if ($success)
       $this->rc->output->show_message('successfullysaved', 'confirmation');
     else {
       $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;
 
     // 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'] = $this->generate_uid();
         if (!$this->write_preprocess($event, $action)) {
           $got_msg = true;
         }
         else if ($success = $this->driver->new_event($event)) {
           $event['id'] = $event['uid'];
           $event['_savemode'] = 'all';
           $this->cleanup_event($event);
           $this->event_save_success($event, null, $action, true);
         }
         $reload = $success && $event['recurrence'] ? 2 : 1;
         break;
         
       case "edit":
         if (!$this->write_preprocess($event, $action)) {
           $got_msg = true;
         }
         else if ($success = $this->driver->edit_event($event)) {
           $this->cleanup_event($event);
           $this->event_save_success($event, $old, $action, $success);
         }
         $reload = $success && ($event['recurrence'] || $event['_savemode'] || $event['_fromcalendar']) ? 2 : 1;
         break;
       
       case "resize":
         if (!$this->write_preprocess($event, $action)) {
           $got_msg = true;
         }
         else if ($success = $this->driver->resize_event($event)) {
           $this->event_save_success($event, $old, $action, $success);
         }
         $reload = $event['_savemode'] ? 2 : 1;
         break;
       
       case "move":
         if (!$this->write_preprocess($event, $action)) {
           $got_msg = true;
         }
         else if ($success = $this->driver->move_event($event)) {
           $this->event_save_success($event, $old, $action, $success);
         }
         $reload = $success && $event['_savemode'] ? 2 : 1;
         break;
       
       case "remove":
         // remove previous deletes
         $undo_time = $this->driver->undelete ? $this->rc->config->get('undo_timeout', 0) : 0;
 
         // search for event if only UID is given
         if (!isset($event['calendar']) && $event['uid']) {
           if (!($event = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE))) {
             break;
           }
           $undo_time = 0;
         }
 
         // Note: the driver is responsible for setting $_SESSION['calendar_event_undo']
         //       containing 'ts' and 'data' elements
         $success = $this->driver->remove_event($event, $undo_time < 1);
         $reload = (!$success || $event['_savemode']) ? 2 : 1;
 
         if ($undo_time > 0 && $success) {
           // 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
         if ($event = $_SESSION['calendar_event_undo']['data'])
           $success = $this->driver->restore_event($event);
 
         if ($success) {
           $this->rc->session->remove('calendar_event_undo');
           $this->rc->output->show_message('calendar.successrestore', 'confirmation');
           $got_msg = true;
           $reload  = 2;
         }
 
         break;
 
       case "rsvp":
         $itip_sending  = $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
         $status        = rcube_utils::get_input_value('status', rcube_utils::INPUT_POST);
         $attendees     = rcube_utils::get_input_value('attendees', rcube_utils::INPUT_POST);
         $reply_comment = $event['comment'];
 
         $this->write_preprocess($event, 'edit');
         $ev = $this->driver->get_event($event);
         $ev['attendees'] = $event['attendees'];
         $ev['free_busy'] = $event['free_busy'];
         $ev['_savemode'] = $event['_savemode'];
         $ev['comment']   = $reply_comment;
 
         // send invitation to delegatee + add it as attendee
         if ($status == 'delegated' && $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['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', $success);
 
     // update event object on the client or trigger a complete refresh if too complicated
     if ($reload && empty($_REQUEST['_framed'])) {
       $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()
   {
     $start  = $this->input_timestamp('start', rcube_utils::INPUT_GET);
     $end    = $this->input_timestamp('end', rcube_utils::INPUT_GET);
     $query  = rcube_utils::get_input_value('q', rcube_utils::INPUT_GET);
     $source = rcube_utils::get_input_value('source', rcube_utils::INPUT_GET);
 
     $events = $this->driver->load_events($start, $end, $query, $source);
     echo $this->encode($events, !empty($query));
     exit;
   }
 
   /**
    * Handler for requests fetching event counts for calendars
    */
   public function count_events()
   {
     // don't update session on these requests (avoiding race conditions)
     $this->rc->session->nowrite = true;
 
     $start = rcube_utils::get_input_value('start', rcube_utils::INPUT_GET);
     if (!$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'])) {
         // Some installations can't handle all occurrences (aborting the request w/o an error in log)
         $end = clone $event['start'];
         $end->add(new DateInterval($event['recurrence']['FREQ'] == 'DAILY' ? 'P1Y' : 'P10Y'));
 
         foreach ($this->driver->get_recurring_events($event, $event['start'], $end) as $recurring) {
           $recurring['temporary'] = true;
           $recurring['readonly']  = true;
           $recurring['calendar']  = '--invitation--itip';
           $events[] = $this->_client_event($recurring, true);
         }
       }
     }
 
     return $events;
   }
 
   /**
    * Handler for keep-alive requests
    * This will check for updated data in active calendars and sync them to the client
    */
   public function refresh($attr)
   {
      // refresh the entire calendar every 10th time to also sync deleted events
     if (rand(0,10) == 10) {
         $this->rc->output->command('plugin.refresh_calendar', 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 ($cal['counts']) {
+      if (!empty($cal['counts'])) {
         $today = new DateTime('today 00:00:00', $this->timezone);
         $counts += $this->driver->count_events($cal['id'], $today->format('U'));
       }
     }
 
     if (!empty($counts)) {
       $this->rc->output->command('plugin.update_counts', 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();
+    $time = !empty($p['time']) ? $p['time'] : time();
     if ($alarms = $this->driver->pending_alarms($time)) {
       foreach ($alarms as $alarm) {
         $alarm['id'] = 'cal:' . $alarm['id'];  // prefix ID with cal:
         $p['alarms'][] = $alarm;
       }
     }
 
     // get alarms for birthdays calendar
     if ($this->rc->config->get('calendar_contact_birthdays') && $this->rc->config->get('calendar_birthdays_alarm_type') == 'DISPLAY') {
       $cache = $this->rc->get_cache('calendar.birthdayalarms', 'db');
 
       foreach ($this->driver->load_birthday_events($time, $time + 86400 * 60) as $e) {
         $alarm = libcalendaring::get_next_alarm($e);
 
         // overwrite alarm time with snooze value (or null if dismissed)
         if ($dismissed = $cache->get($e['id']))
           $alarm['time'] = $dismissed['notifyat'];
 
         // add to list if alarm is set
         if ($alarm && $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->setup();
       $this->load_driver();
       $this->export_events(false);
     }
     else {
       header('HTTP/1.0 404 Not Found');
     }
 
     // don't save session data
     if (!$session_exists)
       session_destroy();
     exit;
   }
 
   /**
    *
    */
   function load_settings()
   {
     $this->lib->load_settings();
     $this->defaults += $this->lib->defaults;
 
     $settings = array();
 
     // configuration
     $settings['default_view']     = (string) $this->rc->config->get('calendar_default_view', $this->defaults['calendar_default_view']);
     $settings['timeslots']        = (int) $this->rc->config->get('calendar_timeslots', $this->defaults['calendar_timeslots']);
     $settings['first_day']        = (int) $this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
     $settings['first_hour']       = (int) $this->rc->config->get('calendar_first_hour', $this->defaults['calendar_first_hour']);
     $settings['work_start']       = (int) $this->rc->config->get('calendar_work_start', $this->defaults['calendar_work_start']);
     $settings['work_end']         = (int) $this->rc->config->get('calendar_work_end', $this->defaults['calendar_work_end']);
     $settings['agenda_range']     = (int) $this->rc->config->get('calendar_agenda_range', $this->defaults['calendar_agenda_range']);
     $settings['event_coloring']   = (int) $this->rc->config->get('calendar_event_coloring', $this->defaults['calendar_event_coloring']);
     $settings['time_indicator']   = (int) $this->rc->config->get('calendar_time_indicator', $this->defaults['calendar_time_indicator']);
     $settings['invite_shared']    = (int) $this->rc->config->get('calendar_allow_invite_shared', $this->defaults['calendar_allow_invite_shared']);
     $settings['itip_notify']      = (int) $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
     $settings['show_weekno']      = (int) $this->rc->config->get('calendar_show_weekno', $this->defaults['calendar_show_weekno']);
     $settings['default_calendar'] = $this->rc->config->get('calendar_default_calendar');
     $settings['invitation_calendars'] = (bool) $this->rc->config->get('kolab_invitation_calendars', false);
 
     // 'table' view has been replaced by 'list' view
     if ($settings['default_view'] == 'table') {
       $settings['default_view'] = 'list';
     }
 
     // get user identity to create default attendee
     if ($this->ui->screen == 'calendar') {
       foreach ($this->rc->user->list_emails() as $rec) {
-        if (!$identity)
+        if (empty($identity)) {
           $identity = $rec;
+        }
         $identity['emails'][] = $rec['email'];
         $settings['identities'][$rec['identity_id']] = $rec['email'];
       }
       $identity['emails'][] = $this->rc->user->get_username();
       $settings['identity'] = array('name' => $identity['name'], 'email' => strtolower($identity['email']), 'emails' => ';' . strtolower(join(';', $identity['emails'])));
     }
 
     // freebusy token authentication URL
     if (($url = $this->rc->config->get('calendar_freebusy_session_auth_url'))
       && ($uniqueid = $this->rc->config->get('kolab_uniqueid'))
     ) {
       if ($url === true) $url = '/freebusy';
       $url = rtrim(rcube_utils::resolve_url($url), '/ ');
       $url .= '/' . urlencode($this->rc->get_user_name());
       $url .= '/' . urlencode($uniqueid);
 
       $settings['freebusy_url'] = $url;
     }
 
     return $settings;
   }
 
   /**
    * Encode events as JSON
    *
    * @param  array  Events as array
    * @param  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, allday => allDay because of the fullcalendar client script
     $event['vurl'] = $event['url'];
     $event['allDay'] = !empty($event['allday']);
     unset($event['url']);
     unset($event['allday']);
 
     $event['className'] = $event['className'] ? explode(' ', $event['className']) : array();
 
     if ($event['allDay']) {
         $event['end'] = $event['end']->add(new DateInterval('P1D'));
     }
 
     if ($_GET['mode'] == 'print') {
         $event['editable'] = false;
     }
 
     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']),
     ) + $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()
   {
     $handler = new kolab_attachments_handler();
     $handler->attachment_upload(self::SESSION_KEY, 'cal-');
   }
 
   /**
    * Handler for attachments download/displaying
    */
   public function attachment_get()
   {
     $handler = new kolab_attachments_handler();
 
     // show loading page
     if (!empty($_GET['_preload'])) {
         return $handler->attachment_loading_page();
     }
 
     $event_id = rcube_utils::get_input_value('_event', rcube_utils::INPUT_GPC);
     $calendar = rcube_utils::get_input_value('_cal', rcube_utils::INPUT_GPC);
     $id       = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
     $rev      = rcube_utils::get_input_value('_rev', rcube_utils::INPUT_GPC);
 
     $event = 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'])) {
         $handler->attachment_page($attachment);
     }
     // deliver attachment content
     else if ($attachment) {
         if ($calendar != '--invitation--itip') {
             $attachment['body'] = $this->driver->get_attachment_body($id, $event);
         }
 
         $handler->attachment_get($attachment);
     }
 
     // if we arrive here, the requested part was not found
     header('HTTP/1.1 404 Not Found');
     exit;
   }
 
   /**
    * Determine whether the given event description is HTML formatted
    */
   private function is_html($event)
   {
       // check for opening and closing <html> or <body> tags
       return (preg_match('/<(html|body)(\s+[a-z]|>)/', $event['description'], $m) && strpos($event['description'], '</'.$m[1].'>') > 0);
   }
 
   /**
    * Prepares new/edited event properties before save
    */
   private function write_preprocess(&$event, $action)
   {
     // Remove double timezone specification (T2313)
     $event['start'] = preg_replace('/\s*\(.*\)/', '', $event['start']);
     $event['end']   = preg_replace('/\s*\(.*\)/', '', $event['end']);
 
     // convert dates into DateTime objects in user's current timezone
     $event['start']  = new DateTime($event['start'], $this->timezone);
     $event['end']    = new DateTime($event['end'], $this->timezone);
     $event['allday'] = !empty($event['allDay']);
     unset($event['allDay']);
 
     // start/end is all we need for 'move' action (#1480)
     if ($action == 'move') {
       return true;
     }
 
     // convert the submitted recurrence settings
     if (is_array($event['recurrence'])) {
       $event['recurrence'] = $this->lib->from_client_recurrence($event['recurrence'], $event['start']);
 
       // align start date with the first occurrence
       if (!empty($event['recurrence']) && !empty($event['syncstart'])
         && (empty($event['_savemode']) || $event['_savemode'] == 'all')
       ) {
         $next = $this->find_first_occurrence($event);
 
         if (!$next) {
           $this->rc->output->show_message('calendar.recurrenceerror', 'error');
           return false;
         }
         else if ($event['start'] != $next) {
           $diff = $event['start']->diff($event['end'], true);
 
           $event['start'] = $next;
           $event['end']   = clone $next;
           $event['end']->add($diff);
         }
       }
     }
 
     // convert the submitted alarm values
     if ($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';
       }
 
       if (!empty($event['_identity'])) {
         $identity = $this->rc->user->get_identity($event['_identity']);
       }
 
       // set new organizer identity
       if ($organizer !== false && $identity) {
         $event['attendees'][$organizer]['name'] = $identity['name'];
         $event['attendees'][$organizer]['email'] = $identity['email'];
       }
       // set owner as organizer if yet missing
       else if ($organizer === false && $owner !== false) {
         $event['attendees'][$owner]['role'] = 'ORGANIZER';
         unset($event['attendees'][$owner]['rsvp']);
       }
       // fallback to the selected identity
       else if ($organizer === false && $identity) {
         $event['attendees'][] = array(
           'role'  => 'ORGANIZER',
           'name'  => $identity['name'],
           'email' => $identity['email'],
         );
       }
     }
 
     // mapping url => vurl because of the fullcalendar client script
     if (array_key_exists('vurl', $event)) {
       $event['url'] = $event['vurl'];
       unset($event['vurl']);
     }
 
     return true;
   }
 
   /**
    * Releases some resources after successful event save
    */
   private function cleanup_event(&$event)
   {
     // remove temp. attachment files
     if (!empty($_SESSION[self::SESSION_KEY]) && ($eventid = $_SESSION[self::SESSION_KEY]['id'])) {
       $this->rc->plugins->exec_hook('attachments_cleanup', 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 = $this->input_timestamp('start', rcube_utils::INPUT_GPC);
     $end   = $this->input_timestamp('end', rcube_utils::INPUT_GPC);
 
     if (!$start) $start = time();
     if (!$end) $end = $start + 3600;
 
     $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 = $this->input_timestamp('start', rcube_utils::INPUT_GPC);
     $end   = $this->input_timestamp('end', rcube_utils::INPUT_GPC);
     $interval  = intval(rcube_utils::get_input_value('interval', rcube_utils::INPUT_GPC));
     $strformat = $interval > 60 ? 'Ymd' : 'YmdHis';
 
     if (!$start) $start = time();
     if (!$end)   $end = $start + 86400 * 30;
     if (!$interval) $interval = 60;  // 1 hour
 
     if (!$dte) {
       $dts = new DateTime('@'.$start);
       $dts->setTimezone($this->timezone);
     }
 
     $fblist = $this->driver->get_freebusy_list($email, $start, $end);
     $slots  = '';
 
     // prepare freebusy list before use (for better performance)
     if (is_array($fblist)) {
       foreach ($fblist as $idx => $slot) {
         list($from, $to, ) = $slot;
 
         // check for possible all-day times
         if (gmdate('His', $from) == '000000' && gmdate('His', $to) == '235959') {
           // shift into the user's timezone for sane matching
           $fblist[$idx][0] -= $this->gmt_offset;
           $fblist[$idx][1] -= $this->gmt_offset;
         }
       }
     }
 
     // build a list from $start till $end with blocks representing the fb-status
     for ($s = 0, $t = $start; $t <= $end; $s++) {
       $t_end = $t + $interval * 60;
       $dt = new DateTime('@'.$t);
       $dt->setTimezone($this->timezone);
 
       // determine attendee's status
       if (is_array($fblist)) {
         $status = self::FREEBUSY_FREE;
 
         foreach ($fblist as $slot) {
           list($from, $to, $type) = $slot;
 
           if ($from < $t_end && $to > $t) {
             $status = isset($type) ? $type : self::FREEBUSY_BUSY;
             if ($status == self::FREEBUSY_BUSY)  // can't get any worse :-)
               break;
           }
         }
       }
       else {
         $status = self::FREEBUSY_UNKNOWN;
       }
 
       // use most compact format, assume $status is one digit/character
       $slots .= $status;
       $t = $t_end;
     }
 
     $dte = new DateTime('@'.$t_end);
     $dte->setTimezone($this->timezone);
 
     // let this information be cached for 5min
     $this->rc->output->future_expire_header(300);
 
     echo rcube_output::json_serialize(array(
       'email' => $email,
       'start' => $dts->format('c'),
       'end'   => $dte->format('c'),
       'interval' => $interval,
       'slots' => $slots,
     ));
     exit;
   }
 
   /**
    * Handler for printing calendars
    */
   public function print_view()
   {
     $title = $this->gettext('print');
 
     $view = rcube_utils::get_input_value('view', rcube_utils::INPUT_GPC);
     if (!in_array($view, array('agendaWeek', 'agendaDay', 'month', 'list')))
       $view = 'agendaDay';
 
     $this->rc->output->set_env('view', $view);
 
     if ($date = rcube_utils::get_input_value('date', rcube_utils::INPUT_GPC))
       $this->rc->output->set_env('date', $date);
 
     if ($range = rcube_utils::get_input_value('range', rcube_utils::INPUT_GPC))
       $this->rc->output->set_env('listRange', intval($range));
 
     if ($search = rcube_utils::get_input_value('search', rcube_utils::INPUT_GPC)) {
       $this->rc->output->set_env('search', $search);
       $title .= ' "' . $search . '"';
     }
 
     // Add JS to the page
     $this->ui->addJS();
 
     $this->register_handler('plugin.calendar_css', array($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');
   }
 
   /**
    * 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((array) $a['attachments']) != count((array) $b['attachments'])) {
       $diff[] = 'attachments';
     }
 
     return $diff;
   }
 
   /**
    * Update attendee properties on the given event object
    *
    * @param array The event object to be altered
    * @param array List of hash arrays each represeting an updated/added attendee
    */
   public static function merge_attendee_data(&$event, $attendees, $removed = null)
   {
     if (!empty($attendees) && !is_array($attendees[0])) {
       $attendees = array($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()) {
       $id    = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
       $start = $this->input_timestamp('start', rcube_utils::INPUT_GET);
       $end   = $this->input_timestamp('end', rcube_utils::INPUT_GET);
 
       $events = $directory->get_resource_calendar($id, $start, $end);
     }
 
     echo $this->encode($events);
     exit;
   }
 
 
   /****  Event invitation plugin hooks ****/
 
   /**
    * Find an event in user calendars
    */
   protected function find_event($event, &$mode)
   {
     $this->load_driver();
 
     // We search for writeable calendars in personal namespace by default
     $mode   = calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL;
     $result = $this->driver->get_event($event, $mode);
     // ... now check shared folders if not found
     if (!$result) {
       $result = $this->driver->get_event($event, calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_SHARED);
       if ($result) {
         $mode |= calendar_driver::FILTER_SHARED;
       }
     }
 
     return $result;
   }
 
   /**
    * Handler for calendar/itip-status requests
    */
   function event_itip_status()
   {
     $data = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
     $this->load_driver();
 
     // find local copy of the referenced event (in personal namespace)
     $existing  = $this->find_event($data, $mode);
     $is_shared = $mode & calendar_driver::FILTER_SHARED;
     $itip      = $this->load_itip();
     $response  = $itip->get_itip_status($data, $existing);
 
     // get a list of writeable calendars to save new events to
     if ((!$existing || $is_shared)
       && !$data['nosave']
       && ($response['action'] == 'rsvp' || $response['action'] == 'import')
     ) {
       $calendars       = $this->driver->list_calendars($mode);
       $calendar_select = new html_select(array(
           'name'       => 'calendar',
           'id'         => 'itip-saveto',
           'is_escaped' => true,
           'class'      => 'form-control custom-select'
       ));
       $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'], $calendars);
       $response['select'] = html::span('folder-select', $this->gettext('saveincalendar') . '&nbsp;' .
         $calendar_select->show($is_shared ? $existing['calendar'] : $default_calendar['id']));
     }
     else if ($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
             || $event['status'] == 'CANCELLED'
             || (!empty($event['className']) && strpos($event['className'], 'declined') !== false)
         ) {
           continue;
         }
 
         if ($event['start'] < $event_start)
           $before[] = $this->mail_agenda_event_row($event);
         else
           $after[] = $this->mail_agenda_event_row($event);
       }
 
       $response['append'] = array(
         'selector' => '.calendar-agenda-preview',
         'replacements' => array(
           '%before%' => !empty($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);
     $listmode = calendar_driver::FILTER_WRITEABLE | calendar_driver::FILTER_PERSONAL;
 
     // search for event if only UID is given
     if ($event = $this->driver->get_event(array('uid' => $uid, '_instance' => $instance), $listmode)) {
       $event['_savemode'] = $savemode;
       $success = $this->driver->remove_event($event, true);
     }
 
     if ($success) {
       $this->rc->output->show_message('calendar.successremoval', 'confirmation');
     }
     else {
       $this->rc->output->show_message('calendar.errorsaving', 'error');
     }
   }
 
   /**
    * Handler for URLs that allow an invitee to respond on his invitation mail
    */
   public function itip_attend_response($p)
   {
     $this->setup();
 
     if ($p['action'] == 'attend') {
       $this->ui->init();
 
       $this->rc->output->set_env('task', 'calendar');  // override some env vars
       $this->rc->output->set_env('refresh_interval', 0);
       $this->rc->output->set_pagetitle($this->gettext('calendar'));
 
       $itip  = $this->load_itip();
       $token = rcube_utils::get_input_value('_t', rcube_utils::INPUT_GPC);
 
       // read event info stored under the given token
       if ($invitation = $itip->get_invitation($token)) {
         $this->token = $token;
         $this->event = $invitation['event'];
 
         // show message about cancellation
         if ($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...
           // FIXME: we should really consider removing this functionality
           //        it's confusing that it creates/updates an event only for logged-in user
           //        what if the logged-in user is not the same as the attendee?
           if ($this->rc->user->ID) {
             $this->load_driver();
 
             $invitation = $itip->get_invitation($token);
             $existing   = $this->driver->get_event($this->event);
 
             // save the event to his/her default calendar if not yet present
             if (!$existing && ($calendar = $this->get_default_calendar($invitation['event']['sensitivity']))) {
               $invitation['event']['calendar'] = $calendar['id'];
               if ($this->driver->new_event($invitation['event']))
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'importedsuccessfully', 'vars' => array('calendar' => $calendar['name']))), 'confirmation');
               else
                 $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
             }
             else if ($existing
               && ($this->event['sequence'] >= $existing['sequence'] || $this->event['changed'] >= $existing['changed'])
               && ($calendar = $this->driver->get_calendar($existing['calendar']))
             ) {
               $this->event       = $invitation['event'];
               $this->event['id'] = $existing['id'];
 
               unset($this->event['comment']);
 
               // merge attendees status
               // e.g. preserve my participant status for regular updates
               $this->lib->merge_attendees($this->event, $existing, $status);
 
               // update attachments list
               $event['deleted_attachments'] = true;
 
               // show me as free when declined (#1670)
               if ($status == 'declined')
                 $this->event['free_busy'] = 'free';
 
               if ($this->driver->edit_event($this->event))
                 $this->rc->output->command('display_message', $this->gettext(array('name' => 'updatedsuccessfully', 'vars' => array('calendar' => $calendar->get_name()))), 'confirmation');
               else
                 $this->rc->output->command('display_message', $this->gettext('errorimportingevent'), 'error');
             }
           }
         }
         
         $this->register_handler('plugin.event_inviteform', array($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 ?: $event['className'])),
       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   = '';
         $date_str = $this->rc->format_date($event['start'], $this->rc->config->get('date_format'), empty($event['start']->_dateonly));
         $date     = new DateTime($event['start']->format('Y-m-d') . ' 12:00:00', new DateTimeZone('UTC'));
 
         // prepare a small agenda preview to be filled with actual event data on async request
         if ($ical_objects->method == 'REQUEST') {
           $append = html::div('calendar-agenda-preview',
             html::tag('h3', 'preview-title', $this->gettext('agenda') . ' ' . html::span('date', $date_str))
             . '%before%' . $this->mail_agenda_event_row($event, 'current') . '%after%');
         }
 
         $html .= html::div('calendar-invitebox invitebox boxinformation',
           $this->itip->mail_itip_inline_ui(
             $event,
             $ical_objects->method,
             $ical_objects->mime_id . ':' . $idx,
             'calendar',
             rcube_utils::anytodatetime($ical_objects->message_date),
             $this->rc->url(array('task' => 'calendar')) . '&view=agendaDay&date=' . $date->format('U')
           ) . $append
         );
       }
 
       // limit listing
       if ($idx >= 3)
         break;
     }
 
     // prepend event boxes to message body
     if ($html) {
       $this->ui->init();
       $p['content'] = $html . $p['content'];
       $this->rc->output->add_label('calendar.savingdata','calendar.deleteventconfirm','calendar.declinedeleteconfirm');
     }
 
     // add "Save to calendar" button into attachment menu
     if ($has_events) {
       $this->add_button(array(
         'id'         => 'attachmentsavecal',
         'name'       => 'attachmentsavecal',
         'type'       => 'link',
         'wrapper'    => 'li',
         'command'    => 'attachment-save-calendar',
         'class'      => 'icon calendarlink disabled',
         'classact'   => 'icon calendarlink active',
         'innerclass' => 'icon calendar',
         'label'      => 'calendar.savetocalendar',
         ), 'attachmentmenu');
     }
 
     return $p;
   }
 
 
   /**
    * Handler for POST request to import an event attached to a mail message
    */
   public function mail_import_itip()
   {
     $itip_sending = $this->rc->config->get('calendar_itip_send_option', $this->defaults['calendar_itip_send_option']);
 
     $uid     = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST);
     $mbox    = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_POST);
     $mime_id = rcube_utils::get_input_value('_part', rcube_utils::INPUT_POST);
     $status  = rcube_utils::get_input_value('_status', rcube_utils::INPUT_POST);
     $delete  = intval(rcube_utils::get_input_value('_del', rcube_utils::INPUT_POST));
     $noreply = intval(rcube_utils::get_input_value('_noreply', rcube_utils::INPUT_POST));
     $noreply = $noreply || $status == 'needs-action' || $itip_sending === 0;
     $instance = rcube_utils::get_input_value('_instance', rcube_utils::INPUT_POST);
     $savemode = rcube_utils::get_input_value('_savemode', rcube_utils::INPUT_POST);
     $comment  = rcube_utils::get_input_value('_comment', rcube_utils::INPUT_POST);
 
     $error_msg = $this->gettext('errorimportingevent');
     $success   = false;
 
     if ($status == 'delegated') {
       $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->rc->gettext('libcalendaring.delegateinvalidaddress'), 'error');
         return;
       }
     }
 
     // successfully parsed events?
     if ($event = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event')) {
       // forward iTip request to delegatee
       if ($delegate) {
         $rsvpme = rcube_utils::get_input_value('_rsvp', rcube_utils::INPUT_POST);
         $itip   = $this->load_itip();
 
         $event['comment'] = $comment;
 
         if ($itip->delegate_to($event, $delegate, !empty($rsvpme))) {
           $this->rc->output->show_message('calendar.itipsendsuccess', 'confirmation');
         }
         else {
           $this->rc->output->command('display_message', $this->gettext('itipresponseerror'), 'error');
         }
 
         unset($event['comment']);
 
         // the delegator is set to non-participant, thus save as non-blocking
         $event['free_busy'] = 'free';
       }
 
       $mode = calendar_driver::FILTER_PERSONAL
         | calendar_driver::FILTER_SHARED
         | calendar_driver::FILTER_WRITEABLE;
 
       // find writeable calendar to store event
       $cal_id    = rcube_utils::get_input_value('_folder', rcube_utils::INPUT_POST);
       $dontsave  = $cal_id === '' && $event['_method'] == 'REQUEST';
       $calendars = $this->driver->list_calendars($mode);
       $calendar  = $calendars[$cal_id];
 
       // select default calendar except user explicitly selected 'none'
       if (!$calendar && !$dontsave)
          $calendar = $this->get_default_calendar($event['sensitivity'], $calendars);
 
       $metadata = 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 = $this->find_event($event, $mode);
 
         // we'll create a new copy if user decided to change the calendar
         if ($existing && $cal_id && $calendar && $calendar['id'] != $existing['calendar']) {
           $existing = null;
         }
 
         if ($existing) {
           $calendar = $calendars[$existing['calendar']];
 
           // forward savemode for correct updates of recurring events
           $existing['_savemode'] = $savemode ?: $event['_savemode'];
 
           // only update attendee status
           if ($event['_method'] == 'REPLY') {
             // try to identify the attendee using the email sender address
             $existing_attendee        = -1;
             $existing_attendee_emails = array();
 
             foreach ($existing['attendees'] as $i => $attendee) {
               $existing_attendee_emails[] = $attendee['email'];
               if ($this->itip->compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                 $existing_attendee = $i;
               }
             }
 
             $event_attendee   = null;
             $update_attendees = array();
 
             foreach ($event['attendees'] as $attendee) {
               if ($this->itip->compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                 $event_attendee       = $attendee;
                 $update_attendees[]   = $attendee;
                 $metadata['fallback'] = $attendee['status'];
                 $metadata['attendee'] = $attendee['email'];
                 $metadata['rsvp']     = $attendee['rsvp'] || $attendee['role'] != 'NON-PARTICIPANT';
 
                 if ($attendee['status'] != 'DELEGATED') {
                   break;
                 }
               }
               // also copy delegate attendee
               else if (!empty($attendee['delegated-from'])
                 && $this->itip->compare_email($attendee['delegated-from'], $event['_sender'], $event['_sender_utf'])
               ) {
                 $update_attendees[] = $attendee;
                 if (!in_array_nocase($attendee['email'], $existing_attendee_emails)) {
                   $existing['attendees'][] = $attendee;
                 }
               }
             }
 
             // if delegatee has declined, set delegator's RSVP=True
             if ($event_attendee && $event_attendee['status'] == 'DECLINED' && $event_attendee['delegated-from']) {
               foreach ($existing['attendees'] as $i => $attendee) {
                 if ($attendee['email'] == $event_attendee['delegated-from']) {
                   $existing['attendees'][$i]['rsvp'] = true;
                   break;
                 }
               }
             }
 
             // Accept sender as a new participant (different email in From: and the iTip)
             // Use ATTENDEE entry from the iTip with replaced email address
             if (!$event_attendee) {
               // remove the organizer
               $itip_attendees = array_filter($event['attendees'], function($item) { return $item['role'] != 'ORGANIZER'; });
 
               // there must be only one attendee
               if (is_array($itip_attendees) && count($itip_attendees) == 1) {
                 $event_attendee          = $itip_attendees[key($itip_attendees)];
                 $event_attendee['email'] = $event['_sender'];
                 $update_attendees[]      = $event_attendee;
                 $metadata['fallback']    = $event_attendee['status'];
                 $metadata['attendee']    = $event_attendee['email'];
                 $metadata['rsvp']        = $event_attendee['rsvp'] || $event_attendee['role'] != 'NON-PARTICIPANT';
               }
             }
 
             // found matching attendee entry in both existing and new events
             if ($existing_attendee >= 0 && $event_attendee) {
               $existing['attendees'][$existing_attendee] = $event_attendee;
               $success = $this->driver->update_attendees($existing, $update_attendees);
             }
             // update the entire attendees block
             else if (($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed']) && $event_attendee) {
               $existing['attendees'][] = $event_attendee;
               $success = $this->driver->update_attendees($existing, $update_attendees);
             }
             else if (!$event_attendee) {
               $error_msg = $this->gettext('errorunknownattendee');
             }
             else {
               $error_msg = $this->gettext('newerversionexists');
             }
           }
           // delete the event when declined (#1670)
           else if ($status == 'declined' && $delete) {
              $deleted = $this->driver->remove_event($existing, true);
              $success = true;
           }
           // import the (newer) event
           else if ($event['sequence'] >= $existing['sequence'] || $event['changed'] >= $existing['changed']) {
             $event['id'] = $existing['id'];
             $event['calendar'] = $existing['calendar'];
 
             // merge attendees status
             // e.g. preserve my participant status for regular updates
             $this->lib->merge_attendees($event, $existing, $status);
 
             // set status=CANCELLED on CANCEL messages
             if ($event['_method'] == 'CANCEL')
               $event['status'] = 'CANCELLED';
 
             // update attachments list, allow attachments update only on REQUEST (#5342)
             if ($event['_method'] == 'REQUEST')
               $event['deleted_attachments'] = true;
             else
               unset($event['attachments']);
 
             // show me as free when declined (#1670)
             if ($status == 'declined' || $event['status'] == 'CANCELLED' || $event_attendee['role'] == 'NON-PARTICIPANT')
               $event['free_busy'] = 'free';
 
             $success = $this->driver->edit_event($event);
           }
           else if (!empty($status)) {
             $existing['attendees'] = $event['attendees'];
             if ($status == 'declined' || $event_attendee['role'] == 'NON-PARTICIPANT')  // show me as free when declined (#1670)
               $existing['free_busy'] = 'free';
             $success = $this->driver->edit_event($existing);
           }
           else
             $error_msg = $this->gettext('newerversionexists');
         }
         else if (!$existing && ($status != 'declined' || $this->rc->config->get('kolab_invitation_calendars'))) {
           if ($status == 'declined' || $event['status'] == 'CANCELLED' || $event_attendee['role'] == 'NON-PARTICIPANT') {
             $event['free_busy'] = 'free';
           }
 
           // if the RSVP reply only refers to a single instance:
           // store unmodified master event with current instance as exception
           if (!empty($instance) && !empty($savemode) && $savemode != 'all') {
             $master = $this->lib->mail_get_itip_object($mbox, $uid, $mime_id, 'event');
             if ($master['recurrence'] && !$master['_instance']) {
               // compute recurring events until this instance's date
               if ($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'] = $comment;
       $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()
   {
     $this->ui->init();
     $this->ui->addJS();
     $this->ui->init_templates();
     $this->ui->calendar_list(array(), true); // set env['calendars']
 
     $uid   = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GET);
     $mbox  = rcube_utils::get_input_value('_mbox', rcube_utils::INPUT_GET);
     $event = array();
 
     // establish imap connection
     $imap    = $this->rc->get_storage();
     $message = new rcube_message($uid, $mbox);
 
     if ($message->headers) {
       $event['title']       = trim($message->subject);
       $event['description'] = trim($message->first_text_part());
 
       $this->load_driver();
 
       // add a reference to the email message
       if ($msgref = $this->driver->get_message_reference($message->headers, $mbox)) {
         $event['links'] = array($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->set_env('event_prop', $event);
     }
     else {
       $this->rc->output->command('display_message', $this->gettext('messageopenerror'), 'error');
     }
 
     $this->rc->output->send('calendar.dialog');
   }
 
   /**
    * Handler for the 'message_compose' plugin hook. This will check for
    * a compose parameter 'calendar_event' and create an attachment with the
    * referenced event in iCal format
    */
   public function mail_message_compose($args)
   {
     // set the submitted event ID as attachment
     if (!empty($args['param']['calendar_event'])) {
       $this->load_driver();
 
       list($cal, $id) = explode(':', $args['param']['calendar_event'], 2);
       if ($event = $this->driver->get_event(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'     => $filename . '.ics',
           'mimetype' => 'text/calendar',
           'size'     => filesize($tmp_path),
         );
         $args['param']['subject'] = $event['title'];
       }
     }
 
     return $args;
   }
 
 
   /**
    * Get a list of email addresses of the current user (from login and identities)
    */
   public function get_user_emails()
   {
     return $this->lib->get_user_emails();
   }
 
 
   /**
    * Build an absolute URL with the given parameters
    */
   public function get_url($param = 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->setup();
      $this->load_driver();
      return $this->driver->user_delete($args);
   }
 
   /**
    * Find first occurrence of a recurring event excluding start date
    *
    * @param array $event Event data (with 'start' and 'recurrence')
    *
    * @return DateTime Date of the first occurrence
    */
   public function find_first_occurrence($event)
   {
     // Make sure libkolab plugin is loaded in case of Kolab driver
     $this->load_driver();
 
     // Use libkolab to compute recurring events (and libkolab plugin)
     // Horde-based fallback has many bugs
     if (class_exists('kolabformat') && class_exists('kolabcalendaring') && class_exists('kolab_date_recurrence')) {
       $object = kolab_format::factory('event', 3.0);
       $object->set($event);
 
       $recurrence = new kolab_date_recurrence($object);
     }
     else {
       // fallback to libcalendaring (Horde-based) recurrence implementation
       require_once(__DIR__ . '/lib/calendar_recurrence.php');
       $recurrence = new calendar_recurrence($this, $event);
     }
 
     return $recurrence->first_occurrence();
   }
 
   /**
    * Get date-time input from UI and convert to unix timestamp
    */
   protected function input_timestamp($name, $type)
   {
     $ts = rcube_utils::get_input_value($name, $type);
 
     if ($ts && (!is_numeric($ts) || strpos($ts, 'T'))) {
       $ts = new DateTime($ts, $this->timezone);
       $ts = $ts->getTimestamp();
     }
 
     return $ts;
   }
 
   /**
    * Magic getter for public access to protected members
    */
   public function __get($name)
   {
     switch ($name) {
       case 'ical':
         return $this->get_ical();
 
       case 'itip':
         return $this->load_itip();
 
       case 'driver':
         $this->load_driver();
         return $this->driver;
     }
 
     return null;
   }
 
 }
diff --git a/plugins/calendar/composer.json b/plugins/calendar/composer.json
index aac326f9..195ae845 100644
--- a/plugins/calendar/composer.json
+++ b/plugins/calendar/composer.json
@@ -1,38 +1,38 @@
 {
     "name": "kolab/calendar",
     "type": "roundcube-plugin",
     "description": "Calendar plugin",
     "homepage": "https://git.kolab.org/diffusion/RPK/",
     "license": "AGPLv3",
     "version": "3.5.5",
     "authors": [
         {
             "name": "Thomas Bruederli",
             "email": "bruederli@kolabsys.com",
             "role": "Lead"
         },
         {
             "name": "Aleksander Machniak",
             "email": "machniak@kolabsys.com",
             "role": "Developer"
         }
     ],
     "repositories": [
         {
             "type": "composer",
             "url": "https://plugins.roundcube.net"
         }
     ],
     "require": {
-        "php": ">=5.3.0",
+        "php": ">=5.4.0",
         "roundcube/plugin-installer": ">=0.1.3",
         "kolab/libcalendaring": ">=3.4.0",
         "kolab/libkolab": ">=3.4.0"
     },
      "extra": {
         "roundcube": {
             "min-version": "1.4.0",
             "sql-dir": "drivers/database/SQL"
         }
     }
 }
diff --git a/plugins/calendar/drivers/calendar_driver.php b/plugins/calendar/drivers/calendar_driver.php
index a0161193..2c0fc6c8 100644
--- a/plugins/calendar/drivers/calendar_driver.php
+++ b/plugins/calendar/drivers/calendar_driver.php
@@ -1,833 +1,863 @@
 <?php
 
 /**
  * Driver interface for the Calendar plugin
  *
  * @version @package_version@
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 /**
  * Struct of an internal event object how it is passed from/to the driver classes:
  *
  *  $event = array(
  *            'id' => 'Event ID used for editing',
  *           'uid' => 'Unique identifier of this event',
  *      'calendar' => 'Calendar identifier to add event to or where the event is stored',
  *         'start' => DateTime,  // Event start date/time as DateTime object
  *           'end' => DateTime,  // Event end date/time as DateTime object
  *        'allday' => true|false,  // Boolean flag if this is an all-day event
  *       'changed' => DateTime,    // Last modification date of event
  *         'title' => 'Event title/summary',
  *      'location' => 'Location string',
  *   'description' => 'Event description',
  *           'url' => 'URL to more information',
  *    'recurrence' => array(   // Recurrence definition according to iCalendar (RFC 2445) specification as list of key-value pairs
  *            'FREQ' => 'DAILY|WEEKLY|MONTHLY|YEARLY',
  *        'INTERVAL' => 1...n,
  *           'UNTIL' => DateTime,
  *           'COUNT' => 1..n,   // number of times
  *                      // + more properties (see http://www.kanzaki.com/docs/ical/recur.html)
  *          'EXDATE' => array(),  // list of DateTime objects of exception Dates/Times
  *      'EXCEPTIONS' => array(<event>),  list of event objects which denote exceptions in the recurrence chain
  *    ),
  * 'recurrence_id' => 'ID of the recurrence group',   // usually the ID of the starting event
  *     '_instance' => 'ID of the recurring instance',   // identifies an instance within a recurrence chain
  *    'categories' => 'Event category',
  *     'free_busy' => 'free|busy|outofoffice|tentative',  // Show time as
  *        'status' => 'TENTATIVE|CONFIRMED|CANCELLED',    // event status according to RFC 2445
  *      'priority' => 0-9,     // Event priority (0=undefined, 1=highest, 9=lowest)
  *   'sensitivity' => 'public|private|confidential',   // Event sensitivity
  *        'alarms' => '-15M:DISPLAY',  // DEPRECATED Reminder settings inspired by valarm definition (e.g. display alert 15 minutes before event)
  *       'valarms' => array(           // List of reminders (new format), each represented as a hash array:
  *                  array(
  *                     'trigger' => '-PT90M',     // ISO 8601 period string prefixed with '+' or '-', or DateTime object
  *                      'action' => 'DISPLAY|EMAIL|AUDIO',
  *                    'duration' => 'PT15M',      // ISO 8601 period string
  *                      'repeat' => 0,            // number of repetitions
  *                 'description' => '',        // text to display for DISPLAY actions
  *                     'summary' => '',        // message text for EMAIL actions
  *                   'attendees' => array(),   // list of email addresses to receive alarm messages
  *                  ),
  *   ),
  *   'attachments' => array(   // List of attachments
  *            'name' => 'File name',
  *        'mimetype' => 'Content type',
  *            'size' => 1..n, // in bytes
  *              'id' => 'Attachment identifier'
  *   ),
  * 'deleted_attachments' => array(), // array of attachment identifiers to delete when event is updated
  *     'attendees' => array(   // List of event participants
  *            'name' => 'Participant name',
  *           'email' => 'Participant e-mail address',  // used as identifier
  *            'role' => 'ORGANIZER|REQ-PARTICIPANT|OPT-PARTICIPANT|CHAIR',
  *          'status' => 'NEEDS-ACTION|UNKNOWN|ACCEPTED|TENTATIVE|DECLINED'
  *            'rsvp' => true|false,
  *    ),
  *
  *     '_savemode' => 'all|future|current|new',   // How changes on recurring event should be handled
  *       '_notify' => true|false,  // whether to notify event attendees about changes
  * '_fromcalendar' => 'Calendar identifier where the event was stored before',
  *  );
  */
 
 /**
  * Interface definition for calendar driver classes
  */
 abstract class calendar_driver
 {
-  const FILTER_ALL           = 0;
-  const FILTER_WRITEABLE     = 1;
-  const FILTER_INSERTABLE    = 2;
-  const FILTER_ACTIVE        = 4;
-  const FILTER_PERSONAL      = 8;
-  const FILTER_PRIVATE       = 16;
-  const FILTER_CONFIDENTIAL  = 32;
-  const FILTER_SHARED        = 64;
-  const BIRTHDAY_CALENDAR_ID = '__bdays__';
-
-  // features supported by backend
-  public $alarms = false;
-  public $attendees = false;
-  public $freebusy = false;
-  public $attachments = false;
-  public $undelete = false;
-  public $history = false;
-  public $categoriesimmutable = false;
-  public $alarm_types = array('DISPLAY');
-  public $alarm_absolute = true;
-  public $last_error;
-
-  protected $default_categories = array(
-    'Personal' => 'c0c0c0',
-    'Work'     => 'ff0000',
-    'Family'   => '00ff00',
-    'Holiday'  => 'ff6600',
-  );
-
-  /**
-   * Get a list of available calendars from this source
-   *
-   * @param integer Bitmask defining filter criterias.
-   *          See FILTER_* constants for possible values.
-   * @return array List of calendars
-   */
-  abstract function list_calendars($filter = 0);
-
-  /**
-   * Create a new calendar assigned to the current user
-   *
-   * @param array Hash array with calendar properties
-   *        name: Calendar name
-   *       color: The color of the calendar
-   *  showalarms: True if alarms are enabled
-   * @return mixed ID of the calendar on success, False on error
-   */
-  abstract function create_calendar($prop);
-
-  /**
-   * Update properties of an existing calendar
-   *
-   * @param array Hash array with calendar properties
-   *          id: Calendar Identifier
-   *        name: Calendar name
-   *       color: The color of the calendar
-   *  showalarms: True if alarms are enabled (if supported)
-   * @return boolean True on success, Fales on failure
-   */
-  abstract function edit_calendar($prop);
-  
-  /**
-   * Set active/subscribed state of a calendar
-   *
-   * @param array Hash array with calendar properties
-   *          id: Calendar Identifier
-   *      active: True if calendar is active, false if not
-   * @return boolean True on success, Fales on failure
-   */
-  abstract function subscribe_calendar($prop);
-
-  /**
-   * Delete the given calendar with all its contents
-   *
-   * @param array Hash array with calendar properties
-   *      id: Calendar Identifier
-   * @return boolean True on success, Fales on failure
-   */
-  abstract function delete_calendar($prop);
-
-  /**
-   * Search for shared or otherwise not listed calendars the user has access
-   *
-   * @param string Search string
-   * @param string Section/source to search
-   * @return array List of calendars
-   */
-  abstract function search_calendars($query, $source);
-
-  /**
-   * Add a single event to the database
-   *
-   * @param array Hash array with event properties (see header of this file)
-   * @return mixed New event ID on success, False on error
-   */
-  abstract function new_event($event);
-
-  /**
-   * Update an event entry with the given data
-   *
-   * @param array Hash array with event properties (see header of this file)
-   * @return boolean True on success, False on error
-   */
-  abstract function edit_event($event);
-
-  /**
-   * Extended event editing with possible changes to the argument
-   *
-   * @param array  Hash array with event properties
-   * @param string New participant status
-   * @param array  List of hash arrays with updated attendees
-   * @return boolean True on success, False on error
-   */
-  public function edit_rsvp(&$event, $status, $attendees)
-  {
-    return $this->edit_event($event);
-  }
-
-  /**
-   * Update the participant status for the given attendee
-   *
-   * @param array  Hash array with event properties
-   * @param array  List of hash arrays each represeting an updated attendee
-   * @return boolean True on success, False on error
-   */
-  public function update_attendees(&$event, $attendees)
-  {
-    return $this->edit_event($event);
-  }
-
-  /**
-   * Move a single event
-   *
-   * @param array Hash array with event properties:
-   *      id: Event identifier
-   *   start: Event start date/time as DateTime object
-   *     end: Event end date/time as DateTime object
-   *  allday: Boolean flag if this is an all-day event
-   * @return boolean True on success, False on error
-   */
-  abstract function move_event($event);
-
-  /**
-   * Resize a single event
-   *
-   * @param array Hash array with event properties:
-   *      id: Event identifier
-   *   start: Event start date/time as DateTime object with timezone
-   *     end: Event end date/time as DateTime object with timezone
-   * @return boolean True on success, False on error
-   */
-  abstract function resize_event($event);
-
-  /**
-   * Remove a single event from the database
-   *
-   * @param array   Hash array with event properties:
-   *      id: Event identifier
-   * @param boolean Remove event irreversible (mark as deleted otherwise,
-   *                if supported by the backend)
-   *
-   * @return boolean True on success, False on error
-   */
-  abstract function remove_event($event, $force = true);
-
-  /**
-   * Restores a single deleted event (if supported)
-   *
-   * @param array Hash array with event properties:
-   *      id: Event identifier
-   *
-   * @return boolean True on success, False on error
-   */
-  public function restore_event($event)
-  {
-    return false;
-  }
-
-  /**
-   * Return data of a single event
-   *
-   * @param mixed  UID string or hash array with event properties:
-   *         id: Event identifier
-   *        uid: Event UID
-   *  _instance: Instance identifier in combination with uid (optional)
-   *   calendar: Calendar identifier (optional)
-   * @param integer Bitmask defining the scope to search events in.
-   *          See FILTER_* constants for possible values.
-   * @param boolean If true, recurrence exceptions shall be added
-   *
-   * @return array Event object as hash array
-   */
-  abstract function get_event($event, $scope = 0, $full = false);
-
-  /**
-   * Get events from source.
-   *
-   * @param  integer Date range start (unix timestamp)
-   * @param  integer Date range end (unix timestamp)
-   * @param  string  Search query (optional)
-   * @param  mixed   List of calendar IDs to load events from (either as array or comma-separated string)
-   * @param  boolean Include virtual/recurring events (optional)
-   * @param  integer Only list events modified since this time (unix timestamp)
-   * @return array A list of event objects (see header of this file for struct of an event)
-   */
-  abstract function load_events($start, $end, $query = null, $calendars = null, $virtual = 1, $modifiedsince = null);
-
-  /**
-   * Get number of events in the given calendar
-   *
-   * @param  mixed   List of calendar IDs to count events (either as array or comma-separated string)
-   * @param  integer Date range start (unix timestamp)
-   * @param  integer Date range end (unix timestamp)
-   * @return array   Hash array with counts grouped by calendar ID
-   */
-  abstract function count_events($calendars, $start, $end = null);
-
-  /**
-   * Get a list of pending alarms to be displayed to the user
-   *
-   * @param  integer Current time (unix timestamp)
-   * @param  mixed   List of calendar IDs to show alarms for (either as array or comma-separated string)
-   * @return array A list of alarms, each encoded as hash array:
-   *         id: Event identifier
-   *        uid: Unique identifier of this event
-   *      start: Event start date/time as DateTime object
-   *        end: Event end date/time as DateTime object
-   *     allday: Boolean flag if this is an all-day event
-   *      title: Event title/summary
-   *   location: Location string
-   */
-  abstract function pending_alarms($time, $calendars = null);
-
-  /**
-   * (User) feedback after showing an alarm notification
-   * This should mark the alarm as 'shown' or snooze it for the given amount of time
-   *
-   * @param  string  Event identifier
-   * @param  integer Suspend the alarm for this number of seconds
-   */
-  abstract function dismiss_alarm($event_id, $snooze = 0);
-
-  /**
-   * Check the given event object for validity
-   *
-   * @param array Event object as hash array
-   * @return boolean True if valid, false if not
-   */
-  public function validate($event)
-  {
-    $valid = true;
-
-    if (!is_object($event['start']) || !is_a($event['start'], 'DateTime'))
-      $valid = false;
-    if (!is_object($event['end']) || !is_a($event['end'], 'DateTime'))
-      $valid = false;
-
-    return $valid;
-  }
-
-
-  /**
-   * Get list of event's attachments.
-   * Drivers can return list of attachments as event property.
-   * If they will do not do this list_attachments() method will be used.
-   *
-   * @param array $event Hash array with event properties:
-   *         id: Event identifier
-   *   calendar: Calendar identifier
-   *
-   * @return array List of attachments, each as hash array:
-   *         id: Attachment identifier
-   *       name: Attachment name
-   *   mimetype: MIME content type of the attachment
-   *       size: Attachment size
-   */
-  public function list_attachments($event) { }
-
-  /**
-   * Get attachment properties
-   *
-   * @param string $id    Attachment identifier
-   * @param array  $event Hash array with event properties:
-   *         id: Event identifier
-   *   calendar: Calendar identifier
-   *
-   * @return array Hash array with attachment properties:
-   *         id: Attachment identifier
-   *       name: Attachment name
-   *   mimetype: MIME content type of the attachment
-   *       size: Attachment size
-   */
-  public function get_attachment($id, $event) { }
-
-  /**
-   * Get attachment body
-   *
-   * @param string $id    Attachment identifier
-   * @param array  $event Hash array with event properties:
-   *         id: Event identifier
-   *   calendar: Calendar identifier
-   *
-   * @return string Attachment body
-   */
-  public function get_attachment_body($id, $event) { }
-
-  /**
-   * Build a struct representing the given message reference
-   *
-   * @param object|string $uri_or_headers rcube_message_header instance holding the message headers
-   *                         or an URI from a stored link referencing a mail message.
-   * @param string $folder  IMAP folder the message resides in
-   *
-   * @return array An struct referencing the given IMAP message
-   */
-  public function get_message_reference($uri_or_headers, $folder = null)
-  {
-      // to be implemented by the derived classes
-      return false;
-  }
-
-  /**
-   * List availabale categories
-   * The default implementation reads them from config/user prefs
-   */
-  public function list_categories()
-  {
-    $rcmail = rcube::get_instance();
-    return $rcmail->config->get('calendar_categories', $this->default_categories);
-  }
-
-  /**
-   * Create a new category
-   */
-  public function add_category($name, $color) { }
-
-  /**
-   * Remove the given category
-   */
-  public function remove_category($name) { }
-
-  /**
-   * Update/replace a category
-   */
-  public function replace_category($oldname, $name, $color) { }
-
-  /**
-   * Fetch free/busy information from a person within the given range
-   *
-   * @param string  E-mail address of attendee
-   * @param integer Requested period start date/time as unix timestamp
-   * @param integer Requested period end date/time as unix timestamp
-   *
-   * @return array  List of busy timeslots within the requested range
-   */
-  public function get_freebusy_list($email, $start, $end)
-  {
-    return false;
-  }
-
-  /**
-   * Create instances of a recurring event
-   *
-   * @param array  Hash array with event properties
-   * @param object DateTime Start date of the recurrence window
-   * @param object DateTime End date of the recurrence window
-   * @return array List of recurring event instances
-   */
-  public function get_recurring_events($event, $start, $end = null)
-  {
-    $events = array();
-
-    if ($event['recurrence']) {
-      // include library class
-      require_once(dirname(__FILE__) . '/../lib/calendar_recurrence.php');
-
-      $rcmail = rcmail::get_instance();
-      $recurrence = new calendar_recurrence($rcmail->plugins->get_plugin('calendar'), $event);
-      $recurrence_id_format = libcalendaring::recurrence_id_format($event);
-
-      // determine a reasonable end date if none given
-      if (!$end) {
-        switch ($event['recurrence']['FREQ']) {
-          case 'YEARLY':  $intvl = 'P100Y'; break;
-          case 'MONTHLY': $intvl = 'P20Y';  break;
-          default:        $intvl = 'P10Y';  break;
-        }
+    const FILTER_ALL           = 0;
+    const FILTER_WRITEABLE     = 1;
+    const FILTER_INSERTABLE    = 2;
+    const FILTER_ACTIVE        = 4;
+    const FILTER_PERSONAL      = 8;
+    const FILTER_PRIVATE       = 16;
+    const FILTER_CONFIDENTIAL  = 32;
+    const FILTER_SHARED        = 64;
+    const BIRTHDAY_CALENDAR_ID = '__bdays__';
+
+    // features supported by backend
+    public $alarms      = false;
+    public $attendees   = false;
+    public $freebusy    = false;
+    public $attachments = false;
+    public $undelete    = false;
+    public $history     = false;
+    public $alarm_types = ['DISPLAY'];
+    public $alarm_absolute      = true;
+    public $categoriesimmutable = false;
+    public $last_error;
+
+    protected $default_categories = [
+        'Personal' => 'c0c0c0',
+        'Work'     => 'ff0000',
+        'Family'   => '00ff00',
+        'Holiday'  => 'ff6600',
+    ];
+
+    /**
+     * Get a list of available calendars from this source
+     *
+     * @param int $filter Bitmask defining filter criterias.
+     *                    See FILTER_* constants for possible values.
+     *
+     * @return array List of calendars
+     */
+    abstract function list_calendars($filter = 0);
+
+    /**
+     * Create a new calendar assigned to the current user
+     *
+     * @param array $prop Hash array with calendar properties
+     *        name: Calendar name
+     *       color: The color of the calendar
+     *  showalarms: True if alarms are enabled
+     *
+     * @return mixed ID of the calendar on success, False on error
+     */
+    abstract function create_calendar($prop);
+
+    /**
+     * Update properties of an existing calendar
+     *
+     * @param array $prop Hash array with calendar properties
+     *          id: Calendar Identifier
+     *        name: Calendar name
+     *       color: The color of the calendar
+     *  showalarms: True if alarms are enabled (if supported)
+     *
+     * @return bool True on success, Fales on failure
+     */
+    abstract function edit_calendar($prop);
+
+    /**
+     * Set active/subscribed state of a calendar
+     *
+     * @param array $prop Hash array with calendar properties
+     *          id: Calendar Identifier
+     *      active: True if calendar is active, false if not
+     *
+     * @return bool True on success, Fales on failure
+     */
+    abstract function subscribe_calendar($prop);
+
+    /**
+     * Delete the given calendar with all its contents
+     *
+     * @param array $prop Hash array with calendar properties
+     *      id: Calendar Identifier
+     *
+     * @return bool True on success, Fales on failure
+     */
+    abstract function delete_calendar($prop);
+
+    /**
+     * Search for shared or otherwise not listed calendars the user has access
+     *
+     * @param string $query  Search string
+     * @param string $source Section/source to search
+     *
+     * @return array List of calendars
+     */
+    abstract function search_calendars($query, $source);
+
+    /**
+     * Add a single event to the database
+     *
+     * @param array $event Hash array with event properties (see header of this file)
+     *
+     * @return mixed New event ID on success, False on error
+     */
+    abstract function new_event($event);
+
+    /**
+     * Update an event entry with the given data
+     *
+     * @param array $event Hash array with event properties (see header of this file)
+     *
+     * @return bool True on success, False on error
+     */
+    abstract function edit_event($event);
+
+    /**
+     * Extended event editing with possible changes to the argument
+     *
+     * @param array  &$event    Hash array with event properties
+     * @param string $status    New participant status
+     * @param array  $attendees List of hash arrays with updated attendees
+     *
+     * @return bool True on success, False on error
+     */
+    public function edit_rsvp(&$event, $status, $attendees)
+    {
+        return $this->edit_event($event);
+    }
 
-        $end = clone $event['start'];
-        $end->add(new DateInterval($intvl));
-      }
-
-      $i = 0;
-      while ($next_event = $recurrence->next_instance()) {
-        // add to output if in range
-        if (($next_event['start'] <= $end && $next_event['end'] >= $start)) {
-          $next_event['_instance'] = $next_event['start']->format($recurrence_id_format);
-          $next_event['id'] = $next_event['uid'] . '-' . $exception['_instance'];
-          $next_event['recurrence_id'] = $event['uid'];
-          $events[] = $next_event;
+    /**
+     * Update the participant status for the given attendee
+     *
+     * @param array &$event    Hash array with event properties
+     * @param array $attendees List of hash arrays each represeting an updated attendee
+     *
+     * @return bool True on success, False on error
+     */
+    public function update_attendees(&$event, $attendees)
+    {
+        return $this->edit_event($event);
+    }
+
+    /**
+     * Move a single event
+     *
+     * @param array $event Hash array with event properties:
+     *      id: Event identifier
+     *   start: Event start date/time as DateTime object
+     *     end: Event end date/time as DateTime object
+     *  allday: Boolean flag if this is an all-day event
+     *
+     * @return bool True on success, False on error
+     */
+    abstract function move_event($event);
+
+    /**
+     * Resize a single event
+     *
+     * @param array $event Hash array with event properties:
+     *      id: Event identifier
+     *   start: Event start date/time as DateTime object with timezone
+     *     end: Event end date/time as DateTime object with timezone
+     *
+     * @return bool True on success, False on error
+     */
+    abstract function resize_event($event);
+
+    /**
+     * Remove a single event from the database
+     *
+     * @param array $event Hash array with event properties:
+     *                     id: Event identifier
+     * @param bool  $force Remove event irreversible (mark as deleted otherwise,
+     *                     if supported by the backend)
+     *
+     * @return bool True on success, False on error
+     */
+    abstract function remove_event($event, $force = true);
+
+    /**
+     * Restores a single deleted event (if supported)
+     *
+     * @param array $event Hash array with event properties:
+     *                     id: Event identifier
+     *
+     * @return bool True on success, False on error
+     */
+    public function restore_event($event)
+    {
+        return false;
+    }
+
+    /**
+     * Return data of a single event
+     *
+     * @param mixed $event UID string or hash array with event properties:
+     *         id: Event identifier
+     *        uid: Event UID
+     *  _instance: Instance identifier in combination with uid (optional)
+     *   calendar: Calendar identifier (optional)
+     * @param int   $scope Bitmask defining the scope to search events in.
+     *                     See FILTER_* constants for possible values.
+     * @param bool  $full  If true, recurrence exceptions shall be added
+     *
+     * @return array Event object as hash array
+     */
+    abstract function get_event($event, $scope = 0, $full = false);
+
+    /**
+     * Get events from source.
+     *
+     * @param int    $start      Date range start (unix timestamp)
+     * @param int    $end        Date range end (unix timestamp)
+     * @param string $query      Search query (optional)
+     * @param mixed  $calendars  List of calendar IDs to load events from (either as array or comma-separated string)
+     * @param bool   $virtual    Include virtual/recurring events (optional)
+     * @param int    $modifiedsince Only list events modified since this time (unix timestamp)
+     *
+     * @return array A list of event objects (see header of this file for struct of an event)
+     */
+    abstract function load_events($start, $end, $query = null, $calendars = null, $virtual = 1, $modifiedsince = null);
+
+    /**
+     * Get number of events in the given calendar
+     *
+     * @param mixed $calendars List of calendar IDs to count events (either as array or comma-separated string)
+     * @param int   $start     Date range start (unix timestamp)
+     * @param int   $end       Date range end (unix timestamp)
+     *
+     * @return array   Hash array with counts grouped by calendar ID
+     */
+    abstract function count_events($calendars, $start, $end = null);
+
+    /**
+     * Get a list of pending alarms to be displayed to the user
+     *
+     * @param int   $time      Current time (unix timestamp)
+     * @param mixed $calendars List of calendar IDs to show alarms for (either as array or comma-separated string)
+     *
+     * @return array A list of alarms, each encoded as hash array:
+     *         id: Event identifier
+     *        uid: Unique identifier of this event
+     *      start: Event start date/time as DateTime object
+     *        end: Event end date/time as DateTime object
+     *     allday: Boolean flag if this is an all-day event
+     *      title: Event title/summary
+     *   location: Location string
+     */
+    abstract function pending_alarms($time, $calendars = null);
+
+    /**
+     * (User) feedback after showing an alarm notification
+     * This should mark the alarm as 'shown' or snooze it for the given amount of time
+     *
+     * @param string $event_id Event identifier
+     * @param int    $snooze   Suspend the alarm for this number of seconds
+     */
+    abstract function dismiss_alarm($event_id, $snooze = 0);
+
+    /**
+     * Check the given event object for validity
+     *
+     * @param array $event Event object as hash array
+     *
+     * @return boolean True if valid, false if not
+     */
+    public function validate($event)
+    {
+        $valid = true;
+
+        if (empty($event['start']) || !is_object($event['start']) || !is_a($event['start'], 'DateTime')) {
+            $valid = false;
         }
-        else if ($next_event['start'] > $end) {  // stop loop if out of range
-          break;
+
+        if (empty($event['end']) || !is_object($event['end']) || !is_a($event['end'], 'DateTime')) {
+            $valid = false;
         }
 
-        // avoid endless recursion loops
-        if (++$i > 1000) {
-          break;
+        return $valid;
+    }
+
+    /**
+     * Get list of event's attachments.
+     * Drivers can return list of attachments as event property.
+     * If they will do not do this list_attachments() method will be used.
+     *
+     * @param array $event Hash array with event properties:
+     *         id: Event identifier
+     *   calendar: Calendar identifier
+     *
+     * @return array List of attachments, each as hash array:
+     *         id: Attachment identifier
+     *       name: Attachment name
+     *   mimetype: MIME content type of the attachment
+     *       size: Attachment size
+     */
+    public function list_attachments($event) { }
+
+    /**
+     * Get attachment properties
+     *
+     * @param string $id    Attachment identifier
+     * @param array  $event Hash array with event properties:
+     *         id: Event identifier
+     *   calendar: Calendar identifier
+     *
+     * @return array Hash array with attachment properties:
+     *         id: Attachment identifier
+     *       name: Attachment name
+     *   mimetype: MIME content type of the attachment
+     *       size: Attachment size
+     */
+    public function get_attachment($id, $event) { }
+
+    /**
+     * Get attachment body
+     *
+     * @param string $id    Attachment identifier
+     * @param array  $event Hash array with event properties:
+     *         id: Event identifier
+     *   calendar: Calendar identifier
+     *
+     * @return string Attachment body
+     */
+    public function get_attachment_body($id, $event) { }
+
+    /**
+     * Build a struct representing the given message reference
+     *
+     * @param object|string $uri_or_headers rcube_message_header instance holding the message headers
+     *                         or an URI from a stored link referencing a mail message.
+     * @param string $folder  IMAP folder the message resides in
+     *
+     * @return array An struct referencing the given IMAP message
+     */
+    public function get_message_reference($uri_or_headers, $folder = null)
+    {
+        // to be implemented by the derived classes
+        return false;
+    }
+
+    /**
+     * List availabale categories
+     * The default implementation reads them from config/user prefs
+     */
+    public function list_categories()
+    {
+        $rcmail = rcube::get_instance();
+        return $rcmail->config->get('calendar_categories', $this->default_categories);
+    }
+
+    /**
+     * Create a new category
+     */
+    public function add_category($name, $color) { }
+
+    /**
+     * Remove the given category
+     */
+    public function remove_category($name) { }
+
+    /**
+     * Update/replace a category
+     */
+    public function replace_category($oldname, $name, $color) { }
+
+    /**
+     * Fetch free/busy information from a person within the given range
+     *
+     * @param string $email E-mail address of attendee
+     * @param int    $start Requested period start date/time as unix timestamp
+     * @param int    $end   Requested period end date/time as unix timestamp
+     *
+     * @return array List of busy timeslots within the requested range
+     */
+    public function get_freebusy_list($email, $start, $end)
+    {
+        return false;
+    }
+
+    /**
+     * Create instances of a recurring event
+     *
+     * @param array    $event Hash array with event properties
+     * @param DateTime $start Start date of the recurrence window
+     * @param DateTime $end   End date of the recurrence window
+     *
+     * @return array List of recurring event instances
+     */
+    public function get_recurring_events($event, $start, $end = null)
+    {
+        $events = [];
+
+        if (!empty($event['recurrence'])) {
+            // include library class
+            require_once(dirname(__FILE__) . '/../lib/calendar_recurrence.php');
+
+            $rcmail = rcmail::get_instance();
+            $recurrence = new calendar_recurrence($rcmail->plugins->get_plugin('calendar'), $event);
+            $recurrence_id_format = libcalendaring::recurrence_id_format($event);
+
+            // determine a reasonable end date if none given
+            if (!$end) {
+                switch ($event['recurrence']['FREQ']) {
+                case 'YEARLY':  $intvl = 'P100Y'; break;
+                case 'MONTHLY': $intvl = 'P20Y';  break;
+                default:        $intvl = 'P10Y';  break;
+                }
+
+                $end = clone $event['start'];
+                $end->add(new DateInterval($intvl));
+            }
+
+            $i = 0;
+            while ($next_event = $recurrence->next_instance()) {
+                // add to output if in range
+                if (($next_event['start'] <= $end && $next_event['end'] >= $start)) {
+                    $next_event['_instance'] = $next_event['start']->format($recurrence_id_format);
+                    $next_event['id'] = $next_event['uid'] . '-' . $exception['_instance'];
+                    $next_event['recurrence_id'] = $event['uid'];
+                    $events[] = $next_event;
+                }
+                else if ($next_event['start'] > $end) {  // stop loop if out of range
+                    break;
+                }
+
+                // avoid endless recursion loops
+                if (++$i > 1000) {
+                    break;
+                }
+            }
         }
-      }
+
+        return $events;
+    }
+
+    /**
+     * Provide a list of revisions for the given event
+     *
+     * @param array $event Hash array with event properties:
+     *         id: Event identifier
+     *   calendar: Calendar identifier
+     *
+     * @return array List of changes, each as a hash array:
+     *         rev: Revision number
+     *        type: Type of the change (create, update, move, delete)
+     *        date: Change date
+     *        user: The user who executed the change
+     *          ip: Client IP
+     * destination: Destination calendar for 'move' type
+     */
+    public function get_event_changelog($event)
+    {
+        return false;
+    }
+
+    /**
+     * Get a list of property changes beteen two revisions of an event
+     *
+     * @param array $event Hash array with event properties:
+     *         id: Event identifier
+     *   calendar: Calendar identifier
+     * @param mixed $rev1 Old Revision
+     * @param mixed $rev2 New Revision
+     *
+     * @return array List of property changes, each as a hash array:
+     *    property: Revision number
+     *         old: Old property value
+     *         new: Updated property value
+     */
+    public function get_event_diff($event, $rev1, $rev2)
+    {
+        return false;
     }
 
-    return $events;
-  }
-
-  /**
-   * Provide a list of revisions for the given event
-   *
-   * @param array  $event Hash array with event properties:
-   *         id: Event identifier
-   *   calendar: Calendar identifier
-   *
-   * @return array List of changes, each as a hash array:
-   *         rev: Revision number
-   *        type: Type of the change (create, update, move, delete)
-   *        date: Change date
-   *        user: The user who executed the change
-   *          ip: Client IP
-   * destination: Destination calendar for 'move' type
-   */
-  public function get_event_changelog($event)
-  {
-    return false;
-  }
-
-  /**
-   * Get a list of property changes beteen two revisions of an event
-   *
-   * @param array $event Hash array with event properties:
-   *         id: Event identifier
-   *   calendar: Calendar identifier
-   * @param mixed $rev1 Old Revision
-   * @param mixed $rev2 New Revision
-   *
-   * @return array List of property changes, each as a hash array:
-   *    property: Revision number
-   *         old: Old property value
-   *         new: Updated property value
-   */
-  public function get_event_diff($event, $rev1, $rev2)
-  {
-    return false;
-  }
-
-  /**
-   * Return full data of a specific revision of an event
-   *
-   * @param mixed  UID string or hash array with event properties:
-   *        id: Event identifier
-   *  calendar: Calendar identifier
-   * @param mixed  $rev Revision number
-   *
-   * @return array Event object as hash array
-   * @see self::get_event()
-   */
-  public function get_event_revison($event, $rev)
-  {
-    return false;
-  }
-
-  /**
-   * Command the backend to restore a certain revision of an event.
-   * This shall replace the current event with an older version.
-   *
-   * @param mixed  UID string or hash array with event properties:
-   *        id: Event identifier
-   *  calendar: Calendar identifier
-   * @param mixed  $rev Revision number
-   *
-   * @return boolean True on success, False on failure
-   */
-  public function restore_event_revision($event, $rev)
-  {
-    return false;
-  }
-
-
-  /**
-   * Callback function to produce driver-specific calendar create/edit form
-   *
-   * @param string Request action 'form-edit|form-new'
-   * @param array  Calendar properties (e.g. id, color)
-   * @param array  Edit form fields
-   *
-   * @return string HTML content of the form
-   */
-  public function calendar_form($action, $calendar, $formfields)
-  {
-    $table = new html_table(array('cols' => 2, 'class' => 'propform'));
-
-    foreach ($formfields as $col => $colprop) {
-      $label = !empty($colprop['label']) ? $colprop['label'] : $rcmail->gettext("$domain.$col");
-
-      $table->add('title', html::label($colprop['id'], rcube::Q($label)));
-      $table->add(null, $colprop['value']);
+    /**
+     * Return full data of a specific revision of an event
+     *
+     * @param mixed $event UID string or hash array with event properties:
+     *        id: Event identifier
+     *  calendar: Calendar identifier
+     * @param mixed  $rev Revision number
+     *
+     * @return array Event object as hash array
+     * @see self::get_event()
+     */
+    public function get_event_revison($event, $rev)
+    {
+        return false;
     }
 
-    return $table->show();
-  }
-
-  /**
-   * Compose a list of birthday events from the contact records in the user's address books.
-   *
-   * This is a default implementation using Roundcube's address book API.
-   * It can be overriden with a more optimized version by the individual drivers.
-   *
-   * @param  integer Event's new start (unix timestamp)
-   * @param  integer Event's new end (unix timestamp)
-   * @param  string  Search query (optional)
-   * @param  integer Only list events modified since this time (unix timestamp)
-   * @return array A list of event records
-   */
-  public function load_birthday_events($start, $end, $search = null, $modifiedsince = null)
-  {
-    // ignore update requests for simplicity reasons
-    if (!empty($modifiedsince)) {
-      return array();
+    /**
+     * Command the backend to restore a certain revision of an event.
+     * This shall replace the current event with an older version.
+     *
+     * @param mixed $event UID string or hash array with event properties:
+     *        id: Event identifier
+     *  calendar: Calendar identifier
+     * @param mixed  $rev Revision number
+     *
+     * @return boolean True on success, False on failure
+     */
+    public function restore_event_revision($event, $rev)
+    {
+        return false;
     }
 
-    // convert to DateTime for comparisons
-    $start  = new DateTime('@'.$start);
-    $end    = new DateTime('@'.$end);
-    // extract the current year
-    $year   = $start->format('Y');
-    $year2  = $end->format('Y');
-
-    $events = array();
-    $search = mb_strtolower($search);
-    $rcmail = rcmail::get_instance();
-    $cache  = $rcmail->get_cache('calendar.birthdays', 'db', 3600);
-    $cache->expunge();
-
-    $alarm_type   = $rcmail->config->get('calendar_birthdays_alarm_type', '');
-    $alarm_offset = $rcmail->config->get('calendar_birthdays_alarm_offset', '-1D');
-    $alarms       = $alarm_type ? $alarm_offset . ':' . $alarm_type : null;
-
-    // let the user select the address books to consider in prefs
-    $selected_sources = $rcmail->config->get('calendar_birthday_adressbooks');
-    $sources = $selected_sources ?: array_keys($rcmail->get_address_sources(false, true));
-    foreach ($sources as $source) {
-      $abook = $rcmail->get_address_book($source);
-
-      // skip LDAP address books unless selected by the user
-      if (!$abook || ($abook instanceof rcube_ldap && empty($selected_sources))) {
-        continue;
-      }
-
-      $abook->set_pagesize(10000);
-
-      // check for cached results
-      $cache_records = array();
-      $cached = $cache->get($source);
-
-      // iterate over (cached) contacts
-      foreach (($cached ?: $abook->search('*', '', 2, true, true, array('birthday'))) as $contact) {
-        $event = self::parse_contact($contact, $source);
-
-        if (empty($event)) {
-          continue;
+    /**
+     * Callback function to produce driver-specific calendar create/edit form
+     *
+     * @param string $action     Request action 'form-edit|form-new'
+     * @param array  $calendar   Calendar properties (e.g. id, color)
+     * @param array  $formfields Edit form fields
+     *
+     * @return string HTML content of the form
+     */
+    public function calendar_form($action, $calendar, $formfields)
+    {
+        $table = new html_table(['cols' => 2, 'class' => 'propform']);
+
+        foreach ($formfields as $col => $colprop) {
+            $label = !empty($colprop['label']) ? $colprop['label'] : $rcmail->gettext("$domain.$col");
+
+            $table->add('title', html::label($colprop['id'], rcube::Q($label)));
+            $table->add(null, $colprop['value']);
         }
 
-        // add stripped record to cache
-        if (empty($cached)) {
-          $cache_records[] = array(
-            'ID'       => $contact['ID'],
-            'name'     => $event['_displayname'],
-            'birthday' => $event['start']->format('Y-m-d'),
-          );
+        return $table->show();
+    }
+
+    /**
+     * Compose a list of birthday events from the contact records in the user's address books.
+     *
+     * This is a default implementation using Roundcube's address book API.
+     * It can be overriden with a more optimized version by the individual drivers.
+     *
+     * @param int    $start         Event's new start (unix timestamp)
+     * @param int    $end           Event's new end (unix timestamp)
+     * @param string $search        Search query (optional)
+     * @param int    $modifiedsince Only list events modified since this time (unix timestamp)
+     *
+     * @return array A list of event records
+     */
+    public function load_birthday_events($start, $end, $search = null, $modifiedsince = null)
+    {
+        // ignore update requests for simplicity reasons
+        if (!empty($modifiedsince)) {
+            return [];
         }
 
-        // filter by search term (only name is involved here)
-        if (!empty($search) && strpos(mb_strtolower($event['title']), $search) === false) {
-          continue;
+        // convert to DateTime for comparisons
+        $start  = new DateTime('@'.$start);
+        $end    = new DateTime('@'.$end);
+        // extract the current year
+        $year   = $start->format('Y');
+        $year2  = $end->format('Y');
+
+        $events = [];
+        $search = mb_strtolower($search);
+        $rcmail = rcmail::get_instance();
+        $cache  = $rcmail->get_cache('calendar.birthdays', 'db', 3600);
+        $cache->expunge();
+
+        $alarm_type   = $rcmail->config->get('calendar_birthdays_alarm_type', '');
+        $alarm_offset = $rcmail->config->get('calendar_birthdays_alarm_offset', '-1D');
+        $alarms       = $alarm_type ? $alarm_offset . ':' . $alarm_type : null;
+
+        // let the user select the address books to consider in prefs
+        $selected_sources = $rcmail->config->get('calendar_birthday_adressbooks');
+        $sources = $selected_sources ?: array_keys($rcmail->get_address_sources(false, true));
+
+        foreach ($sources as $source) {
+            $abook = $rcmail->get_address_book($source);
+
+            // skip LDAP address books unless selected by the user
+            if (!$abook || ($abook instanceof rcube_ldap && empty($selected_sources))) {
+                continue;
+            }
+
+            // skip collected recipients/senders addressbooks
+            if (is_a($abook, 'rcube_addresses')) {
+                continue;
+            }
+
+            $abook->set_pagesize(10000);
+
+            // check for cached results
+            $cache_records = [];
+            $cached = $cache->get($source);
+
+            // iterate over (cached) contacts
+            foreach (($cached ?: $abook->search('*', '', 2, true, true, ['birthday'])) as $contact) {
+                $event = self::parse_contact($contact, $source);
+
+                if (empty($event)) {
+                    continue;
+                }
+
+                // add stripped record to cache
+                if (empty($cached)) {
+                    $cache_records[] = [
+                        'ID'       => $contact['ID'],
+                        'name'     => $event['_displayname'],
+                        'birthday' => $event['start']->format('Y-m-d'),
+                    ];
+                }
+
+                // filter by search term (only name is involved here)
+                if (!empty($search) && strpos(mb_strtolower($event['title']), $search) === false) {
+                    continue;
+                }
+
+                $bday  = clone $event['start'];
+                $byear = $bday->format('Y');
+
+                // quick-and-dirty recurrence computation: just replace the year
+                $bday->setDate($year, $bday->format('n'), $bday->format('j'));
+                $bday->setTime(12, 0, 0);
+                $this_year = $year;
+
+                // date range reaches over multiple years: use end year if not in range
+                if (($bday > $end || $bday < $start) && $year2 != $year) {
+                    $bday->setDate($year2, $bday->format('n'), $bday->format('j'));
+                    $this_year = $year2;
+                }
+
+                // birthday is within requested range
+                if ($bday <= $end && $bday >= $start) {
+                    unset($event['_displayname']);
+                    $event['alarms'] = $alarms;
+
+                    // if this is not the first occurence modify event details
+                    // but not when this is "all birthdays feed" request
+                    if ($year2 - $year < 10 && ($age = ($this_year - $byear))) {
+                        $label = ['name' => 'birthdayage', 'vars' => ['age' => $age]];
+
+                        $event['description'] = $rcmail->gettext($label, 'calendar');
+                        $event['start']       = $bday;
+                        $event['end']         = clone $bday;
+
+                        unset($event['recurrence']);
+                    }
+
+                    // add the main instance
+                    $events[] = $event;
+                }
+            }
+
+            // store collected contacts in cache
+            if (empty($cached)) {
+                $cache->write($source, $cache_records);
+            }
         }
 
-        $bday  = clone $event['start'];
-        $byear = $bday->format('Y');
+        return $events;
+    }
 
-        // quick-and-dirty recurrence computation: just replace the year
-        $bday->setDate($year, $bday->format('n'), $bday->format('j'));
-        $bday->setTime(12, 0, 0);
-        $this_year = $year;
+    /**
+     * Get a single birthday calendar event
+     */
+    public function get_birthday_event($id)
+    {
+        // decode $id
+        list(, $source, $contact_id, $year) = explode(':', rcube_ldap::dn_decode($id));
 
-        // date range reaches over multiple years: use end year if not in range
-        if (($bday > $end || $bday < $start) && $year2 != $year) {
-          $bday->setDate($year2, $bday->format('n'), $bday->format('j'));
-          $this_year = $year2;
-        }
+        $rcmail = rcmail::get_instance();
 
-        // birthday is within requested range
-        if ($bday <= $end && $bday >= $start) {
-          unset($event['_displayname']);
-          $event['alarms'] = $alarms;
-
-          // if this is not the first occurence modify event details
-          // but not when this is "all birthdays feed" request
-          if ($year2 - $year < 10 && ($age = ($this_year - $byear))) {
-            $event['description'] = $rcmail->gettext(array('name' => 'birthdayage', 'vars' => array('age' => $age)), 'calendar');
-            $event['start']       = $bday;
-            $event['end']         = clone $bday;
-            unset($event['recurrence']);
-          }
-
-          // add the main instance
-          $events[] = $event;
+        if (strlen($source) && $contact_id && ($abook = $rcmail->get_address_book($source))) {
+            if ($contact = $abook->get_record($contact_id, true)) {
+                return self::parse_contact($contact, $source);
+            }
         }
-      }
-
-      // store collected contacts in cache
-      if (empty($cached)) {
-        $cache->write($source, $cache_records);
-      }
     }
 
-    return $events;
-  }
+    /**
+     * Parse contact and create an event for its birthday
+     *
+     * @param array  $contact Contact data
+     * @param string $source  Addressbook source ID
+     *
+     * @return array|null Birthday event data
+     */
+    public static function parse_contact($contact, $source)
+    {
+        if (!is_array($contact)) {
+            return;
+        }
 
-  /**
-   * Get a single birthday calendar event
-   */
-  public function get_birthday_event($id)
-  {
-    // decode $id
-    list(,$source,$contact_id,$year) = explode(':', rcube_ldap::dn_decode($id));
+        if (!empty($contact['birthday']) && is_array($contact['birthday'])) {
+            $contact['birthday'] = reset($contact['birthday']);
+        }
 
-    $rcmail = rcmail::get_instance();
+        if (empty($contact['birthday'])) {
+            return;
+        }
 
-    if (strlen($source) && $contact_id && ($abook = $rcmail->get_address_book($source))) {
-      if ($contact = $abook->get_record($contact_id, true)) {
-        return self::parse_contact($contact, $source);
-      }
-    }
-  }
-
-  /**
-   * Parse contact and create an event for its birthday
-   *
-   * @param array  $contact Contact data
-   * @param string $source  Addressbook source ID
-   *
-   * @return array Birthday event data
-   */
-  public static function parse_contact($contact, $source)
-  {
-    if (!is_array($contact)) {
-      return;
-    }
+        try {
+            $bday = $contact['birthday'];
+            if (!$bday instanceof DateTime) {
+                $bday = new DateTime($bday, new DateTimezone('UTC'));
+            }
+            $bday->_dateonly = true;
+        }
+        catch (Exception $e) {
+            rcube::raise_error([
+                    'code' => 600,
+                    'file' => __FILE__,
+                    'line' => __LINE__,
+                    'message' => 'BIRTHDAY PARSE ERROR: ' . $e->getMessage()
+                ],
+                true, false
+            );
+            return;
+        }
 
-    if (is_array($contact['birthday'])) {
-      $contact['birthday'] = reset($contact['birthday']);
+        $rcmail       = rcmail::get_instance();
+        $birthyear    = $bday->format('Y');
+        $display_name = rcube_addressbook::compose_display_name($contact);
+        $label        = ['name' => 'birthdayeventtitle', 'vars' => ['name' => $display_name]];
+        $event_title  = $rcmail->gettext($label, 'calendar');
+        $uid          = rcube_ldap::dn_encode('bday:' . $source . ':' . $contact['ID'] . ':' . $birthyear);
+
+        return [
+            'id'           => $uid,
+            'uid'          => $uid,
+            'calendar'     => self::BIRTHDAY_CALENDAR_ID,
+            'title'        => $event_title,
+            'description'  => '',
+            'allday'       => true,
+            'start'        => $bday,
+            'end'          => clone $bday,
+            'recurrence'   => ['FREQ' => 'YEARLY', 'INTERVAL' => 1],
+            'free_busy'    => 'free',
+            '_displayname' => $display_name,
+        ];
     }
 
-    if (empty($contact['birthday'])) {
-      return;
+    /**
+     * Store alarm dismissal for birtual birthay events
+     *
+     * @param string $event_id Event identifier
+     * @param int    $snooze   Suspend the alarm for this number of seconds
+     */
+    public function dismiss_birthday_alarm($event_id, $snooze = 0)
+    {
+        $rcmail = rcmail::get_instance();
+        $cache  = $rcmail->get_cache('calendar.birthdayalarms', 'db', 86400 * 30);
+        $cache->remove($event_id);
+
+        // compute new notification time or disable if not snoozed
+        $notifyat = $snooze > 0 ? time() + $snooze : null;
+        $cache->set($event_id, ['snooze' => $snooze, 'notifyat' => $notifyat]);
+
+        return true;
     }
 
-    try {
-      $bday = $contact['birthday'];
-      if (!$bday instanceof DateTime) {
-        $bday = new DateTime($bday, new DateTimezone('UTC'));
-      }
-      $bday->_dateonly = true;
+    /**
+     * Handler for user_delete plugin hook
+     *
+     * @param array $args Hash array with hook arguments
+     *
+     * @return array Return arguments for plugin hooks
+     */
+    public function user_delete($args)
+    {
+        // TO BE OVERRIDDEN
+        return $args;
     }
-    catch (Exception $e) {
-      rcube::raise_error(array(
-          'code' => 600, 'type' => 'php',
-          'file' => __FILE__, 'line' => __LINE__,
-          'message' => 'BIRTHDAY PARSE ERROR: ' . $e->getMessage()),
-        true, false);
-      return;
-    }
-
-    $rcmail       = rcmail::get_instance();
-    $birthyear    = $bday->format('Y');
-    $display_name = rcube_addressbook::compose_display_name($contact);
-    $label        = array('name' => 'birthdayeventtitle', 'vars' => array('name' => $display_name));
-    $event_title  = $rcmail->gettext($label, 'calendar');
-    $uid          = rcube_ldap::dn_encode('bday:' . $source . ':' . $contact['ID'] . ':' . $birthyear);
-
-    $event = array(
-      'id'           => $uid,
-      'uid'          => $uid,
-      'calendar'     => self::BIRTHDAY_CALENDAR_ID,
-      'title'        => $event_title,
-      'description'  => '',
-      'allday'       => true,
-      'start'        => $bday,
-      'end'          => clone $bday,
-      'recurrence'   => array('FREQ' => 'YEARLY', 'INTERVAL' => 1),
-      'free_busy'    => 'free',
-      '_displayname' => $display_name,
-    );
-
-    return $event;
-  }
-
-  /**
-   * Store alarm dismissal for birtual birthay events
-   *
-   * @param  string  Event identifier
-   * @param  integer Suspend the alarm for this number of seconds
-   */
-  public function dismiss_birthday_alarm($event_id, $snooze = 0)
-  {
-    $rcmail = rcmail::get_instance();
-    $cache  = $rcmail->get_cache('calendar.birthdayalarms', 'db', 86400 * 30);
-    $cache->remove($event_id);
-
-    // compute new notification time or disable if not snoozed
-    $notifyat = $snooze > 0 ? time() + $snooze : null;
-    $cache->set($event_id, array('snooze' => $snooze, 'notifyat' => $notifyat));
-
-    return true;
-  }
-
-  /**
-   * Handler for user_delete plugin hook
-   *
-   * @param array Hash array with hook arguments
-   * @return array Return arguments for plugin hooks
-   */
-  public function user_delete($args)
-  {
-    // TO BE OVERRIDDEN
-    return $args;
-  }
 }
diff --git a/plugins/calendar/drivers/database/database_driver.php b/plugins/calendar/drivers/database/database_driver.php
index c057825b..699cb88a 100644
--- a/plugins/calendar/drivers/database/database_driver.php
+++ b/plugins/calendar/drivers/database/database_driver.php
@@ -1,1529 +1,1530 @@
 <?php
 
 /**
  * Database driver for the Calendar plugin
  *
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 class database_driver extends calendar_driver
 {
     const DB_DATE_FORMAT = 'Y-m-d H:i:s';
 
     public static $scheduling_properties = array('start', 'end', 'allday', 'recurrence', 'location', 'cancelled');
 
     // features this backend supports
     public $alarms      = true;
     public $attendees   = true;
     public $freebusy    = false;
     public $attachments = true;
     public $alarm_types = array('DISPLAY');
 
     private $rc;
     private $cal;
     private $cache           = array();
     private $calendars       = array();
     private $calendar_ids    = '';
     private $free_busy_map   = array('free' => 0, 'busy' => 1, 'out-of-office' => 2, 'outofoffice' => 2, 'tentative' => 3);
     private $sensitivity_map = array('public' => 0, 'private' => 1, 'confidential' => 2);
     private $server_timezone;
 
     private $db_events      = 'events';
     private $db_calendars   = 'calendars';
     private $db_attachments = 'attachments';
 
 
     /**
      * Default constructor
      */
     public function __construct($cal)
     {
         $this->cal             = $cal;
         $this->rc              = $cal->rc;
         $this->server_timezone = new DateTimeZone(date_default_timezone_get());
 
         // read database config
         $db = $this->rc->get_dbh();
         $this->db_events      = $db->table_name($this->rc->config->get('db_table_events', $this->db_events));
         $this->db_calendars   = $db->table_name($this->rc->config->get('db_table_calendars', $this->db_calendars));
         $this->db_attachments = $db->table_name($this->rc->config->get('db_table_attachments', $this->db_attachments));
 
         $this->_read_calendars();
     }
 
     /**
      * Read available calendars for the current user and store them internally
      */
     private function _read_calendars()
     {
         $hidden = array_filter(explode(',', $this->rc->config->get('hidden_calendars', '')));
 
         if (!empty($this->rc->user->ID)) {
             $calendar_ids = array();
             $result = $this->rc->db->query(
                 "SELECT *, `calendar_id` AS id FROM `{$this->db_calendars}`"
                 . " WHERE `user_id` = ?"
                 . " ORDER BY `name`",
                 $this->rc->user->ID
             );
 
             while ($result && ($arr = $this->rc->db->fetch_assoc($result))) {
                 $arr['showalarms'] = intval($arr['showalarms']);
                 $arr['active']     = !in_array($arr['id'], $hidden);
                 $arr['name']       = html::quote($arr['name']);
                 $arr['listname']   = html::quote($arr['name']);
                 $arr['rights']     = 'lrswikxteav';
                 $arr['editable']  = true;
 
                 $this->calendars[$arr['calendar_id']] = $arr;
                 $calendar_ids[] = $this->rc->db->quote($arr['calendar_id']);
             }
 
             $this->calendar_ids = join(',', $calendar_ids);
         }
     }
 
     /**
      * Get a list of available calendars from this source
      *
      * @param integer Bitmask defining filter criterias
      *
      * @return array List of calendars
      */
     public function list_calendars($filter = 0)
     {
         // attempt to create a default calendar for this user
         if (empty($this->calendars)) {
             if ($this->create_calendar(array('name' => 'Default', 'color' => 'cc0000', 'showalarms' => true))) {
                 $this->_read_calendars();
             }
         }
 
         $calendars = $this->calendars;
 
         // filter active calendars
         if ($filter & self::FILTER_ACTIVE) {
             foreach ($calendars as $idx => $cal) {
                 if (!$cal['active']) {
                     unset($calendars[$idx]);
                 }
             }
         }
 
         // 'personal' is unsupported in this driver
 
         // append the virtual birthdays calendar
         if ($this->rc->config->get('calendar_contact_birthdays', false)) {
             $prefs  = $this->rc->config->get('birthday_calendar', array('color' => '87CEFA'));
             $hidden = array_filter(explode(',', $this->rc->config->get('hidden_calendars', '')));
             $id     = self::BIRTHDAY_CALENDAR_ID;
 
-            if (!$active || !in_array($id, $hidden)) {
+            if (empty($active) || !in_array($id, $hidden)) {
                 $calendars[$id] = array(
                     'id'         => $id,
                     'name'       => $this->cal->gettext('birthdays'),
                     'listname'   => $this->cal->gettext('birthdays'),
                     'color'      => $prefs['color'],
                     'showalarms' => (bool)$this->rc->config->get('calendar_birthdays_alarm_type'),
                     'active'     => !in_array($id, $hidden),
                     'group'      => 'x-birthdays',
                     'editable'  => false,
                     'default'    => false,
                     'children'   => false,
                 );
             }
         }
 
         return $calendars;
     }
 
     /**
      * Create a new calendar assigned to the current user
      *
      * @param array Hash array with calendar properties
      *    name: Calendar name
      *   color: The color of the calendar
      * @return mixed ID of the calendar on success, False on error
      */
     public function create_calendar($prop)
     {
         $result = $this->rc->db->query(
             "INSERT INTO `{$this->db_calendars}`"
             . " (`user_id`, `name`, `color`, `showalarms`)"
             . " VALUES (?, ?, ?, ?)",
             $this->rc->user->ID,
             $prop['name'],
             strval($prop['color']),
             $prop['showalarms'] ? 1 : 0
         );
 
         if ($result) {
             return $this->rc->db->insert_id($this->db_calendars);
         }
 
         return false;
     }
 
     /**
      * Update properties of an existing calendar
      *
      * @see calendar_driver::edit_calendar()
      */
     public function edit_calendar($prop)
     {
         // birthday calendar properties are saved in user prefs
         if ($prop['id'] == self::BIRTHDAY_CALENDAR_ID) {
             $prefs['birthday_calendar'] = $this->rc->config->get('birthday_calendar', array('color' => '87CEFA'));
             if (isset($prop['color'])) {
                 $prefs['birthday_calendar']['color'] = $prop['color'];
             }
             if (isset($prop['showalarms'])) {
                 $prefs['calendar_birthdays_alarm_type'] = $prop['showalarms'] ? $this->alarm_types[0] : '';
             }
 
             $this->rc->user->save_prefs($prefs);
             return true;
         }
 
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_calendars}`"
             . " SET `name` = ?, `color` = ?, `showalarms` = ?"
             . " WHERE `calendar_id` = ? AND `user_id` = ?",
             $prop['name'],
             strval($prop['color']),
             $prop['showalarms'] ? 1 : 0,
             $prop['id'],
             $this->rc->user->ID
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Set active/subscribed state of a calendar
      * Save a list of hidden calendars in user prefs
      *
      * @see calendar_driver::subscribe_calendar()
      */
     public function subscribe_calendar($prop)
     {
         $hidden = array_flip(explode(',', $this->rc->config->get('hidden_calendars', '')));
 
         if ($prop['active']) {
             unset($hidden[$prop['id']]);
         }
         else {
             $hidden[$prop['id']] = 1;
         }
 
         return $this->rc->user->save_prefs(array('hidden_calendars' => join(',', array_keys($hidden))));
     }
 
     /**
      * Delete the given calendar with all its contents
      *
      * @see calendar_driver::delete_calendar()
      */
     public function delete_calendar($prop)
     {
         if (!$this->calendars[$prop['id']]) {
             return false;
         }
 
         // events and attachments will be deleted by foreign key cascade
 
         $query = $this->rc->db->query(
             "DELETE FROM `{$this->db_calendars}` WHERE `calendar_id` = ? AND `user_id` = ?",
             $prop['id'],
             $this->rc->user->ID
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Search for shared or otherwise not listed calendars the user has access
      *
      * @param string Search string
      * @param string Section/source to search
      *
      * @return array List of calendars
      */
     public function search_calendars($query, $source)
     {
         // not implemented
         return array();
     }
 
     /**
      * Add a single event to the database
      *
      * @param array Hash array with event properties
      * @see calendar_driver::new_event()
      */
     public function new_event($event)
     {
         if (!$this->validate($event)) {
             return false;
         }
 
         if (!empty($this->calendars)) {
             if ($event['calendar'] && !$this->calendars[$event['calendar']]) {
                 return false;
             }
 
             if (!$event['calendar']) {
                 $event['calendar'] = reset(array_keys($this->calendars));
             }
 
             if ($event_id = $this->_insert_event($event)) {
                 $this->_update_recurring($event);
             }
 
             return $event_id;
         }
 
         return false;
     }
 
     /**
      *
      */
     private function _insert_event(&$event)
     {
         $event = $this->_save_preprocess($event);
         $now   = $this->rc->db->now();
 
         $this->rc->db->query(
             "INSERT INTO `{$this->db_events}`"
             . " (`calendar_id`, `created`, `changed`, `uid`, `recurrence_id`, `instance`,"
                 . " `isexception`, `start`, `end`, `all_day`, `recurrence`, `title`, `description`,"
                 . " `location`, `categories`, `url`, `free_busy`, `priority`, `sensitivity`,"
                 . " `status`, `attendees`, `alarms`, `notifyat`)"
             . " VALUES (?, $now, $now, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)",
             $event['calendar'],
             strval($event['uid']),
             intval($event['recurrence_id']),
             strval($event['_instance']),
             intval($event['isexception']),
             $event['start']->format(self::DB_DATE_FORMAT),
             $event['end']->format(self::DB_DATE_FORMAT),
             intval($event['all_day']),
             $event['_recurrence'],
             strval($event['title']),
             strval($event['description']),
             strval($event['location']),
             join(',', (array)$event['categories']),
             strval($event['url']),
             intval($event['free_busy']),
             intval($event['priority']),
             intval($event['sensitivity']),
             strval($event['status']),
             $event['attendees'],
             $event['alarms'],
             $event['notifyat']
         );
 
         $event_id = $this->rc->db->insert_id($this->db_events);
 
         if ($event_id) {
             $event['id'] = $event_id;
 
             // add attachments
             if (!empty($event['attachments'])) {
                 foreach ($event['attachments'] as $attachment) {
                     $this->add_attachment($attachment, $event_id);
                     unset($attachment);
                 }
             }
 
             return $event_id;
         }
 
         return false;
     }
 
     /**
      * Update an event entry with the given data
      *
      * @param array Hash array with event properties
      * @see calendar_driver::edit_event()
      */
     public function edit_event($event)
     {
         if (!empty($this->calendars)) {
             $update_master    = false;
             $update_recurring = true;
 
             $old = $this->get_event($event);
             $ret = true;
 
             // check if update affects scheduling and update attendee status accordingly
             $reschedule = $this->_check_scheduling($event, $old, true);
 
             // increment sequence number
             if (empty($event['sequence']) && $reschedule) {
                 $event['sequence'] = max($event['sequence'], $old['sequence']) + 1;
             }
 
             // modify a recurring event, check submitted savemode to do the right things
             if ($old['recurrence'] || $old['recurrence_id']) {
                 $master = $old['recurrence_id'] ? $this->get_event(array('id' => $old['recurrence_id'])) : $old;
 
                 // keep saved exceptions (not submitted by the client)
                 if ($old['recurrence']['EXDATE']) {
                     $event['recurrence']['EXDATE'] = $old['recurrence']['EXDATE'];
                 }
 
                 switch ($event['_savemode']) {
                 case 'new':
                     $event['uid'] = $this->cal->generate_uid();
                     return $this->new_event($event);
 
                 case 'current':
                     // save as exception
                     $event['isexception'] = 1;
                     $update_recurring     = false;
 
                     // set exception to first instance (= master)
                     if ($event['id'] == $master['id']) {
                         $event += $old;
                         $event['recurrence_id'] = $master['id'];
                         $event['_instance']     = libcalendaring::recurrence_instance_identifier($old, $master['allday']);
                         $event['isexception']   = 1;
                         $event_id = $this->_insert_event($event);
 
                         return $event_id;
                     }
                     break;
 
                 case 'future':
                     if ($master['id'] != $event['id']) {
                         // set until-date on master event, then save this instance as new recurring event
                         $master['recurrence']['UNTIL'] = clone $event['start'];
                         $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
                         unset($master['recurrence']['COUNT']);
                         $update_master = true;
 
                         // if recurrence COUNT, update value to the correct number of future occurences
                         if ($event['recurrence']['COUNT']) {
                             $fromdate = clone $event['start'];
                             $fromdate->setTimezone($this->server_timezone);
 
                             $query = $this->rc->db->query(
                                 "SELECT `event_id` FROM `{$this->db_events}`"
                                 . " WHERE `calendar_id` IN ({$this->calendar_ids})"
                                     . " AND `start` >= ? AND `recurrence_id` = ?",
                                 $fromdate->format(self::DB_DATE_FORMAT),
                                 $master['id']
                             );
 
                             if ($count = $this->rc->db->num_rows($query)) {
                                 $event['recurrence']['COUNT'] = $count;
                             }
                         }
 
                         $update_recurring       = true;
                         $event['recurrence_id'] = 0;
                         $event['isexception']   = 0;
                         $event['_instance']     = '';
                         break;
                     }
                     // else: 'future' == 'all' if modifying the master event
 
                 default:  // 'all' is default
                     $event['id']            = $master['id'];
                     $event['recurrence_id'] = 0;
 
                     // use start date from master but try to be smart on time or duration changes
                     $old_start_date = $old['start']->format('Y-m-d');
                     $old_start_time = $old['allday'] ? '' : $old['start']->format('H:i');
                     $old_duration   = $old['end']->format('U') - $old['start']->format('U');
 
                     $new_start_date = $event['start']->format('Y-m-d');
                     $new_start_time = $event['allday'] ? '' : $event['start']->format('H:i');
                     $new_duration   = $event['end']->format('U') - $event['start']->format('U');
 
                     $diff = $old_start_date != $new_start_date || $old_start_time != $new_start_time || $old_duration != $new_duration;
                     $date_shift = $old['start']->diff($event['start']);
 
                     // shifted or resized
                     if ($diff && ($old_start_date == $new_start_date || $old_duration == $new_duration)) {
                         $event['start'] = $master['start']->add($old['start']->diff($event['start']));
                         $event['end']   = clone $event['start'];
                         $event['end']->add(new DateInterval('PT'.$new_duration.'S'));
                     }
                     // dates did not change, use the ones from master
                     else if ($new_start_date . $new_start_time == $old_start_date . $old_start_time) {
                         $event['start'] = $master['start'];
                         $event['end']   = $master['end'];
                     }
 
                     // adjust recurrence-id when start changed and therefore the entire recurrence chain changes
                     if (is_array($event['recurrence'])
                         && ($old_start_date != $new_start_date || $old_start_time != $new_start_time)
                         && ($exceptions = $this->_load_exceptions($old))
                     ) {
                         $recurrence_id_format = libcalendaring::recurrence_id_format($event);
 
                         foreach ($exceptions as $exception) {
                             $recurrence_id = rcube_utils::anytodatetime($exception['_instance'], $old['start']->getTimezone());
                             if (is_a($recurrence_id, 'DateTime')) {
                                 $recurrence_id->add($date_shift);
                                 $exception['_instance'] = $recurrence_id->format($recurrence_id_format);
                                 $this->_update_event($exception, false);
                             }
                         }
                     }
 
                     $ret = $event['id'];  // return master ID
                     break;
                 }
             }
 
             $success = $this->_update_event($event, $update_recurring);
 
             if ($success && $update_master) {
                 $this->_update_event($master, true);
             }
 
             return $success ? $ret : false;
         }
 
         return false;
     }
 
     /**
      * Extended event editing with possible changes to the argument
      *
      * @param array  Hash array with event properties
      * @param string New participant status
      * @param array  List of hash arrays with updated attendees
      *
      * @return boolean True on success, False on error
      */
     public function edit_rsvp(&$event, $status, $attendees)
     {
         $update_event = $event;
 
         // apply changes to master (and all exceptions)
         if ($event['_savemode'] == 'all' && $event['recurrence_id']) {
             $update_event = $this->get_event(array('id' => $event['recurrence_id']));
             $update_event['_savemode'] = $event['_savemode'];
             calendar::merge_attendee_data($update_event, $attendees);
         }
 
         if ($ret = $this->update_attendees($update_event, $attendees)) {
             // replace $event with effectively updated event (for iTip reply)
             if ($ret !== true && $ret != $update_event['id'] && ($new_event = $this->get_event(array('id' => $ret)))) {
                 $event = $new_event;
             }
             else {
                 $event = $update_event;
             }
         }
 
         return $ret;
     }
 
     /**
      * Update the participant status for the given attendees
      *
      * @see calendar_driver::update_attendees()
      */
     public function update_attendees(&$event, $attendees)
     {
         $success = $this->edit_event($event, true);
 
         // apply attendee updates to recurrence exceptions too
         if ($success && $event['_savemode'] == 'all'
             && !empty($event['recurrence'])
             && empty($event['recurrence_id'])
             && ($exceptions = $this->_load_exceptions($event))
         ) {
             foreach ($exceptions as $exception) {
                 calendar::merge_attendee_data($exception, $attendees);
                 $this->_update_event($exception, false);
             }
         }
 
         return $success;
     }
 
     /**
      * Determine whether the current change affects scheduling and reset attendee status accordingly
      */
     private function _check_scheduling(&$event, $old, $update = true)
     {
         // skip this check when importing iCal/iTip events
         if (isset($event['sequence']) || !empty($event['_method'])) {
             return false;
         }
 
         $reschedule = false;
 
         // iterate through the list of properties considered 'significant' for scheduling
         foreach (self::$scheduling_properties as $prop) {
             $a = $old[$prop];
             $b = $event[$prop];
 
             if ($event['allday'] && ($prop == 'start' || $prop == 'end') && $a instanceof DateTime && $b instanceof DateTime) {
                 $a = $a->format('Y-m-d');
                 $b = $b->format('Y-m-d');
             }
 
             if ($prop == 'recurrence' && is_array($a) && is_array($b)) {
                 unset($a['EXCEPTIONS'], $b['EXCEPTIONS']);
                 $a = array_filter($a);
                 $b = array_filter($b);
 
                 // advanced rrule comparison: no rescheduling if series was shortened
                 if ($a['COUNT'] && $b['COUNT'] && $b['COUNT'] < $a['COUNT']) {
                     unset($a['COUNT'], $b['COUNT']);
                 }
                 else if ($a['UNTIL'] && $b['UNTIL'] && $b['UNTIL'] < $a['UNTIL']) {
                     unset($a['UNTIL'], $b['UNTIL']);
                 }
             }
 
             if ($a != $b) {
                 $reschedule = true;
                 break;
             }
         }
 
         // reset all attendee status to needs-action (#4360)
         if ($update && $reschedule && is_array($event['attendees'])) {
             $is_organizer = false;
             $emails       = $this->cal->get_user_emails();
             $attendees    = $event['attendees'];
 
             foreach ($attendees as $i => $attendee) {
                 if ($attendee['role'] == 'ORGANIZER' && $attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                     $is_organizer = true;
                 }
                 else if ($attendee['role'] != 'ORGANIZER'
                     && $attendee['role'] != 'NON-PARTICIPANT'
                     && $attendee['status'] != 'DELEGATED'
                 ) {
                     $attendees[$i]['status'] = 'NEEDS-ACTION';
                     $attendees[$i]['rsvp'] = true;
                 }
             }
 
             // update attendees only if I'm the organizer
             if ($is_organizer || ($event['organizer'] && in_array(strtolower($event['organizer']['email']), $emails))) {
                 $event['attendees'] = $attendees;
             }
         }
 
         return $reschedule;
     }
 
     /**
      * Convert save data to be used in SQL statements
      */
     private function _save_preprocess($event)
     {
         // shift dates to server's timezone (except for all-day events)
         if (!$event['allday']) {
             $event['start'] = clone $event['start'];
             $event['start']->setTimezone($this->server_timezone);
             $event['end'] = clone $event['end'];
             $event['end']->setTimezone($this->server_timezone);
         }
 
         // compose vcalendar-style recurrencue rule from structured data
         $rrule = $event['recurrence'] ? libcalendaring::to_rrule($event['recurrence']) : '';
 
         $event['_recurrence'] = rtrim($rrule, ';');
         $event['free_busy']   = intval($this->free_busy_map[strtolower($event['free_busy'])]);
         $event['sensitivity'] = intval($this->sensitivity_map[strtolower($event['sensitivity'])]);
 
         if ($event['free_busy'] == 'tentative') {
             $event['status'] = 'TENTATIVE';
         }
 
         if (isset($event['allday'])) {
             $event['all_day'] = $event['allday'] ? 1 : 0;
         }
 
         // compute absolute time to notify the user
         $event['notifyat'] = $this->_get_notification($event);
 
         if (is_array($event['valarms'])) {
             $event['alarms'] = $this->serialize_alarms($event['valarms']);
         }
 
         // process event attendees
         if (!empty($event['attendees'])) {
             $event['attendees'] = json_encode((array)$event['attendees']);
         }
         else {
             $event['attendees'] = '';
         }
 
         return $event;
     }
 
     /**
      * Compute absolute time to notify the user
      */
     private function _get_notification($event)
     {
         if ($event['valarms'] && $event['start'] > new DateTime()) {
             $alarm = libcalendaring::get_next_alarm($event);
 
             if ($alarm['time'] && in_array($alarm['action'], $this->alarm_types)) {
                 return date('Y-m-d H:i:s', $alarm['time']);
             }
         }
     }
 
     /**
      * Save the given event record to database
      *
      * @param array Event data
      * @param boolean True if recurring events instances should be updated, too
      */
     private function _update_event($event, $update_recurring = true)
     {
         $event    = $this->_save_preprocess($event);
         $sql_args = array();
         $set_cols = array('start', 'end', 'all_day', 'recurrence_id', 'isexception', 'sequence',
             'title', 'description', 'location', 'categories', 'url', 'free_busy', 'priority',
             'sensitivity', 'status', 'attendees', 'alarms', 'notifyat'
         );
 
         foreach ($set_cols as $col) {
             if (is_object($event[$col]) && is_a($event[$col], 'DateTime')) {
                 $sql_args[$col] = $event[$col]->format(self::DB_DATE_FORMAT);
             }
             else if (is_array($event[$col])) {
                 $sql_args[$col] = join(',', $event[$col]);
             }
             else if (array_key_exists($col, $event)) {
                 $sql_args[$col] = $event[$col];
             }
         }
 
         if ($event['_recurrence']) {
             $sql_args['recurrence'] = $event['_recurrence'];
         }
 
         if ($event['_instance']) {
             $sql_args['instance'] = $event['_instance'];
         }
 
         if ($event['_fromcalendar'] && $event['_fromcalendar'] != $event['calendar']) {
             $sql_args['calendar_id'] = $event['calendar'];
         }
 
         $sql_set = '';
         foreach (array_keys($sql_args) as $col) {
             $sql_set .= ", `$col` = ?";
         }
 
         $sql_args = array_values($sql_args);
         $sql_args[] = $event['id'];
 
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}`"
             . " SET `changed` = " . $this->rc->db->now() . $sql_set
             . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $sql_args
         );
 
         $success = $this->rc->db->affected_rows($query);
 
         // add attachments
         if ($success && !empty($event['attachments'])) {
             foreach ($event['attachments'] as $attachment) {
                 $this->add_attachment($attachment, $event['id']);
                 unset($attachment);
             }
         }
 
         // remove attachments
         if ($success && !empty($event['deleted_attachments'])) {
             foreach ($event['deleted_attachments'] as $attachment) {
                 $this->remove_attachment($attachment, $event['id']);
             }
         }
 
         if ($success) {
             unset($this->cache[$event['id']]);
             if ($update_recurring) {
                 $this->_update_recurring($event);
             }
         }
 
         return $success;
     }
 
     /**
      * Insert "fake" entries for recurring occurences of this event
      */
     private function _update_recurring($event)
     {
         if (empty($this->calendars)) {
             return;
         }
 
         if (!empty($event['recurrence'])) {
             $exdata     = array();
             $exceptions = $this->_load_exceptions($event);
 
             foreach ($exceptions as $exception) {
                 $exdate = substr($exception['_instance'], 0, 8);
                 $exdata[$exdate] = $exception;
             }
         }
 
         // clear existing recurrence copies
         $this->rc->db->query(
             "DELETE FROM `{$this->db_events}`"
             . " WHERE `recurrence_id` = ? AND `isexception` = 0 AND `calendar_id` IN ({$this->calendar_ids})",
             $event['id']
         );
 
         // create new fake entries
         if (!empty($event['recurrence'])) {
             // include library class
             require_once($this->cal->home . '/lib/calendar_recurrence.php');
 
             $recurrence = new calendar_recurrence($this->cal, $event);
             $count = 0;
             $event['allday'] = $event['all_day'];
             $duration = $event['start']->diff($event['end']);
             $recurrence_id_format = libcalendaring::recurrence_id_format($event);
 
             while ($next_start = $recurrence->next_start()) {
                 $instance = $next_start->format($recurrence_id_format);
                 $datestr  = substr($instance, 0, 8);
 
                 // skip exceptions
                 // TODO: merge updated data from master event
                 if ($exdata[$datestr]) {
                     continue;
                 }
 
                 $next_start->setTimezone($this->server_timezone);
                 $next_end = clone $next_start;
                 $next_end->add($duration);
 
                 $notify_at = $this->_get_notification(array(
                         'alarms' => $event['alarms'],
                         'start'  => $next_start,
                         'end'    => $next_end,
                         'status' => $event['status']
                 ));
 
                 $now   = $this->rc->db->now();
                 $query = $this->rc->db->query(
                     "INSERT INTO `{$this->db_events}`"
                     . " (`calendar_id`, `recurrence_id`, `created`, `changed`, `uid`, `instance`, `start`, `end`,"
                         . " `all_day`, `sequence`, `recurrence`, `title`, `description`, `location`, `categories`,"
                         . " `url`, `free_busy`, `priority`, `sensitivity`, `status`, `alarms`, `attendees`, `notifyat`)"
                     . " SELECT `calendar_id`, ?, $now, $now, `uid`, ?, ?, ?,"
                         . " `all_day`, `sequence`, `recurrence`, `title`, `description`, `location`, `categories`,"
                         . " `url`, `free_busy`, `priority`, `sensitivity`, `status`, `alarms`, `attendees`, ?"
                     . " FROM `{$this->db_events}` WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids})",
                     $event['id'],
                     $instance,
                     $next_start->format(self::DB_DATE_FORMAT),
                     $next_end->format(self::DB_DATE_FORMAT),
                     $notify_at,
                     $event['id']
                 );
 
                 if (!$this->rc->db->affected_rows($query)) {
                     break;
                 }
 
                 // stop adding events for inifinite recurrence after 20 years
                 if (++$count > 999 || (!$recurrence->recurEnd && !$recurrence->recurCount && $next_start->format('Y') > date('Y') + 20)) {
                     break;
                 }
             }
 
             // remove all exceptions after recurrence end
             if ($next_end && !empty($exceptions)) {
                 $this->rc->db->query(
                     "DELETE FROM `{$this->db_events}`"
                     . " WHERE `recurrence_id` = ? AND `isexception` = 1 AND `start` > ?"
                         . " AND `calendar_id` IN ({$this->calendar_ids})",
                     $event['id'],
                     $next_end->format(self::DB_DATE_FORMAT)
                 );
             }
         }
     }
 
     /**
      *
      */
     private function _load_exceptions($event, $instance_id = null)
     {
         $sql_add_where = '';
         if (!empty($instance_id)) {
             $sql_add_where = " AND `instance` = ?";
         }
 
         $result = $this->rc->db->query(
             "SELECT * FROM `{$this->db_events}`"
             . " WHERE `recurrence_id` = ? AND `isexception` = 1"
                 . " AND `calendar_id` IN ({$this->calendar_ids})" . $sql_add_where
             . " ORDER BY `instance`, `start`",
             $event['id'],
             $instance_id
         );
 
         $exceptions = array();
         while (($sql_arr = $this->rc->db->fetch_assoc($result)) && $sql_arr['event_id']) {
             $exception = $this->_read_postprocess($sql_arr);
             $instance  = $exception['_instance'] ?: $exception['start']->format($exception['allday'] ? 'Ymd' : 'Ymd\THis');
             $exceptions[$instance] = $exception;
         }
 
         return $exceptions;
     }
 
     /**
      * Move a single event
      *
      * @param array Hash array with event properties
      * @see calendar_driver::move_event()
      */
     public function move_event($event)
     {
         // let edit_event() do all the magic
         return $this->edit_event($event + (array)$this->get_event($event));
     }
 
     /**
      * Resize a single event
      *
      * @param array Hash array with event properties
      * @see calendar_driver::resize_event()
      */
     public function resize_event($event)
     {
         // let edit_event() do all the magic
         return $this->edit_event($event + (array)$this->get_event($event));
     }
 
     /**
      * Remove a single event from the database
      *
      * @param array   Hash array with event properties
      * @param boolean Remove record irreversible (@TODO)
      *
      * @see calendar_driver::remove_event()
      */
     public function remove_event($event, $force = true)
     {
         if (!empty($this->calendars)) {
             $event += (array)$this->get_event($event);
             $master        = $event;
             $update_master = false;
             $savemode      = 'all';
             $ret           = true;
 
             // read master if deleting a recurring event
             if ($event['recurrence'] || $event['recurrence_id']) {
                 $master   = $event['recurrence_id'] ? $this->get_event(array('id' => $event['recurrence_id'])) : $event;
                 $savemode = $event['_savemode'];
             }
 
             switch ($savemode) {
             case 'current':
                 // add exception to master event
                 $master['recurrence']['EXDATE'][] = $event['start'];
                 $update_master = true;
 
                 // just delete this single occurence
                 $query = $this->rc->db->query(
                     "DELETE FROM `{$this->db_events}`"
                     . " WHERE `calendar_id` IN ({$this->calendar_ids}) AND `event_id` = ?",
                     $event['id']
                 );
                 break;
 
             case 'future':
                 if ($master['id'] != $event['id']) {
                     // set until-date on master event
                     $master['recurrence']['UNTIL'] = clone $event['start'];
                     $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
                     unset($master['recurrence']['COUNT']);
                     $update_master = true;
 
                     // delete this and all future instances
                     $fromdate = clone $event['start'];
                     $fromdate->setTimezone($this->server_timezone);
 
                     $query = $this->rc->db->query(
                         "DELETE FROM `{$this->db_events}`"
                         . " WHERE `calendar_id` IN ({$this->calendar_ids}) AND `start` >= ? AND `recurrence_id` = ?",
                         $fromdate->format(self::DB_DATE_FORMAT),
                         $master['id']
                     );
 
                     $ret = $master['id'];
                     break;
                 }
                 // else: future == all if modifying the master event
 
             default:  // 'all' is default
                 $query = $this->rc->db->query(
                     "DELETE FROM `{$this->db_events}`"
                     . " WHERE (`event_id` = ? OR `recurrence_id` = ?) AND `calendar_id` IN ({$this->calendar_ids})",
                     $master['id'],
                     $master['id']
                 );
                 break;
             }
 
             $success = $this->rc->db->affected_rows($query);
 
             if ($success && $update_master) {
                 $this->_update_event($master, true);
             }
 
             return $success ? $ret : false;
         }
 
         return false;
     }
 
     /**
      * Return data of a specific event
      *
      * @param mixed   Hash array with event properties or event UID
      * @param integer Bitmask defining the scope to search events in
      * @param boolean If true, recurrence exceptions shall be added
      *
      * @return array Hash array with event properties
      */
     public function get_event($event, $scope = 0, $full = false)
     {
         $id  = is_array($event) ? ($event['id'] ?: $event['uid']) : $event;
         $cal = is_array($event) ? $event['calendar'] : null;
         $col = is_array($event) && is_numeric($id) ? 'event_id' : 'uid';
 
         if ($this->cache[$id]) {
             return $this->cache[$id];
         }
 
         // get event from the address books birthday calendar
         if ($cal == self::BIRTHDAY_CALENDAR_ID) {
             return $this->get_birthday_event($id);
         }
 
         $where_add = '';
         if (is_array($event) && !$event['id'] && !empty($event['_instance'])) {
             $where_add = " AND e.instance = " . $this->rc->db->quote($event['_instance']);
         }
 
         if ($scope & self::FILTER_ACTIVE) {
             $calendars = $this->calendars;
             foreach ($calendars as $idx => $cal) {
                 if (!$cal['active']) {
                     unset($calendars[$idx]);
                 }
             }
             $cals = join(',', $calendars);
         }
         else {
             $cals = $this->calendar_ids;
         }
 
         $result = $this->rc->db->query(
             "SELECT e.*, (SELECT COUNT(`attachment_id`) FROM `{$this->db_attachments}`"
                 . " WHERE `event_id` = e.event_id OR `event_id` = e.recurrence_id) AS _attachments"
             . " FROM `{$this->db_events}` AS e"
             . " WHERE e.calendar_id IN ($cals) AND e.$col = ?" . $where_add,
             $id
         );
 
         if ($result && ($sql_arr = $this->rc->db->fetch_assoc($result)) && $sql_arr['event_id']) {
             $event = $this->_read_postprocess($sql_arr);
 
             // also load recurrence exceptions
             if (!empty($event['recurrence']) && $full) {
                 $event['recurrence']['EXCEPTIONS'] = array_values($this->_load_exceptions($event));
             }
 
             $this->cache[$id] = $event;
 
             return $this->cache[$id];
         }
 
         return false;
     }
 
     /**
      * Get event data
      *
      * @see calendar_driver::load_events()
      */
     public function load_events($start, $end, $query = null, $calendars = null, $virtual = 1, $modifiedsince = null)
     {
         if (empty($calendars)) {
             $calendars = array_keys($this->calendars);
         }
         else if (!is_array($calendars)) {
             $calendars = explode(',', strval($calendars));
         }
 
         // only allow to select from calendars of this use
         $calendar_ids = array_map(array($this->rc->db, 'quote'), array_intersect($calendars, array_keys($this->calendars)));
 
         // compose (slow) SQL query for searching
         // FIXME: improve searching using a dedicated col and normalized values
+        $sql_add = '';
         if ($query) {
             foreach (array('title','location','description','categories','attendees') as $col) {
                 $sql_query[] = $this->rc->db->ilike($col, '%'.$query.'%');
             }
-            $sql_add = " AND (" . join(' OR ', $sql_query) . ")";
+            $sql_add .= " AND (" . join(' OR ', $sql_query) . ")";
         }
 
         if (!$virtual) {
             $sql_add .= " AND e.recurrence_id = 0";
         }
 
         if ($modifiedsince) {
             $sql_add .= " AND e.changed >= " . $this->rc->db->quote(date('Y-m-d H:i:s', $modifiedsince));
         }
 
         $events = array();
         if (!empty($calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT e.*, (SELECT COUNT(`attachment_id`) FROM `{$this->db_attachments}`"
                     . " WHERE `event_id` = e.event_id OR `event_id` = e.recurrence_id) AS _attachments"
                 . " FROM `{$this->db_events}` e"
                 . " WHERE e.calendar_id IN (" . join(',', $calendar_ids) . ")"
                     . " AND e.start <= " . $this->rc->db->fromunixtime($end)
                     . " AND e.end >= " . $this->rc->db->fromunixtime($start)
                     . $sql_add
             );
 
             while ($result && ($sql_arr = $this->rc->db->fetch_assoc($result))) {
                 $event = $this->_read_postprocess($sql_arr);
                 $add   = true;
 
                 if (!empty($event['recurrence']) && !$event['recurrence_id']) {
                     // load recurrence exceptions (i.e. for export)
                     if (!$virtual) {
                         $event['recurrence']['EXCEPTIONS'] = $this->_load_exceptions($event);
                     }
                     // check for exception on first instance
                     else {
                         $instance   = libcalendaring::recurrence_instance_identifier($event);
                         $exceptions = $this->_load_exceptions($event, $instance);
 
                         if ($exceptions && is_array($exceptions[$instance])) {
                             $event = $exceptions[$instance];
                             $add   = false;
                         }
                     }
                 }
 
                 if ($add) {
                     $events[] = $event;
                 }
             }
         }
 
         // add events from the address books birthday calendar
         if (in_array(self::BIRTHDAY_CALENDAR_ID, $calendars) && empty($query)) {
-            $events = array_merge($events, $this->load_birthday_events($start, $end, $search, $modifiedsince));
+            $events = array_merge($events, $this->load_birthday_events($start, $end, null, $modifiedsince));
         }
 
         return $events;
     }
 
     /**
      * Get number of events in the given calendar
      *
      * @param  mixed   List of calendar IDs to count events (either as array or comma-separated string)
      * @param  integer Date range start (unix timestamp)
      * @param  integer Date range end (unix timestamp)
      *
      * @return array   Hash array with counts grouped by calendar ID
      */
     public function count_events($calendars, $start, $end = null)
     {
         // not implemented
         return array();
     }
 
     /**
      * Convert sql record into a rcube style event object
      */
     private function _read_postprocess($event)
     {
         $free_busy_map   = array_flip($this->free_busy_map);
         $sensitivity_map = array_flip($this->sensitivity_map);
 
         $event['id']            = $event['event_id'];
         $event['start']         = new DateTime($event['start']);
         $event['end']           = new DateTime($event['end']);
         $event['allday']        = intval($event['all_day']);
         $event['created']       = new DateTime($event['created']);
         $event['changed']       = new DateTime($event['changed']);
         $event['free_busy']     = $free_busy_map[$event['free_busy']];
         $event['sensitivity']   = $sensitivity_map[$event['sensitivity']];
         $event['calendar']      = $event['calendar_id'];
         $event['recurrence_id'] = intval($event['recurrence_id']);
         $event['isexception']   = intval($event['isexception']);
 
         // parse recurrence rule
         if ($event['recurrence'] && preg_match_all('/([A-Z]+)=([^;]+);?/', $event['recurrence'], $m, PREG_SET_ORDER)) {
             $event['recurrence'] = array();
             foreach ($m as $rr) {
                 if (is_numeric($rr[2])) {
                     $rr[2] = intval($rr[2]);
                 }
                 else if ($rr[1] == 'UNTIL') {
                     $rr[2] = date_create($rr[2]);
                 }
                 else if ($rr[1] == 'RDATE') {
                     $rr[2] = array_map('date_create', explode(',', $rr[2]));
                 }
                 else if ($rr[1] == 'EXDATE') {
                     $rr[2] = array_map('date_create', explode(',', $rr[2]));
                 }
 
                 $event['recurrence'][$rr[1]] = $rr[2];
             }
         }
 
         if ($event['recurrence_id']) {
             libcalendaring::identify_recurrence_instance($event);
         }
 
         if (strlen($event['instance'])) {
             $event['_instance'] = $event['instance'];
 
             if (empty($event['recurrence_id'])) {
                 $event['recurrence_date'] = rcube_utils::anytodatetime($event['_instance'], $event['start']->getTimezone());
             }
         }
 
         if ($event['_attachments'] > 0) {
             $event['attachments'] = (array)$this->list_attachments($event);
         }
 
         // decode serialized event attendees
         if (strlen($event['attendees'])) {
             $event['attendees'] = $this->unserialize_attendees($event['attendees']);
         }
         else {
             $event['attendees'] = array();
         }
 
         // decode serialized alarms
         if ($event['alarms']) {
             $event['valarms'] = $this->unserialize_alarms($event['alarms']);
         }
 
         unset($event['event_id'], $event['calendar_id'], $event['notifyat'], $event['all_day'], $event['instance'], $event['_attachments']);
 
         return $event;
     }
 
     /**
      * Get a list of pending alarms to be displayed to the user
      *
      * @see calendar_driver::pending_alarms()
      */
     public function pending_alarms($time, $calendars = null)
     {
         if (empty($calendars)) {
             $calendars = array_keys($this->calendars);
         }
         else if (!is_array($calendars)) {
             $calendars = explode(',', (array) $calendars);
         }
 
         // only allow to select from calendars with activated alarms
         $calendar_ids = array();
         foreach ($calendars as $cid) {
             if ($this->calendars[$cid] && $this->calendars[$cid]['showalarms']) {
                 $calendar_ids[] = $cid;
             }
         }
 
         $calendar_ids = array_map(array($this->rc->db, 'quote'), $calendar_ids);
         $alarms       = array();
 
         if (!empty($calendar_ids)) {
             $stime  = $this->rc->db->fromunixtime($time);
             $result = $this->rc->db->query(
                 "SELECT * FROM `{$this->db_events}`"
                 . " WHERE `calendar_id` IN (" . join(',', $calendar_ids) . ")"
                 . " AND `notifyat` <= $stime AND `end` > $stime"
             );
 
             while ($event = $this->rc->db->fetch_assoc($result)) {
                 $alarms[] = $this->_read_postprocess($event);
             }
         }
 
         return $alarms;
     }
 
     /**
      * Feedback after showing/sending an alarm notification
      *
      * @see calendar_driver::dismiss_alarm()
      */
     public function dismiss_alarm($event_id, $snooze = 0)
     {
         // set new notifyat time or unset if not snoozed
         $notify_at = $snooze > 0 ? date(self::DB_DATE_FORMAT, time() + $snooze) : null;
 
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}`"
             . " SET `changed` = " . $this->rc->db->now() . ", `notifyat` = ?"
             . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $notify_at,
             $event_id
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Save an attachment related to the given event
      */
     private function add_attachment($attachment, $event_id)
     {
         if (isset($attachment['data'])) {
             $data = $attachment['data'];
         }
         else if (!empty($attachment['path'])) {
             $data = file_get_contents($attachment['path']);
         }
         else {
             return false;
         }
 
         $query = $this->rc->db->query(
             "INSERT INTO `{$this->db_attachments}`"
             . " (`event_id`, `filename`, `mimetype`, `size`, `data`)"
             . " VALUES (?, ?, ?, ?, ?)",
             $event_id,
             $attachment['name'],
             $attachment['mimetype'],
             strlen($data),
             base64_encode($data)
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Remove a specific attachment from the given event
      */
     private function remove_attachment($attachment_id, $event_id)
     {
         $query = $this->rc->db->query(
             "DELETE FROM `{$this->db_attachments}`"
             . " WHERE `attachment_id` = ? AND `event_id` IN ("
                 . "SELECT `event_id` FROM `{$this->db_events}`"
                 . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))",
             $attachment_id,
             $event_id
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * List attachments of specified event
      */
     public function list_attachments($event)
     {
         $attachments = array();
 
         if (!empty($this->calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT `attachment_id` AS id, `filename` AS name, `mimetype`, `size`"
                 . " FROM `{$this->db_attachments}`"
                 . " WHERE `event_id` IN ("
                     . "SELECT `event_id` FROM `{$this->db_events}`"
                     . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))"
                 . " ORDER BY `filename`",
                 $event['recurrence_id'] ? $event['recurrence_id'] : $event['event_id']
             );
 
             while ($arr = $this->rc->db->fetch_assoc($result)) {
                 $attachments[] = $arr;
             }
         }
 
         return $attachments;
     }
 
     /**
      * Get attachment properties
      */
     public function get_attachment($id, $event)
     {
         if (!empty($this->calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT `attachment_id` AS id, `filename` AS name, `mimetype`, `size` "
                 . " FROM `{$this->db_attachments}`"
                 . " WHERE `attachment_id` = ? AND `event_id` IN ("
                     . "SELECT `event_id` FROM `{$this->db_events}`"
                     . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))",
                 $id,
                 $event['recurrence_id'] ? $event['recurrence_id'] : $event['id']
             );
 
             if ($result && ($arr = $this->rc->db->fetch_assoc($result))) {
                 return $arr;
             }
         }
     }
 
     /**
      * Get attachment body
      */
     public function get_attachment_body($id, $event)
     {
         if (!empty($this->calendar_ids)) {
             $result = $this->rc->db->query(
                 "SELECT `data` FROM `{$this->db_attachments}`"
                 . " WHERE `attachment_id` = ? AND `event_id` IN ("
                     . "SELECT `event_id` FROM `{$this->db_events}`"
                     . " WHERE `event_id` = ? AND `calendar_id` IN ({$this->calendar_ids}))",
                 $id,
                 $event['id']
             );
 
             if ($arr = $this->rc->db->fetch_assoc($result)) {
                 return base64_decode($arr['data']);
             }
         }
     }
 
     /**
      * Remove the given category
      */
     public function remove_category($name)
     {
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}` SET `categories` = ''"
             . " WHERE `categories` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $name
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Update/replace a category
      */
     public function replace_category($oldname, $name, $color)
     {
         $query = $this->rc->db->query(
             "UPDATE `{$this->db_events}` SET `categories` = ?"
             . " WHERE `categories` = ? AND `calendar_id` IN ({$this->calendar_ids})",
             $name,
             $oldname
         );
 
         return $this->rc->db->affected_rows($query);
     }
 
     /**
      * Helper method to serialize the list of alarms into a string
      */
     private function serialize_alarms($valarms)
     {
         foreach ((array)$valarms as $i => $alarm) {
             if ($alarm['trigger'] instanceof DateTime) {
                 $valarms[$i]['trigger'] = '@' . $alarm['trigger']->format('c');
             }
         }
 
         return $valarms ? json_encode($valarms) : null;
     }
 
     /**
      * Helper method to decode a serialized list of alarms
      */
     private function unserialize_alarms($alarms)
     {
         // decode json serialized alarms
         if ($alarms && $alarms[0] == '[') {
             $valarms = json_decode($alarms, true);
             foreach ($valarms as $i => $alarm) {
                 if ($alarm['trigger'][0] == '@') {
                     try {
                         $valarms[$i]['trigger'] = new DateTime(substr($alarm['trigger'], 1));
                     }
                     catch (Exception $e) {
                         unset($valarms[$i]);
                     }
                 }
             }
         }
         // convert legacy alarms data
         else if (strlen($alarms)) {
             list($trigger, $action) = explode(':', $alarms, 2);
             if ($trigger = libcalendaring::parse_alarm_value($trigger)) {
                 $valarms = array(array('action' => $action, 'trigger' => $trigger[3] ?: $trigger[0]));
             }
         }
 
         return $valarms;
     }
 
     /**
      * Helper method to decode the attendees list from string
      */
     private function unserialize_attendees($s_attendees)
     {
         $attendees = array();
 
         // decode json serialized string
         if ($s_attendees[0] == '[') {
             $attendees = json_decode($s_attendees, true);
         }
         // decode the old serialization format
         else {
             foreach (explode("\n", $s_attendees) as $line) {
                 $att = array();
                 foreach (rcube_utils::explode_quoted_string(';', $line) as $prop) {
                     list($key, $value) = explode("=", $prop);
                     $att[strtolower($key)] = stripslashes(trim($value, '""'));
                 }
                 $attendees[] = $att;
             }
         }
 
         return $attendees;
     }
 }
diff --git a/plugins/calendar/drivers/ldap/resources_driver_ldap.php b/plugins/calendar/drivers/ldap/resources_driver_ldap.php
index bd2d610c..0be41261 100644
--- a/plugins/calendar/drivers/ldap/resources_driver_ldap.php
+++ b/plugins/calendar/drivers/ldap/resources_driver_ldap.php
@@ -1,154 +1,157 @@
 <?php
 
 /**
  * LDAP-based resource directory class using rcube_ldap functionality
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 /**
  * LDAP-based resource directory implementation
  */
 class resources_driver_ldap extends resources_driver
 {
     private $rc;
     private $ldap;
 
     /**
      * Default constructor
      */
     function __construct($cal)
     {
         $this->cal = $cal;
         $this->rc = $cal->rc;
     }
 
     /**
      * Fetch resource objects to be displayed for booking
      *
-     * @param  string  Search query (optional)
-     * @return array  List of resource records available for booking
+     * @param string $query Search query (optional)
+     * @param int    $num   Max size of the result
+     *
+     * @return array List of resource records available for booking
      */
     public function load_resources($query = null, $num = 5000)
     {
-      if (!($ldap = $this->connect())) {
-        return array();
-      }
-
-      // TODO: apply paging
-      $ldap->set_pagesize($num);
-
-      if (isset($query)) {
-        $results = $ldap->search('*', $query, 0, true, true);
-      }
-      else {
-        $results = $ldap->list_records();
-      }
-
-      if ($results instanceof ArrayAccess) {
-        foreach ($results as $i => $rec) {
-          $results[$i] = $this->decode_resource($rec);
+        if (!($ldap = $this->connect())) {
+            return [];
+        }
+
+        // TODO: apply paging
+        $ldap->set_pagesize($num);
+
+        if (isset($query)) {
+            $results = $ldap->search('*', $query, 0, true, true);
+        }
+        else {
+            $results = $ldap->list_records();
         }
-      }
 
-      return $results;
+        if ($results instanceof ArrayAccess) {
+            foreach ($results as $i => $rec) {
+                $results[$i] = $this->decode_resource($rec);
+            }
+        }
+
+        return $results;
     }
 
     /**
      * Return properties of a single resource
      *
-     * @param string  Unique resource identifier
+     * @param string $id Unique resource identifier
+     *
      * @return array Resource object as hash array
      */
     public function get_resource($dn)
     {
-      $rec = null;
+        $rec = null;
 
-      if ($ldap = $this->connect()) {
-        $rec = $ldap->get_record(rcube_ldap::dn_encode($dn), true);
+        if ($ldap = $this->connect()) {
+            $rec = $ldap->get_record(rcube_ldap::dn_encode($dn), true);
 
-        if (!empty($rec)) {
-          $rec = $this->decode_resource($rec);
+            if (!empty($rec)) {
+                $rec = $this->decode_resource($rec);
+            }
         }
-      }
 
-      return $rec;
+        return $rec;
     }
 
     /**
      * Return properties of a resource owner
      *
-     * @param string  Owner identifier
-     * @return array  Resource object as hash array
+     * @param string $dn Owner identifier
+     *
+     * @return array Resource object as hash array
      */
     public function get_resource_owner($dn)
     {
-      $owner = null;
+        $owner = null;
 
-      if ($ldap = $this->connect()) {
-        $owner = $ldap->get_record(rcube_ldap::dn_encode($dn), true);
-        $owner['ID'] = rcube_ldap::dn_decode($owner['ID']);
-        unset($owner['_raw_attrib'], $owner['_type']);
-      }
+        if ($ldap = $this->connect()) {
+            $owner = $ldap->get_record(rcube_ldap::dn_encode($dn), true);
+            $owner['ID'] = rcube_ldap::dn_decode($owner['ID']);
+            unset($owner['_raw_attrib'], $owner['_type']);
+        }
 
-      return $owner;
+        return $owner;
     }
 
     /**
      * Extract JSON-serialized attributes
      */
     private function decode_resource($rec)
     {
-      $rec['ID'] = rcube_ldap::dn_decode($rec['ID']);
-
-      $attributes = array();
-
-      foreach ((array) $rec['attributes'] as $sattr) {
-        $sattr = trim($sattr);
-        if ($sattr && $sattr[0] === '{') {
-          $attr = @json_decode($sattr, true);
-          $attributes += $attr;
+        $rec['ID'] = rcube_ldap::dn_decode($rec['ID']);
+
+        $attributes = [];
+
+        foreach ((array) $rec['attributes'] as $sattr) {
+            $sattr = trim($sattr);
+            if (!empty($sattr) && $sattr[0] === '{') {
+                $attr = @json_decode($sattr, true);
+                $attributes += $attr;
+            }
+            else if (!empty($sattr) && empty($rec['description'])) {
+                $rec['description'] = $sattr;
+            }
         }
-        else if ($sattr && empty($rec['description'])) {
-          $rec['description'] = $sattr;
-        }
-      }
 
-      $rec['attributes'] = $attributes;
+        $rec['attributes'] = $attributes;
 
-      // force $rec['members'] to be an array
-      if (!empty($rec['members']) && !is_array($rec['members'])) {
-        $rec['members'] = array($rec['members']);
-      }
+        // force $rec['members'] to be an array
+        if (!empty($rec['members']) && !is_array($rec['members'])) {
+            $rec['members'] = [$rec['members']];
+        }
 
-      // remove unused cruft
-      unset($rec['_raw_attrib']);
+        // remove unused cruft
+        unset($rec['_raw_attrib']);
 
-      return $rec;
+        return $rec;
     }
 
     private function connect()
     {
-      if (!isset($this->ldap)) {
-        $this->ldap = new rcube_ldap($this->rc->config->get('calendar_resources_directory'), true);
-      }
+        if (!isset($this->ldap)) {
+            $this->ldap = new rcube_ldap($this->rc->config->get('calendar_resources_directory'), true);
+        }
 
-      return $this->ldap->ready ? $this->ldap : null;
+        return $this->ldap->ready ? $this->ldap : null;
     }
-
-}
\ No newline at end of file
+}
diff --git a/plugins/calendar/drivers/resources_driver.php b/plugins/calendar/drivers/resources_driver.php
index 4c141cdf..a81a0fff 100644
--- a/plugins/calendar/drivers/resources_driver.php
+++ b/plugins/calendar/drivers/resources_driver.php
@@ -1,112 +1,118 @@
 <?php
 
 /**
  * Resources directory interface definition
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 /**
  * Interface definition for a resources directory driver classe
  */
 abstract class resources_driver
 {
-  protected $cal;
+    protected $cal;
 
-  /**
-   * Default constructor
-   */
-  function __construct($cal)
-  {
-      $this->cal = $cal;
-  }
+    /**
+     * Default constructor
+     */
+    function __construct($cal)
+    {
+        $this->cal = $cal;
+    }
 
-  /**
-   * Fetch resource objects to be displayed for booking
-   *
-   * @param  string  Search query (optional)
-   * @return array  List of resource records available for booking
-   */
-  abstract public function load_resources($query = null);
+    /**
+     * Fetch resource objects to be displayed for booking
+     *
+     * @param string $query Search query (optional)
+     *
+     * @return array List of resource records available for booking
+     */
+    abstract public function load_resources($query = null);
 
-  /**
-   * Return properties of a single resource
-   *
-   * @param string  Unique resource identifier
-   * @return array  Resource object as hash array
-   */
-  abstract public function get_resource($id);
+    /**
+     * Return properties of a single resource
+     *
+     * @param string $id Unique resource identifier
+     *
+     * @return array Resource object as hash array
+     */
+    abstract public function get_resource($id);
 
-  /**
-   * Return properties of a resource owner
-   *
-   * @param string  Owner identifier
-   * @return array  Resource object as hash array
-   */
-  public function get_resource_owner($id)
-  {
-      return null;
-  }
+    /**
+     * Return properties of a resource owner
+     *
+     * @param string $id Owner identifier
+     *
+     * @return array Resource object as hash array
+     */
+    public function get_resource_owner($id)
+    {
+        return null;
+    }
 
-  /**
-   * Get event data to display a resource's calendar
-   *
-   * The default implementation extracts the resource's email address
-   * and fetches free-busy data using the calendar backend driver.
-   *
-   * @param  integer Event's new start (unix timestamp)
-   * @param  integer Event's new end (unix timestamp)
-   * @return array A list of event objects (see calendar_driver specification)
-   */
-  public function get_resource_calendar($id, $start, $end)
-  {
-      $events = array();
-      $rec = $this->get_resource($id);
-      if ($rec && !empty($rec['email']) && $this->cal->driver) {
-          $fbtypemap = array(
-              calendar::FREEBUSY_BUSY => 'busy',
-              calendar::FREEBUSY_TENTATIVE => 'tentative',
-              calendar::FREEBUSY_OOF => 'outofoffice',
-          );
+    /**
+     * Get event data to display a resource's calendar
+     *
+     * The default implementation extracts the resource's email address
+     * and fetches free-busy data using the calendar backend driver.
+     *
+     * @param string $id    Calendar identifier
+     * @param int    $start Event's new start (unix timestamp)
+     * @param int    $end   Event's new end (unix timestamp)
+     *
+     * @return array A list of event objects (see calendar_driver specification)
+     */
+    public function get_resource_calendar($id, $start, $end)
+    {
+        $events = [];
+        $rec    = $this->get_resource($id);
 
-          // if the backend has free-busy information
-          $fblist = $this->cal->driver->get_freebusy_list($rec['email'], $start, $end);
-          if (is_array($fblist)) {
-              foreach ($fblist as $slot) {
-                  list($from, $to, $type) = $slot;
-                  if ($type == calendar::FREEBUSY_FREE || $type == calendar::FREEBUSY_UNKNOWN) {
-                      continue;
-                  }
-                  if ($from < $end && $to > $start) {
-                      $event = array(
-                          'id'     => sha1($id . $from . $to),
-                          'title'  => $rec['name'],
-                          'start'  => new DateTime('@' . $from),
-                          'end'    => new DateTime('@' . $to),
-                          'status' => $fbtypemap[$type],
-                          'calendar' => '_resource',
-                      );
-                      $events[] = $event;
-                  }
-              }
-          }
-      }
+        if ($rec && !empty($rec['email']) && !empty($this->cal->driver)) {
+            $fbtypemap = [
+                calendar::FREEBUSY_BUSY      => 'busy',
+                calendar::FREEBUSY_TENTATIVE => 'tentative',
+                calendar::FREEBUSY_OOF       => 'outofoffice',
+            ];
 
-      return $events;
-  }
+            // if the backend has free-busy information
+            $fblist = $this->cal->driver->get_freebusy_list($rec['email'], $start, $end);
+            if (is_array($fblist)) {
+                foreach ($fblist as $slot) {
+                    list($from, $to, $type) = $slot;
+                    if ($type == calendar::FREEBUSY_FREE || $type == calendar::FREEBUSY_UNKNOWN) {
+                        continue;
+                    }
+
+                    if ($from < $end && $to > $start) {
+                        $events[] = [
+                            'id'     => sha1($id . $from . $to),
+                            'title'  => $rec['name'],
+                            'start'  => new DateTime('@' . $from),
+                            'end'    => new DateTime('@' . $to),
+                            'status' => $fbtypemap[$type],
+                            'calendar' => '_resource',
+                        ];
+                    }
+                }
+            }
+        }
+
+        return $events;
+    }
 }
diff --git a/plugins/calendar/lib/calendar_itip.php b/plugins/calendar/lib/calendar_itip.php
index e2a2402b..4f7f382f 100644
--- a/plugins/calendar/lib/calendar_itip.php
+++ b/plugins/calendar/lib/calendar_itip.php
@@ -1,240 +1,258 @@
 <?php
 
 require_once realpath(__DIR__ . '/../../libcalendaring/lib/libcalendaring_itip.php');
 
 /**
  * iTIP functions for the Calendar plugin
  *
  * Class providing functionality to manage iTIP invitations
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  * @package @package_name@
  *
  * Copyright (C) 2011, 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_itip extends libcalendaring_itip
 {
-  /**
-   * Constructor to set text domain to calendar
-   */
-  function __construct($plugin, $domain = 'calendar')
-  {
-    parent::__construct($plugin, $domain);
-
-    $this->db_itipinvitations = $this->rc->db->table_name('itipinvitations', true);
-  }
-
-  /**
-   * Handler for calendar/itip-status requests
-   */
-  public function get_itip_status($event, $existing = null)
-  {
-    $status = parent::get_itip_status($event, $existing);
-
-    // don't ask for deleting events when declining
-    if ($this->rc->config->get('kolab_invitation_calendars'))
-      $status['saved'] = false;
-
-    return $status;
-  }
-
-  /**
-   * Find invitation record by token
-   *
-   * @param string Invitation token
-   * @return mixed Invitation record as hash array or False if not found
-   */
-  public function get_invitation($token)
-  {
-    if ($parts = $this->decode_token($token)) {
-      $result = $this->rc->db->query("SELECT * FROM $this->db_itipinvitations WHERE `token` = ?", $parts['base']);
-      if ($result && ($rec = $this->rc->db->fetch_assoc($result))) {
-        $rec['event'] = unserialize($rec['event']);
-        $rec['attendee'] = $parts['attendee'];
-        return $rec;
-      }
+    /**
+     * Constructor to set text domain to calendar
+     */
+    function __construct($plugin, $domain = 'calendar')
+    {
+        parent::__construct($plugin, $domain);
+
+        $this->db_itipinvitations = $this->rc->db->table_name('itipinvitations', true);
+    }
+
+    /**
+     * Handler for calendar/itip-status requests
+     */
+    public function get_itip_status($event, $existing = null)
+    {
+        $status = parent::get_itip_status($event, $existing);
+
+        // don't ask for deleting events when declining
+        if ($this->rc->config->get('kolab_invitation_calendars')) {
+            $status['saved'] = false;
+        }
+
+        return $status;
     }
-    
-    return false;
-  }
-
-  /**
-   * Update the attendee status of the given invitation record
-   *
-   * @param array Invitation record as fetched with calendar_itip::get_invitation()
-   * @param string Attendee email address
-   * @param string New attendee status
-   */
-  public function update_invitation($invitation, $email, $newstatus)
-  {
-    if (is_string($invitation))
-      $invitation = $this->get_invitation($invitation);
-    
-    if ($invitation['token'] && $invitation['event']) {
-      // update attendee record in event data
-      foreach ($invitation['event']['attendees'] as $i => $attendee) {
-        if ($attendee['role'] == 'ORGANIZER') {
-          $organizer = $attendee;
+
+    /**
+     * Find invitation record by token
+     *
+     * @param string $token Invitation token
+     *
+     * @return mixed Invitation record as hash array or False if not found
+     */
+    public function get_invitation($token)
+    {
+        if ($parts = $this->decode_token($token)) {
+            $result = $this->rc->db->query("SELECT * FROM $this->db_itipinvitations WHERE `token` = ?", $parts['base']);
+            if ($result && ($rec = $this->rc->db->fetch_assoc($result))) {
+                $rec['event']    = unserialize($rec['event']);
+                $rec['attendee'] = $parts['attendee'];
+
+                return $rec;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Update the attendee status of the given invitation record
+     *
+     * @param array  $invitation Invitation record as fetched with calendar_itip::get_invitation()
+     * @param string $email      Attendee email address
+     * @param string $newstatus  New attendee status
+     */
+    public function update_invitation($invitation, $email, $newstatus)
+    {
+        if (is_string($invitation)) {
+            $invitation = $this->get_invitation($invitation);
+        }
+
+        if (!empty($invitation['token']) && !empty($invitation['event'])) {
+            // update attendee record in event data
+            foreach ($invitation['event']['attendees'] as $i => $attendee) {
+                if ($attendee['role'] == 'ORGANIZER') {
+                    $organizer = $attendee;
+                }
+                else if ($attendee['email'] == $email) {
+                    // nothing to be done here
+                    if ($attendee['status'] == $newstatus) {
+                        return true;
+                    }
+
+                    $invitation['event']['attendees'][$i]['status'] = $newstatus;
+                    $this->sender = $attendee;
+                }
+            }
+
+            $invitation['event']['changed'] = new DateTime();
+
+            // send iTIP REPLY message to organizer
+            if (!empty($organizer)) {
+                $status = strtolower($newstatus);
+                if ($this->send_itip_message($invitation['event'], 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status)) {
+                    $mailto = !empty($organizer['name']) ? $organizer['name'] : $organizer['email'];
+                    $message = $this->plugin->gettext([
+                            'name' => 'sentresponseto',
+                            'vars' => ['mailto' => $mailto]
+                    ]);
+                    $this->rc->output->command('display_message', $message, 'confirmation');
+                }
+                else {
+                    $this->rc->output->command('display_message', $this->plugin->gettext('itipresponseerror'), 'error');
+                }
+            }
+
+            // update record in DB
+            $query = $this->rc->db->query(
+                "UPDATE $this->db_itipinvitations SET `event` = ? WHERE `token` = ?",
+                self::serialize_event($invitation['event']),
+                $invitation['token']
+            );
+
+            if ($this->rc->db->affected_rows($query)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Create iTIP invitation token for later replies via URL
+     *
+     * @param array  $event    Hash array with event properties
+     * @param string $attendee Attendee email address
+     *
+     * @return string Invitation token
+     */
+    public function store_invitation($event, $attendee)
+    {
+        static $stored = [];
+
+        if (empty($event['uid']) || !$attendee) {
+            return false;
+        }
+
+        // generate token for this invitation
+        $token = $this->generate_token($event, $attendee);
+        $base = substr($token, 0, 40);
+
+        // already stored this
+        if (!empty($stored[$base])) {
+            return $token;
         }
-        else if ($attendee['email'] == $email) {
-          // nothing to be done here
-          if ($attendee['status'] == $newstatus)
-            return true;
-          
-          $invitation['event']['attendees'][$i]['status'] = $newstatus;
-          $this->sender = $attendee;
+
+        // delete old entry
+        $this->rc->db->query("DELETE FROM $this->db_itipinvitations WHERE `token` = ?", $base);
+
+        $event_uid = $event['uid'] . (!empty($event['_instance']) ? '-' . $event['_instance'] : '');
+
+        $query = $this->rc->db->query(
+            "INSERT INTO $this->db_itipinvitations"
+            . " (`token`, `event_uid`, `user_id`, `event`, `expires`)"
+            . " VALUES(?, ?, ?, ?, ?)",
+            $base,
+            $event_uid,
+            $this->rc->user->ID,
+            self::serialize_event($event),
+            date('Y-m-d H:i:s', $event['end']->format('U') + 86400 * 2)
+        );
+
+        if ($this->rc->db->affected_rows($query)) {
+            $stored[$base] = 1;
+            return $token;
         }
-      }
-      $invitation['event']['changed'] = new DateTime();
-      
-      // send iTIP REPLY message to organizer
-      if ($organizer) {
-        $status = strtolower($newstatus);
-        if ($this->send_itip_message($invitation['event'], 'REPLY', $organizer, 'itipsubject' . $status, 'itipmailbody' . $status))
-          $this->rc->output->command('display_message', $this->plugin->gettext(array('name' => 'sentresponseto', 'vars' => array('mailto' => $organizer['name'] ? $organizer['name'] : $organizer['email']))), 'confirmation');
-        else
-          $this->rc->output->command('display_message', $this->plugin->gettext('itipresponseerror'), 'error');
-      }
-      
-      // update record in DB
-      $query = $this->rc->db->query(
-        "UPDATE $this->db_itipinvitations
-         SET `event` = ?
-         WHERE `token` = ?",
-        self::serialize_event($invitation['event']),
-        $invitation['token']
-      );
-
-      if ($this->rc->db->affected_rows($query))
-        return true;
+
+        return false;
     }
-    
-    return false;
-  }
-
-
-  /**
-   * Create iTIP invitation token for later replies via URL
-   *
-   * @param array Hash array with event properties
-   * @param string Attendee email address
-   * @return string Invitation token
-   */
-  public function store_invitation($event, $attendee)
-  {
-    static $stored = array();
-    
-    if (!$event['uid'] || !$attendee)
-      return false;
-      
-    // generate token for this invitation
-    $token = $this->generate_token($event, $attendee);
-    $base = substr($token, 0, 40);
-    
-    // already stored this
-    if ($stored[$base])
-      return $token;
-
-    // delete old entry
-    $this->rc->db->query("DELETE FROM $this->db_itipinvitations WHERE `token` = ?", $base);
-
-    $event_uid = $event['uid'] . ($event['_instance'] ? '-' . $event['_instance'] : '');
-
-    $query = $this->rc->db->query(
-      "INSERT INTO $this->db_itipinvitations
-       (`token`, `event_uid`, `user_id`, `event`, `expires`)
-       VALUES(?, ?, ?, ?, ?)",
-      $base,
-      $event_uid,
-      $this->rc->user->ID,
-      self::serialize_event($event),
-      date('Y-m-d H:i:s', $event['end']->format('U') + 86400 * 2)
-    );
-    
-    if ($this->rc->db->affected_rows($query)) {
-      $stored[$base] = 1;
-      return $token;
+
+    /**
+     * Mark invitations for the given event as cancelled
+     *
+     * @param array $event Hash array with event properties
+     */
+    public function cancel_itip_invitation($event)
+    {
+        $event_uid = $event['uid'] . (!empty($event['_instance']) ? '-' . $event['_instance'] : '');
+
+        // flag invitation record as cancelled
+        $this->rc->db->query(
+            "UPDATE $this->db_itipinvitations SET `cancelled` = 1"
+            . " WHERE `event_uid` = ? AND `user_id` = ?",
+           $event_uid,
+           $this->rc->user->ID
+        );
     }
-    
-    return false;
-  }
-
-  /**
-   * Mark invitations for the given event as cancelled
-   *
-   * @param array Hash array with event properties
-   */
-  public function cancel_itip_invitation($event)
-  {
-    $event_uid = $event['uid'] . ($event['_instance'] ? '-' . $event['_instance'] : '');
-
-    // flag invitation record as cancelled
-    $this->rc->db->query(
-      "UPDATE $this->db_itipinvitations
-       SET `cancelled` = 1
-       WHERE `event_uid` = ? AND `user_id` = ?",
-       $event_uid,
-       $this->rc->user->ID
-    );
-  }
-
-  /**
-   * Generate an invitation request token for the given event and attendee
-   *
-   * @param array Event hash array
-   * @param string Attendee email address
-   */
-  public function generate_token($event, $attendee)
-  {
-    $event_uid = $event['uid'] . ($event['_instance'] ? '-' . $event['_instance'] : '');
-    $base = sha1($event_uid . ';' . $this->rc->user->ID);
-    $mail = base64_encode($attendee);
-    $hash = substr(md5($base . $mail . $this->rc->config->get('des_key')), 0, 6);
-    
-    return "$base.$mail.$hash";
-  }
-
-  /**
-   * Decode the given iTIP request token and return its parts
-   *
-   * @param string Request token to decode
-   * @return mixed Hash array with parts or False if invalid
-   */
-  public function decode_token($token)
-  {
-    list($base, $mail, $hash) = explode('.', $token);
-    
-    // validate and return parts
-    if ($mail && $hash && $hash == substr(md5($base . $mail . $this->rc->config->get('des_key')), 0, 6)) {
-      return array('base' => $base, 'attendee' => base64_decode($mail));
+
+    /**
+     * Generate an invitation request token for the given event and attendee
+     *
+     * @param array  $event    Event hash array
+     * @param string $attendee Attendee email address
+     */
+    public function generate_token($event, $attendee)
+    {
+        $event_uid = $event['uid'] . (!empty($event['_instance']) ? '-' . $event['_instance'] : '');
+        $base = sha1($event_uid . ';' . $this->rc->user->ID);
+        $mail = base64_encode($attendee);
+        $hash = substr(md5($base . $mail . $this->rc->config->get('des_key')), 0, 6);
+
+        return "$base.$mail.$hash";
+    }
+
+    /**
+     * Decode the given iTIP request token and return its parts
+     *
+     * @param string $token Request token to decode
+     *
+     * @return mixed Hash array with parts or False if invalid
+     */
+    public function decode_token($token)
+    {
+        list($base, $mail, $hash) = explode('.', $token);
+
+        // validate and return parts
+        if ($mail && $hash && $hash == substr(md5($base . $mail . $this->rc->config->get('des_key')), 0, 6)) {
+            return ['base' => $base, 'attendee' => base64_decode($mail)];
+        }
+
+        return false;
     }
-    
-    return false;
-  }
-
-  /**
-   * Helper method to serialize the given event for storing in invitations table
-   */
-  private static function serialize_event($event)
-  {
-    $ev = $event;
-    $ev['description'] = abbreviate_string($ev['description'], 100);
-    unset($ev['attachments']);
-    return serialize($ev);
-  }
 
+    /**
+     * Helper method to serialize the given event for storing in invitations table
+     */
+    private static function serialize_event($event)
+    {
+        $ev = $event;
+
+        if (!empty($ev['description'])) {
+            $ev['description'] = abbreviate_string($ev['description'], 100);
+        }
+
+        unset($ev['attachments']);
+
+        return serialize($ev);
+    }
 }
diff --git a/plugins/calendar/lib/calendar_recurrence.php b/plugins/calendar/lib/calendar_recurrence.php
index c0d7c793..4888fe18 100644
--- a/plugins/calendar/lib/calendar_recurrence.php
+++ b/plugins/calendar/lib/calendar_recurrence.php
@@ -1,88 +1,89 @@
 <?php
 
 require_once realpath(__DIR__ . '/../../libcalendaring/lib/libcalendaring_recurrence.php');
 
 /**
  * Recurrence computation class for the Calendar plugin
  *
  * Uitility class to compute instances of recurring events.
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012-2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 class calendar_recurrence extends libcalendaring_recurrence
 {
-  private $event;
-  private $duration;
+    private $event;
+    private $duration;
 
-  /**
-   * Default constructor
-   *
-   * @param object calendar The calendar plugin instance
-   * @param array The event object to operate on
-   */
-  function __construct($cal, $event)
-  {
-    parent::__construct($cal->lib);
+    /**
+     * Default constructor
+     *
+     * @param calendar $cal   The calendar plugin instance
+     * @param array    $event The event object to operate on
+     */
+    function __construct($cal, $event)
+    {
+        parent::__construct($cal->lib);
 
-    $this->event = $event;
+        $this->event = $event;
 
-    if (is_object($event['start']) && is_object($event['end']))
-      $this->duration = $event['start']->diff($event['end']);
+        if (is_object($event['start']) && is_object($event['end'])) {
+            $this->duration = $event['start']->diff($event['end']);
+        }
 
-    $event['start']->_dateonly |= $event['allday'];
-    $this->init($event['recurrence'], $event['start']);
-  }
+        $event['start']->_dateonly = !empty($event['allday']);
 
-  /**
-   * Alias of libcalendaring_recurrence::next()
-   *
-   * @return mixed DateTime object or False if recurrence ended
-   */
-  public function next_start()
-  {
-    return $this->next();
-  }
+        $this->init($event['recurrence'], $event['start']);
+    }
 
-  /**
-   * Get the next recurring instance of this event
-   *
-   * @return mixed Array with event properties or False if recurrence ended
-   */
-  public function next_instance()
-  {
-    if ($next_start = $this->next()) {
-      $next = $this->event;
-      $next['start'] = $next_start;
+    /**
+     * Alias of libcalendaring_recurrence::next()
+     *
+     * @return mixed DateTime object or False if recurrence ended
+     */
+    public function next_start()
+    {
+        return $this->next();
+    }
 
-      if ($this->duration) {
-        $next['end'] = clone $next_start;
-        $next['end']->add($this->duration);
-      }
+    /**
+     * Get the next recurring instance of this event
+     *
+     * @return mixed Array with event properties or False if recurrence ended
+     */
+    public function next_instance()
+    {
+        if ($next_start = $this->next()) {
+            $next = $this->event;
+            $next['start'] = $next_start;
 
-      $next['recurrence_date'] = clone $next_start;
-      $next['_instance'] = libcalendaring::recurrence_instance_identifier($next, $this->event['allday']);
+            if ($this->duration) {
+                $next['end'] = clone $next_start;
+                $next['end']->add($this->duration);
+            }
 
-      unset($next['_formatobj']);
+            $next['recurrence_date'] = clone $next_start;
+            $next['_instance'] = libcalendaring::recurrence_instance_identifier($next, $this->event['allday']);
 
-      return $next;
-    }
+            unset($next['_formatobj']);
 
-    return false;
-  }
+            return $next;
+        }
 
+        return false;
+    }
 }
diff --git a/plugins/calendar/lib/calendar_ui.php b/plugins/calendar/lib/calendar_ui.php
index 63ab9c3b..b8366c4f 100644
--- a/plugins/calendar/lib/calendar_ui.php
+++ b/plugins/calendar/lib/calendar_ui.php
@@ -1,843 +1,1022 @@
 <?php
 /**
  * User Interface class for the Calendar plugin
  *
  * @author Lazlo Westerhof <hello@lazlo.me>
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2010, Lazlo Westerhof <hello@lazlo.me>
  * Copyright (C) 2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 class calendar_ui
 {
-  private $rc;
-  private $cal;
-  private $ready = false;
-  public $screen;
-
-  function __construct($cal)
-  {
-    $this->cal = $cal;
-    $this->rc = $cal->rc;
-    $this->screen = $this->rc->task == 'calendar' ? ($this->rc->action ? $this->rc->action: 'calendar') : 'other';
-  }
-
-  /**
-   * Calendar UI initialization and requests handlers
-   */
-  public function init()
-  {
-    if ($this->ready)  // already done
-      return;
-
-    // add taskbar button
-    $this->cal->add_button(array(
-      'command'    => 'calendar',
-      'class'      => 'button-calendar',
-      'classsel'   => 'button-calendar button-selected',
-      'innerclass' => 'button-inner',
-      'label'      => 'calendar.calendar',
-      'type'       => 'link'
-      ), 'taskbar');
-    
-    // load basic client script
-    if ($this->rc->action != 'print') {
-      $this->cal->include_script('calendar_base.js');
-    }
-
-    $this->addCSS();
-
-    $this->ready = true;
-  }
-
-  /**
-   * Register handler methods for the template engine
-   */
-  public function init_templates()
-  {
-    $this->cal->register_handler('plugin.calendar_css', array($this, 'calendar_css'));
-    $this->cal->register_handler('plugin.calendar_list', array($this, 'calendar_list'));
-    $this->cal->register_handler('plugin.calendar_select', array($this, 'calendar_select'));
-    $this->cal->register_handler('plugin.identity_select', array($this, 'identity_select'));
-    $this->cal->register_handler('plugin.category_select', array($this, 'category_select'));
-    $this->cal->register_handler('plugin.status_select', array($this, 'status_select'));
-    $this->cal->register_handler('plugin.freebusy_select', array($this, 'freebusy_select'));
-    $this->cal->register_handler('plugin.priority_select', array($this, 'priority_select'));
-    $this->cal->register_handler('plugin.sensitivity_select', array($this, 'sensitivity_select'));
-    $this->cal->register_handler('plugin.alarm_select', array($this, 'alarm_select'));
-    $this->cal->register_handler('plugin.recurrence_form', array($this->cal->lib, 'recurrence_form'));
-    $this->cal->register_handler('plugin.attendees_list', array($this, 'attendees_list'));
-    $this->cal->register_handler('plugin.attendees_form', array($this, 'attendees_form'));
-    $this->cal->register_handler('plugin.resources_form', array($this, 'resources_form'));
-    $this->cal->register_handler('plugin.resources_list', array($this, 'resources_list'));
-    $this->cal->register_handler('plugin.resources_searchform', array($this, 'resources_search_form'));
-    $this->cal->register_handler('plugin.resource_info', array($this, 'resource_info'));
-    $this->cal->register_handler('plugin.resource_calendar', array($this, 'resource_calendar'));
-    $this->cal->register_handler('plugin.attendees_freebusy_table', array($this, 'attendees_freebusy_table'));
-    $this->cal->register_handler('plugin.edit_attendees_notify', array($this, 'edit_attendees_notify'));
-    $this->cal->register_handler('plugin.edit_recurrence_sync', array($this, 'edit_recurrence_sync'));
-    $this->cal->register_handler('plugin.edit_recurring_warning', array($this, 'recurring_event_warning'));
-    $this->cal->register_handler('plugin.event_rsvp_buttons', array($this, 'event_rsvp_buttons'));
-    $this->cal->register_handler('plugin.agenda_options', array($this, 'agenda_options'));
-    $this->cal->register_handler('plugin.events_import_form', array($this, 'events_import_form'));
-    $this->cal->register_handler('plugin.events_export_form', array($this, 'events_export_form'));
-    $this->cal->register_handler('plugin.object_changelog_table', array('libkolab', 'object_changelog_table'));
-    $this->cal->register_handler('plugin.searchform', array($this->rc->output, 'search_form'));  // use generic method from rcube_template
-
-    kolab_attachments_handler::ui();
-  }
-
-  /**
-   * Adds CSS stylesheets to the page header
-   */
-  public function addCSS()
-  {
-    $skin_path = $this->cal->local_skin_path();
+    private $rc;
+    private $cal;
+    private $ready = false;
+
+    public $screen;
+
+    function __construct($cal)
+    {
+        $this->cal    = $cal;
+        $this->rc     = $cal->rc;
+        $this->screen = $this->rc->task == 'calendar' ? ($this->rc->action ?: 'calendar') : 'other';
+    }
+
+    /**
+     * Calendar UI initialization and requests handlers
+     */
+    public function init()
+    {
+        if ($this->ready) {
+            // already done
+            return;
+        }
+
+        // add taskbar button
+        $this->cal->add_button([
+                'command'    => 'calendar',
+                'class'      => 'button-calendar',
+                'classsel'   => 'button-calendar button-selected',
+                'innerclass' => 'button-inner',
+                'label'      => 'calendar.calendar',
+                'type'       => 'link'
+            ],
+            'taskbar'
+        );
+
+        // load basic client script
+        if ($this->rc->action != 'print') {
+            $this->cal->include_script('calendar_base.js');
+        }
+
+        $this->addCSS();
+
+        $this->ready = true;
+    }
+
+    /**
+     * Register handler methods for the template engine
+     */
+    public function init_templates()
+    {
+        $this->cal->register_handler('plugin.calendar_css', [$this, 'calendar_css']);
+        $this->cal->register_handler('plugin.calendar_list', [$this, 'calendar_list']);
+        $this->cal->register_handler('plugin.calendar_select', [$this, 'calendar_select']);
+        $this->cal->register_handler('plugin.identity_select', [$this, 'identity_select']);
+        $this->cal->register_handler('plugin.category_select', [$this, 'category_select']);
+        $this->cal->register_handler('plugin.status_select', [$this, 'status_select']);
+        $this->cal->register_handler('plugin.freebusy_select', [$this, 'freebusy_select']);
+        $this->cal->register_handler('plugin.priority_select', [$this, 'priority_select']);
+        $this->cal->register_handler('plugin.sensitivity_select', [$this, 'sensitivity_select']);
+        $this->cal->register_handler('plugin.alarm_select', [$this, 'alarm_select']);
+        $this->cal->register_handler('plugin.recurrence_form', [$this->cal->lib, 'recurrence_form']);
+        $this->cal->register_handler('plugin.attendees_list', [$this, 'attendees_list']);
+        $this->cal->register_handler('plugin.attendees_form', [$this, 'attendees_form']);
+        $this->cal->register_handler('plugin.resources_form', [$this, 'resources_form']);
+        $this->cal->register_handler('plugin.resources_list', [$this, 'resources_list']);
+        $this->cal->register_handler('plugin.resources_searchform', [$this, 'resources_search_form']);
+        $this->cal->register_handler('plugin.resource_info', [$this, 'resource_info']);
+        $this->cal->register_handler('plugin.resource_calendar', [$this, 'resource_calendar']);
+        $this->cal->register_handler('plugin.attendees_freebusy_table', [$this, 'attendees_freebusy_table']);
+        $this->cal->register_handler('plugin.edit_attendees_notify', [$this, 'edit_attendees_notify']);
+        $this->cal->register_handler('plugin.edit_recurrence_sync', [$this, 'edit_recurrence_sync']);
+        $this->cal->register_handler('plugin.edit_recurring_warning', [$this, 'recurring_event_warning']);
+        $this->cal->register_handler('plugin.event_rsvp_buttons', [$this, 'event_rsvp_buttons']);
+        $this->cal->register_handler('plugin.agenda_options', [$this, 'agenda_options']);
+        $this->cal->register_handler('plugin.events_import_form', [$this, 'events_import_form']);
+        $this->cal->register_handler('plugin.events_export_form', [$this, 'events_export_form']);
+        $this->cal->register_handler('plugin.object_changelog_table', ['libkolab', 'object_changelog_table']);
+        $this->cal->register_handler('plugin.searchform', [$this->rc->output, 'search_form']);
+
+        kolab_attachments_handler::ui();
+    }
+
+    /**
+     * Adds CSS stylesheets to the page header
+     */
+    public function addCSS()
+    {
+        $skin_path = $this->cal->local_skin_path();
  
-    if ($this->rc->task == 'calendar' && (!$this->rc->action || in_array($this->rc->action, array('index', 'print')))) {
-      // Include fullCalendar style before skin file for simpler style overriding
-      $this->cal->include_stylesheet($skin_path . '/fullcalendar.css');
-    }
-
-    $this->cal->include_stylesheet($skin_path . '/calendar.css');
-
-    if ($this->rc->task == 'calendar' && $this->rc->action == 'print') {
-      $this->cal->include_stylesheet($skin_path . '/print.css');
+        if (
+            $this->rc->task == 'calendar'
+            && (!$this->rc->action || in_array($this->rc->action, ['index', 'print']))
+        ) {
+            // Include fullCalendar style before skin file for simpler style overriding
+            $this->cal->include_stylesheet($skin_path . '/fullcalendar.css');
+        }
+
+        $this->cal->include_stylesheet($skin_path . '/calendar.css');
+
+        if ($this->rc->task == 'calendar' && $this->rc->action == 'print') {
+            $this->cal->include_stylesheet($skin_path . '/print.css');
+        }
+    }
+
+    /**
+     * Adds JS files to the page header
+     */
+    public function addJS()
+    {
+        $this->cal->include_script('lib/js/moment.js');
+        $this->cal->include_script('lib/js/fullcalendar.js');
+
+        if ($this->rc->task == 'calendar' && $this->rc->action == 'print') {
+            $this->cal->include_script('print.js');
+        }
+        else {
+            $this->rc->output->include_script('treelist.js');
+            $this->cal->api->include_script('libkolab/libkolab.js');
+            $this->cal->include_script('calendar_ui.js');
+            jqueryui::miniColors();
+        }
+    }
+
+    /**
+     * Add custom style for the calendar UI
+     */
+    function calendar_css($attrib = [])
+    {
+        $categories    = $this->cal->driver->list_categories();
+        $calendars     = $this->cal->driver->list_calendars();
+        $js_categories = [];
+
+        $mode = $this->rc->config->get('calendar_event_coloring', $this->cal->defaults['calendar_event_coloring']);
+        $css  = "\n";
+
+        foreach ((array) $categories as $class => $color) {
+            if (!empty($color)) {
+                $js_categories[$class] = $color;
+
+                $color = ltrim($color, '#');
+                $class = 'cat-' . asciiwords(strtolower($class), true);
+                $css  .= ".$class { color: #$color; }\n";
+            }
+        }
+
+        $this->rc->output->set_env('calendar_categories', $js_categories);
+
+        foreach ((array) $calendars as $id => $prop) {
+            if (!empty($prop['color'])) {
+                $css .= $this->calendar_css_classes($id, $prop, $mode, $attrib);
+            }
+        }
+
+        return html::tag('style', ['type' => 'text/css'], $css);
+    }
+
+    /**
+     * Calendar folder specific CSS classes
+     */
+    public function calendar_css_classes($id, $prop, $mode, $attrib = [])
+    {
+        $color = $folder_color = $prop['color'];
+
+        // replace white with skin-defined color
+        if (!empty($attrib['folder-fallback-color']) && preg_match('/^f+$/i', $folder_color)) {
+            $folder_color = ltrim($attrib['folder-fallback-color'], '#');
+        }
+
+        $class = 'cal-' . asciiwords($id, true);
+        $css   = str_replace('$class', $class, $attrib['folder-class']) ?: "li .$class";
+        $css  .= " { color: #$folder_color; }\n";
+
+        return $css . ".$class .handle { background-color: #$color; }\n";
+    }
+
+    /**
+     * Generate HTML content of the calendars list (or metadata only)
+     */
+    function calendar_list($attrib = [], $js_only = false)
+    {
+        $html      = '';
+        $jsenv     = [];
+        $tree      = true;
+        $calendars = $this->cal->driver->list_calendars(0, $tree);
+
+        // walk folder tree
+        if (is_object($tree)) {
+            $html = $this->list_tree_html($tree, $calendars, $jsenv, $attrib);
+
+            // append birthdays calendar which isn't part of $tree
+            if (!empty($calendars[calendar_driver::BIRTHDAY_CALENDAR_ID])) {
+                $bdaycal = $calendars[calendar_driver::BIRTHDAY_CALENDAR_ID];
+                $calendars = [calendar_driver::BIRTHDAY_CALENDAR_ID => $bdaycal];
+            }
+            else {
+                $calendars = [];  // clear array for flat listing
+            }
+        }
+        else if (isset($attrib['class'])) {
+            // fall-back to flat folder listing
+            $attrib['class'] .= ' flat';
+        }
+
+        foreach ((array) $calendars as $id => $prop) {
+            if (!empty($attrib['activeonly']) && empty($prop['active'])) {
+                continue;
+            }
+
+            $li_content = $this->calendar_list_item($id, $prop, $jsenv, !empty($attrib['activeonly']));
+            $li_attr = [
+                'id'    => 'rcmlical' . $id,
+                'class' => isset($prop['group']) ? $prop['group'] : null,
+            ];
+
+            $html .= html::tag('li', $li_attr, $li_content);
+        }
+
+        $this->rc->output->set_env('calendars', $jsenv);
+
+        if ($js_only) {
+            return;
+        }
+
+        $this->rc->output->set_env('source', rcube_utils::get_input_value('source', rcube_utils::INPUT_GET));
+        $this->rc->output->add_gui_object('calendarslist', !empty($attrib['id']) ? $attrib['id'] : 'rccalendarlist');
+
+        return html::tag('ul', $attrib, $html, html::$common_attrib);
+    }
+
+    /**
+     * Return html for a structured list <ul> for the folder tree
+     */
+    public function list_tree_html($node, $data, &$jsenv, $attrib)
+    {
+        $out = '';
+        foreach ($node->children as $folder) {
+            $id   = $folder->id;
+            $prop = $data[$id];
+            $is_collapsed = false; // TODO: determine this somehow?
+
+            $content = $this->calendar_list_item($id, $prop, $jsenv, !empty($attrib['activeonly']));
+
+            if (!empty($folder->children)) {
+                $content .= html::tag('ul', ['style' => $is_collapsed ? "display:none;" : null],
+                    $this->list_tree_html($folder, $data, $jsenv, $attrib)
+                );
+            }
+
+            if (strlen($content)) {
+                $li_attr = [
+                    'id'    => 'rcmlical' . rcube_utils::html_identifier($id),
+                    'class' => $prop['group'] . (!empty($prop['virtual']) ? ' virtual' : ''),
+                ];
+                $out .= html::tag('li', $li_attr, $content);
+            }
+        }
+
+        return $out;
+    }
+
+    /**
+     * Helper method to build a calendar list item (HTML content and js data)
+     */
+    public function calendar_list_item($id, $prop, &$jsenv, $activeonly = false)
+    {
+        // enrich calendar properties with settings from the driver
+        if (empty($prop['virtual'])) {
+            unset($prop['user_id']);
+
+            $prop['alarms']      = $this->cal->driver->alarms;
+            $prop['attendees']   = $this->cal->driver->attendees;
+            $prop['freebusy']    = $this->cal->driver->freebusy;
+            $prop['attachments'] = $this->cal->driver->attachments;
+            $prop['undelete']    = $this->cal->driver->undelete;
+            $prop['feedurl']     = $this->cal->get_url([
+                    '_cal'   => $this->cal->ical_feed_hash($id) . '.ics',
+                    'action' => 'feed'
+                ]
+            );
+
+            $jsenv[$id] = $prop;
+        }
+
+        if (!empty($prop['title'])) {
+            $title = $prop['title'];
+        }
+        else if ($prop['name'] != $prop['listname'] || strlen($prop['name']) > 25) {
+            $title = html_entity_decode($prop['name'], ENT_COMPAT, RCUBE_CHARSET);
+        }
+        else {
+            $title = '';
+        }
+
+        $classes = ['calendar', 'cal-'  . asciiwords($id, true)];
+
+        if (!empty($prop['virtual'])) {
+            $classes[] = 'virtual';
+        }
+        else if (empty($prop['editable'])) {
+            $classes[] = 'readonly';
+        }
+        if (!empty($prop['subscribed'])) {
+            $classes[] = 'subscribed';
+
+            if ($prop['subscribed'] === 2) {
+                $classes[] = 'partial';
+            }
+        }
+        if (!empty($prop['class'])) {
+            $classes[] = $prop['class'];
+        }
+
+        $content = '';
+
+        if (!$activeonly || !empty($prop['active'])) {
+            $label_id = 'cl:' . $id;
+            $content = html::a(
+                ['class' => 'calname', 'id' => $label_id, 'title' => $title, 'href' => '#'],
+                rcube::Q(!empty($prop['editname']) ? $prop['editname'] : $prop['listname'])
+            );
+
+            if (empty($prop['virtual'])) {
+                $color   = !empty($prop['color']) ? $prop['color'] : 'f00';
+                $actions = '';
+
+                if (!EMPTY($prop['removable'])) {
+                    $actions .= html::a([
+                            'href'  => '#',
+                            'class' => 'remove',
+                            'title' => $this->cal->gettext('removelist')
+                        ], ' '
+                    );
+                }
+
+                $actions .= html::a([
+                        'href'  => '#',
+                        'class' => 'quickview',
+                        'title' => $this->cal->gettext('quickview'),
+                        'role'  => 'checkbox',
+                        'aria-checked' => 'false'
+                    ], ''
+                );
+
+                if (!empty($prop['subscribed'])) {
+                    $actions .= html::a([
+                            'href'  => '#',
+                            'class' => 'subscribed',
+                            'title' => $this->cal->gettext('calendarsubscribe'),
+                            'role'  => 'checkbox',
+                            'aria-checked' => !empty($prop['subscribed']) ? 'true' : 'false'
+                        ], ' '
+                    );
+                }
+
+                $content .= html::tag('input', [
+                        'type'    => 'checkbox',
+                        'name'    => '_cal[]',
+                        'value'   => $id,
+                        'checked' => !empty($prop['active']),
+                        'aria-labelledby' => $label_id
+                    ])
+                    . html::span('actions', $actions)
+                    . html::span(['class' => 'handle', 'style' => "background-color: #$color"], '&nbsp;');
+            }
+
+            $content = html::div(join(' ', $classes), $content);
+        }
+
+        return $content;
+    }
+
+    /**
+     * Render a HTML for agenda options form
+     */
+    function agenda_options($attrib = [])
+    {
+        $attrib += ['id' => 'agendaoptions'];
+        $attrib['style'] = 'display:none';
+
+        $select_range = new html_select(['name' => 'listrange', 'id' => 'agenda-listrange', 'class' => 'form-control custom-select']);
+        $select_range->add(1 . ' ' . preg_replace('/\(.+\)/', '', $this->cal->lib->gettext('days')), '');
+
+        foreach ([2,5,7,14,30,60,90,180,365] as $days) {
+            $select_range->add($days . ' ' . preg_replace('/\(|\)/', '', $this->cal->lib->gettext('days')), $days);
+        }
+
+        $html = html::span('input-group',
+            html::label(['for' => 'agenda-listrange', 'class' => 'input-group-prepend'],
+                html::span('input-group-text', $this->cal->gettext('listrange'))
+            )
+            . $select_range->show($this->rc->config->get('calendar_agenda_range', $this->cal->defaults['calendar_agenda_range']))
+        );
+
+        return html::div($attrib, $html);
+    }
+
+    /**
+     * Render a HTML select box for calendar selection
+     */
+    function calendar_select($attrib = [])
+    {
+        $attrib['name']       = 'calendar';
+        $attrib['is_escaped'] = true;
+
+        $select = new html_select($attrib);
+
+        foreach ((array) $this->cal->driver->list_calendars() as $id => $prop) {
+            if (
+                !empty($prop['editable'])
+                || (!empty($prop['rights']) && strpos($prop['rights'], 'i') !== false)
+            ) {
+                $select->add($prop['name'], $id);
+            }
+        }
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render a HTML select box for user identity selection
+     */
+    function identity_select($attrib = [])
+    {
+        $attrib['name'] = 'identity';
+
+        $select     = new html_select($attrib);
+        $identities = $this->rc->user->list_emails();
+
+        foreach ($identities as $ident) {
+            $select->add(format_email_recipient($ident['email'], $ident['name']), $ident['identity_id']);
+        }
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render a HTML select box to select an event category
+     */
+    function category_select($attrib = [])
+    {
+        $attrib['name'] = 'categories';
+
+        $select = new html_select($attrib);
+        $select->add('---', '');
+        foreach (array_keys((array) $this->cal->driver->list_categories()) as $cat) {
+              $select->add($cat, $cat);
+        }
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render a HTML select box for status property
+     */
+    function status_select($attrib = [])
+    {
+        $attrib['name'] = 'status';
+
+        $select = new html_select($attrib);
+        $select->add('---', '');
+        $select->add($this->cal->gettext('status-confirmed'), 'CONFIRMED');
+        $select->add($this->cal->gettext('status-cancelled'), 'CANCELLED');
+        $select->add($this->cal->gettext('status-tentative'), 'TENTATIVE');
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render a HTML select box for free/busy/out-of-office property
+     */
+    function freebusy_select($attrib = [])
+    {
+        $attrib['name'] = 'freebusy';
+
+        $select = new html_select($attrib);
+        $select->add($this->cal->gettext('free'), 'free');
+        $select->add($this->cal->gettext('busy'), 'busy');
+        // out-of-office is not supported by libkolabxml (#3220)
+        // $select->add($this->cal->gettext('outofoffice'), 'outofoffice');
+        $select->add($this->cal->gettext('tentative'), 'tentative');
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render a HTML select for event priorities
+     */
+    function priority_select($attrib = [])
+    {
+        $attrib['name'] = 'priority';
+
+        $select = new html_select($attrib);
+        $select->add('---', '0');
+        $select->add('1 ' . $this->cal->gettext('highest'), '1');
+        $select->add('2 ' . $this->cal->gettext('high'), '2');
+        $select->add('3 ', '3');
+        $select->add('4 ', '4');
+        $select->add('5 ' . $this->cal->gettext('normal'), '5');
+        $select->add('6 ', '6');
+        $select->add('7 ', '7');
+        $select->add('8 ' . $this->cal->gettext('low'), '8');
+        $select->add('9 ' . $this->cal->gettext('lowest'),  '9');
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render HTML input for sensitivity selection
+     */
+    function sensitivity_select($attrib = [])
+    {
+        $attrib['name'] = 'sensitivity';
+
+        $select = new html_select($attrib);
+        $select->add($this->cal->gettext('public'), 'public');
+        $select->add($this->cal->gettext('private'), 'private');
+        $select->add($this->cal->gettext('confidential'), 'confidential');
+
+        return $select->show(null);
+    }
+
+    /**
+     * Render HTML form for alarm configuration
+     */
+    function alarm_select($attrib = [])
+    {
+        return $this->cal->lib->alarm_select($attrib, $this->cal->driver->alarm_types, $this->cal->driver->alarm_absolute);
     }
-  }
-
-  /**
-   * Adds JS files to the page header
-   */
-  public function addJS()
-  {
-    $this->cal->include_script('lib/js/moment.js');
-    $this->cal->include_script('lib/js/fullcalendar.js');
 
-    if ($this->rc->task == 'calendar' && $this->rc->action == 'print') {
-      $this->cal->include_script('print.js');
+    /**
+     * Render HTML for attendee notification warning
+     */
+    function edit_attendees_notify($attrib = [])
+    {
+        $checkbox = new html_checkbox(['name' => '_notify', 'id' => 'edit-attendees-donotify', 'value' => 1, 'class' => 'pretty-checkbox']);
+        return html::div($attrib, html::label(null, $checkbox->show(1) . ' ' . $this->cal->gettext('sendnotifications')));
     }
-    else {
-      $this->rc->output->include_script('treelist.js');
-      $this->cal->api->include_script('libkolab/libkolab.js');
-      $this->cal->include_script('calendar_ui.js');
-      jqueryui::miniColors();
+
+    /**
+     * Render HTML for recurrence option to align start date with the recurrence rule
+     */
+    function edit_recurrence_sync($attrib = [])
+    {
+        $checkbox = new html_checkbox(['name' => '_start_sync', 'value' => 1, 'class' => 'pretty-checkbox']);
+        return html::div($attrib, html::label(null, $checkbox->show(1) . ' ' . $this->cal->gettext('eventstartsync')));
     }
-  }
 
-  /**
-   *
-   */
-  function calendar_css($attrib = array())
-  {
-    $categories    = $this->cal->driver->list_categories();
-    $js_categories = array();
-    $mode = $this->rc->config->get('calendar_event_coloring', $this->cal->defaults['calendar_event_coloring']);
-    $css  = "\n";
+    /**
+     * Generate the form for recurrence settings
+     */
+    function recurring_event_warning($attrib = [])
+    {
+        $attrib['id'] = 'edit-recurring-warning';
+
+        $radio = new html_radiobutton(['name' => '_savemode', 'class' => 'edit-recurring-savemode']);
 
-    foreach ((array)$categories as $class => $color) {
-      if (!empty($color)) {
-        $js_categories[$class] = $color;
+        $form = html::label(null, $radio->show('', ['value' => 'current']) . $this->cal->gettext('currentevent')) . ' '
+            . html::label(null, $radio->show('', ['value' => 'future']) . $this->cal->gettext('futurevents')) . ' '
+            . html::label(null, $radio->show('all', ['value' => 'all']) . $this->cal->gettext('allevents')) . ' '
+            . html::label(null, $radio->show('', ['value' => 'new']) . $this->cal->gettext('saveasnew'));
+
+        return html::div($attrib,
+            html::div('message', $this->cal->gettext('changerecurringeventwarning'))
+            . html::div('savemode', $form)
+        );
+    }
 
-        $color = ltrim($color, '#');
-        $class = 'cat-' . asciiwords(strtolower($class), true);
-        $css  .= ".$class { color: #$color; }\n";
-      }
+    /**
+     * Form for uploading and importing events
+     */
+    function events_import_form($attrib = [])
+    {
+        if (empty($attrib['id'])) {
+            $attrib['id'] = 'rcmImportForm';
+        }
+
+        // Get max filesize, enable upload progress bar
+        $max_filesize = $this->rc->upload_init();
+
+        $accept = '.ics, text/calendar, text/x-vcalendar, application/ics';
+        if (class_exists('ZipArchive', false)) {
+            $accept .= ', .zip, application/zip';
+        }
+
+        $input = new html_inputfield([
+                'id'     => 'importfile',
+                'type'   => 'file',
+                'name'   => '_data',
+                'size'   => !empty($attrib['uploadfieldsize']) ? $attrib['uploadfieldsize'] : null,
+                'accept' => $accept
+        ]);
+
+        $select = new html_select(['name' => '_range', 'id' => 'event-import-range']);
+        $select->add([
+                $this->cal->gettext('onemonthback'),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr'=>2]]),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr'=>3]]),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr'=>6]]),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr'=>12]]),
+                $this->cal->gettext('all'),
+            ],
+            ['1','2','3','6','12',0]
+        );
+
+        $html = html::div('form-section form-group row',
+            html::label(['class' => 'col-sm-4 col-form-label', 'for' => 'importfile'],
+                rcube::Q($this->rc->gettext('importfromfile'))
+            )
+            . html::div('col-sm-8', $input->show()
+                . html::div('hint', $this->rc->gettext(['name' => 'maxuploadsize', 'vars' => ['size' => $max_filesize]]))
+            )
+        );
+
+        $html .= html::div('form-section form-group row',
+            html::label(['for' => 'event-import-calendar', 'class' => 'col-form-label col-sm-4'],
+                $this->cal->gettext('calendar')
+            )
+            . html::div('col-sm-8', $this->calendar_select(['name' => 'calendar', 'id' => 'event-import-calendar']))
+        );
+
+        $html .= html::div('form-section form-group row',
+            html::label(['for' => 'event-import-range', 'class' => 'col-form-label col-sm-4'],
+                $this->cal->gettext('importrange')
+            )
+            . html::div('col-sm-8', $select->show(1))
+        );
+
+        $this->rc->output->add_gui_object('importform', $attrib['id']);
+        $this->rc->output->add_label('import');
+
+        return html::tag('p', null, $this->cal->gettext('importtext'))
+            . html::tag('form', [
+                    'action'  => $this->rc->url(['task' => 'calendar', 'action' => 'import_events']),
+                    'method'  => 'post',
+                    'enctype' => 'multipart/form-data',
+                    'id'      => $attrib['id']
+                ], $html
+            );
     }
 
-    $this->rc->output->set_env('calendar_categories', $js_categories);
+    /**
+     * Form to select options for exporting events
+     */
+    function events_export_form($attrib = [])
+    {
+        if (empty($attrib['id'])) {
+            $attrib['id'] = 'rcmExportForm';
+        }
+
+        $html = html::div('form-section form-group row',
+            html::label(['for' => 'event-export-calendar', 'class' => 'col-sm-4 col-form-label'],
+                $this->cal->gettext('calendar')
+            )
+            . html::div('col-sm-8', $this->calendar_select(['name' => 'calendar', 'id' => 'event-export-calendar', 'class' => 'form-control custom-select']))
+        );
+
+        $select = new html_select([
+                'name'  => 'range',
+                'id'    => 'event-export-range',
+                'class' => 'form-control custom-select rounded-right'
+        ]);
+
+        $select->add([
+                $this->cal->gettext('all'),
+                $this->cal->gettext('onemonthback'),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr' => 2]]),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr' => 3]]),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr' => 6]]),
+                $this->cal->gettext(['name' => 'nmonthsback', 'vars' => ['nr' => 12]]),
+                $this->cal->gettext('customdate'),
+            ],
+            [0,'1','2','3','6','12','custom']
+        );
+
+        $startdate = new html_inputfield([
+                'name'  => 'start',
+                'size'  => 11,
+                'id'    => 'event-export-startdate',
+                'style' => 'display:none'
+        ]);
+
+        $html .= html::div('form-section form-group row',
+            html::label(['for' => 'event-export-range', 'class' => 'col-sm-4 col-form-label'],
+                $this->cal->gettext('exportrange')
+            )
+            . html::div('col-sm-8 input-group', $select->show(0) . $startdate->show())
+        );
+
+        $checkbox = new html_checkbox([
+                'name'  => 'attachments',
+                'id'    => 'event-export-attachments',
+                'value' => 1,
+                'class' => 'form-check-input pretty-checkbox'
+        ]);
+
+        $html .= html::div('form-section form-check row',
+            html::label(['for' => 'event-export-attachments', 'class' => 'col-sm-4 col-form-label'],
+                $this->cal->gettext('exportattachments')
+            )
+            . html::div('col-sm-8', $checkbox->show(1))
+        );
+
+        $this->rc->output->add_gui_object('exportform', $attrib['id']);
+
+        return html::tag('form', $attrib + [
+                'action' => $this->rc->url(['task' => 'calendar', 'action' => 'export_events']),
+                'method' => 'post',
+                'id'     => $attrib['id']
+            ],
+            $html
+        );
+    }
 
-    $calendars = $this->cal->driver->list_calendars();
-    foreach ((array)$calendars as $id => $prop) {
-      if ($prop['color']) {
-        $css .= $this->calendar_css_classes($id, $prop, $mode, $attrib);
-      }
+    /**
+     * Handler for calendar form template.
+     * The form content could be overriden by the driver
+     */
+    function calendar_editform($action, $calendar = [])
+    {
+        $this->action   = $action;
+        $this->calendar = $calendar;
+
+        // load miniColors js/css files
+        jqueryui::miniColors();
+
+        $this->rc->output->set_env('pagetitle', $this->cal->gettext('calendarprops'));
+        $this->rc->output->add_handler('folderform', [$this, 'calendarform']);
+        $this->rc->output->send('libkolab.folderform');
     }
 
-    return html::tag('style', array('type' => 'text/css'), $css);
-  }
+    /**
+     * Handler for calendar form template.
+     * The form content could be overriden by the driver
+     */
+    function calendarform($attrib)
+    {
+        // compose default calendar form fields
+        $input_name  = new html_inputfield(['name' => 'name', 'id' => 'calendar-name', 'size' => 20]);
+        $input_color = new html_inputfield(['name' => 'color', 'id' => 'calendar-color', 'size' => 7, 'class' => 'colors']);
+
+        $formfields = [
+            'name' => [
+                'label' => $this->cal->gettext('name'),
+                'value' => $input_name->show($calendar['name']),
+                'id'    => 'calendar-name',
+            ],
+            'color' => [
+                'label' => $this->cal->gettext('color'),
+                'value' => $input_color->show($calendar['color']),
+                'id'    => 'calendar-color',
+            ],
+        ];
+
+        if (!empty($this->cal->driver->alarms)) {
+            $checkbox = new html_checkbox(['name' => 'showalarms', 'id' => 'calendar-showalarms', 'value' => 1]);
+
+            $formfields['showalarms'] = [
+                'label' => $this->cal->gettext('showalarms'),
+                'value' => $checkbox->show($this->calendar['showalarms'] ? 1 : 0),
+                'id'    => 'calendar-showalarms',
+            ];
+        }
+
+        // allow driver to extend or replace the form content
+        return html::tag('form', $attrib + ['action' => '#', 'method' => 'get', 'id' => 'calendarpropform'],
+            $this->cal->driver->calendar_form($this->action, $this->calendar, $formfields)
+        );
+    }
 
-  /**
-   *
-   */
-  public function calendar_css_classes($id, $prop, $mode, $attrib = array())
-  {
-    $color = $folder_color = $prop['color'];
-
-    // replace white with skin-defined color
-    if (!empty($attrib['folder-fallback-color']) && preg_match('/^f+$/i', $folder_color)) {
-        $folder_color = ltrim($attrib['folder-fallback-color'], '#');
-    }
-
-    $class = 'cal-' . asciiwords($id, true);
-    $css   = str_replace('$class', $class, $attrib['folder-class']) ?: "li .$class";
-    $css  .= " { color: #$folder_color; }\n";
+    /**
+     * Render HTML for attendees table
+     */
+    function attendees_list($attrib = [])
+    {
+        // add "noreply" checkbox to attendees table only
+        $invitations = strpos($attrib['id'], 'attend') !== false;
+
+        $invite = new html_checkbox(['value' => 1, 'id' => 'edit-attendees-invite']);
+        $table  = new html_table(['cols' => 5 + intval($invitations), 'border' => 0, 'cellpadding' => 0, 'class' => 'rectable']);
+
+        $table->add_header('role', $this->cal->gettext('role'));
+        $table->add_header('name', $this->cal->gettext(!empty($attrib['coltitle']) ? $attrib['coltitle'] : 'attendee'));
+        $table->add_header('availability', $this->cal->gettext('availability'));
+        $table->add_header('confirmstate', $this->cal->gettext('confirmstate'));
+
+        if ($invitations) {
+            $table->add_header(['class' => 'invite', 'title' => $this->cal->gettext('sendinvitations')],
+                $invite->show(1)
+                . html::label('edit-attendees-invite', html::span('inner', $this->cal->gettext('sendinvitations')))
+            );
+        }
+
+        $table->add_header('options', '');
+
+        // hide invite column if disabled by config
+        $itip_notify = (int)$this->rc->config->get('calendar_itip_send_option', $this->cal->defaults['calendar_itip_send_option']);
+        if ($invitations && !($itip_notify & 2)) {
+            $css = sprintf('#%s td.invite, #%s th.invite { display:none !important }', $attrib['id'], $attrib['id']);
+            $this->rc->output->add_footer(html::tag('style', ['type' => 'text/css'], $css));
+        }
+
+        return $table->show($attrib);
+    }
 
-    return $css . ".$class .handle { background-color: #$color; }\n";
-  }
+    /**
+     * Render HTML for attendees adding form
+     */
+    function attendees_form($attrib = [])
+    {
+        $input = new html_inputfield([
+                'name'  => 'participant',
+                'id'    => 'edit-attendee-name',
+                'class' => 'form-control'
+        ]);
+        $textarea = new html_textarea([
+                'name'  => 'comment',
+                'id'    => 'edit-attendees-comment',
+                'class' => 'form-control',
+                'rows'  => 4,
+                'cols'  => 55,
+                'title' => $this->cal->gettext('itipcommenttitle')
+        ]);
+
+        return html::div($attrib,
+            html::div('form-searchbar',
+                $input->show()
+                . ' ' .
+                html::tag('input', [
+                        'type'  => 'button',
+                        'class' => 'button',
+                        'id'    => 'edit-attendee-add',
+                        'value' => $this->cal->gettext('addattendee')
+                ])
+                . ' ' .
+                html::tag('input', [
+                        'type'  => 'button',
+                        'class' => 'button',
+                        'id'    => 'edit-attendee-schedule',
+                        'value' => $this->cal->gettext('scheduletime') . '...'
+                ])
+            )
+            . html::p('attendees-commentbox', html::label('edit-attendees-comment', $this->cal->gettext('itipcomment')) . $textarea->show())
+        );
+    }
 
-  /**
-   *
-   */
-  function calendar_list($attrib = array(), $js_only = false)
-  {
-    $html      = '';
-    $jsenv     = array();
-    $tree      = true;
-    $calendars = $this->cal->driver->list_calendars(0, $tree);
-
-    // walk folder tree
-    if (is_object($tree)) {
-      $html = $this->list_tree_html($tree, $calendars, $jsenv, $attrib);
-
-      // append birthdays calendar which isn't part of $tree
-      if ($bdaycal = $calendars[calendar_driver::BIRTHDAY_CALENDAR_ID]) {
-        $calendars = array(calendar_driver::BIRTHDAY_CALENDAR_ID => $bdaycal);
-      }
-      else {
-        $calendars = array();  // clear array for flat listing
-      }
-    }
-    else {
-      // fall-back to flat folder listing
-      $attrib['class'] .= ' flat';
-    }
-
-    foreach ((array)$calendars as $id => $prop) {
-      if ($attrib['activeonly'] && !$prop['active'])
-        continue;
-
-      $html .= html::tag('li', array('id' => 'rcmlical' . $id, 'class' => $prop['group']),
-        $content = $this->calendar_list_item($id, $prop, $jsenv, $attrib['activeonly'])
-      );
-    }
-
-    $this->rc->output->set_env('calendars', $jsenv);
-
-    if ($js_only) {
-      return;
-    }
-
-    $this->rc->output->set_env('source', rcube_utils::get_input_value('source', rcube_utils::INPUT_GET));
-    $this->rc->output->add_gui_object('calendarslist', $attrib['id'] ?: 'unknown');
-
-    return html::tag('ul', $attrib, $html, html::$common_attrib);
-  }
-
-  /**
-   * Return html for a structured list <ul> for the folder tree
-   */
-  public function list_tree_html($node, $data, &$jsenv, $attrib)
-  {
-    $out = '';
-    foreach ($node->children as $folder) {
-      $id = $folder->id;
-      $prop = $data[$id];
-      $is_collapsed = false; // TODO: determine this somehow?
-
-      $content = $this->calendar_list_item($id, $prop, $jsenv, $attrib['activeonly']);
-
-      if (!empty($folder->children)) {
-        $content .= html::tag('ul', array('style' => ($is_collapsed ? "display:none;" : null)),
-          $this->list_tree_html($folder, $data, $jsenv, $attrib));
-      }
-
-      if (strlen($content)) {
-        $out .= html::tag('li', array(
-            'id' => 'rcmlical' . rcube_utils::html_identifier($id),
-            'class' => $prop['group'] . ($prop['virtual'] ? ' virtual' : ''),
-          ),
-          $content);
-      }
-    }
-
-    return $out;
-  }
-
-  /**
-   * Helper method to build a calendar list item (HTML content and js data)
-   */
-  public function calendar_list_item($id, $prop, &$jsenv, $activeonly = false)
-  {
-    // enrich calendar properties with settings from the driver
-    if (!$prop['virtual']) {
-      unset($prop['user_id']);
-      $prop['alarms']      = $this->cal->driver->alarms;
-      $prop['attendees']   = $this->cal->driver->attendees;
-      $prop['freebusy']    = $this->cal->driver->freebusy;
-      $prop['attachments'] = $this->cal->driver->attachments;
-      $prop['undelete']    = $this->cal->driver->undelete;
-      $prop['feedurl']     = $this->cal->get_url(array('_cal' => $this->cal->ical_feed_hash($id) . '.ics', 'action' => 'feed'));
-
-      $jsenv[$id] = $prop;
-    }
-
-    $classes = array('calendar', 'cal-'  . asciiwords($id, true));
-    $title = $prop['title'] ?: ($prop['name'] != $prop['listname'] || strlen($prop['name']) > 25 ?
-      html_entity_decode($prop['name'], ENT_COMPAT, RCUBE_CHARSET) : '');
-
-    if ($prop['virtual'])
-      $classes[] = 'virtual';
-    else if (!$prop['editable'])
-      $classes[] = 'readonly';
-    if ($prop['subscribed'])
-      $classes[] = 'subscribed';
-    if ($prop['subscribed'] === 2)
-      $classes[] = 'partial';
-    if ($prop['class'])
-      $classes[] = $prop['class'];
-
-    $content = '';
-    if (!$activeonly || $prop['active']) {
-      $label_id = 'cl:' . $id;
-      $content = html::div(join(' ', $classes),
-        html::a(array('class' => 'calname', 'id' => $label_id, 'title' => $title, 'href' => '#'), rcube::Q($prop['editname'] ?: $prop['listname']))
-        . ($prop['virtual'] ? '' :
-          html::tag('input', array('type' => 'checkbox', 'name' => '_cal[]', 'value' => $id, 'checked' => $prop['active'], 'aria-labelledby' => $label_id)) .
-          html::span('actions', 
-            ($prop['removable'] ? html::a(array('href' => '#', 'class' => 'remove', 'title' => $this->cal->gettext('removelist')), ' ') : '') .
-            html::a(array('href' => '#', 'class' => 'quickview', 'title' => $this->cal->gettext('quickview'), 'role' => 'checkbox', 'aria-checked' => 'false'), '') .
-            (isset($prop['subscribed']) ? html::a(array('href' => '#', 'class' => 'subscribed', 'title' => $this->cal->gettext('calendarsubscribe'), 'role' => 'checkbox', 'aria-checked' => $prop['subscribed'] ? 'true' : 'false'), ' ') : '')
-          ) .
-          html::span(array('class' => 'handle', 'style' => "background-color: #" . ($prop['color'] ?: 'f00')), '&nbsp;')
-        )
-      );
-    }
-
-    return $content;
-  }
-
-  /**
-   * Render a HTML for agenda options form
-   */
-  function agenda_options($attrib = array())
-  {
-    $attrib += array('id' => 'agendaoptions');
-    $attrib['style'] .= 'display:none';
-
-    $select_range = new html_select(array('name' => 'listrange', 'id' => 'agenda-listrange', 'class' => 'form-control custom-select'));
-    $select_range->add(1 . ' ' . preg_replace('/\(.+\)/', '', $this->cal->lib->gettext('days')), $days);
-    foreach (array(2,5,7,14,30,60,90,180,365) as $days)
-      $select_range->add($days . ' ' . preg_replace('/\(|\)/', '', $this->cal->lib->gettext('days')), $days);
-
-    $html = html::span('input-group',
-        html::label(array('for' => 'agenda-listrange', 'class' => 'input-group-prepend'),
-            html::span('input-group-text', $this->cal->gettext('listrange')))
-        . $select_range->show($this->rc->config->get('calendar_agenda_range', $this->cal->defaults['calendar_agenda_range']))
-    );
-
-    return html::div($attrib, $html);
-  }
-
-  /**
-   * Render a HTML select box for calendar selection
-   */
-  function calendar_select($attrib = array())
-  {
-    $attrib['name']       = 'calendar';
-    $attrib['is_escaped'] = true;
-    $select = new html_select($attrib);
-
-    foreach ((array)$this->cal->driver->list_calendars() as $id => $prop) {
-      if ($prop['editable'] || strpos($prop['rights'], 'i') !== false)
-        $select->add($prop['name'], $id);
-    }
-
-    return $select->show(null);
-  }
-
-  /**
-   * Render a HTML select box for user identity selection
-   */
-  function identity_select($attrib = array())
-  {
-    $attrib['name'] = 'identity';
-    $select         = new html_select($attrib);
-    $identities     = $this->rc->user->list_emails();
-
-    foreach ($identities as $ident) {
-        $select->add(format_email_recipient($ident['email'], $ident['name']), $ident['identity_id']);
-    }
-
-    return $select->show(null);
-  }
-
-  /**
-   * Render a HTML select box to select an event category
-   */
-  function category_select($attrib = array())
-  {
-    $attrib['name'] = 'categories';
-    $select = new html_select($attrib);
-    $select->add('---', '');
-    foreach (array_keys((array)$this->cal->driver->list_categories()) as $cat) {
-      $select->add($cat, $cat);
-    }
-
-    return $select->show(null);
-  }
-
-  /**
-   * Render a HTML select box for status property
-   */
-  function status_select($attrib = array())
-  {
-    $attrib['name'] = 'status';
-    $select = new html_select($attrib);
-    $select->add('---', '');
-    $select->add($this->cal->gettext('status-confirmed'), 'CONFIRMED');
-    $select->add($this->cal->gettext('status-cancelled'), 'CANCELLED');
-    $select->add($this->cal->gettext('status-tentative'), 'TENTATIVE');
-    return $select->show(null);
-  }
-
-  /**
-   * Render a HTML select box for free/busy/out-of-office property
-   */
-  function freebusy_select($attrib = array())
-  {
-    $attrib['name'] = 'freebusy';
-    $select = new html_select($attrib);
-    $select->add($this->cal->gettext('free'), 'free');
-    $select->add($this->cal->gettext('busy'), 'busy');
-    // out-of-office is not supported by libkolabxml (#3220)
-    // $select->add($this->cal->gettext('outofoffice'), 'outofoffice');
-    $select->add($this->cal->gettext('tentative'), 'tentative');
-    return $select->show(null);
-  }
-
-  /**
-   * Render a HTML select for event priorities
-   */
-  function priority_select($attrib = array())
-  {
-    $attrib['name'] = 'priority';
-    $select = new html_select($attrib);
-    $select->add('---', '0');
-    $select->add('1 '.$this->cal->gettext('highest'), '1');
-    $select->add('2 '.$this->cal->gettext('high'),    '2');
-    $select->add('3 ',                                '3');
-    $select->add('4 ',                                '4');
-    $select->add('5 '.$this->cal->gettext('normal'),  '5');
-    $select->add('6 ',                                '6');
-    $select->add('7 ',                                '7');
-    $select->add('8 '.$this->cal->gettext('low'),     '8');
-    $select->add('9 '.$this->cal->gettext('lowest'),  '9');
-    return $select->show(null);
-  }
-  
-  /**
-   * Render HTML input for sensitivity selection
-   */
-  function sensitivity_select($attrib = array())
-  {
-    $attrib['name'] = 'sensitivity';
-    $select = new html_select($attrib);
-    $select->add($this->cal->gettext('public'), 'public');
-    $select->add($this->cal->gettext('private'), 'private');
-    $select->add($this->cal->gettext('confidential'), 'confidential');
-    return $select->show(null);
-  }
-  
-  /**
-   * Render HTML form for alarm configuration
-   */
-  function alarm_select($attrib = array())
-  {
-    return $this->cal->lib->alarm_select($attrib, $this->cal->driver->alarm_types, $this->cal->driver->alarm_absolute);
-  }
-
-  /**
-   * Render HTML for attendee notification warning
-   */
-  function edit_attendees_notify($attrib = array())
-  {
-    $checkbox = new html_checkbox(array('name' => '_notify', 'id' => 'edit-attendees-donotify', 'value' => 1, 'class' => 'pretty-checkbox'));
-    return html::div($attrib, html::label(null, $checkbox->show(1) . ' ' . $this->cal->gettext('sendnotifications')));
-  }
-
-  /**
-   * Render HTML for recurrence option to align start date with the recurrence rule
-   */
-  function edit_recurrence_sync($attrib = array())
-  {
-    $checkbox = new html_checkbox(array('name' => '_start_sync', 'value' => 1, 'class' => 'pretty-checkbox'));
-    return html::div($attrib, html::label(null, $checkbox->show(1) . ' ' . $this->cal->gettext('eventstartsync')));
-  }
-
-  /**
-   * Generate the form for recurrence settings
-   */
-  function recurring_event_warning($attrib = array())
-  {
-    $attrib['id'] = 'edit-recurring-warning';
-
-    $radio = new html_radiobutton(array('name' => '_savemode', 'class' => 'edit-recurring-savemode'));
-    $form = html::label(null, $radio->show('', array('value' => 'current')) . $this->cal->gettext('currentevent')) . ' ' .
-       html::label(null, $radio->show('', array('value' => 'future')) . $this->cal->gettext('futurevents')) . ' ' .
-       html::label(null, $radio->show('all', array('value' => 'all')) . $this->cal->gettext('allevents')) . ' ' .
-       html::label(null, $radio->show('', array('value' => 'new')) . $this->cal->gettext('saveasnew'));
-
-    return html::div($attrib, html::div('message', $this->cal->gettext('changerecurringeventwarning')) . html::div('savemode', $form));
-  }
-
-  /**
-   * Form for uploading and importing events
-   */
-  function events_import_form($attrib = array())
-  {
-    if (!$attrib['id'])
-      $attrib['id'] = 'rcmImportForm';
-
-    // Get max filesize, enable upload progress bar
-    $max_filesize = $this->rc->upload_init();
-
-    $accept = '.ics, text/calendar, text/x-vcalendar, application/ics';
-    if (class_exists('ZipArchive', false)) {
-      $accept .= ', .zip, application/zip';
-    }
-
-    $input = new html_inputfield(array(
-        'id'     => 'importfile',
-        'type'   => 'file',
-        'name'   => '_data',
-        'size'   => $attrib['uploadfieldsize'],
-        'accept' => $accept
-    ));
-
-    $select = new html_select(array('name' => '_range', 'id' => 'event-import-range'));
-    $select->add(array(
-        $this->cal->gettext('onemonthback'),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>2))),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>3))),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>6))),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>12))),
-        $this->cal->gettext('all'),
-      ),
-      array('1','2','3','6','12',0));
-
-    $html = html::div('form-section form-group row',
-      html::label(array('class' => 'col-sm-4 col-form-label', 'for' => 'importfile'), rcube::Q($this->rc->gettext('importfromfile')))
-      . html::div('col-sm-8', $input->show()
-        . html::div('hint', $this->rc->gettext(array('name' => 'maxuploadsize', 'vars' => array('size' => $max_filesize)))))
-    );
-
-    $html .= html::div('form-section form-group row',
-      html::label(array('for' => 'event-import-calendar', 'class' => 'col-form-label col-sm-4'), $this->cal->gettext('calendar'))
-      . html::div('col-sm-8', $this->calendar_select(array('name' => 'calendar', 'id' => 'event-import-calendar')))
-    );
-
-    $html .= html::div('form-section form-group row',
-      html::label(array('for' => 'event-import-range', 'class' => 'col-form-label col-sm-4'), $this->cal->gettext('importrange'))
-      . html::div('col-sm-8', $select->show(1))
-    );
-
-    $this->rc->output->add_gui_object('importform', $attrib['id']);
-    $this->rc->output->add_label('import');
-
-    return html::tag('p', null, $this->cal->gettext('importtext'))
-      . html::tag('form', array(
-          'action'  => $this->rc->url(array('task' => 'calendar', 'action' => 'import_events')),
-          'method'  => 'post',
-          'enctype' => 'multipart/form-data',
-          'id'      => $attrib['id']
-        ), $html);
-  }
-
-  /**
-   * Form to select options for exporting events
-   */
-  function events_export_form($attrib = array())
-  {
-    if (!$attrib['id'])
-      $attrib['id'] = 'rcmExportForm';
-
-    $html = html::div('form-section form-group row',
-      html::label(array('for' => 'event-export-calendar', 'class' => 'col-sm-4 col-form-label'), $this->cal->gettext('calendar'))
-        . html::div('col-sm-8', $this->calendar_select(array('name' => 'calendar', 'id' => 'event-export-calendar', 'class' => 'form-control custom-select'))));
-
-    $select = new html_select(array('name' => 'range', 'id' => 'event-export-range', 'class' => 'form-control custom-select rounded-right'));
-    $select->add(array(
-        $this->cal->gettext('all'),
-        $this->cal->gettext('onemonthback'),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>2))),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>3))),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>6))),
-        $this->cal->gettext(array('name' => 'nmonthsback', 'vars' => array('nr'=>12))),
-        $this->cal->gettext('customdate'),
-      ),
-      array(0,'1','2','3','6','12','custom'));
-
-    $startdate = new html_inputfield(array('name' => 'start', 'size' => 11, 'id' => 'event-export-startdate', 'style' => 'display:none'));
-
-    $html .= html::div('form-section form-group row',
-      html::label(array('for' => 'event-export-range', 'class' => 'col-sm-4 col-form-label'), $this->cal->gettext('exportrange'))
-        . html::div('col-sm-8 input-group', $select->show(0) . $startdate->show()));
-
-    $checkbox = new html_checkbox(array('name' => 'attachments', 'id' => 'event-export-attachments', 'value' => 1, 'class' => 'form-check-input pretty-checkbox'));
-    $html .= html::div('form-section form-check row',
-      html::label(array('for' => 'event-export-attachments', 'class' => 'col-sm-4 col-form-label'), $this->cal->gettext('exportattachments'))
-        . html::div('col-sm-8', $checkbox->show(1)));
-
-    $this->rc->output->add_gui_object('exportform', $attrib['id']);
-
-    return html::tag('form', $attrib + array(
-        'action' => $this->rc->url(array('task' => 'calendar', 'action' => 'export_events')),
-        'method' => "post",
-        'id' => $attrib['id']
-      ),
-      $html
-    );
-  }
-
-  /**
-   * Handler for calendar form template.
-   * The form content could be overriden by the driver
-   */
-  function calendar_editform($action, $calendar = array())
-  {
-    $this->action   = $action;
-    $this->calendar = $calendar;
-
-    // load miniColors js/css files
-    jqueryui::miniColors();
-
-    $this->rc->output->set_env('pagetitle', $this->cal->gettext('calendarprops'));
-    $this->rc->output->add_handler('folderform', array($this, 'calendarform'));
-    $this->rc->output->send('libkolab.folderform');
-  }
-
-  /**
-   * Handler for calendar form template.
-   * The form content could be overriden by the driver
-   */
-  function calendarform($attrib)
-  {
-    // compose default calendar form fields
-    $input_name  = new html_inputfield(array('name' => 'name', 'id' => 'calendar-name', 'size' => 20));
-    $input_color = new html_inputfield(array('name' => 'color', 'id' => 'calendar-color', 'size' => 7, 'class' => 'colors'));
-
-    $formfields = array(
-      'name' => array(
-        'label' => $this->cal->gettext('name'),
-        'value' => $input_name->show($calendar['name']),
-        'id'    => 'calendar-name',
-      ),
-      'color' => array(
-        'label' => $this->cal->gettext('color'),
-        'value' => $input_color->show($calendar['color']),
-        'id'    => 'calendar-color',
-      ),
-    );
-
-    if ($this->cal->driver->alarms) {
-      $checkbox = new html_checkbox(array('name' => 'showalarms', 'id' => 'calendar-showalarms', 'value' => 1));
-      $formfields['showalarms'] = array(
-        'label' => $this->cal->gettext('showalarms'),
-        'value' => $checkbox->show($this->calendar['showalarms'] ? 1 :0),
-        'id'    => 'calendar-showalarms',
-      );
-    }
-
-    // allow driver to extend or replace the form content
-    return html::tag('form', $attrib + array('action' => "#", 'method' => "get", 'id' => 'calendarpropform'),
-      $this->cal->driver->calendar_form($this->action, $this->calendar, $formfields)
-    );
-  }
-
-  /**
-   *
-   */
-  function attendees_list($attrib = array())
-  {
-    // add "noreply" checkbox to attendees table only
-    $invitations = strpos($attrib['id'], 'attend') !== false;
-
-    $invite = new html_checkbox(array('value' => 1, 'id' => 'edit-attendees-invite'));
-    $table  = new html_table(array('cols' => 5 + intval($invitations), 'border' => 0, 'cellpadding' => 0, 'class' => 'rectable'));
-
-    $table->add_header('role', $this->cal->gettext('role'));
-    $table->add_header('name', $this->cal->gettext($attrib['coltitle'] ?: 'attendee'));
-    $table->add_header('availability', $this->cal->gettext('availability'));
-    $table->add_header('confirmstate', $this->cal->gettext('confirmstate'));
-    if ($invitations) {
-      $table->add_header(array('class' => 'invite', 'title' => $this->cal->gettext('sendinvitations')),
-        $invite->show(1) . html::label('edit-attendees-invite', html::span('inner', $this->cal->gettext('sendinvitations'))));
-    }
-    $table->add_header('options', '');
-
-    // hide invite column if disabled by config
-    $itip_notify = (int)$this->rc->config->get('calendar_itip_send_option', $this->cal->defaults['calendar_itip_send_option']);
-    if ($invitations && !($itip_notify & 2)) {
-        $css = sprintf('#%s td.invite, #%s th.invite { display:none !important }', $attrib['id'], $attrib['id']);
-        $this->rc->output->add_footer(html::tag('style', array('type' => 'text/css'), $css));
-    }
-
-    return $table->show($attrib);
-  }
-
-  /**
-   *
-   */
-  function attendees_form($attrib = array())
-  {
-    $input    = new html_inputfield(array('name' => 'participant', 'id' => 'edit-attendee-name', 'class' => 'form-control'));
-    $textarea = new html_textarea(array('name' => 'comment', 'id' => 'edit-attendees-comment', 'class' => 'form-control',
-        'rows' => 4, 'cols' => 55, 'title' => $this->cal->gettext('itipcommenttitle')));
-
-    return html::div($attrib,
-      html::div('form-searchbar', $input->show() . " " .
-        html::tag('input', array('type' => 'button', 'class' => 'button', 'id' => 'edit-attendee-add', 'value' => $this->cal->gettext('addattendee'))) . " " .
-        html::tag('input', array('type' => 'button', 'class' => 'button', 'id' => 'edit-attendee-schedule', 'value' => $this->cal->gettext('scheduletime').'...'))) .
-      html::p('attendees-commentbox', html::label('edit-attendees-comment', $this->cal->gettext('itipcomment')) . $textarea->show())
-    );
-  }
-
-  /**
-   *
-   */
-  function resources_form($attrib = array())
-  {
-    $input = new html_inputfield(array('name' => 'resource', 'id' => 'edit-resource-name', 'class' => 'form-control'));
-
-    return html::div($attrib,
-      html::div('form-searchbar', $input->show() . " " .
-        html::tag('input', array('type' => 'button', 'class' => 'button', 'id' => 'edit-resource-add', 'value' => $this->cal->gettext('addresource'))) . " " .
-        html::tag('input', array('type' => 'button', 'class' => 'button', 'id' => 'edit-resource-find', 'value' => $this->cal->gettext('findresources').'...')))
-      );
-  }
-
-  /**
-   *
-   */
-  function resources_list($attrib = array())
-  {
-    $attrib += array('id' => 'calendar-resources-list');
-
-    $this->rc->output->add_gui_object('resourceslist', $attrib['id']);
-
-    return html::tag('ul', $attrib, '', html::$common_attrib);
-  }
-
-  /**
-   *
-   */
-  public function resource_info($attrib = array())
-  {
-    $attrib += array('id' => 'calendar-resources-info');
-
-    $this->rc->output->add_gui_object('resourceinfo', $attrib['id']);
-    $this->rc->output->add_gui_object('resourceownerinfo', $attrib['id'] . '-owner');
-
-    // copy address book labels for owner details to client
-    $this->rc->output->add_label('name','firstname','surname','department','jobtitle','email','phone','address');
-
-    $table_attrib = array('id','class','style','width','summary','cellpadding','cellspacing','border');
-
-    return html::tag('table', $attrib,
-        html::tag('tbody', null, ''), $table_attrib) .
-
-      html::tag('table', array('id' => $attrib['id'] . '-owner', 'style' => 'display:none') + $attrib,
-        html::tag('thead', null,
-          html::tag('tr', null,
-            html::tag('td', array('colspan' => 2), rcube::Q($this->cal->gettext('resourceowner')))
-          )
-        ) .
-        html::tag('tbody', null, ''),
-        $table_attrib);
-  }
-
-  /**
-   *
-   */
-  public function resource_calendar($attrib = array())
-  {
-    $attrib += array('id' => 'calendar-resources-calendar');
-
-    $this->rc->output->add_gui_object('resourceinfocalendar', $attrib['id']);
-
-    return html::div($attrib, '');
-  }
-
-  /**
-   * GUI object 'searchform' for the resource finder dialog
-   *
-   * @param array Named parameters
-   * @return string HTML code for the gui object
-   */
-  function resources_search_form($attrib)
-  {
-    $attrib += array(
-        'command'       => 'search-resource',
-        'reset-command' => 'reset-resource-search',
-        'id'            => 'rcmcalresqsearchbox',
-        'autocomplete'  => 'off',
-        'form-name'     => 'rcmcalresoursqsearchform',
-        'gui-object'    => 'resourcesearchform',
-    );
-
-    // add form tag around text field
-    return $this->rc->output->search_form($attrib);
-  }
-
-  /**
-   *
-   */
-  function attendees_freebusy_table($attrib = array())
-  {
-    $table = new html_table(array('cols' => 2, 'border' => 0, 'cellspacing' => 0));
-    $table->add('attendees',
-      html::tag('h3', 'boxtitle', $this->cal->gettext('tabattendees')) .
-      html::div('timesheader', '&nbsp;') .
-      html::div(array('id' => 'schedule-attendees-list', 'class' => 'attendees-list'), '')
-    );
-    $table->add('times',
-      html::div('scroll',
-        html::tag('table', array('id' => 'schedule-freebusy-times', 'border' => 0, 'cellspacing' => 0), html::tag('thead') . html::tag('tbody')) .
-        html::div(array('id' => 'schedule-event-time', 'style' => 'display:none'), '&nbsp;')
-      )
-    );
-    
-    return $table->show($attrib);
-  }
-
-  /**
-   *
-   */
-  function event_invitebox($attrib = array())
-  {
-    if ($this->cal->event) {
-      return html::div($attrib,
-        $this->cal->itip->itip_object_details_table($this->cal->event, $this->cal->itip->gettext('itipinvitation')) .
-        $this->cal->invitestatus
-      );
-    }
-    
-    return '';
-  }
-
-  function event_rsvp_buttons($attrib = array())
-  {
-    $actions = array('accepted','tentative','declined');
-    if ($attrib['delegate'] !== 'false')
-      $actions[] = 'delegated';
-
-    return $this->cal->itip->itip_rsvp_buttons($attrib, $actions);
-  }
+    /**
+     * Render HTML for resources adding form
+     */
+    function resources_form($attrib = [])
+    {
+        $input = new html_inputfield(['name' => 'resource', 'id' => 'edit-resource-name', 'class' => 'form-control']);
+
+        return html::div($attrib,
+            html::div('form-searchbar',
+                $input->show()
+                . ' ' .
+                html::tag('input', [
+                        'type'  => 'button',
+                        'class' => 'button',
+                        'id'    => 'edit-resource-add',
+                        'value' => $this->cal->gettext('addresource')
+                ])
+                . ' ' .
+                html::tag('input', [
+                        'type'  => 'button',
+                        'class' => 'button',
+                        'id'    => 'edit-resource-find',
+                        'value' => $this->cal->gettext('findresources') . '...'
+                ])
+            )
+        );
+    }
 
+    /**
+     * Render HTML for resources list
+     */
+    function resources_list($attrib = [])
+    {
+        $attrib += ['id' => 'calendar-resources-list'];
+
+        $this->rc->output->add_gui_object('resourceslist', $attrib['id']);
+
+        return html::tag('ul', $attrib, '', html::$common_attrib);
+    }
+
+    /**
+     *
+     */
+    public function resource_info($attrib = [])
+    {
+        $attrib += ['id' => 'calendar-resources-info'];
+
+        $this->rc->output->add_gui_object('resourceinfo', $attrib['id']);
+        $this->rc->output->add_gui_object('resourceownerinfo', $attrib['id'] . '-owner');
+
+        // copy address book labels for owner details to client
+        $this->rc->output->add_label('name','firstname','surname','department','jobtitle','email','phone','address');
+
+        $table_attrib = ['id','class','style','width','summary','cellpadding','cellspacing','border'];
+
+        return html::tag('table', $attrib, html::tag('tbody', null, ''), $table_attrib)
+            . html::tag('table', ['id' => $attrib['id'] . '-owner', 'style' => 'display:none'] + $attrib,
+                html::tag('thead', null,
+                    html::tag('tr', null,
+                        html::tag('td', ['colspan' => 2], rcube::Q($this->cal->gettext('resourceowner')))
+                    )
+                )
+                . html::tag('tbody', null, ''),
+                $table_attrib
+            );
+    }
+
+    /**
+     *
+     */
+    public function resource_calendar($attrib = [])
+    {
+        $attrib += ['id' => 'calendar-resources-calendar'];
+
+        $this->rc->output->add_gui_object('resourceinfocalendar', $attrib['id']);
+
+        return html::div($attrib, '');
+    }
+
+    /**
+     * GUI object 'searchform' for the resource finder dialog
+     *
+     * @param array $attrib Named parameters
+     *
+     * @return string HTML code for the gui object
+     */
+    function resources_search_form($attrib)
+    {
+        $attrib += [
+            'command'       => 'search-resource',
+            'reset-command' => 'reset-resource-search',
+            'id'            => 'rcmcalresqsearchbox',
+            'autocomplete'  => 'off',
+            'form-name'     => 'rcmcalresoursqsearchform',
+            'gui-object'    => 'resourcesearchform',
+        ];
+
+        // add form tag around text field
+        return $this->rc->output->search_form($attrib);
+    }
+
+    /**
+     *
+     */
+    function attendees_freebusy_table($attrib = [])
+    {
+        $table = new html_table(['cols' => 2, 'border' => 0, 'cellspacing' => 0]);
+        $table->add('attendees',
+            html::tag('h3', 'boxtitle', $this->cal->gettext('tabattendees'))
+            . html::div('timesheader', '&nbsp;')
+            . html::div(['id' => 'schedule-attendees-list', 'class' => 'attendees-list'], '')
+        );
+        $table->add('times',
+            html::div('scroll',
+                html::tag('table', ['id' => 'schedule-freebusy-times', 'border' => 0, 'cellspacing' => 0],
+                    html::tag('thead') . html::tag('tbody')
+                )
+                . html::div(['id' => 'schedule-event-time', 'style' => 'display:none'], '&nbsp;')
+            )
+        );
+
+        return $table->show($attrib);
+    }
+
+    /**
+     *
+     */
+    function event_invitebox($attrib = [])
+    {
+        if (!empty($this->cal->event)) {
+            return html::div($attrib,
+                $this->cal->itip->itip_object_details_table($this->cal->event, $this->cal->itip->gettext('itipinvitation'))
+                . $this->cal->invitestatus
+            );
+        }
+
+        return '';
+    }
+
+    function event_rsvp_buttons($attrib = [])
+    {
+        $actions = ['accepted', 'tentative', 'declined'];
+
+        if (empty($attrib['delegate']) || $attrib['delegate'] !== 'false') {
+            $actions[] = 'delegated';
+        }
+
+        return $this->cal->itip->itip_rsvp_buttons($attrib, $actions);
+    }
 }
diff --git a/plugins/libcalendaring/lib/libcalendaring_itip.php b/plugins/libcalendaring/lib/libcalendaring_itip.php
index 42b6106d..bce19f1a 100644
--- a/plugins/libcalendaring/lib/libcalendaring_itip.php
+++ b/plugins/libcalendaring/lib/libcalendaring_itip.php
@@ -1,999 +1,1002 @@
 <?php
 
 /**
  * iTIP functions for the calendar-based Roudncube plugins
  *
  * Class providing functionality to manage iTIP invitations
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2011-2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 class libcalendaring_itip
 {
     protected $rc;
     protected $lib;
     protected $plugin;
     protected $sender;
     protected $domain;
     protected $itip_send = false;
     protected $rsvp_actions = array('accepted','tentative','declined','delegated');
     protected $rsvp_status  = array('accepted','tentative','declined','delegated');
 
     function __construct($plugin, $domain = 'libcalendaring')
     {
         $this->plugin = $plugin;
         $this->rc = rcube::get_instance();
         $this->lib = libcalendaring::get_instance();
         $this->domain = $domain;
 
         $hook = $this->rc->plugins->exec_hook('calendar_load_itip',
             array('identity' => $this->rc->user->list_emails(true)));
         $this->sender = $hook['identity'];
 
         $this->plugin->add_hook('smtp_connect', array($this, 'smtp_connect_hook'));
     }
 
     public function set_sender_email($email)
     {
         if (!empty($email))
             $this->sender['email'] = $email;
     }
 
     public function set_rsvp_actions($actions)
     {
         $this->rsvp_actions = (array)$actions;
         $this->rsvp_status = array_merge($this->rsvp_actions, array('delegated'));
     }
 
     public function set_rsvp_status($status)
     {
         $this->rsvp_status = $status;
     }
 
     /**
      * Wrapper for rcube_plugin::gettext()
      * Checking for a label in different domains
      *
      * @see rcube::gettext()
      */
     public function gettext($p)
     {
         $label = is_array($p) ? $p['name'] : $p;
         $domain = $this->domain;
         if (!$this->rc->text_exists($label, $domain)) {
             $domain = 'libcalendaring';
         }
         return $this->rc->gettext($p, $domain);
     }
 
     /**
      * Send an iTip mail message
      *
      * @param array   Event object to send
      * @param string  iTip method (REQUEST|REPLY|CANCEL)
      * @param array   Hash array with recipient data (name, email)
      * @param string  Mail subject
      * @param string  Mail body text label
      * @param object  Mail_mime object with message data
      * @param boolean Request RSVP
      * @return boolean True on success, false on failure
      */
     public function send_itip_message($event, $method, $recipient, $subject, $bodytext, $message = null, $rsvp = true)
     {
         if (!$this->sender['name']) {
             $this->sender['name'] = $this->sender['email'];
         }
 
         if (!$message) {
             libcalendaring::identify_recurrence_instance($event);
             $message = $this->compose_itip_message($event, $method, $rsvp);
         }
 
         $mailto = rcube_utils::idn_to_ascii($recipient['email']);
 
         $headers = $message->headers();
         $headers['To'] = format_email_recipient($mailto, $recipient['name']);
         $headers['Subject'] = $this->gettext(array(
             'name' => $subject,
             'vars' => array(
                 'title' => $event['title'],
                 'name' => $this->sender['name'],
             )
         ));
 
         // compose a list of all event attendees
         $attendees_list = array();
         foreach ((array)$event['attendees'] as $attendee) {
             $attendees_list[] = ($attendee['name'] && $attendee['email']) ?
                 $attendee['name'] . ' <' . $attendee['email'] . '>' :
                 ($attendee['name'] ? $attendee['name'] : $attendee['email']);
         }
 
         $recurrence_info = '';
         if (!empty($event['recurrence_id'])) {
             $recurrence_info = "\n\n** " . $this->gettext($event['thisandfuture'] ? 'itipmessagefutureoccurrence' : 'itipmessagesingleoccurrence') . ' **';
         }
         else if (!empty($event['recurrence'])) {
             $recurrence_info = sprintf("\n%s: %s", $this->gettext('recurring'), $this->lib->recurrence_text($event['recurrence']));
         }
 
         $mailbody = $this->gettext(array(
             'name' => $bodytext,
             'vars' => array(
                 'title'       => $event['title'],
                 'date'        => $this->lib->event_date_text($event, true) . $recurrence_info,
                 'attendees'   => join(",\n ", $attendees_list),
                 'sender'      => $this->sender['name'],
                 'organizer'   => $this->sender['name'],
                 'description' => $event['description'],
             )
         ));
 
         // remove redundant empty lines (e.g. when an event description is empty)
         $mailbody = preg_replace('/\n{3,}/', "\n\n", $mailbody);
 
         // if (!empty($event['comment'])) {
         //     $mailbody .= "\n\n" . $this->gettext('itipsendercomment') . $event['comment'];
         // }
 
         // append links for direct invitation replies
         if ($method == 'REQUEST' && $rsvp
             && $this->rc->config->get('calendar_itip_smtp_server')
             && ($token = $this->store_invitation($event, $recipient['email']))
         ) {
             $mailbody .= "\n\n" . $this->gettext(array(
                 'name' => 'invitationattendlinks',
                 'vars' => array('url' => $this->plugin->get_url(array('action' => 'attend', 't' => $token))),
             ));
         }
         else if ($method == 'CANCEL' && $event['cancelled']) {
             $this->cancel_itip_invitation($event);
         }
 
         $message->headers($headers, true);
         $message->setTXTBody(rcube_mime::format_flowed($mailbody, 79));
 
         if ($this->rc->config->get('libcalendaring_itip_debug', false)) {
             rcube::console('iTip ' . $method, $message->txtHeaders() . "\r\n" . $message->get());
         }
 
         // finally send the message
         $this->itip_send = true;
         $sent = $this->rc->deliver_message($message, $headers['X-Sender'], $mailto, $smtp_error);
         $this->itip_send = false;
 
         return $sent;
     }
 
     /**
      * Plugin hook to alter SMTP authentication.
      * This is used if iTip messages are to be sent from an unauthenticated session
      */
     public function smtp_connect_hook($p)
     {
         // replace smtp auth settings if we're not in an authenticated session
         if ($this->itip_send && !$this->rc->user->ID) {
             foreach (array('smtp_server', 'smtp_user', 'smtp_pass') as $prop) {
                 $p[$prop] = $this->rc->config->get("calendar_itip_$prop", $p[$prop]);
             }
         }
 
         return $p;
     }
 
     /**
      * Helper function to build a Mail_mime object to send an iTip message
      *
      * @param array   Event object to send
      * @param string  iTip method (REQUEST|REPLY|CANCEL)
      * @param boolean Request RSVP
      * @return object Mail_mime object with message data
      */
     public function compose_itip_message($event, $method, $rsvp = true)
     {
         $from     = rcube_utils::idn_to_ascii($this->sender['email']);
         $from_utf = rcube_utils::idn_to_utf8($from);
         $sender   = format_email_recipient($from, $this->sender['name']);
 
         // truncate list attendees down to the recipient of the iTip Reply.
         // constraints for a METHOD:REPLY according to RFC 5546
         if ($method == 'REPLY') {
             $replying_attendee = null;
             $reply_attendees = array();
             foreach ($event['attendees'] as $attendee) {
                 if ($attendee['role'] == 'ORGANIZER') {
                     $reply_attendees[] = $attendee;
                 }
                 else if (strcasecmp($attendee['email'], $from) == 0 || strcasecmp($attendee['email'], $from_utf) == 0) {
                     $replying_attendee = $attendee;
                     if ($attendee['status'] != 'DELEGATED') {
                         unset($replying_attendee['rsvp']);  // unset the RSVP attribute
                     }
                 }
                 // include attendees relevant for delegation (RFC 5546, Section 4.2.5)
                 else if ((!empty($attendee['delegated-to']) &&
                             (strcasecmp($attendee['delegated-to'], $from) == 0 || strcasecmp($attendee['delegated-to'], $from_utf) == 0)) ||
                          (!empty($attendee['delegated-from']) &&
                             (strcasecmp($attendee['delegated-from'], $from) == 0 || strcasecmp($attendee['delegated-from'], $from_utf) == 0))) {
                     $reply_attendees[] = $attendee;
                 }
             }
             if ($replying_attendee) {
                 array_unshift($reply_attendees, $replying_attendee);
                 $event['attendees'] = $reply_attendees;
             }
             if ($event['recurrence']) {
                 unset($event['recurrence']['EXCEPTIONS']);
             }
         }
         // set RSVP for every attendee
         else if ($method == 'REQUEST') {
             foreach ($event['attendees'] as $i => $attendee) {
                 if (($rsvp || !isset($attendee['rsvp'])) && ($attendee['status'] != 'DELEGATED' && $attendee['role'] != 'NON-PARTICIPANT')) {
                     $event['attendees'][$i]['rsvp']= (bool)$rsvp;
                 }
             }
         }
         else if ($method == 'CANCEL') {
             if ($event['recurrence']) {
                 unset($event['recurrence']['EXCEPTIONS']);
             }
         }
 
         // Set SENT-BY property if the sender is not the organizer
         if ($method == 'CANCEL' || $method == 'REQUEST') {
             foreach ((array)$event['attendees'] as $idx => $attendee) {
                 if ($attendee['role'] == 'ORGANIZER'
                     && $attendee['email']
                     && strcasecmp($attendee['email'], $from) != 0
                     && strcasecmp($attendee['email'], $from_utf) != 0
                 ) {
                     $attendee['sent-by'] = 'mailto:' . $from_utf;
                     $event['organizer'] = $event['attendees'][$idx] = $attendee;
                     break;
                 }
             }
         }
 
         // compose multipart message using PEAR:Mail_Mime
         $message = new Mail_mime("\r\n");
         $message->setParam('text_encoding', 'quoted-printable');
         $message->setParam('head_encoding', 'quoted-printable');
         $message->setParam('head_charset', RCUBE_CHARSET);
         $message->setParam('text_charset', RCUBE_CHARSET . ";\r\n format=flowed");
         $message->setContentType('multipart/alternative');
 
         // compose common headers array
         $headers = array(
             'From' => $sender,
             'Date' => $this->rc->user_date(),
             'Message-ID' => $this->rc->gen_message_id(),
             'X-Sender' => $from,
         );
         if ($agent = $this->rc->config->get('useragent')) {
             $headers['User-Agent'] = $agent;
         }
 
         $message->headers($headers);
 
         // attach ics file for this event
         $ical = libcalendaring::get_ical();
         $ics = $ical->export(array($event), $method, false, $method == 'REQUEST' && $this->plugin->driver ? array($this->plugin->driver, 'get_attachment_body') : false);
         $filename = $event['_type'] == 'task' ? 'todo.ics' : 'event.ics';
         $message->addAttachment($ics, 'text/calendar', $filename, false, '8bit', '', RCUBE_CHARSET . "; method=" . $method);
 
         return $message;
     }
 
     /**
      * Forward the given iTip event as delegation to another person
      *
      * @param array Event object to delegate
      * @param mixed Delegatee as string or hash array with keys 'name' and 'mailto'
      * @param boolean The delegator's RSVP flag
      * @param array List with indexes of new/updated attendees
      * @return boolean True on success, False on failure
      */
     public function delegate_to(&$event, $delegate, $rsvp = false, &$attendees = array())
     {
         if (is_string($delegate)) {
             $delegates = rcube_mime::decode_address_list($delegate, 1, false);
             if (count($delegates) > 0) {
                 $delegate = reset($delegates);
             }
         }
 
         $emails = $this->lib->get_user_emails();
         $me     = $this->rc->user->list_emails(true);
 
         // find/create the delegate attendee
         $delegate_attendee = array(
             'email' => $delegate['mailto'],
             'name'  => $delegate['name'],
             'role'  => 'REQ-PARTICIPANT',
         );
         $delegate_index = count($event['attendees']);
 
         foreach ($event['attendees'] as $i => $attendee) {
           // set myself the DELEGATED-TO parameter
           if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
               $event['attendees'][$i]['delegated-to'] = $delegate['mailto'];
               $event['attendees'][$i]['status'] = 'DELEGATED';
               $event['attendees'][$i]['role'] = 'NON-PARTICIPANT';
               $event['attendees'][$i]['rsvp'] = $rsvp;
 
               $me['email'] = $attendee['email'];
               $delegate_attendee['role'] = $attendee['role'];
           }
           // the disired delegatee is already listed as an attendee
           else if (stripos($delegate['mailto'], $attendee['email']) !== false && $attendee['role'] != 'ORGANIZER') {
               $delegate_attendee = $attendee;
               $delegate_index = $i;
               break;
           }
           // TODO: remove previous delegatee (i.e. attendee that has DELEGATED-FROM == $me)
         }
 
         // set/add delegate attendee with RSVP=TRUE and DELEGATED-FROM parameter
         $delegate_attendee['rsvp'] = true;
         $delegate_attendee['status'] = 'NEEDS-ACTION';
         $delegate_attendee['delegated-from'] = $me['email'];
         $event['attendees'][$delegate_index] = $delegate_attendee;
 
         $attendees[] = $delegate_index;
 
         $this->set_sender_email($me['email']);
         return $this->send_itip_message($event, 'REQUEST', $delegate_attendee, 'itipsubjectdelegatedto', 'itipmailbodydelegatedto');
     }
 
     /**
      * Handler for calendar/itip-status requests
      */
     public function get_itip_status($event, $existing = null)
     {
         $action = $event['rsvp'] ? 'rsvp' : '';
         $status = $event['fallback'];
         $latest = $rescheduled = false;
         $html   = '';
 
         if (is_numeric($event['changed'])) {
             $event['changed'] = new DateTime('@'.$event['changed']);
         }
 
         // check if the given itip object matches the last state
         if ($existing) {
             $latest = (isset($event['sequence']) && intval($existing['sequence']) == intval($event['sequence'])) ||
                   (!isset($event['sequence']) && $existing['changed'] && $existing['changed'] >= $event['changed']);
         }
 
         // determine action for REQUEST
         if ($event['method'] == 'REQUEST') {
             $html = html::div('rsvp-status', $this->gettext('acceptinvitation'));
 
             if ($existing) {
                 $rsvp   = $event['rsvp'];
                 $emails = $this->lib->get_user_emails();
 
                 foreach ($existing['attendees'] as $attendee) {
                     if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                         $status = strtoupper($attendee['status']);
                         break;
                     }
                 }
             }
             else {
                 $rsvp = $event['rsvp'] && $this->rc->config->get('calendar_allow_itip_uninvited', true);
             }
 
             $status_lc = strtolower($status);
 
             if ($status_lc == 'unknown' && !$this->rc->config->get('calendar_allow_itip_uninvited', true)) {
                 $html = html::div('rsvp-status', $this->gettext('notanattendee'));
                 $action = 'import';
             }
             else if (in_array($status_lc, $this->rsvp_status)) {
                 $status_text = $this->gettext(($latest ? 'youhave' : 'youhavepreviously') . $status_lc);
 
                 if ($existing && ($existing['sequence'] > $event['sequence']
                     || (!isset($event['sequence']) && $existing['changed'] && $existing['changed'] > $event['changed']))
                 ) {
                     $action = '';  // nothing to do here, outdated invitation
                     if ($status_lc == 'needs-action') {
                         $status_text = $this->gettext('outdatedinvitation');
                     }
                 }
                 else if (!$existing && !$rsvp) {
                     $action = 'import';
                 }
                 else {
                     if ($latest) {
                         $diff = $this->get_itip_diff($event, $existing);
 
                         // Detect re-scheduling
                         // FIXME: This is probably to simplistic, or maybe we should just check
                         //        attendee's RSVP flag in the new event?
                         $rescheduled = !empty($diff['start']) || !empty($diff['end']);
                         unset($diff['start'], $diff['end']);
                     }
 
                     if ($rescheduled) {
                         $action = 'rsvp';
                         $latest = false;
                     }
                     else if ($status_lc != 'needs-action') {
                         // check if there are any changes
                         if ($latest) {
                             $latest = empty($diff);
                         }
 
                         $action = !$latest ? 'update' : '';
                     }
                 }
 
                 $html = html::div('rsvp-status ' . $status_lc, $status_text);
             }
         }
         // determine action for REPLY
         else if ($event['method'] == 'REPLY') {
             // check whether the sender already is an attendee
             if ($existing) {
                 // Relax checking if that is a reply to the latest version of the event
                 // We accept versions with older SEQUENCE but no significant changes (Bifrost#T78144)
                 if (!$latest) {
                     $num = $got = 0;
                     foreach (array('start', 'end', 'due', 'allday', 'recurrence', 'location') as $key) {
                         if (isset($existing[$key])) {
                             if ($key == 'allday') {
                                 $event[$key] = $event[$key] == 'true';
                             }
                             $value = $existing[$key] instanceof DateTime ? $existing[$key]->format('c') : $existing[$key];
                             $num++;
                             $got += intval($value == $event[$key]);
                         }
                     }
 
                     $latest = $num === $got;
                 }
 
                 $action = $this->rc->config->get('calendar_allow_itip_uninvited', true) ? 'accept' : '';
                 $listed = false;
 
                 foreach ($existing['attendees'] as $attendee) {
                     if ($attendee['role'] != 'ORGANIZER' && strcasecmp($attendee['email'], $event['attendee']) == 0) {
                         $status_lc = strtolower($status);
                         if (in_array($status_lc, $this->rsvp_status)) {
                             $html = html::div('rsvp-status ' . $status_lc, $this->gettext(array(
                                 'name' => 'attendee' . $status_lc,
                                 'vars' => array(
                                     'delegatedto' => rcube::Q($event['delegated-to'] ?: ($attendee['delegated-to'] ?: '?')),
                                 )
                             )));
                         }
 
                         $action = $attendee['status'] == $status || !$latest ? '' : 'update';
                         $listed = true;
                         break;
                     }
                 }
 
                 if (!$listed) {
                     $html = html::div('rsvp-status', $this->gettext('itipnewattendee'));
                 }
             }
             else {
                 $html   = html::div('rsvp-status hint', $this->gettext('itipobjectnotfound'));
                 $action = '';
             }
         }
         else if ($event['method'] == 'CANCEL') {
             if (!$existing) {
                 $html   = html::div('rsvp-status hint', $this->gettext('itipobjectnotfound'));
                 $action = '';
             }
         }
 
         return array(
             'uid'        => $event['uid'],
             'id'         => asciiwords($event['uid'], true),
             'existing'   => $existing ? true : false,
             'saved'      => $existing ? true : false,
             'latest'     => $latest,
             'status'     => $status,
             'action'     => $action,
             'rescheduled' => $rescheduled,
             'html'       => $html,
         );
     }
 
     protected function get_itip_diff($event, $existing)
     {
         if (empty($event) || empty($existing) || empty($event['message_uid'])) {
             return;
         }
 
         $itip = $this->lib->mail_get_itip_object($event['mbox'], $event['message_uid'], $event['mime_id'],
             $event['task'] == 'calendar' ? 'event' : 'task');
 
         if ($itip) {
             // List of properties that could change without SEQUENCE bump
             $attrs = array('description', 'title', 'location', 'url');
             $diff  = array();
 
             foreach ($attrs as $attr) {
                 if (isset($itip[$attr]) && $itip[$attr] != $existing[$attr]) {
                     $diff[$attr] = array(
                         'new' => $itip[$attr],
                         'old' => $existing[$attr]
                     );
                 }
             }
 
             $status             = array();
             $itip_attendees     = array();
             $existing_attendees = array();
             $emails             = $this->lib->get_user_emails();
 
             // Compare list of attendees (ignoring current user status)
             foreach ((array) $existing['attendees'] as $idx => $attendee) {
                 if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                     $status[strtolower($attendee['email'])] = $attendee['status'];
                 }
                 if ($attendee['role'] == 'ORGANIZER') {
                     $attendee['status'] = 'ACCEPTED'; // sometimes is not set for exceptions
                     $existing['attendees'][$idx] = $attendee;
                 }
                 $existing_attendees[] = $attendee['email'].$attendee['name'];
             }
             foreach ((array) $itip['attendees'] as $idx => $attendee) {
                 if ($attendee['email'] && ($_status = $status[strtolower($attendee['email'])])) {
                     $attendee['status'] = $_status;
                     $itip['attendees'][$idx] = $attendee;
                 }
                 $itip_attendees[] = $attendee['email'].$attendee['name'];
             }
 
             if ($itip_attendees != $existing_attendees) {
                 $diff['attendees'] = array(
                     'new' => $itip['attendees'],
                     'old' => $existing['attendees']
                 );
             }
 
             if ($existing['start'] != $itip['start']) {
                 $diff['start'] = array(
                     'new' => $itip['start'],
                     'old' => $existing['start'],
                 );
             }
 
             if ($existing['end'] != $itip['end']) {
                 $diff['end'] = array(
                     'new' => $itip['end'],
                     'old' => $existing['end'],
                 );
             }
 
             return $diff;
         }
     }
 
     /**
      * Build inline UI elements for iTip messages
      */
     public function mail_itip_inline_ui($event, $method, $mime_id, $task, $message_date = null, $preview_url = null)
     {
         $buttons = array();
         $dom_id = asciiwords($event['uid'], true);
         $rsvp_status = 'unknown';
 
         // pass some metadata about the event and trigger the asynchronous status check
         $changed = is_object($event['changed']) ? $event['changed'] : $message_date;
         $metadata = array(
             'uid'      => $event['uid'],
             '_instance' => $event['_instance'],
             'changed'  => $changed ? $changed->format('U') : 0,
             'sequence' => intval($event['sequence']),
             'method'   => $method,
             'task'     => $task,
             'mime_id'  => $mime_id,
         );
 
         // create buttons to be activated from async request checking existence of this event in local calendars
         $buttons[] = html::div(array('id' => 'loading-'.$dom_id, 'class' => 'rsvp-status loading'), $this->gettext('loading'));
 
         // on iTip REPLY we have two options:
         if ($method == 'REPLY') {
             $title = $this->gettext('itipreply');
 
             foreach ($event['attendees'] as $attendee) {
                 if (!empty($attendee['email']) && $attendee['role'] != 'ORGANIZER') {
                     if (empty($event['_sender']) || self::compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                         $metadata['attendee'] = $attendee['email'];
                         $rsvp_status = strtoupper($attendee['status']);
                         if ($attendee['delegated-to']) {
                             $metadata['delegated-to'] = $attendee['delegated-to'];
                         }
                         break;
                     }
                 }
             }
 
             // It may happen that sender's address is different in From: and the attached iTip
             // In such case use the ATTENDEE entry with the address from From: header
             if (empty($metadata['attendee']) && !empty($event['_sender'])) {
                 // remove the organizer
                 $itip_attendees = array_filter($event['attendees'], function($item) { return $item['role'] != 'ORGANIZER'; });
 
                 // there must be only one attendee
                 if (is_array($itip_attendees) && count($itip_attendees) == 1) {
                     $event_attendee       = $itip_attendees[key($itip_attendees)];
                     $metadata['attendee'] = $event['_sender'];
                     $rsvp_status          = strtoupper($event_attendee['status']);
                 }
             }
 
             // 1. update the attendee status on our copy
             $update_button = html::tag('input', array(
                 'type'    => 'button',
                 'class'   => 'button',
                 'onclick' => "rcube_libcalendaring.add_from_itip_mail('" . rcube::JQ($mime_id) . "', '$task')",
                 'value'   => $this->gettext('updateattendeestatus'),
             ));
 
             // 2. accept or decline a new or delegate attendee
             $accept_buttons = html::tag('input', array(
                 'type'    => 'button',
                 'class'   => "button accept",
                 'onclick' => "rcube_libcalendaring.add_from_itip_mail('" . rcube::JQ($mime_id) . "', '$task')",
                 'value'   => $this->gettext('acceptattendee'),
             ));
             $accept_buttons .= html::tag('input', array(
                 'type'    => 'button',
                 'class'   => "button decline",
                 'onclick' => "rcube_libcalendaring.decline_attendee_reply('" . rcube::JQ($mime_id) . "', '$task')",
                 'value'   => $this->gettext('declineattendee'),
             ));
 
             $buttons[] = html::div(array('id' => 'update-'.$dom_id, 'style' => 'display:none'), $update_button);
             $buttons[] = html::div(array('id' => 'accept-'.$dom_id, 'style' => 'display:none'), $accept_buttons);
 
             // For replies we need more metadata
             foreach (array('start', 'end', 'due', 'allday', 'recurrence', 'location') as $key) {
                 if (isset($event[$key])) {
                     $metadata[$key] = $event[$key] instanceof DateTime ? $event[$key]->format('c') : $event[$key];
                 }
             }
         }
         // when receiving iTip REQUEST messages:
         else if ($method == 'REQUEST') {
             $emails = $this->lib->get_user_emails();
             $title = $event['sequence'] > 0 ? $this->gettext('itipupdate') : $this->gettext('itipinvitation');
             $metadata['rsvp'] = true;
             $metadata['sensitivity'] = $event['sensitivity'];
 
             if (is_object($event['start'])) {
                 $metadata['date'] = $event['start']->format('U');
             }
 
             // check for X-KOLAB-INVITATIONTYPE property and only show accept/decline buttons
             if (self::get_custom_property($event, 'X-KOLAB-INVITATIONTYPE') == 'CONFIRMATION') {
                 $this->rsvp_actions = array('accepted','declined');
                 $metadata['nosave'] = true;
             }
 
             // 1. display RSVP buttons (if the user was invited)
             foreach ($this->rsvp_actions as $method) {
                 $rsvp_buttons .= html::tag('input', array(
                     'type'    => 'button',
                     'class'   => "button $method",
                     'onclick' => "rcube_libcalendaring.add_from_itip_mail('" . rcube::JQ($mime_id) . "', '$task', '$method', '$dom_id')",
                     'value'   => $this->gettext('itip' . $method),
                 ));
             }
 
             // add button to open calendar/preview
             if (!empty($preview_url)) {
                 $msgref = $this->lib->ical_message->folder . '/' . $this->lib->ical_message->uid . '#' . $mime_id;
                 $rsvp_buttons .= html::tag('input', array(
                     'type'    => 'button',
                     // TODO: Temp. disable this button on small screen in Elastic (Bifrost#T105747)
                     'class'   => "button preview hidden-phone hidden-small",
                     'onclick' => "rcube_libcalendaring.open_itip_preview('" . rcube::JQ($preview_url) . "', '" . rcube::JQ($msgref) . "')",
                     'value'   => $this->gettext('openpreview'),
                 ));
             }
 
             // 2. update the local copy with minor changes
             $update_button = html::tag('input', array(
                 'type'    => 'button',
                 'class'   => 'button',
                 'onclick' => "rcube_libcalendaring.add_from_itip_mail('" . rcube::JQ($mime_id) . "', '$task')",
                 'value'   => $this->gettext('updatemycopy'),
             ));
 
             // 3. Simply import the event without replying
             $import_button = html::tag('input', array(
                 'type'    => 'button',
                 'class'   => 'button',
                 'onclick' => "rcube_libcalendaring.add_from_itip_mail('" . rcube::JQ($mime_id) . "', '$task')",
                 'value'   => $this->gettext('importtocalendar'),
             ));
 
             // check my status as an attendee
             foreach ($event['attendees'] as $attendee) {
                 if ($attendee['email'] && $attendee['role'] != 'ORGANIZER' && in_array(strtolower($attendee['email']), $emails)) {
                     $metadata['attendee'] = $attendee['email'];
                     $metadata['rsvp']     = $attendee['rsvp'] || $attendee['role'] != 'NON-PARTICIPANT';
                     $rsvp_status = !empty($attendee['status']) ? strtoupper($attendee['status']) : 'NEEDS-ACTION';
                     break;
                 }
             }
 
             // add itip reply message controls
             $rsvp_buttons .= html::div('itip-reply-controls', $this->itip_rsvp_options_ui($dom_id, $metadata['nosave']));
 
             $buttons[] = html::div(array('id' => 'rsvp-'.$dom_id, 'class' => 'rsvp-buttons', 'style' => 'display:none'), $rsvp_buttons);
             $buttons[] = html::div(array('id' => 'update-'.$dom_id, 'style' => 'display:none'), $update_button);
 
             // prepare autocompletion for delegation dialog
             if (in_array('delegated', $this->rsvp_actions)) {
                 $this->rc->autocomplete_init();
             }
         }
         // for CANCEL messages, we can:
         else if ($method == 'CANCEL') {
             $title = $this->gettext('itipcancellation');
             $event_prop = array_filter(array(
                 'uid'       => $event['uid'],
                 '_instance' => $event['_instance'],
                 '_savemode' => $event['_savemode'],
             ));
 
             // 1. remove the event from our calendar
             $button_remove = html::tag('input', array(
                 'type' => 'button',
                 'class' => 'button',
                 'onclick' => "rcube_libcalendaring.remove_from_itip(" . rcube_output::json_serialize($event_prop) . ", '$task', '" . rcube::JQ($event['title']) . "')",
                 'value' => $this->gettext('removefromcalendar'),
             ));
 
             // 2. update our copy with status=cancelled
             $button_update = html::tag('input', array(
                 'type'    => 'button',
                 'class'   => 'button',
                 'onclick' => "rcube_libcalendaring.add_from_itip_mail('" . rcube::JQ($mime_id) . "', '$task')",
                 'value'   => $this->gettext('updatemycopy'),
             ));
 
             $buttons[] = html::div(array('id' => 'rsvp-'.$dom_id, 'style' => 'display:none'), $button_remove . $button_update);
 
             $rsvp_status = 'CANCELLED';
             $metadata['rsvp'] = true;
         }
 
         // append generic import button
         if ($import_button) {
             $buttons[] = html::div(array('id' => 'import-'.$dom_id, 'style' => 'display:none'), $import_button);
         }
 
         // pass some metadata about the event and trigger the asynchronous status check
         $metadata['fallback'] = $rsvp_status;
         $metadata['rsvp'] = intval($metadata['rsvp']);
 
         $this->rc->output->add_script("rcube_libcalendaring.fetch_itip_object_status(" . rcube_output::json_serialize($metadata) . ")", 'docready');
 
         // get localized texts from the right domain
         foreach (array('savingdata','deleteobjectconfirm','declinedeleteconfirm','declineattendee',
             'cancel','itipdelegated','declineattendeeconfirm','itipcomment','delegateinvitation',
             'delegateto','delegatersvpme','delegateinvalidaddress') as $label) {
             $this->rc->output->command('add_label', "itip.$label", $this->gettext($label));
         }
 
         // show event details with buttons
         return $this->itip_object_details_table($event, $title) .
             html::div(array('class' => 'itip-buttons', 'id' => 'itip-buttons-' . asciiwords($metadata['uid'], true)), join('', $buttons));
     }
 
     /**
      * Render an RSVP UI widget with buttons to respond on iTip invitations
      */
     function itip_rsvp_buttons($attrib = array(), $actions = null)
     {
         $attrib += array('type' => 'button');
 
-        if (!$actions)
+        if (!$actions) {
             $actions = $this->rsvp_actions;
+        }
+
+        $buttons = '';
 
         foreach ($actions as $method) {
             $buttons .= html::tag('input', array(
                 'type'  => $attrib['type'],
-                'name'  => $attrib['iname'],
+                'name'  => !empty($attrib['iname']) ? $attrib['iname'] : null,
                 'class' => 'button',
                 'rel'   => $method,
                 'value' => $this->gettext('itip' . $method),
             ));
         }
 
         // add localized texts for the delegation dialog
         if (in_array('delegated', $actions)) {
             foreach (array('itipdelegated','itipcomment','delegateinvitation',
                   'delegateto','delegatersvpme','delegateinvalidaddress','cancel') as $label) {
                 $this->rc->output->command('add_label', "itip.$label", $this->gettext($label));
             }
         }
 
         foreach (array('all','current','future') as $mode) {
             $this->rc->output->command('add_label', "rsvpmode$mode", $this->gettext("rsvpmode$mode"));
         }
 
         $savemode_radio = new html_radiobutton(array('name' => '_rsvpmode', 'class' => 'rsvp-replymode'));
 
         return html::div($attrib,
             html::div('label', $this->gettext('acceptinvitation')) .
             html::div('rsvp-buttons itip-buttons',
                 $buttons .
                 html::div('itip-reply-controls', $this->itip_rsvp_options_ui($attrib['id']))
             )
         );
     }
 
     /**
      * Render UI elements to control iTip reply message sending
      */
     public function itip_rsvp_options_ui($dom_id, $disable = false)
     {
         $itip_sending = $this->rc->config->get('calendar_itip_send_option', 3);
 
         // itip sending is entirely disabled
         if ($itip_sending === 0) {
             return '';
         }
         // add checkbox to suppress itip reply message
         else if ($itip_sending >= 2) {
             $toggle_attrib = array(
                 'type'     => 'checkbox',
                 'id'       => 'noreply-'.$dom_id,
                 'value'    => 1,
                 'disabled' => $disable,
                 'checked'  => ($itip_sending & 1) == 0,
                 'class'    => 'pretty-checkbox',
             );
             $rsvp_additions = html::label(array('class' => 'noreply-toggle'),
                 html::tag('input', $toggle_attrib) . ' ' . $this->gettext('itipsuppressreply')
             );
         }
 
         // add input field for reply comment
         $toggle_attrib = array(
             'href'    => '#toggle',
             'class'   => 'reply-comment-toggle',
             'onclick' => '$(this).hide().parent().find(\'textarea\').show().focus()'
         );
         $textarea_attrib = array(
             'id'    => 'reply-comment-' . $dom_id,
             'name'  => '_comment',
             'cols'  => 40,
             'rows'  => 4,
             'class' => 'form-control',
             'style' => 'display:none',
             'placeholder' => $this->gettext('itipcomment')
         );
 
         $rsvp_additions .= html::a($toggle_attrib, $this->gettext('itipeditresponse'))
             . html::div('itip-reply-comment', html::tag('textarea', $textarea_attrib, ''));
 
         return $rsvp_additions;
     }
 
     /**
      * Render event/task details in a table
      */
     function itip_object_details_table($event, $title)
     {
         $table = new html_table(array('cols' => 2, 'border' => 0, 'class' => 'calendar-eventdetails'));
         $table->add('ititle', $title);
         $table->add('title', rcube::Q(trim($event['title'])));
         if ($event['start'] && $event['end']) {
             $table->add('label', $this->gettext('date'));
             $table->add('date', rcube::Q($this->lib->event_date_text($event)));
         }
         else if ($event['due'] && $event['_type'] == 'task') {
             $table->add('label', $this->gettext('date'));
             $table->add('date', rcube::Q($this->lib->event_date_text($event)));
         }
         if (!empty($event['recurrence_date'])) {
             $table->add('label', '');
             $table->add('recurrence-id', $this->gettext($event['thisandfuture'] ? 'itipfutureoccurrence' : 'itipsingleoccurrence'));
         }
         else if (!empty($event['recurrence'])) {
             $table->add('label', $this->gettext('recurring'));
             $table->add('recurrence', $this->lib->recurrence_text($event['recurrence']));
         }
         if ($location = trim($event['location'])) {
             $table->add('label', $this->gettext('location'));
             $table->add('location', rcube::Q($location));
         }
         if (($sensitivity = trim($event['sensitivity'])) && !preg_match('/^(x-|public$)/i', $sensitivity)) {
             $table->add('label', $this->gettext('sensitivity'));
             $table->add('sensitivity', ucfirst($this->gettext($sensitivity)) . '!');
         }
         if ($event['status'] == 'COMPLETED' || $event['status'] == 'CANCELLED') {
             $table->add('label', $this->gettext('status'));
             $table->add('status', $this->gettext('status-' . strtolower($event['status'])));
         }
         if ($comment = trim($event['comment'])) {
             $table->add('label', $this->gettext('comment'));
             $table->add('location', rcube::Q($comment));
         }
 
         return $table->show();
     }
 
 
     /**
      * Create iTIP invitation token for later replies via URL
      *
      * @param array Hash array with event properties
      * @param string Attendee email address
      * @return string Invitation token
      */
     public function store_invitation($event, $attendee)
     {
         // empty stub
         return false;
     }
 
     /**
      * Mark invitations for the given event as cancelled
      *
      * @param array Hash array with event properties
      */
     public function cancel_itip_invitation($event)
     {
         // empty stub
         return false;
     }
 
     /**
      * Utility function to get the value of a custom property
      */
     public static function get_custom_property($event, $name)
     {
       $ret = false;
 
       if (is_array($event['x-custom'])) {
           array_walk($event['x-custom'], function($prop, $i) use ($name, &$ret) {
               if (strcasecmp($prop[0], $name) === 0) {
                   $ret = $prop[1];
               }
           });
       }
 
       return $ret;
     }
 
     /**
      * Compare email address
      */
     public static function compare_email($value, $email, $email_utf = null)
     {
         $v1 = !empty($email) && strcasecmp($value, $email) === 0;
         $v2 = !empty($email_utf) && strcasecmp($value, $email_utf) === 0;
 
         return $v1 || $v2;
     }
 }
diff --git a/plugins/libcalendaring/libcalendaring.php b/plugins/libcalendaring/libcalendaring.php
index 379bd945..c8098a01 100644
--- a/plugins/libcalendaring/libcalendaring.php
+++ b/plugins/libcalendaring/libcalendaring.php
@@ -1,1551 +1,1554 @@
 <?php
 
 /**
  * Library providing common functions for calendaring plugins
  *
  * Provides utility functions for calendar-related modules such as
  * - alarms display and dismissal
  * - attachment handling
  * - recurrence computation and UI elements
  * - ical parsing and exporting
  * - itip scheduling protocol
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class libcalendaring extends rcube_plugin
 {
     public $rc;
     public $timezone;
     public $gmt_offset;
     public $dst_active;
     public $timezone_offset;
     public $ical_parts = array();
     public $ical_message;
 
     public $defaults = array(
-      'calendar_date_format'  => "Y-m-d",
-      'calendar_date_short'   => "M-j",
-      'calendar_date_long'    => "F j Y",
-      'calendar_date_agenda'  => "l M-d",
-      'calendar_time_format'  => "H:m",
-      'calendar_first_day'    => 1,
-      'calendar_first_hour'   => 6,
-      'calendar_date_format_sets' => array(
-        'Y-m-d' => array('d M Y',   'm-d',  'l m-d'),
-        'Y/m/d' => array('d M Y',   'm/d',  'l m/d'),
-        'Y.m.d' => array('d M Y',   'm.d',  'l m.d'),
-        'd-m-Y' => array('d M Y',   'd-m',  'l d-m'),
-        'd/m/Y' => array('d M Y',   'd/m',  'l d/m'),
-        'd.m.Y' => array('d M Y',  'd.m',  'l d.m'),
-        'j.n.Y' => array('d M Y',  'd.m',  'l d.m'),
-        'm/d/Y' => array('M d Y',   'm/d',  'l m/d'),
-      ),
+        'calendar_date_format'  => "Y-m-d",
+        'calendar_date_short'   => "M-j",
+        'calendar_date_long'    => "F j Y",
+        'calendar_date_agenda'  => "l M-d",
+        'calendar_time_format'  => "H:m",
+        'calendar_first_day'    => 1,
+        'calendar_first_hour'   => 6,
+        'calendar_date_format_sets' => array(
+            'Y-m-d' => array('d M Y',   'm-d',  'l m-d'),
+            'Y/m/d' => array('d M Y',   'm/d',  'l m/d'),
+            'Y.m.d' => array('d M Y',   'm.d',  'l m.d'),
+            'd-m-Y' => array('d M Y',   'd-m',  'l d-m'),
+            'd/m/Y' => array('d M Y',   'd/m',  'l d/m'),
+            'd.m.Y' => array('d M Y',  'd.m',  'l d.m'),
+            'j.n.Y' => array('d M Y',  'd.m',  'l d.m'),
+            'm/d/Y' => array('M d Y',   'm/d',  'l m/d'),
+        ),
     );
 
     private static $instance;
 
     private $mail_ical_parser;
 
     /**
      * Singleton getter to allow direct access from other plugins
      */
     public static function get_instance()
     {
         if (!self::$instance) {
             self::$instance = new libcalendaring(rcube::get_instance()->plugins);
             self::$instance->init_instance();
         }
 
         return self::$instance;
     }
 
     /**
      * Initializes class properties
      */
     public function init_instance()
     {
         $this->rc = rcube::get_instance();
 
         // set user's timezone
         try {
             $this->timezone = new DateTimeZone($this->rc->config->get('timezone', 'GMT'));
         }
         catch (Exception $e) {
             $this->timezone = new DateTimeZone('GMT');
         }
 
         $now = new DateTime('now', $this->timezone);
 
         $this->gmt_offset      = $now->getOffset();
         $this->dst_active      = $now->format('I');
         $this->timezone_offset = $this->gmt_offset / 3600 - $this->dst_active;
 
         $this->add_texts('localization/', false);
     }
 
     /**
      * Required plugin startup method
      */
     public function init()
     {
         self::$instance = $this;
 
         $this->rc = rcube::get_instance();
         $this->init_instance();
 
         // include client scripts and styles
         if ($this->rc->output) {
             // add hook to display alarms
             $this->add_hook('refresh', array($this, 'refresh'));
             $this->register_action('plugin.alarms', array($this, 'alarms_action'));
             $this->register_action('plugin.expand_attendee_group', array($this, 'expand_attendee_group'));
         }
 
         // proceed initialization in startup hook
         $this->add_hook('startup', array($this, 'startup'));
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         if ($this->rc->output && $this->rc->output->type == 'html') {
             $this->rc->output->set_env('libcal_settings', $this->load_settings());
             $this->include_script('libcalendaring.js');
             $this->include_stylesheet($this->local_skin_path() . '/libcal.css');
 
             $this->add_label(
                 'itipaccepted', 'itiptentative', 'itipdeclined',
                 'itipdelegated', 'expandattendeegroup', 'expandattendeegroupnodata',
                 'statusorganizer', 'statusaccepted', 'statusdeclined',
                 'statusdelegated', 'statusunknown', 'statusneeds-action',
                 'statustentative', 'statuscompleted', 'statusin-process',
                 'delegatedto', 'delegatedfrom', 'showmore'
             );
         }
 
         if ($args['task'] == 'mail') {
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 $this->add_hook('message_load', array($this, 'mail_message_load'));
             }
         }
     }
 
     /**
      * Load iCalendar functions
      */
     public static function get_ical()
     {
         $self = self::get_instance();
         require_once __DIR__ . '/libvcalendar.php';
         return new libvcalendar();
     }
 
     /**
      * Load iTip functions
      */
     public static function get_itip($domain = 'libcalendaring')
     {
         $self = self::get_instance();
         require_once __DIR__ . '/lib/libcalendaring_itip.php';
         return new libcalendaring_itip($self, $domain);
     }
 
     /**
      * Load recurrence computation engine
      */
     public static function get_recurrence()
     {
         $self = self::get_instance();
         require_once __DIR__ . '/lib/libcalendaring_recurrence.php';
         return new libcalendaring_recurrence($self);
     }
 
     /**
      * Shift dates into user's current timezone
      *
      * @param mixed Any kind of a date representation (DateTime object, string or unix timestamp)
      * @return object DateTime object in user's timezone
      */
     public function adjust_timezone($dt, $dateonly = false)
     {
-        if (is_numeric($dt))
+        if (is_numeric($dt)) {
             $dt = new DateTime('@'.$dt);
-        else if (is_string($dt))
+        }
+        else if (is_string($dt)) {
             $dt = rcube_utils::anytodatetime($dt);
+        }
 
         if ($dt instanceof DateTime && !($dt->_dateonly || $dateonly)) {
             $dt->setTimezone($this->timezone);
         }
 
         return $dt;
     }
 
-
     /**
      *
      */
     public function load_settings()
     {
         $this->date_format_defaults();
 
         $settings = array();
         $keys     = array('date_format', 'time_format', 'date_short', 'date_long', 'date_agenda');
 
         foreach ($keys as $key) {
             $settings[$key] = (string)$this->rc->config->get('calendar_' . $key, $this->defaults['calendar_' . $key]);
             $settings[$key] = self::from_php_date_format($settings[$key]);
         }
 
         $settings['dates_long']  = $settings['date_long'];
         $settings['first_day']   = (int)$this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
         $settings['timezone']    = $this->timezone_offset;
         $settings['dst']         = $this->dst_active;
 
         // localization
         $settings['days'] = array(
             $this->rc->gettext('sunday'),   $this->rc->gettext('monday'),
             $this->rc->gettext('tuesday'),  $this->rc->gettext('wednesday'),
             $this->rc->gettext('thursday'), $this->rc->gettext('friday'),
             $this->rc->gettext('saturday')
         );
         $settings['days_short'] = array(
             $this->rc->gettext('sun'), $this->rc->gettext('mon'),
             $this->rc->gettext('tue'), $this->rc->gettext('wed'),
             $this->rc->gettext('thu'), $this->rc->gettext('fri'),
             $this->rc->gettext('sat')
         );
         $settings['months'] = array(
             $this->rc->gettext('longjan'), $this->rc->gettext('longfeb'),
             $this->rc->gettext('longmar'), $this->rc->gettext('longapr'),
             $this->rc->gettext('longmay'), $this->rc->gettext('longjun'),
             $this->rc->gettext('longjul'), $this->rc->gettext('longaug'),
             $this->rc->gettext('longsep'), $this->rc->gettext('longoct'),
             $this->rc->gettext('longnov'), $this->rc->gettext('longdec')
         );
         $settings['months_short'] = array(
             $this->rc->gettext('jan'), $this->rc->gettext('feb'),
             $this->rc->gettext('mar'), $this->rc->gettext('apr'),
             $this->rc->gettext('may'), $this->rc->gettext('jun'),
             $this->rc->gettext('jul'), $this->rc->gettext('aug'),
             $this->rc->gettext('sep'), $this->rc->gettext('oct'),
             $this->rc->gettext('nov'), $this->rc->gettext('dec')
         );
         $settings['today'] = $this->rc->gettext('today');
 
         return $settings;
     }
 
 
     /**
      * Helper function to set date/time format according to config and user preferences
      */
     private function date_format_defaults()
     {
         static $defaults = array();
 
         // nothing to be done
         if (isset($defaults['date_format']))
           return;
 
         $defaults['date_format'] = $this->rc->config->get('calendar_date_format', $this->rc->config->get('date_format'));
         $defaults['time_format'] = $this->rc->config->get('calendar_time_format', $this->rc->config->get('time_format'));
 
         // override defaults
         if ($defaults['date_format'])
             $this->defaults['calendar_date_format'] = $defaults['date_format'];
         if ($defaults['time_format'])
             $this->defaults['calendar_time_format'] = $defaults['time_format'];
 
         // derive format variants from basic date format
         $format_sets = $this->rc->config->get('calendar_date_format_sets', $this->defaults['calendar_date_format_sets']);
         if ($format_set = $format_sets[$this->defaults['calendar_date_format']]) {
             $this->defaults['calendar_date_long'] = $format_set[0];
             $this->defaults['calendar_date_short'] = $format_set[1];
             $this->defaults['calendar_date_agenda'] = $format_set[2];
         }
     }
 
     /**
      * Compose a date string for the given event
      */
     public function event_date_text($event, $tzinfo = false)
     {
         $fromto = '--';
 
         // handle task objects
         if ($event['_type'] == 'task' && is_object($event['due'])) {
             $date_format = $event['due']->_dateonly ? self::to_php_date_format($this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format'])) : null;
             $fromto = $this->rc->format_date($event['due'], $date_format, false);
 
             // add timezone information
             if ($fromto && $tzinfo && ($tzname = $this->timezone->getName())) {
                 $fromto .= ' (' . strtr($tzname, '_', ' ') . ')';
             }
 
             return $fromto;
         }
 
         // abort if no valid event dates are given
         if (!is_object($event['start']) || !is_a($event['start'], 'DateTime') || !is_object($event['end']) || !is_a($event['end'], 'DateTime')) {
             return $fromto;
         }
 
         $duration = $event['start']->diff($event['end'])->format('s');
 
         $this->date_format_defaults();
         $date_format = self::to_php_date_format($this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format']));
         $time_format = self::to_php_date_format($this->rc->config->get('calendar_time_format', $this->defaults['calendar_time_format']));
 
         if ($event['allday']) {
             $fromto = $this->rc->format_date($event['start'], $date_format, false);
             if (($todate = $this->rc->format_date($event['end'], $date_format, false)) != $fromto)
                 $fromto .= ' - ' . $todate;
         }
         else if ($duration < 86400 && $event['start']->format('d') == $event['end']->format('d')) {
             $fromto = $this->rc->format_date($event['start'], $date_format) . ' ' . $this->rc->format_date($event['start'], $time_format) .
                 ' - ' . $this->rc->format_date($event['end'], $time_format);
         }
         else {
             $fromto = $this->rc->format_date($event['start'], $date_format) . ' ' . $this->rc->format_date($event['start'], $time_format) .
                 ' - ' . $this->rc->format_date($event['end'], $date_format) . ' ' . $this->rc->format_date($event['end'], $time_format);
         }
 
         // add timezone information
         if ($tzinfo && ($tzname = $this->timezone->getName())) {
             $fromto .= ' (' . strtr($tzname, '_', ' ') . ')';
         }
 
         return $fromto;
     }
 
 
     /**
      * Render HTML form for alarm configuration
      */
     public function alarm_select($attrib, $alarm_types, $absolute_time = true)
     {
         unset($attrib['name']);
 
         $input_value    = new html_inputfield(array('name' => 'alarmvalue[]', 'class' => 'edit-alarm-value form-control', 'size' => 3));
         $input_date     = new html_inputfield(array('name' => 'alarmdate[]', 'class' => 'edit-alarm-date form-control', 'size' => 10));
         $input_time     = new html_inputfield(array('name' => 'alarmtime[]', 'class' => 'edit-alarm-time form-control', 'size' => 6));
         $select_type    = new html_select(array('name' => 'alarmtype[]', 'class' => 'edit-alarm-type form-control', 'id' => $attrib['id']));
         $select_offset  = new html_select(array('name' => 'alarmoffset[]', 'class' => 'edit-alarm-offset form-control'));
         $select_related = new html_select(array('name' => 'alarmrelated[]', 'class' => 'edit-alarm-related form-control'));
-        $object_type    = $attrib['_type'] ?: 'event';
+        $object_type    = !empty($attrib['_type']) ? $attrib['_type'] : 'event';
 
         $select_type->add($this->gettext('none'), '');
-        foreach ($alarm_types as $type)
+        foreach ($alarm_types as $type) {
             $select_type->add($this->gettext(strtolower("alarm{$type}option")), $type);
+        }
 
-        foreach (array('-M','-H','-D','+M','+H','+D') as $trigger)
+        foreach (array('-M','-H','-D','+M','+H','+D') as $trigger) {
             $select_offset->add($this->gettext('trigger' . $trigger), $trigger);
+        }
 
         $select_offset->add($this->gettext('trigger0'), '0');
-        if ($absolute_time)
+        if ($absolute_time) {
             $select_offset->add($this->gettext('trigger@'), '@');
+        }
 
         $select_related->add($this->gettext('relatedstart'), 'start');
         $select_related->add($this->gettext('relatedend' . $object_type), 'end');
 
         // pre-set with default values from user settings
         $preset = self::parse_alarm_value($this->rc->config->get('calendar_default_alarm_offset', '-15M'));
         $hidden = array('style' => 'display:none');
 
         return html::span('edit-alarm-set',
             $select_type->show($this->rc->config->get('calendar_default_alarm_type', '')) . ' ' .
             html::span(array('class' => 'edit-alarm-values input-group', 'style' => 'display:none'),
                 $input_value->show($preset[0]) . ' ' .
                 $select_offset->show($preset[1]) . ' ' .
                 $select_related->show() . ' ' .
                 $input_date->show('', $hidden) . ' ' .
                 $input_time->show('', $hidden)
             )
         );
     }
 
     /**
      * Get a list of email addresses of the given user (from login and identities)
      *
      * @param string User Email (default to current user)
      *
      * @return array Email addresses related to the user
      */
     public function get_user_emails($user = null)
     {
         static $_emails = array();
 
         if (empty($user)) {
             $user = $this->rc->user->get_username();
         }
 
         // return cached result
         if (is_array($_emails[$user])) {
             return $_emails[$user];
         }
 
         $emails = array($user);
         $plugin = $this->rc->plugins->exec_hook('calendar_user_emails', array('emails' => $emails));
         $emails = array_map('strtolower', $plugin['emails']);
 
         // add all emails from the current user's identities
         if (!$plugin['abort'] && ($user == $this->rc->user->get_username())) {
             foreach ($this->rc->user->list_emails() as $identity) {
                 $emails[] = strtolower($identity['email']);
             }
         }
 
         $_emails[$user] = array_unique($emails);
         return $_emails[$user];
     }
 
     /**
      * Set the given participant status to the attendee matching the current user's identities
      * Unsets 'rsvp' flag too.
      *
      * @param array  &$event    Event data
      * @param string $status    The PARTSTAT value to set
      * @param bool   $recursive Recurive call
      *
      * @return mixed Email address of the updated attendee or False if none matching found
      */
     public function set_partstat(&$event, $status, $recursive = true)
     {
         $success = false;
         $emails = $this->get_user_emails();
         foreach ((array)$event['attendees'] as $i => $attendee) {
             if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                 $event['attendees'][$i]['status'] = strtoupper($status);
                 unset($event['attendees'][$i]['rsvp']);
                 $success = $attendee['email'];
             }
         }
 
         // apply partstat update to each existing exception
         if ($event['recurrence'] && is_array($event['recurrence']['EXCEPTIONS'])) {
             foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
                 $this->set_partstat($event['recurrence']['EXCEPTIONS'][$i], $status, false);
             }
 
             // set link to top-level exceptions
             $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
         }
 
         return $success;
     }
 
 
     /*********  Alarms handling  *********/
 
     /**
      * Helper function to convert alarm trigger strings
      * into two-field values (e.g. "-45M" => 45, "-M")
      */
     public static function parse_alarm_value($val)
     {
         if ($val[0] == '@') {
             return array(new DateTime($val));
         }
         else if (preg_match('/([+-]?)P?(T?\d+[HMSDW])+/', $val, $m) && preg_match_all('/T?(\d+)([HMSDW])/', $val, $m2, PREG_SET_ORDER)) {
             if ($m[1] == '')
                 $m[1] = '+';
             foreach ($m2 as $seg) {
                 $prefix = $seg[2] == 'D' || $seg[2] == 'W' ? 'P' : 'PT';
                 if ($seg[1] > 0) {  // ignore zero values
                     // convert seconds to minutes
                     if ($seg[2] == 'S') {
                         $seg[2] = 'M';
                         $seg[1] = max(1, round($seg[1]/60));
                     }
 
                     return array($seg[1], $m[1].$seg[2], $m[1].$seg[1].$seg[2], $m[1].$prefix.$seg[1].$seg[2]);
                 }
             }
 
             // return zero value nevertheless
             return array($seg[1], $m[1].$seg[2], $m[1].$seg[1].$seg[2], $m[1].$prefix.$seg[1].$seg[2]);
         }
 
         return false;
     }
 
     /**
      * Convert the alarms list items to be processed on the client
      */
     public static function to_client_alarms($valarms)
     {
         return array_map(function($alarm){
             if ($alarm['trigger'] instanceof DateTime) {
                 $alarm['trigger'] = '@' . $alarm['trigger']->format('U');
             }
             else if ($trigger = libcalendaring::parse_alarm_value($alarm['trigger'])) {
                 $alarm['trigger'] = $trigger[2];
             }
             return $alarm;
         }, (array)$valarms);
     }
 
     /**
      * Process the alarms values submitted by the client
      */
     public static function from_client_alarms($valarms)
     {
         return array_map(function($alarm){
             if ($alarm['trigger'][0] == '@') {
                 try {
                     $alarm['trigger'] = new DateTime($alarm['trigger']);
                     $alarm['trigger']->setTimezone(new DateTimeZone('UTC'));
                 }
                 catch (Exception $e) { /* handle this ? */ }
             }
             else if ($trigger = libcalendaring::parse_alarm_value($alarm['trigger'])) {
                 $alarm['trigger'] = $trigger[3];
             }
             return $alarm;
         }, (array)$valarms);
     }
 
     /**
      * Render localized text for alarm settings
      */
     public static function alarms_text($alarms)
     {
         if (is_array($alarms) && is_array($alarms[0])) {
             $texts = array();
             foreach ($alarms as $alarm) {
                 if ($text = self::alarm_text($alarm))
                     $texts[] = $text;
             }
 
             return join(', ', $texts);
         }
         else {
             return self::alarm_text($alarms);
         }
     }
 
     /**
      * Render localized text for a single alarm property
      */
     public static function alarm_text($alarm)
     {
         if (is_string($alarm)) {
             list($trigger, $action) = explode(':', $alarm);
         }
         else {
             $trigger = $alarm['trigger'];
             $action  = $alarm['action'];
             $related = $alarm['related'];
         }
 
         $text  = '';
         $rcube = rcube::get_instance();
 
         switch ($action) {
         case 'EMAIL':
             $text = $rcube->gettext('libcalendaring.alarmemail');
             break;
         case 'DISPLAY':
             $text = $rcube->gettext('libcalendaring.alarmdisplay');
             break;
         case 'AUDIO':
             $text = $rcube->gettext('libcalendaring.alarmaudio');
             break;
         }
 
         if ($trigger instanceof DateTime) {
             $text .= ' ' . $rcube->gettext(array(
                 'name' => 'libcalendaring.alarmat',
                 'vars' => array('datetime' => $rcube->format_date($trigger))
             ));
         }
         else if (preg_match('/@(\d+)/', $trigger, $m)) {
             $text .= ' ' . $rcube->gettext(array(
                 'name' => 'libcalendaring.alarmat',
                 'vars' => array('datetime' => $rcube->format_date($m[1]))
             ));
         }
         else if ($val = self::parse_alarm_value($trigger)) {
             $r = strtoupper($related ?: 'start') == 'END' ? 'end' : '';
             // TODO: for all-day events say 'on date of event at XX' ?
             if ($val[0] == 0) {
                 $text .= ' ' . $rcube->gettext('libcalendaring.triggerattime' . $r);
             }
             else {
                 $label = 'libcalendaring.trigger' . $r . $val[1];
                 $text .= ' ' . intval($val[0]) . ' ' . $rcube->gettext($label);
             }
         }
         else {
             return false;
         }
 
         return $text;
     }
 
     /**
      * Get the next alarm (time & action) for the given event
      *
      * @param array Record data
      * @return array Hash array with alarm time/type or null if no alarms are configured
      */
     public static function get_next_alarm($rec, $type = 'event')
     {
         if (
             (empty($rec['valarms']) && empty($rec['alarms']))
             || !empty($rec['cancelled'])
             || (!empty($rec['status']) && $rec['status'] == 'CANCELLED')
         ) {
             return null;
         }
 
         if ($type == 'task') {
             $timezone = self::get_instance()->timezone;
             if (!empty($rec['startdate'])) {
                 $time = !empty($rec['starttime']) ? $rec['starttime'] : '12:00';
                 $rec['start'] = new DateTime($rec['startdate'] . ' ' . $time, $timezone);
             }
             if (!empty($rec['date'])) {
                 $time = !empty($rec['time']) ? $rec['time'] : '12:00';
                 $rec[!empty($rec['start']) ? 'end' : 'start'] = new DateTime($rec['date'] . ' ' . $time, $timezone);
             }
         }
 
         if (empty($rec['end'])) {
             $rec['end'] = $rec['start'];
         }
 
         // support legacy format
         if (empty($rec['valarms'])) {
             list($trigger, $action) = explode(':', $rec['alarms'], 2);
             if ($alarm = self::parse_alarm_value($trigger)) {
                 $rec['valarms'] = array(array('action' => $action, 'trigger' => $alarm[3] ?: $alarm[0]));
             }
         }
 
         // alarm ID eq. record ID by default to keep backwards compatibility
         $alarm_id   = isset($rec['id']) ? $rec['id'] : null;
         $alarm_prop = null;
         $expires    = new DateTime('now - 12 hours');
         $notify_at  = null;
 
         // handle multiple alarms
         foreach ($rec['valarms'] as $alarm) {
             $notify_time = null;
 
             if ($alarm['trigger'] instanceof DateTime) {
                 $notify_time = $alarm['trigger'];
             }
             else if (is_string($alarm['trigger'])) {
                 $refdate = !empty($alarm['related']) && $alarm['related'] == 'END' ? $rec['end'] : $rec['start'];
 
                 // abort if no reference date is available to compute notification time
                 if (!is_a($refdate, 'DateTime')) {
                     continue;
                 }
 
                 // TODO: for all-day events, take start @ 00:00 as reference date ?
 
                 try {
                     $interval = new DateInterval(trim($alarm['trigger'], '+-'));
                     $interval->invert = $alarm['trigger'][0] == '-';
                     $notify_time = clone $refdate;
                     $notify_time->add($interval);
                 }
                 catch (Exception $e) {
                     rcube::raise_error($e, true);
                     continue;
                 }
             }
 
             if ($notify_time && (!$notify_at || ($notify_time > $notify_at && $notify_time > $expires))) {
                 $notify_at  = $notify_time;
                 $action     = isset($alarm['action']) ? $alarm['action'] : null;
                 $alarm_prop = $alarm;
 
                 // generate a unique alarm ID if multiple alarms are set
                 if (count($rec['valarms']) > 1) {
                     $rec_id = substr(md5(isset($rec['id']) ? $rec['id'] : 'none'), 0, 16);
                     $alarm_id = $rec_id . '-' . $notify_at->format('Ymd\THis');
                 }
             }
         }
 
         return !$notify_at ? null : array(
             'time'   => $notify_at->format('U'),
             'action' => !empty($action) ? strtoupper($action) : 'DISPLAY',
             'id'     => $alarm_id,
             'prop'   => $alarm_prop,
         );
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for pending notifications and pass them to the client
      */
     public function refresh($attr)
     {
         // collect pending alarms from all providers (e.g. calendar, tasks)
         $plugin = $this->rc->plugins->exec_hook('pending_alarms', array(
             'time' => time(),
             'alarms' => array(),
         ));
 
         if (!$plugin['abort'] && !empty($plugin['alarms'])) {
             // make sure texts and env vars are available on client
             $this->add_texts('localization/', true);
             $this->rc->output->add_label('close');
             $this->rc->output->set_env('snooze_select', $this->snooze_select());
             $this->rc->output->command('plugin.display_alarms', $this->_alarms_output($plugin['alarms']));
         }
     }
 
     /**
      * Handler for alarm dismiss/snooze requests
      */
     public function alarms_action()
     {
 //        $action = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $data  = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         $data['ids'] = explode(',', $data['id']);
         $plugin = $this->rc->plugins->exec_hook('dismiss_alarms', $data);
 
         if (!empty($plugin['success'])) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $this->rc->output->show_message('calendar.errorsaving', 'error');
         }
     }
 
     /**
      * Generate reduced and streamlined output for pending alarms
      */
     private function _alarms_output($alarms)
     {
         $out = array();
         foreach ($alarms as $alarm) {
             $out[] = array(
                 'id'       => $alarm['id'],
                 'start'    => !empty($alarm['start']) ? $this->adjust_timezone($alarm['start'])->format('c') : '',
                 'end'      => !empty($alarm['end'])? $this->adjust_timezone($alarm['end'])->format('c') : '',
                 'allDay'   => !empty($alarm['allday']),
                 'action'   => $alarm['action'],
                 'title'    => $alarm['title'],
                 'location' => $alarm['location'],
                 'calendar' => $alarm['calendar'],
             );
         }
 
         return $out;
     }
 
     /**
      * Render a dropdown menu to choose snooze time
      */
     private function snooze_select($attrib = array())
     {
         $steps = array(
              5 => 'repeatinmin',
             10 => 'repeatinmin',
             15 => 'repeatinmin',
             20 => 'repeatinmin',
             30 => 'repeatinmin',
             60 => 'repeatinhr',
             120 => 'repeatinhrs',
             1440 => 'repeattomorrow',
             10080 => 'repeatinweek',
         );
 
         $items = array();
         foreach ($steps as $n => $label) {
             $items[] = html::tag('li', null, html::a(array('href' => "#" . ($n * 60), 'class' => 'active'),
                 $this->gettext(array('name' => $label, 'vars' => array('min' => $n % 60, 'hrs' => intval($n / 60))))));
         }
 
         return html::tag('ul', $attrib + array('class' => 'toolbarmenu menu'), join("\n", $items), html::$common_attrib);
     }
 
 
     /*********  Recurrence rules handling ********/
 
     /**
      * Render localized text describing the recurrence rule of an event
      */
     public function recurrence_text($rrule)
     {
         $limit     = 10;
         $exdates   = array();
         $format    = $this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format']);
         $format    = self::to_php_date_format($format);
         $format_fn = function($dt) use ($format) {
             return rcmail::get_instance()->format_date($dt, $format);
         };
 
         if (is_array($rrule['EXDATE']) && !empty($rrule['EXDATE'])) {
             $exdates = array_map($format_fn, $rrule['EXDATE']);
         }
 
         if (empty($rrule['FREQ']) && !empty($rrule['RDATE'])) {
             $rdates = array_map($format_fn, $rrule['RDATE']);
 
             if (!empty($exdates)) {
                 $rdates = array_diff($rdates, $exdates);
             }
 
             if (count($rdates) > $limit) {
                 $rdates = array_slice($rdates, 0, $limit);
                 $more   = true;
             }
 
             return $this->gettext('ondate') . ' ' . join(', ', $rdates)
                 . ($more ? '...' : '');
         }
 
         $output  = sprintf('%s %d ', $this->gettext('every'), $rrule['INTERVAL'] ?: 1);
 
         switch ($rrule['FREQ']) {
         case 'DAILY':
             $output .= $this->gettext('days');
             break;
         case 'WEEKLY':
             $output .= $this->gettext('weeks');
             break;
         case 'MONTHLY':
             $output .= $this->gettext('months');
             break;
         case 'YEARLY':
             $output .= $this->gettext('years');
             break;
         }
 
         if ($rrule['COUNT']) {
             $until = $this->gettext(array('name' => 'forntimes', 'vars' => array('nr' => $rrule['COUNT'])));
         }
         else if ($rrule['UNTIL']) {
             $until = $this->gettext('recurrencend') . ' ' . $this->rc->format_date($rrule['UNTIL'], $format);
         }
         else {
             $until = $this->gettext('forever');
         }
 
         $output .= ', ' . $until;
 
         if (!empty($exdates)) {
             if (count($exdates) > $limit) {
                 $exdates = array_slice($exdates, 0, $limit);
                 $more    = true;
             }
 
             $output  .= '; ' . $this->gettext('except') . ' ' . join(', ', $exdates)
                 . ($more ? '...' : '');
         }
 
         return $output;
     }
 
     /**
      * Generate the form for recurrence settings
      */
     public function recurrence_form($attrib = array())
     {
         switch ($attrib['part']) {
             // frequency selector
             case 'frequency':
                 $select = new html_select(array('name' => 'frequency', 'id' => 'edit-recurrence-frequency', 'class' => 'form-control'));
                 $select->add($this->gettext('never'),   '');
                 $select->add($this->gettext('daily'),   'DAILY');
                 $select->add($this->gettext('weekly'),  'WEEKLY');
                 $select->add($this->gettext('monthly'), 'MONTHLY');
                 $select->add($this->gettext('yearly'),  'YEARLY');
                 $select->add($this->gettext('rdate'),   'RDATE');
                 $html = html::label(array('for' => 'edit-recurrence-frequency', 'class' => 'col-form-label col-sm-2'), $this->gettext('frequency'))
                     . html::div('col-sm-10', $select->show(''));
                 break;
 
             // daily recurrence
             case 'daily':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-daily'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-daily', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('days')))));
                 break;
 
             // weekly recurrence form
             case 'weekly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-weekly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-weekly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('weeks')))));
 
                 // weekday selection
                 $daymap   = array('sun','mon','tue','wed','thu','fri','sat');
                 $checkbox = new html_checkbox(array('name' => 'byday', 'class' => 'edit-recurrence-weekly-byday'));
                 $first    = $this->rc->config->get('calendar_first_day', 1);
 
                 for ($weekdays = '', $j = $first; $j <= $first+6; $j++) {
                     $d = $j % 7;
                     $weekdays .= html::label(array('class' => 'weekday'),
                         $checkbox->show('', array('value' => strtoupper(substr($daymap[$d], 0, 2)))) .
                         $this->gettext($daymap[$d])
                     ) . ' ';
                 }
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bydays'))
                     . html::div('col-sm-10 form-control-plaintext', $weekdays));
                 break;
 
             // monthly recurrence form
             case 'monthly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-monthly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-monthly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('months')))));
 
                 $checkbox = new html_checkbox(array('name' => 'bymonthday', 'class' => 'edit-recurrence-monthly-bymonthday'));
                 for ($monthdays = '', $d = 1; $d <= 31; $d++) {
                     $monthdays .= html::label(array('class' => 'monthday'), $checkbox->show('', array('value' => $d)) . $d);
                     $monthdays .= $d % 7 ? ' ' : html::br();
                 }
 
                 // rule selectors
                 $radio = new html_radiobutton(array('name' => 'repeatmode', 'class' => 'edit-recurrence-monthly-mode'));
                 $table = new html_table(array('cols' => 2, 'border' => 0, 'cellpadding' => 0, 'class' => 'formtable'));
                 $table->add('label', html::label(null, $radio->show('BYMONTHDAY', array('value' => 'BYMONTHDAY')) . ' ' . $this->gettext('each')));
                 $table->add(null, $monthdays);
                 $table->add('label', html::label(null, $radio->show('', array('value' => 'BYDAY')) . ' ' . $this->gettext('every')));
                 $table->add('recurrence-onevery', $this->rrule_selectors($attrib['part']));
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bydays'))
                     . html::div('col-sm-10 form-control-plaintext', $table->show()));
                 break;
 
             // annually recurrence form
             case 'yearly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-yearly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-yearly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('years')))));
 
                 // month selector
                 $monthmap = array('','jan','feb','mar','apr','may','jun','jul','aug','sep','oct','nov','dec');
                 $checkbox = new html_checkbox(array('name' => 'bymonth', 'class' => 'edit-recurrence-yearly-bymonth'));
 
                 for ($months = '', $m = 1; $m <= 12; $m++) {
                     $months .= html::label(array('class' => 'month'), $checkbox->show(null, array('value' => $m)) . $this->gettext($monthmap[$m]));
                     $months .= $m % 4 ? ' ' : html::br();
                 }
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bymonths'))
                     . html::div('col-sm-10 form-control-plaintext',
                         html::div(array('id' => 'edit-recurrence-yearly-bymonthblock'), $months)
                         . html::div('recurrence-onevery', $this->rrule_selectors($attrib['part'], '---'))
                     ));
                 break;
 
             // end of recurrence form
             case 'until':
                 $radio  = new html_radiobutton(array('name' => 'repeat', 'class' => 'edit-recurrence-until'));
                 $select = $this->interval_selector(array('name' => 'times', 'id' => 'edit-recurrence-repeat-times', 'class' => 'form-control'));
                 $input  = new html_inputfield(array('name' => 'untildate', 'id' => 'edit-recurrence-enddate', 'size' => '10', 'class' => 'form-control datepicker'));
 
                 $html = html::div('line first',
                     $radio->show('', array('value' => '', 'id' => 'edit-recurrence-repeat-forever'))
                         . ' ' . html::label('edit-recurrence-repeat-forever', $this->gettext('forever'))
                 );
 
                 $label = $this->gettext('ntimes');
                 if (strpos($label, '$') === 0) {
                     $label = str_replace('$n', '', $label);
                     $group  = $select->show(1)
                         . html::span('input-group-append', html::span('input-group-text', rcube::Q($label)));
                 }
                 else {
                     $label = str_replace('$n', '', $label);
                     $group  = html::span('input-group-prepend', html::span('input-group-text', rcube::Q($label)))
                         . $select->show(1);
                 }
 
                 $html .= html::div('line',
                     $radio->show('', array('value' => 'count', 'id' => 'edit-recurrence-repeat-count'))
                         . ' ' . html::label('edit-recurrence-repeat-count', $this->gettext('for'))
                         . ' ' . html::span('input-group', $group)
                 );
 
                 $html .= html::div('line',
                     $radio->show('', array('value' => 'until', 'id' => 'edit-recurrence-repeat-until', 'aria-label' => $this->gettext('untilenddate')))
                         . ' ' . html::label('edit-recurrence-repeat-until', $this->gettext('untildate'))
                         . ' ' . $input->show('', array('aria-label' => $this->gettext('untilenddate')))
                 );
 
                 $html = html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), ucfirst($this->gettext('recurrencend')))
                     . html::div('col-sm-10', $html));
                 break;
 
             case 'rdate':
                 $ul     = html::tag('ul', array('id' => 'edit-recurrence-rdates', 'class' => 'recurrence-rdates'), '');
                 $input  = new html_inputfield(array('name' => 'rdate', 'id' => 'edit-recurrence-rdate-input', 'size' => "10", 'class' => 'form-control datepicker'));
                 $button = new html_inputfield(array('type' => 'button', 'class' => 'button add', 'value' => $this->gettext('addrdate')));
 
                 $html = html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2', 'for' => 'edit-recurrence-rdate-input'), $this->gettext('bydates'))
                     . html::div('col-sm-10', $ul . html::div('inputform', $input->show() . $button->show())));
                 break;
         }
 
         return $html;
     }
 
     /**
      * Input field for interval selection
      */
     private function interval_selector($attrib)
     {
         $select = new html_select($attrib);
         $select->add(range(1,30), range(1,30));
         return $select;
     }
 
     /**
      * Drop-down menus for recurrence rules like "each last sunday of"
      */
     private function rrule_selectors($part, $noselect = null)
     {
         // rule selectors
         $select_prefix = new html_select(array('name' => 'bydayprefix', 'id' => "edit-recurrence-$part-prefix", 'class' => 'form-control'));
         if ($noselect) $select_prefix->add($noselect, '');
         $select_prefix->add(array(
                 $this->gettext('first'),
                 $this->gettext('second'),
                 $this->gettext('third'),
                 $this->gettext('fourth'),
                 $this->gettext('last')
             ),
             array(1, 2, 3, 4, -1));
 
         $select_wday = new html_select(array('name' => 'byday', 'id' => "edit-recurrence-$part-byday", 'class' => 'form-control'));
         if ($noselect) $select_wday->add($noselect, '');
 
         $daymap = array('sunday','monday','tuesday','wednesday','thursday','friday','saturday');
         $first = $this->rc->config->get('calendar_first_day', 1);
         for ($j = $first; $j <= $first+6; $j++) {
             $d = $j % 7;
             $select_wday->add($this->gettext($daymap[$d]), strtoupper(substr($daymap[$d], 0, 2)));
         }
 
         return $select_prefix->show() . '&nbsp;' . $select_wday->show();
     }
 
     /**
      * Convert the recurrence settings to be processed on the client
      */
     public function to_client_recurrence($recurrence, $allday = false)
     {
         if ($recurrence['UNTIL']) {
             $recurrence['UNTIL'] = $this->adjust_timezone($recurrence['UNTIL'], $allday)->format('c');
         }
 
         // format RDATE values
         if (is_array($recurrence['RDATE'])) {
             $libcal = $this;
             $recurrence['RDATE'] = array_map(function($rdate) use ($libcal) {
                 return $libcal->adjust_timezone($rdate, true)->format('c');
             }, $recurrence['RDATE']);
         }
 
         unset($recurrence['EXCEPTIONS']);
 
         return $recurrence;
     }
 
     /**
      * Process the alarms values submitted by the client
      */
     public function from_client_recurrence($recurrence, $start = null)
     {
         if (is_array($recurrence) && !empty($recurrence['UNTIL'])) {
             $recurrence['UNTIL'] = new DateTime($recurrence['UNTIL'], $this->timezone);
         }
 
         if (is_array($recurrence) && is_array($recurrence['RDATE'])) {
             $tz = $this->timezone;
             $recurrence['RDATE'] = array_map(function($rdate) use ($tz, $start) {
                 try {
                     $dt = new DateTime($rdate, $tz);
                     if (is_a($start, 'DateTime'))
                         $dt->setTime($start->format('G'), $start->format('i'));
                     return $dt;
                 }
                 catch (Exception $e) {
                     return null;
                 }
             }, $recurrence['RDATE']);
         }
 
         return $recurrence;
     }
 
 
     /*********  iTip message detection  *********/
 
     /**
      * Check mail message structure of there are .ics files attached
      */
     public function mail_message_load($p)
     {
         $this->ical_message = $p['object'];
         $itip_part          = null;
 
         // check all message parts for .ics files
         foreach ((array)$this->ical_message->mime_parts as $part) {
             if (self::part_is_vcalendar($part, $this->ical_message)) {
                 if ($part->ctype_parameters['method'])
                     $itip_part = $part->mime_id;
                 else
                     $this->ical_parts[] = $part->mime_id;
             }
         }
 
         // priorize part with method parameter
         if ($itip_part) {
             $this->ical_parts = array($itip_part);
         }
     }
 
     /**
      * Getter for the parsed iCal objects attached to the current email message
      *
      * @return object libvcalendar parser instance with the parsed objects
      */
     public function get_mail_ical_objects()
     {
         // create parser and load ical objects
         if (!$this->mail_ical_parser) {
             $this->mail_ical_parser = $this->get_ical();
 
             foreach ($this->ical_parts as $mime_id) {
                 $part    = $this->ical_message->mime_parts[$mime_id];
                 $charset = $part->ctype_parameters['charset'] ?: RCUBE_CHARSET;
                 $this->mail_ical_parser->import($this->ical_message->get_part_body($mime_id, true), $charset);
 
                 // check if the parsed object is an instance of a recurring event/task
                 array_walk($this->mail_ical_parser->objects, 'libcalendaring::identify_recurrence_instance');
 
                 // stop on the part that has an iTip method specified
                 if (count($this->mail_ical_parser->objects) && $this->mail_ical_parser->method) {
                     $this->mail_ical_parser->message_date = $this->ical_message->headers->date;
                     $this->mail_ical_parser->mime_id = $mime_id;
 
                     // store the message's sender address for comparisons
                     $from = rcube_mime::decode_address_list($this->ical_message->headers->from, 1, true, null, true);
                     $this->mail_ical_parser->sender = !empty($from) ? $from[1] : '';
 
                     if (!empty($this->mail_ical_parser->sender)) {
                         foreach ($this->mail_ical_parser->objects as $i => $object) {
                             $this->mail_ical_parser->objects[$i]['_sender'] = $this->mail_ical_parser->sender;
                             $this->mail_ical_parser->objects[$i]['_sender_utf'] = rcube_utils::idn_to_utf8($this->mail_ical_parser->sender);
                         }
                     }
 
                     break;
                 }
             }
         }
 
         return $this->mail_ical_parser;
     }
 
     /**
      * Read the given mime message from IMAP and parse ical data
      *
      * @param string Mailbox name
      * @param string Message UID
      * @param string Message part ID and object index (e.g. '1.2:0')
      * @param string Object type filter (optional)
      *
      * @return array Hash array with the parsed iCal 
      */
     public function mail_get_itip_object($mbox, $uid, $mime_id, $type = null)
     {
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             list($mime_id, $index) = explode(':', $mime_id);
 
             $part    = $imap->get_message_part($uid, $mime_id);
             $headers = $imap->get_message_headers($uid);
             $parser  = $this->get_ical();
 
             if ($part->ctype_parameters['charset']) {
                 $charset = $part->ctype_parameters['charset'];
             }
 
             if ($part) {
                 $objects = $parser->import($part, $charset);
             }
         }
 
         // successfully parsed events/tasks?
         if (!empty($objects) && ($object = $objects[$index]) && (!$type || $object['_type'] == $type)) {
             if ($parser->method)
                 $object['_method'] = $parser->method;
 
             // store the message's sender address for comparisons
             $from = rcube_mime::decode_address_list($headers->from, 1, true, null, true);
             $object['_sender'] = !empty($from) ? $from[1] : '';
             $object['_sender_utf'] = rcube_utils::idn_to_utf8($object['_sender']);
 
             // check if this is an instance of a recurring event/task
             self::identify_recurrence_instance($object);
 
             return $object;
         }
 
         return null;
     }
 
     /**
      * Checks if specified message part is a vcalendar data
      *
      * @param rcube_message_part Part object
      * @param rcube_message      Message object
      *
      * @return boolean True if part is of type vcard
      */
     public static function part_is_vcalendar($part, $message = null)
     {
         // First check if the message is "valid" (i.e. not multipart/report)
         if ($message) {
             $level = explode('.', $part->mime_id);
 
             while (array_pop($level) !== null) {
                 $parent = $message->mime_parts[join('.', $level) ?: 0];
                 if ($parent->mimetype == 'multipart/report') {
                     return false;
                 }
             }
         }
 
         return (
             in_array($part->mimetype, array('text/calendar', 'text/x-vcalendar', 'application/ics')) ||
             // Apple sends files as application/x-any (!?)
             ($part->mimetype == 'application/x-any' && $part->filename && preg_match('/\.ics$/i', $part->filename))
         );
     }
 
     /**
      * Single occourrences of recurring events are identified by their RECURRENCE-ID property
      * in iCal which is represented as 'recurrence_date' in our internal data structure.
      *
      * Check if such a property exists and derive the '_instance' identifier and '_savemode'
      * attributes which are used in the storage backend to identify the nested exception item.
      */
     public static function identify_recurrence_instance(&$object)
     {
         // for savemode=all, remove recurrence instance identifiers
         if (!empty($object['_savemode']) && $object['_savemode'] == 'all' && $object['recurrence']) {
             unset($object['_instance'], $object['recurrence_date']);
         }
         // set instance and 'savemode' according to recurrence-id
         else if (!empty($object['recurrence_date']) && is_a($object['recurrence_date'], 'DateTime')) {
             $object['_instance'] = self::recurrence_instance_identifier($object);
             $object['_savemode'] = $object['thisandfuture'] ? 'future' : 'current';
         }
         else if (!empty($object['recurrence_id']) && !empty($object['_instance'])) {
             if (strlen($object['_instance']) > 4) {
                 $object['recurrence_date'] = rcube_utils::anytodatetime($object['_instance'], $object['start']->getTimezone());
             }
             else {
                 $object['recurrence_date'] = clone $object['start'];
             }
         }
     }
 
     /**
      * Return a date() format string to render identifiers for recurrence instances
      *
      * @param array Hash array with event properties
      * @return string Format string
      */
     public static function recurrence_id_format($event)
     {
         return $event['allday'] ? 'Ymd' : 'Ymd\THis';
     }
 
     /**
      * Return the identifer for the given instance of a recurring event
      *
      * @param array Hash array with event properties
      * @param bool  All-day flag from the main event
      *
      * @return mixed Format string or null if identifier cannot be generated
      */
     public static function recurrence_instance_identifier($event, $allday = null)
     {
         $instance_date = $event['recurrence_date'] ?: $event['start'];
 
         if ($instance_date && is_a($instance_date, 'DateTime')) {
             // According to RFC5545 (3.8.4.4) RECURRENCE-ID format should
             // be date/date-time depending on the main event type, not the exception
             if ($allday === null) {
                 $allday = $event['allday'];
             }
 
             return $instance_date->format($allday ? 'Ymd' : 'Ymd\THis');
         }
     }
 
 
     /*********  Attendee handling functions  *********/
 
     /**
      * Handler for attendee group expansion requests
      */
     public function expand_attendee_group()
     {
         $id     = rcube_utils::get_input_value('id', rcube_utils::INPUT_POST);
         $data   = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
         $result = array('id' => $id, 'members' => array());
         $maxnum = 500;
 
         // iterate over all autocomplete address books (we don't know the source of the group)
         foreach ((array)$this->rc->config->get('autocomplete_addressbooks', 'sql') as $abook_id) {
             if (($abook = $this->rc->get_address_book($abook_id)) && $abook->groups) {
                 foreach ($abook->list_groups($data['name'], 1) as $group) {
                     // this is the matching group to expand
                     if (in_array($data['email'], (array)$group['email'])) {
                         $abook->set_pagesize($maxnum);
                         $abook->set_group($group['ID']);
 
                         // get all members
                         $res = $abook->list_records($this->rc->config->get('contactlist_fields'));
 
                         // handle errors (e.g. sizelimit, timelimit)
                         if ($abook->get_error()) {
                             $result['error'] = $this->rc->gettext('expandattendeegrouperror', 'libcalendaring');
                             $res = false;
                         }
                         // check for maximum number of members (we don't wanna bloat the UI too much)
                         else if ($res->count > $maxnum) {
                             $result['error'] = $this->rc->gettext('expandattendeegroupsizelimit', 'libcalendaring');
                             $res = false;
                         }
 
                         while ($res && ($member = $res->iterate())) {
                             $emails = (array)$abook->get_col_values('email', $member, true);
                             if (!empty($emails) && ($email = array_shift($emails))) {
                                 $result['members'][] = array(
                                     'email' => $email,
                                     'name' => rcube_addressbook::compose_list_name($member),
                                 );
                             }
                         }
 
                         break 2;
                     }
                 }
             }
         }
 
         $this->rc->output->command('plugin.expand_attendee_callback', $result);
     }
 
     /**
      * Merge attendees of the old and new event version
      * with keeping current user and his delegatees status
      *
      * @param array &$new   New object data
      * @param array $old    Old object data
      * @param bool  $status New status of the current user
      */
     public function merge_attendees(&$new, $old, $status = null)
     {
         if (empty($status)) {
             $emails    = $this->get_user_emails();
             $delegates = array();
             $attendees = array();
 
             // keep attendee status of the current user
             foreach ((array) $new['attendees'] as $i => $attendee) {
                 if (empty($attendee['email'])) {
                     continue;
                 }
 
                 $attendees[] = $email = strtolower($attendee['email']);
 
                 if (in_array($email, $emails)) {
                     foreach ($old['attendees'] as $_attendee) {
                         if ($attendee['email'] == $_attendee['email']) {
                             $new['attendees'][$i] = $_attendee;
                             if ($_attendee['status'] == 'DELEGATED' && ($email = $_attendee['delegated-to'])) {
                                 $delegates[] = strtolower($email);
                             }
 
                             break;
                         }
                     }
                 }
             }
 
             // make sure delegated attendee is not lost
             foreach ($delegates as $delegatee) {
                 if (!in_array($delegatee, $attendees)) {
                     foreach ((array) $old['attendees'] as $attendee) {
                         if ($attendee['email'] && ($email = strtolower($attendee['email'])) && $email == $delegatee) {
                             $new['attendees'][] = $attendee;
                             break;
                         }
                     }
                 }
             }
         }
 
         // We also make sure that status of any attendee
         // is not overriden by NEEDS-ACTION if it was already set
         // which could happen if you work with shared events
         foreach ((array) $new['attendees'] as $i => $attendee) {
             if ($attendee['email'] && $attendee['status'] == 'NEEDS-ACTION') {
                 foreach ($old['attendees'] as $_attendee) {
                     if ($attendee['email'] == $_attendee['email']) {
                         $new['attendees'][$i]['status'] = $_attendee['status'];
                         unset($new['attendees'][$i]['rsvp']);
                         break;
                     }
                 }
             }
         }
     }
 
 
     /*********  Static utility functions  *********/
 
     /**
      * Convert the internal structured data into a vcalendar rrule 2.0 string
      */
     public static function to_rrule($recurrence, $allday = false)
     {
         if (is_string($recurrence)) {
             return $recurrence;
         }
 
         $rrule = '';
         foreach ((array)$recurrence as $k => $val) {
             $k = strtoupper($k);
             switch ($k) {
             case 'UNTIL':
                 // convert to UTC according to RFC 5545
                 if (is_a($val, 'DateTime')) {
                     if (!$allday && empty($val->_dateonly)) {
                         $until = clone $val;
                         $until->setTimezone(new DateTimeZone('UTC'));
                         $val = $until->format('Ymd\THis\Z');
                     }
                     else {
                         $val = $val->format('Ymd');
                     }
                 }
                 break;
             case 'RDATE':
             case 'EXDATE':
                 foreach ((array)$val as $i => $ex) {
                     if (is_a($ex, 'DateTime')) {
                         $val[$i] = $ex->format('Ymd\THis');
                     }
                 }
                 $val = join(',', (array)$val);
                 break;
             case 'EXCEPTIONS':
                 continue 2;
             }
 
             if (strlen($val)) {
                 $rrule .= $k . '=' . $val . ';';
             }
         }
 
         return rtrim($rrule, ';');
     }
 
     /**
      * Convert from fullcalendar date format to PHP date() format string
      */
     public static function to_php_date_format($from)
     {
         // "dd.MM.yyyy HH:mm:ss" => "d.m.Y H:i:s"
         return strtr(strtr($from, array(
             'YYYY' => 'Y',
             'YY'   => 'y',
             'yyyy' => 'Y',
             'yy'   => 'y',
             'MMMM' => 'F',
             'MMM'  => 'M',
             'MM'   => 'm',
             'M'    => 'n',
             'dddd' => 'l',
             'ddd'  => 'D',
             'DD'   => 'd',
             'D'    => 'j',
             'HH'   => '**',
             'hh'   => '%%',
             'H'    => 'G',
             'h'    => 'g',
             'mm'   => 'i',
             'ss'   => 's',
             'TT'   => 'A',
             'tt'   => 'a',
             'T'    => 'A',
             't'    => 'a',
             'u'    => 'c',
         )), array(
             '**'   => 'H',
             '%%'   => 'h',
         ));
     }
 
     /**
      * Convert from PHP date() format to fullcalendar (MomentJS) format string
      */
     public static function from_php_date_format($from)
     {
         // "d.m.Y H:i:s" => "dd.MM.yyyy HH:mm:ss"
         return strtr($from, array(
             'y' => 'YY',
             'Y' => 'YYYY',
             'M' => 'MMM',
             'F' => 'MMMM',
             'm' => 'MM',
             'n' => 'M',
             'j' => 'D',
             'd' => 'DD',
             'D' => 'ddd',
             'l' => 'dddd',
             'H' => 'HH',
             'h' => 'hh',
             'G' => 'H',
             'g' => 'h',
             'i' => 'mm',
             's' => 'ss',
             'c' => '',
         ));
     }
-
 }
diff --git a/plugins/libkolab/lib/kolab_attachments_handler.php b/plugins/libkolab/lib/kolab_attachments_handler.php
index d38739e6..7ddcea05 100644
--- a/plugins/libkolab/lib/kolab_attachments_handler.php
+++ b/plugins/libkolab/lib/kolab_attachments_handler.php
@@ -1,370 +1,370 @@
 <?php
 
 /**
  * Shared code for attachments handling in Kolab plugins
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  * @author Aleksander Machniak <machniak@kolabsys.com>
  *
  * Copyright (C) 2012-2018, 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_attachments_handler
 {
     private $rc;
     private $attachment;
 
     public function __construct()
     {
         $this->rc = rcmail::get_instance();
     }
 
     public static function ui()
     {
         $rcmail = rcmail::get_instance();
         $self   = new self;
 
         $rcmail->output->add_handler('plugin.attachments_form', array($self, 'files_form'));
         $rcmail->output->add_handler('plugin.attachments_list', array($self, 'files_list'));
         $rcmail->output->add_handler('plugin.filedroparea', array($self, 'files_drop_area'));
     }
 
     /**
      * Generate HTML element for attachments list
      */
     public function files_list($attrib = array())
     {
         if (!$attrib['id']) {
             $attrib['id'] = 'kolabattachmentlist';
         }
 
         // define list of file types which can be displayed inline
         // same as in program/steps/mail/show.inc
         $this->rc->output->set_env('mimetypes', (array)$this->rc->config->get('client_mimetypes'));
 
         $this->rc->output->add_gui_object('attachmentlist', $attrib['id']);
 
         return html::tag('ul', $attrib, '', html::$common_attrib);
     }
 
     /**
      * Generate the form for event attachments upload
      */
     public function files_form($attrib = array())
     {
         // add ID if not given
-        if (!$attrib['id']) {
+        if (empty($attrib['id'])) {
             $attrib['id'] = 'kolabuploadform';
         }
 
         return $this->rc->upload_form($attrib, 'uploadform', 'upload-file', array('multiple' => true));
     }
 
     /**
      * Register UI object for HTML5 drag & drop file upload
      */
     public function files_drop_area($attrib = array())
     {
         // add ID if not given
         if (!$attrib['id']) {
             $attrib['id'] = 'kolabfiledroparea';
         }
 
         $this->rc->output->add_gui_object('filedrop', $attrib['id']);
         $this->rc->output->set_env('filedrop', array('action' => 'upload', 'fieldname' => '_attachments'));
     }
 
     /**
      * Displays attachment preview page
      */
     public function attachment_page($attachment)
     {
         $this->attachment = $attachment;
 
         $this->rc->plugins->include_script('libkolab/libkolab.js');
 
         $this->rc->output->add_handler('plugin.attachmentframe', array($this, 'attachment_frame'));
         $this->rc->output->add_handler('plugin.attachmentcontrols', array($this, 'attachment_header'));
         $this->rc->output->set_env('filename', $attachment['name']);
         $this->rc->output->set_env('mimetype', $attachment['mimetype']);
         $this->rc->output->send('libkolab.attachment');
     }
 
     /**
      * Handler for attachment uploads
      */
     public function attachment_upload($session_key, $id_prefix = '')
     {
         // Upload progress update
         if (!empty($_GET['_progress'])) {
             $this->rc->upload_progress();
         }
 
         $recid    = $id_prefix . rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
         $uploadid = rcube_utils::get_input_value('_uploadid', rcube_utils::INPUT_GPC);
 
         if (!is_array($_SESSION[$session_key]) || $_SESSION[$session_key]['id'] != $recid) {
             $_SESSION[$session_key] = array();
             $_SESSION[$session_key]['id'] = $recid;
             $_SESSION[$session_key]['attachments'] = array();
         }
 
         // clear all stored output properties (like scripts and env vars)
         $this->rc->output->reset();
 
         if (is_array($_FILES['_attachments']['tmp_name'])) {
             foreach ($_FILES['_attachments']['tmp_name'] as $i => $filepath) {
                 // Process uploaded attachment if there is no error
                 $err = $_FILES['_attachments']['error'][$i];
 
                 if (!$err) {
                     $filename   = $_FILES['_attachments']['name'][$i];
                     $attachment = array(
                         'path'     => $filepath,
                         'size'     => $_FILES['_attachments']['size'][$i],
                         'name'     => $filename,
                         'mimetype' => rcube_mime::file_content_type($filepath, $filename, $_FILES['_attachments']['type'][$i]),
                         'group'    => $recid,
                     );
 
                     $attachment = $this->rc->plugins->exec_hook('attachment_upload', $attachment);
                 }
 
                 if (!$err && $attachment['status'] && !$attachment['abort']) {
                     $id = $attachment['id'];
 
                     // store new attachment in session
                     unset($attachment['status'], $attachment['abort']);
                     $this->rc->session->append($session_key . '.attachments', $id, $attachment);
 
                     if (($icon = $_SESSION[$session_key . '_deleteicon']) && is_file($icon)) {
                         $button = html::img(array(
                             'src' => $icon,
                             'alt' => $this->rc->gettext('delete')
                         ));
                     }
                     else if ($_SESSION[$session_key . '_textbuttons']) {
                         $button = rcube::Q($this->rc->gettext('delete'));
                     }
                     else {
                         $button = '';
                     }
 
                     $link_content = sprintf('<span class="attachment-name">%s</span><span class="attachment-size">(%s)</span>',
                         rcube::Q($attachment['name']), $this->rc->show_bytes($attachment['size']));
 
                     $delete_link = html::a(array(
                             'href'       => "#delete",
                             'class'      => 'delete',
                             'onclick'    => sprintf("return %s.remove_from_attachment_list('rcmfile%s')", rcmail_output::JS_OBJECT_NAME, $id),
                             'title'      => $this->rc->gettext('delete'),
                             'aria-label' => $this->rc->gettext('delete') . ' ' . $attachment['name'],
                         ), $button);
 
                     $content_link = html::a(array(
                             'href'    => "#load",
                             'class'   => 'filename',
                             'onclick' => 'return false', // sprintf("return %s.command('load-attachment','rcmfile%s', this, event)", rcmail_output::JS_OBJECT_NAME, $id),
                          ), $link_content);
 
                     $content .= $_SESSION[$session_key . '_icon_pos'] == 'left' ? $delete_link.$content_link : $content_link.$delete_link;
 
                     $this->rc->output->command('add2attachment_list', "rcmfile$id", array(
                             'html'      => $content,
                             'name'      => $attachment['name'],
                             'mimetype'  => $attachment['mimetype'],
                             'classname' => 'no-menu ' . rcube_utils::file2class($attachment['mimetype'], $attachment['name']),
                             'complete'  => true
                         ), $uploadid);
                 }
                 else {  // upload failed
                     if ($err == UPLOAD_ERR_INI_SIZE || $err == UPLOAD_ERR_FORM_SIZE) {
                         $msg = $this->rc->gettext(array('name' => 'filesizeerror', 'vars' => array(
                             'size' => $this->rc->show_bytes(parse_bytes(ini_get('upload_max_filesize'))))));
                     }
                     else if ($attachment['error']) {
                         $msg = $attachment['error'];
                     }
                     else {
                         $msg = $this->rc->gettext('fileuploaderror');
                     }
 
                     $this->rc->output->command('display_message', $msg, 'error');
                     $this->rc->output->command('remove_from_attachment_list', $uploadid);
                 }
             }
         }
         else if ($_SERVER['REQUEST_METHOD'] == 'POST') {
             // if filesize exceeds post_max_size then $_FILES array is empty,
             // show filesizeerror instead of fileuploaderror
             if ($maxsize = ini_get('post_max_size'))
                 $msg = $this->rc->gettext(array('name' => 'filesizeerror', 'vars' => array(
                     'size' => $this->rc->show_bytes(parse_bytes($maxsize)))));
             else
                 $msg = $this->rc->gettext('fileuploaderror');
 
             $this->rc->output->command('display_message', $msg, 'error');
             $this->rc->output->command('remove_from_attachment_list', $uploadid);
         }
 
         $this->rc->output->send('iframe');
     }
 
 
     /**
      * Deliver an event/task attachment to the client
      * (similar as in Roundcube core program/steps/mail/get.inc)
      */
     public function attachment_get($attachment)
     {
         ob_end_clean();
 
         if ($attachment && $attachment['body']) {
             // allow post-processing of the attachment body
             $part = new rcube_message_part;
             $part->filename  = $attachment['name'];
             $part->size      = $attachment['size'];
             $part->mimetype  = $attachment['mimetype'];
 
             $plugin = $this->rc->plugins->exec_hook('message_part_get', array(
                 'body'     => $attachment['body'],
                 'mimetype' => strtolower($attachment['mimetype']),
                 'download' => !empty($_GET['_download']),
                 'part'     => $part,
             ));
 
             if ($plugin['abort'])
                 exit;
 
             $mimetype = $plugin['mimetype'];
             list($ctype_primary, $ctype_secondary) = explode('/', $mimetype);
 
             $browser = $this->rc->output->browser;
 
             // send download headers
             if ($plugin['download']) {
                 header("Content-Type: application/octet-stream");
                 if ($browser->ie)
                     header("Content-Type: application/force-download");
             }
             else if ($ctype_primary == 'text') {
                 header("Content-Type: text/$ctype_secondary");
             }
             else {
                 header("Content-Type: $mimetype");
                 header("Content-Transfer-Encoding: binary");
             }
 
             // display page, @TODO: support text/plain (and maybe some other text formats)
             if ($mimetype == 'text/html' && empty($_GET['_download'])) {
                 $OUTPUT = new rcmail_html_page();
                 // @TODO: use washtml on $body
                 $OUTPUT->write($plugin['body']);
             }
             else {
                 // don't kill the connection if download takes more than 30 sec.
                 @set_time_limit(0);
 
                 $filename = $attachment['name'];
                 $filename = preg_replace('[\r\n]', '', $filename);
 
                 if ($browser->ie && $browser->ver < 7)
                     $filename = rawurlencode(abbreviate_string($filename, 55));
                 else if ($browser->ie)
                     $filename = rawurlencode($filename);
                 else
                     $filename = addcslashes($filename, '"');
 
                 $disposition = !empty($_GET['_download']) ? 'attachment' : 'inline';
                 header("Content-Disposition: $disposition; filename=\"$filename\"");
 
                 echo $plugin['body'];
             }
 
             exit;
         }
 
         // if we arrive here, the requested part was not found
         header('HTTP/1.1 404 Not Found');
         exit;
     }
 
     /**
      * Show "loading..." page in attachment iframe
      */
     public function attachment_loading_page()
     {
         $url = str_replace('&_preload=1', '', $_SERVER['REQUEST_URI']);
         $message = $this->rc->gettext('loadingdata');
 
         header('Content-Type: text/html; charset=' . RCUBE_CHARSET);
         print "<html>\n<head>\n"
             . '<meta http-equiv="refresh" content="0; url='.rcube::Q($url).'">' . "\n"
             . '<meta http-equiv="content-type" content="text/html; charset='.RCUBE_CHARSET.'">' . "\n"
             . "</head>\n<body>\n$message\n</body>\n</html>";
         exit;
     }
 
     /**
      * Template object for attachment display frame
      */
     public function attachment_frame($attrib = array())
     {
         $mimetype = strtolower($this->attachment['mimetype']);
         list($ctype_primary, $ctype_secondary) = explode('/', $mimetype);
 
         $attrib['src'] = './?' . str_replace('_frame=', ($ctype_primary == 'text' ? '_show=' : '_preload='), $_SERVER['QUERY_STRING']);
 
         $this->rc->output->add_gui_object('attachmentframe', $attrib['id']);
 
         return html::iframe($attrib);
     }
 
     /**
      *
      */
     public function attachment_header($attrib = array())
     {
         $rcmail  = rcmail::get_instance();
         $dl_link = strtolower($attrib['downloadlink']) == 'true';
         $dl_url  = $this->rc->url(array('_frame' => null, '_download' => 1) + $_GET);
         $table   = new html_table(array('cols' => $dl_link ? 3 : 2));
 
         if (!empty($this->attachment['name'])) {
             $table->add('title', rcube::Q($this->rc->gettext('filename')));
             $table->add('header', rcube::Q($this->attachment['name']));
 
             if ($dl_link) {
                 $table->add('download-link', html::a($dl_url, rcube::Q($this->rc->gettext('download'))));
             }
         }
 
         if (!empty($this->attachment['mimetype'])) {
             $table->add('title', rcube::Q($this->rc->gettext('type')));
             $table->add('header', rcube::Q($this->attachment['mimetype']));
         }
 
         if (!empty($this->attachment['size'])) {
             $table->add('title', rcube::Q($this->rc->gettext('filesize')));
             $table->add('header', rcube::Q($this->rc->show_bytes($this->attachment['size'])));
         }
 
         $this->rc->output->set_env('attachment_download_url', $dl_url);
 
         return $table->show($attrib);
     }
 }
diff --git a/plugins/libkolab/lib/kolab_bonnie_api.php b/plugins/libkolab/lib/kolab_bonnie_api.php
index 6905dcaa..c4368e2c 100644
--- a/plugins/libkolab/lib/kolab_bonnie_api.php
+++ b/plugins/libkolab/lib/kolab_bonnie_api.php
@@ -1,97 +1,96 @@
 <?php
 
 /**
  * Provider class for accessing historic groupware object data through the Bonnie service
  *
  * API Specification at https://wiki.kolabsys.com/User:Bruederli/Draft:Bonnie_Client_API
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class kolab_bonnie_api
 {
     public $ready = false;
 
     private $config = array();
     private $client = null;
 
 
     /**
      * Default constructor
      */
     public function __construct($config)
     {
         $this->config = $config;
 
         $this->client = new kolab_bonnie_api_client($config['uri'], $config['timeout'] ?: 30, (bool)$config['debug']);
 
         $this->client->set_secret($config['secret']);
         $this->client->set_authentication($config['user'], $config['pass']);
         $this->client->set_request_user(rcube::get_instance()->get_user_name());
 
         $this->ready = !empty($config['secret']) && !empty($config['user']) && !empty($config['pass']);
     }
 
     /**
      * Wrapper function for <object>.changelog() API call
      */
     public function changelog($type, $uid, $mailbox, $msguid=null)
     {
         return $this->client->execute($type.'.changelog', array('uid' => $uid, 'mailbox' => $mailbox, 'msguid' => $msguid));
     }
 
     /**
      * Wrapper function for <object>.diff() API call
      */
     public function diff($type, $uid, $rev1, $rev2, $mailbox, $msguid=null, $instance=null)
     {
         return $this->client->execute($type.'.diff', array(
           'uid' => $uid,
           'rev1' => $rev1,
           'rev2' => $rev2,
           'mailbox' => $mailbox,
           'msguid' => $msguid,
           'instance' => $instance,
         ));
     }
 
     /**
      * Wrapper function for <object>.get() API call
      */
     public function get($type, $uid, $rev, $mailbox, $msguid=null)
     {
       return $this->client->execute($type.'.get', array('uid' => $uid, 'rev' => $rev, 'mailbox' => $mailbox, 'msguid' => $msguid));
     }
 
     /**
      * Wrapper function for <object>.rawdata() API call
      */
     public function rawdata($type, $uid, $rev, $mailbox, $msguid=null)
     {
       return $this->client->execute($type.'.rawdata', array('uid' => $uid, 'rev' => $rev, 'mailbox' => $mailbox, 'msguid' => $msguid));
     }
 
     /**
      * Generic wrapper for direct API calls
      */
     public function _execute($method, $params = array())
     {
         return $this->client->execute($method, $params);
     }
-
-}
\ No newline at end of file
+}
diff --git a/plugins/libkolab/lib/kolab_bonnie_api_client.php b/plugins/libkolab/lib/kolab_bonnie_api_client.php
index bc209f41..a69aa05e 100644
--- a/plugins/libkolab/lib/kolab_bonnie_api_client.php
+++ b/plugins/libkolab/lib/kolab_bonnie_api_client.php
@@ -1,239 +1,238 @@
 <?php
 
 /**
  * JSON-RPC client class with some extra features for communicating with the Bonnie API service.
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class kolab_bonnie_api_client
 {
     /**
      * URL of the RPC endpoint
      * @var string
      */
     protected $url;
 
     /**
      * HTTP client timeout in seconds
      * @var integer
      */
     protected $timeout;
 
     /**
      * Debug flag
      * @var bool
      */
     protected $debug;
 
     /**
      * Username for authentication
      * @var string
      */
     protected $username;
 
     /**
      * Password for authentication
      * @var string
      */
     protected $password;
 
     /**
      * Secret key for request signing
      * @var string
      */
     protected $secret;
 
     /**
      * Default HTTP headers to send to the server
      * @var array
      */
     protected $headers = array(
         'Connection' => 'close',
         'Content-Type' => 'application/json',
         'Accept' => 'application/json',
     );
 
     /**
      * Constructor
      *
      * @param  string  $url      Server URL
      * @param  integer $timeout  Request timeout
      * @param  bool    $debug    Enabled debug logging
      * @param  array   $headers  Custom HTTP headers
      */
     public function __construct($url, $timeout = 5, $debug = false, $headers = array())
     {
         $this->url = $url;
         $this->timeout = $timeout;
         $this->debug = $debug;
         $this->headers = array_merge($this->headers, $headers);
     }
 
     /**
      * Setter for secret key for request signing
      */
     public function set_secret($secret)
     {
         $this->secret = $secret;
     }
 
     /**
      * Setter for the X-Request-User header
      */
     public function set_request_user($username)
     {
         $this->headers['X-Request-User'] = $username;
     }
 
     /**
      * Set authentication parameters
      *
      * @param  string $username  Username
      * @param  string $password  Password
      */
     public function set_authentication($username, $password)
     {
         $this->username = $username;
         $this->password = $password;
     }
 
     /**
      * Automatic mapping of procedures
      *
      * @param  string $method  Procedure name
      * @param  array  $params  Procedure arguments
      * @return mixed
      */
     public function __call($method, $params)
     {
         return $this->execute($method, $params);
     }
 
     /**
      * Execute an RPC command
      *
      * @param  string $method  Procedure name
      * @param  array  $params  Procedure arguments
      * @return mixed
      */
     public function execute($method, array $params = array())
     {
         $id = mt_rand();
 
         $payload = array(
             'jsonrpc' => '2.0',
             'method' => $method,
             'id' => $id,
         );
 
         if (!empty($params)) {
             $payload['params'] = $params;
         }
 
         $result = $this->send_request($payload, $method != 'system.keygen');
 
         if (isset($result['id']) && $result['id'] == $id && array_key_exists('result', $result)) {
             return $result['result'];
         }
         else if (isset($result['error'])) {
             $this->_debug('ERROR', $result);
         }
 
         return null;
     }
 
     /**
      * Do the HTTP request
      *
      * @param  string  $payload  Data to send
      */
     protected function send_request($payload, $sign = true)
     {
         try {
             $payload_ = json_encode($payload);
 
             // add request signature
             if ($sign && !empty($this->secret)) {
                 $this->headers['X-Request-Sign'] = $this->request_signature($payload_);
             }
             else if ($this->headers['X-Request-Sign']) {
                 unset($this->headers['X-Request-Sign']);
             }
 
             $this->_debug('REQUEST', $payload, $this->headers);
             $request = libkolab::http_request($this->url, 'POST', array('timeout' => $this->timeout));
             $request->setHeader($this->headers);
             $request->setAuth($this->username, $this->password);
             $request->setBody($payload_);
 
             $response = $request->send();
 
             if ($response->getStatus() == 200) {
                 $result = json_decode($response->getBody(), true);
                 $this->_debug('RESPONSE', $result);
             }
             else {
                 throw new Exception(sprintf("HTTP %d %s", $response->getStatus(), $response->getReasonPhrase()));
             }
         }
         catch (Exception $e) {
             rcube::raise_error(array(
                 'code' => 500,
                 'type' => 'php',
                 'message' => "Bonnie API request failed: " . $e->getMessage(),
             ), true);
 
             return array('id' => $payload['id'], 'error' => $e->getMessage(), 'code' => -32000);
         }
 
         return is_array($result) ? $result : array();
     }
 
     /**
      * Compute the hmac signature for the current event payload using
      * the secret key configured for this API client
      *
      * @param string $data The request payload data
      * @return string The request signature
      */
     protected function request_signature($data)
     {
         // TODO: get the session key with a system.keygen call
         return hash_hmac('sha256', $this->headers['X-Request-User'] . ':' . $data, $this->secret);
     }
 
     /**
      * Write debug log
      */
     protected function _debug(/* $message, $data1, data2, ...*/)
     {
         if (!$this->debug)
             return;
 
         $args = func_get_args();
 
         $msg = array();
         foreach ($args as $arg) {
             $msg[] = !is_string($arg) ? var_export($arg, true) : $arg;
         }
 
         rcube::write_log('bonnie', join(";\n", $msg));
     }
-
-}
\ No newline at end of file
+}
diff --git a/plugins/libkolab/lib/kolab_format_task.php b/plugins/libkolab/lib/kolab_format_task.php
index cb35f98d..bc57e6b9 100644
--- a/plugins/libkolab/lib/kolab_format_task.php
+++ b/plugins/libkolab/lib/kolab_format_task.php
@@ -1,155 +1,154 @@
 <?php
 
 /**
  * Kolab Task (ToDo) model class
  *
  * @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 kolab_format_task extends kolab_format_xcal
 {
     public $CTYPEv2 = 'application/x-vnd.kolab.task';
 
     public static $scheduling_properties = array('start', 'due', 'summary', 'status');
 
     protected $objclass = 'Todo';
     protected $read_func = 'readTodo';
     protected $write_func = 'writeTodo';
 
     /**
      * Default constructor
      */
     function __construct($data = null, $version = 3.0)
     {
         parent::__construct(is_string($data) ? $data : null, $version);
 
         // copy static property overriden by this class
         $this->_scheduling_properties = self::$scheduling_properties;
     }
 
     /**
      * Set properties to the kolabformat object
      *
      * @param array  Object data as hash array
      */
     public function set(&$object)
     {
         // set common xcal properties
         parent::set($object);
 
         $this->obj->setPercentComplete(intval($object['complete']));
 
         $status = kolabformat::StatusUndefined;
         if ($object['complete'] == 100 && !array_key_exists('status', $object))
             $status = kolabformat::StatusCompleted;
         else if ($object['status'] && array_key_exists($object['status'], $this->status_map))
             $status = $this->status_map[$object['status']];
         $this->obj->setStatus($status);
 
         $this->obj->setStart(self::get_datetime($object['start'], null, $object['start']->_dateonly));
         $this->obj->setDue(self::get_datetime($object['due'], null, $object['due']->_dateonly));
 
         $related = new vectors;
         if (!empty($object['parent_id']))
             $related->push($object['parent_id']);
         $this->obj->setRelatedTo($related);
 
         // cache this data
         $this->data = $object;
         unset($this->data['_formatobj']);
     }
 
     /**
      *
      */
     public function is_valid()
     {
         return !$this->formaterror && ($this->data || (is_object($this->obj) && $this->obj->isValid()));
     }
 
     /**
      * Convert the Configuration object into a hash array data structure
      *
      * @param array Additional data for merge
      *
      * @return array  Config object data as hash array
      */
     public function to_array($data = array())
     {
         // return cached result
         if (!empty($this->data))
             return $this->data;
 
         // read common xcal props
         $object = parent::to_array($data);
 
         $object['complete'] = intval($this->obj->percentComplete());
 
         // if due date is set
         if ($due = $this->obj->due())
             $object['due'] = self::php_datetime($due);
 
         // related-to points to parent task; we only support one relation
         $related = self::vector2array($this->obj->relatedTo());
         if (count($related))
             $object['parent_id'] = $related[0];
 
         // TODO: map more properties
 
         $this->data = $object;
         return $this->data;
     }
 
     /**
      * Return the reference date for recurrence and alarms
      *
      * @return mixed DateTime instance of null if no refdate is available
      */
     public function get_reference_date()
     {
         if ($this->data['due'] && $this->data['due'] instanceof DateTime) {
             return $this->data['due'];
         }
 
         return self::php_datetime($this->obj->due()) ?: parent::get_reference_date();
     }
 
     /**
      * 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($obj = null)
     {
         $tags = parent::get_tags($obj);
         $object = $obj ?: $this->data;
 
         if ($object['status'] == 'COMPLETED' || ($object['complete'] == 100 && empty($object['status'])))
             $tags[] = 'x-complete';
 
         if ($object['priority'] == 1)
             $tags[] = 'x-flagged';
 
         if ($object['parent_id'])
             $tags[] = 'x-parent:' . $object['parent_id'];
 
         return array_unique($tags);
     }
-
 }
diff --git a/plugins/libkolab/lib/kolab_storage_dataset.php b/plugins/libkolab/lib/kolab_storage_dataset.php
index 9ddf3f9f..9f39b12e 100644
--- a/plugins/libkolab/lib/kolab_storage_dataset.php
+++ b/plugins/libkolab/lib/kolab_storage_dataset.php
@@ -1,154 +1,153 @@
 <?php
 
 /**
  * Dataset class providing the results of a select operation on a kolab_storage_folder.
  *
  * Can be used as a normal array as well as an iterator in foreach() loops.
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2014, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class kolab_storage_dataset implements Iterator, ArrayAccess, Countable
 {
     private $cache;  // kolab_storage_cache instance to use for fetching data
     private $memlimit = 0;
     private $buffer = false;
     private $index = array();
     private $data = array();
     private $iteratorkey = 0;
     private $error = null;
 
     /**
      * Default constructor
      *
      * @param object kolab_storage_cache instance to be used for fetching objects upon access
      */
     public function __construct($cache)
     {
         $this->cache = $cache;
 
         // enable in-memory buffering up until 1/5 of the available memory
         if (function_exists('memory_get_usage')) {
             $this->memlimit = parse_bytes(ini_get('memory_limit')) / 5;
             $this->buffer = true;
         }
     }
 
     /**
      * Return error state
      */
     public function is_error()
     {
         return !empty($this->error);
     }
 
     /**
      * Set error state
      */
     public function set_error($err)
     {
         $this->error = $err;
     }
 
 
     /*** Implement PHP Countable interface ***/
 
     public function count()
     {
         return count($this->index);
     }
 
 
     /*** Implement PHP ArrayAccess interface ***/
 
     public function offsetSet($offset, $value)
     {
         $uid = $value['_msguid'];
 
         if (is_null($offset)) {
             $offset = count($this->index);
             $this->index[] = $uid;
         }
         else {
             $this->index[$offset] = $uid;
         }
 
         // keep full payload data in memory if possible
         if ($this->memlimit && $this->buffer && isset($value['_mailbox'])) {
             $this->data[$offset] = $value;
 
             // check memory usage and stop buffering
             if ($offset % 10 == 0) {
                 $this->buffer = memory_get_usage() < $this->memlimit;
             }
         }
     }
 
     public function offsetExists($offset)
     {
         return isset($this->index[$offset]);
     }
 
     public function offsetUnset($offset)
     {
         unset($this->index[$offset]);
     }
 
     public function offsetGet($offset)
     {
         if (isset($this->data[$offset])) {
             return $this->data[$offset];
         }
         else if ($msguid = $this->index[$offset]) {
             return $this->cache->get($msguid);
         }
 
         return null;
     }
 
 
     /*** Implement PHP Iterator interface ***/
 
     public function current()
     {
         return $this->offsetGet($this->iteratorkey);
     }
 
     public function key()
     {
         return $this->iteratorkey;
     }
 
     public function next()
     {
         $this->iteratorkey++;
         return $this->valid();
     }
 
     public function rewind()
     {
         $this->iteratorkey = 0;
     }
 
     public function valid()
     {
         return !empty($this->index[$this->iteratorkey]);
     }
-
 }