roundcubemail-plugins-kolab/plugins/calendar/drivers/kolab/kolab_driver.php

<?php

/**
 * Kolab driver for the Calendar plugin
 *
 * @version @package_version@
 * @author Thomas Bruederli <bruederli@kolabsys.com>
 * @author Aleksander Machniak <machniak@kolabsys.com>
 *
 * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

class kolab_driver extends calendar_driver
{
  const INVITATIONS_CALENDAR_PENDING  = '--invitation--pending';
  const INVITATIONS_CALENDAR_DECLINED = '--invitation--declined';

  // features this backend supports
  public $alarms = true;
  public $attendees = true;
  public $freebusy = true;
  public $attachments = true;
  public $undelete = true;
  public $alarm_types = array('DISPLAY','AUDIO');
  public $categoriesimmutable = true;

  private $rc;
  private $cal;
  private $calendars;
  private $has_writeable = false;
  private $freebusy_trigger = false;
  private $bonnie_api = false;

  /**
   * Default constructor
   */
  public function __construct($cal)
  {
    $cal->require_plugin('libkolab');

    // load helper classes *after* libkolab has been loaded (#3248)
    require_once(dirname(__FILE__) . '/kolab_calendar.php');
    require_once(dirname(__FILE__) . '/kolab_user_calendar.php');
    require_once(dirname(__FILE__) . '/kolab_invitation_calendar.php');

    $this->cal = $cal;
    $this->rc  = $cal->rc;

    $this->cal->register_action('push-freebusy', array($this, 'push_freebusy'));
    $this->cal->register_action('calendar-acl', array($this, 'calendar_acl'));

    $this->freebusy_trigger = $this->rc->config->get('calendar_freebusy_trigger', false);

    if (kolab_storage::$version == '2.0') {
        $this->alarm_types = array('DISPLAY');
        $this->alarm_absolute = false;
    }

    // get configuration for the Bonnie API
    $this->bonnie_api = libkolab::get_bonnie_api();

    // calendar uses fully encoded identifiers
    kolab_storage::$encode_ids = true;
  }


  /**
   * Read available calendars from server
   */
  private function _read_calendars()
  {
    // already read sources
    if (isset($this->calendars))
      return $this->calendars;

    // get all folders that have "event" type, sorted by namespace/name
    $folders = kolab_storage::sort_folders(kolab_storage::get_folders('event') + kolab_storage::get_user_folders('event', true));

    $this->calendars = array();
    foreach ($folders as $folder) {
      if ($folder instanceof kolab_storage_folder_user) {
        $calendar = new kolab_user_calendar($folder->name, $this->cal);
        $calendar->subscriptions = count($folder->children) > 0;
      }
      else {
        $calendar = new kolab_calendar($folder->name, $this->cal);
      }

      if ($calendar->ready) {
        $this->calendars[$calendar->id] = $calendar;
        if ($calendar->editable)
          $this->has_writeable = true;
      }
    }

    return $this->calendars;
  }

  /**
   * Get a list of available calendars from this source
   *
   * @param integer $filter Bitmask defining filter criterias
   * @param object $tree   Reference to hierarchical folder tree object
   *
   * @return array List of calendars
   */
  public function list_calendars($filter = 0, &$tree = null)
  {
    $this->_read_calendars();

    // attempt to create a default calendar for this user
    if (!$this->has_writeable) {
      if ($this->create_calendar(array('name' => 'Calendar', 'color' => 'cc0000'))) {
        unset($this->calendars);
        $this->_read_calendars();
      }
    }

    $delim = $this->rc->get_storage()->get_hierarchy_delimiter();
    $folders = $this->filter_calendars($filter);
    $calendars = array();

    // include virtual folders for a full folder tree
    if (!is_null($tree))
      $folders = kolab_storage::folder_hierarchy($folders, $tree);

    foreach ($folders as $id => $cal) {
      $fullname = $cal->get_name();
      $listname = $cal->get_foldername();
      $imap_path = explode($delim, $cal->name);

      // find parent
      do {
        array_pop($imap_path);
        $parent_id = kolab_storage::folder_id(join($delim, $imap_path));
      }
      while (count($imap_path) > 1 && !$this->calendars[$parent_id]);

      // restore "real" parent ID
      if ($parent_id && !$this->calendars[$parent_id]) {
          $parent_id = kolab_storage::folder_id($cal->get_parent());
      }

      // turn a kolab_storage_folder object into a kolab_calendar
      if ($cal instanceof kolab_storage_folder) {
          $cal = new kolab_calendar($cal->name, $this->cal);
          $this->calendars[$cal->id] = $cal;
      }

      // special handling for user or virtual folders
      if ($cal instanceof kolab_storage_folder_user) {
        $calendars[$cal->id] = array(
          'id'       => $cal->id,
          'name'     => $fullname,
          'listname' => $listname,
          'editname' => $cal->get_foldername(),
          'color'    => $cal->get_color(),
          'active'   => $cal->is_active(),
          'title'    => $cal->get_owner(),
          'owner'    => $cal->get_owner(),
          'history'  => false,
          'virtual'  => false,
          'editable' => false,
          'group'     => 'other',
          'class'     => 'user',
          'removable' => true,
        );
      }
      else if ($cal->virtual) {
        $calendars[$cal->id] = array(
          'id' => $cal->id,
          'name' => $fullname,
          'listname' => $listname,
          'editname' => $cal->get_foldername(),
          'virtual'  => true,
          'editable' => false,
          'group'     => $cal->get_namespace(),
          'class'     => 'folder',
        );
      }
      else {
        $calendars[$cal->id] = array(
          'id'       => $cal->id,
          'name'     => $fullname,
          'listname' => $listname,
          'editname' => $cal->get_foldername(),
          'title'    => $cal->get_title(),
          'color'    => $cal->get_color(),
          'editable' => $cal->editable,
          'rights'    => $cal->rights,
          'showalarms' => $cal->alarms,
          'history'  => !empty($this->bonnie_api),
          'group'    => $cal->get_namespace(),
          'default'  => $cal->default,
          'active'   => $cal->is_active(),
          'owner'    => $cal->get_owner(),
          'children' => true,  // TODO: determine if that folder indeed has child folders
          'parent'   => $parent_id,
          'subtype'  => $cal->subtype,
          'caldavurl' => $cal->get_caldav_url(),
          'removable' => !$cal->default,
        );
      }

      if ($cal->subscriptions) {
        $calendars[$cal->id]['subscribed'] = $cal->is_subscribed();
      }
    }

    // list virtual calendars showing invitations
    if ($this->rc->config->get('kolab_invitation_calendars')) {
      foreach (array(self::INVITATIONS_CALENDAR_PENDING, self::INVITATIONS_CALENDAR_DECLINED) as $id) {
        $cal = new kolab_invitation_calendar($id, $this->cal);
        $this->calendars[$cal->id] = $cal;
        if (!($filter & self::FILTER_ACTIVE) || $cal->is_active()) {
          $calendars[$id] = array(
            'id'       => $cal->id,
            'name'     => $cal->get_name(),
            'listname' => $cal->get_name(),
            'editname' => $cal->get_foldername(),
            'title'    => $cal->get_title(),
            'color'    => $cal->get_color(),
            'editable' => $cal->editable,
            'rights'    => $cal->rights,
            'showalarms' => $cal->alarms,
            'history'  => !empty($this->bonnie_api),
            'group'    => 'x-invitations',
            'default'  => false,
            'active'   => $cal->is_active(),
            'owner'    => $cal->get_owner(),
            'children' => false,
          );

          if ($id == self::INVITATIONS_CALENDAR_PENDING) {
            $calendars[$id]['counts'] = true;
          }

          if (is_object($tree)) {
            $tree->children[] = $cal;
          }
        }
      }
    }

    // append the virtual birthdays calendar
    if ($this->rc->config->get('calendar_contact_birthdays', false)) {
      $id = self::BIRTHDAY_CALENDAR_ID;
      $prefs = $this->rc->config->get('kolab_calendars', array());  // read local prefs
      if (!($filter & self::FILTER_ACTIVE) || $prefs[$id]['active']) {
        $calendars[$id] = array(
          'id'         => $id,
          'name'       => $this->cal->gettext('birthdays'),
          'listname'   => $this->cal->gettext('birthdays'),
          'color'      => $prefs[$id]['color'] ?: '87CEFA',
          'active'     => (bool)$prefs[$id]['active'],
          'showalarms' => (bool)$this->rc->config->get('calendar_birthdays_alarm_type'),
          'group'      => 'x-birthdays',
          'editable'  => false,
          'default'    => false,
          'children'   => false,
          'history'    => false,
        );
      }
    }

    return $calendars;
  }

  /**
   * Get list of calendars according to specified filters
   *
   * @param integer Bitmask defining restrictions. See FILTER_* constants for possible values.
   *
   * @return array List of calendars
   */
  protected function filter_calendars($filter)
  {
    $this->_read_calendars();

    $calendars = array();

    $plugin = $this->rc->plugins->exec_hook('calendar_list_filter', array(
      'list'      => $this->calendars,
      'calendars' => $calendars,
      'filter'    => $filter,
      'editable'  => ($filter & self::FILTER_WRITEABLE),
      'insert'    => ($filter & self::FILTER_INSERTABLE),
      'active'    => ($filter & self::FILTER_ACTIVE),
      'personal'  => ($filter & self::FILTER_PERSONAL)
    ));

    if ($plugin['abort']) {
      return $plugin['calendars'];
    }

    foreach ($this->calendars as $cal) {
      if (!$cal->ready) {
        continue;
      }
      if (($filter & self::FILTER_WRITEABLE) && !$cal->editable) {
        continue;
      }
      if (($filter & self::FILTER_INSERTABLE) && !$cal->insert) {
        continue;
      }
      if (($filter & self::FILTER_ACTIVE) && !$cal->is_active()) {
        continue;
      }
      if (($filter & self::FILTER_PRIVATE) && $cal->subtype != 'private') {
        continue;
      }
      if (($filter & self::FILTER_CONFIDENTIAL) && $cal->subtype != 'confidential') {
        continue;
      }
      if (($filter & self::FILTER_PERSONAL) && $cal->get_namespace() != 'personal') {
        continue;
      }
      $calendars[$cal->id] = $cal;
    }

    return $calendars;
  }


  /**
   * Get the kolab_calendar instance for the given calendar ID
   *
   * @param string Calendar identifier (encoded imap folder name)
   * @return object kolab_calendar Object nor null if calendar doesn't exist
   */
  public function get_calendar($id)
  {
    $this->_read_calendars();

    // create calendar object if necesary
    if (!$this->calendars[$id] && in_array($id, array(self::INVITATIONS_CALENDAR_PENDING, self::INVITATIONS_CALENDAR_DECLINED))) {
      $this->calendars[$id] = new kolab_invitation_calendar($id, $this->cal);
    }
    else if (!$this->calendars[$id] && $id !== self::BIRTHDAY_CALENDAR_ID) {
      $calendar = kolab_calendar::factory($id, $this->cal);
      if ($calendar->ready)
        $this->calendars[$calendar->id] = $calendar;
    }

    return $this->calendars[$id];
  }

  /**
   * Create a new calendar assigned to the current user
   *
   * @param array Hash array with calendar properties
   *    name: Calendar name
   *   color: The color of the calendar
   * @return mixed ID of the calendar on success, False on error
   */
  public function create_calendar($prop)
  {
    $prop['type'] = 'event';
    $prop['active'] = true;
    $prop['subscribed'] = true;
    $folder = kolab_storage::folder_update($prop);

    if ($folder === false) {
      $this->last_error = $this->cal->gettext(kolab_storage::$last_error);
      return false;
    }

    // create ID
    $id = kolab_storage::folder_id($folder);

    // save color in user prefs (temp. solution)
    $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());

    if (isset($prop['color']))
      $prefs['kolab_calendars'][$id]['color'] = $prop['color'];
    if (isset($prop['showalarms']))
      $prefs['kolab_calendars'][$id]['showalarms'] = $prop['showalarms'] ? true : false;

    if ($prefs['kolab_calendars'][$id])
      $this->rc->user->save_prefs($prefs);

    return $id;
  }


  /**
   * Update properties of an existing calendar
   *
   * @see calendar_driver::edit_calendar()
   */
  public function edit_calendar($prop)
  {
    if ($prop['id'] && ($cal = $this->get_calendar($prop['id']))) {
      $id = $cal->update($prop);
    }
    else {
      $id = $prop['id'];
    }

    // fallback to local prefs
    $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
    unset($prefs['kolab_calendars'][$prop['id']]['color'], $prefs['kolab_calendars'][$prop['id']]['showalarms']);

    if (isset($prop['color']))
      $prefs['kolab_calendars'][$id]['color'] = $prop['color'];

    if (isset($prop['showalarms']) && $id == self::BIRTHDAY_CALENDAR_ID)
      $prefs['calendar_birthdays_alarm_type'] = $prop['showalarms'] ? $this->alarm_types[0] : '';
    else if (isset($prop['showalarms']))
      $prefs['kolab_calendars'][$id]['showalarms'] = $prop['showalarms'] ? true : false;

    if (!empty($prefs['kolab_calendars'][$id]))
      $this->rc->user->save_prefs($prefs);

    return true;
  }


  /**
   * Set active/subscribed state of a calendar
   *
   * @see calendar_driver::subscribe_calendar()
   */
  public function subscribe_calendar($prop)
  {
    if ($prop['id'] && ($cal = $this->get_calendar($prop['id'])) && is_object($cal->storage)) {
      $ret = false;
      if (isset($prop['permanent']))
        $ret |= $cal->storage->subscribe(intval($prop['permanent']));
      if (isset($prop['active']))
        $ret |= $cal->storage->activate(intval($prop['active']));

      // apply to child folders, too
      if ($prop['recursive']) {
        foreach ((array)kolab_storage::list_folders($cal->storage->name, '*', 'event') as $subfolder) {
          if (isset($prop['permanent']))
            ($prop['permanent'] ? kolab_storage::folder_subscribe($subfolder) : kolab_storage::folder_unsubscribe($subfolder));
          if (isset($prop['active']))
            ($prop['active'] ? kolab_storage::folder_activate($subfolder) : kolab_storage::folder_deactivate($subfolder));
        }
      }
      return $ret;
    }
    else {
      // save state in local prefs
      $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
      $prefs['kolab_calendars'][$prop['id']]['active'] = (bool)$prop['active'];
      $this->rc->user->save_prefs($prefs);
      return true;
    }

    return false;
  }


  /**
   * Delete the given calendar with all its contents
   *
   * @see calendar_driver::delete_calendar()
   */
  public function delete_calendar($prop)
  {
    if ($prop['id'] && ($cal = $this->get_calendar($prop['id']))) {
      $folder = $cal->get_realname();
      // TODO: unsubscribe if no admin rights
      if (kolab_storage::folder_delete($folder)) {
        // remove color in user prefs (temp. solution)
        $prefs['kolab_calendars'] = $this->rc->config->get('kolab_calendars', array());
        unset($prefs['kolab_calendars'][$prop['id']]);

        $this->rc->user->save_prefs($prefs);
        return true;
      }
      else
        $this->last_error = kolab_storage::$last_error;
    }

    return false;
  }


  /**
   * Search for shared or otherwise not listed calendars the user has access
   *
   * @param string Search string
   * @param string Section/source to search
   * @return array List of calendars
   */
  public function search_calendars($query, $source)
  {
    if (!kolab_storage::setup())
      return array();

    $this->calendars = array();
    $this->search_more_results = false;

    // find unsubscribed IMAP folders that have "event" type
    if ($source == 'folders') {
      foreach ((array)kolab_storage::search_folders('event', $query, array('other')) as $folder) {
        $calendar = new kolab_calendar($folder->name, $this->cal);
        $this->calendars[$calendar->id] = $calendar;
      }
    }
    // find other user's virtual calendars
    else if ($source == 'users') {
      $limit = $this->rc->config->get('autocomplete_max', 15) * 2;  // we have slightly more space, so display twice the number
      foreach (kolab_storage::search_users($query, 0, array(), $limit, $count) as $user) {
        $calendar = new kolab_user_calendar($user, $this->cal);
        $this->calendars[$calendar->id] = $calendar;

        // search for calendar folders shared by this user
        foreach (kolab_storage::list_user_folders($user, 'event', false) as $foldername) {
          $cal = new kolab_calendar($foldername, $this->cal);
          $this->calendars[$cal->id] = $cal;
          $calendar->subscriptions = true;
        }
      }

      if ($count > $limit) {
        $this->search_more_results = true;
      }
    }

    // don't list the birthday calendar
    $this->rc->config->set('calendar_contact_birthdays', false);
    $this->rc->config->set('kolab_invitation_calendars', false);

    return $this->list_calendars();
  }


  /**
   * Fetch a single event
   *
   * @see calendar_driver::get_event()
   * @return array Hash array with event properties, false if not found
   */
  public function get_event($event, $scope = 0, $full = false)
  {
    if (is_array($event)) {
      $id = $event['id'] ?: $event['uid'];
      $cal = $event['calendar'];

      // we're looking for a recurring instance: expand the ID to our internal convention for recurring instances
      if (!$event['id'] && $event['_instance']) {
        $id .= '-' . $event['_instance'];
      }
    }
    else {
      $id = $event;
    }

    if ($cal) {
      if ($storage = $this->get_calendar($cal)) {
        $result = $storage->get_event($id);
        return self::to_rcube_event($result);
      }
      // get event from the address books birthday calendar
      else if ($cal == self::BIRTHDAY_CALENDAR_ID) {
        return $this->get_birthday_event($id);
      }
    }
    // iterate over all calendar folders and search for the event ID
    else {
      foreach ($this->filter_calendars($scope) as $calendar) {
        if ($result = $calendar->get_event($id)) {
          return self::to_rcube_event($result);
        }
      }
    }

    return false;
  }

  /**
   * Add a single event to the database
   *
   * @see calendar_driver::new_event()
   */
  public function new_event($event)
  {
    if (!$this->validate($event))
      return false;

    $event = self::from_rcube_event($event);

    if (!$event['calendar']) {
      $this->_read_calendars();
      $event['calendar'] = reset(array_keys($this->calendars));
    }

    if ($storage = $this->get_calendar($event['calendar'])) {
      // if this is a recurrence instance, append as exception to an already existing object for this UID
      if (!empty($event['recurrence_date']) && ($master = $storage->get_event($event['uid']))) {
        self::add_exception($master, $event);
        $success = $storage->update_event($master);
      }
      else {
        $success = $storage->insert_event($event);
      }

      if ($success && $this->freebusy_trigger) {
        $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
        $this->freebusy_trigger = false; // disable after first execution (#2355)
      }
      
      return $success;
    }

    return false;
  }

  /**
   * Update an event entry with the given data
   *
   * @see calendar_driver::new_event()
   * @return boolean True on success, False on error
   */
  public function edit_event($event)
  {
     if (!($storage = $this->get_calendar($event['calendar'])))
       return false;

    return $this->update_event(self::from_rcube_event($event, $storage->get_event($event['id'])));
  }

  /**
   * Extended event editing with possible changes to the argument
   *
   * @param array  Hash array with event properties
   * @param string New participant status
   * @param array  List of hash arrays with updated attendees
   * @return boolean True on success, False on error
   */
  public function edit_rsvp(&$event, $status, $attendees)
  {
    $update_event = $event;

    // apply changes to master (and all exceptions)
    if ($event['_savemode'] == 'all' && $event['recurrence_id']) {
      if ($storage = $this->get_calendar($event['calendar'])) {
        $update_event = $storage->get_event($event['recurrence_id']);
        $update_event['_savemode'] = $event['_savemode'];
        $update_event['id'] = $update_event['uid'];
        unset($update_event['recurrence_id']);
        calendar::merge_attendee_data($update_event, $attendees);
      }
    }

    if ($ret = $this->update_attendees($update_event, $attendees)) {
      // replace with master event (for iTip reply)
      $event = self::to_rcube_event($update_event);

      // re-assign to the according (virtual) calendar
      if ($this->rc->config->get('kolab_invitation_calendars')) {
        if (strtoupper($status) == 'DECLINED')
          $event['calendar'] = self::INVITATIONS_CALENDAR_DECLINED;
        else if (strtoupper($status) == 'NEEDS-ACTION')
          $event['calendar'] = self::INVITATIONS_CALENDAR_PENDING;
        else if ($event['_folder_id'])
          $event['calendar'] = $event['_folder_id'];
      }
    }

    return $ret;
  }

  /**
   * Update the participant status for the given attendees
   *
   * @see calendar_driver::update_attendees()
   */
  public function update_attendees(&$event, $attendees)
  {
    // for this-and-future updates, merge the updated attendees onto all exceptions in range
    if (($event['_savemode'] == 'future' && $event['recurrence_id']) || (!empty($event['recurrence']) && !$event['recurrence_id'])) {
      if (!($storage = $this->get_calendar($event['calendar'])))
        return false;

      // load master event
      $master = $event['recurrence_id'] ? $storage->get_event($event['recurrence_id']) : $event;

      // apply attendee update to each existing exception
      if ($master['recurrence'] && !empty($master['recurrence']['EXCEPTIONS'])) {
        $saved = false;
        foreach ($master['recurrence']['EXCEPTIONS'] as $i => $exception) {
          // merge the new event properties onto future exceptions
          if ($exception['_instance'] >= strval($event['_instance'])) {
            calendar::merge_attendee_data($master['recurrence']['EXCEPTIONS'][$i], $attendees);
          }
          // update a specific instance
          if ($exception['_instance'] == $event['_instance'] && $exception['thisandfuture']) {
            $saved = true;
          }
        }

        // add the given event as new exception
        if (!$saved && $event['id'] != $master['id']) {
          $event['thisandfuture'] = true;
          $master['recurrence']['EXCEPTIONS'][] = $event;
        }

        // set link to top-level exceptions
        $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];

        return $this->update_event($master);
      }
    }

    // just update the given event (instance)
    return $this->update_event($event);
  }

  /**
   * Move a single event
   *
   * @see calendar_driver::move_event()
   * @return boolean True on success, False on error
   */
  public function move_event($event)
  {
    if (($storage = $this->get_calendar($event['calendar'])) && ($ev = $storage->get_event($event['id']))) {
      unset($ev['sequence']);
      self::clear_attandee_noreply($ev);
      return $this->update_event($event + $ev);
    }

    return false;
  }

  /**
   * Resize a single event
   *
   * @see calendar_driver::resize_event()
   * @return boolean True on success, False on error
   */
  public function resize_event($event)
  {
    if (($storage = $this->get_calendar($event['calendar'])) && ($ev = $storage->get_event($event['id']))) {
      unset($ev['sequence']);
      self::clear_attandee_noreply($ev);
      return $this->update_event($event + $ev);
    }

    return false;
  }

  /**
   * Remove a single event
   *
   * @param array   Hash array with event properties:
   *      id: Event identifier
   * @param boolean Remove record(s) irreversible (mark as deleted otherwise)
   *
   * @return boolean True on success, False on error
   */
  public function remove_event($event, $force = true)
  {
    $ret = true;
    $success = false;
    $savemode = $event['_savemode'];
    $decline  = $event['_decline'];

    if (($storage = $this->get_calendar($event['calendar'])) && ($event = $storage->get_event($event['id']))) {
      $event['_savemode'] = $savemode;
      $savemode = 'all';
      $master = $event;

      $this->rc->session->remove('calendar_restore_event_data');

      // read master if deleting a recurring event
      if ($event['recurrence'] || $event['recurrence_id'] || $event['isexception']) {
        $master = $storage->get_event($event['uid']);
        $savemode = $event['_savemode'] ?: ($event['_instance'] || $event['isexception'] ? 'current' : 'all');

        // force 'current' mode for single occurrences stored as exception
        if (!$event['recurrence'] && !$event['recurrence_id'] && $event['isexception'])
          $savemode = 'current';
      }

      // removing an exception instance
      if (($event['recurrence_id'] || $event['isexception']) && is_array($master['exceptions'])) {
        foreach ($master['exceptions'] as $i => $exception) {
          if ($exception['_instance'] == $event['_instance']) {
            unset($master['exceptions'][$i]);
            // set event date back to the actual occurrence
            if ($exception['recurrence_date'])
              $event['start'] = $exception['recurrence_date'];
          }
        }

        if (is_array($master['recurrence'])) {
          $master['recurrence']['EXCEPTIONS'] = &$master['exceptions'];
        }
      }

      switch ($savemode) {
        case 'current':
          $_SESSION['calendar_restore_event_data'] = $master;

          // removing the first instance => just move to next occurence
          if ($master['recurrence'] && $event['_instance'] == libcalendaring::recurrence_instance_identifier($master)) {
            $recurring = reset($storage->get_recurring_events($event, $event['start'], null, $event['id'].'-1'));

            // no future instances found: delete the master event (bug #1677)
            if (!$recurring['start']) {
              $success = $storage->delete_event($master, $force);
              break;
            }

            $master['start'] = $recurring['start'];
            $master['end'] = $recurring['end'];
            if ($master['recurrence']['COUNT'])
              $master['recurrence']['COUNT']--;
          }
          // remove the matching RDATE entry
          else if ($master['recurrence']['RDATE']) {
            foreach ($master['recurrence']['RDATE'] as $j => $rdate) {
              if ($rdate->format('Ymd') == $event['start']->format('Ymd')) {
                unset($master['recurrence']['RDATE'][$j]);
                break;
              }
            }
          }
          else {  // add exception to master event
            $master['recurrence']['EXDATE'][] = $event['start'];
          }
          $success = $storage->update_event($master);
          break;

        case 'future':
          $master['_instance'] = libcalendaring::recurrence_instance_identifier($master);
          if ($master['_instance'] != $event['_instance']) {
            $_SESSION['calendar_restore_event_data'] = $master;
            
            // set until-date on master event
            $master['recurrence']['UNTIL'] = clone $event['start'];
            $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
            unset($master['recurrence']['COUNT']);

            // if all future instances are deleted, remove recurrence rule entirely (bug #1677)
            if ($master['recurrence']['UNTIL']->format('Ymd') == $master['start']->format('Ymd')) {
              $master['recurrence'] = array();
            }
            // remove matching RDATE entries
            else if ($master['recurrence']['RDATE']) {
              foreach ($master['recurrence']['RDATE'] as $j => $rdate) {
                if ($rdate->format('Ymd') == $event['start']->format('Ymd')) {
                  $master['recurrence']['RDATE'] = array_slice($master['recurrence']['RDATE'], 0, $j);
                  break;
                }
              }
            }

            $success = $storage->update_event($master);
            $ret = $master['uid'];
            break;
          }

        default:  // 'all' is default
          // removing the master event with loose exceptions (not recurring though)
          if (!empty($event['recurrence_date']) && empty($master['recurrence']) && !empty($master['exceptions'])) {
            // make the first exception the new master
            $newmaster = array_shift($master['exceptions']);
            $newmaster['exceptions'] = $master['exceptions'];
            $newmaster['_attachments'] = $master['_attachments'];
            $newmaster['_mailbox'] = $master['_mailbox'];
            $newmaster['_msguid'] = $master['_msguid'];

            $success = $storage->update_event($newmaster);
          }
          else if ($decline && $this->rc->config->get('kolab_invitation_calendars')) {
            // don't delete but set PARTSTAT=DECLINED
            if ($this->cal->lib->set_partstat($master, 'DECLINED')) {
              $success = $storage->update_event($master);
            }
          }

          if (!$success)
            $success = $storage->delete_event($master, $force);
          break;
      }
    }
    
    if ($success && $this->freebusy_trigger)
      $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));

    return $success ? $ret : false;
  }

  /**
   * Restore a single deleted event
   *
   * @param array Hash array with event properties:
   *      id: Event identifier
   * @return boolean True on success, False on error
   */
  public function restore_event($event)
  {
    if ($storage = $this->get_calendar($event['calendar'])) {
      if (!empty($_SESSION['calendar_restore_event_data']))
        $success = $storage->update_event($_SESSION['calendar_restore_event_data']);
      else
        $success = $storage->restore_event($event);
      
      if ($success && $this->freebusy_trigger)
        $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
      
      return $success;
    }

    return false;
  }

  /**
   * Wrapper to update an event object depending on the given savemode
   */
  private function update_event($event)
  {
    if (!($storage = $this->get_calendar($event['calendar'])))
      return false;

    // move event to another folder/calendar
    if ($event['_fromcalendar'] && $event['_fromcalendar'] != $event['calendar']) {
      if (!($fromcalendar = $this->get_calendar($event['_fromcalendar'])))
        return false;

      $old = $fromcalendar->get_event($event['id']);

      if ($event['_savemode'] != 'new') {
        if (!$fromcalendar->storage->move($old['uid'], $storage->storage)) {
          return false;
        }

        $fromcalendar = $storage;
      }
    }
    else
      $fromcalendar = $storage;

    $success = false;
    $savemode = 'all';
    $attachments = array();
    $old = $master = $storage->get_event($event['id']);

    if (!$old || !$old['start']) {
      rcube::raise_error(array(
        'code' => 600, 'type' => 'php',
        'file' => __FILE__, 'line' => __LINE__,
        'message' => "Failed to load event object to update: id=" . $event['id']),
        true, false);
      return false;
    }

    // modify a recurring event, check submitted savemode to do the right things
    if ($old['recurrence'] || $old['recurrence_id'] || $old['isexception']) {
      $master = $storage->get_event($old['uid']);
      $savemode = $event['_savemode'] ?: ($old['recurrence_id'] || $old['isexception'] ? 'current' : 'all');

      // this-and-future on the first instance equals to 'all'
      if ($savemode == 'future' && $master['start'] && $old['_instance'] == libcalendaring::recurrence_instance_identifier($master))
        $savemode = 'all';
      // force 'current' mode for single occurrences stored as exception
      else if (!$old['recurrence'] && !$old['recurrence_id'] && $old['isexception'])
        $savemode = 'current';
    }

    // check if update affects scheduling and update attendee status accordingly
    $reschedule = $this->check_scheduling($event, $old, true);

    // keep saved exceptions (not submitted by the client)
    if ($old['recurrence']['EXDATE'] && !isset($event['recurrence']['EXDATE']))
      $event['recurrence']['EXDATE'] = $old['recurrence']['EXDATE'];
    if (isset($event['recurrence']['EXCEPTIONS']))
      $with_exceptions = true;  // exceptions already provided (e.g. from iCal import)
    else if ($old['recurrence']['EXCEPTIONS'])
      $event['recurrence']['EXCEPTIONS'] = $old['recurrence']['EXCEPTIONS'];
    else if ($old['exceptions'])
      $event['exceptions'] = $old['exceptions'];

    // remove some internal properties which should not be saved
    unset($event['_savemode'], $event['_fromcalendar'], $event['_identity'], $event['_owner'],
        $event['_notify'], $event['_method'], $event['_sender'], $event['_sender_utf'], $event['_size']);

    switch ($savemode) {
      case 'new':
        // save submitted data as new (non-recurring) event
        $event['recurrence'] = array();
        $event['_copyfrom'] = $master['_msguid'];
        $event['_mailbox'] = $master['_mailbox'];
        $event['uid'] = $this->cal->generate_uid();
        unset($event['recurrence_id'], $event['recurrence_date'], $event['_instance'], $event['id']);

        // copy attachment metadata to new event
        $event = self::from_rcube_event($event, $master);

        self::clear_attandee_noreply($event);
        if ($success = $storage->insert_event($event))
          $success = $event['uid'];
        break;

      case 'future':
        // create a new recurring event
        $event['_copyfrom'] = $master['_msguid'];
        $event['_mailbox'] = $master['_mailbox'];
        $event['uid'] = $this->cal->generate_uid();
        unset($event['recurrence_id'], $event['recurrence_date'], $event['_instance'], $event['id']);

        // copy attachment metadata to new event
        $event = self::from_rcube_event($event, $master);

        // remove recurrence exceptions on re-scheduling
        if ($reschedule) {
          unset($event['recurrence']['EXCEPTIONS'], $event['exceptions'], $master['recurrence']['EXDATE']);
        }
        else if (is_array($event['recurrence']['EXCEPTIONS'])) {
          // only keep relevant exceptions
          $event['recurrence']['EXCEPTIONS'] = array_filter($event['recurrence']['EXCEPTIONS'], function($exception) use ($event) {
            return $exception['start'] > $event['start'];
          });
          if (is_array($event['recurrence']['EXDATE'])) {
            $event['recurrence']['EXDATE'] = array_filter($event['recurrence']['EXDATE'], function($exdate) use ($event) {
              return $exdate > $event['start'];
            });
          }
          // set link to top-level exceptions
          $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
        }

        // compute remaining occurrences
        if ($event['recurrence']['COUNT']) {
          if (!$old['_count'])
            $old['_count'] = $this->get_recurrence_count($master, $old['start']);
          $event['recurrence']['COUNT'] -= intval($old['_count']);
        }

        // remove fixed weekday when date changed
        if ($old['start']->format('Y-m-d') != $event['start']->format('Y-m-d')) {
          if (strlen($event['recurrence']['BYDAY']) == 2)
            unset($event['recurrence']['BYDAY']);
          if ($old['recurrence']['BYMONTH'] == $old['start']->format('n'))
            unset($event['recurrence']['BYMONTH']);
        }

        // set until-date on master event
        $master['recurrence']['UNTIL'] = clone $old['start'];
        $master['recurrence']['UNTIL']->sub(new DateInterval('P1D'));
        unset($master['recurrence']['COUNT']);

        // remove all exceptions after $event['start']
        if (is_array($master['recurrence']['EXCEPTIONS'])) {
          $master['recurrence']['EXCEPTIONS'] = array_filter($master['recurrence']['EXCEPTIONS'], function($exception) use ($event) {
            return $exception['start'] < $event['start'];
          });
          // set link to top-level exceptions
          $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];
        }
        if (is_array($master['recurrence']['EXDATE'])) {
          $master['recurrence']['EXDATE'] = array_filter($master['recurrence']['EXDATE'], function($exdate) use ($event) {
            return $exdate < $event['start'];
          });
        }

        // save new event
        if ($success = $storage->insert_event($event)) {
          $success = $event['uid'];

          // update master event (no rescheduling!)
          self::clear_attandee_noreply($master);
          $storage->update_event($master);
        }
        break;

      case 'current':
        // recurring instances shall not store recurrence rules and attachments
        $event['recurrence'] = array();
        $event['thisandfuture'] = $savemode == 'future';
        unset($event['attachments'], $event['id']);

        // increment sequence of this instance if scheduling is affected
        if ($reschedule) {
          $event['sequence'] = max($old['sequence'], $master['sequence']) + 1;
        }
        else if (!isset($event['sequence'])) {
          $event['sequence'] = $old['sequence'] ?: $master['sequence'];
        }

        // save properties to a recurrence exception instance
        if ($old['_instance'] && is_array($master['recurrence']['EXCEPTIONS'])) {
          if ($this->update_recurrence_exceptions($master, $event, $old, $savemode)) {
            $success = $storage->update_event($master, $old['id']);
            break;
          }
        }

        $add_exception = true;

        // adjust matching RDATE entry if dates changed
        if (is_array($master['recurrence']['RDATE']) && ($old_date = $old['start']->format('Ymd')) != $event['start']->format('Ymd')) {
          foreach ($master['recurrence']['RDATE'] as $j => $rdate) {
            if ($rdate->format('Ymd') == $old_date) {
              $master['recurrence']['RDATE'][$j] = $event['start'];
              sort($master['recurrence']['RDATE']);
              $add_exception = false;
              break;
            }
          }
        }

        // save as new exception to master event
        if ($add_exception) {
          self::add_exception($master, $event, $old);
        }

        $success = $storage->update_event($master);
        break;

      default:  // 'all' is default
        $event['id'] = $master['uid'];
        $event['uid'] = $master['uid'];

        // use start date from master but try to be smart on time or duration changes
        $old_start_date = $old['start']->format('Y-m-d');
        $old_start_time = $old['allday'] ? '' : $old['start']->format('H:i');
        $old_duration = $old['end']->format('U') - $old['start']->format('U');
        
        $new_start_date = $event['start']->format('Y-m-d');
        $new_start_time = $event['allday'] ? '' : $event['start']->format('H:i');
        $new_duration = $event['end']->format('U') - $event['start']->format('U');
        
        $diff = $old_start_date != $new_start_date || $old_start_time != $new_start_time || $old_duration != $new_duration;
        $date_shift = $old['start']->diff($event['start']);
        
        // shifted or resized
        if ($diff && ($old_start_date == $new_start_date || $old_duration == $new_duration)) {
          $event['start'] = $master['start']->add($date_shift);
          $event['end'] = clone $event['start'];
          $event['end']->add(new DateInterval('PT'.$new_duration.'S'));
          
          // remove fixed weekday, will be re-set to the new weekday in kolab_calendar::update_event()
          if ($old_start_date != $new_start_date) {
            if (strlen($event['recurrence']['BYDAY']) == 2)
              unset($event['recurrence']['BYDAY']);
            if ($old['recurrence']['BYMONTH'] == $old['start']->format('n'))
              unset($event['recurrence']['BYMONTH']);
          }
        }
        // dates did not change, use the ones from master
        else if ($new_start_date . $new_start_time == $old_start_date . $old_start_time) {
          $event['start'] = $master['start'];
          $event['end'] = $master['end'];
        }

        // when saving an instance in 'all' mode, copy recurrence exceptions over
        if ($old['recurrence_id']) {
          $event['recurrence']['EXCEPTIONS'] = $master['recurrence']['EXCEPTIONS'];
        }
        else if ($master['_instance']) {
          $event['_instance'] = $master['_instance'];
          $event['recurrence_date'] = $master['recurrence_date'];
        }

        // TODO: forward changes to exceptions (which do not yet have differing values stored)
        if (is_array($event['recurrence']) && is_array($event['recurrence']['EXCEPTIONS']) && !$with_exceptions) {
          // determine added and removed attendees
          $old_attendees = $current_attendees = $added_attendees = array();
          foreach ((array)$old['attendees'] as $attendee) {
            $old_attendees[] = $attendee['email'];
          }
          foreach ((array)$event['attendees'] as $attendee) {
            $current_attendees[] = $attendee['email'];
            if (!in_array($attendee['email'], $old_attendees)) {
              $added_attendees[] = $attendee;
            }
          }
          $removed_attendees = array_diff($old_attendees, $current_attendees);

          foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
            calendar::merge_attendee_data($event['recurrence']['EXCEPTIONS'][$i], $added_attendees, $removed_attendees);
          }

          // adjust recurrence-id when start changed and therefore the entire recurrence chain changes
          if ($old_start_date != $new_start_date || $old_start_time != $new_start_time) {
            $recurrence_id_format = libcalendaring::recurrence_id_format($event);
            foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
              $recurrence_id = is_a($exception['recurrence_date'], 'DateTime') ? $exception['recurrence_date'] :
                  rcube_utils::anytodatetime($exception['_instance'], $old['start']->getTimezone());
              if (is_a($recurrence_id, 'DateTime')) {
                $recurrence_id->add($date_shift);
                $event['recurrence']['EXCEPTIONS'][$i]['recurrence_date'] = $recurrence_id;
                $event['recurrence']['EXCEPTIONS'][$i]['_instance'] = $recurrence_id->format($recurrence_id_format);
              }
            }
          }

          // set link to top-level exceptions
          $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
        }

        // unset _dateonly flags in (cached) date objects
        unset($event['start']->_dateonly, $event['end']->_dateonly);

        $success = $storage->update_event($event) ? $event['id'] : false;  // return master UID
        break;
    }

    if ($success && $this->freebusy_trigger)
      $this->rc->output->command('plugin.ping_url', array('action' => 'calendar/push-freebusy', 'source' => $storage->id));
    
    return $success;
  }

  /**
   * Determine whether the current change affects scheduling and reset attendee status accordingly
   */
  public function check_scheduling(&$event, $old, $update = true)
  {
    // skip this check when importing iCal/iTip events
    if (isset($event['sequence']) || !empty($event['_method'])) {
      return false;
    }

    // iterate through the list of properties considered 'significant' for scheduling
    $kolab_event = $old['_formatobj'] ?: new kolab_format_event();
    $reschedule = $kolab_event->check_rescheduling($event, $old);

    // reset all attendee status to needs-action (#4360)
    if ($update && $reschedule && is_array($event['attendees'])) {
      $is_organizer = false;
      $emails = $this->cal->get_user_emails();
      $attendees = $event['attendees'];
      foreach ($attendees as $i => $attendee) {
        if ($attendee['role'] == 'ORGANIZER' && $attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
          $is_organizer = true;
        }
        else if ($attendee['role'] != 'ORGANIZER' && $attendee['role'] != 'NON-PARTICIPANT' && $attendee['status'] != 'DELEGATED') {
          $attendees[$i]['status'] = 'NEEDS-ACTION';
          $attendees[$i]['rsvp'] = true;
        }
      }

      // update attendees only if I'm the organizer
      if ($is_organizer || ($event['organizer'] && in_array(strtolower($event['organizer']['email']), $emails))) {
        $event['attendees'] = $attendees;
      }
    }

    return $reschedule;
  }

  /**
   * Apply the given changes to already existing exceptions
   */
  protected function update_recurrence_exceptions(&$master, $event, $old, $savemode)
  {
    $saved = false;
    $existing = null;

    // determine added and removed attendees
    $added_attendees = $removed_attendees = array();
    if ($savemode == 'future') {
      $old_attendees = $current_attendees = array();
      foreach ((array)$old['attendees'] as $attendee) {
        $old_attendees[] = $attendee['email'];
      }
      foreach ((array)$event['attendees'] as $attendee) {
        $current_attendees[] = $attendee['email'];
        if (!in_array($attendee['email'], $old_attendees)) {
          $added_attendees[] = $attendee;
        }
      }
      $removed_attendees = array_diff($old_attendees, $current_attendees);
    }

    foreach ($master['recurrence']['EXCEPTIONS'] as $i => $exception) {
      // update a specific instance
      if ($exception['_instance'] == $old['_instance']) {
        $existing = $i;

        // check savemode against existing exception mode.
        // if matches, we can update this existing exception
        if ((bool)$exception['thisandfuture'] === ($savemode == 'future')) {
          $event['_instance'] = $old['_instance'];
          $event['thisandfuture'] = $old['thisandfuture'];
          $event['recurrence_date'] = $old['recurrence_date'];
          $master['recurrence']['EXCEPTIONS'][$i] = $event;
          $saved = true;
        }
      }
      // merge the new event properties onto future exceptions
      if ($savemode == 'future' && $exception['_instance'] >= $old['_instance']) {
        unset($event['thisandfuture']);
        self::merge_exception_data($master['recurrence']['EXCEPTIONS'][$i], $event, array('attendees'));

        if (!empty($added_attendees) || !empty($removed_attendees)) {
          calendar::merge_attendee_data($master['recurrence']['EXCEPTIONS'][$i], $added_attendees, $removed_attendees);
        }
      }
    }
/*
    // we could not update the existing exception due to savemode mismatch...
    if (!$saved && $existing !== null && $master['recurrence']['EXCEPTIONS'][$existing]['thisandfuture']) {
      // ... try to move the existing this-and-future exception to the next occurrence
      foreach ($this->get_recurring_events($master, $existing['start']) as $candidate) {
        // our old this-and-future exception is obsolete
        if ($candidate['thisandfuture']) {
          unset($master['recurrence']['EXCEPTIONS'][$existing]);
          $saved = true;
          break;
        }
        // this occurrence doesn't yet have an exception
        else if (!$candidate['isexception']) {
          $event['_instance'] = $candidate['_instance'];
          $event['recurrence_date'] = $candidate['recurrence_date'];
          $master['recurrence']['EXCEPTIONS'][$i] = $event;
          $saved = true;
          break;
        }
      }
    }
*/

    // set link to top-level exceptions
    $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];

    // returning false here will add a new exception
    return $saved;
  }

  /**
   * Add or update the given event as an exception to $master
   */
  public static function add_exception(&$master, $event, $old = null)
  {
    if ($old) {
      $event['_instance'] = $old['_instance'];
      if (!$event['recurrence_date'])
        $event['recurrence_date'] = $old['recurrence_date'] ?: $old['start'];
    }
    else if (!$event['recurrence_date']) {
      $event['recurrence_date'] = $event['start'];
    }

    if (!$event['_instance'] && is_a($event['recurrence_date'], 'DateTime')) {
      $event['_instance'] = libcalendaring::recurrence_instance_identifier($event);
    }

    if (!is_array($master['exceptions']) && is_array($master['recurrence']['EXCEPTIONS'])) {
      $master['exceptions'] = &$master['recurrence']['EXCEPTIONS'];
    }

    $existing = false;
    foreach ((array)$master['exceptions'] as $i => $exception) {
      if ($exception['_instance'] == $event['_instance']) {
        $master['exceptions'][$i] = $event;
        $existing = true;
      }
    }

    if (!$existing) {
      $master['exceptions'][] = $event;
    }

    return true;
  }

  /**
   * Remove the noreply flags from attendees
   */
  public static function clear_attandee_noreply(&$event)
  {
    foreach ((array)$event['attendees'] as $i => $attendee) {
      unset($event['attendees'][$i]['noreply']);
    }
  }


  /**
   * Merge certain properties from the overlay event to the base event object
   *
   * @param array The event object to be altered
   * @param array The overlay event object to be merged over $event
   * @param array List of properties not allowed to be overwritten
   */
  public static function merge_exception_data(&$event, $overlay, $blacklist = null)
  {
    $forbidden = array('id','uid','recurrence','recurrence_date','thisandfuture','organizer','_attachments');

    if (is_array($blacklist))
      $forbidden = array_merge($forbidden, $blacklist);

    // compute date offset from the exception
    if ($overlay['start'] instanceof DateTime && $overlay['recurrence_date'] instanceof DateTime) {
      $date_offset = $overlay['recurrence_date']->diff($overlay['start']);
    }

    foreach ($overlay as $prop => $value) {
      if ($prop == 'start' || $prop == 'end') {
        if (is_object($event[$prop]) && $event[$prop] instanceof DateTime) {
          // set date value if overlay is an exception of the current instance
          if (substr($overlay['_instance'], 0, 8) == substr($event['_instance'], 0, 8)) {
            $event[$prop]->setDate(intval($value->format('Y')), intval($value->format('n')), intval($value->format('j')));
          }
          // apply date offset
          else if ($date_offset) {
            $event[$prop]->add($date_offset);
          }
          // adjust time of the recurring event instance
          $event[$prop]->setTime($value->format('G'), intval($value->format('i')), intval($value->format('s')));
        }
      }
      else if ($prop == 'thisandfuture' && $overlay['_instance'] == $event['_instance']) {
        $event[$prop] = $value;
      }
      else if ($prop[0] != '_' && !in_array($prop, $forbidden))
        $event[$prop] = $value;
    }
  }

  /**
   * Get events from source.
   *
   * @param  integer Event's new start (unix timestamp)
   * @param  integer Event's new end (unix timestamp)
   * @param  string  Search query (optional)
   * @param  mixed   List of calendar IDs to load events from (either as array or comma-separated string)
   * @param  boolean Include virtual events (optional)
   * @param  integer Only list events modified since this time (unix timestamp)
   * @return array A list of event records
   */
  public function load_events($start, $end, $search = null, $calendars = null, $virtual = 1, $modifiedsince = null)
  {
    if ($calendars && is_string($calendars))
      $calendars = explode(',', $calendars);
    else if (!$calendars) {
      $this->_read_calendars();
      $calendars = array_keys($this->calendars);
    }

    $query = array();
    if ($modifiedsince)
      $query[] = array('changed', '>=', $modifiedsince);

    $events = $categories = array();
    foreach ($calendars as $cid) {
      if ($storage = $this->get_calendar($cid)) {
        $events = array_merge($events, $storage->list_events($start, $end, $search, $virtual, $query));
        $categories += $storage->categories;
      }
    }

    // add events from the address books birthday calendar
    if (in_array(self::BIRTHDAY_CALENDAR_ID, $calendars)) {
      $events = array_merge($events, $this->load_birthday_events($start, $end, $search, $modifiedsince));
    }

    // add new categories to user prefs
    $old_categories = $this->rc->config->get('calendar_categories', $this->default_categories);
    if ($newcats = array_udiff(array_keys($categories), array_keys($old_categories), function($a, $b){ return strcasecmp($a, $b); })) {
      foreach ($newcats as $category)
        $old_categories[$category] = '';  // no color set yet
      $this->rc->user->save_prefs(array('calendar_categories' => $old_categories));
    }

    array_walk($events, 'kolab_driver::to_rcube_event');
    return $events;
  }

  /**
   * Get number of events in the given calendar
   *
   * @param  mixed   List of calendar IDs to count events (either as array or comma-separated string)
   * @param  integer Date range start (unix timestamp)
   * @param  integer Date range end (unix timestamp)
   * @return array   Hash array with counts grouped by calendar ID
   */
  public function count_events($calendars, $start, $end = null)
  {
      $counts = array();

      if ($calendars && is_string($calendars))
        $calendars = explode(',', $calendars);
      else if (!$calendars) {
        $this->_read_calendars();
        $calendars = array_keys($this->calendars);
      }

      foreach ($calendars as $cid) {
        if ($storage = $this->get_calendar($cid)) {
            $counts[$cid] = $storage->count_events($start, $end);
        }
      }

      return $counts;
  }

  /**
   * Get a list of pending alarms to be displayed to the user
   *
   * @see calendar_driver::pending_alarms()
   */
  public function pending_alarms($time, $calendars = null)
  {
    $interval = 300;
    $time -= $time % 60;
    
    $slot = $time;
    $slot -= $slot % $interval;
    
    $last = $time - max(60, $this->rc->config->get('refresh_interval', 0));
    $last -= $last % $interval;
    
    // only check for alerts once in 5 minutes
    if ($last == $slot)
      return array();
    
    if ($calendars && is_string($calendars))
      $calendars = explode(',', $calendars);
    
    $time = $slot + $interval;
    
    $candidates = array();
    $query = array(array('tags', '=', 'x-has-alarms'));

    $this->_read_calendars();

    foreach ($this->calendars as $cid => $calendar) {
      // skip calendars with alarms disabled
      if (!$calendar->alarms || ($calendars && !in_array($cid, $calendars)))
        continue;

      foreach ($calendar->list_events($time, $time + 86400 * 365, null, 1, $query) as $e) {
        // add to list if alarm is set
        $alarm = libcalendaring::get_next_alarm($e);
        if ($alarm && $alarm['time'] && $alarm['time'] >= $last && in_array($alarm['action'], $this->alarm_types)) {
          $id = $alarm['id'];  // use alarm-id as primary identifier
          $candidates[$id] = array(
            'id'       => $id,
            'title'    => $e['title'],
            'location' => $e['location'],
            'start'    => $e['start'],
            'end'      => $e['end'],
            'notifyat' => $alarm['time'],
            'action'   => $alarm['action'],
          );
        }
      }
    }

    // get alarm information stored in local database
    if (!empty($candidates)) {
      $alarm_ids = array_map(array($this->rc->db, 'quote'), array_keys($candidates));
      $result = $this->rc->db->query("SELECT *"
        . " FROM " . $this->rc->db->table_name('kolab_alarms', true)
        . " WHERE `alarm_id` IN (" . join(',', $alarm_ids) . ")"
          . " AND `user_id` = ?",
        $this->rc->user->ID
      );

      while ($result && ($e = $this->rc->db->fetch_assoc($result))) {
        $dbdata[$e['alarm_id']] = $e;
      }
    }
    
    $alarms = array();
    foreach ($candidates as $id => $alarm) {
      // skip dismissed alarms
      if ($dbdata[$id]['dismissed'])
        continue;
      
      // snooze function may have shifted alarm time
      $notifyat = $dbdata[$id]['notifyat'] ? strtotime($dbdata[$id]['notifyat']) : $alarm['notifyat'];
      if ($notifyat <= $time)
        $alarms[] = $alarm;
    }
    
    return $alarms;
  }

  /**
   * Feedback after showing/sending an alarm notification
   *
   * @see calendar_driver::dismiss_alarm()
   */
  public function dismiss_alarm($alarm_id, $snooze = 0)
  {
    $alarms_table = $this->rc->db->table_name('kolab_alarms', true);
    // delete old alarm entry
    $this->rc->db->query("DELETE FROM $alarms_table"
      . " WHERE `alarm_id` = ? AND `user_id` = ?",
      $alarm_id,
      $this->rc->user->ID
    );

    // set new notifyat time or unset if not snoozed
    $notifyat = $snooze > 0 ? date('Y-m-d H:i:s', time() + $snooze) : null;

    $query = $this->rc->db->query("INSERT INTO $alarms_table"
      . " (`alarm_id`, `user_id`, `dismissed`, `notifyat`)"
      . " VALUES (?, ?, ?, ?)",
      $alarm_id,
      $this->rc->user->ID,
      $snooze > 0 ? 0 : 1,
      $notifyat
    );

    return $this->rc->db->affected_rows($query);
  }

  /**
   * List attachments from the given event
   */
  public function list_attachments($event)
  {
    if (!($storage = $this->get_calendar($event['calendar'])))
      return false;

    $event = $storage->get_event($event['id']);

    return $event['attachments'];
  }

  /**
   * Get attachment properties
   */
  public function get_attachment($id, $event)
  {
    if (!($storage = $this->get_calendar($event['calendar'])))
      return false;

    // get old revision of event
    if ($event['rev']) {
      $event = $this->get_event_revison($event, $event['rev'], true);
    }
    else {
      $event = $storage->get_event($event['id']);
    }

    if ($event && !empty($event['_attachments'])) {
      foreach ($event['_attachments'] as $att) {
        if ($att['id'] == $id) {
          return $att;
        }
      }
    }

    return null;
  }

  /**
   * Get attachment body
   * @see calendar_driver::get_attachment_body()
   */
  public function get_attachment_body($id, $event)
  {
    if (!($cal = $this->get_calendar($event['calendar'])))
      return false;

    // get old revision of event
    if ($event['rev']) {
      if (empty($this->bonnie_api)) {
        return false;
      }

      $cid = substr($id, 4);

      // call Bonnie API and get the raw mime message
      list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
      if ($msg_raw = $this->bonnie_api->rawdata('event', $uid, $event['rev'], $mailbox, $msguid)) {
        // parse the message and find the part with the matching content-id
        $message = rcube_mime::parse_message($msg_raw);
        foreach ((array)$message->parts as $part) {
          if ($part->headers['content-id'] && trim($part->headers['content-id'], '<>') == $cid) {
            return $part->body;
          }
        }
      }

      return false;
    }

    return $cal->get_attachment_body($id, $event);
  }

  /**
   * Build a struct representing the given message reference
   *
   * @see calendar_driver::get_message_reference()
   */
  public function get_message_reference($uri_or_headers, $folder = null)
  {
      if (is_object($uri_or_headers)) {
          $uri_or_headers = kolab_storage_config::get_message_uri($uri_or_headers, $folder);
      }

      if (is_string($uri_or_headers)) {
          return kolab_storage_config::get_message_reference($uri_or_headers, 'event');
      }

      return false;
  }

  /**
   * List availabale categories
   * The default implementation reads them from config/user prefs
   */
  public function list_categories()
  {
    // FIXME: complete list with categories saved in config objects (KEP:12)
    return $this->rc->config->get('calendar_categories', $this->default_categories);
  }

  /**
   * Create instances of a recurring event
   *
   * @param array  Hash array with event properties
   * @param object DateTime Start date of the recurrence window
   * @param object DateTime End date of the recurrence window
   * @return array List of recurring event instances
   */
  public function get_recurring_events($event, $start, $end = null)
  {
    // load the given event data into a libkolabxml container
    if (!$event['_formatobj']) {
      $event_xml = new kolab_format_event();
      $event_xml->set($event);
      $event['_formatobj'] = $event_xml;
    }

    $this->_read_calendars();
    $storage = reset($this->calendars);
    return $storage->get_recurring_events($event, $start, $end);
  }

  /**
   *
   */
  private function get_recurrence_count($event, $dtstart)
  {
    // use libkolab to compute recurring events
    if (class_exists('kolabcalendaring') && $event['_formatobj']) {
        $recurrence = new kolab_date_recurrence($event['_formatobj']);
    }
    else {
      // fallback to local recurrence implementation
      require_once($this->cal->home . '/lib/calendar_recurrence.php');
      $recurrence = new calendar_recurrence($this->cal, $event);
    }

    $count = 0;
    while (($next_event = $recurrence->next_instance()) && $next_event['start'] <= $dtstart && $count < 1000) {
      $count++;
    }

    return $count;
  }

  /**
   * Fetch free/busy information from a person within the given range
   */
  public function get_freebusy_list($email, $start, $end)
  {
    if (empty($email)/* || $end < time()*/)
      return false;

    // map vcalendar fbtypes to internal values
    $fbtypemap = array(
      'FREE' => calendar::FREEBUSY_FREE,
      'BUSY-TENTATIVE' => calendar::FREEBUSY_TENTATIVE,
      'X-OUT-OF-OFFICE' => calendar::FREEBUSY_OOF,
      'OOF' => calendar::FREEBUSY_OOF);

    // ask kolab server first
    try {
      $request_config = array(
        'store_body'       => true,
        'follow_redirects' => true,
      );
      $request  = libkolab::http_request(kolab_storage::get_freebusy_url($email), 'GET', $request_config);
      $response = $request->send();

      // authentication required
      if ($response->getStatus() == 401) {
        $request->setAuth($this->rc->user->get_username(), $this->rc->decrypt($_SESSION['password']));
        $response = $request->send();
      }

      if ($response->getStatus() == 200)
        $fbdata = $response->getBody();

      unset($request, $response);
    }
    catch (Exception $e) {
      PEAR::raiseError("Error fetching free/busy information: " . $e->getMessage());
    }

    // get free-busy url from contacts
    if (!$fbdata) {
      $fburl = null;
      foreach ((array)$this->rc->config->get('autocomplete_addressbooks', 'sql') as $book) {
        $abook = $this->rc->get_address_book($book);

        if ($result = $abook->search(array('email'), $email, true, true, true/*, 'freebusyurl'*/)) {
          while ($contact = $result->iterate()) {
            if ($fburl = $contact['freebusyurl']) {
              $fbdata = @file_get_contents($fburl);
              break;
            }
          }
        }

        if ($fbdata)
          break;
      }
    }

    // parse free-busy information using Horde classes
    if ($fbdata) {
      $ical = $this->cal->get_ical();
      $ical->import($fbdata);
      if ($fb = $ical->freebusy) {
        $result = array();
        foreach ($fb['periods'] as $tuple) {
          list($from, $to, $type) = $tuple;
          $result[] = array($from->format('U'), $to->format('U'), isset($fbtypemap[$type]) ? $fbtypemap[$type] : calendar::FREEBUSY_BUSY);
        }

        // we take 'dummy' free-busy lists as "unknown"
        if (empty($result) && !empty($fb['comment']) && stripos($fb['comment'], 'dummy'))
          return false;

        // set period from $start till the begin of the free-busy information as 'unknown'
        if ($fb['start'] && ($fbstart = $fb['start']->format('U')) && $start < $fbstart) {
          array_unshift($result, array($start, $fbstart, calendar::FREEBUSY_UNKNOWN));
        }
        // pad period till $end with status 'unknown'
        if ($fb['end'] && ($fbend = $fb['end']->format('U')) && $fbend < $end) {
          $result[] = array($fbend, $end, calendar::FREEBUSY_UNKNOWN);
        }

        return $result;
      }
    }

    return false;
  }

  /**
   * Handler to push folder triggers when sent from client.
   * Used to push free-busy changes asynchronously after updating an event
   */
  public function push_freebusy()
  {
    // make shure triggering completes
    set_time_limit(0);
    ignore_user_abort(true);

    $cal = rcube_utils::get_input_value('source', rcube_utils::INPUT_GPC);
    if (!($cal = $this->get_calendar($cal)))
      return false;

    // trigger updates on folder
    $trigger = $cal->storage->trigger();
    if (is_object($trigger) && is_a($trigger, 'PEAR_Error')) {
      rcube::raise_error(array(
        'code' => 900, 'type' => 'php',
        'file' => __FILE__, 'line' => __LINE__,
        'message' => "Failed triggering folder. Error was " . $trigger->getMessage()),
        true, false);
    }

    exit;
  }


  /**
   * Convert from driver format to external caledar app data
   */
  public static function to_rcube_event(&$record)
  {
    if (!is_array($record))
      return $record;

    $record['id'] = $record['uid'];

    if ($record['_instance']) {
      $record['id'] .= '-' . $record['_instance'];

      if (!$record['recurrence_id'] && !empty($record['recurrence']))
        $record['recurrence_id'] = $record['uid'];
    }

    // all-day events go from 12:00 - 13:00
    if (is_a($record['start'], 'DateTime') && $record['end'] <= $record['start'] && $record['allday']) {
      $record['end'] = clone $record['start'];
      $record['end']->add(new DateInterval('PT1H'));
    }

    // translate internal '_attachments' to external 'attachments' list
    if (!empty($record['_attachments'])) {
      foreach ($record['_attachments'] as $key => $attachment) {
        if ($attachment !== false) {
          if (!$attachment['name'])
            $attachment['name'] = $key;

          unset($attachment['path'], $attachment['content']);
          $attachments[] = $attachment;
        }
      }

      $record['attachments'] = $attachments;
    }

    if (!empty($record['attendees'])) {
      foreach ((array)$record['attendees'] as $i => $attendee) {
        if (is_array($attendee['delegated-from'])) {
          $record['attendees'][$i]['delegated-from'] = join(', ', $attendee['delegated-from']);
        }
        if (is_array($attendee['delegated-to'])) {
          $record['attendees'][$i]['delegated-to'] = join(', ', $attendee['delegated-to']);
        }
      }
    }

    // Roundcube only supports one category assignment
    if (is_array($record['categories']))
      $record['categories'] = $record['categories'][0];

    // the cancelled flag transltes into status=CANCELLED
    if ($record['cancelled'])
      $record['status'] = 'CANCELLED';

    // The web client only supports DISPLAY type of alarms
    if (!empty($record['alarms']))
      $record['alarms'] = preg_replace('/:[A-Z]+$/', ':DISPLAY', $record['alarms']);

    // remove empty recurrence array
    if (empty($record['recurrence']))
      unset($record['recurrence']);

    // clean up exception data
    if (is_array($record['recurrence']['EXCEPTIONS'])) {
      array_walk($record['recurrence']['EXCEPTIONS'], function(&$exception) {
        unset($exception['_mailbox'], $exception['_msguid'], $exception['_formatobj'], $exception['_attachments']);
      });
    }

    unset($record['_mailbox'], $record['_msguid'], $record['_type'], $record['_size'],
      $record['_formatobj'], $record['_attachments'], $record['exceptions'], $record['x-custom']);

    return $record;
  }

  /**
   *
   */
  public static function from_rcube_event($event, $old = array())
  {
    // in kolab_storage attachments are indexed by content-id
    if (is_array($event['attachments']) || !empty($event['deleted_attachments'])) {
      $event['_attachments'] = array();

      foreach ($event['attachments'] as $attachment) {
        $key = null;
        // Roundcube ID has nothing to do with the storage ID, remove it
        if ($attachment['content'] || $attachment['path']) {
          unset($attachment['id']);
        }
        else {
          foreach ((array)$old['_attachments'] as $cid => $oldatt) {
            if ($attachment['id'] == $oldatt['id'])
              $key = $cid;
          }
        }

        // flagged for deletion => set to false
        if ($attachment['_deleted'] || in_array($attachment['id'], (array)$event['deleted_attachments'])) {
          $event['_attachments'][$key] = false;
        }
        // replace existing entry
        else if ($key) {
          $event['_attachments'][$key] = $attachment;
        }
        // append as new attachment
        else {
          $event['_attachments'][] = $attachment;
        }
      }

      $event['_attachments'] = array_merge((array)$old['_attachments'], $event['_attachments']);

      // attachments flagged for deletion => set to false
      foreach ($event['_attachments'] as $key => $attachment) {
        if ($attachment['_deleted'] || in_array($attachment['id'], (array)$event['deleted_attachments'])) {
          $event['_attachments'][$key] = false;
        }
      }
    }

    return $event;
  }


  /**
   * Set CSS class according to the event's attendde partstat
   */
  public static function add_partstat_class($event, $partstats, $user = null)
  {
    // set classes according to PARTSTAT
    if (is_array($event['attendees'])) {
      $user_emails = libcalendaring::get_instance()->get_user_emails($user);
      $partstat = 'UNKNOWN';
      foreach ($event['attendees'] as $attendee) {
        if (in_array($attendee['email'], $user_emails)) {
          $partstat = $attendee['status'];
          break;
        }
      }

      if (in_array($partstat, $partstats)) {
        $event['className'] = trim($event['className'] . ' fc-invitation-' . strtolower($partstat));
      }
    }

    return $event;
  }

  /**
   * Provide a list of revisions for the given event
   *
   * @param array  $event Hash array with event properties
   *
   * @return array List of changes, each as a hash array
   * @see calendar_driver::get_event_changelog()
   */
  public function get_event_changelog($event)
  {
    if (empty($this->bonnie_api)) {
      return false;
    }

    list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);

    $result = $this->bonnie_api->changelog('event', $uid, $mailbox, $msguid);
    if (is_array($result) && $result['uid'] == $uid) {
      return $result['changes'];
    }

    return false;
  }

  /**
   * Get a list of property changes beteen two revisions of an event
   *
   * @param array  $event Hash array with event properties
   * @param mixed  $rev1  Old Revision
   * @param mixed  $rev2  New Revision
   *
   * @return array List of property changes, each as a hash array
   * @see calendar_driver::get_event_diff()
   */
  public function get_event_diff($event, $rev1, $rev2)
  {
    if (empty($this->bonnie_api)) {
      return false;
    }

    list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);

    // get diff for the requested recurrence instance
    $instance_id = $event['id'] != $uid ? substr($event['id'], strlen($uid) + 1) : null;

    // call Bonnie API
    $result = $this->bonnie_api->diff('event', $uid, $rev1, $rev2, $mailbox, $msguid, $instance_id);
    if (is_array($result) && $result['uid'] == $uid) {
      $result['rev1'] = $rev1;
      $result['rev2'] = $rev2;

      $keymap = array(
        'dtstart'  => 'start',
        'dtend'    => 'end',
        'dstamp'   => 'changed',
        'summary'  => 'title',
        'alarm'    => 'alarms',
        'attendee' => 'attendees',
        'attach'   => 'attachments',
        'rrule'    => 'recurrence',
        'transparency' => 'free_busy',
        'classification' => 'sensitivity',
        'lastmodified-date' => 'changed',
      );
      $prop_keymaps = array(
        'attachments' => array('fmttype' => 'mimetype', 'label' => 'name'),
        'attendees'   => array('partstat' => 'status'),
      );
      $special_changes = array();

      // map kolab event properties to keys the client expects
      array_walk($result['changes'], function(&$change, $i) use ($keymap, $prop_keymaps, $special_changes) {
        if (array_key_exists($change['property'], $keymap)) {
          $change['property'] = $keymap[$change['property']];
        }
        // translate free_busy values
        if ($change['property'] == 'free_busy') {
          $change['old'] = $old['old'] ? 'free' : 'busy';
          $change['new'] = $old['new'] ? 'free' : 'busy';
        }
        // map alarms trigger value
        if ($change['property'] == 'alarms') {
          if (is_array($change['old']) && is_array($change['old']['trigger']))
            $change['old']['trigger'] = $change['old']['trigger']['value'];
          if (is_array($change['new']) && is_array($change['new']['trigger']))
            $change['new']['trigger'] = $change['new']['trigger']['value'];
        }
        // make all property keys uppercase
        if ($change['property'] == 'recurrence') {
          $special_changes['recurrence'] = $i;
          foreach (array('old','new') as $m) {
            if (is_array($change[$m])) {
              $props = array();
              foreach ($change[$m] as $k => $v)
                $props[strtoupper($k)] = $v;
              $change[$m] = $props;
            }
          }
        }
        // map property keys names
        if (is_array($prop_keymaps[$change['property']])) {
          foreach ($prop_keymaps[$change['property']] as $k => $dest) {
            if (is_array($change['old']) && array_key_exists($k, $change['old'])) {
              $change['old'][$dest] = $change['old'][$k];
              unset($change['old'][$k]);
            }
            if (is_array($change['new']) && array_key_exists($k, $change['new'])) {
              $change['new'][$dest] = $change['new'][$k];
              unset($change['new'][$k]);
            }
          }
        }

        if ($change['property'] == 'exdate') {
          $special_changes['exdate'] = $i;
        }
        else if ($change['property'] == 'rdate') {
          $special_changes['rdate'] = $i;
        }
      });

      // merge some recurrence changes
      foreach (array('exdate','rdate') as $prop) {
        if (array_key_exists($prop, $special_changes)) {
          $exdate = $result['changes'][$special_changes[$prop]];
          if (array_key_exists('recurrence', $special_changes)) {
            $recurrence = &$result['changes'][$special_changes['recurrence']];
          }
          else {
            $i = count($result['changes']);
            $result['changes'][$i] = array('property' => 'recurrence', 'old' => array(), 'new' => array());
            $recurrence = &$result['changes'][$i]['recurrence'];
          }
          $key = strtoupper($prop);
          $recurrence['old'][$key] = $exdate['old'];
          $recurrence['new'][$key] = $exdate['new'];
          unset($result['changes'][$special_changes[$prop]]);
        }
      }

      return $result;
    }

    return false;
  }

  /**
   * Return full data of a specific revision of an event
   *
   * @param array  Hash array with event properties
   * @param mixed  $rev Revision number
   *
   * @return array Event object as hash array
   * @see calendar_driver::get_event_revison()
   */
  public function get_event_revison($event, $rev, $internal = false)
  {
    if (empty($this->bonnie_api)) {
      return false;
    }

    $eventid = $event['id'];
    $calid = $event['calendar'];
    list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);

    // call Bonnie API
    $result = $this->bonnie_api->get('event', $uid, $rev, $mailbox, $msguid);
    if (is_array($result) && $result['uid'] == $uid && !empty($result['xml'])) {
      $format = kolab_format::factory('event');
      $format->load($result['xml']);
      $event = $format->to_array();
      $format->get_attachments($event, true);

      // get the right instance from a recurring event
      if ($eventid != $event['uid']) {
        $instance_id = substr($eventid, strlen($event['uid']) + 1);

        // check for recurrence exception first
        if ($instance = $format->get_instance($instance_id)) {
          $event = $instance;
        }
        else {
          // not a exception, compute recurrence...
          $event['_formatobj'] = $format;
          $recurrence_date = rcube_utils::anytodatetime($instance_id, $event['start']->getTimezone());
          foreach ($this->get_recurring_events($event, $event['start'], $recurrence_date) as $instance) {
            if ($instance['id'] == $eventid) {
              $event = $instance;
              break;
            }
          }
        }
      }

      if ($format->is_valid()) {
        $event['calendar'] = $calid;
        $event['rev'] = $result['rev'];
        return $internal ? $event : self::to_rcube_event($event);
      }
    }

    return false;
  }

  /**
   * Command the backend to restore a certain revision of an event.
   * This shall replace the current event with an older version.
   *
   * @param mixed  UID string or hash array with event properties:
   *        id: Event identifier
   *  calendar: Calendar identifier
   * @param mixed  $rev Revision number
   *
   * @return boolean True on success, False on failure
   */
  public function restore_event_revision($event, $rev)
  {
    if (empty($this->bonnie_api)) {
      return false;
    }

    list($uid, $mailbox, $msguid) = $this->_resolve_event_identity($event);
    $calendar = $this->get_calendar($event['calendar']);
    $success = false;

    if ($calendar && $calendar->storage && $calendar->editable) {
      if ($raw_msg = $this->bonnie_api->rawdata('event', $uid, $rev, $mailbox)) {
        $imap = $this->rc->get_storage();

        // insert $raw_msg as new message
        if ($imap->save_message($calendar->storage->name, $raw_msg, null, false)) {
          $success = true;

          // delete old revision from imap and cache
          $imap->delete_message($msguid, $calendar->storage->name);
          $calendar->storage->cache->set($msguid, false);
        }
      }
    }

    return $success;
  }

  /**
   * Helper method to resolved the given event identifier into uid and folder
   *
   * @return array (uid,folder,msguid) tuple
   */
  private function _resolve_event_identity($event)
  {
    $mailbox = $msguid = null;
    if (is_array($event)) {
      $uid = $event['uid'] ?: $event['id'];
      if (($cal = $this->get_calendar($event['calendar'])) && !($cal instanceof kolab_invitation_calendar)) {
        $mailbox = $cal->get_mailbox_id();

        // get event object from storage in order to get the real object uid an msguid
        if ($ev = $cal->get_event($event['id'])) {
          $msguid = $ev['_msguid'];
          $uid = $ev['uid'];
        }
      }
    }
    else {
      $uid = $event;

      // get event object from storage in order to get the real object uid an msguid
      if ($ev = $this->get_event($event)) {
        $mailbox = $ev['_mailbox'];
        $msguid = $ev['_msguid'];
        $uid = $ev['uid'];
      }
    }

    return array($uid, $mailbox, $msguid);
  }

  /**
   * Callback function to produce driver-specific calendar create/edit form
   *
   * @param string Request action 'form-edit|form-new'
   * @param array  Calendar properties (e.g. id, color)
   * @param array  Edit form fields
   *
   * @return string HTML content of the form
   */
  public function calendar_form($action, $calendar, $formfields)
  {
    // show default dialog for birthday calendar
    if (in_array($calendar['id'], array(self::BIRTHDAY_CALENDAR_ID, self::INVITATIONS_CALENDAR_PENDING, self::INVITATIONS_CALENDAR_DECLINED))) {
      if ($calendar['id'] != self::BIRTHDAY_CALENDAR_ID)
        unset($formfields['showalarms']);
      return parent::calendar_form($action, $calendar, $formfields);
    }

    $this->_read_calendars();

    if ($calendar['id'] && ($cal = $this->calendars[$calendar['id']])) {
      $folder = $cal->get_realname(); // UTF7
      $color  = $cal->get_color();
    }
    else {
      $folder = '';
      $color  = '';
    }

    $hidden_fields[] = array('name' => 'oldname', 'value' => $folder);

    $storage = $this->rc->get_storage();
    $delim   = $storage->get_hierarchy_delimiter();
    $form   = array();

    if (strlen($folder)) {
      $path_imap = explode($delim, $folder);
      array_pop($path_imap);  // pop off name part
      $path_imap = implode($path_imap, $delim);

      $options = $storage->folder_info($folder);
    }
    else {
      $path_imap = '';
    }

    // General tab
    $form['props'] = array(
      'name' => $this->rc->gettext('properties'),
    );

    // Disable folder name input
    if (!empty($options) && ($options['norename'] || $options['protected'])) {
      $input_name = new html_hiddenfield(array('name' => 'name', 'id' => 'calendar-name'));
      $formfields['name']['value'] = kolab_storage::object_name($folder)
        . $input_name->show($folder);
    }

    // calendar name (default field)
    $form['props']['fieldsets']['location'] = array(
      'name'  => $this->rc->gettext('location'),
      'content' => array(
        'name' => $formfields['name']
      ),
    );

    if (!empty($options) && ($options['norename'] || $options['protected'])) {
      // prevent user from moving folder
      $hidden_fields[] = array('name' => 'parent', 'value' => $path_imap);
    }
    else {
      $select = kolab_storage::folder_selector('event', array('name' => 'parent', 'id' => 'calendar-parent'), $folder);
      $form['props']['fieldsets']['location']['content']['path'] = array(
        'id' => 'calendar-parent',
        'label' => $this->cal->gettext('parentcalendar'),
        'value' => $select->show(strlen($folder) ? $path_imap : ''),
      );
    }

    // calendar color (default field)
    $form['props']['fieldsets']['settings'] = array(
      'name'  => $this->rc->gettext('settings'),
      'content' => array(
        'color' => $formfields['color'],
        'showalarms' => $formfields['showalarms'],
      ),
    );
    
    
    if ($action != 'form-new') {
      $form['sharing'] = array(
          'name'    => rcube::Q($this->cal->gettext('tabsharing')),
          'content' => html::tag('iframe', array(
            'src' => $this->cal->rc->url(array('_action' => 'calendar-acl', 'id' => $calendar['id'], 'framed' => 1)),
            'width' => '100%',
            'height' => 350,
            'border' => 0,
            'style' => 'border:0'),
        ''),
      );
    }

    $this->form_html = '';
    if (is_array($hidden_fields)) {
        foreach ($hidden_fields as $field) {
            $hiddenfield = new html_hiddenfield($field);
            $this->form_html .= $hiddenfield->show() . "\n";
        }
    }

    // Create form output
    foreach ($form as $tab) {
      if (!empty($tab['fieldsets']) && is_array($tab['fieldsets'])) {
        $content = '';
        foreach ($tab['fieldsets'] as $fieldset) {
          $subcontent = $this->get_form_part($fieldset);
          if ($subcontent) {
            $content .= html::tag('fieldset', null, html::tag('legend', null, rcube::Q($fieldset['name'])) . $subcontent) ."\n";
          }
        }
      }
      else {
        $content = $this->get_form_part($tab);
      }

      if ($content) {
        $this->form_html .= html::tag('fieldset', null, html::tag('legend', null, rcube::Q($tab['name'])) . $content) ."\n";
      }
    }

    // Parse form template for skin-dependent stuff
    $this->rc->output->add_handler('calendarform', array($this, 'calendar_form_html'));
    return $this->rc->output->parse('calendar.kolabform', false, false);
  }

  /**
   * Handler for template object
   */
  public function calendar_form_html()
  {
    return $this->form_html;
  }

  /**
   * Helper function used in calendar_form_content(). Creates a part of the form.
   */
  private function get_form_part($form)
  {
    $content = '';

    if (is_array($form['content']) && !empty($form['content'])) {
      $table = new html_table(array('cols' => 2));
      foreach ($form['content'] as $col => $colprop) {
        $label = !empty($colprop['label']) ? $colprop['label'] : $this->cal->gettext($col);

        $table->add('title', html::label($colprop['id'], rcube::Q($label)));
        $table->add(null, $colprop['value']);
      }
      $content = $table->show();
    }
    else {
      $content = $form['content'];
    }

    return $content;
  }


  /**
   * Handler to render ACL form for a calendar folder
   */
  public function calendar_acl()
  {
    $this->rc->output->add_handler('folderacl', array($this, 'calendar_acl_form'));
    $this->rc->output->send('calendar.kolabacl');
  }

  /**
   * Handler for ACL form template object
   */
  public function calendar_acl_form()
  {
    $calid = rcube_utils::get_input_value('_id', rcube_utils::INPUT_GPC);
    if ($calid && ($cal = $this->get_calendar($calid))) {
      $folder = $cal->get_realname(); // UTF7
      $color  = $cal->get_color();
    }
    else {
      $folder = '';
      $color  = '';
    }

    $storage = $this->rc->get_storage();
    $delim   = $storage->get_hierarchy_delimiter();
    $form   = array();

    if (strlen($folder)) {
      $path_imap = explode($delim, $folder);
      array_pop($path_imap);  // pop off name part
      $path_imap = implode($path_imap, $delim);

      $options = $storage->folder_info($folder);

      // Allow plugins to modify the form content (e.g. with ACL form)
      $plugin = $this->rc->plugins->exec_hook('calendar_form_kolab',
        array('form' => $form, 'options' => $options, 'name' => $folder));
    }

    if (!$plugin['form']['sharing']['content'])
        $plugin['form']['sharing']['content'] = html::div('hint', $this->cal->gettext('aclnorights'));

    return $plugin['form']['sharing']['content'];
  }

  /**
   * Handler for user_delete plugin hook
   */
  public function user_delete($args)
  {
    $db = $this->rc->get_dbh();
    foreach (array('kolab_alarms', 'itipinvitations') as $table) {
      $db->query("DELETE FROM " . $this->rc->db->table_name($table, true)
        . " WHERE `user_id` = ?", $args['user']->ID);
    }
  }
}