/**
  * @param ICalendar $calendar
  * @param \OCA\Calendar\IObject|\OCA\Calendar\IObjectCollection $data
  * @param TimezoneMapper $timezones
  */
 public function __construct(ICalendar $calendar, $data, TimezoneMapper $timezones)
 {
     $vobject = $data->getVObject();
     if ($vobject) {
         if ($timezones) {
             SabreUtility::addMissingVTimezones($vobject, $timezones);
         }
         $serialized = $vobject->serialize();
         $contentType = 'application/octet-stream';
         $filename = $calendar->getPublicUri();
         if ($data instanceof IObject) {
             $filename .= '-' . $data->getSummary();
         }
         $filename .= '.ics';
         parent::__construct($serialized, $filename, $contentType);
     }
 }