Overwrite the schedule target calendar with the personal one and create it if missing

Otherwise this leads to problems like events being added to the birthday calendar,
if that one is the first calendar which was created for the user. See:
https://github.com/nextcloud/server/pull/2274

Signed-off-by: Joas Schilling <coding@schilljs.com>

apps/dav/lib/CalDAV/CalendarHome.php

@@ -41,6 +41,13 @@ class CalendarHome extends \Sabre\CalDAV\CalendarHome {
 		$this->l10n = \OC::$server->getL10N('dav');
 	}
 
+	/**
+	 * @return BackendInterface
+	 */
+	public function getCalDAVBackend() {
+		return $this->caldavBackend;
+	}
+
 	/**
 	 * @inheritdoc
 	 */

apps/dav/lib/CalDAV/Schedule/Plugin.php

@@ -1,7 +1,9 @@
 <?php
 /**
  * @copyright Copyright (c) 2016, Roeland Jago Douma <roeland@famdouma.nl>
+ * @copyright Copyright (c) 2016, Joas Schilling <coding@schilljs.com>
  *
+ * @author Joas Schilling <coding@schilljs.com>
  * @author Roeland Jago Douma <roeland@famdouma.nl>
  *
  * @license GNU AGPL version 3 or any later version
@@ -22,8 +24,27 @@
  */
 namespace OCA\DAV\CalDAV\Schedule;
 
+use OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\CalDAV\CalendarHome;
+use Sabre\DAV\INode;
+use Sabre\DAV\PropFind;
+use Sabre\DAV\Server;
+use Sabre\DAV\Xml\Property\LocalHref;
+use Sabre\DAVACL\IPrincipal;
+
 class Plugin extends \Sabre\CalDAV\Schedule\Plugin {
 
+	/**
+	 * Initializes the plugin
+	 *
+	 * @param Server $server
+	 * @return void
+	 */
+	function initialize(Server $server) {
+		parent::initialize($server);
+		$server->on('propFind', [$this, 'propFindDefaultCalendarUrl'], 90);
+	}
+
 	/**
 	 * Returns a list of addresses that are associated with a principal.
 	 *
@@ -39,4 +60,42 @@ class Plugin extends \Sabre\CalDAV\Schedule\Plugin {
 
 		return $result;
 	}
+
+	/**
+	 * Always use the personal calendar as target for scheduled events
+	 *
+	 * @param PropFind $propFind
+	 * @param INode $node
+	 * @return void
+	 */
+	function propFindDefaultCalendarUrl(PropFind $propFind, INode $node) {
+		if ($node instanceof IPrincipal) {
+			$propFind->handle('{' . self::NS_CALDAV . '}schedule-default-calendar-URL', function() use ($node) {
+				/** @var \OCA\DAV\CalDAV\Plugin $caldavPlugin */
+				$caldavPlugin = $this->server->getPlugin('caldav');
+				$principalUrl = $node->getPrincipalUrl();
+
+				$calendarHomePath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl);
+
+				if (!$calendarHomePath) {
+					return null;
+				}
+
+				/** @var CalendarHome $calendarHome */
+				$calendarHome = $this->server->tree->getNodeForPath($calendarHomePath);
+				if (!$calendarHome->childExists(CalDavBackend::PERSONAL_CALENDAR_URI)) {
+					$calendarHome->getCalDAVBackend()->createCalendar($principalUrl, CalDavBackend::PERSONAL_CALENDAR_URI, [
+						'{DAV:}displayname' => CalDavBackend::PERSONAL_CALENDAR_NAME,
+					]);
+				}
+
+				$result = $this->server->getPropertiesForPath($calendarHomePath . '/' . CalDavBackend::PERSONAL_CALENDAR_URI, [], 1);
+				if (empty($result)) {
+					return null;
+				}
+
+				return new LocalHref($result[0]['href']);
+			});
+		}
+	}
 }