1 files changed, 39 insertions, 5 deletions

diff --git a/apps/dav/lib/CalDAV/Schedule/Plugin.php b/apps/dav/lib/CalDAV/Schedule/Plugin.php
index 96bacce4454..74865297944 100644
--- a/apps/dav/lib/CalDAV/Schedule/Plugin.php
+++ b/apps/dav/lib/CalDAV/Schedule/Plugin.php
@@ -30,6 +30,7 @@ namespace OCA\DAV\CalDAV\Schedule;
 
 use DateTimeZone;
 use OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\CalDAV\Calendar;
 use OCA\DAV\CalDAV\CalendarHome;
 use OCP\IConfig;
 use Sabre\CalDAV\ICalendar;
@@ -299,12 +300,14 @@ EOF;
 					return null;
 				}
 
+				$isResourceOrRoom = strpos($principalUrl, 'principals/calendar-resources') === 0 ||
+					strpos($principalUrl, 'principals/calendar-rooms') === 0;
+
 				if (strpos($principalUrl, 'principals/users') === 0) {
 					[, $userId] = split($principalUrl);
 					$uri = $this->config->getUserValue($userId, 'dav', 'defaultCalendar', CalDavBackend::PERSONAL_CALENDAR_URI);
 					$displayName = CalDavBackend::PERSONAL_CALENDAR_NAME;
-				} elseif (strpos($principalUrl, 'principals/calendar-resources') === 0 ||
-						  strpos($principalUrl, 'principals/calendar-rooms') === 0) {
+				} elseif ($isResourceOrRoom) {
 					$uri = CalDavBackend::RESOURCE_BOOKING_CALENDAR_URI;
 					$displayName = CalDavBackend::RESOURCE_BOOKING_CALENDAR_NAME;
 				} else {
@@ -316,9 +319,40 @@ EOF;
 				/** @var CalendarHome $calendarHome */
 				$calendarHome = $this->server->tree->getNodeForPath($calendarHomePath);
 				if (!$calendarHome->childExists($uri)) {
-					$calendarHome->getCalDAVBackend()->createCalendar($principalUrl, $uri, [
-						'{DAV:}displayname' => $displayName,
-					]);
+					// If the default calendar doesn't exist
+					if ($isResourceOrRoom) {
+						$calendarHome->getCalDAVBackend()->createCalendar($principalUrl, $uri, [
+							'{DAV:}displayname' => $displayName,
+						]);
+					} else {
+						// And we're not handling scheduling on resource/room booking
+						$userCalendars = [];
+						/**
+						 * If the default calendar of the user isn't set and the
+						 * fallback doesn't match any of the user's calendar
+						 * try to find the first "personal" calendar we can write to
+						 * instead of creating a new one.
+						 * A appropriate personal calendar to receive invites:
+						 * - isn't a calendar subscription
+						 * - user can write to it (no virtual/3rd-party calendars)
+						 * - calendar isn't a share
+						 */
+						foreach ($calendarHome->getChildren() as $node) {
+							if ($node instanceof Calendar && !$node->isSubscription() && $node->canWrite() && !$node->isShared() && !$node->isDeleted()) {
+								$userCalendars[] = $node;
+							}
+						}
+
+						if (count($userCalendars) > 0) {
+							// Calendar backend returns calendar by calendarorder property
+							$uri = $userCalendars[0]->getName();
+						} else {
+							// Otherwise if we have really nothing, create a new calendar
+							$calendarHome->getCalDAVBackend()->createCalendar($principalUrl, $uri, [
+								'{DAV:}displayname' => $displayName,
+							]);
+						}
+					}
 				}
 
 				$result = $this->server->getPropertiesForPath($calendarHomePath . '/' . $uri, [], 1);