Add a trashbin for calendars and calendar objects

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

apps/dav/appinfo/info.xml

@@ -5,7 +5,7 @@
 	<name>WebDAV</name>
 	<summary>WebDAV endpoint</summary>
 	<description>WebDAV endpoint</description>
-	<version>1.17.2</version>
+	<version>1.18.0</version>
 	<licence>agpl</licence>
 	<author>owncloud.org</author>
 	<namespace>DAV</namespace>
@@ -24,6 +24,7 @@
 		<job>OCA\DAV\BackgroundJob\UpdateCalendarResourcesRoomsBackgroundJob</job>
 		<job>OCA\DAV\BackgroundJob\CleanupInvitationTokenJob</job>
 		<job>OCA\DAV\BackgroundJob\EventReminderJob</job>
+		<job>OCA\DAV\BackgroundJob\CalendarRetentionJob</job>
 	</background-jobs>
 
 	<repair-steps>
@@ -48,6 +49,7 @@
 		<command>OCA\DAV\Command\CreateCalendar</command>
 		<command>OCA\DAV\Command\MoveCalendar</command>
 		<command>OCA\DAV\Command\ListCalendars</command>
+		<command>OCA\DAV\Command\RetentionCleanupCommand</command>
 		<command>OCA\DAV\Command\SendEventReminders</command>
 		<command>OCA\DAV\Command\SyncBirthdayCalendar</command>
 		<command>OCA\DAV\Command\SyncSystemAddressBook</command>

apps/dav/appinfo/v1/caldav.php

@@ -61,8 +61,20 @@ $random = \OC::$server->getSecureRandom();
 $logger = \OC::$server->getLogger();
 $dispatcher = \OC::$server->get(\OCP\EventDispatcher\IEventDispatcher::class);
 $legacyDispatcher = \OC::$server->getEventDispatcher();
+$config = \OC::$server->get(\OCP\IConfig::class);
 
-$calDavBackend = new CalDavBackend($db, $principalBackend, $userManager, \OC::$server->getGroupManager(), $random, $logger, $dispatcher, $legacyDispatcher, true);
+$calDavBackend = new CalDavBackend(
+	$db,
+	$principalBackend,
+	$userManager,
+	\OC::$server->getGroupManager(),
+	$random,
+	$logger,
+	$dispatcher,
+	$legacyDispatcher,
+	$config,
+	true
+);
 
 $debugging = \OC::$server->getConfig()->getSystemValue('debug', false);
 $sendInvitations = \OC::$server->getConfig()->getAppValue('dav', 'sendInvitations', 'yes') === 'yes';

apps/dav/composer/composer/autoload_classmap.php

@@ -13,6 +13,7 @@ return array(
     'OCA\\DAV\\Avatars\\AvatarNode' => $baseDir . '/../lib/Avatars/AvatarNode.php',
     'OCA\\DAV\\Avatars\\RootCollection' => $baseDir . '/../lib/Avatars/RootCollection.php',
     'OCA\\DAV\\BackgroundJob\\BuildReminderIndexBackgroundJob' => $baseDir . '/../lib/BackgroundJob/BuildReminderIndexBackgroundJob.php',
+    'OCA\\DAV\\BackgroundJob\\CalendarRetentionJob' => $baseDir . '/../lib/BackgroundJob/CalendarRetentionJob.php',
     'OCA\\DAV\\BackgroundJob\\CleanupDirectLinksJob' => $baseDir . '/../lib/BackgroundJob/CleanupDirectLinksJob.php',
     'OCA\\DAV\\BackgroundJob\\CleanupInvitationTokenJob' => $baseDir . '/../lib/BackgroundJob/CleanupInvitationTokenJob.php',
     'OCA\\DAV\\BackgroundJob\\EventReminderJob' => $baseDir . '/../lib/BackgroundJob/EventReminderJob.php',
@@ -44,6 +45,7 @@ return array(
     'OCA\\DAV\\CalDAV\\CalendarObject' => $baseDir . '/../lib/CalDAV/CalendarObject.php',
     'OCA\\DAV\\CalDAV\\CalendarRoot' => $baseDir . '/../lib/CalDAV/CalendarRoot.php',
     'OCA\\DAV\\CalDAV\\ICSExportPlugin\\ICSExportPlugin' => $baseDir . '/../lib/CalDAV/ICSExportPlugin/ICSExportPlugin.php',
+    'OCA\\DAV\\CalDAV\\IRestorable' => $baseDir . '/../lib/CalDAV/IRestorable.php',
     'OCA\\DAV\\CalDAV\\Integration\\ExternalCalendar' => $baseDir . '/../lib/CalDAV/Integration/ExternalCalendar.php',
     'OCA\\DAV\\CalDAV\\Integration\\ICalendarProvider' => $baseDir . '/../lib/CalDAV/Integration/ICalendarProvider.php',
     'OCA\\DAV\\CalDAV\\InvitationResponse\\InvitationResponseServer' => $baseDir . '/../lib/CalDAV/InvitationResponse/InvitationResponseServer.php',
@@ -72,6 +74,7 @@ return array(
     'OCA\\DAV\\CalDAV\\ResourceBooking\\AbstractPrincipalBackend' => $baseDir . '/../lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php',
     'OCA\\DAV\\CalDAV\\ResourceBooking\\ResourcePrincipalBackend' => $baseDir . '/../lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php',
     'OCA\\DAV\\CalDAV\\ResourceBooking\\RoomPrincipalBackend' => $baseDir . '/../lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php',
+    'OCA\\DAV\\CalDAV\\RetentionService' => $baseDir . '/../lib/CalDAV/RetentionService.php',
     'OCA\\DAV\\CalDAV\\Schedule\\IMipPlugin' => $baseDir . '/../lib/CalDAV/Schedule/IMipPlugin.php',
     'OCA\\DAV\\CalDAV\\Schedule\\Plugin' => $baseDir . '/../lib/CalDAV/Schedule/Plugin.php',
     'OCA\\DAV\\CalDAV\\Search\\SearchPlugin' => $baseDir . '/../lib/CalDAV/Search/SearchPlugin.php',
@@ -82,6 +85,11 @@ return array(
     'OCA\\DAV\\CalDAV\\Search\\Xml\\Filter\\PropFilter' => $baseDir . '/../lib/CalDAV/Search/Xml/Filter/PropFilter.php',
     'OCA\\DAV\\CalDAV\\Search\\Xml\\Filter\\SearchTermFilter' => $baseDir . '/../lib/CalDAV/Search/Xml/Filter/SearchTermFilter.php',
     'OCA\\DAV\\CalDAV\\Search\\Xml\\Request\\CalendarSearchReport' => $baseDir . '/../lib/CalDAV/Search/Xml/Request/CalendarSearchReport.php',
+    'OCA\\DAV\\CalDAV\\Trashbin\\DeletedCalendarObject' => $baseDir . '/../lib/CalDAV/Trashbin/DeletedCalendarObject.php',
+    'OCA\\DAV\\CalDAV\\Trashbin\\DeletedCalendarObjectsCollection' => $baseDir . '/../lib/CalDAV/Trashbin/DeletedCalendarObjectsCollection.php',
+    'OCA\\DAV\\CalDAV\\Trashbin\\Plugin' => $baseDir . '/../lib/CalDAV/Trashbin/Plugin.php',
+    'OCA\\DAV\\CalDAV\\Trashbin\\RestoreTarget' => $baseDir . '/../lib/CalDAV/Trashbin/RestoreTarget.php',
+    'OCA\\DAV\\CalDAV\\Trashbin\\TrashbinHome' => $baseDir . '/../lib/CalDAV/Trashbin/TrashbinHome.php',
     'OCA\\DAV\\CalDAV\\WebcalCaching\\Plugin' => $baseDir . '/../lib/CalDAV/WebcalCaching/Plugin.php',
     'OCA\\DAV\\CalDAV\\WebcalCaching\\RefreshWebcalService' => $baseDir . '/../lib/CalDAV/WebcalCaching/RefreshWebcalService.php',
     'OCA\\DAV\\Capabilities' => $baseDir . '/../lib/Capabilities.php',
@@ -113,6 +121,7 @@ return array(
     'OCA\\DAV\\Command\\ListCalendars' => $baseDir . '/../lib/Command/ListCalendars.php',
     'OCA\\DAV\\Command\\MoveCalendar' => $baseDir . '/../lib/Command/MoveCalendar.php',
     'OCA\\DAV\\Command\\RemoveInvalidShares' => $baseDir . '/../lib/Command/RemoveInvalidShares.php',
+    'OCA\\DAV\\Command\\RetentionCleanupCommand' => $baseDir . '/../lib/Command/RetentionCleanupCommand.php',
     'OCA\\DAV\\Command\\SendEventReminders' => $baseDir . '/../lib/Command/SendEventReminders.php',
     'OCA\\DAV\\Command\\SyncBirthdayCalendar' => $baseDir . '/../lib/Command/SyncBirthdayCalendar.php',
     'OCA\\DAV\\Command\\SyncSystemAddressBook' => $baseDir . '/../lib/Command/SyncSystemAddressBook.php',
@@ -188,10 +197,14 @@ return array(
     'OCA\\DAV\\Events\\CachedCalendarObjectUpdatedEvent' => $baseDir . '/../lib/Events/CachedCalendarObjectUpdatedEvent.php',
     'OCA\\DAV\\Events\\CalendarCreatedEvent' => $baseDir . '/../lib/Events/CalendarCreatedEvent.php',
     'OCA\\DAV\\Events\\CalendarDeletedEvent' => $baseDir . '/../lib/Events/CalendarDeletedEvent.php',
+    'OCA\\DAV\\Events\\CalendarMovedToTrashEvent' => $baseDir . '/../lib/Events/CalendarMovedToTrashEvent.php',
     'OCA\\DAV\\Events\\CalendarObjectCreatedEvent' => $baseDir . '/../lib/Events/CalendarObjectCreatedEvent.php',
     'OCA\\DAV\\Events\\CalendarObjectDeletedEvent' => $baseDir . '/../lib/Events/CalendarObjectDeletedEvent.php',
+    'OCA\\DAV\\Events\\CalendarObjectMovedToTrashEvent' => $baseDir . '/../lib/Events/CalendarObjectMovedToTrashEvent.php',
+    'OCA\\DAV\\Events\\CalendarObjectRestoredEvent' => $baseDir . '/../lib/Events/CalendarObjectRestoredEvent.php',
     'OCA\\DAV\\Events\\CalendarObjectUpdatedEvent' => $baseDir . '/../lib/Events/CalendarObjectUpdatedEvent.php',
     'OCA\\DAV\\Events\\CalendarPublishedEvent' => $baseDir . '/../lib/Events/CalendarPublishedEvent.php',
+    'OCA\\DAV\\Events\\CalendarRestoredEvent' => $baseDir . '/../lib/Events/CalendarRestoredEvent.php',
     'OCA\\DAV\\Events\\CalendarShareUpdatedEvent' => $baseDir . '/../lib/Events/CalendarShareUpdatedEvent.php',
     'OCA\\DAV\\Events\\CalendarUnpublishedEvent' => $baseDir . '/../lib/Events/CalendarUnpublishedEvent.php',
     'OCA\\DAV\\Events\\CalendarUpdatedEvent' => $baseDir . '/../lib/Events/CalendarUpdatedEvent.php',
@@ -248,6 +261,7 @@ return array(
     'OCA\\DAV\\Migration\\Version1012Date20190808122342' => $baseDir . '/../lib/Migration/Version1012Date20190808122342.php',
     'OCA\\DAV\\Migration\\Version1016Date20201109085907' => $baseDir . '/../lib/Migration/Version1016Date20201109085907.php',
     'OCA\\DAV\\Migration\\Version1017Date20210216083742' => $baseDir . '/../lib/Migration/Version1017Date20210216083742.php',
+    'OCA\\DAV\\Migration\\Version1018Date20210312100735' => $baseDir . '/../lib/Migration/Version1018Date20210312100735.php',
     'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningNode' => $baseDir . '/../lib/Provisioning/Apple/AppleProvisioningNode.php',
     'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningPlugin' => $baseDir . '/../lib/Provisioning/Apple/AppleProvisioningPlugin.php',
     'OCA\\DAV\\RootCollection' => $baseDir . '/../lib/RootCollection.php',

apps/dav/composer/composer/autoload_static.php

@@ -28,6 +28,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Avatars\\AvatarNode' => __DIR__ . '/..' . '/../lib/Avatars/AvatarNode.php',
         'OCA\\DAV\\Avatars\\RootCollection' => __DIR__ . '/..' . '/../lib/Avatars/RootCollection.php',
         'OCA\\DAV\\BackgroundJob\\BuildReminderIndexBackgroundJob' => __DIR__ . '/..' . '/../lib/BackgroundJob/BuildReminderIndexBackgroundJob.php',
+        'OCA\\DAV\\BackgroundJob\\CalendarRetentionJob' => __DIR__ . '/..' . '/../lib/BackgroundJob/CalendarRetentionJob.php',
         'OCA\\DAV\\BackgroundJob\\CleanupDirectLinksJob' => __DIR__ . '/..' . '/../lib/BackgroundJob/CleanupDirectLinksJob.php',
         'OCA\\DAV\\BackgroundJob\\CleanupInvitationTokenJob' => __DIR__ . '/..' . '/../lib/BackgroundJob/CleanupInvitationTokenJob.php',
         'OCA\\DAV\\BackgroundJob\\EventReminderJob' => __DIR__ . '/..' . '/../lib/BackgroundJob/EventReminderJob.php',
@@ -59,6 +60,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\CalDAV\\CalendarObject' => __DIR__ . '/..' . '/../lib/CalDAV/CalendarObject.php',
         'OCA\\DAV\\CalDAV\\CalendarRoot' => __DIR__ . '/..' . '/../lib/CalDAV/CalendarRoot.php',
         'OCA\\DAV\\CalDAV\\ICSExportPlugin\\ICSExportPlugin' => __DIR__ . '/..' . '/../lib/CalDAV/ICSExportPlugin/ICSExportPlugin.php',
+        'OCA\\DAV\\CalDAV\\IRestorable' => __DIR__ . '/..' . '/../lib/CalDAV/IRestorable.php',
         'OCA\\DAV\\CalDAV\\Integration\\ExternalCalendar' => __DIR__ . '/..' . '/../lib/CalDAV/Integration/ExternalCalendar.php',
         'OCA\\DAV\\CalDAV\\Integration\\ICalendarProvider' => __DIR__ . '/..' . '/../lib/CalDAV/Integration/ICalendarProvider.php',
         'OCA\\DAV\\CalDAV\\InvitationResponse\\InvitationResponseServer' => __DIR__ . '/..' . '/../lib/CalDAV/InvitationResponse/InvitationResponseServer.php',
@@ -87,6 +89,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\CalDAV\\ResourceBooking\\AbstractPrincipalBackend' => __DIR__ . '/..' . '/../lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php',
         'OCA\\DAV\\CalDAV\\ResourceBooking\\ResourcePrincipalBackend' => __DIR__ . '/..' . '/../lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php',
         'OCA\\DAV\\CalDAV\\ResourceBooking\\RoomPrincipalBackend' => __DIR__ . '/..' . '/../lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php',
+        'OCA\\DAV\\CalDAV\\RetentionService' => __DIR__ . '/..' . '/../lib/CalDAV/RetentionService.php',
         'OCA\\DAV\\CalDAV\\Schedule\\IMipPlugin' => __DIR__ . '/..' . '/../lib/CalDAV/Schedule/IMipPlugin.php',
         'OCA\\DAV\\CalDAV\\Schedule\\Plugin' => __DIR__ . '/..' . '/../lib/CalDAV/Schedule/Plugin.php',
         'OCA\\DAV\\CalDAV\\Search\\SearchPlugin' => __DIR__ . '/..' . '/../lib/CalDAV/Search/SearchPlugin.php',
@@ -97,6 +100,11 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\CalDAV\\Search\\Xml\\Filter\\PropFilter' => __DIR__ . '/..' . '/../lib/CalDAV/Search/Xml/Filter/PropFilter.php',
         'OCA\\DAV\\CalDAV\\Search\\Xml\\Filter\\SearchTermFilter' => __DIR__ . '/..' . '/../lib/CalDAV/Search/Xml/Filter/SearchTermFilter.php',
         'OCA\\DAV\\CalDAV\\Search\\Xml\\Request\\CalendarSearchReport' => __DIR__ . '/..' . '/../lib/CalDAV/Search/Xml/Request/CalendarSearchReport.php',
+        'OCA\\DAV\\CalDAV\\Trashbin\\DeletedCalendarObject' => __DIR__ . '/..' . '/../lib/CalDAV/Trashbin/DeletedCalendarObject.php',
+        'OCA\\DAV\\CalDAV\\Trashbin\\DeletedCalendarObjectsCollection' => __DIR__ . '/..' . '/../lib/CalDAV/Trashbin/DeletedCalendarObjectsCollection.php',
+        'OCA\\DAV\\CalDAV\\Trashbin\\Plugin' => __DIR__ . '/..' . '/../lib/CalDAV/Trashbin/Plugin.php',
+        'OCA\\DAV\\CalDAV\\Trashbin\\RestoreTarget' => __DIR__ . '/..' . '/../lib/CalDAV/Trashbin/RestoreTarget.php',
+        'OCA\\DAV\\CalDAV\\Trashbin\\TrashbinHome' => __DIR__ . '/..' . '/../lib/CalDAV/Trashbin/TrashbinHome.php',
         'OCA\\DAV\\CalDAV\\WebcalCaching\\Plugin' => __DIR__ . '/..' . '/../lib/CalDAV/WebcalCaching/Plugin.php',
         'OCA\\DAV\\CalDAV\\WebcalCaching\\RefreshWebcalService' => __DIR__ . '/..' . '/../lib/CalDAV/WebcalCaching/RefreshWebcalService.php',
         'OCA\\DAV\\Capabilities' => __DIR__ . '/..' . '/../lib/Capabilities.php',
@@ -128,6 +136,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Command\\ListCalendars' => __DIR__ . '/..' . '/../lib/Command/ListCalendars.php',
         'OCA\\DAV\\Command\\MoveCalendar' => __DIR__ . '/..' . '/../lib/Command/MoveCalendar.php',
         'OCA\\DAV\\Command\\RemoveInvalidShares' => __DIR__ . '/..' . '/../lib/Command/RemoveInvalidShares.php',
+        'OCA\\DAV\\Command\\RetentionCleanupCommand' => __DIR__ . '/..' . '/../lib/Command/RetentionCleanupCommand.php',
         'OCA\\DAV\\Command\\SendEventReminders' => __DIR__ . '/..' . '/../lib/Command/SendEventReminders.php',
         'OCA\\DAV\\Command\\SyncBirthdayCalendar' => __DIR__ . '/..' . '/../lib/Command/SyncBirthdayCalendar.php',
         'OCA\\DAV\\Command\\SyncSystemAddressBook' => __DIR__ . '/..' . '/../lib/Command/SyncSystemAddressBook.php',
@@ -203,10 +212,14 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Events\\CachedCalendarObjectUpdatedEvent' => __DIR__ . '/..' . '/../lib/Events/CachedCalendarObjectUpdatedEvent.php',
         'OCA\\DAV\\Events\\CalendarCreatedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarCreatedEvent.php',
         'OCA\\DAV\\Events\\CalendarDeletedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarDeletedEvent.php',
+        'OCA\\DAV\\Events\\CalendarMovedToTrashEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarMovedToTrashEvent.php',
         'OCA\\DAV\\Events\\CalendarObjectCreatedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarObjectCreatedEvent.php',
         'OCA\\DAV\\Events\\CalendarObjectDeletedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarObjectDeletedEvent.php',
+        'OCA\\DAV\\Events\\CalendarObjectMovedToTrashEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarObjectMovedToTrashEvent.php',
+        'OCA\\DAV\\Events\\CalendarObjectRestoredEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarObjectRestoredEvent.php',
         'OCA\\DAV\\Events\\CalendarObjectUpdatedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarObjectUpdatedEvent.php',
         'OCA\\DAV\\Events\\CalendarPublishedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarPublishedEvent.php',
+        'OCA\\DAV\\Events\\CalendarRestoredEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarRestoredEvent.php',
         'OCA\\DAV\\Events\\CalendarShareUpdatedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarShareUpdatedEvent.php',
         'OCA\\DAV\\Events\\CalendarUnpublishedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarUnpublishedEvent.php',
         'OCA\\DAV\\Events\\CalendarUpdatedEvent' => __DIR__ . '/..' . '/../lib/Events/CalendarUpdatedEvent.php',
@@ -263,6 +276,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Migration\\Version1012Date20190808122342' => __DIR__ . '/..' . '/../lib/Migration/Version1012Date20190808122342.php',
         'OCA\\DAV\\Migration\\Version1016Date20201109085907' => __DIR__ . '/..' . '/../lib/Migration/Version1016Date20201109085907.php',
         'OCA\\DAV\\Migration\\Version1017Date20210216083742' => __DIR__ . '/..' . '/../lib/Migration/Version1017Date20210216083742.php',
+        'OCA\\DAV\\Migration\\Version1018Date20210312100735' => __DIR__ . '/..' . '/../lib/Migration/Version1018Date20210312100735.php',
         'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningNode' => __DIR__ . '/..' . '/../lib/Provisioning/Apple/AppleProvisioningNode.php',
         'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningPlugin' => __DIR__ . '/..' . '/../lib/Provisioning/Apple/AppleProvisioningPlugin.php',
         'OCA\\DAV\\RootCollection' => __DIR__ . '/..' . '/../lib/RootCollection.php',

apps/dav/lib/AppInfo/Application.php

@@ -57,9 +57,13 @@ use OCA\DAV\Events\AddressBookShareUpdatedEvent;
 use OCA\DAV\Events\AddressBookUpdatedEvent;
 use OCA\DAV\Events\CalendarCreatedEvent;
 use OCA\DAV\Events\CalendarDeletedEvent;
+use OCA\DAV\Events\CalendarMovedToTrashEvent;
 use OCA\DAV\Events\CalendarObjectCreatedEvent;
 use OCA\DAV\Events\CalendarObjectDeletedEvent;
+use OCA\DAV\Events\CalendarObjectMovedToTrashEvent;
+use OCA\DAV\Events\CalendarObjectRestoredEvent;
 use OCA\DAV\Events\CalendarObjectUpdatedEvent;
+use OCA\DAV\Events\CalendarRestoredEvent;
 use OCA\DAV\Events\CalendarShareUpdatedEvent;
 use OCA\DAV\Events\CalendarUpdatedEvent;
 use OCA\DAV\Events\CardCreatedEvent;
@@ -129,7 +133,11 @@ class Application extends App implements IBootstrap {
 		$context->registerEventListener(CalendarDeletedEvent::class, ActivityUpdaterListener::class);
 		$context->registerEventListener(CalendarDeletedEvent::class, CalendarObjectReminderUpdaterListener::class);
 		$context->registerEventListener(CalendarDeletedEvent::class, CalendarDeletionDefaultUpdaterListener::class);
+		$context->registerEventListener(CalendarMovedToTrashEvent::class, ActivityUpdaterListener::class);
+		$context->registerEventListener(CalendarMovedToTrashEvent::class, CalendarObjectReminderUpdaterListener::class);
 		$context->registerEventListener(CalendarUpdatedEvent::class, ActivityUpdaterListener::class);
+		$context->registerEventListener(CalendarRestoredEvent::class, ActivityUpdaterListener::class);
+		$context->registerEventListener(CalendarRestoredEvent::class, CalendarObjectReminderUpdaterListener::class);
 		$context->registerEventListener(CalendarObjectCreatedEvent::class, ActivityUpdaterListener::class);
 		$context->registerEventListener(CalendarObjectCreatedEvent::class, CalendarContactInteractionListener::class);
 		$context->registerEventListener(CalendarObjectCreatedEvent::class, CalendarObjectReminderUpdaterListener::class);
@@ -138,6 +146,10 @@ class Application extends App implements IBootstrap {
 		$context->registerEventListener(CalendarObjectUpdatedEvent::class, CalendarObjectReminderUpdaterListener::class);
 		$context->registerEventListener(CalendarObjectDeletedEvent::class, ActivityUpdaterListener::class);
 		$context->registerEventListener(CalendarObjectDeletedEvent::class, CalendarObjectReminderUpdaterListener::class);
+		$context->registerEventListener(CalendarObjectMovedToTrashEvent::class, ActivityUpdaterListener::class);
+		$context->registerEventListener(CalendarObjectMovedToTrashEvent::class, CalendarObjectReminderUpdaterListener::class);
+		$context->registerEventListener(CalendarObjectRestoredEvent::class, ActivityUpdaterListener::class);
+		$context->registerEventListener(CalendarObjectRestoredEvent::class, CalendarObjectReminderUpdaterListener::class);
 		$context->registerEventListener(CalendarShareUpdatedEvent::class, CalendarContactInteractionListener::class);
 
 
@@ -220,6 +232,7 @@ class Application extends App implements IBootstrap {
 			$syncService->updateUser($user);
 		});
 
+
 		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::updateShares', function (GenericEvent $event) use ($container) {
 			/** @var Backend $backend */
 			$backend = $container->query(Backend::class);

apps/dav/lib/BackgroundJob/CalendarRetentionJob.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\BackgroundJob;
+
+use OCA\DAV\CalDAV\RetentionService;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\TimedJob;
+
+class CalendarRetentionJob extends TimedJob {
+	/** @var RetentionService */
+	private $service;
+
+	public function __construct(ITimeFactory $time,
+								RetentionService $service) {
+		parent::__construct($time);
+		$this->service = $service;
+
+		// Run four times a day
+		$this->setInterval(6 * 60 * 60);
+	}
+
+	protected function run($argument): void {
+		$this->service->cleanUp();
+	}
+}

apps/dav/lib/BackgroundJob/UpdateCalendarResourcesRoomsBackgroundJob.php

@@ -415,7 +415,10 @@ class UpdateCalendarResourcesRoomsBackgroundJob extends TimedJob {
 			CalDavBackend::RESOURCE_BOOKING_CALENDAR_URI);
 
 		if ($calendar !== null) {
-			$this->calDavBackend->deleteCalendar($calendar['id']);
+			$this->calDavBackend->deleteCalendar(
+				$calendar['id'],
+				true // Because this wasn't deleted by a user
+			);
 		}
 	}
 

apps/dav/lib/CalDAV/Activity/Backend.php

@@ -84,13 +84,33 @@ class Backend {
 		$this->triggerCalendarActivity(Calendar::SUBJECT_UPDATE, $calendarData, $shares, $properties);
 	}
 
+	/**
+	 * Creates activities when a calendar was moved to trash
+	 *
+	 * @param array $calendarData
+	 * @param array $shares
+	 */
+	public function onCalendarMovedToTrash(array $calendarData, array $shares): void {
+		$this->triggerCalendarActivity(Calendar::SUBJECT_MOVE_TO_TRASH, $calendarData, $shares);
+	}
+
+	/**
+	 * Creates activities when a calendar was restored
+	 *
+	 * @param array $calendarData
+	 * @param array $shares
+	 */
+	public function onCalendarRestored(array $calendarData, array $shares): void {
+		$this->triggerCalendarActivity(Calendar::SUBJECT_RESTORE, $calendarData, $shares);
+	}
+
 	/**
 	 * Creates activities when a calendar was deleted
 	 *
 	 * @param array $calendarData
 	 * @param array $shares
 	 */
-	public function onCalendarDelete(array $calendarData, array $shares) {
+	public function onCalendarDelete(array $calendarData, array $shares): void {
 		$this->triggerCalendarActivity(Calendar::SUBJECT_DELETE, $calendarData, $shares);
 	}
 

apps/dav/lib/CalDAV/Activity/Provider/Calendar.php

@@ -39,6 +39,8 @@ use OCP\L10N\IFactory;
 class Calendar extends Base {
 	public const SUBJECT_ADD = 'calendar_add';
 	public const SUBJECT_UPDATE = 'calendar_update';
+	public const SUBJECT_MOVE_TO_TRASH = 'calendar_move_to_trash';
+	public const SUBJECT_RESTORE = 'calendar_restore';
 	public const SUBJECT_DELETE = 'calendar_delete';
 	public const SUBJECT_PUBLISH = 'calendar_publish';
 	public const SUBJECT_UNPUBLISH = 'calendar_unpublish';
@@ -107,6 +109,14 @@ class Calendar extends Base {
 			$subject = $this->l->t('{actor} updated calendar {calendar}');
 		} elseif ($event->getSubject() === self::SUBJECT_UPDATE . '_self') {
 			$subject = $this->l->t('You updated calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_MOVE_TO_TRASH) {
+			$subject = $this->l->t('{actor} deleted calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_MOVE_TO_TRASH . '_self') {
+			$subject = $this->l->t('You deleted calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_RESTORE) {
+			$subject = $this->l->t('{actor} restored calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_RESTORE . '_self') {
+			$subject = $this->l->t('You restored calendar {calendar}');
 		} elseif ($event->getSubject() === self::SUBJECT_PUBLISH . '_self') {
 			$subject = $this->l->t('You shared calendar {calendar} as public link');
 		} elseif ($event->getSubject() === self::SUBJECT_UNPUBLISH . '_self') {
@@ -172,6 +182,10 @@ class Calendar extends Base {
 				case self::SUBJECT_DELETE . '_self':
 				case self::SUBJECT_UPDATE:
 				case self::SUBJECT_UPDATE . '_self':
+				case self::SUBJECT_MOVE_TO_TRASH:
+				case self::SUBJECT_MOVE_TO_TRASH . '_self':
+				case self::SUBJECT_RESTORE:
+				case self::SUBJECT_RESTORE . '_self':
 				case self::SUBJECT_PUBLISH . '_self':
 				case self::SUBJECT_UNPUBLISH . '_self':
 				case self::SUBJECT_SHARE_USER:

apps/dav/lib/CalDAV/Activity/Provider/Event.php

@@ -40,6 +40,8 @@ use OCP\L10N\IFactory;
 class Event extends Base {
 	public const SUBJECT_OBJECT_ADD = 'object_add';
 	public const SUBJECT_OBJECT_UPDATE = 'object_update';
+	public const SUBJECT_OBJECT_MOVE_TO_TRASH = 'object_move_to_trash';
+	public const SUBJECT_OBJECT_RESTORE = 'object_restore';
 	public const SUBJECT_OBJECT_DELETE = 'object_delete';
 
 	/** @var IFactory */
@@ -143,6 +145,14 @@ class Event extends Base {
 			$subject = $this->l->t('{actor} updated event {event} in calendar {calendar}');
 		} elseif ($event->getSubject() === self::SUBJECT_OBJECT_UPDATE . '_event_self') {
 			$subject = $this->l->t('You updated event {event} in calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_OBJECT_MOVE_TO_TRASH . '_event') {
+			$subject = $this->l->t('{actor} deleted event {event} from calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_OBJECT_MOVE_TO_TRASH . '_event_self') {
+			$subject = $this->l->t('You deleted event {event} from calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_OBJECT_RESTORE . '_event') {
+			$subject = $this->l->t('{actor} restored event {event} of calendar {calendar}');
+		} elseif ($event->getSubject() === self::SUBJECT_OBJECT_RESTORE . '_event_self') {
+			$subject = $this->l->t('You restored event {event} of calendar {calendar}');
 		} else {
 			throw new \InvalidArgumentException();
 		}
@@ -169,6 +179,8 @@ class Event extends Base {
 				case self::SUBJECT_OBJECT_ADD . '_event':
 				case self::SUBJECT_OBJECT_DELETE . '_event':
 				case self::SUBJECT_OBJECT_UPDATE . '_event':
+				case self::SUBJECT_OBJECT_MOVE_TO_TRASH . '_event':
+				case self::SUBJECT_OBJECT_RESTORE . '_event':
 					return [
 						'actor' => $this->generateUserParameter($parameters['actor']),
 						'calendar' => $this->generateCalendarParameter($parameters['calendar'], $this->l),
@@ -177,6 +189,8 @@ class Event extends Base {
 				case self::SUBJECT_OBJECT_ADD . '_event_self':
 				case self::SUBJECT_OBJECT_DELETE . '_event_self':
 				case self::SUBJECT_OBJECT_UPDATE . '_event_self':
+				case self::SUBJECT_OBJECT_MOVE_TO_TRASH . '_event_self':
+				case self::SUBJECT_OBJECT_RESTORE . '_event_self':
 					return [
 						'calendar' => $this->generateCalendarParameter($parameters['calendar'], $this->l),
 						'event' => $this->generateClassifiedObjectParameter($parameters['object']),

apps/dav/lib/CalDAV/CalDavBackend.php

@@ -39,6 +39,7 @@
 namespace OCA\DAV\CalDAV;
 
 use DateTime;
+use OCA\DAV\AppInfo\Application;
 use OCA\DAV\Connector\Sabre\Principal;
 use OCA\DAV\DAV\Sharing\Backend;
 use OCA\DAV\DAV\Sharing\IShareable;
@@ -47,10 +48,14 @@ use OCA\DAV\Events\CachedCalendarObjectDeletedEvent;
 use OCA\DAV\Events\CachedCalendarObjectUpdatedEvent;
 use OCA\DAV\Events\CalendarCreatedEvent;
 use OCA\DAV\Events\CalendarDeletedEvent;
+use OCA\DAV\Events\CalendarMovedToTrashEvent;
 use OCA\DAV\Events\CalendarObjectCreatedEvent;
 use OCA\DAV\Events\CalendarObjectDeletedEvent;
+use OCA\DAV\Events\CalendarObjectMovedToTrashEvent;
+use OCA\DAV\Events\CalendarObjectRestoredEvent;
 use OCA\DAV\Events\CalendarObjectUpdatedEvent;
 use OCA\DAV\Events\CalendarPublishedEvent;
+use OCA\DAV\Events\CalendarRestoredEvent;
 use OCA\DAV\Events\CalendarShareUpdatedEvent;
 use OCA\DAV\Events\CalendarUnpublishedEvent;
 use OCA\DAV\Events\CalendarUpdatedEvent;
@@ -59,12 +64,14 @@ use OCA\DAV\Events\SubscriptionDeletedEvent;
 use OCA\DAV\Events\SubscriptionUpdatedEvent;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\ILogger;
 use OCP\IUser;
 use OCP\IUserManager;
 use OCP\Security\ISecureRandom;
+use RuntimeException;
 use Sabre\CalDAV\Backend\AbstractBackend;
 use Sabre\CalDAV\Backend\SchedulingSupport;
 use Sabre\CalDAV\Backend\SubscriptionSupport;
@@ -72,6 +79,7 @@ use Sabre\CalDAV\Backend\SyncSupport;
 use Sabre\CalDAV\Xml\Property\ScheduleCalendarTransp;
 use Sabre\CalDAV\Xml\Property\SupportedCalendarComponentSet;
 use Sabre\DAV;
+use Sabre\DAV\Exception\BadRequest;
 use Sabre\DAV\Exception\Forbidden;
 use Sabre\DAV\Exception\NotFound;
 use Sabre\DAV\PropPatch;
@@ -87,6 +95,15 @@ use Sabre\VObject\Reader;
 use Sabre\VObject\Recur\EventIterator;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\EventDispatcher\GenericEvent;
+use function array_merge;
+use function array_values;
+use function explode;
+use function is_array;
+use function pathinfo;
+use function sprintf;
+use function str_replace;
+use function strtolower;
+use function time;
 
 /**
  * Class CalDavBackend
@@ -134,6 +151,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		'{urn:ietf:params:xml:ns:caldav}calendar-timezone' => 'timezone',
 		'{http://apple.com/ns/ical/}calendar-order' => 'calendarorder',
 		'{http://apple.com/ns/ical/}calendar-color' => 'calendarcolor',
+		'{' . \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD . '}deleted-at' => 'deleted_at',
 	];
 
 	/**
@@ -191,6 +209,9 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	/** @var EventDispatcherInterface */
 	private $legacyDispatcher;
 
+	/** @var IConfig */
+	private $config;
+
 	/** @var bool */
 	private $legacyEndpoint;
 
@@ -218,6 +239,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 								ILogger $logger,
 								IEventDispatcher $dispatcher,
 								EventDispatcherInterface $legacyDispatcher,
+								IConfig $config,
 								bool $legacyEndpoint = false) {
 		$this->db = $db;
 		$this->principalBackend = $principalBackend;
@@ -227,6 +249,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		$this->logger = $logger;
 		$this->dispatcher = $dispatcher;
 		$this->legacyDispatcher = $legacyDispatcher;
+		$this->config = $config;
 		$this->legacyEndpoint = $legacyEndpoint;
 	}
 
@@ -261,6 +284,26 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		return $column;
 	}
 
+	/**
+	 * @return array{id: int, deleted_at: int}[]
+	 */
+	public function getDeletedCalendars(int $deletedBefore): array {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select(['id', 'deleted_at'])
+			->from('calendars')
+			->where($qb->expr()->isNotNull('deleted_at'))
+			->andWhere($qb->expr()->lt('deleted_at', $qb->createNamedParameter($deletedBefore)));
+		$result = $qb->executeQuery();
+		$raw = $result->fetchAll();
+		$result->closeCursor();
+		return array_map(function ($row) {
+			return [
+				'id' => (int) $row['id'],
+				'deleted_at' => (int) $row['deleted_at'],
+			];
+		}, $raw);
+	}
+
 	/**
 	 * Returns a list of calendars for a principal.
 	 *
@@ -334,7 +377,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 				$calendar[$xmlName] = $row[$dbName];
 			}
 
-			$this->addOwnerPrincipal($calendar);
+			$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+			$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 			if (!isset($calendars[$calendar['id']])) {
 				$calendars[$calendar['id']] = $calendar;
@@ -410,7 +454,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 				$calendar[$xmlName] = $row[$dbName];
 			}
 
-			$this->addOwnerPrincipal($calendar);
+			$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+			$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 			$calendars[$calendar['id']] = $calendar;
 		}
@@ -458,7 +503,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 				$calendar[$xmlName] = $row[$dbName];
 			}
 
-			$this->addOwnerPrincipal($calendar);
+			$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+			$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 			if (!isset($calendars[$calendar['id']])) {
 				$calendars[$calendar['id']] = $calendar;
@@ -534,7 +580,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 				$calendar[$xmlName] = $row[$dbName];
 			}
 
-			$this->addOwnerPrincipal($calendar);
+			$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+			$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 			if (!isset($calendars[$calendar['id']])) {
 				$calendars[$calendar['id']] = $calendar;
@@ -601,7 +648,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			$calendar[$xmlName] = $row[$dbName];
 		}
 
-		$this->addOwnerPrincipal($calendar);
+		$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+		$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 		return $calendar;
 	}
@@ -654,7 +702,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			$calendar[$xmlName] = $row[$dbName];
 		}
 
-		$this->addOwnerPrincipal($calendar);
+		$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+		$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 		return $calendar;
 	}
@@ -705,7 +754,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			$calendar[$xmlName] = $row[$dbName];
 		}
 
-		$this->addOwnerPrincipal($calendar);
+		$calendar = $this->addOwnerPrincipalToCalendar($calendar);
+		$calendar = $this->addResourceTypeToCalendar($row, $calendar);
 
 		return $calendar;
 	}
@@ -872,33 +922,84 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 * @param mixed $calendarId
 	 * @return void
 	 */
-	public function deleteCalendar($calendarId) {
+	public function deleteCalendar($calendarId, bool $forceDeletePermanently = false) {
+		// The calendar is deleted right away if this is either enforced by the caller
+		// or the special contacts birthday calendar or when the preference of an empty
+		// retention (0 seconds) is set, which signals a disabled trashbin.
 		$calendarData = $this->getCalendarById($calendarId);
-		$shares = $this->getShares($calendarId);
+		$isBirthdayCalendar = isset($calendarData['uri']) && $calendarData['uri'] === BirthdayService::BIRTHDAY_CALENDAR_URI;
+		$trashbinDisabled = $this->config->getAppValue(Application::APP_ID, RetentionService::RETENTION_CONFIG_KEY) === '0';
+		if ($forceDeletePermanently || $isBirthdayCalendar || $trashbinDisabled) {
+			$calendarData = $this->getCalendarById($calendarId);
+			$shares = $this->getShares($calendarId);
 
-		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ? AND `calendartype` = ?');
+			$qbDeleteCalendarObjectProps = $this->db->getQueryBuilder();
-		$stmt->execute([$calendarId, self::CALENDAR_TYPE_CALENDAR]);
+			$qbDeleteCalendarObjectProps->delete($this->dbObjectPropertiesTable)
+				->where($qbDeleteCalendarObjectProps->expr()->eq('calendarid', $qbDeleteCalendarObjectProps->createNamedParameter($calendarId)))
+				->andWhere($qbDeleteCalendarObjectProps->expr()->eq('calendartype', $qbDeleteCalendarObjectProps->createNamedParameter(self::CALENDAR_TYPE_CALENDAR)))
+				->executeStatement();
 
-		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendars` WHERE `id` = ?');
+			$qbDeleteCalendarObjects = $this->db->getQueryBuilder();
-		$stmt->execute([$calendarId]);
+			$qbDeleteCalendarObjects->delete('calendarobjects')
+				->where($qbDeleteCalendarObjects->expr()->eq('calendarid', $qbDeleteCalendarObjects->createNamedParameter($calendarId)))
+				->andWhere($qbDeleteCalendarObjects->expr()->eq('calendartype', $qbDeleteCalendarObjects->createNamedParameter(self::CALENDAR_TYPE_CALENDAR)))
+				->executeStatement();
 
-		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarchanges` WHERE `calendarid` = ? AND `calendartype` = ?');
+			$qbDeleteCalendarChanges = $this->db->getQueryBuilder();
-		$stmt->execute([$calendarId, self::CALENDAR_TYPE_CALENDAR]);
+			$qbDeleteCalendarObjects->delete('calendarchanges')
+				->where($qbDeleteCalendarChanges->expr()->eq('calendarid', $qbDeleteCalendarChanges->createNamedParameter($calendarId)))
+				->andWhere($qbDeleteCalendarChanges->expr()->eq('calendartype', $qbDeleteCalendarChanges->createNamedParameter(self::CALENDAR_TYPE_CALENDAR)))
+				->executeStatement();
 
-		$this->calendarSharingBackend->deleteAllShares($calendarId);
+			$this->calendarSharingBackend->deleteAllShares($calendarId);
 
-		$query = $this->db->getQueryBuilder();
+			$qbDeleteCalendar = $this->db->getQueryBuilder();
-		$query->delete($this->dbObjectPropertiesTable)
+			$qbDeleteCalendarObjects->delete('calendars')
-			->where($query->expr()->eq('calendarid', $query->createNamedParameter($calendarId)))
+				->where($qbDeleteCalendar->expr()->eq('id', $qbDeleteCalendar->createNamedParameter($calendarId)))
-			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter(self::CALENDAR_TYPE_CALENDAR)))
+				->executeStatement();
-			->executeStatement();
 
-		// Only dispatch if we actually deleted anything
+			// Only dispatch if we actually deleted anything
-		if ($calendarData) {
+			if ($calendarData) {
-			$this->dispatcher->dispatchTyped(new CalendarDeletedEvent((int)$calendarId, $calendarData, $shares));
+				$this->dispatcher->dispatchTyped(new CalendarDeletedEvent((int)$calendarId, $calendarData, $shares));
+			}
+		} else {
+			$qbMarkCalendarDeleted = $this->db->getQueryBuilder();
+			$qbMarkCalendarDeleted->update('calendars')
+				->set('deleted_at', $qbMarkCalendarDeleted->createNamedParameter(time()))
+				->where($qbMarkCalendarDeleted->expr()->eq('id', $qbMarkCalendarDeleted->createNamedParameter($calendarId)))
+				->executeStatement();
+
+			$calendarData = $this->getCalendarById($calendarId);
+			$shares = $this->getShares($calendarId);
+			if ($calendarData) {
+				$this->dispatcher->dispatchTyped(new CalendarMovedToTrashEvent(
+					(int)$calendarId,
+					$calendarData,
+					$shares
+				));
+			}
 		}
 	}
 
+	public function restoreCalendar(int $id): void {
+		$qb = $this->db->getQueryBuilder();
+		$update = $qb->update('calendars')
+			->set('deleted_at', $qb->createNamedParameter(null))
+			->where($qb->expr()->eq('id', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT));
+		$update->executeStatement();
+
+		$calendarData = $this->getCalendarById($id);
+		$shares = $this->getShares($id);
+		if ($calendarData === null) {
+			throw new RuntimeException('Calendar data that was just written can\'t be read back. Check your database configuration.');
+		}
+		$this->dispatcher->dispatchTyped(new CalendarRestoredEvent(
+			$id,
+			$calendarData,
+			$shares
+		));
+	}
+
 	/**
 	 * Delete all of an user's shares
 	 *
@@ -946,7 +1047,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		$query->select(['id', 'uri', 'lastmodified', 'etag', 'calendarid', 'size', 'componenttype', 'classification'])
 			->from('calendarobjects')
 			->where($query->expr()->eq('calendarid', $query->createNamedParameter($calendarId)))
-			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter($calendarType)));
+			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter($calendarType)))
+			->andWhere($query->expr()->isNull('deleted_at'));
 		$stmt = $query->executeQuery();
 
 		$result = [];
@@ -967,6 +1069,63 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		return $result;
 	}
 
+	public function getDeletedCalendarObjects(int $deletedBefore): array {
+		$query = $this->db->getQueryBuilder();
+		$query->select(['co.id', 'co.uri', 'co.lastmodified', 'co.etag', 'co.calendarid', 'co.calendartype', 'co.size', 'co.componenttype', 'co.classification', 'co.deleted_at'])
+			->from('calendarobjects', 'co')
+			->join('co', 'calendars', 'c', $query->expr()->eq('c.id', 'co.calendarid', IQueryBuilder::PARAM_INT))
+			->where($query->expr()->isNotNull('co.deleted_at'))
+			->andWhere($query->expr()->lt('co.deleted_at', $query->createNamedParameter($deletedBefore)));
+		$stmt = $query->executeQuery();
+
+		$result = [];
+		foreach ($stmt->fetchAll() as $row) {
+			$result[] = [
+				'id' => $row['id'],
+				'uri' => $row['uri'],
+				'lastmodified' => $row['lastmodified'],
+				'etag' => '"' . $row['etag'] . '"',
+				'calendarid' => (int) $row['calendarid'],
+				'calendartype' => (int) $row['calendartype'],
+				'size' => (int) $row['size'],
+				'component' => strtolower($row['componenttype']),
+				'classification' => (int) $row['classification'],
+				'{' . \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD . '}deleted-at' => $row['deleted_at'],
+			];
+		}
+		$stmt->closeCursor();
+
+		return $result;
+	}
+
+	public function getDeletedCalendarObjectsByPrincipal(string $principalUri): array {
+		$query = $this->db->getQueryBuilder();
+		$query->select(['co.id', 'co.uri', 'co.lastmodified', 'co.etag', 'co.calendarid', 'co.size', 'co.componenttype', 'co.classification', 'co.deleted_at'])
+			->from('calendarobjects', 'co')
+			->join('co', 'calendars', 'c', $query->expr()->eq('c.id', 'co.calendarid', IQueryBuilder::PARAM_INT))
+			->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)))
+			->andWhere($query->expr()->isNotNull('co.deleted_at'));
+		$stmt = $query->executeQuery();
+
+		$result = [];
+		while ($row = $stmt->fetch()) {
+			$result[] = [
+				'id' => $row['id'],
+				'uri' => $row['uri'],
+				'lastmodified' => $row['lastmodified'],
+				'etag' => '"' . $row['etag'] . '"',
+				'calendarid' => $row['calendarid'],
+				'size' => (int)$row['size'],
+				'component' => strtolower($row['componenttype']),
+				'classification' => (int)$row['classification'],
+				'{' . \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD . '}deleted-at' => $row['deleted_at'],
+			];
+		}
+		$stmt->closeCursor();
+
+		return $result;
+	}
+
 	/**
 	 * Returns information from a single calendar object, based on it's object
 	 * uri.
@@ -984,7 +1143,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 * @param int $calendarType
 	 * @return array|null
 	 */
-	public function getCalendarObject($calendarId, $objectUri, $calendarType = self::CALENDAR_TYPE_CALENDAR) {
+	public function getCalendarObject($calendarId, $objectUri, int $calendarType = self::CALENDAR_TYPE_CALENDAR) {
 		$query = $this->db->getQueryBuilder();
 		$query->select(['id', 'uri', 'lastmodified', 'etag', 'calendarid', 'size', 'calendardata', 'componenttype', 'classification'])
 			->from('calendarobjects')
@@ -1038,7 +1197,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			->from('calendarobjects')
 			->where($query->expr()->eq('calendarid', $query->createNamedParameter($calendarId)))
 			->andWhere($query->expr()->in('uri', $query->createParameter('uri')))
-			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter($calendarType)));
+			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter($calendarType)))
+			->andWhere($query->expr()->isNull('deleted_at'));
 
 		foreach ($chunks as $uris) {
 			$query->setParameter('uri', $uris, IQueryBuilder::PARAM_STR_ARRAY);
@@ -1085,19 +1245,34 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	public function createCalendarObject($calendarId, $objectUri, $calendarData, $calendarType = self::CALENDAR_TYPE_CALENDAR) {
 		$extraData = $this->getDenormalizedData($calendarData);
 
-		$q = $this->db->getQueryBuilder();
+		// Try to detect duplicates
-		$q->select($q->func()->count('*'))
+		$qb = $this->db->getQueryBuilder();
+		$qb->select($qb->func()->count('*'))
 			->from('calendarobjects')
-			->where($q->expr()->eq('calendarid', $q->createNamedParameter($calendarId)))
+			->where($qb->expr()->eq('calendarid', $qb->createNamedParameter($calendarId)))
-			->andWhere($q->expr()->eq('uid', $q->createNamedParameter($extraData['uid'])))
+			->andWhere($qb->expr()->eq('uid', $qb->createNamedParameter($extraData['uid'])))
-			->andWhere($q->expr()->eq('calendartype', $q->createNamedParameter($calendarType)));
+			->andWhere($qb->expr()->eq('calendartype', $qb->createNamedParameter($calendarType)))
-
+			->andWhere($qb->expr()->isNull('deleted_at'));
-		$result = $q->executeQuery();
+		$result = $qb->executeQuery();
 		$count = (int) $result->fetchOne();
 		$result->closeCursor();
 
 		if ($count !== 0) {
-			throw new \Sabre\DAV\Exception\BadRequest('Calendar object with uid already exists in this calendar collection.');
+			throw new BadRequest('Calendar object with uid already exists in this calendar collection.');
+		}
+		// For a more specific error message we also try to explicitly look up the UID but as a deleted entry
+		$qbDel = $this->db->getQueryBuilder();
+		$qbDel->select($qb->func()->count('*'))
+			->from('calendarobjects')
+			->where($qbDel->expr()->eq('calendarid', $qbDel->createNamedParameter($calendarId)))
+			->andWhere($qbDel->expr()->eq('uid', $qbDel->createNamedParameter($extraData['uid'])))
+			->andWhere($qbDel->expr()->eq('calendartype', $qbDel->createNamedParameter($calendarType)))
+			->andWhere($qbDel->expr()->isNotNull('deleted_at'));
+		$result = $qbDel->executeQuery();
+		$count = (int) $result->fetchOne();
+		$result->closeCursor();
+		if ($count !== 0) {
+			throw new BadRequest('Deleted calendar object with uid already exists in this calendar collection.');
 		}
 
 		$query = $this->db->getQueryBuilder();
@@ -1236,11 +1411,23 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 * @param mixed $calendarId
 	 * @param string $objectUri
 	 * @param int $calendarType
+	 * @param bool $forceDeletePermanently
 	 * @return void
 	 */
-	public function deleteCalendarObject($calendarId, $objectUri, $calendarType = self::CALENDAR_TYPE_CALENDAR) {
+	public function deleteCalendarObject($calendarId, $objectUri, $calendarType = self::CALENDAR_TYPE_CALENDAR, bool $forceDeletePermanently = false) {
 		$data = $this->getCalendarObject($calendarId, $objectUri, $calendarType);
-		if (is_array($data)) {
+
+		if ($data === null) {
+			// Nothing to delete
+			return;
+		}
+
+		if ($forceDeletePermanently || $this->config->getAppValue(Application::APP_ID, RetentionService::RETENTION_CONFIG_KEY) === '0') {
+			$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ? AND `uri` = ? AND `calendartype` = ?');
+			$stmt->execute([$calendarId, $objectUri, $calendarType]);
+
+			$this->purgeProperties($calendarId, $data['id']);
+
 			if ($calendarType === self::CALENDAR_TYPE_CALENDAR) {
 				$calendarRow = $this->getCalendarById($calendarId);
 				$shares = $this->getShares($calendarId);
@@ -1260,18 +1447,107 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 					]
 				));
 			}
-		}
+		} else {
+			$pathInfo = pathinfo($data['uri']);
+			if (!empty($pathInfo['extension'])) {
+				// Append a suffix to "free" the old URI for recreation
+				$newUri = sprintf(
+					"%s-deleted.%s",
+					$pathInfo['filename'],
+					$pathInfo['extension']
+				);
+			} else {
+				$newUri = sprintf(
+					"%s-deleted",
+					$pathInfo['filename']
+				);
+			}
 
-		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ? AND `uri` = ? AND `calendartype` = ?');
+			// Try to detect conflicts before the DB does
-		$stmt->execute([$calendarId, $objectUri, $calendarType]);
+			// As unlikely as it seems, this can happen when the user imports, then deletes, imports and deletes again
+			$newObject = $this->getCalendarObject($calendarId, $newUri, $calendarType);
+			if ($newObject !== null) {
+				throw new Forbidden("A calendar object with URI $newUri already exists in calendar $calendarId, therefore this object can't be moved into the trashbin");
+			}
 
-		if (is_array($data)) {
+			$qb = $this->db->getQueryBuilder();
-			$this->purgeProperties($calendarId, $data['id'], $calendarType);
+			$markObjectDeletedQuery = $qb->update('calendarobjects')
+				->set('deleted_at', $qb->createNamedParameter(time(), IQueryBuilder::PARAM_INT))
+				->set('uri', $qb->createNamedParameter($newUri))
+				->where(
+					$qb->expr()->eq('calendarid', $qb->createNamedParameter($calendarId)),
+					$qb->expr()->eq('calendartype', $qb->createNamedParameter($calendarType, IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT),
+					$qb->expr()->eq('uri', $qb->createNamedParameter($objectUri))
+				);
+			$markObjectDeletedQuery->executeStatement();
+
+			$calendarData = $this->getCalendarById($calendarId);
+			if ($calendarData !== null) {
+				$this->dispatcher->dispatchTyped(
+					new CalendarObjectMovedToTrashEvent(
+						(int)$calendarId,
+						$calendarData,
+						$this->getShares($calendarId),
+						$data
+					)
+				);
+			}
 		}
 
 		$this->addChange($calendarId, $objectUri, 3, $calendarType);
 	}
 
+	/**
+	 * @param mixed $objectData
+	 *
+	 * @throws Forbidden
+	 */
+	public function restoreCalendarObject(array $objectData): void {
+		$id = (int) $objectData['id'];
+		$restoreUri = str_replace("-deleted.ics", ".ics", $objectData['uri']);
+		$targetObject = $this->getCalendarObject(
+			$objectData['calendarid'],
+			$restoreUri
+		);
+		if ($targetObject !== null) {
+			throw new Forbidden("Can not restore calendar $id because a calendar object with the URI $restoreUri already exists");
+		}
+
+		$qb = $this->db->getQueryBuilder();
+		$update = $qb->update('calendarobjects')
+			->set('uri', $qb->createNamedParameter($restoreUri))
+			->set('deleted_at', $qb->createNamedParameter(null))
+			->where($qb->expr()->eq('id', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT));
+		$update->executeStatement();
+
+		// Make sure this change is tracked in the changes table
+		$qb2 = $this->db->getQueryBuilder();
+		$selectObject = $qb2->select('calendardata', 'uri', 'calendarid', 'calendartype')
+			->from('calendarobjects')
+			->where($qb2->expr()->eq('id', $qb2->createNamedParameter($id, IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT));
+		$result = $selectObject->executeQuery();
+		$row = $result->fetch();
+		$result->closeCursor();
+		if ($row === false) {
+			// Welp, this should possibly not have happened, but let's ignore
+			return;
+		}
+		$this->addChange($row['calendarid'], $row['uri'], 1, (int) $row['calendartype']);
+
+		$calendarRow = $this->getCalendarById((int) $row['calendarid']);
+		if ($calendarRow === null) {
+			throw new RuntimeException('Calendar object data that was just written can\'t be read back. Check your database configuration.');
+		}
+		$this->dispatcher->dispatchTyped(
+			new CalendarObjectRestoredEvent(
+				(int) $objectData['calendarid'],
+				$calendarRow,
+				$this->getShares((int) $row['calendarid']),
+				$row
+			)
+		);
+	}
+
 	/**
 	 * Performs a calendar-query on the contents of this calendar.
 	 *
@@ -1359,7 +1635,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		$query->select($columns)
 			->from('calendarobjects')
 			->where($query->expr()->eq('calendarid', $query->createNamedParameter($calendarId)))
-			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter($calendarType)));
+			->andWhere($query->expr()->eq('calendartype', $query->createNamedParameter($calendarType)))
+			->andWhere($query->expr()->isNull('deleted_at'));
 
 		if ($componentType) {
 			$query->andWhere($query->expr()->eq('componenttype', $query->createNamedParameter($componentType)));
@@ -1508,7 +1785,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			->andWhere($compExpr)
 			->andWhere($propParamExpr)
 			->andWhere($query->expr()->iLike('i.value',
-				$query->createNamedParameter('%'.$this->db->escapeLikeParameter($filters['search-term']).'%')));
+				$query->createNamedParameter('%'.$this->db->escapeLikeParameter($filters['search-term']).'%')))
+			->andWhere($query->expr()->isNull('deleted_at'));
 
 		if ($offset) {
 			$query->setFirstResult($offset);
@@ -1574,7 +1852,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		}
 
 		$outerQuery->select('c.id', 'c.calendardata', 'c.componenttype', 'c.uid', 'c.uri')
-			->from('calendarobjects', 'c');
+			->from('calendarobjects', 'c')
+			->where($outerQuery->expr()->isNull('deleted_at'));
 
 		if (isset($options['timerange'])) {
 			if (isset($options['timerange']['start']) && $options['timerange']['start'] instanceof DateTime) {
@@ -1776,7 +2055,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			->leftJoin('cob', 'calendarobjects', 'co', $calendarObjectIdQuery->expr()->eq('co.id', 'cob.objectid'))
 			->andWhere($calendarObjectIdQuery->expr()->in('co.componenttype', $calendarObjectIdQuery->createNamedParameter($componentTypes, IQueryBuilder::PARAM_STR_ARRAY)))
 			->andWhere($calendarOr)
-			->andWhere($searchOr);
+			->andWhere($searchOr)
+			->andWhere($calendarObjectIdQuery->expr()->isNull('deleted_at'));
 
 		if ('' !== $pattern) {
 			if (!$escapePattern) {
@@ -1843,8 +2123,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			->from('calendarobjects', 'co')
 			->leftJoin('co', 'calendars', 'c', $query->expr()->eq('co.calendarid', 'c.id'))
 			->where($query->expr()->eq('c.principaluri', $query->createNamedParameter($principalUri)))
-			->andWhere($query->expr()->eq('co.uid', $query->createNamedParameter($uid)));
+			->andWhere($query->expr()->eq('co.uid', $query->createNamedParameter($uid)))
-
+			->andWhere($query->expr()->isNull('co.deleted_at'));
 		$stmt = $query->executeQuery();
 		$row = $stmt->fetch();
 		$stmt->closeCursor();
@@ -1855,6 +2135,35 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		return null;
 	}
 
+	public function getCalendarObjectById(string $principalUri, int $id): ?array {
+		$query = $this->db->getQueryBuilder();
+		$query->select(['co.id', 'co.uri', 'co.lastmodified', 'co.etag', 'co.calendarid', 'co.size', 'co.calendardata', 'co.componenttype', 'co.classification', 'co.deleted_at'])
+			->from('calendarobjects', 'co')
+			->join('co', 'calendars', 'c', $query->expr()->eq('c.id', 'co.calendarid', IQueryBuilder::PARAM_INT))
+			->where($query->expr()->eq('c.principaluri', $query->createNamedParameter($principalUri)))
+			->andWhere($query->expr()->eq('co.id', $query->createNamedParameter($id, IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT));
+		$stmt = $query->executeQuery();
+		$row = $stmt->fetch();
+		$stmt->closeCursor();
+
+		if (!$row) {
+			return null;
+		}
+
+		return [
+			'id' => $row['id'],
+			'uri' => $row['uri'],
+			'lastmodified' => $row['lastmodified'],
+			'etag' => '"' . $row['etag'] . '"',
+			'calendarid' => $row['calendarid'],
+			'size' => (int)$row['size'],
+			'calendardata' => $this->readBlob($row['calendardata']),
+			'component' => strtolower($row['componenttype']),
+			'classification' => (int)$row['classification'],
+			'deleted_at' => isset($row['deleted_at']) ? ((int) $row['deleted_at']) : null,
+		];
+	}
+
 	/**
 	 * The getChanges method returns all the changes that have happened, since
 	 * the specified syncToken in the specified calendar.
@@ -2410,7 +2719,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			}
 		}
 		if (!$componentType) {
-			throw new \Sabre\DAV\Exception\BadRequest('Calendar objects must have a VJOURNAL, VEVENT or VTODO component');
+			throw new BadRequest('Calendar objects must have a VJOURNAL, VEVENT or VTODO component');
 		}
 
 		if ($hasDTSTART) {
@@ -2670,7 +2979,10 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 
 		$ids = $result->fetchAll();
 		foreach ($ids as $id) {
-			$this->deleteCalendar($id['id']);
+			$this->deleteCalendar(
+				$id['id'],
+				true // No data to keep in the trashbin, if the user re-enables then we regenerate
+			);
 		}
 	}
 
@@ -2802,9 +3114,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	/**
 	 * adds information about an owner to the calendar data
 	 *
-	 * @param $calendarInfo
 	 */
-	private function addOwnerPrincipal(&$calendarInfo) {
+	private function addOwnerPrincipalToCalendar(array $calendarInfo): array {
 		$ownerPrincipalKey = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}owner-principal';
 		$displaynameKey = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD . '}owner-displayname';
 		if (isset($calendarInfo[$ownerPrincipalKey])) {
@@ -2817,5 +3128,20 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		if (isset($principalInformation['{DAV:}displayname'])) {
 			$calendarInfo[$displaynameKey] = $principalInformation['{DAV:}displayname'];
 		}
+		return $calendarInfo;
+	}
+
+	private function addResourceTypeToCalendar(array $row, array $calendar): array {
+		if (isset($row['deleted_at'])) {
+			// Columns is set and not null -> this is a deleted calendar
+			// we send a custom resourcetype to hide the deleted calendar
+			// from ordinary DAV clients, but the Calendar app will know
+			// how to handle this special resource.
+			$calendar['{DAV:}resourcetype'] = new DAV\Xml\Property\ResourceType([
+				'{DAV:}collection',
+				sprintf('{%s}deleted-calendar', \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD),
+			]);
+		}
+		return $calendar;
 	}
 }

apps/dav/lib/CalDAV/Calendar.php

@@ -42,9 +42,9 @@ use Sabre\DAV\PropPatch;
  * Class Calendar
  *
  * @package OCA\DAV\CalDAV
- * @property BackendInterface|CalDavBackend $caldavBackend
+ * @property CalDavBackend $caldavBackend
  */
-class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
+class Calendar extends \Sabre\CalDAV\Calendar implements IRestorable, IShareable {
 
 	/** @var IConfig */
 	private $config;
@@ -52,6 +52,9 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 	/** @var IL10N */
 	protected $l10n;
 
+	/** @var bool */
+	private $useTrashbin = true;
+
 	/**
 	 * Calendar constructor.
 	 *
@@ -269,7 +272,10 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 			$this->config->setUserValue($userId, 'dav', 'generateBirthdayCalendar', 'no');
 		}
 
-		parent::delete();
+		$this->caldavBackend->deleteCalendar(
+			$this->calendarInfo['id'],
+			!$this->useTrashbin
+		);
 	}
 
 	public function propPatch(PropPatch $propPatch) {
@@ -399,4 +405,12 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 
 		return parent::getChanges($syncToken, $syncLevel, $limit);
 	}
+
+	public function restore(): void {
+		$this->caldavBackend->restoreCalendar((int) $this->calendarInfo['id']);
+	}
+
+	public function disableTrashbin(): void {
+		$this->useTrashbin = false;
+	}
 }

apps/dav/lib/CalDAV/CalendarHome.php

@@ -30,6 +30,7 @@ namespace OCA\DAV\CalDAV;
 use OCA\DAV\AppInfo\PluginManager;
 use OCA\DAV\CalDAV\Integration\ExternalCalendar;
 use OCA\DAV\CalDAV\Integration\ICalendarProvider;
+use OCA\DAV\CalDAV\Trashbin\TrashbinHome;
 use Sabre\CalDAV\Backend\BackendInterface;
 use Sabre\CalDAV\Backend\NotificationSupport;
 use Sabre\CalDAV\Backend\SchedulingSupport;
@@ -38,6 +39,7 @@ use Sabre\CalDAV\Schedule\Inbox;
 use Sabre\CalDAV\Subscriptions\Subscription;
 use Sabre\DAV\Exception\MethodNotAllowed;
 use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\INode;
 use Sabre\DAV\MkCol;
 
 class CalendarHome extends \Sabre\CalDAV\CalendarHome {
@@ -74,8 +76,11 @@ class CalendarHome extends \Sabre\CalDAV\CalendarHome {
 	/**
 	 * @inheritdoc
 	 */
-	public function createExtendedCollection($name, MkCol $mkCol) {
+	public function createExtendedCollection($name, MkCol $mkCol): void {
-		$reservedNames = [BirthdayService::BIRTHDAY_CALENDAR_URI];
+		$reservedNames = [
+			BirthdayService::BIRTHDAY_CALENDAR_URI,
+			TrashbinHome::NAME,
+		];
 
 		if (\in_array($name, $reservedNames, true) || ExternalCalendar::doesViolateReservedName($name)) {
 			throw new MethodNotAllowed('The resource you tried to create has a reserved name');
@@ -104,6 +109,10 @@ class CalendarHome extends \Sabre\CalDAV\CalendarHome {
 			$objects[] = new \Sabre\CalDAV\Notifications\Collection($this->caldavBackend, $this->principalInfo['uri']);
 		}
 
+		if ($this->caldavBackend instanceof CalDavBackend) {
+			$objects[] = new TrashbinHome($this->caldavBackend, $this->principalInfo);
+		}
+
 		// If the backend supports subscriptions, we'll add those as well,
 		if ($this->caldavBackend instanceof SubscriptionSupport) {
 			foreach ($this->caldavBackend->getSubscriptionsForUser($this->principalInfo['uri']) as $subscription) {
@@ -127,7 +136,9 @@ class CalendarHome extends \Sabre\CalDAV\CalendarHome {
 	}
 
 	/**
-	 * @inheritdoc
+	 * @param string $name
+	 *
+	 * @return INode
 	 */
 	public function getChild($name) {
 		// Special nodes
@@ -140,6 +151,9 @@ class CalendarHome extends \Sabre\CalDAV\CalendarHome {
 		if ($name === 'notifications' && $this->caldavBackend instanceof NotificationSupport) {
 			return new \Sabre\CalDAV\Notifications\Collection($this->caldavBackend, $this->principalInfo['uri']);
 		}
+		if ($name === TrashbinHome::NAME && $this->caldavBackend instanceof CalDavBackend) {
+			return new TrashbinHome($this->caldavBackend, $this->principalInfo);
+		}
 
 		// Calendars
 		foreach ($this->caldavBackend->getCalendarsForUser($this->principalInfo['uri']) as $calendar) {

apps/dav/lib/CalDAV/CalendarObject.php

@@ -82,6 +82,10 @@ class CalendarObject extends \Sabre\CalDAV\CalendarObject {
 		return $vObject->serialize();
 	}
 
+	public function getId(): int {
+		return (int) $this->objectData['id'];
+	}
+
 	protected function isShared() {
 		if (!isset($this->calendarInfo['{http://owncloud.org/ns}owner-principal'])) {
 			return false;

apps/dav/lib/CalDAV/IRestorable.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV;
+
+use Sabre\DAV\Exception;
+
+/**
+ * Interface for nodes that can be restored from the trashbin
+ */
+interface IRestorable {
+
+	/**
+	 * Restore this node
+	 *
+	 * @throws Exception
+	 */
+	public function restore(): void;
+}

apps/dav/lib/CalDAV/RetentionService.php

@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV;
+
+use OCA\DAV\AppInfo\Application;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\IConfig;
+use function max;
+
+class RetentionService {
+	public const RETENTION_CONFIG_KEY = 'calendarRetentionObligation';
+	private const DEFAULT_RETENTION_SECONDS = 30 * 24 * 60 * 60;
+
+	/** @var IConfig */
+	private $config;
+
+	/** @var ITimeFactory */
+	private $time;
+
+	/** @var CalDavBackend */
+	private $calDavBackend;
+
+	public function __construct(IConfig $config,
+								ITimeFactory $time,
+								CalDavBackend $calDavBackend) {
+		$this->config = $config;
+		$this->time = $time;
+		$this->calDavBackend = $calDavBackend;
+	}
+
+	public function cleanUp(): void {
+		$retentionTime = max(
+			(int) $this->config->getAppValue(
+				Application::APP_ID,
+				self::RETENTION_CONFIG_KEY,
+				(string) self::DEFAULT_RETENTION_SECONDS
+			),
+			0 // Just making sure we don't delete things in the future when a negative number is passed
+		);
+		$now = $this->time->getTime();
+
+		$calendars = $this->calDavBackend->getDeletedCalendars($now - $retentionTime);
+		foreach ($calendars as $calendar) {
+			$this->calDavBackend->deleteCalendar($calendar['id'], true);
+		}
+
+		$objects = $this->calDavBackend->getDeletedCalendarObjects($now - $retentionTime);
+		foreach ($objects as $object) {
+			$this->calDavBackend->deleteCalendarObject(
+				$object['calendarid'],
+				$object['uri'],
+				$object['calendartype'],
+				true
+			);
+		}
+	}
+}

apps/dav/lib/CalDAV/Trashbin/DeletedCalendarObject.php

@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV\Trashbin;
+
+use OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\CalDAV\IRestorable;
+use Sabre\CalDAV\ICalendarObject;
+use Sabre\DAV\Exception\Forbidden;
+
+class DeletedCalendarObject implements ICalendarObject, IRestorable {
+
+	/** @var string */
+	private $name;
+
+	/** @var mixed[] */
+	private $objectData;
+
+	/** @var CalDavBackend */
+	private $calDavBackend;
+
+	public function __construct(string $name,
+								array $objectData,
+								CalDavBackend $calDavBackend) {
+		$this->name = $name;
+		$this->objectData = $objectData;
+		$this->calDavBackend = $calDavBackend;
+	}
+
+	public function delete() {
+		throw new Forbidden();
+	}
+
+	public function getName() {
+		return $this->name;
+	}
+
+	public function setName($name) {
+		throw new Forbidden();
+	}
+
+	public function getLastModified() {
+		return 0;
+	}
+
+	public function put($data) {
+		throw new Forbidden();
+	}
+
+	public function get() {
+		return $this->objectData['calendardata'];
+	}
+
+	public function getContentType() {
+		$mime = 'text/calendar; charset=utf-8';
+		if (isset($this->objectData['component']) && $this->objectData['component']) {
+			$mime .= '; component='.$this->objectData['component'];
+		}
+
+		return $mime;
+	}
+
+	public function getETag() {
+		return $this->objectData['etag'];
+	}
+
+	public function getSize() {
+		return (int) $this->objectData['size'];
+	}
+
+	public function restore(): void {
+		$this->calDavBackend->restoreCalendarObject($this->objectData);
+	}
+}

apps/dav/lib/CalDAV/Trashbin/DeletedCalendarObjectsCollection.php

@@ -0,0 +1,131 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV\Trashbin;
+
+use OCA\DAV\CalDAV\CalDavBackend;
+use Sabre\CalDAV\ICalendarObjectContainer;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\Exception\NotImplemented;
+use function array_map;
+use function implode;
+use function preg_match;
+
+class DeletedCalendarObjectsCollection implements ICalendarObjectContainer {
+	public const NAME = 'objects';
+
+	/** @var CalDavBackend */
+	protected $caldavBackend;
+
+	/** @var mixed[] */
+	private $principalInfo;
+
+	public function __construct(CalDavBackend $caldavBackend,
+								array $principalInfo) {
+		$this->caldavBackend = $caldavBackend;
+		$this->principalInfo = $principalInfo;
+	}
+
+	/**
+	 * @see \OCA\DAV\CalDAV\Trashbin\DeletedCalendarObjectsCollection::calendarQuery
+	 */
+	public function getChildren() {
+		throw new NotImplemented();
+	}
+
+	public function getChild($name) {
+		if (!preg_match("/(\d+)\\.ics/", $name, $matches)) {
+			throw new NotFound();
+		}
+
+		$data = $this->caldavBackend->getCalendarObjectById(
+			$this->principalInfo['uri'],
+			(int) $matches[1],
+		);
+
+		// If the object hasn't been deleted yet then we don't want to find it here
+		if ($data === null) {
+			throw new NotFound();
+		}
+		if (!isset($data['deleted_at'])) {
+			throw new BadRequest('The calendar object you\'re trying to restore is not marked as deleted');
+		}
+
+		return new DeletedCalendarObject(
+			$this->getRelativeObjectPath($data),
+			$data,
+			$this->caldavBackend
+		);
+	}
+
+	public function createFile($name, $data = null) {
+		throw new Forbidden();
+	}
+
+	public function createDirectory($name) {
+		throw new Forbidden();
+	}
+
+	public function childExists($name) {
+		try {
+			$this->getChild($name);
+		} catch (NotFound $e) {
+			return false;
+		}
+
+		return true;
+	}
+
+	public function delete() {
+		throw new Forbidden();
+	}
+
+	public function getName(): string {
+		return self::NAME;
+	}
+
+	public function setName($name) {
+		throw new Forbidden();
+	}
+
+	public function getLastModified(): int {
+		return 0;
+	}
+
+	public function calendarQuery(array $filters) {
+		return array_map(function (array $calendarInfo) {
+			return $this->getRelativeObjectPath($calendarInfo);
+		}, $this->caldavBackend->getDeletedCalendarObjectsByPrincipal($this->principalInfo['uri']));
+	}
+
+	private function getRelativeObjectPath(array $calendarInfo): string {
+		return implode(
+			'.',
+			[$calendarInfo['id'], 'ics'],
+		);
+	}
+}

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

@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV\Trashbin;
+
+use OCA\DAV\CalDAV\Calendar;
+use OCP\IRequest;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+use function array_slice;
+use function implode;
+
+/**
+ * Conditional logic to bypass the calendar trashbin
+ */
+class Plugin extends ServerPlugin {
+
+	/** @var bool */
+	private $disableTrashbin;
+
+	/** @var Server */
+	private $server;
+
+	public function __construct(IRequest $request) {
+		$this->disableTrashbin = $request->getHeader('X-NC-CalDAV-No-Trashbin') === '1';
+	}
+
+	public function initialize(Server $server): void {
+		$this->server = $server;
+		$server->on('beforeMethod:*', [$this, 'beforeMethod']);
+	}
+
+	public function beforeMethod(RequestInterface $request, ResponseInterface $response): void {
+		if (!$this->disableTrashbin) {
+			return;
+		}
+
+		$path = $request->getPath();
+		$pathParts = explode('/', ltrim($path, '/'));
+		if (\count($pathParts) < 3) {
+			// We are looking for a path like calendars/username/calendarname
+			return;
+		}
+
+		// $calendarPath will look like calendars/username/calendarname
+		$calendarPath = implode(
+			'/',
+			array_slice($pathParts, 0, 3)
+		);
+		try {
+			$calendar = $this->server->tree->getNodeForPath($calendarPath);
+			if (!($calendar instanceof Calendar)) {
+				// This is odd
+				return;
+			}
+
+			/** @var Calendar $calendar */
+			$calendar->disableTrashbin();
+		} catch (NotFound $ex) {
+			return;
+		}
+	}
+
+	public function getFeatures(): array {
+		return ['nc-calendar-trashbin'];
+	}
+
+	public function getPluginName(): string {
+		return 'nc-calendar-trashbin';
+	}
+}

apps/dav/lib/CalDAV/Trashbin/RestoreTarget.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV\Trashbin;
+
+use OCA\DAV\CalDAV\IRestorable;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\ICollection;
+use Sabre\DAV\IMoveTarget;
+use Sabre\DAV\INode;
+
+class RestoreTarget implements ICollection, IMoveTarget {
+	public const NAME = 'restore';
+
+	public function createFile($name, $data = null) {
+		throw new Forbidden();
+	}
+
+	public function createDirectory($name) {
+		throw new Forbidden();
+	}
+
+	public function getChild($name) {
+		throw new NotFound();
+	}
+
+	public function getChildren(): array {
+		return [];
+	}
+
+	public function childExists($name): bool {
+		return false;
+	}
+
+	public function moveInto($targetName, $sourcePath, INode $sourceNode): bool {
+		if ($sourceNode instanceof IRestorable) {
+			$sourceNode->restore();
+			return true;
+		}
+
+		return false;
+	}
+
+	public function delete() {
+		throw new Forbidden();
+	}
+
+	public function getName(): string {
+		return 'restore';
+	}
+
+	public function setName($name) {
+		throw new Forbidden();
+	}
+
+	public function getLastModified() {
+		return 0;
+	}
+}

apps/dav/lib/CalDAV/Trashbin/TrashbinHome.php

@@ -0,0 +1,129 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\CalDAV\Trashbin;
+
+use OCA\DAV\CalDAV\CalDavBackend;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\ICollection;
+use Sabre\DAV\INode;
+use Sabre\DAV\IProperties;
+use Sabre\DAV\PropPatch;
+use Sabre\DAV\Xml\Property\ResourceType;
+use Sabre\DAVACL\ACLTrait;
+use Sabre\DAVACL\IACL;
+use function in_array;
+use function sprintf;
+
+class TrashbinHome implements IACL, ICollection, IProperties {
+	use ACLTrait;
+
+	public const NAME = 'trashbin';
+
+	/** @var CalDavBackend */
+	private $caldavBackend;
+
+	/** @var array */
+	private $principalInfo;
+
+	public function __construct(CalDavBackend $caldavBackend,
+								array $principalInfo) {
+		$this->caldavBackend = $caldavBackend;
+		$this->principalInfo = $principalInfo;
+	}
+
+	public function getOwner(): string {
+		return $this->principalInfo['uri'];
+	}
+
+	public function createFile($name, $data = null) {
+		throw new Forbidden('Permission denied to create files in the trashbin');
+	}
+
+	public function createDirectory($name) {
+		throw new Forbidden('Permission denied to create a directory in the trashbin');
+	}
+
+	public function getChild($name): INode {
+		switch ($name) {
+			case RestoreTarget::NAME:
+				return new RestoreTarget();
+			case DeletedCalendarObjectsCollection::NAME:
+				return new DeletedCalendarObjectsCollection(
+					$this->caldavBackend,
+					$this->principalInfo
+				);
+		}
+
+		throw new NotFound();
+	}
+
+	public function getChildren(): array {
+		return [
+			new RestoreTarget(),
+			new DeletedCalendarObjectsCollection(
+				$this->caldavBackend,
+				$this->principalInfo
+			),
+		];
+	}
+
+	public function childExists($name): bool {
+		return in_array($name, [
+			RestoreTarget::NAME,
+			DeletedCalendarObjectsCollection::NAME,
+		], true);
+	}
+
+	public function delete() {
+		throw new Forbidden('Permission denied to delete the trashbin');
+	}
+
+	public function getName(): string {
+		return self::NAME;
+	}
+
+	public function setName($name) {
+		throw new Forbidden('Permission denied to rename the trashbin');
+	}
+
+	public function getLastModified(): int {
+		return 0;
+	}
+
+	public function propPatch(PropPatch $propPatch): void {
+		throw new Forbidden('not implemented');
+	}
+
+	public function getProperties($properties): array {
+		return [
+			'{DAV:}resourcetype' => new ResourceType([
+				'{DAV:}collection',
+				sprintf('{%s}trash-bin', \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD),
+			]),
+		];
+	}
+}

apps/dav/lib/Command/CreateCalendar.php

@@ -32,6 +32,7 @@ use OCA\DAV\CalDAV\CalDavBackend;
 use OCA\DAV\CalDAV\Proxy\ProxyMapper;
 use OCA\DAV\Connector\Sabre\Principal;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\IUserManager;
@@ -94,9 +95,20 @@ class CreateCalendar extends Command {
 		$logger = \OC::$server->getLogger();
 		$dispatcher = \OC::$server->get(IEventDispatcher::class);
 		$legacyDispatcher = \OC::$server->getEventDispatcher();
+		$config = \OC::$server->get(IConfig::class);
 
 		$name = $input->getArgument('name');
-		$caldav = new CalDavBackend($this->dbConnection, $principalBackend, $this->userManager, $this->groupManager, $random, $logger, $dispatcher, $legacyDispatcher);
+		$caldav = new CalDavBackend(
+			$this->dbConnection,
+			$principalBackend,
+			$this->userManager,
+			$this->groupManager,
+			$random,
+			$logger,
+			$dispatcher,
+			$legacyDispatcher,
+			$config
+		);
 		$caldav->createCalendar("principals/users/$user", $name, []);
 		return 0;
 	}

apps/dav/lib/Command/RetentionCleanupCommand.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\Command;
+
+use OCA\DAV\CalDAV\RetentionService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class RetentionCleanupCommand extends Command {
+	/** @var RetentionService */
+	private $service;
+
+	public function __construct(RetentionService $service) {
+		parent::__construct('dav:retention:clean-up');
+
+		$this->service = $service;
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$this->service->cleanUp();
+
+		return 0;
+	}
+}

apps/dav/lib/Events/CalendarMovedToTrashEvent.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\Events;
+
+use OCP\EventDispatcher\Event;
+
+/**
+ * @since 22.0.0
+ */
+class CalendarMovedToTrashEvent extends Event {
+
+	/** @var int */
+	private $calendarId;
+
+	/** @var array */
+	private $calendarData;
+
+	/** @var array  */
+	private $shares;
+
+	/**
+	 * @param int $calendarId
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @since 22.0.0
+	 */
+	public function __construct(int $calendarId,
+								array $calendarData,
+								array $shares) {
+		parent::__construct();
+		$this->calendarId = $calendarId;
+		$this->calendarData = $calendarData;
+		$this->shares = $shares;
+	}
+
+	/**
+	 * @return int
+	 * @since 22.0.0
+	 */
+	public function getCalendarId(): int {
+		return $this->calendarId;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getCalendarData(): array {
+		return $this->calendarData;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getShares(): array {
+		return $this->shares;
+	}
+}

apps/dav/lib/Events/CalendarObjectMovedToTrashEvent.php

@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\Events;
+
+use OCP\EventDispatcher\Event;
+
+/**
+ * @since 22.0.0
+ */
+class CalendarObjectMovedToTrashEvent extends Event {
+
+	/** @var int */
+	private $calendarId;
+
+	/** @var array */
+	private $calendarData;
+
+	/** @var array */
+	private $shares;
+
+	/** @var array */
+	private $objectData;
+
+	/**
+	 * @param int $calendarId
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @param array $objectData
+	 * @since 22.0.0
+	 */
+	public function __construct(int $calendarId,
+								array $calendarData,
+								array $shares,
+								array $objectData) {
+		parent::__construct();
+		$this->calendarId = $calendarId;
+		$this->calendarData = $calendarData;
+		$this->shares = $shares;
+		$this->objectData = $objectData;
+	}
+
+	/**
+	 * @return int
+	 * @since 22.0.0
+	 */
+	public function getCalendarId(): int {
+		return $this->calendarId;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getCalendarData(): array {
+		return $this->calendarData;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getShares(): array {
+		return $this->shares;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getObjectData(): array {
+		return $this->objectData;
+	}
+}

apps/dav/lib/Events/CalendarObjectRestoredEvent.php

@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\Events;
+
+use OCP\EventDispatcher\Event;
+
+/**
+ * @since 22.0.0
+ */
+class CalendarObjectRestoredEvent extends Event {
+
+	/** @var int */
+	private $calendarId;
+
+	/** @var array */
+	private $calendarData;
+
+	/** @var array */
+	private $shares;
+
+	/** @var array */
+	private $objectData;
+
+	/**
+	 * @param int $calendarId
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @param array $objectData
+	 * @since 22.0.0
+	 */
+	public function __construct(int $calendarId,
+								array $calendarData,
+								array $shares,
+								array $objectData) {
+		parent::__construct();
+		$this->calendarId = $calendarId;
+		$this->calendarData = $calendarData;
+		$this->shares = $shares;
+		$this->objectData = $objectData;
+	}
+
+	/**
+	 * @return int
+	 * @since 22.0.0
+	 */
+	public function getCalendarId(): int {
+		return $this->calendarId;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getCalendarData(): array {
+		return $this->calendarData;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getShares(): array {
+		return $this->shares;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getObjectData(): array {
+		return $this->objectData;
+	}
+}

apps/dav/lib/Events/CalendarRestoredEvent.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * 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/>.
+ */
+
+namespace OCA\DAV\Events;
+
+use OCP\EventDispatcher\Event;
+
+/**
+ * @since 22.0.0
+ */
+class CalendarRestoredEvent extends Event {
+
+	/** @var int */
+	private $calendarId;
+
+	/** @var array */
+	private $calendarData;
+
+	/** @var array  */
+	private $shares;
+
+	/**
+	 * @param int $calendarId
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @since 22.0.0
+	 */
+	public function __construct(int $calendarId,
+								array $calendarData,
+								array $shares) {
+		parent::__construct();
+		$this->calendarId = $calendarId;
+		$this->calendarData = $calendarData;
+		$this->shares = $shares;
+	}
+
+	/**
+	 * @return int
+	 * @since 22.0.0
+	 */
+	public function getCalendarId(): int {
+		return $this->calendarId;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getCalendarData(): array {
+		return $this->calendarData;
+	}
+
+	/**
+	 * @return array
+	 * @since 22.0.0
+	 */
+	public function getShares(): array {
+		return $this->shares;
+	}
+}

apps/dav/lib/HookManager.php

@@ -128,7 +128,10 @@ class HookManager {
 		}
 
 		foreach ($this->calendarsToDelete as $calendar) {
-			$this->calDav->deleteCalendar($calendar['id']);
+			$this->calDav->deleteCalendar(
+				$calendar['id'],
+				true // Make sure the data doesn't go into the trashbin, a new user with the same UID would later see it otherwise
+			);
 		}
 		$this->calDav->deleteAllSharesByUser('principals/users/' . $uid);
 

apps/dav/lib/Listener/ActivityUpdaterListener.php

@@ -26,11 +26,16 @@ declare(strict_types=1);
 namespace OCA\DAV\Listener;
 
 use OCA\DAV\CalDAV\Activity\Backend as ActivityBackend;
+use OCA\DAV\DAV\Sharing\Plugin;
 use OCA\DAV\Events\CalendarCreatedEvent;
 use OCA\DAV\Events\CalendarDeletedEvent;
+use OCA\DAV\Events\CalendarMovedToTrashEvent;
 use OCA\DAV\Events\CalendarObjectCreatedEvent;
 use OCA\DAV\Events\CalendarObjectDeletedEvent;
+use OCA\DAV\Events\CalendarObjectMovedToTrashEvent;
+use OCA\DAV\Events\CalendarObjectRestoredEvent;
 use OCA\DAV\Events\CalendarObjectUpdatedEvent;
+use OCA\DAV\Events\CalendarRestoredEvent;
 use OCA\DAV\Events\CalendarUpdatedEvent;
 use OCP\EventDispatcher\Event;
 use OCP\EventDispatcher\IEventListener;
@@ -85,16 +90,55 @@ class ActivityUpdaterListener implements IEventListener {
 					'exception' => $e,
 				]);
 			}
-		} elseif ($event instanceof CalendarDeletedEvent) {
+		} elseif ($event instanceof CalendarMovedToTrashEvent) {
 			try {
-				$this->activityBackend->onCalendarDelete(
+				$this->activityBackend->onCalendarMovedToTrash(
 					$event->getCalendarData(),
 					$event->getShares()
 				);
 
 				$this->logger->debug(
-					sprintf('Activity generated for deleted calendar %d', $event->getCalendarId())
+					sprintf('Activity generated for changed calendar %d', $event->getCalendarId())
 				);
+			} catch (Throwable $e) {
+				// Any error with activities shouldn't abort the calendar update, so we just log it
+				$this->logger->error('Error generating activities for changed calendar: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
+		} elseif ($event instanceof CalendarRestoredEvent) {
+			try {
+				$this->activityBackend->onCalendarRestored(
+					$event->getCalendarData(),
+					$event->getShares()
+				);
+
+				$this->logger->debug(
+					sprintf('Activity generated for changed calendar %d', $event->getCalendarId())
+				);
+			} catch (Throwable $e) {
+				// Any error with activities shouldn't abort the calendar update, so we just log it
+				$this->logger->error('Error generating activities for changed calendar: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
+		} elseif ($event instanceof CalendarDeletedEvent) {
+			try {
+				$deletedProp = '{' . Plugin::NS_NEXTCLOUD . '}deleted-at';
+				if (isset($event->getCalendarData()[$deletedProp])) {
+					$this->logger->debug(
+						sprintf('Calendar %d was already in trashbin, skipping deletion activity', $event->getCalendarId())
+					);
+				} else {
+					$this->activityBackend->onCalendarDelete(
+						$event->getCalendarData(),
+						$event->getShares()
+					);
+
+					$this->logger->debug(
+						sprintf('Activity generated for deleted calendar %d', $event->getCalendarId())
+					);
+				}
 			} catch (Throwable $e) {
 				// Any error with activities shouldn't abort the calendar deletion, so we just log it
 				$this->logger->error('Error generating activities for a deleted calendar: ' . $e->getMessage(), [
@@ -137,18 +181,61 @@ class ActivityUpdaterListener implements IEventListener {
 					'exception' => $e,
 				]);
 			}
-		} elseif ($event instanceof CalendarObjectDeletedEvent) {
+		} elseif ($event instanceof CalendarObjectMovedToTrashEvent) {
 			try {
 				$this->activityBackend->onTouchCalendarObject(
-					\OCA\DAV\CalDAV\Activity\Provider\Event::SUBJECT_OBJECT_DELETE,
+					\OCA\DAV\CalDAV\Activity\Provider\Event::SUBJECT_OBJECT_MOVE_TO_TRASH,
 					$event->getCalendarData(),
 					$event->getShares(),
 					$event->getObjectData()
 				);
 
 				$this->logger->debug(
-					sprintf('Activity generated for deleted calendar object %d', $event->getCalendarId())
+					sprintf('Activity generated for a calendar object of calendar %d that is moved to trash', $event->getCalendarId())
 				);
+			} catch (Throwable $e) {
+				// Any error with activities shouldn't abort the calendar object creation, so we just log it
+				$this->logger->error('Error generating activity for a new calendar object: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
+		} elseif ($event instanceof CalendarObjectRestoredEvent) {
+			try {
+				$this->activityBackend->onTouchCalendarObject(
+					\OCA\DAV\CalDAV\Activity\Provider\Event::SUBJECT_OBJECT_RESTORE,
+					$event->getCalendarData(),
+					$event->getShares(),
+					$event->getObjectData()
+				);
+
+				$this->logger->debug(
+					sprintf('Activity generated for a restore calendar object of calendar %d', $event->getCalendarId())
+				);
+			} catch (Throwable $e) {
+				// Any error with activities shouldn't abort the calendar object restoration, so we just log it
+				$this->logger->error('Error generating activity for a restored calendar object: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
+		} elseif ($event instanceof CalendarObjectDeletedEvent) {
+			try {
+				$deletedProp = '{' . Plugin::NS_NEXTCLOUD . '}deleted-at';
+				if (isset($event->getObjectData()[$deletedProp])) {
+					$this->logger->debug(
+						sprintf('Calendar object in calendar %d was already in trashbin, skipping deletion activity', $event->getCalendarId())
+					);
+				} else {
+					$this->activityBackend->onTouchCalendarObject(
+						\OCA\DAV\CalDAV\Activity\Provider\Event::SUBJECT_OBJECT_DELETE,
+						$event->getCalendarData(),
+						$event->getShares(),
+						$event->getObjectData()
+					);
+
+					$this->logger->debug(
+						sprintf('Activity generated for deleted calendar object in calendar %d', $event->getCalendarId())
+					);
+				}
 			} catch (Throwable $e) {
 				// Any error with activities shouldn't abort the calendar deletion, so we just log it
 				$this->logger->error('Error generating activity for a deleted calendar object: ' . $e->getMessage(), [

apps/dav/lib/Listener/CalendarObjectReminderUpdaterListener.php

@@ -25,12 +25,17 @@ declare(strict_types=1);
 
 namespace OCA\DAV\Listener;
 
+use OCA\DAV\CalDAV\CalDavBackend;
 use OCA\DAV\CalDAV\Reminder\Backend as ReminderBackend;
 use OCA\DAV\CalDAV\Reminder\ReminderService;
 use OCA\DAV\Events\CalendarDeletedEvent;
+use OCA\DAV\Events\CalendarMovedToTrashEvent;
 use OCA\DAV\Events\CalendarObjectCreatedEvent;
 use OCA\DAV\Events\CalendarObjectDeletedEvent;
+use OCA\DAV\Events\CalendarObjectMovedToTrashEvent;
+use OCA\DAV\Events\CalendarObjectRestoredEvent;
 use OCA\DAV\Events\CalendarObjectUpdatedEvent;
+use OCA\DAV\Events\CalendarRestoredEvent;
 use OCP\EventDispatcher\Event;
 use OCP\EventDispatcher\IEventListener;
 use Psr\Log\LoggerInterface;
@@ -45,19 +50,39 @@ class CalendarObjectReminderUpdaterListener implements IEventListener {
 	/** @var ReminderService */
 	private $reminderService;
 
+	/** @var CalDavBackend */
+	private $calDavBackend;
+
 	/** @var LoggerInterface */
 	private $logger;
 
 	public function __construct(ReminderBackend $reminderBackend,
 								ReminderService $reminderService,
+								CalDavBackend $calDavBackend,
 								LoggerInterface $logger) {
 		$this->reminderBackend = $reminderBackend;
 		$this->reminderService = $reminderService;
+		$this->calDavBackend = $calDavBackend;
 		$this->logger = $logger;
 	}
 
 	public function handle(Event $event): void {
-		if ($event instanceof CalendarDeletedEvent) {
+		if ($event instanceof CalendarMovedToTrashEvent) {
+			try {
+				$this->reminderBackend->cleanRemindersForCalendar(
+					$event->getCalendarId()
+				);
+
+				$this->logger->debug(
+					sprintf('Reminders of calendar %d cleaned up after move into trashbin', $event->getCalendarId())
+				);
+			} catch (Throwable $e) {
+				// Any error with reminders shouldn't abort the calendar move, so we just log it
+				$this->logger->error('Error cleaning up reminders of a calendar moved into trashbin: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
+		} elseif ($event instanceof CalendarDeletedEvent) {
 			try {
 				$this->reminderBackend->cleanRemindersForCalendar(
 					$event->getCalendarId()
@@ -72,6 +97,27 @@ class CalendarObjectReminderUpdaterListener implements IEventListener {
 					'exception' => $e,
 				]);
 			}
+		} elseif ($event instanceof CalendarRestoredEvent) {
+			try {
+				$objects = $this->calDavBackend->getCalendarObjects($event->getCalendarId());
+				$this->logger->debug(sprintf('Restoring calendar reminder objects for %d items', count($objects)));
+				foreach ($objects as $object) {
+					$fullObject = $this->calDavBackend->getCalendarObject(
+						$event->getCalendarId(),
+						$object['uri']
+					);
+					$this->reminderService->onCalendarObjectCreate($fullObject);
+				}
+
+				$this->logger->debug(
+					sprintf('Reminders of calendar %d restored', $event->getCalendarId())
+				);
+			} catch (Throwable $e) {
+				// Any error with reminders shouldn't abort the calendar deletion, so we just log it
+				$this->logger->error('Error restoring reminders of a calendar: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
 		} elseif ($event instanceof CalendarObjectCreatedEvent) {
 			try {
 				$this->reminderService->onCalendarObjectCreate(
@@ -102,6 +148,36 @@ class CalendarObjectReminderUpdaterListener implements IEventListener {
 					'exception' => $e,
 				]);
 			}
+		} elseif ($event instanceof CalendarObjectMovedToTrashEvent) {
+			try {
+				$this->reminderService->onCalendarObjectDelete(
+					$event->getObjectData()
+				);
+
+				$this->logger->debug(
+					sprintf('Reminders of restored calendar object of calendar %d deleted', $event->getCalendarId())
+				);
+			} catch (Throwable $e) {
+				// Any error with reminders shouldn't abort the calendar object deletion, so we just log it
+				$this->logger->error('Error deleting reminders of a calendar object: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
+		} elseif ($event instanceof CalendarObjectRestoredEvent) {
+			try {
+				$this->reminderService->onCalendarObjectCreate(
+					$event->getObjectData()
+				);
+
+				$this->logger->debug(
+					sprintf('Reminders of restored calendar object of calendar %d restored', $event->getCalendarId())
+				);
+			} catch (Throwable $e) {
+				// Any error with reminders shouldn't abort the calendar object deletion, so we just log it
+				$this->logger->error('Error restoring reminders of a calendar object: ' . $e->getMessage(), [
+					'exception' => $e,
+				]);
+			}
 		} elseif ($event instanceof CalendarObjectDeletedEvent) {
 			try {
 				$this->reminderService->onCalendarObjectDelete(

apps/dav/lib/Migration/Version1018Date20210312100735.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\DAV\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\Types;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+class Version1018Date20210312100735 extends SimpleMigrationStep {
+
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return ISchemaWrapper
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		$calendarsTable = $schema->getTable('calendars');
+		$calendarsTable->addColumn('deleted_at', Types::INTEGER, [
+			'notnull' => false,
+			'length' => 4,
+			'unsigned' => true,
+		]);
+		$calendarsTable->addIndex([
+			'principaluri',
+			'deleted_at',
+		], 'cals_princ_del_idx');
+
+		$calendarObjectsTable = $schema->getTable('calendarobjects');
+		$calendarObjectsTable->addColumn('deleted_at', Types::INTEGER, [
+			'notnull' => false,
+			'length' => 4,
+			'unsigned' => true,
+		]);
+
+		return $schema;
+	}
+}

apps/dav/lib/RootCollection.php

@@ -47,6 +47,7 @@ use OCA\DAV\Upload\CleanupService;
 use OCP\App\IAppManager;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\IConfig;
 use Sabre\DAV\SimpleCollection;
 
 class RootCollection extends SimpleCollection {
@@ -62,6 +63,7 @@ class RootCollection extends SimpleCollection {
 		$db = \OC::$server->getDatabaseConnection();
 		$dispatcher = \OC::$server->get(IEventDispatcher::class);
 		$legacyDispatcher = \OC::$server->getEventDispatcher();
+		$config = \OC::$server->get(IConfig::class);
 		$proxyMapper = \OC::$server->query(ProxyMapper::class);
 
 		$userPrincipalBackend = new Principal(
@@ -95,15 +97,23 @@ class RootCollection extends SimpleCollection {
 
 		$filesCollection = new Files\RootCollection($userPrincipalBackend, 'principals/users');
 		$filesCollection->disableListing = $disableListing;
-		$caldavBackend = new CalDavBackend($db, $userPrincipalBackend, $userManager, $groupManager, $random, $logger, $dispatcher, $legacyDispatcher);
+		$caldavBackend = new CalDavBackend(
+			$db,
+			$userPrincipalBackend,
+			$userManager,
+			$groupManager,
+			$random,
+			$logger,
+			$dispatcher,
+			$legacyDispatcher,
+			$config
+		);
 		$userCalendarRoot = new CalendarRoot($userPrincipalBackend, $caldavBackend, 'principals/users');
 		$userCalendarRoot->disableListing = $disableListing;
 
-		$resourceCalendarCaldavBackend = new CalDavBackend($db, $userPrincipalBackend, $userManager, $groupManager, $random, $logger, $dispatcher, $legacyDispatcher);
 		$resourceCalendarRoot = new CalendarRoot($calendarResourcePrincipalBackend, $caldavBackend, 'principals/calendar-resources');
 		$resourceCalendarRoot->disableListing = $disableListing;
-		$roomCalendarCaldavBackend = new CalDavBackend($db, $userPrincipalBackend, $userManager, $groupManager, $random, $logger, $dispatcher, $legacyDispatcher);
+		$roomCalendarRoot = new CalendarRoot($calendarRoomPrincipalBackend, $caldavBackend, 'principals/calendar-rooms');
-		$roomCalendarRoot = new CalendarRoot($calendarRoomPrincipalBackend, $roomCalendarCaldavBackend, 'principals/calendar-rooms');
 		$roomCalendarRoot->disableListing = $disableListing;
 
 		$publicCalendarRoot = new PublicCalendarRoot($caldavBackend, $l10n, $config);

apps/dav/lib/Server.php

@@ -165,7 +165,8 @@ class Server {
 				$this->server->addPlugin(\OC::$server->query(\OCA\DAV\CalDAV\Schedule\IMipPlugin::class));
 			}
 
-			$this->server->addPlugin(new CalDAV\WebcalCaching\Plugin($request));
+			$this->server->addPlugin(new \OCA\DAV\CalDAV\Trashbin\Plugin($request));
+			$this->server->addPlugin(new \OCA\DAV\CalDAV\WebcalCaching\Plugin($request));
 			$this->server->addPlugin(new \Sabre\CalDAV\Subscriptions\Plugin());
 
 			$this->server->addPlugin(new \Sabre\CalDAV\Notifications\Plugin());

apps/dav/lib/SystemTag/SystemTagsObjectMappingCollection.php

@@ -115,20 +115,20 @@ class SystemTagsObjectMappingCollection implements ICollection {
 		throw new Forbidden('Permission denied to create collections');
 	}
 
-	public function getChild($tagId) {
+	public function getChild($tagName) {
 		try {
-			if ($this->tagMapper->haveTag([$this->objectId], $this->objectType, $tagId, true)) {
+			if ($this->tagMapper->haveTag([$this->objectId], $this->objectType, $tagName, true)) {
-				$tag = $this->tagManager->getTagsByIds([$tagId]);
+				$tag = $this->tagManager->getTagsByIds([$tagName]);
 				$tag = current($tag);
 				if ($this->tagManager->canUserSeeTag($tag, $this->user)) {
 					return $this->makeNode($tag);
 				}
 			}
-			throw new NotFound('Tag with id ' . $tagId . ' not present for object ' . $this->objectId);
+			throw new NotFound('Tag with id ' . $tagName . ' not present for object ' . $this->objectId);
 		} catch (\InvalidArgumentException $e) {
 			throw new BadRequest('Invalid tag id', 0, $e);
 		} catch (TagNotFoundException $e) {
-			throw new NotFound('Tag with id ' . $tagId . ' not found', 0, $e);
+			throw new NotFound('Tag with id ' . $tagName . ' not found', 0, $e);
 		}
 	}
 

apps/dav/lib/SystemTag/SystemTagsObjectTypeCollection.php

@@ -115,17 +115,18 @@ class SystemTagsObjectTypeCollection implements ICollection {
 	}
 
 	/**
-	 * @param string $objectId
+	 * @param string $objectName
+	 *
 	 * @return SystemTagsObjectMappingCollection
 	 * @throws NotFound
 	 */
-	public function getChild($objectId) {
+	public function getChild($objectName) {
 		// make sure the object exists and is reachable
-		if (!$this->childExists($objectId)) {
+		if (!$this->childExists($objectName)) {
 			throw new NotFound('Entity does not exist or is not available');
 		}
 		return new SystemTagsObjectMappingCollection(
-			$objectId,
+			$objectName,
 			$this->objectType,
 			$this->userSession->getUser(),
 			$this->tagManager,

apps/dav/tests/travis/caldav/install.sh

@@ -11,8 +11,12 @@ if [ ! -f pycalendar/setup.py ]; then
     git clone https://github.com/apple/ccs-pycalendar.git pycalendar
 fi
 
-# create test user
 cd "$SCRIPTPATH/../../../../../"
+
+# disable the trashbin, so recurrent deletion of the same object works
+php occ config:app:set dav calendarRetentionObligation --value=0
+
+# create test user
 OC_PASS=user01 php occ user:add --password-from-env user01
 php occ dav:create-calendar user01 calendar
 php occ dav:create-calendar user01 shared

apps/dav/tests/unit/CalDAV/AbstractCalDavBackend.php

@@ -113,7 +113,18 @@ abstract class AbstractCalDavBackend extends TestCase {
 		$db = \OC::$server->getDatabaseConnection();
 		$this->random = \OC::$server->getSecureRandom();
 		$this->logger = $this->createMock(ILogger::class);
-		$this->backend = new CalDavBackend($db, $this->principal, $this->userManager, $this->groupManager, $this->random, $this->logger, $this->dispatcher, $this->legacyDispatcher);
+		$this->config = $this->createMock(IConfig::class);
+		$this->backend = new CalDavBackend(
+			$db,
+			$this->principal,
+			$this->userManager,
+			$this->groupManager,
+			$this->random,
+			$this->logger,
+			$this->dispatcher,
+			$this->legacyDispatcher,
+			$this->config
+		);
 
 		$this->cleanUpBackend();
 	}
@@ -142,7 +153,7 @@ abstract class AbstractCalDavBackend extends TestCase {
 				return $event instanceof CalendarDeletedEvent;
 			}));
 		foreach ($calendars as $calendar) {
-			$this->backend->deleteCalendar($calendar['id']);
+			$this->backend->deleteCalendar($calendar['id'], true);
 		}
 		$subscriptions = $this->backend->getSubscriptionsForUser($principal);
 		foreach ($subscriptions as $subscription) {

apps/dav/tests/unit/CalDAV/CalDavBackendTest.php

@@ -83,7 +83,7 @@ class CalDavBackendTest extends AbstractCalDavBackend {
 			->with(self::callback(function ($event) {
 				return $event instanceof CalendarDeletedEvent;
 			}));
-		$this->backend->deleteCalendar($calendars[0]['id']);
+		$this->backend->deleteCalendar($calendars[0]['id'], true);
 		$calendars = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
 		self::assertEmpty($calendars);
 	}
@@ -212,7 +212,7 @@ EOD;
 			->with(self::callback(function ($event) {
 				return $event instanceof CalendarDeletedEvent;
 			}));
-		$this->backend->deleteCalendar($calendars[0]['id']);
+		$this->backend->deleteCalendar($calendars[0]['id'], true);
 		$calendars = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
 		self::assertEmpty($calendars);
 	}

apps/dav/tests/unit/CalDAV/CalendarHomeTest.php

@@ -32,6 +32,7 @@ use OCA\DAV\CalDAV\CalendarHome;
 use OCA\DAV\CalDAV\Integration\ExternalCalendar;
 use OCA\DAV\CalDAV\Integration\ICalendarProvider;
 use OCA\DAV\CalDAV\Outbox;
+use OCA\DAV\CalDAV\Trashbin\TrashbinHome;
 use Sabre\CalDAV\Schedule\Inbox;
 use Sabre\DAV\MkCol;
 use Test\TestCase;
@@ -141,13 +142,14 @@ class CalendarHomeTest extends TestCase {
 
 		$actual = $this->calendarHome->getChildren();
 
-		$this->assertCount(6, $actual);
+		$this->assertCount(7, $actual);
 		$this->assertInstanceOf(Inbox::class, $actual[0]);
 		$this->assertInstanceOf(Outbox::class, $actual[1]);
-		$this->assertEquals('plugin1calendar1', $actual[2]);
+		$this->assertInstanceOf(TrashbinHome::class, $actual[2]);
-		$this->assertEquals('plugin1calendar2', $actual[3]);
+		$this->assertEquals('plugin1calendar1', $actual[3]);
-		$this->assertEquals('plugin2calendar1', $actual[4]);
+		$this->assertEquals('plugin1calendar2', $actual[4]);
-		$this->assertEquals('plugin2calendar2', $actual[5]);
+		$this->assertEquals('plugin2calendar1', $actual[5]);
+		$this->assertEquals('plugin2calendar2', $actual[6]);
 	}
 
 	public function testGetChildNonAppGenerated():void {

apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php

@@ -86,6 +86,7 @@ class PublicCalendarRootTest extends TestCase {
 		$this->logger = $this->createMock(ILogger::class);
 		$dispatcher = $this->createMock(IEventDispatcher::class);
 		$legacyDispatcher = $this->createMock(EventDispatcherInterface::class);
+		$config = $this->createMock(IConfig::class);
 
 		$this->principal->expects($this->any())->method('getGroupMembership')
 			->withAnyParameters()
@@ -103,7 +104,8 @@ class PublicCalendarRootTest extends TestCase {
 			$this->random,
 			$this->logger,
 			$dispatcher,
-			$legacyDispatcher
+			$legacyDispatcher,
+			$config
 		);
 		$this->l10n = $this->getMockBuilder(IL10N::class)
 			->disableOriginalConstructor()->getMock();
@@ -129,7 +131,7 @@ class PublicCalendarRootTest extends TestCase {
 
 		$books = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
 		foreach ($books as $book) {
-			$this->backend->deleteCalendar($book['id']);
+			$this->backend->deleteCalendar($book['id'], true);
 		}
 	}
 

build/integration/features/bootstrap/CalDavContext.php

@@ -70,6 +70,9 @@ class CalDavContext implements \Behat\Behat\Context\Context {
 						'admin',
 						'admin',
 					],
+					'headers' => [
+						'X-NC-CalDAV-No-Trashbin' => '1',
+					]
 				]
 			);
 		} catch (\GuzzleHttp\Exception\ClientException $e) {

build/psalm-baseline.xml

@@ -163,11 +163,14 @@
   <file src="apps/dav/lib/CalDAV/CalDavBackend.php">
     <InvalidArgument occurrences="8">
       <code>'\OCA\DAV\CalDAV\CalDavBackend::createCachedCalendarObject'</code>
+
       <code>'\OCA\DAV\CalDAV\CalDavBackend::createSubscription'</code>
       <code>'\OCA\DAV\CalDAV\CalDavBackend::deleteCachedCalendarObject'</code>
+
       <code>'\OCA\DAV\CalDAV\CalDavBackend::deleteSubscription'</code>
       <code>'\OCA\DAV\CalDAV\CalDavBackend::publishCalendar'</code>
       <code>'\OCA\DAV\CalDAV\CalDavBackend::updateCachedCalendarObject'</code>
+
       <code>'\OCA\DAV\CalDAV\CalDavBackend::updateShares'</code>
       <code>'\OCA\DAV\CalDAV\CalDavBackend::updateSubscription'</code>
     </InvalidArgument>
@@ -186,7 +189,7 @@
     <RedundantCast occurrences="1">
       <code>(int)$calendarId</code>
     </RedundantCast>
-    <TooManyArguments occurrences="9">
+    <TooManyArguments occurrences="13">
       <code>dispatch</code>
       <code>dispatch</code>
       <code>dispatch</code>
@@ -200,7 +203,7 @@
       <code>dispatch</code>
       <code>dispatch</code>
       <code>dispatch</code>
-      <code>purgeProperties</code>
+
     </TooManyArguments>
     <UndefinedFunction occurrences="4">
       <code>Uri\split($principalUri)</code>
@@ -210,16 +213,13 @@
     </UndefinedFunction>
   </file>
   <file src="apps/dav/lib/CalDAV/CalendarHome.php">
-    <InvalidReturnStatement occurrences="5">
+    <InvalidNullableReturnType occurrences="1">
-      <code>$calendarPlugin-&gt;getCalendarInCalendarHome($this-&gt;principalInfo['uri'], $calendarUri)</code>
+      <code>INode</code>
-      <code>new Inbox($this-&gt;caldavBackend, $this-&gt;principalInfo['uri'])</code>
+    </InvalidNullableReturnType>
-      <code>new Outbox($this-&gt;config, $this-&gt;principalInfo['uri'])</code>
+    <LessSpecificImplementedReturnType occurrences="1">
-      <code>new Subscription($this-&gt;caldavBackend, $subscription)</code>
+      <code>INode</code>
-      <code>new \Sabre\CalDAV\Notifications\Collection($this-&gt;caldavBackend, $this-&gt;principalInfo['uri'])</code>
+    </LessSpecificImplementedReturnType>
-    </InvalidReturnStatement>
+
-    <InvalidReturnType occurrences="1">
-      <code>getChild</code>
-    </InvalidReturnType>
     <NullableReturnStatement occurrences="1">
       <code>$calendarPlugin-&gt;getCalendarInCalendarHome($this-&gt;principalInfo['uri'], $calendarUri)</code>
     </NullableReturnStatement>
@@ -5095,4 +5095,4 @@
       <code>$e-&gt;getCode()</code>
     </InvalidScalarArgument>
   </file>
-</files>
+</files>