1 files changed, 59 insertions, 0 deletions
diff --git a/lib/private/EventDispatcher/ServiceEventListener.php b/lib/private/EventDispatcher/ServiceEventListener.php
new file mode 100644
index 00000000000..f9cc85b4126
--- /dev/null
+++ b/lib/private/EventDispatcher/ServiceEventListener.php
@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2019 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OC\EventDispatcher;
+
+use OCP\AppFramework\QueryException;
+use OCP\EventDispatcher\Event;
+use OCP\EventDispatcher\IEventListener;
+use Psr\Container\ContainerInterface;
+use Psr\Log\LoggerInterface;
+use function sprintf;
+
+/**
+ * Lazy service event listener
+ *
+ * Makes it possible to lazy-route a dispatched event to a service instance
+ * created by the service container
+ */
+final class ServiceEventListener {
+	private ?IEventListener $service = null;
+
+	public function __construct(
+		private ContainerInterface $container,
+		private string $class,
+		private LoggerInterface $logger,
+	) {
+	}
+
+	public function __invoke(Event $event) {
+		if ($this->service === null) {
+			try {
+				// TODO: fetch from the app containers, otherwise any custom services,
+				//       parameters and aliases won't be resolved.
+				//       See https://github.com/nextcloud/server/issues/27793 for details.
+				$this->service = $this->container->get($this->class);
+			} catch (QueryException $e) {
+				$this->logger->error(
+					sprintf(
+						'Could not load event listener service %s: %s. Make sure the class is auto-loadable by the Nextcloud server container',
+						$this->class,
+						$e->getMessage()
+					),
+					[
+						'exception' => $e,
+					]
+				);
+				return;
+			}
+		}
+
+		$this->service->handle($event);
+	}
+}