1 files changed, 55 insertions, 0 deletions
diff --git a/apps/dav/lib/Connector/Sabre/PropFindPreloadNotifyPlugin.php b/apps/dav/lib/Connector/Sabre/PropFindPreloadNotifyPlugin.php
new file mode 100644
index 00000000000..c7b0c64132c
--- /dev/null
+++ b/apps/dav/lib/Connector/Sabre/PropFindPreloadNotifyPlugin.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types = 1);
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCA\DAV\Connector\Sabre;
+
+use Sabre\DAV\ICollection;
+use Sabre\DAV\INode;
+use Sabre\DAV\PropFind;
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+
+/**
+ * This plugin asks other plugins to preload data for a collection, so that
+ * subsequent PROPFIND handlers for children do not query the DB on a per-node
+ * basis.
+ */
+class PropFindPreloadNotifyPlugin extends ServerPlugin {
+
+	private Server $server;
+
+	public function initialize(Server $server): void {
+		$this->server = $server;
+		$this->server->on('propFind', [$this, 'collectionPreloadNotifier' ], 1);
+	}
+
+	/**
+	 * Uses the server instance to emit a `preloadCollection` event to signal
+	 * to interested plugins that a collection can be preloaded.
+	 *
+	 * NOTE: this can be emitted several times, so ideally every plugin
+	 * should cache what they need and check if a cache exists before
+	 * re-fetching.
+	 */
+	public function collectionPreloadNotifier(PropFind $propFind, INode $node): bool {
+		if (!$this->shouldPreload($propFind, $node)) {
+			return true;
+		}
+
+		return $this->server->emit('preloadCollection', [$propFind, $node]);
+	}
+
+	private function shouldPreload(
+		PropFind $propFind,
+		INode $node,
+	): bool {
+		$depth = $propFind->getDepth();
+		return $node instanceof ICollection
+			&& ($depth === Server::DEPTH_INFINITY || $depth > 0);
+	}
+}