better error for duplicate

lib/Album/AlbumMapper.php

@@ -23,6 +23,8 @@
 
 namespace OCA\Photos\Album;
 
+use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
+use OCA\Photos\Exception\AlreadyInAlbumException;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\Files\IMimeTypeLoader;
 use OCP\IDBConnection;
@@ -138,13 +140,17 @@ public function getForUserWithFiles(string $userId): array {
 	}
 
 	public function addFile(int $albumId, int $fileId): void {
-		$query = $this->connection->getQueryBuilder();
-		$query->insert("photos_albums_files")
-			->values([
-				"album_id" => $query->createNamedParameter($albumId, IQueryBuilder::PARAM_INT),
-				"file_id" => $query->createNamedParameter($fileId, IQueryBuilder::PARAM_INT)
-			]);
-		$query->executeStatement();
+		try {
+			$query = $this->connection->getQueryBuilder();
+			$query->insert("photos_albums_files")
+				->values([
+					"album_id" => $query->createNamedParameter($albumId, IQueryBuilder::PARAM_INT),
+					"file_id" => $query->createNamedParameter($fileId, IQueryBuilder::PARAM_INT)
+				]);
+			$query->executeStatement();
+		} catch (UniqueConstraintViolationException $e) {
+			throw new AlreadyInAlbumException("File already in album", 0, $e);
+		}
 	}
 
 	public function removeFile(int $albumId, int $fileId): void {

lib/Exception/AlreadyInAlbumException.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Robin Appelman <robin@icewind.nl>
+ *
+ * @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\Photos\Exception;
+
+class AlreadyInAlbumException extends \Exception {
+
+}