Add proper comment offset support

The offset is based on the last known comment instead of limit-offset,
so new comments don't mess up requests which get the history of an object-

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/private/Comments/Manager.php

@@ -376,6 +376,121 @@ class Manager implements ICommentsManager {
 		return $comments;
 	}
 
+	/**
+	 * @param string $objectType
+	 * @param string $objectId
+	 * @param int $lastKnownCommentId
+	 * @param string $sortDirection
+	 * @param int $limit
+	 * @return array
+	 */
+	public function getForObjectSince(
+		string $objectType,
+		string $objectId,
+		int $lastKnownCommentId,
+		string $sortDirection = 'asc',
+		int $limit = 30
+	): array {
+		$comments = [];
+
+		$query = $this->dbConn->getQueryBuilder();
+		$query->select('*')
+			->from('comments')
+			->where($query->expr()->eq('object_type', $query->createNamedParameter($objectType)))
+			->andWhere($query->expr()->eq('object_id', $query->createNamedParameter($objectId)))
+			->orderBy('creation_timestamp', $sortDirection === 'desc' ? 'DESC' : 'ASC')
+			->addOrderBy('id', $sortDirection === 'desc' ? 'DESC' : 'ASC');
+
+		if ($limit > 0) {
+			$query->setMaxResults($limit);
+		}
+
+		$lastKnownComment = $this->getLastKnownComment(
+			$objectType,
+			$objectId,
+			$lastKnownCommentId
+		);
+		if ($lastKnownComment instanceof IComment) {
+			$lastKnownCommentDateTime = $lastKnownComment->getCreationDateTime();
+			if ($sortDirection === 'desc') {
+				$query->andWhere(
+					$query->expr()->orX(
+						$query->expr()->lt(
+							'creation_timestamp',
+							$query->createNamedParameter($lastKnownCommentDateTime, IQueryBuilder::PARAM_DATE),
+							IQueryBuilder::PARAM_DATE
+						),
+						$query->expr()->andX(
+							$query->expr()->eq(
+								'creation_timestamp',
+								$query->createNamedParameter($lastKnownCommentDateTime, IQueryBuilder::PARAM_DATE),
+								IQueryBuilder::PARAM_DATE
+							),
+							$query->expr()->lt('id', $query->createNamedParameter($lastKnownCommentId))
+						)
+					)
+				);
+			} else {
+				$query->andWhere(
+					$query->expr()->orX(
+						$query->expr()->gt(
+							'creation_timestamp',
+							$query->createNamedParameter($lastKnownCommentDateTime, IQueryBuilder::PARAM_DATE),
+							IQueryBuilder::PARAM_DATE
+						),
+						$query->expr()->andX(
+							$query->expr()->eq(
+								'creation_timestamp',
+								$query->createNamedParameter($lastKnownCommentDateTime, IQueryBuilder::PARAM_DATE),
+								IQueryBuilder::PARAM_DATE
+							),
+							$query->expr()->gt('id', $query->createNamedParameter($lastKnownCommentId))
+						)
+					)
+				);
+			}
+		}
+
+		$resultStatement = $query->execute();
+		while ($data = $resultStatement->fetch()) {
+			$comment = new Comment($this->normalizeDatabaseData($data));
+			$this->cache($comment);
+			$comments[] = $comment;
+		}
+		$resultStatement->closeCursor();
+
+		return $comments;
+	}
+
+	/**
+	 * @param string $objectType
+	 * @param string $objectId
+	 * @param int $id
+	 * @return Comment|null
+	 */
+	protected function getLastKnownComment(string $objectType,
+										   string $objectId,
+										   int $id) {
+		$query = $this->dbConn->getQueryBuilder();
+		$query->select('*')
+			->from('comments')
+			->where($query->expr()->eq('object_type', $query->createNamedParameter($objectType)))
+			->andWhere($query->expr()->eq('object_id', $query->createNamedParameter($objectId)))
+			->andWhere($query->expr()->eq('id', $query->createNamedParameter($id, IQueryBuilder::PARAM_INT)));
+
+		$result = $query->execute();
+		$row = $result->fetch();
+		$result->closeCursor();
+
+		if ($row) {
+			$comment = new Comment($this->normalizeDatabaseData($row));
+			$this->cache($comment);
+			return $comment;
+		}
+
+		return null;
+	}
+
 	/**
 	 * @param $objectType string the object type, e.g. 'files'
 	 * @param $objectId string the id of the object

lib/public/Comments/ICommentsManager.php

@@ -120,6 +120,23 @@ interface ICommentsManager {
 			\DateTime $notOlderThan = null
 	);
 
+	/**
+	 * @param string $objectType
+	 * @param string $objectId
+	 * @param int $lastKnownCommentId
+	 * @param string $sortDirection
+	 * @param int $limit
+	 * @return array
+	 * @since 14.0.0
+	 */
+	public function getForObjectSince(
+		string $objectType,
+		string $objectId,
+		int $lastKnownCommentId,
+		string $sortDirection = 'asc',
+		int $limit = 30
+	): array;
+
 	/**
 	 * @param $objectType string the object type, e.g. 'files'
 	 * @param $objectId string the id of the object

tests/lib/Comments/ManagerTest.php

@@ -354,6 +354,48 @@ class ManagerTest extends TestCase {
 		], $amount);
 	}
 
+	/**
+	 * @dataProvider dataGetForObjectSince
+	 * @param $lastKnown
+	 * @param $order
+	 * @param $limit
+	 * @param $resultFrom
+	 * @param $resultTo
+	 */
+	public function testGetForObjectSince($lastKnown, $order, $limit, $resultFrom, $resultTo) {
+		$ids = [];
+		$ids[] = $this->addDatabaseEntry(0, 0);
+		$ids[] = $this->addDatabaseEntry(0, 0);
+		$ids[] = $this->addDatabaseEntry(0, 0);
+		$ids[] = $this->addDatabaseEntry(0, 0);
+		$ids[] = $this->addDatabaseEntry(0, 0);
+
+		$manager = $this->getManager();
+		$comments = $manager->getForObjectSince('files', 'file64', ($lastKnown === null ? 0 : $ids[$lastKnown]), $order, $limit);
+
+		$expected = array_slice($ids, $resultFrom, $resultTo - $resultFrom + 1);
+		if ($order === 'desc') {
+			$expected = array_reverse($expected);
+		}
+
+		$this->assertSame($expected, array_map(function(IComment $c) {
+			return (int) $c->getId();
+		}, $comments));
+	}
+
+	public function dataGetForObjectSince() {
+		return [
+			[null, 'asc', 20, 0, 4],
+			[null, 'asc', 2, 0, 1],
+			[null, 'desc', 20, 0, 4],
+			[null, 'desc', 2, 3, 4],
+			[1, 'asc', 20, 2, 4],
+			[1, 'asc', 2, 2, 3],
+			[3, 'desc', 20, 0, 2],
+			[3, 'desc', 2, 1, 2],
+		];
+	}
+
 	public function invalidCreateArgsProvider() {
 		return [
 			['', 'aId-1', 'oType-1', 'oId-1'],