Move \OC\Comments to PSR-4

1 files changed, 753 insertions, 0 deletions

diff --git a/lib/private/Comments/Manager.php b/lib/private/Comments/Manager.php
new file mode 100644
index 00000000000..b986c8c51f9
--- /dev/null
+++ b/lib/private/Comments/Manager.php
@@ -0,0 +1,753 @@
+<?php
+/**
+ * @author Arthur Schiwon <blizzz@owncloud.com>
+ * @author Joas Schilling <nickvergessen@owncloud.com>
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * 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, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OC\Comments;
+
+use Doctrine\DBAL\Exception\DriverException;
+use OCP\Comments\CommentsEvent;
+use OCP\Comments\IComment;
+use OCP\Comments\ICommentsManager;
+use OCP\Comments\NotFoundException;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
+use OCP\IConfig;
+use OCP\ILogger;
+use OCP\IUser;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+
+class Manager implements ICommentsManager {
+
+	/** @var  IDBConnection */
+	protected $dbConn;
+
+	/** @var  ILogger */
+	protected $logger;
+
+	/** @var IConfig */
+	protected $config;
+
+	/** @var EventDispatcherInterface */
+	protected $dispatcher;
+
+	/** @var IComment[]  */
+	protected $commentsCache = [];
+
+	/**
+	 * Manager constructor.
+	 *
+	 * @param IDBConnection $dbConn
+	 * @param ILogger $logger
+	 * @param IConfig $config
+	 * @param EventDispatcherInterface $dispatcher
+	 */
+	public function __construct(
+		IDBConnection $dbConn,
+		ILogger $logger,
+		IConfig $config,
+		EventDispatcherInterface $dispatcher
+	) {
+		$this->dbConn = $dbConn;
+		$this->logger = $logger;
+		$this->config = $config;
+		$this->dispatcher = $dispatcher;
+	}
+
+	/**
+	 * converts data base data into PHP native, proper types as defined by
+	 * IComment interface.
+	 *
+	 * @param array $data
+	 * @return array
+	 */
+	protected function normalizeDatabaseData(array $data) {
+		$data['id'] = strval($data['id']);
+		$data['parent_id'] = strval($data['parent_id']);
+		$data['topmost_parent_id'] = strval($data['topmost_parent_id']);
+		$data['creation_timestamp'] = new \DateTime($data['creation_timestamp']);
+		if (!is_null($data['latest_child_timestamp'])) {
+			$data['latest_child_timestamp'] = new \DateTime($data['latest_child_timestamp']);
+		}
+		$data['children_count'] = intval($data['children_count']);
+		return $data;
+	}
+
+	/**
+	 * prepares a comment for an insert or update operation after making sure
+	 * all necessary fields have a value assigned.
+	 *
+	 * @param IComment $comment
+	 * @return IComment returns the same updated IComment instance as provided
+	 *                  by parameter for convenience
+	 * @throws \UnexpectedValueException
+	 */
+	protected function prepareCommentForDatabaseWrite(IComment $comment) {
+		if(    !$comment->getActorType()
+			|| !$comment->getActorId()
+			|| !$comment->getObjectType()
+			|| !$comment->getObjectId()
+			|| !$comment->getVerb()
+		) {
+			throw new \UnexpectedValueException('Actor, Object and Verb information must be provided for saving');
+		}
+
+		if($comment->getId() === '') {
+			$comment->setChildrenCount(0);
+			$comment->setLatestChildDateTime(new \DateTime('0000-00-00 00:00:00', new \DateTimeZone('UTC')));
+			$comment->setLatestChildDateTime(null);
+		}
+
+		if(is_null($comment->getCreationDateTime())) {
+			$comment->setCreationDateTime(new \DateTime());
+		}
+
+		if($comment->getParentId() !== '0') {
+			$comment->setTopmostParentId($this->determineTopmostParentId($comment->getParentId()));
+		} else {
+			$comment->setTopmostParentId('0');
+		}
+
+		$this->cache($comment);
+
+		return $comment;
+	}
+
+	/**
+	 * returns the topmost parent id of a given comment identified by ID
+	 *
+	 * @param string $id
+	 * @return string
+	 * @throws NotFoundException
+	 */
+	protected function determineTopmostParentId($id) {
+		$comment = $this->get($id);
+		if($comment->getParentId() === '0') {
+			return $comment->getId();
+		} else {
+			return $this->determineTopmostParentId($comment->getId());
+		}
+	}
+
+	/**
+	 * updates child information of a comment
+	 *
+	 * @param string	$id
+	 * @param \DateTime	$cDateTime	the date time of the most recent child
+	 * @throws NotFoundException
+	 */
+	protected function updateChildrenInformation($id, \DateTime $cDateTime) {
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->select($qb->createFunction('COUNT(`id`)'))
+				->from('comments')
+				->where($qb->expr()->eq('parent_id', $qb->createParameter('id')))
+				->setParameter('id', $id);
+
+		$resultStatement = $query->execute();
+		$data = $resultStatement->fetch(\PDO::FETCH_NUM);
+		$resultStatement->closeCursor();
+		$children = intval($data[0]);
+
+		$comment = $this->get($id);
+		$comment->setChildrenCount($children);
+		$comment->setLatestChildDateTime($cDateTime);
+		$this->save($comment);
+	}
+
+	/**
+	 * Tests whether actor or object type and id parameters are acceptable.
+	 * Throws exception if not.
+	 *
+	 * @param string $role
+	 * @param string $type
+	 * @param string $id
+	 * @throws \InvalidArgumentException
+	 */
+	protected function checkRoleParameters($role, $type, $id) {
+		if(
+			   !is_string($type) || empty($type)
+			|| !is_string($id) || empty($id)
+		) {
+			throw new \InvalidArgumentException($role . ' parameters must be string and not empty');
+		}
+	}
+
+	/**
+	 * run-time caches a comment
+	 *
+	 * @param IComment $comment
+	 */
+	protected function cache(IComment $comment) {
+		$id = $comment->getId();
+		if(empty($id)) {
+			return;
+		}
+		$this->commentsCache[strval($id)] = $comment;
+	}
+
+	/**
+	 * removes an entry from the comments run time cache
+	 *
+	 * @param mixed $id the comment's id
+	 */
+	protected function uncache($id) {
+		$id = strval($id);
+		if (isset($this->commentsCache[$id])) {
+			unset($this->commentsCache[$id]);
+		}
+	}
+
+	/**
+	 * returns a comment instance
+	 *
+	 * @param string $id the ID of the comment
+	 * @return IComment
+	 * @throws NotFoundException
+	 * @throws \InvalidArgumentException
+	 * @since 9.0.0
+	 */
+	public function get($id) {
+		if(intval($id) === 0) {
+			throw new \InvalidArgumentException('IDs must be translatable to a number in this implementation.');
+		}
+
+		if(isset($this->commentsCache[$id])) {
+			return $this->commentsCache[$id];
+		}
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$resultStatement = $qb->select('*')
+			->from('comments')
+			->where($qb->expr()->eq('id', $qb->createParameter('id')))
+			->setParameter('id', $id, IQueryBuilder::PARAM_INT)
+			->execute();
+
+		$data = $resultStatement->fetch();
+		$resultStatement->closeCursor();
+		if(!$data) {
+			throw new NotFoundException();
+		}
+
+		$comment = new Comment($this->normalizeDatabaseData($data));
+		$this->cache($comment);
+		return $comment;
+	}
+
+	/**
+	 * returns the comment specified by the id and all it's child comments.
+	 * At this point of time, we do only support one level depth.
+	 *
+	 * @param string $id
+	 * @param int $limit max number of entries to return, 0 returns all
+	 * @param int $offset the start entry
+	 * @return array
+	 * @since 9.0.0
+	 *
+	 * The return array looks like this
+	 * [
+	 *   'comment' => IComment, // root comment
+	 *   'replies' =>
+	 *   [
+	 *     0 =>
+	 *     [
+	 *       'comment' => IComment,
+	 *       'replies' => []
+	 *     ]
+	 *     1 =>
+	 *     [
+	 *       'comment' => IComment,
+	 *       'replies'=> []
+	 *     ],
+	 *     …
+	 *   ]
+	 * ]
+	 */
+	public function getTree($id, $limit = 0, $offset = 0) {
+		$tree = [];
+		$tree['comment'] = $this->get($id);
+		$tree['replies'] = [];
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->select('*')
+				->from('comments')
+				->where($qb->expr()->eq('topmost_parent_id', $qb->createParameter('id')))
+				->orderBy('creation_timestamp', 'DESC')
+				->setParameter('id', $id);
+
+		if($limit > 0) {
+			$query->setMaxResults($limit);
+		}
+		if($offset > 0) {
+			$query->setFirstResult($offset);
+		}
+
+		$resultStatement = $query->execute();
+		while($data = $resultStatement->fetch()) {
+			$comment = new Comment($this->normalizeDatabaseData($data));
+			$this->cache($comment);
+			$tree['replies'][] = [
+				'comment' => $comment,
+				'replies' => []
+			];
+		}
+		$resultStatement->closeCursor();
+
+		return $tree;
+	}
+
+	/**
+	 * returns comments for a specific object (e.g. a file).
+	 *
+	 * The sort order is always newest to oldest.
+	 *
+	 * @param string $objectType the object type, e.g. 'files'
+	 * @param string $objectId the id of the object
+	 * @param int $limit optional, number of maximum comments to be returned. if
+	 * not specified, all comments are returned.
+	 * @param int $offset optional, starting point
+	 * @param \DateTime $notOlderThan optional, timestamp of the oldest comments
+	 * that may be returned
+	 * @return IComment[]
+	 * @since 9.0.0
+	 */
+	public function getForObject(
+			$objectType,
+			$objectId,
+			$limit = 0,
+			$offset = 0,
+			\DateTime $notOlderThan = null
+	) {
+		$comments = [];
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->select('*')
+				->from('comments')
+				->where($qb->expr()->eq('object_type', $qb->createParameter('type')))
+				->andWhere($qb->expr()->eq('object_id', $qb->createParameter('id')))
+				->orderBy('creation_timestamp', 'DESC')
+				->setParameter('type', $objectType)
+				->setParameter('id', $objectId);
+
+		if($limit > 0) {
+			$query->setMaxResults($limit);
+		}
+		if($offset > 0) {
+			$query->setFirstResult($offset);
+		}
+		if(!is_null($notOlderThan)) {
+			$query
+				->andWhere($qb->expr()->gt('creation_timestamp', $qb->createParameter('notOlderThan')))
+				->setParameter('notOlderThan', $notOlderThan, 'datetime');
+		}
+
+		$resultStatement = $query->execute();
+		while($data = $resultStatement->fetch()) {
+			$comment = new Comment($this->normalizeDatabaseData($data));
+			$this->cache($comment);
+			$comments[] = $comment;
+		}
+		$resultStatement->closeCursor();
+
+		return $comments;
+	}
+
+	/**
+	 * @param $objectType string the object type, e.g. 'files'
+	 * @param $objectId string the id of the object
+	 * @param \DateTime $notOlderThan optional, timestamp of the oldest comments
+	 * that may be returned
+	 * @return Int
+	 * @since 9.0.0
+	 */
+	public function getNumberOfCommentsForObject($objectType, $objectId, \DateTime $notOlderThan = null) {
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->select($qb->createFunction('COUNT(`id`)'))
+				->from('comments')
+				->where($qb->expr()->eq('object_type', $qb->createParameter('type')))
+				->andWhere($qb->expr()->eq('object_id', $qb->createParameter('id')))
+				->setParameter('type', $objectType)
+				->setParameter('id', $objectId);
+
+		if(!is_null($notOlderThan)) {
+			$query
+				->andWhere($qb->expr()->gt('creation_timestamp', $qb->createParameter('notOlderThan')))
+				->setParameter('notOlderThan', $notOlderThan, 'datetime');
+		}
+
+		$resultStatement = $query->execute();
+		$data = $resultStatement->fetch(\PDO::FETCH_NUM);
+		$resultStatement->closeCursor();
+		return intval($data[0]);
+	}
+
+	/**
+	 * creates a new comment and returns it. At this point of time, it is not
+	 * saved in the used data storage. Use save() after setting other fields
+	 * of the comment (e.g. message or verb).
+	 *
+	 * @param string $actorType the actor type (e.g. 'users')
+	 * @param string $actorId a user id
+	 * @param string $objectType the object type the comment is attached to
+	 * @param string $objectId the object id the comment is attached to
+	 * @return IComment
+	 * @since 9.0.0
+	 */
+	public function create($actorType, $actorId, $objectType, $objectId) {
+		$comment = new Comment();
+		$comment
+			->setActor($actorType, $actorId)
+			->setObject($objectType, $objectId);
+		return $comment;
+	}
+
+	/**
+	 * permanently deletes the comment specified by the ID
+	 *
+	 * When the comment has child comments, their parent ID will be changed to
+	 * the parent ID of the item that is to be deleted.
+	 *
+	 * @param string $id
+	 * @return bool
+	 * @throws \InvalidArgumentException
+	 * @since 9.0.0
+	 */
+	public function delete($id) {
+		if(!is_string($id)) {
+			throw new \InvalidArgumentException('Parameter must be string');
+		}
+
+		try {
+			$comment = $this->get($id);
+		} catch (\Exception $e) {
+			// Ignore exceptions, we just don't fire a hook then
+			$comment = null;
+		}
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->delete('comments')
+			->where($qb->expr()->eq('id', $qb->createParameter('id')))
+			->setParameter('id', $id);
+
+		try {
+			$affectedRows = $query->execute();
+			$this->uncache($id);
+		} catch (DriverException $e) {
+			$this->logger->logException($e, ['app' => 'core_comments']);
+			return false;
+		}
+
+		if ($affectedRows > 0 && $comment instanceof IComment) {
+			$this->dispatcher->dispatch(CommentsEvent::EVENT_DELETE, new CommentsEvent(
+				CommentsEvent::EVENT_DELETE,
+				$comment
+			));
+		}
+
+		return ($affectedRows > 0);
+	}
+
+	/**
+	 * saves the comment permanently
+	 *
+	 * if the supplied comment has an empty ID, a new entry comment will be
+	 * saved and the instance updated with the new ID.
+	 *
+	 * Otherwise, an existing comment will be updated.
+	 *
+	 * Throws NotFoundException when a comment that is to be updated does not
+	 * exist anymore at this point of time.
+	 *
+	 * @param IComment $comment
+	 * @return bool
+	 * @throws NotFoundException
+	 * @since 9.0.0
+	 */
+	public function save(IComment $comment) {
+		if($this->prepareCommentForDatabaseWrite($comment)->getId() === '') {
+			$result = $this->insert($comment);
+		} else {
+			$result = $this->update($comment);
+		}
+
+		if($result && !!$comment->getParentId()) {
+			$this->updateChildrenInformation(
+					$comment->getParentId(),
+					$comment->getCreationDateTime()
+			);
+			$this->cache($comment);
+		}
+
+		return $result;
+	}
+
+	/**
+	 * inserts the provided comment in the database
+	 *
+	 * @param IComment $comment
+	 * @return bool
+	 */
+	protected function insert(IComment &$comment) {
+		$qb = $this->dbConn->getQueryBuilder();
+		$affectedRows = $qb
+			->insert('comments')
+			->values([
+				'parent_id'					=> $qb->createNamedParameter($comment->getParentId()),
+				'topmost_parent_id' 		=> $qb->createNamedParameter($comment->getTopmostParentId()),
+				'children_count' 			=> $qb->createNamedParameter($comment->getChildrenCount()),
+				'actor_type' 				=> $qb->createNamedParameter($comment->getActorType()),
+				'actor_id' 					=> $qb->createNamedParameter($comment->getActorId()),
+				'message' 					=> $qb->createNamedParameter($comment->getMessage()),
+				'verb' 						=> $qb->createNamedParameter($comment->getVerb()),
+				'creation_timestamp' 		=> $qb->createNamedParameter($comment->getCreationDateTime(), 'datetime'),
+				'latest_child_timestamp'	=> $qb->createNamedParameter($comment->getLatestChildDateTime(), 'datetime'),
+				'object_type' 				=> $qb->createNamedParameter($comment->getObjectType()),
+				'object_id' 				=> $qb->createNamedParameter($comment->getObjectId()),
+			])
+			->execute();
+
+		if ($affectedRows > 0) {
+			$comment->setId(strval($qb->getLastInsertId()));
+		}
+
+		$this->dispatcher->dispatch(CommentsEvent::EVENT_ADD, new CommentsEvent(
+			CommentsEvent::EVENT_ADD,
+			$comment
+		));
+
+		return $affectedRows > 0;
+	}
+
+	/**
+	 * updates a Comment data row
+	 *
+	 * @param IComment $comment
+	 * @return bool
+	 * @throws NotFoundException
+	 */
+	protected function update(IComment $comment) {
+		$qb = $this->dbConn->getQueryBuilder();
+		$affectedRows = $qb
+			->update('comments')
+				->set('parent_id',				$qb->createNamedParameter($comment->getParentId()))
+				->set('topmost_parent_id', 		$qb->createNamedParameter($comment->getTopmostParentId()))
+				->set('children_count',			$qb->createNamedParameter($comment->getChildrenCount()))
+				->set('actor_type', 			$qb->createNamedParameter($comment->getActorType()))
+				->set('actor_id', 				$qb->createNamedParameter($comment->getActorId()))
+				->set('message',				$qb->createNamedParameter($comment->getMessage()))
+				->set('verb',					$qb->createNamedParameter($comment->getVerb()))
+				->set('creation_timestamp',		$qb->createNamedParameter($comment->getCreationDateTime(), 'datetime'))
+				->set('latest_child_timestamp',	$qb->createNamedParameter($comment->getLatestChildDateTime(), 'datetime'))
+				->set('object_type',			$qb->createNamedParameter($comment->getObjectType()))
+				->set('object_id',				$qb->createNamedParameter($comment->getObjectId()))
+			->where($qb->expr()->eq('id', $qb->createParameter('id')))
+			->setParameter('id', $comment->getId())
+			->execute();
+
+		if($affectedRows === 0) {
+			throw new NotFoundException('Comment to update does ceased to exist');
+		}
+
+		$this->dispatcher->dispatch(CommentsEvent::EVENT_UPDATE, new CommentsEvent(
+			CommentsEvent::EVENT_UPDATE,
+			$comment
+		));
+
+		return $affectedRows > 0;
+	}
+
+	/**
+	 * removes references to specific actor (e.g. on user delete) of a comment.
+	 * The comment itself must not get lost/deleted.
+	 *
+	 * @param string $actorType the actor type (e.g. 'users')
+	 * @param string $actorId a user id
+	 * @return boolean
+	 * @since 9.0.0
+	 */
+	public function deleteReferencesOfActor($actorType, $actorId) {
+		$this->checkRoleParameters('Actor', $actorType, $actorId);
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$affectedRows = $qb
+			->update('comments')
+			->set('actor_type',	$qb->createNamedParameter(ICommentsManager::DELETED_USER))
+			->set('actor_id',	$qb->createNamedParameter(ICommentsManager::DELETED_USER))
+			->where($qb->expr()->eq('actor_type', $qb->createParameter('type')))
+			->andWhere($qb->expr()->eq('actor_id', $qb->createParameter('id')))
+			->setParameter('type', $actorType)
+			->setParameter('id', $actorId)
+			->execute();
+
+		$this->commentsCache = [];
+
+		return is_int($affectedRows);
+	}
+
+	/**
+	 * deletes all comments made of a specific object (e.g. on file delete)
+	 *
+	 * @param string $objectType the object type (e.g. 'files')
+	 * @param string $objectId e.g. the file id
+	 * @return boolean
+	 * @since 9.0.0
+	 */
+	public function deleteCommentsAtObject($objectType, $objectId) {
+		$this->checkRoleParameters('Object', $objectType, $objectId);
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$affectedRows = $qb
+			->delete('comments')
+			->where($qb->expr()->eq('object_type', $qb->createParameter('type')))
+			->andWhere($qb->expr()->eq('object_id', $qb->createParameter('id')))
+			->setParameter('type', $objectType)
+			->setParameter('id', $objectId)
+			->execute();
+
+		$this->commentsCache = [];
+
+		return is_int($affectedRows);
+	}
+
+	/**
+	 * deletes the read markers for the specified user
+	 *
+	 * @param \OCP\IUser $user
+	 * @return bool
+	 * @since 9.0.0
+	 */
+	public function deleteReadMarksFromUser(IUser $user) {
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->delete('comments_read_markers')
+			->where($qb->expr()->eq('user_id', $qb->createParameter('user_id')))
+			->setParameter('user_id', $user->getUID());
+
+		try {
+			$affectedRows = $query->execute();
+		} catch (DriverException $e) {
+			$this->logger->logException($e, ['app' => 'core_comments']);
+			return false;
+		}
+		return ($affectedRows > 0);
+	}
+
+	/**
+	 * sets the read marker for a given file to the specified date for the
+	 * provided user
+	 *
+	 * @param string $objectType
+	 * @param string $objectId
+	 * @param \DateTime $dateTime
+	 * @param IUser $user
+	 * @since 9.0.0
+	 */
+	public function setReadMark($objectType, $objectId, \DateTime $dateTime, IUser $user) {
+		$this->checkRoleParameters('Object', $objectType, $objectId);
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$values = [
+			'user_id'         => $qb->createNamedParameter($user->getUID()),
+			'marker_datetime' => $qb->createNamedParameter($dateTime, 'datetime'),
+			'object_type'     => $qb->createNamedParameter($objectType),
+			'object_id'       => $qb->createNamedParameter($objectId),
+		];
+
+		// Strategy: try to update, if this does not return affected rows, do an insert.
+		$affectedRows = $qb
+			->update('comments_read_markers')
+			->set('user_id',         $values['user_id'])
+			->set('marker_datetime', $values['marker_datetime'])
+			->set('object_type',     $values['object_type'])
+			->set('object_id',       $values['object_id'])
+			->where($qb->expr()->eq('user_id', $qb->createParameter('user_id')))
+			->andWhere($qb->expr()->eq('object_type', $qb->createParameter('object_type')))
+			->andWhere($qb->expr()->eq('object_id', $qb->createParameter('object_id')))
+			->setParameter('user_id', $user->getUID(), IQueryBuilder::PARAM_STR)
+			->setParameter('object_type', $objectType, IQueryBuilder::PARAM_STR)
+			->setParameter('object_id', $objectId, IQueryBuilder::PARAM_STR)
+			->execute();
+
+		if ($affectedRows > 0) {
+			return;
+		}
+
+		$qb->insert('comments_read_markers')
+			->values($values)
+			->execute();
+	}
+
+	/**
+	 * returns the read marker for a given file to the specified date for the
+	 * provided user. It returns null, when the marker is not present, i.e.
+	 * no comments were marked as read.
+	 *
+	 * @param string $objectType
+	 * @param string $objectId
+	 * @param IUser $user
+	 * @return \DateTime|null
+	 * @since 9.0.0
+	 */
+	public function getReadMark($objectType, $objectId, IUser $user) {
+		$qb = $this->dbConn->getQueryBuilder();
+		$resultStatement = $qb->select('marker_datetime')
+			->from('comments_read_markers')
+			->where($qb->expr()->eq('user_id', $qb->createParameter('user_id')))
+			->andWhere($qb->expr()->eq('object_type', $qb->createParameter('object_type')))
+			->andWhere($qb->expr()->eq('object_id', $qb->createParameter('object_id')))
+			->setParameter('user_id', $user->getUID(), IQueryBuilder::PARAM_STR)
+			->setParameter('object_type', $objectType, IQueryBuilder::PARAM_STR)
+			->setParameter('object_id', $objectId, IQueryBuilder::PARAM_STR)
+			->execute();
+
+		$data = $resultStatement->fetch();
+		$resultStatement->closeCursor();
+		if(!$data || is_null($data['marker_datetime'])) {
+			return null;
+		}
+
+		return new \DateTime($data['marker_datetime']);
+	}
+
+	/**
+	 * deletes the read markers on the specified object
+	 *
+	 * @param string $objectType
+	 * @param string $objectId
+	 * @return bool
+	 * @since 9.0.0
+	 */
+	public function deleteReadMarksOnObject($objectType, $objectId) {
+		$this->checkRoleParameters('Object', $objectType, $objectId);
+
+		$qb = $this->dbConn->getQueryBuilder();
+		$query = $qb->delete('comments_read_markers')
+			->where($qb->expr()->eq('object_type', $qb->createParameter('object_type')))
+			->andWhere($qb->expr()->eq('object_id', $qb->createParameter('object_id')))
+			->setParameter('object_type', $objectType)
+			->setParameter('object_id', $objectId);
+
+		try {
+			$affectedRows = $query->execute();
+		} catch (DriverException $e) {
+			$this->logger->logException($e, ['app' => 'core_comments']);
+			return false;
+		}
+		return ($affectedRows > 0);
+	}
+}