nextcloud / server

lib/private/TagManager.php

Indentation +52 added lines, -52 removed lines

@@ -46,62 +46,62 @@
 
 class TagManager implements ITagManager {
 
-	/** @var TagMapper */
-	private $mapper;
+    /** @var TagMapper */
+    private $mapper;
 
-	/** @var IUserSession */
-	private $userSession;
+    /** @var IUserSession */
+    private $userSession;
 
-	/** @var IDBConnection */
-	private $connection;
+    /** @var IDBConnection */
+    private $connection;
 
-	public function __construct(TagMapper $mapper, IUserSession $userSession, IDBConnection $connection) {
-		$this->mapper = $mapper;
-		$this->userSession = $userSession;
-		$this->connection = $connection;
-	}
+    public function __construct(TagMapper $mapper, IUserSession $userSession, IDBConnection $connection) {
+        $this->mapper = $mapper;
+        $this->userSession = $userSession;
+        $this->connection = $connection;
+    }
 
-	/**
-	 * Create a new \OCP\ITags instance and load tags from db.
-	 *
-	 * @see \OCP\ITags
-	 * @param string $type The type identifier e.g. 'contact' or 'event'.
-	 * @param array $defaultTags An array of default tags to be used if none are stored.
-	 * @param boolean $includeShared Whether to include tags for items shared with this user by others.
-	 * @param string $userId user for which to retrieve the tags, defaults to the currently
-	 * logged in user
-	 * @return \OCP\ITags
-	 *
-	 * since 20.0.0 $includeShared isn't used anymore
-	 */
-	public function load($type, $defaultTags = [], $includeShared = false, $userId = null) {
-		if (is_null($userId)) {
-			$user = $this->userSession->getUser();
-			if ($user === null) {
-				// nothing we can do without a user
-				return null;
-			}
-			$userId = $this->userSession->getUser()->getUId();
-		}
-		return new Tags($this->mapper, $userId, $type, $defaultTags);
-	}
+    /**
+     * Create a new \OCP\ITags instance and load tags from db.
+     *
+     * @see \OCP\ITags
+     * @param string $type The type identifier e.g. 'contact' or 'event'.
+     * @param array $defaultTags An array of default tags to be used if none are stored.
+     * @param boolean $includeShared Whether to include tags for items shared with this user by others.
+     * @param string $userId user for which to retrieve the tags, defaults to the currently
+     * logged in user
+     * @return \OCP\ITags
+     *
+     * since 20.0.0 $includeShared isn't used anymore
+     */
+    public function load($type, $defaultTags = [], $includeShared = false, $userId = null) {
+        if (is_null($userId)) {
+            $user = $this->userSession->getUser();
+            if ($user === null) {
+                // nothing we can do without a user
+                return null;
+            }
+            $userId = $this->userSession->getUser()->getUId();
+        }
+        return new Tags($this->mapper, $userId, $type, $defaultTags);
+    }
 
-	/**
-	 * Get all users who favorited an object
-	 *
-	 * @param string $objectType
-	 * @param int $objectId
-	 * @return array
-	 */
-	public function getUsersFavoritingObject(string $objectType, int $objectId): array {
-		$query = $this->connection->getQueryBuilder();
-		$query->select('uid')
-			->from('vcategory_to_object', 'o')
-			->innerJoin('o', 'vcategory', 'c', $query->expr()->eq('o.categoryid', 'c.id'))
-			->where($query->expr()->eq('objid', $query->createNamedParameter($objectId, IQueryBuilder::PARAM_INT)))
-			->andWhere($query->expr()->eq('c.type', $query->createNamedParameter($objectType)))
-			->andWhere($query->expr()->eq('c.category', $query->createNamedParameter(ITags::TAG_FAVORITE)));
+    /**
+     * Get all users who favorited an object
+     *
+     * @param string $objectType
+     * @param int $objectId
+     * @return array
+     */
+    public function getUsersFavoritingObject(string $objectType, int $objectId): array {
+        $query = $this->connection->getQueryBuilder();
+        $query->select('uid')
+            ->from('vcategory_to_object', 'o')
+            ->innerJoin('o', 'vcategory', 'c', $query->expr()->eq('o.categoryid', 'c.id'))
+            ->where($query->expr()->eq('objid', $query->createNamedParameter($objectId, IQueryBuilder::PARAM_INT)))
+            ->andWhere($query->expr()->eq('c.type', $query->createNamedParameter($objectType)))
+            ->andWhere($query->expr()->eq('c.category', $query->createNamedParameter(ITags::TAG_FAVORITE)));
 
-		return $query->execute()->fetchAll(\PDO::FETCH_COLUMN);
-	}
+        return $query->execute()->fetchAll(\PDO::FETCH_COLUMN);
+    }
 }

lib/private/Tags.php

Indentation +785 added lines, -785 removed lines

@@ -51,789 +51,789 @@
 
 class Tags implements ITags {
 
-	/**
-	 * Tags
-	 *
-	 * @var array
-	 */
-	private $tags = [];
-
-	/**
-	 * Used for storing objectid/categoryname pairs while rescanning.
-	 *
-	 * @var array
-	 */
-	private static $relations = [];
-
-	/**
-	 * Type
-	 *
-	 * @var string
-	 */
-	private $type;
-
-	/**
-	 * User
-	 *
-	 * @var string
-	 */
-	private $user;
-
-	/**
-	 * Are we including tags for shared items?
-	 *
-	 * @var bool
-	 */
-	private $includeShared = false;
-
-	/**
-	 * The current user, plus any owners of the items shared with the current
-	 * user, if $this->includeShared === true.
-	 *
-	 * @var array
-	 */
-	private $owners = [];
-
-	/**
-	 * The Mapper we're using to communicate our Tag objects to the database.
-	 *
-	 * @var TagMapper
-	 */
-	private $mapper;
-
-	/**
-	 * The sharing backend for objects of $this->type. Required if
-	 * $this->includeShared === true to determine ownership of items.
-	 *
-	 * @var \OCP\Share_Backend
-	 */
-	private $backend;
-
-	public const TAG_TABLE = '*PREFIX*vcategory';
-	public const RELATION_TABLE = '*PREFIX*vcategory_to_object';
-
-	/**
-	 * Constructor.
-	 *
-	 * @param TagMapper $mapper Instance of the TagMapper abstraction layer.
-	 * @param string $user The user whose data the object will operate on.
-	 * @param string $type The type of items for which tags will be loaded.
-	 * @param array $defaultTags Tags that should be created at construction.
-	 *
-	 * since 20.0.0 $includeShared isn't used anymore
-	 */
-	public function __construct(TagMapper $mapper, $user, $type, $defaultTags = []) {
-		$this->mapper = $mapper;
-		$this->user = $user;
-		$this->type = $type;
-		$this->owners = [$this->user];
-		$this->tags = $this->mapper->loadTags($this->owners, $this->type);
-
-		if (count($defaultTags) > 0 && count($this->tags) === 0) {
-			$this->addMultiple($defaultTags, true);
-		}
-	}
-
-	/**
-	 * Check if any tags are saved for this type and user.
-	 *
-	 * @return boolean
-	 */
-	public function isEmpty() {
-		return count($this->tags) === 0;
-	}
-
-	/**
-	 * Returns an array mapping a given tag's properties to its values:
-	 * ['id' => 0, 'name' = 'Tag', 'owner' = 'User', 'type' => 'tagtype']
-	 *
-	 * @param string $id The ID of the tag that is going to be mapped
-	 * @return array|false
-	 */
-	public function getTag($id) {
-		$key = $this->getTagById($id);
-		if ($key !== false) {
-			return $this->tagMap($this->tags[$key]);
-		}
-		return false;
-	}
-
-	/**
-	 * Get the tags for a specific user.
-	 *
-	 * This returns an array with maps containing each tag's properties:
-	 * [
-	 * 	['id' => 0, 'name' = 'First tag', 'owner' = 'User', 'type' => 'tagtype'],
-	 * 	['id' => 1, 'name' = 'Shared tag', 'owner' = 'Other user', 'type' => 'tagtype'],
-	 * ]
-	 *
-	 * @return array
-	 */
-	public function getTags() {
-		if (!count($this->tags)) {
-			return [];
-		}
-
-		usort($this->tags, function ($a, $b) {
-			return strnatcasecmp($a->getName(), $b->getName());
-		});
-		$tagMap = [];
-
-		foreach ($this->tags as $tag) {
-			if ($tag->getName() !== ITags::TAG_FAVORITE) {
-				$tagMap[] = $this->tagMap($tag);
-			}
-		}
-		return $tagMap;
-	}
-
-	/**
-	 * Return only the tags owned by the given user, omitting any tags shared
-	 * by other users.
-	 *
-	 * @param string $user The user whose tags are to be checked.
-	 * @return array An array of Tag objects.
-	 */
-	public function getTagsForUser($user) {
-		return array_filter($this->tags,
-			function ($tag) use ($user) {
-				return $tag->getOwner() === $user;
-			}
-		);
-	}
-
-	/**
-	 * Get the list of tags for the given ids.
-	 *
-	 * @param array $objIds array of object ids
-	 * @return array|boolean of tags id as key to array of tag names
-	 * or false if an error occurred
-	 */
-	public function getTagsForObjects(array $objIds) {
-		$entries = [];
-
-		try {
-			$conn = \OC::$server->getDatabaseConnection();
-			$chunks = array_chunk($objIds, 900, false);
-			foreach ($chunks as $chunk) {
-				$result = $conn->executeQuery(
-					'SELECT `category`, `categoryid`, `objid` ' .
-					'FROM `' . self::RELATION_TABLE . '` r, `' . self::TAG_TABLE . '` ' .
-					'WHERE `categoryid` = `id` AND `uid` = ? AND r.`type` = ? AND `objid` IN (?)',
-					[$this->user, $this->type, $chunk],
-					[null, null, IQueryBuilder::PARAM_INT_ARRAY]
-				);
-				while ($row = $result->fetch()) {
-					$objId = (int)$row['objid'];
-					if (!isset($entries[$objId])) {
-						$entries[$objId] = [];
-					}
-					$entries[$objId][] = $row['category'];
-				}
-				if ($result === null) {
-					\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-					return false;
-				}
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-
-		return $entries;
-	}
-
-	/**
-	 * Get the a list if items tagged with $tag.
-	 *
-	 * Throws an exception if the tag could not be found.
-	 *
-	 * @param string $tag Tag id or name.
-	 * @return array|false An array of object ids or false on error.
-	 * @throws \Exception
-	 */
-	public function getIdsForTag($tag) {
-		$result = null;
-		$tagId = false;
-		if (is_numeric($tag)) {
-			$tagId = $tag;
-		} elseif (is_string($tag)) {
-			$tag = trim($tag);
-			if ($tag === '') {
-				\OCP\Util::writeLog('core', __METHOD__.', Cannot use empty tag names', ILogger::DEBUG);
-				return false;
-			}
-			$tagId = $this->getTagId($tag);
-		}
-
-		if ($tagId === false) {
-			$l10n = \OC::$server->getL10N('core');
-			throw new \Exception(
-				$l10n->t('Could not find category "%s"', [$tag])
-			);
-		}
-
-		$ids = [];
-		$sql = 'SELECT `objid` FROM `' . self::RELATION_TABLE
-			. '` WHERE `categoryid` = ?';
-
-		try {
-			$stmt = \OC_DB::prepare($sql);
-			$result = $stmt->execute([$tagId]);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-				return false;
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-
-		if (!is_null($result)) {
-			while ($row = $result->fetchRow()) {
-				$ids[] = (int)$row['objid'];
-			}
-		}
-
-		return $ids;
-	}
-
-	/**
-	 * Checks whether a tag is saved for the given user,
-	 * disregarding the ones shared with him or her.
-	 *
-	 * @param string $name The tag name to check for.
-	 * @param string $user The user whose tags are to be checked.
-	 * @return bool
-	 */
-	public function userHasTag($name, $user) {
-		$key = $this->array_searchi($name, $this->getTagsForUser($user));
-		return ($key !== false) ? $this->tags[$key]->getId() : false;
-	}
-
-	/**
-	 * Checks whether a tag is saved for or shared with the current user.
-	 *
-	 * @param string $name The tag name to check for.
-	 * @return bool
-	 */
-	public function hasTag($name) {
-		return $this->getTagId($name) !== false;
-	}
-
-	/**
-	 * Add a new tag.
-	 *
-	 * @param string $name A string with a name of the tag
-	 * @return false|int the id of the added tag or false on error.
-	 */
-	public function add($name) {
-		$name = trim($name);
-
-		if ($name === '') {
-			\OCP\Util::writeLog('core', __METHOD__.', Cannot add an empty tag', ILogger::DEBUG);
-			return false;
-		}
-		if ($this->userHasTag($name, $this->user)) {
-			\OCP\Util::writeLog('core', __METHOD__.', name: ' . $name. ' exists already', ILogger::DEBUG);
-			return false;
-		}
-		try {
-			$tag = new Tag($this->user, $this->type, $name);
-			$tag = $this->mapper->insert($tag);
-			$this->tags[] = $tag;
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-		\OCP\Util::writeLog('core', __METHOD__.', id: ' . $tag->getId(), ILogger::DEBUG);
-		return $tag->getId();
-	}
-
-	/**
-	 * Rename tag.
-	 *
-	 * @param string|integer $from The name or ID of the existing tag
-	 * @param string $to The new name of the tag.
-	 * @return bool
-	 */
-	public function rename($from, $to) {
-		$from = trim($from);
-		$to = trim($to);
-
-		if ($to === '' || $from === '') {
-			\OCP\Util::writeLog('core', __METHOD__.', Cannot use empty tag names', ILogger::DEBUG);
-			return false;
-		}
-
-		if (is_numeric($from)) {
-			$key = $this->getTagById($from);
-		} else {
-			$key = $this->getTagByName($from);
-		}
-		if ($key === false) {
-			\OCP\Util::writeLog('core', __METHOD__.', tag: ' . $from. ' does not exist', ILogger::DEBUG);
-			return false;
-		}
-		$tag = $this->tags[$key];
-
-		if ($this->userHasTag($to, $tag->getOwner())) {
-			\OCP\Util::writeLog('core', __METHOD__.', A tag named ' . $to. ' already exists for user ' . $tag->getOwner() . '.', ILogger::DEBUG);
-			return false;
-		}
-
-		try {
-			$tag->setName($to);
-			$this->tags[$key] = $this->mapper->update($tag);
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-		return true;
-	}
-
-	/**
-	 * Add a list of new tags.
-	 *
-	 * @param string[] $names A string with a name or an array of strings containing
-	 * the name(s) of the tag(s) to add.
-	 * @param bool $sync When true, save the tags
-	 * @param int|null $id int Optional object id to add to this|these tag(s)
-	 * @return bool Returns false on error.
-	 */
-	public function addMultiple($names, $sync = false, $id = null) {
-		if (!is_array($names)) {
-			$names = [$names];
-		}
-		$names = array_map('trim', $names);
-		array_filter($names);
-
-		$newones = [];
-		foreach ($names as $name) {
-			if (!$this->hasTag($name) && $name !== '') {
-				$newones[] = new Tag($this->user, $this->type, $name);
-			}
-			if (!is_null($id)) {
-				// Insert $objectid, $categoryid  pairs if not exist.
-				self::$relations[] = ['objid' => $id, 'tag' => $name];
-			}
-		}
-		$this->tags = array_merge($this->tags, $newones);
-		if ($sync === true) {
-			$this->save();
-		}
-
-		return true;
-	}
-
-	/**
-	 * Save the list of tags and their object relations
-	 */
-	protected function save() {
-		if (is_array($this->tags)) {
-			foreach ($this->tags as $tag) {
-				try {
-					if (!$this->mapper->tagExists($tag)) {
-						$this->mapper->insert($tag);
-					}
-				} catch (\Exception $e) {
-					\OC::$server->getLogger()->logException($e, [
-						'message' => __METHOD__,
-						'level' => ILogger::ERROR,
-						'app' => 'core',
-					]);
-				}
-			}
-
-			// reload tags to get the proper ids.
-			$this->tags = $this->mapper->loadTags($this->owners, $this->type);
-			\OCP\Util::writeLog('core', __METHOD__.', tags: ' . print_r($this->tags, true),
-				ILogger::DEBUG);
-			// Loop through temporarily cached objectid/tagname pairs
-			// and save relations.
-			$tags = $this->tags;
-			// For some reason this is needed or array_search(i) will return 0..?
-			ksort($tags);
-			$dbConnection = \OC::$server->getDatabaseConnection();
-			foreach (self::$relations as $relation) {
-				$tagId = $this->getTagId($relation['tag']);
-				\OCP\Util::writeLog('core', __METHOD__ . 'catid, ' . $relation['tag'] . ' ' . $tagId, ILogger::DEBUG);
-				if ($tagId) {
-					try {
-						$dbConnection->insertIfNotExist(self::RELATION_TABLE,
-							[
-								'objid' => $relation['objid'],
-								'categoryid' => $tagId,
-								'type' => $this->type,
-							]);
-					} catch (\Exception $e) {
-						\OC::$server->getLogger()->logException($e, [
-							'message' => __METHOD__,
-							'level' => ILogger::ERROR,
-							'app' => 'core',
-						]);
-					}
-				}
-			}
-			self::$relations = []; // reset
-		} else {
-			\OCP\Util::writeLog('core', __METHOD__.', $this->tags is not an array! '
-				. print_r($this->tags, true), ILogger::ERROR);
-		}
-	}
-
-	/**
-	 * Delete tags and tag/object relations for a user.
-	 *
-	 * For hooking up on post_deleteUser
-	 *
-	 * @param array $arguments
-	 */
-	public static function post_deleteUser($arguments) {
-		// Find all objectid/tagId pairs.
-		$result = null;
-		try {
-			$stmt = \OC_DB::prepare('SELECT `id` FROM `' . self::TAG_TABLE . '` '
-				. 'WHERE `uid` = ?');
-			$result = $stmt->execute([$arguments['uid']]);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-		}
-
-		if (!is_null($result)) {
-			try {
-				$stmt = \OC_DB::prepare('DELETE FROM `' . self::RELATION_TABLE . '` '
-					. 'WHERE `categoryid` = ?');
-				while ($row = $result->fetchRow()) {
-					try {
-						$stmt->execute([$row['id']]);
-					} catch (\Exception $e) {
-						\OC::$server->getLogger()->logException($e, [
-							'message' => __METHOD__,
-							'level' => ILogger::ERROR,
-							'app' => 'core',
-						]);
-					}
-				}
-			} catch (\Exception $e) {
-				\OC::$server->getLogger()->logException($e, [
-					'message' => __METHOD__,
-					'level' => ILogger::ERROR,
-					'app' => 'core',
-				]);
-			}
-		}
-		try {
-			$stmt = \OC_DB::prepare('DELETE FROM `' . self::TAG_TABLE . '` '
-				. 'WHERE `uid` = ?');
-			$result = $stmt->execute([$arguments['uid']]);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. ', DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-		}
-	}
-
-	/**
-	 * Delete tag/object relations from the db
-	 *
-	 * @param array $ids The ids of the objects
-	 * @return boolean Returns false on error.
-	 */
-	public function purgeObjects(array $ids) {
-		if (count($ids) === 0) {
-			// job done ;)
-			return true;
-		}
-		$updates = $ids;
-		try {
-			$query = 'DELETE FROM `' . self::RELATION_TABLE . '` ';
-			$query .= 'WHERE `objid` IN (' . str_repeat('?,', count($ids) - 1) . '?) ';
-			$query .= 'AND `type`= ?';
-			$updates[] = $this->type;
-			$stmt = \OC_DB::prepare($query);
-			$result = $stmt->execute($updates);
-			if ($result === null) {
-				\OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
-				return false;
-			}
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-		return true;
-	}
-
-	/**
-	 * Get favorites for an object type
-	 *
-	 * @return array|false An array of object ids.
-	 */
-	public function getFavorites() {
-		if (!$this->userHasTag(ITags::TAG_FAVORITE, $this->user)) {
-			return [];
-		}
-
-		try {
-			return $this->getIdsForTag(ITags::TAG_FAVORITE);
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return [];
-		}
-	}
-
-	/**
-	 * Add an object to favorites
-	 *
-	 * @param int $objid The id of the object
-	 * @return boolean
-	 */
-	public function addToFavorites($objid) {
-		if (!$this->userHasTag(ITags::TAG_FAVORITE, $this->user)) {
-			$this->add(ITags::TAG_FAVORITE);
-		}
-		return $this->tagAs($objid, ITags::TAG_FAVORITE);
-	}
-
-	/**
-	 * Remove an object from favorites
-	 *
-	 * @param int $objid The id of the object
-	 * @return boolean
-	 */
-	public function removeFromFavorites($objid) {
-		return $this->unTag($objid, ITags::TAG_FAVORITE);
-	}
-
-	/**
-	 * Creates a tag/object relation.
-	 *
-	 * @param int $objid The id of the object
-	 * @param string $tag The id or name of the tag
-	 * @return boolean Returns false on error.
-	 */
-	public function tagAs($objid, $tag) {
-		if (is_string($tag) && !is_numeric($tag)) {
-			$tag = trim($tag);
-			if ($tag === '') {
-				\OCP\Util::writeLog('core', __METHOD__.', Cannot add an empty tag', ILogger::DEBUG);
-				return false;
-			}
-			if (!$this->hasTag($tag)) {
-				$this->add($tag);
-			}
-			$tagId = $this->getTagId($tag);
-		} else {
-			$tagId = $tag;
-		}
-		try {
-			\OC::$server->getDatabaseConnection()->insertIfNotExist(self::RELATION_TABLE,
-				[
-					'objid' => $objid,
-					'categoryid' => $tagId,
-					'type' => $this->type,
-				]);
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-		return true;
-	}
-
-	/**
-	 * Delete single tag/object relation from the db
-	 *
-	 * @param int $objid The id of the object
-	 * @param string $tag The id or name of the tag
-	 * @return boolean
-	 */
-	public function unTag($objid, $tag) {
-		if (is_string($tag) && !is_numeric($tag)) {
-			$tag = trim($tag);
-			if ($tag === '') {
-				\OCP\Util::writeLog('core', __METHOD__.', Tag name is empty', ILogger::DEBUG);
-				return false;
-			}
-			$tagId = $this->getTagId($tag);
-		} else {
-			$tagId = $tag;
-		}
-
-		try {
-			$sql = 'DELETE FROM `' . self::RELATION_TABLE . '` '
-					. 'WHERE `objid` = ? AND `categoryid` = ? AND `type` = ?';
-			$stmt = \OC_DB::prepare($sql);
-			$stmt->execute([$objid, $tagId, $this->type]);
-		} catch (\Exception $e) {
-			\OC::$server->getLogger()->logException($e, [
-				'message' => __METHOD__,
-				'level' => ILogger::ERROR,
-				'app' => 'core',
-			]);
-			return false;
-		}
-		return true;
-	}
-
-	/**
-	 * Delete tags from the database.
-	 *
-	 * @param string[]|integer[] $names An array of tags (names or IDs) to delete
-	 * @return bool Returns false on error
-	 */
-	public function delete($names) {
-		if (!is_array($names)) {
-			$names = [$names];
-		}
-
-		$names = array_map('trim', $names);
-		array_filter($names);
-
-		\OCP\Util::writeLog('core', __METHOD__ . ', before: '
-			. print_r($this->tags, true), ILogger::DEBUG);
-		foreach ($names as $name) {
-			$id = null;
-
-			if (is_numeric($name)) {
-				$key = $this->getTagById($name);
-			} else {
-				$key = $this->getTagByName($name);
-			}
-			if ($key !== false) {
-				$tag = $this->tags[$key];
-				$id = $tag->getId();
-				unset($this->tags[$key]);
-				$this->mapper->delete($tag);
-			} else {
-				\OCP\Util::writeLog('core', __METHOD__ . 'Cannot delete tag ' . $name
-					. ': not found.', ILogger::ERROR);
-			}
-			if (!is_null($id) && $id !== false) {
-				try {
-					$sql = 'DELETE FROM `' . self::RELATION_TABLE . '` '
-							. 'WHERE `categoryid` = ?';
-					$stmt = \OC_DB::prepare($sql);
-					$result = $stmt->execute([$id]);
-					if ($result === null) {
-						\OCP\Util::writeLog('core',
-							__METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(),
-							ILogger::ERROR);
-						return false;
-					}
-				} catch (\Exception $e) {
-					\OC::$server->getLogger()->logException($e, [
-						'message' => __METHOD__,
-						'level' => ILogger::ERROR,
-						'app' => 'core',
-					]);
-					return false;
-				}
-			}
-		}
-		return true;
-	}
-
-	// case-insensitive array_search
-	protected function array_searchi($needle, $haystack, $mem = 'getName') {
-		if (!is_array($haystack)) {
-			return false;
-		}
-		return array_search(strtolower($needle), array_map(
-			function ($tag) use ($mem) {
-				return strtolower(call_user_func([$tag, $mem]));
-			}, $haystack)
-		);
-	}
-
-	/**
-	 * Get a tag's ID.
-	 *
-	 * @param string $name The tag name to look for.
-	 * @return string|bool The tag's id or false if no matching tag is found.
-	 */
-	private function getTagId($name) {
-		$key = $this->array_searchi($name, $this->tags);
-		if ($key !== false) {
-			return $this->tags[$key]->getId();
-		}
-		return false;
-	}
-
-	/**
-	 * Get a tag by its name.
-	 *
-	 * @param string $name The tag name.
-	 * @return integer|bool The tag object's offset within the $this->tags
-	 *                      array or false if it doesn't exist.
-	 */
-	private function getTagByName($name) {
-		return $this->array_searchi($name, $this->tags, 'getName');
-	}
-
-	/**
-	 * Get a tag by its ID.
-	 *
-	 * @param string $id The tag ID to look for.
-	 * @return integer|bool The tag object's offset within the $this->tags
-	 *                      array or false if it doesn't exist.
-	 */
-	private function getTagById($id) {
-		return $this->array_searchi($id, $this->tags, 'getId');
-	}
-
-	/**
-	 * Returns an array mapping a given tag's properties to its values:
-	 * ['id' => 0, 'name' = 'Tag', 'owner' = 'User', 'type' => 'tagtype']
-	 *
-	 * @param Tag $tag The tag that is going to be mapped
-	 * @return array
-	 */
-	private function tagMap(Tag $tag) {
-		return [
-			'id' => $tag->getId(),
-			'name' => $tag->getName(),
-			'owner' => $tag->getOwner(),
-			'type' => $tag->getType()
-		];
-	}
+    /**
+     * Tags
+     *
+     * @var array
+     */
+    private $tags = [];
+
+    /**
+     * Used for storing objectid/categoryname pairs while rescanning.
+     *
+     * @var array
+     */
+    private static $relations = [];
+
+    /**
+     * Type
+     *
+     * @var string
+     */
+    private $type;
+
+    /**
+     * User
+     *
+     * @var string
+     */
+    private $user;
+
+    /**
+     * Are we including tags for shared items?
+     *
+     * @var bool
+     */
+    private $includeShared = false;
+
+    /**
+     * The current user, plus any owners of the items shared with the current
+     * user, if $this->includeShared === true.
+     *
+     * @var array
+     */
+    private $owners = [];
+
+    /**
+     * The Mapper we're using to communicate our Tag objects to the database.
+     *
+     * @var TagMapper
+     */
+    private $mapper;
+
+    /**
+     * The sharing backend for objects of $this->type. Required if
+     * $this->includeShared === true to determine ownership of items.
+     *
+     * @var \OCP\Share_Backend
+     */
+    private $backend;
+
+    public const TAG_TABLE = '*PREFIX*vcategory';
+    public const RELATION_TABLE = '*PREFIX*vcategory_to_object';
+
+    /**
+     * Constructor.
+     *
+     * @param TagMapper $mapper Instance of the TagMapper abstraction layer.
+     * @param string $user The user whose data the object will operate on.
+     * @param string $type The type of items for which tags will be loaded.
+     * @param array $defaultTags Tags that should be created at construction.
+     *
+     * since 20.0.0 $includeShared isn't used anymore
+     */
+    public function __construct(TagMapper $mapper, $user, $type, $defaultTags = []) {
+        $this->mapper = $mapper;
+        $this->user = $user;
+        $this->type = $type;
+        $this->owners = [$this->user];
+        $this->tags = $this->mapper->loadTags($this->owners, $this->type);
+
+        if (count($defaultTags) > 0 && count($this->tags) === 0) {
+            $this->addMultiple($defaultTags, true);
+        }
+    }
+
+    /**
+     * Check if any tags are saved for this type and user.
+     *
+     * @return boolean
+     */
+    public function isEmpty() {
+        return count($this->tags) === 0;
+    }
+
+    /**
+     * Returns an array mapping a given tag's properties to its values:
+     * ['id' => 0, 'name' = 'Tag', 'owner' = 'User', 'type' => 'tagtype']
+     *
+     * @param string $id The ID of the tag that is going to be mapped
+     * @return array|false
+     */
+    public function getTag($id) {
+        $key = $this->getTagById($id);
+        if ($key !== false) {
+            return $this->tagMap($this->tags[$key]);
+        }
+        return false;
+    }
+
+    /**
+     * Get the tags for a specific user.
+     *
+     * This returns an array with maps containing each tag's properties:
+     * [
+     * 	['id' => 0, 'name' = 'First tag', 'owner' = 'User', 'type' => 'tagtype'],
+     * 	['id' => 1, 'name' = 'Shared tag', 'owner' = 'Other user', 'type' => 'tagtype'],
+     * ]
+     *
+     * @return array
+     */
+    public function getTags() {
+        if (!count($this->tags)) {
+            return [];
+        }
+
+        usort($this->tags, function ($a, $b) {
+            return strnatcasecmp($a->getName(), $b->getName());
+        });
+        $tagMap = [];
+
+        foreach ($this->tags as $tag) {
+            if ($tag->getName() !== ITags::TAG_FAVORITE) {
+                $tagMap[] = $this->tagMap($tag);
+            }
+        }
+        return $tagMap;
+    }
+
+    /**
+     * Return only the tags owned by the given user, omitting any tags shared
+     * by other users.
+     *
+     * @param string $user The user whose tags are to be checked.
+     * @return array An array of Tag objects.
+     */
+    public function getTagsForUser($user) {
+        return array_filter($this->tags,
+            function ($tag) use ($user) {
+                return $tag->getOwner() === $user;
+            }
+        );
+    }
+
+    /**
+     * Get the list of tags for the given ids.
+     *
+     * @param array $objIds array of object ids
+     * @return array|boolean of tags id as key to array of tag names
+     * or false if an error occurred
+     */
+    public function getTagsForObjects(array $objIds) {
+        $entries = [];
+
+        try {
+            $conn = \OC::$server->getDatabaseConnection();
+            $chunks = array_chunk($objIds, 900, false);
+            foreach ($chunks as $chunk) {
+                $result = $conn->executeQuery(
+                    'SELECT `category`, `categoryid`, `objid` ' .
+                    'FROM `' . self::RELATION_TABLE . '` r, `' . self::TAG_TABLE . '` ' .
+                    'WHERE `categoryid` = `id` AND `uid` = ? AND r.`type` = ? AND `objid` IN (?)',
+                    [$this->user, $this->type, $chunk],
+                    [null, null, IQueryBuilder::PARAM_INT_ARRAY]
+                );
+                while ($row = $result->fetch()) {
+                    $objId = (int)$row['objid'];
+                    if (!isset($entries[$objId])) {
+                        $entries[$objId] = [];
+                    }
+                    $entries[$objId][] = $row['category'];
+                }
+                if ($result === null) {
+                    \OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
+                    return false;
+                }
+            }
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+
+        return $entries;
+    }
+
+    /**
+     * Get the a list if items tagged with $tag.
+     *
+     * Throws an exception if the tag could not be found.
+     *
+     * @param string $tag Tag id or name.
+     * @return array|false An array of object ids or false on error.
+     * @throws \Exception
+     */
+    public function getIdsForTag($tag) {
+        $result = null;
+        $tagId = false;
+        if (is_numeric($tag)) {
+            $tagId = $tag;
+        } elseif (is_string($tag)) {
+            $tag = trim($tag);
+            if ($tag === '') {
+                \OCP\Util::writeLog('core', __METHOD__.', Cannot use empty tag names', ILogger::DEBUG);
+                return false;
+            }
+            $tagId = $this->getTagId($tag);
+        }
+
+        if ($tagId === false) {
+            $l10n = \OC::$server->getL10N('core');
+            throw new \Exception(
+                $l10n->t('Could not find category "%s"', [$tag])
+            );
+        }
+
+        $ids = [];
+        $sql = 'SELECT `objid` FROM `' . self::RELATION_TABLE
+            . '` WHERE `categoryid` = ?';
+
+        try {
+            $stmt = \OC_DB::prepare($sql);
+            $result = $stmt->execute([$tagId]);
+            if ($result === null) {
+                \OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
+                return false;
+            }
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+
+        if (!is_null($result)) {
+            while ($row = $result->fetchRow()) {
+                $ids[] = (int)$row['objid'];
+            }
+        }
+
+        return $ids;
+    }
+
+    /**
+     * Checks whether a tag is saved for the given user,
+     * disregarding the ones shared with him or her.
+     *
+     * @param string $name The tag name to check for.
+     * @param string $user The user whose tags are to be checked.
+     * @return bool
+     */
+    public function userHasTag($name, $user) {
+        $key = $this->array_searchi($name, $this->getTagsForUser($user));
+        return ($key !== false) ? $this->tags[$key]->getId() : false;
+    }
+
+    /**
+     * Checks whether a tag is saved for or shared with the current user.
+     *
+     * @param string $name The tag name to check for.
+     * @return bool
+     */
+    public function hasTag($name) {
+        return $this->getTagId($name) !== false;
+    }
+
+    /**
+     * Add a new tag.
+     *
+     * @param string $name A string with a name of the tag
+     * @return false|int the id of the added tag or false on error.
+     */
+    public function add($name) {
+        $name = trim($name);
+
+        if ($name === '') {
+            \OCP\Util::writeLog('core', __METHOD__.', Cannot add an empty tag', ILogger::DEBUG);
+            return false;
+        }
+        if ($this->userHasTag($name, $this->user)) {
+            \OCP\Util::writeLog('core', __METHOD__.', name: ' . $name. ' exists already', ILogger::DEBUG);
+            return false;
+        }
+        try {
+            $tag = new Tag($this->user, $this->type, $name);
+            $tag = $this->mapper->insert($tag);
+            $this->tags[] = $tag;
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+        \OCP\Util::writeLog('core', __METHOD__.', id: ' . $tag->getId(), ILogger::DEBUG);
+        return $tag->getId();
+    }
+
+    /**
+     * Rename tag.
+     *
+     * @param string|integer $from The name or ID of the existing tag
+     * @param string $to The new name of the tag.
+     * @return bool
+     */
+    public function rename($from, $to) {
+        $from = trim($from);
+        $to = trim($to);
+
+        if ($to === '' || $from === '') {
+            \OCP\Util::writeLog('core', __METHOD__.', Cannot use empty tag names', ILogger::DEBUG);
+            return false;
+        }
+
+        if (is_numeric($from)) {
+            $key = $this->getTagById($from);
+        } else {
+            $key = $this->getTagByName($from);
+        }
+        if ($key === false) {
+            \OCP\Util::writeLog('core', __METHOD__.', tag: ' . $from. ' does not exist', ILogger::DEBUG);
+            return false;
+        }
+        $tag = $this->tags[$key];
+
+        if ($this->userHasTag($to, $tag->getOwner())) {
+            \OCP\Util::writeLog('core', __METHOD__.', A tag named ' . $to. ' already exists for user ' . $tag->getOwner() . '.', ILogger::DEBUG);
+            return false;
+        }
+
+        try {
+            $tag->setName($to);
+            $this->tags[$key] = $this->mapper->update($tag);
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Add a list of new tags.
+     *
+     * @param string[] $names A string with a name or an array of strings containing
+     * the name(s) of the tag(s) to add.
+     * @param bool $sync When true, save the tags
+     * @param int|null $id int Optional object id to add to this|these tag(s)
+     * @return bool Returns false on error.
+     */
+    public function addMultiple($names, $sync = false, $id = null) {
+        if (!is_array($names)) {
+            $names = [$names];
+        }
+        $names = array_map('trim', $names);
+        array_filter($names);
+
+        $newones = [];
+        foreach ($names as $name) {
+            if (!$this->hasTag($name) && $name !== '') {
+                $newones[] = new Tag($this->user, $this->type, $name);
+            }
+            if (!is_null($id)) {
+                // Insert $objectid, $categoryid  pairs if not exist.
+                self::$relations[] = ['objid' => $id, 'tag' => $name];
+            }
+        }
+        $this->tags = array_merge($this->tags, $newones);
+        if ($sync === true) {
+            $this->save();
+        }
+
+        return true;
+    }
+
+    /**
+     * Save the list of tags and their object relations
+     */
+    protected function save() {
+        if (is_array($this->tags)) {
+            foreach ($this->tags as $tag) {
+                try {
+                    if (!$this->mapper->tagExists($tag)) {
+                        $this->mapper->insert($tag);
+                    }
+                } catch (\Exception $e) {
+                    \OC::$server->getLogger()->logException($e, [
+                        'message' => __METHOD__,
+                        'level' => ILogger::ERROR,
+                        'app' => 'core',
+                    ]);
+                }
+            }
+
+            // reload tags to get the proper ids.
+            $this->tags = $this->mapper->loadTags($this->owners, $this->type);
+            \OCP\Util::writeLog('core', __METHOD__.', tags: ' . print_r($this->tags, true),
+                ILogger::DEBUG);
+            // Loop through temporarily cached objectid/tagname pairs
+            // and save relations.
+            $tags = $this->tags;
+            // For some reason this is needed or array_search(i) will return 0..?
+            ksort($tags);
+            $dbConnection = \OC::$server->getDatabaseConnection();
+            foreach (self::$relations as $relation) {
+                $tagId = $this->getTagId($relation['tag']);
+                \OCP\Util::writeLog('core', __METHOD__ . 'catid, ' . $relation['tag'] . ' ' . $tagId, ILogger::DEBUG);
+                if ($tagId) {
+                    try {
+                        $dbConnection->insertIfNotExist(self::RELATION_TABLE,
+                            [
+                                'objid' => $relation['objid'],
+                                'categoryid' => $tagId,
+                                'type' => $this->type,
+                            ]);
+                    } catch (\Exception $e) {
+                        \OC::$server->getLogger()->logException($e, [
+                            'message' => __METHOD__,
+                            'level' => ILogger::ERROR,
+                            'app' => 'core',
+                        ]);
+                    }
+                }
+            }
+            self::$relations = []; // reset
+        } else {
+            \OCP\Util::writeLog('core', __METHOD__.', $this->tags is not an array! '
+                . print_r($this->tags, true), ILogger::ERROR);
+        }
+    }
+
+    /**
+     * Delete tags and tag/object relations for a user.
+     *
+     * For hooking up on post_deleteUser
+     *
+     * @param array $arguments
+     */
+    public static function post_deleteUser($arguments) {
+        // Find all objectid/tagId pairs.
+        $result = null;
+        try {
+            $stmt = \OC_DB::prepare('SELECT `id` FROM `' . self::TAG_TABLE . '` '
+                . 'WHERE `uid` = ?');
+            $result = $stmt->execute([$arguments['uid']]);
+            if ($result === null) {
+                \OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
+            }
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+        }
+
+        if (!is_null($result)) {
+            try {
+                $stmt = \OC_DB::prepare('DELETE FROM `' . self::RELATION_TABLE . '` '
+                    . 'WHERE `categoryid` = ?');
+                while ($row = $result->fetchRow()) {
+                    try {
+                        $stmt->execute([$row['id']]);
+                    } catch (\Exception $e) {
+                        \OC::$server->getLogger()->logException($e, [
+                            'message' => __METHOD__,
+                            'level' => ILogger::ERROR,
+                            'app' => 'core',
+                        ]);
+                    }
+                }
+            } catch (\Exception $e) {
+                \OC::$server->getLogger()->logException($e, [
+                    'message' => __METHOD__,
+                    'level' => ILogger::ERROR,
+                    'app' => 'core',
+                ]);
+            }
+        }
+        try {
+            $stmt = \OC_DB::prepare('DELETE FROM `' . self::TAG_TABLE . '` '
+                . 'WHERE `uid` = ?');
+            $result = $stmt->execute([$arguments['uid']]);
+            if ($result === null) {
+                \OCP\Util::writeLog('core', __METHOD__. ', DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
+            }
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+        }
+    }
+
+    /**
+     * Delete tag/object relations from the db
+     *
+     * @param array $ids The ids of the objects
+     * @return boolean Returns false on error.
+     */
+    public function purgeObjects(array $ids) {
+        if (count($ids) === 0) {
+            // job done ;)
+            return true;
+        }
+        $updates = $ids;
+        try {
+            $query = 'DELETE FROM `' . self::RELATION_TABLE . '` ';
+            $query .= 'WHERE `objid` IN (' . str_repeat('?,', count($ids) - 1) . '?) ';
+            $query .= 'AND `type`= ?';
+            $updates[] = $this->type;
+            $stmt = \OC_DB::prepare($query);
+            $result = $stmt->execute($updates);
+            if ($result === null) {
+                \OCP\Util::writeLog('core', __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(), ILogger::ERROR);
+                return false;
+            }
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Get favorites for an object type
+     *
+     * @return array|false An array of object ids.
+     */
+    public function getFavorites() {
+        if (!$this->userHasTag(ITags::TAG_FAVORITE, $this->user)) {
+            return [];
+        }
+
+        try {
+            return $this->getIdsForTag(ITags::TAG_FAVORITE);
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return [];
+        }
+    }
+
+    /**
+     * Add an object to favorites
+     *
+     * @param int $objid The id of the object
+     * @return boolean
+     */
+    public function addToFavorites($objid) {
+        if (!$this->userHasTag(ITags::TAG_FAVORITE, $this->user)) {
+            $this->add(ITags::TAG_FAVORITE);
+        }
+        return $this->tagAs($objid, ITags::TAG_FAVORITE);
+    }
+
+    /**
+     * Remove an object from favorites
+     *
+     * @param int $objid The id of the object
+     * @return boolean
+     */
+    public function removeFromFavorites($objid) {
+        return $this->unTag($objid, ITags::TAG_FAVORITE);
+    }
+
+    /**
+     * Creates a tag/object relation.
+     *
+     * @param int $objid The id of the object
+     * @param string $tag The id or name of the tag
+     * @return boolean Returns false on error.
+     */
+    public function tagAs($objid, $tag) {
+        if (is_string($tag) && !is_numeric($tag)) {
+            $tag = trim($tag);
+            if ($tag === '') {
+                \OCP\Util::writeLog('core', __METHOD__.', Cannot add an empty tag', ILogger::DEBUG);
+                return false;
+            }
+            if (!$this->hasTag($tag)) {
+                $this->add($tag);
+            }
+            $tagId = $this->getTagId($tag);
+        } else {
+            $tagId = $tag;
+        }
+        try {
+            \OC::$server->getDatabaseConnection()->insertIfNotExist(self::RELATION_TABLE,
+                [
+                    'objid' => $objid,
+                    'categoryid' => $tagId,
+                    'type' => $this->type,
+                ]);
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Delete single tag/object relation from the db
+     *
+     * @param int $objid The id of the object
+     * @param string $tag The id or name of the tag
+     * @return boolean
+     */
+    public function unTag($objid, $tag) {
+        if (is_string($tag) && !is_numeric($tag)) {
+            $tag = trim($tag);
+            if ($tag === '') {
+                \OCP\Util::writeLog('core', __METHOD__.', Tag name is empty', ILogger::DEBUG);
+                return false;
+            }
+            $tagId = $this->getTagId($tag);
+        } else {
+            $tagId = $tag;
+        }
+
+        try {
+            $sql = 'DELETE FROM `' . self::RELATION_TABLE . '` '
+                    . 'WHERE `objid` = ? AND `categoryid` = ? AND `type` = ?';
+            $stmt = \OC_DB::prepare($sql);
+            $stmt->execute([$objid, $tagId, $this->type]);
+        } catch (\Exception $e) {
+            \OC::$server->getLogger()->logException($e, [
+                'message' => __METHOD__,
+                'level' => ILogger::ERROR,
+                'app' => 'core',
+            ]);
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Delete tags from the database.
+     *
+     * @param string[]|integer[] $names An array of tags (names or IDs) to delete
+     * @return bool Returns false on error
+     */
+    public function delete($names) {
+        if (!is_array($names)) {
+            $names = [$names];
+        }
+
+        $names = array_map('trim', $names);
+        array_filter($names);
+
+        \OCP\Util::writeLog('core', __METHOD__ . ', before: '
+            . print_r($this->tags, true), ILogger::DEBUG);
+        foreach ($names as $name) {
+            $id = null;
+
+            if (is_numeric($name)) {
+                $key = $this->getTagById($name);
+            } else {
+                $key = $this->getTagByName($name);
+            }
+            if ($key !== false) {
+                $tag = $this->tags[$key];
+                $id = $tag->getId();
+                unset($this->tags[$key]);
+                $this->mapper->delete($tag);
+            } else {
+                \OCP\Util::writeLog('core', __METHOD__ . 'Cannot delete tag ' . $name
+                    . ': not found.', ILogger::ERROR);
+            }
+            if (!is_null($id) && $id !== false) {
+                try {
+                    $sql = 'DELETE FROM `' . self::RELATION_TABLE . '` '
+                            . 'WHERE `categoryid` = ?';
+                    $stmt = \OC_DB::prepare($sql);
+                    $result = $stmt->execute([$id]);
+                    if ($result === null) {
+                        \OCP\Util::writeLog('core',
+                            __METHOD__. 'DB error: ' . \OC::$server->getDatabaseConnection()->getError(),
+                            ILogger::ERROR);
+                        return false;
+                    }
+                } catch (\Exception $e) {
+                    \OC::$server->getLogger()->logException($e, [
+                        'message' => __METHOD__,
+                        'level' => ILogger::ERROR,
+                        'app' => 'core',
+                    ]);
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    // case-insensitive array_search
+    protected function array_searchi($needle, $haystack, $mem = 'getName') {
+        if (!is_array($haystack)) {
+            return false;
+        }
+        return array_search(strtolower($needle), array_map(
+            function ($tag) use ($mem) {
+                return strtolower(call_user_func([$tag, $mem]));
+            }, $haystack)
+        );
+    }
+
+    /**
+     * Get a tag's ID.
+     *
+     * @param string $name The tag name to look for.
+     * @return string|bool The tag's id or false if no matching tag is found.
+     */
+    private function getTagId($name) {
+        $key = $this->array_searchi($name, $this->tags);
+        if ($key !== false) {
+            return $this->tags[$key]->getId();
+        }
+        return false;
+    }
+
+    /**
+     * Get a tag by its name.
+     *
+     * @param string $name The tag name.
+     * @return integer|bool The tag object's offset within the $this->tags
+     *                      array or false if it doesn't exist.
+     */
+    private function getTagByName($name) {
+        return $this->array_searchi($name, $this->tags, 'getName');
+    }
+
+    /**
+     * Get a tag by its ID.
+     *
+     * @param string $id The tag ID to look for.
+     * @return integer|bool The tag object's offset within the $this->tags
+     *                      array or false if it doesn't exist.
+     */
+    private function getTagById($id) {
+        return $this->array_searchi($id, $this->tags, 'getId');
+    }
+
+    /**
+     * Returns an array mapping a given tag's properties to its values:
+     * ['id' => 0, 'name' = 'Tag', 'owner' = 'User', 'type' => 'tagtype']
+     *
+     * @param Tag $tag The tag that is going to be mapped
+     * @return array
+     */
+    private function tagMap(Tag $tag) {
+        return [
+            'id' => $tag->getId(),
+            'name' => $tag->getName(),
+            'owner' => $tag->getOwner(),
+            'type' => $tag->getType()
+        ];
+    }
 }