nextcloud / server

apps/dav/lib/CardDAV/CardDavBackend.php

Indentation +1299 added lines, -1299 removed lines

@@ -60,1303 +60,1303 @@
 use Sabre\VObject\Reader;
 
 class CardDavBackend implements BackendInterface, SyncSupport {
-	public const PERSONAL_ADDRESSBOOK_URI = 'contacts';
-	public const PERSONAL_ADDRESSBOOK_NAME = 'Contacts';
-
-	private Principal $principalBackend;
-	private string $dbCardsTable = 'cards';
-	private string $dbCardsPropertiesTable = 'cards_properties';
-	private IDBConnection $db;
-	private Backend $sharingBackend;
-
-	/** @var array properties to index */
-	public static array $indexProperties = [
-		'BDAY', 'UID', 'N', 'FN', 'TITLE', 'ROLE', 'NOTE', 'NICKNAME',
-		'ORG', 'CATEGORIES', 'EMAIL', 'TEL', 'IMPP', 'ADR', 'URL', 'GEO',
-		'CLOUD', 'X-SOCIALPROFILE'];
-
-	/**
-	 * @var string[] Map of uid => display name
-	 */
-	protected array $userDisplayNames;
-	private IUserManager $userManager;
-	private IEventDispatcher $dispatcher;
-	private array $etagCache = [];
-
-	/**
-	 * CardDavBackend constructor.
-	 *
-	 * @param IDBConnection $db
-	 * @param Principal $principalBackend
-	 * @param IUserManager $userManager
-	 * @param IGroupManager $groupManager
-	 * @param IEventDispatcher $dispatcher
-	 */
-	public function __construct(IDBConnection $db,
-								Principal $principalBackend,
-								IUserManager $userManager,
-								IGroupManager $groupManager,
-								IEventDispatcher $dispatcher) {
-		$this->db = $db;
-		$this->principalBackend = $principalBackend;
-		$this->userManager = $userManager;
-		$this->dispatcher = $dispatcher;
-		$this->sharingBackend = new Backend($this->db, $this->userManager, $groupManager, $principalBackend, 'addressbook');
-	}
-
-	/**
-	 * Return the number of address books for a principal
-	 *
-	 * @param $principalUri
-	 * @return int
-	 */
-	public function getAddressBooksForUserCount($principalUri) {
-		$principalUri = $this->convertPrincipal($principalUri, true);
-		$query = $this->db->getQueryBuilder();
-		$query->select($query->func()->count('*'))
-			->from('addressbooks')
-			->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
-
-		$result = $query->executeQuery();
-		$column = (int) $result->fetchOne();
-		$result->closeCursor();
-		return $column;
-	}
-
-	/**
-	 * Returns the list of address books for a specific user.
-	 *
-	 * Every addressbook should have the following properties:
-	 *   id - an arbitrary unique id
-	 *   uri - the 'basename' part of the url
-	 *   principaluri - Same as the passed parameter
-	 *
-	 * Any additional clark-notation property may be passed besides this. Some
-	 * common ones are :
-	 *   {DAV:}displayname
-	 *   {urn:ietf:params:xml:ns:carddav}addressbook-description
-	 *   {http://calendarserver.org/ns/}getctag
-	 *
-	 * @param string $principalUri
-	 * @return array
-	 */
-	public function getAddressBooksForUser($principalUri) {
-		$principalUriOriginal = $principalUri;
-		$principalUri = $this->convertPrincipal($principalUri, true);
-		$query = $this->db->getQueryBuilder();
-		$query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
-			->from('addressbooks')
-			->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
-
-		$addressBooks = [];
-
-		$result = $query->execute();
-		while ($row = $result->fetch()) {
-			$addressBooks[$row['id']] = [
-				'id' => $row['id'],
-				'uri' => $row['uri'],
-				'principaluri' => $this->convertPrincipal($row['principaluri'], false),
-				'{DAV:}displayname' => $row['displayname'],
-				'{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
-				'{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
-				'{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
-			];
-
-			$this->addOwnerPrincipal($addressBooks[$row['id']]);
-		}
-		$result->closeCursor();
-
-		// query for shared addressbooks
-		$principals = $this->principalBackend->getGroupMembership($principalUriOriginal, true);
-		$principals = array_merge($principals, $this->principalBackend->getCircleMembership($principalUriOriginal));
-
-		$principals[] = $principalUri;
-
-		$query = $this->db->getQueryBuilder();
-		$result = $query->select(['a.id', 'a.uri', 'a.displayname', 'a.principaluri', 'a.description', 'a.synctoken', 's.access'])
-			->from('dav_shares', 's')
-			->join('s', 'addressbooks', 'a', $query->expr()->eq('s.resourceid', 'a.id'))
-			->where($query->expr()->in('s.principaluri', $query->createParameter('principaluri')))
-			->andWhere($query->expr()->eq('s.type', $query->createParameter('type')))
-			->setParameter('type', 'addressbook')
-			->setParameter('principaluri', $principals, IQueryBuilder::PARAM_STR_ARRAY)
-			->execute();
-
-		$readOnlyPropertyName = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}read-only';
-		while ($row = $result->fetch()) {
-			if ($row['principaluri'] === $principalUri) {
-				continue;
-			}
-
-			$readOnly = (int)$row['access'] === Backend::ACCESS_READ;
-			if (isset($addressBooks[$row['id']])) {
-				if ($readOnly) {
-					// New share can not have more permissions then the old one.
-					continue;
-				}
-				if (isset($addressBooks[$row['id']][$readOnlyPropertyName]) &&
-					$addressBooks[$row['id']][$readOnlyPropertyName] === 0) {
-					// Old share is already read-write, no more permissions can be gained
-					continue;
-				}
-			}
-
-			[, $name] = \Sabre\Uri\split($row['principaluri']);
-			$uri = $row['uri'] . '_shared_by_' . $name;
-			$displayName = $row['displayname'] . ' (' . $this->getUserDisplayName($name) . ')';
-
-			$addressBooks[$row['id']] = [
-				'id' => $row['id'],
-				'uri' => $uri,
-				'principaluri' => $principalUriOriginal,
-				'{DAV:}displayname' => $displayName,
-				'{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
-				'{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
-				'{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
-				'{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}owner-principal' => $row['principaluri'],
-				$readOnlyPropertyName => $readOnly,
-			];
-
-			$this->addOwnerPrincipal($addressBooks[$row['id']]);
-		}
-		$result->closeCursor();
-
-		return array_values($addressBooks);
-	}
-
-	public function getUsersOwnAddressBooks($principalUri) {
-		$principalUri = $this->convertPrincipal($principalUri, true);
-		$query = $this->db->getQueryBuilder();
-		$query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
-			->from('addressbooks')
-			->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
-
-		$addressBooks = [];
-
-		$result = $query->execute();
-		while ($row = $result->fetch()) {
-			$addressBooks[$row['id']] = [
-				'id' => $row['id'],
-				'uri' => $row['uri'],
-				'principaluri' => $this->convertPrincipal($row['principaluri'], false),
-				'{DAV:}displayname' => $row['displayname'],
-				'{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
-				'{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
-				'{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
-			];
-
-			$this->addOwnerPrincipal($addressBooks[$row['id']]);
-		}
-		$result->closeCursor();
-
-		return array_values($addressBooks);
-	}
-
-	private function getUserDisplayName($uid) {
-		if (!isset($this->userDisplayNames[$uid])) {
-			$user = $this->userManager->get($uid);
-
-			if ($user instanceof IUser) {
-				$this->userDisplayNames[$uid] = $user->getDisplayName();
-			} else {
-				$this->userDisplayNames[$uid] = $uid;
-			}
-		}
-
-		return $this->userDisplayNames[$uid];
-	}
-
-	/**
-	 * @param int $addressBookId
-	 */
-	public function getAddressBookById(int $addressBookId): ?array {
-		$query = $this->db->getQueryBuilder();
-		$result = $query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
-			->from('addressbooks')
-			->where($query->expr()->eq('id', $query->createNamedParameter($addressBookId, IQueryBuilder::PARAM_INT)))
-			->executeQuery();
-		$row = $result->fetch();
-		$result->closeCursor();
-		if (!$row) {
-			return null;
-		}
-
-		$addressBook = [
-			'id' => $row['id'],
-			'uri' => $row['uri'],
-			'principaluri' => $row['principaluri'],
-			'{DAV:}displayname' => $row['displayname'],
-			'{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
-			'{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
-			'{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
-		];
-
-		$this->addOwnerPrincipal($addressBook);
-
-		return $addressBook;
-	}
-
-	public function getAddressBooksByUri(string $principal, string $addressBookUri): ?array {
-		$query = $this->db->getQueryBuilder();
-		$result = $query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
-			->from('addressbooks')
-			->where($query->expr()->eq('uri', $query->createNamedParameter($addressBookUri)))
-			->andWhere($query->expr()->eq('principaluri', $query->createNamedParameter($principal)))
-			->setMaxResults(1)
-			->executeQuery();
-
-		$row = $result->fetch();
-		$result->closeCursor();
-		if ($row === false) {
-			return null;
-		}
-
-		$addressBook = [
-			'id' => $row['id'],
-			'uri' => $row['uri'],
-			'principaluri' => $row['principaluri'],
-			'{DAV:}displayname' => $row['displayname'],
-			'{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
-			'{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
-			'{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
-		];
-
-		$this->addOwnerPrincipal($addressBook);
-
-		return $addressBook;
-	}
-
-	/**
-	 * Updates properties for an address book.
-	 *
-	 * The list of mutations is stored in a Sabre\DAV\PropPatch object.
-	 * To do the actual updates, you must tell this object which properties
-	 * you're going to process with the handle() method.
-	 *
-	 * Calling the handle method is like telling the PropPatch object "I
-	 * promise I can handle updating this property".
-	 *
-	 * Read the PropPatch documentation for more info and examples.
-	 *
-	 * @param string $addressBookId
-	 * @param \Sabre\DAV\PropPatch $propPatch
-	 * @return void
-	 */
-	public function updateAddressBook($addressBookId, \Sabre\DAV\PropPatch $propPatch) {
-		$supportedProperties = [
-			'{DAV:}displayname',
-			'{' . Plugin::NS_CARDDAV . '}addressbook-description',
-		];
-
-		$propPatch->handle($supportedProperties, function ($mutations) use ($addressBookId) {
-			$updates = [];
-			foreach ($mutations as $property => $newValue) {
-				switch ($property) {
-					case '{DAV:}displayname':
-						$updates['displayname'] = $newValue;
-						break;
-					case '{' . Plugin::NS_CARDDAV . '}addressbook-description':
-						$updates['description'] = $newValue;
-						break;
-				}
-			}
-			$query = $this->db->getQueryBuilder();
-			$query->update('addressbooks');
-
-			foreach ($updates as $key => $value) {
-				$query->set($key, $query->createNamedParameter($value));
-			}
-			$query->where($query->expr()->eq('id', $query->createNamedParameter($addressBookId)))
-				->executeStatement();
-
-			$this->addChange($addressBookId, "", 2);
-
-			$addressBookRow = $this->getAddressBookById((int)$addressBookId);
-			$shares = $this->getShares((int)$addressBookId);
-			$this->dispatcher->dispatchTyped(new AddressBookUpdatedEvent((int)$addressBookId, $addressBookRow, $shares, $mutations));
-
-			return true;
-		});
-	}
-
-	/**
-	 * Creates a new address book
-	 *
-	 * @param string $principalUri
-	 * @param string $url Just the 'basename' of the url.
-	 * @param array $properties
-	 * @return int
-	 * @throws BadRequest
-	 */
-	public function createAddressBook($principalUri, $url, array $properties) {
-		$values = [
-			'displayname' => null,
-			'description' => null,
-			'principaluri' => $principalUri,
-			'uri' => $url,
-			'synctoken' => 1
-		];
-
-		foreach ($properties as $property => $newValue) {
-			switch ($property) {
-				case '{DAV:}displayname':
-					$values['displayname'] = $newValue;
-					break;
-				case '{' . Plugin::NS_CARDDAV . '}addressbook-description':
-					$values['description'] = $newValue;
-					break;
-				default:
-					throw new BadRequest('Unknown property: ' . $property);
-			}
-		}
-
-		// Fallback to make sure the displayname is set. Some clients may refuse
-		// to work with addressbooks not having a displayname.
-		if (is_null($values['displayname'])) {
-			$values['displayname'] = $url;
-		}
-
-		$query = $this->db->getQueryBuilder();
-		$query->insert('addressbooks')
-			->values([
-				'uri' => $query->createParameter('uri'),
-				'displayname' => $query->createParameter('displayname'),
-				'description' => $query->createParameter('description'),
-				'principaluri' => $query->createParameter('principaluri'),
-				'synctoken' => $query->createParameter('synctoken'),
-			])
-			->setParameters($values)
-			->execute();
-
-		$addressBookId = $query->getLastInsertId();
-		$addressBookRow = $this->getAddressBookById($addressBookId);
-		$this->dispatcher->dispatchTyped(new AddressBookCreatedEvent($addressBookId, $addressBookRow));
-
-		return $addressBookId;
-	}
-
-	/**
-	 * Deletes an entire addressbook and all its contents
-	 *
-	 * @param mixed $addressBookId
-	 * @return void
-	 */
-	public function deleteAddressBook($addressBookId) {
-		$addressBookId = (int)$addressBookId;
-		$addressBookData = $this->getAddressBookById($addressBookId);
-		$shares = $this->getShares($addressBookId);
-
-		$query = $this->db->getQueryBuilder();
-		$query->delete($this->dbCardsTable)
-			->where($query->expr()->eq('addressbookid', $query->createParameter('addressbookid')))
-			->setParameter('addressbookid', $addressBookId, IQueryBuilder::PARAM_INT)
-			->executeStatement();
-
-		$query->delete('addressbookchanges')
-			->where($query->expr()->eq('addressbookid', $query->createParameter('addressbookid')))
-			->setParameter('addressbookid', $addressBookId, IQueryBuilder::PARAM_INT)
-			->executeStatement();
-
-		$query->delete('addressbooks')
-			->where($query->expr()->eq('id', $query->createParameter('id')))
-			->setParameter('id', $addressBookId, IQueryBuilder::PARAM_INT)
-			->executeStatement();
-
-		$this->sharingBackend->deleteAllShares($addressBookId);
-
-		$query->delete($this->dbCardsPropertiesTable)
-			->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId, IQueryBuilder::PARAM_INT)))
-			->executeStatement();
-
-		if ($addressBookData) {
-			$this->dispatcher->dispatchTyped(new AddressBookDeletedEvent($addressBookId, $addressBookData, $shares));
-		}
-	}
-
-	/**
-	 * Returns all cards for a specific addressbook id.
-	 *
-	 * This method should return the following properties for each card:
-	 *   * carddata - raw vcard data
-	 *   * uri - Some unique url
-	 *   * lastmodified - A unix timestamp
-	 *
-	 * It's recommended to also return the following properties:
-	 *   * etag - A unique etag. This must change every time the card changes.
-	 *   * size - The size of the card in bytes.
-	 *
-	 * If these last two properties are provided, less time will be spent
-	 * calculating them. If they are specified, you can also omit carddata.
-	 * This may speed up certain requests, especially with large cards.
-	 *
-	 * @param mixed $addressbookId
-	 * @return array
-	 */
-	public function getCards($addressbookId) {
-		$query = $this->db->getQueryBuilder();
-		$query->select(['id', 'uri', 'lastmodified', 'etag', 'size', 'carddata', 'uid'])
-			->from($this->dbCardsTable)
-			->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressbookId)));
-
-		$cards = [];
-
-		$result = $query->execute();
-		while ($row = $result->fetch()) {
-			$row['etag'] = '"' . $row['etag'] . '"';
-
-			$modified = false;
-			$row['carddata'] = $this->readBlob($row['carddata'], $modified);
-			if ($modified) {
-				$row['size'] = strlen($row['carddata']);
-			}
-
-			$cards[] = $row;
-		}
-		$result->closeCursor();
-
-		return $cards;
-	}
-
-	/**
-	 * Returns a specific card.
-	 *
-	 * The same set of properties must be returned as with getCards. The only
-	 * exception is that 'carddata' is absolutely required.
-	 *
-	 * If the card does not exist, you must return false.
-	 *
-	 * @param mixed $addressBookId
-	 * @param string $cardUri
-	 * @return array
-	 */
-	public function getCard($addressBookId, $cardUri) {
-		$query = $this->db->getQueryBuilder();
-		$query->select(['id', 'uri', 'lastmodified', 'etag', 'size', 'carddata', 'uid'])
-			->from($this->dbCardsTable)
-			->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
-			->andWhere($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
-			->setMaxResults(1);
-
-		$result = $query->execute();
-		$row = $result->fetch();
-		if (!$row) {
-			return false;
-		}
-		$row['etag'] = '"' . $row['etag'] . '"';
-
-		$modified = false;
-		$row['carddata'] = $this->readBlob($row['carddata'], $modified);
-		if ($modified) {
-			$row['size'] = strlen($row['carddata']);
-		}
-
-		return $row;
-	}
-
-	/**
-	 * Returns a list of cards.
-	 *
-	 * This method should work identical to getCard, but instead return all the
-	 * cards in the list as an array.
-	 *
-	 * If the backend supports this, it may allow for some speed-ups.
-	 *
-	 * @param mixed $addressBookId
-	 * @param array $uris
-	 * @return array
-	 */
-	public function getMultipleCards($addressBookId, array $uris) {
-		if (empty($uris)) {
-			return [];
-		}
-
-		$chunks = array_chunk($uris, 100);
-		$cards = [];
-
-		$query = $this->db->getQueryBuilder();
-		$query->select(['id', 'uri', 'lastmodified', 'etag', 'size', 'carddata', 'uid'])
-			->from($this->dbCardsTable)
-			->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
-			->andWhere($query->expr()->in('uri', $query->createParameter('uri')));
-
-		foreach ($chunks as $uris) {
-			$query->setParameter('uri', $uris, IQueryBuilder::PARAM_STR_ARRAY);
-			$result = $query->execute();
-
-			while ($row = $result->fetch()) {
-				$row['etag'] = '"' . $row['etag'] . '"';
-
-				$modified = false;
-				$row['carddata'] = $this->readBlob($row['carddata'], $modified);
-				if ($modified) {
-					$row['size'] = strlen($row['carddata']);
-				}
-
-				$cards[] = $row;
-			}
-			$result->closeCursor();
-		}
-		return $cards;
-	}
-
-	/**
-	 * Creates a new card.
-	 *
-	 * The addressbook id will be passed as the first argument. This is the
-	 * same id as it is returned from the getAddressBooksForUser method.
-	 *
-	 * The cardUri is a base uri, and doesn't include the full path. The
-	 * cardData argument is the vcard body, and is passed as a string.
-	 *
-	 * It is possible to return an ETag from this method. This ETag is for the
-	 * newly created resource, and must be enclosed with double quotes (that
-	 * is, the string itself must contain the double quotes).
-	 *
-	 * You should only return the ETag if you store the carddata as-is. If a
-	 * subsequent GET request on the same card does not have the same body,
-	 * byte-by-byte and you did return an ETag here, clients tend to get
-	 * confused.
-	 *
-	 * If you don't return an ETag, you can just return null.
-	 *
-	 * @param mixed $addressBookId
-	 * @param string $cardUri
-	 * @param string $cardData
-	 * @param bool $checkAlreadyExists
-	 * @return string
-	 */
-	public function createCard($addressBookId, $cardUri, $cardData, bool $checkAlreadyExists = true) {
-		$etag = md5($cardData);
-		$uid = $this->getUID($cardData);
-
-		if ($checkAlreadyExists) {
-			$q = $this->db->getQueryBuilder();
-			$q->select('uid')
-				->from($this->dbCardsTable)
-				->where($q->expr()->eq('addressbookid', $q->createNamedParameter($addressBookId)))
-				->andWhere($q->expr()->eq('uid', $q->createNamedParameter($uid)))
-				->setMaxResults(1);
-			$result = $q->executeQuery();
-			$count = (bool)$result->fetchOne();
-			$result->closeCursor();
-			if ($count) {
-				throw new \Sabre\DAV\Exception\BadRequest('VCard object with uid already exists in this addressbook collection.');
-			}
-		}
-
-		$query = $this->db->getQueryBuilder();
-		$query->insert('cards')
-			->values([
-				'carddata' => $query->createNamedParameter($cardData, IQueryBuilder::PARAM_LOB),
-				'uri' => $query->createNamedParameter($cardUri),
-				'lastmodified' => $query->createNamedParameter(time()),
-				'addressbookid' => $query->createNamedParameter($addressBookId),
-				'size' => $query->createNamedParameter(strlen($cardData)),
-				'etag' => $query->createNamedParameter($etag),
-				'uid' => $query->createNamedParameter($uid),
-			])
-			->execute();
-
-		$etagCacheKey = "$addressBookId#$cardUri";
-		$this->etagCache[$etagCacheKey] = $etag;
-
-		$this->addChange($addressBookId, $cardUri, 1);
-		$this->updateProperties($addressBookId, $cardUri, $cardData);
-
-		$addressBookData = $this->getAddressBookById($addressBookId);
-		$shares = $this->getShares($addressBookId);
-		$objectRow = $this->getCard($addressBookId, $cardUri);
-		$this->dispatcher->dispatchTyped(new CardCreatedEvent($addressBookId, $addressBookData, $shares, $objectRow));
-
-		return '"' . $etag . '"';
-	}
-
-	/**
-	 * Updates a card.
-	 *
-	 * The addressbook id will be passed as the first argument. This is the
-	 * same id as it is returned from the getAddressBooksForUser method.
-	 *
-	 * The cardUri is a base uri, and doesn't include the full path. The
-	 * cardData argument is the vcard body, and is passed as a string.
-	 *
-	 * It is possible to return an ETag from this method. This ETag should
-	 * match that of the updated resource, and must be enclosed with double
-	 * quotes (that is: the string itself must contain the actual quotes).
-	 *
-	 * You should only return the ETag if you store the carddata as-is. If a
-	 * subsequent GET request on the same card does not have the same body,
-	 * byte-by-byte and you did return an ETag here, clients tend to get
-	 * confused.
-	 *
-	 * If you don't return an ETag, you can just return null.
-	 *
-	 * @param mixed $addressBookId
-	 * @param string $cardUri
-	 * @param string $cardData
-	 * @return string
-	 */
-	public function updateCard($addressBookId, $cardUri, $cardData) {
-		$uid = $this->getUID($cardData);
-		$etag = md5($cardData);
-		$query = $this->db->getQueryBuilder();
-
-		// check for recently stored etag and stop if it is the same
-		$etagCacheKey = "$addressBookId#$cardUri";
-		if (isset($this->etagCache[$etagCacheKey]) && $this->etagCache[$etagCacheKey] === $etag) {
-			return '"' . $etag . '"';
-		}
-
-		$query->update($this->dbCardsTable)
-			->set('carddata', $query->createNamedParameter($cardData, IQueryBuilder::PARAM_LOB))
-			->set('lastmodified', $query->createNamedParameter(time()))
-			->set('size', $query->createNamedParameter(strlen($cardData)))
-			->set('etag', $query->createNamedParameter($etag))
-			->set('uid', $query->createNamedParameter($uid))
-			->where($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
-			->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
-			->execute();
-
-		$this->etagCache[$etagCacheKey] = $etag;
-
-		$this->addChange($addressBookId, $cardUri, 2);
-		$this->updateProperties($addressBookId, $cardUri, $cardData);
-
-		$addressBookData = $this->getAddressBookById($addressBookId);
-		$shares = $this->getShares($addressBookId);
-		$objectRow = $this->getCard($addressBookId, $cardUri);
-		$this->dispatcher->dispatchTyped(new CardUpdatedEvent($addressBookId, $addressBookData, $shares, $objectRow));
-		return '"' . $etag . '"';
-	}
-
-	/**
-	 * Deletes a card
-	 *
-	 * @param mixed $addressBookId
-	 * @param string $cardUri
-	 * @return bool
-	 */
-	public function deleteCard($addressBookId, $cardUri) {
-		$addressBookData = $this->getAddressBookById($addressBookId);
-		$shares = $this->getShares($addressBookId);
-		$objectRow = $this->getCard($addressBookId, $cardUri);
-
-		try {
-			$cardId = $this->getCardId($addressBookId, $cardUri);
-		} catch (\InvalidArgumentException $e) {
-			$cardId = null;
-		}
-		$query = $this->db->getQueryBuilder();
-		$ret = $query->delete($this->dbCardsTable)
-			->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
-			->andWhere($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
-			->executeStatement();
-
-		$this->addChange($addressBookId, $cardUri, 3);
-
-		if ($ret === 1) {
-			if ($cardId !== null) {
-				$this->dispatcher->dispatchTyped(new CardDeletedEvent($addressBookId, $addressBookData, $shares, $objectRow));
-				$this->purgeProperties($addressBookId, $cardId);
-			}
-			return true;
-		}
-
-		return false;
-	}
-
-	/**
-	 * The getChanges method returns all the changes that have happened, since
-	 * the specified syncToken in the specified address book.
-	 *
-	 * This function should return an array, such as the following:
-	 *
-	 * [
-	 *   'syncToken' => 'The current synctoken',
-	 *   'added'   => [
-	 *      'new.txt',
-	 *   ],
-	 *   'modified'   => [
-	 *      'modified.txt',
-	 *   ],
-	 *   'deleted' => [
-	 *      'foo.php.bak',
-	 *      'old.txt'
-	 *   ]
-	 * ];
-	 *
-	 * The returned syncToken property should reflect the *current* syncToken
-	 * of the calendar, as reported in the {http://sabredav.org/ns}sync-token
-	 * property. This is needed here too, to ensure the operation is atomic.
-	 *
-	 * If the $syncToken argument is specified as null, this is an initial
-	 * sync, and all members should be reported.
-	 *
-	 * The modified property is an array of nodenames that have changed since
-	 * the last token.
-	 *
-	 * The deleted property is an array with nodenames, that have been deleted
-	 * from collection.
-	 *
-	 * The $syncLevel argument is basically the 'depth' of the report. If it's
-	 * 1, you only have to report changes that happened only directly in
-	 * immediate descendants. If it's 2, it should also include changes from
-	 * the nodes below the child collections. (grandchildren)
-	 *
-	 * The $limit argument allows a client to specify how many results should
-	 * be returned at most. If the limit is not specified, it should be treated
-	 * as infinite.
-	 *
-	 * If the limit (infinite or not) is higher than you're willing to return,
-	 * you should throw a Sabre\DAV\Exception\TooMuchMatches() exception.
-	 *
-	 * If the syncToken is expired (due to data cleanup) or unknown, you must
-	 * return null.
-	 *
-	 * The limit is 'suggestive'. You are free to ignore it.
-	 *
-	 * @param string $addressBookId
-	 * @param string $syncToken
-	 * @param int $syncLevel
-	 * @param int|null $limit
-	 * @return array
-	 */
-	public function getChangesForAddressBook($addressBookId, $syncToken, $syncLevel, $limit = null) {
-		// Current synctoken
-		$qb = $this->db->getQueryBuilder();
-		$qb->select('synctoken')
-			->from('addressbooks')
-			->where(
-				$qb->expr()->eq('id', $qb->createNamedParameter($addressBookId))
-			);
-		$stmt = $qb->executeQuery();
-		$currentToken = $stmt->fetchOne();
-		$stmt->closeCursor();
-
-		if (is_null($currentToken)) {
-			return [];
-		}
-
-		$result = [
-			'syncToken' => $currentToken,
-			'added' => [],
-			'modified' => [],
-			'deleted' => [],
-		];
-
-		if ($syncToken) {
-			$qb = $this->db->getQueryBuilder();
-			$qb->select('uri', 'operation')
-				->from('addressbookchanges')
-				->where(
-					$qb->expr()->andX(
-						$qb->expr()->gte('synctoken', $qb->createNamedParameter($syncToken)),
-						$qb->expr()->lt('synctoken', $qb->createNamedParameter($currentToken)),
-						$qb->expr()->eq('addressbookid', $qb->createNamedParameter($addressBookId))
-					)
-				)->orderBy('synctoken');
-
-			if (is_int($limit) && $limit > 0) {
-				$qb->setMaxResults($limit);
-			}
-
-			// Fetching all changes
-			$stmt = $qb->executeQuery();
-
-			$changes = [];
-
-			// This loop ensures that any duplicates are overwritten, only the
-			// last change on a node is relevant.
-			while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
-				$changes[$row['uri']] = $row['operation'];
-			}
-			$stmt->closeCursor();
-
-			foreach ($changes as $uri => $operation) {
-				switch ($operation) {
-					case 1:
-						$result['added'][] = $uri;
-						break;
-					case 2:
-						$result['modified'][] = $uri;
-						break;
-					case 3:
-						$result['deleted'][] = $uri;
-						break;
-				}
-			}
-		} else {
-			$qb = $this->db->getQueryBuilder();
-			$qb->select('uri')
-				->from('cards')
-				->where(
-					$qb->expr()->eq('addressbookid', $qb->createNamedParameter($addressBookId))
-				);
-			// No synctoken supplied, this is the initial sync.
-			$stmt = $qb->executeQuery();
-			$result['added'] = $stmt->fetchAll(\PDO::FETCH_COLUMN);
-			$stmt->closeCursor();
-		}
-		return $result;
-	}
-
-	/**
-	 * Adds a change record to the addressbookchanges table.
-	 *
-	 * @param mixed $addressBookId
-	 * @param string $objectUri
-	 * @param int $operation 1 = add, 2 = modify, 3 = delete
-	 * @return void
-	 */
-	protected function addChange($addressBookId, $objectUri, $operation) {
-		$sql = 'INSERT INTO `*PREFIX*addressbookchanges`(`uri`, `synctoken`, `addressbookid`, `operation`) SELECT ?, `synctoken`, ?, ? FROM `*PREFIX*addressbooks` WHERE `id` = ?';
-		$stmt = $this->db->prepare($sql);
-		$stmt->execute([
-			$objectUri,
-			$addressBookId,
-			$operation,
-			$addressBookId
-		]);
-		$stmt = $this->db->prepare('UPDATE `*PREFIX*addressbooks` SET `synctoken` = `synctoken` + 1 WHERE `id` = ?');
-		$stmt->execute([
-			$addressBookId
-		]);
-	}
-
-	/**
-	 * @param resource|string $cardData
-	 * @param bool $modified
-	 * @return string
-	 */
-	private function readBlob($cardData, &$modified = false) {
-		if (is_resource($cardData)) {
-			$cardData = stream_get_contents($cardData);
-		}
-
-		// Micro optimisation
-		// don't loop through
-		if (strpos($cardData, 'PHOTO:data:') === 0) {
-			return $cardData;
-		}
-
-		$cardDataArray = explode("\r\n", $cardData);
-
-		$cardDataFiltered = [];
-		$removingPhoto = false;
-		foreach ($cardDataArray as $line) {
-			if (strpos($line, 'PHOTO:data:') === 0
-				&& strpos($line, 'PHOTO:data:image/') !== 0) {
-				// Filter out PHOTO data of non-images
-				$removingPhoto = true;
-				$modified = true;
-				continue;
-			}
-
-			if ($removingPhoto) {
-				if (strpos($line, ' ') === 0) {
-					continue;
-				}
-				// No leading space means this is a new property
-				$removingPhoto = false;
-			}
-
-			$cardDataFiltered[] = $line;
-		}
-		return implode("\r\n", $cardDataFiltered);
-	}
-
-	/**
-	 * @param list<array{href: string, commonName: string, readOnly: bool}> $add
-	 * @param list<string> $remove
-	 */
-	public function updateShares(IShareable $shareable, array $add, array $remove): void {
-		$addressBookId = $shareable->getResourceId();
-		$addressBookData = $this->getAddressBookById($addressBookId);
-		$oldShares = $this->getShares($addressBookId);
-
-		$this->sharingBackend->updateShares($shareable, $add, $remove);
-
-		$this->dispatcher->dispatchTyped(new AddressBookShareUpdatedEvent($addressBookId, $addressBookData, $oldShares, $add, $remove));
-	}
-
-	/**
-	 * Search contacts in a specific address-book
-	 *
-	 * @param int $addressBookId
-	 * @param string $pattern which should match within the $searchProperties
-	 * @param array $searchProperties defines the properties within the query pattern should match
-	 * @param array $options = array() to define the search behavior
-	 *    - 'escape_like_param' - If set to false wildcards _ and % are not escaped, otherwise they are
-	 *    - 'limit' - Set a numeric limit for the search results
-	 *    - 'offset' - Set the offset for the limited search results
-	 *    - 'wildcard' - Whether the search should use wildcards
-	 * @psalm-param array{escape_like_param?: bool, limit?: int, offset?: int, wildcard?: bool} $options
-	 * @return array an array of contacts which are arrays of key-value-pairs
-	 */
-	public function search($addressBookId, $pattern, $searchProperties, $options = []): array {
-		return $this->searchByAddressBookIds([$addressBookId], $pattern, $searchProperties, $options);
-	}
-
-	/**
-	 * Search contacts in all address-books accessible by a user
-	 *
-	 * @param string $principalUri
-	 * @param string $pattern
-	 * @param array $searchProperties
-	 * @param array $options
-	 * @return array
-	 */
-	public function searchPrincipalUri(string $principalUri,
-									   string $pattern,
-									   array $searchProperties,
-									   array $options = []): array {
-		$addressBookIds = array_map(static function ($row):int {
-			return (int) $row['id'];
-		}, $this->getAddressBooksForUser($principalUri));
-
-		return $this->searchByAddressBookIds($addressBookIds, $pattern, $searchProperties, $options);
-	}
-
-	/**
-	 * @param array $addressBookIds
-	 * @param string $pattern
-	 * @param array $searchProperties
-	 * @param array $options
-	 * @psalm-param array{types?: bool, escape_like_param?: bool, limit?: int, offset?: int, wildcard?: bool} $options
-	 * @return array
-	 */
-	private function searchByAddressBookIds(array $addressBookIds,
-											string $pattern,
-											array $searchProperties,
-											array $options = []): array {
-		$escapePattern = !\array_key_exists('escape_like_param', $options) || $options['escape_like_param'] !== false;
-		$useWildcards = !\array_key_exists('wildcard', $options) || $options['wildcard'] !== false;
-
-		$query2 = $this->db->getQueryBuilder();
-
-		$addressBookOr = $query2->expr()->orX();
-		foreach ($addressBookIds as $addressBookId) {
-			$addressBookOr->add($query2->expr()->eq('cp.addressbookid', $query2->createNamedParameter($addressBookId)));
-		}
-
-		if ($addressBookOr->count() === 0) {
-			return [];
-		}
-
-		$propertyOr = $query2->expr()->orX();
-		foreach ($searchProperties as $property) {
-			if ($escapePattern) {
-				if ($property === 'EMAIL' && strpos($pattern, ' ') !== false) {
-					// There can be no spaces in emails
-					continue;
-				}
-
-				if ($property === 'CLOUD' && preg_match('/[^a-zA-Z0-9 :_.@\/\-\']/', $pattern) === 1) {
-					// There can be no chars in cloud ids which are not valid for user ids plus :/
-					// worst case: CA61590A-BBBC-423E-84AF-E6DF01455A53@https://my.nxt/srv/
-					continue;
-				}
-			}
-
-			$propertyOr->add($query2->expr()->eq('cp.name', $query2->createNamedParameter($property)));
-		}
-
-		if ($propertyOr->count() === 0) {
-			return [];
-		}
-
-		$query2->selectDistinct('cp.cardid')
-			->from($this->dbCardsPropertiesTable, 'cp')
-			->andWhere($addressBookOr)
-			->andWhere($propertyOr);
-
-		// No need for like when the pattern is empty
-		if ('' !== $pattern) {
-			if (!$useWildcards) {
-				$query2->andWhere($query2->expr()->eq('cp.value', $query2->createNamedParameter($pattern)));
-			} elseif (!$escapePattern) {
-				$query2->andWhere($query2->expr()->ilike('cp.value', $query2->createNamedParameter($pattern)));
-			} else {
-				$query2->andWhere($query2->expr()->ilike('cp.value', $query2->createNamedParameter('%' . $this->db->escapeLikeParameter($pattern) . '%')));
-			}
-		}
-
-		if (isset($options['limit'])) {
-			$query2->setMaxResults($options['limit']);
-		}
-		if (isset($options['offset'])) {
-			$query2->setFirstResult($options['offset']);
-		}
-
-		$result = $query2->execute();
-		$matches = $result->fetchAll();
-		$result->closeCursor();
-		$matches = array_map(function ($match) {
-			return (int)$match['cardid'];
-		}, $matches);
-
-		$cards = [];
-		$query = $this->db->getQueryBuilder();
-		$query->select('c.addressbookid', 'c.carddata', 'c.uri')
-			->from($this->dbCardsTable, 'c')
-			->where($query->expr()->in('c.id', $query->createParameter('matches')));
-
-		foreach (array_chunk($matches, 1000) as $matchesChunk) {
-			$query->setParameter('matches', $matchesChunk, IQueryBuilder::PARAM_INT_ARRAY);
-			$result = $query->executeQuery();
-			$cards = array_merge($cards, $result->fetchAll());
-			$result->closeCursor();
-		}
-
-		return array_map(function ($array) {
-			$array['addressbookid'] = (int) $array['addressbookid'];
-			$modified = false;
-			$array['carddata'] = $this->readBlob($array['carddata'], $modified);
-			if ($modified) {
-				$array['size'] = strlen($array['carddata']);
-			}
-			return $array;
-		}, $cards);
-	}
-
-	/**
-	 * @param int $bookId
-	 * @param string $name
-	 * @return array
-	 */
-	public function collectCardProperties($bookId, $name) {
-		$query = $this->db->getQueryBuilder();
-		$result = $query->selectDistinct('value')
-			->from($this->dbCardsPropertiesTable)
-			->where($query->expr()->eq('name', $query->createNamedParameter($name)))
-			->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($bookId)))
-			->execute();
-
-		$all = $result->fetchAll(PDO::FETCH_COLUMN);
-		$result->closeCursor();
-
-		return $all;
-	}
-
-	/**
-	 * get URI from a given contact
-	 *
-	 * @param int $id
-	 * @return string
-	 */
-	public function getCardUri($id) {
-		$query = $this->db->getQueryBuilder();
-		$query->select('uri')->from($this->dbCardsTable)
-			->where($query->expr()->eq('id', $query->createParameter('id')))
-			->setParameter('id', $id);
-
-		$result = $query->execute();
-		$uri = $result->fetch();
-		$result->closeCursor();
-
-		if (!isset($uri['uri'])) {
-			throw new \InvalidArgumentException('Card does not exists: ' . $id);
-		}
-
-		return $uri['uri'];
-	}
-
-	/**
-	 * return contact with the given URI
-	 *
-	 * @param int $addressBookId
-	 * @param string $uri
-	 * @returns array
-	 */
-	public function getContact($addressBookId, $uri) {
-		$result = [];
-		$query = $this->db->getQueryBuilder();
-		$query->select('*')->from($this->dbCardsTable)
-			->where($query->expr()->eq('uri', $query->createNamedParameter($uri)))
-			->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
-		$queryResult = $query->execute();
-		$contact = $queryResult->fetch();
-		$queryResult->closeCursor();
-
-		if (is_array($contact)) {
-			$modified = false;
-			$contact['etag'] = '"' . $contact['etag'] . '"';
-			$contact['carddata'] = $this->readBlob($contact['carddata'], $modified);
-			if ($modified) {
-				$contact['size'] = strlen($contact['carddata']);
-			}
-
-			$result = $contact;
-		}
-
-		return $result;
-	}
-
-	/**
-	 * Returns the list of people whom this address book is shared with.
-	 *
-	 * Every element in this array should have the following properties:
-	 *   * href - Often a mailto: address
-	 *   * commonName - Optional, for example a first + last name
-	 *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
-	 *   * readOnly - boolean
-	 *
-	 * @return list<array{href: string, commonName: string, status: int, readOnly: bool, '{http://owncloud.org/ns}principal': string, '{http://owncloud.org/ns}group-share': bool}>
-	 */
-	public function getShares(int $addressBookId): array {
-		return $this->sharingBackend->getShares($addressBookId);
-	}
-
-	/**
-	 * update properties table
-	 *
-	 * @param int $addressBookId
-	 * @param string $cardUri
-	 * @param string $vCardSerialized
-	 */
-	protected function updateProperties($addressBookId, $cardUri, $vCardSerialized) {
-		$cardId = $this->getCardId($addressBookId, $cardUri);
-		$vCard = $this->readCard($vCardSerialized);
-
-		$this->purgeProperties($addressBookId, $cardId);
-
-		$query = $this->db->getQueryBuilder();
-		$query->insert($this->dbCardsPropertiesTable)
-			->values(
-				[
-					'addressbookid' => $query->createNamedParameter($addressBookId),
-					'cardid' => $query->createNamedParameter($cardId),
-					'name' => $query->createParameter('name'),
-					'value' => $query->createParameter('value'),
-					'preferred' => $query->createParameter('preferred')
-				]
-			);
-
-
-		$this->db->beginTransaction();
-
-		try {
-			foreach ($vCard->children() as $property) {
-				if (!in_array($property->name, self::$indexProperties)) {
-					continue;
-				}
-				$preferred = 0;
-				foreach ($property->parameters as $parameter) {
-					if ($parameter->name === 'TYPE' && strtoupper($parameter->getValue()) === 'PREF') {
-						$preferred = 1;
-						break;
-					}
-				}
-				$query->setParameter('name', $property->name);
-				$query->setParameter('value', mb_strcut($property->getValue(), 0, 254));
-				$query->setParameter('preferred', $preferred);
-				$query->execute();
-			}
-			$this->db->commit();
-		} catch (\Exception $e) {
-			$this->db->rollBack();
-		}
-	}
-
-	/**
-	 * read vCard data into a vCard object
-	 *
-	 * @param string $cardData
-	 * @return VCard
-	 */
-	protected function readCard($cardData) {
-		return Reader::read($cardData);
-	}
-
-	/**
-	 * delete all properties from a given card
-	 *
-	 * @param int $addressBookId
-	 * @param int $cardId
-	 */
-	protected function purgeProperties($addressBookId, $cardId) {
-		$query = $this->db->getQueryBuilder();
-		$query->delete($this->dbCardsPropertiesTable)
-			->where($query->expr()->eq('cardid', $query->createNamedParameter($cardId)))
-			->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
-		$query->execute();
-	}
-
-	/**
-	 * Get ID from a given contact
-	 */
-	protected function getCardId(int $addressBookId, string $uri): int {
-		$query = $this->db->getQueryBuilder();
-		$query->select('id')->from($this->dbCardsTable)
-			->where($query->expr()->eq('uri', $query->createNamedParameter($uri)))
-			->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
-
-		$result = $query->execute();
-		$cardIds = $result->fetch();
-		$result->closeCursor();
-
-		if (!isset($cardIds['id'])) {
-			throw new \InvalidArgumentException('Card does not exists: ' . $uri);
-		}
-
-		return (int)$cardIds['id'];
-	}
-
-	/**
-	 * For shared address books the sharee is set in the ACL of the address book
-	 *
-	 * @param int $addressBookId
-	 * @param list<array{privilege: string, principal: string, protected: bool}> $acl
-	 * @return list<array{privilege: string, principal: string, protected: bool}>
-	 */
-	public function applyShareAcl(int $addressBookId, array $acl): array {
-		return $this->sharingBackend->applyShareAcl($addressBookId, $acl);
-	}
-
-	private function convertPrincipal(string $principalUri, bool $toV2): string {
-		if ($this->principalBackend->getPrincipalPrefix() === 'principals') {
-			[, $name] = \Sabre\Uri\split($principalUri);
-			if ($toV2 === true) {
-				return "principals/users/$name";
-			}
-			return "principals/$name";
-		}
-		return $principalUri;
-	}
-
-	private function addOwnerPrincipal(array &$addressbookInfo): void {
-		$ownerPrincipalKey = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}owner-principal';
-		$displaynameKey = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD . '}owner-displayname';
-		if (isset($addressbookInfo[$ownerPrincipalKey])) {
-			$uri = $addressbookInfo[$ownerPrincipalKey];
-		} else {
-			$uri = $addressbookInfo['principaluri'];
-		}
-
-		$principalInformation = $this->principalBackend->getPrincipalByPath($uri);
-		if (isset($principalInformation['{DAV:}displayname'])) {
-			$addressbookInfo[$displaynameKey] = $principalInformation['{DAV:}displayname'];
-		}
-	}
-
-	/**
-	 * Extract UID from vcard
-	 *
-	 * @param string $cardData the vcard raw data
-	 * @return string the uid
-	 * @throws BadRequest if no UID is available or vcard is empty
-	 */
-	private function getUID(string $cardData): string {
-		if ($cardData !== '') {
-			$vCard = Reader::read($cardData);
-			if ($vCard->UID) {
-				$uid = $vCard->UID->getValue();
-				return $uid;
-			}
-			// should already be handled, but just in case
-			throw new BadRequest('vCards on CardDAV servers MUST have a UID property');
-		}
-		// should already be handled, but just in case
-		throw new BadRequest('vCard can not be empty');
-	}
+    public const PERSONAL_ADDRESSBOOK_URI = 'contacts';
+    public const PERSONAL_ADDRESSBOOK_NAME = 'Contacts';
+
+    private Principal $principalBackend;
+    private string $dbCardsTable = 'cards';
+    private string $dbCardsPropertiesTable = 'cards_properties';
+    private IDBConnection $db;
+    private Backend $sharingBackend;
+
+    /** @var array properties to index */
+    public static array $indexProperties = [
+        'BDAY', 'UID', 'N', 'FN', 'TITLE', 'ROLE', 'NOTE', 'NICKNAME',
+        'ORG', 'CATEGORIES', 'EMAIL', 'TEL', 'IMPP', 'ADR', 'URL', 'GEO',
+        'CLOUD', 'X-SOCIALPROFILE'];
+
+    /**
+     * @var string[] Map of uid => display name
+     */
+    protected array $userDisplayNames;
+    private IUserManager $userManager;
+    private IEventDispatcher $dispatcher;
+    private array $etagCache = [];
+
+    /**
+     * CardDavBackend constructor.
+     *
+     * @param IDBConnection $db
+     * @param Principal $principalBackend
+     * @param IUserManager $userManager
+     * @param IGroupManager $groupManager
+     * @param IEventDispatcher $dispatcher
+     */
+    public function __construct(IDBConnection $db,
+                                Principal $principalBackend,
+                                IUserManager $userManager,
+                                IGroupManager $groupManager,
+                                IEventDispatcher $dispatcher) {
+        $this->db = $db;
+        $this->principalBackend = $principalBackend;
+        $this->userManager = $userManager;
+        $this->dispatcher = $dispatcher;
+        $this->sharingBackend = new Backend($this->db, $this->userManager, $groupManager, $principalBackend, 'addressbook');
+    }
+
+    /**
+     * Return the number of address books for a principal
+     *
+     * @param $principalUri
+     * @return int
+     */
+    public function getAddressBooksForUserCount($principalUri) {
+        $principalUri = $this->convertPrincipal($principalUri, true);
+        $query = $this->db->getQueryBuilder();
+        $query->select($query->func()->count('*'))
+            ->from('addressbooks')
+            ->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
+
+        $result = $query->executeQuery();
+        $column = (int) $result->fetchOne();
+        $result->closeCursor();
+        return $column;
+    }
+
+    /**
+     * Returns the list of address books for a specific user.
+     *
+     * Every addressbook should have the following properties:
+     *   id - an arbitrary unique id
+     *   uri - the 'basename' part of the url
+     *   principaluri - Same as the passed parameter
+     *
+     * Any additional clark-notation property may be passed besides this. Some
+     * common ones are :
+     *   {DAV:}displayname
+     *   {urn:ietf:params:xml:ns:carddav}addressbook-description
+     *   {http://calendarserver.org/ns/}getctag
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    public function getAddressBooksForUser($principalUri) {
+        $principalUriOriginal = $principalUri;
+        $principalUri = $this->convertPrincipal($principalUri, true);
+        $query = $this->db->getQueryBuilder();
+        $query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
+            ->from('addressbooks')
+            ->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
+
+        $addressBooks = [];
+
+        $result = $query->execute();
+        while ($row = $result->fetch()) {
+            $addressBooks[$row['id']] = [
+                'id' => $row['id'],
+                'uri' => $row['uri'],
+                'principaluri' => $this->convertPrincipal($row['principaluri'], false),
+                '{DAV:}displayname' => $row['displayname'],
+                '{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
+                '{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
+                '{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
+            ];
+
+            $this->addOwnerPrincipal($addressBooks[$row['id']]);
+        }
+        $result->closeCursor();
+
+        // query for shared addressbooks
+        $principals = $this->principalBackend->getGroupMembership($principalUriOriginal, true);
+        $principals = array_merge($principals, $this->principalBackend->getCircleMembership($principalUriOriginal));
+
+        $principals[] = $principalUri;
+
+        $query = $this->db->getQueryBuilder();
+        $result = $query->select(['a.id', 'a.uri', 'a.displayname', 'a.principaluri', 'a.description', 'a.synctoken', 's.access'])
+            ->from('dav_shares', 's')
+            ->join('s', 'addressbooks', 'a', $query->expr()->eq('s.resourceid', 'a.id'))
+            ->where($query->expr()->in('s.principaluri', $query->createParameter('principaluri')))
+            ->andWhere($query->expr()->eq('s.type', $query->createParameter('type')))
+            ->setParameter('type', 'addressbook')
+            ->setParameter('principaluri', $principals, IQueryBuilder::PARAM_STR_ARRAY)
+            ->execute();
+
+        $readOnlyPropertyName = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}read-only';
+        while ($row = $result->fetch()) {
+            if ($row['principaluri'] === $principalUri) {
+                continue;
+            }
+
+            $readOnly = (int)$row['access'] === Backend::ACCESS_READ;
+            if (isset($addressBooks[$row['id']])) {
+                if ($readOnly) {
+                    // New share can not have more permissions then the old one.
+                    continue;
+                }
+                if (isset($addressBooks[$row['id']][$readOnlyPropertyName]) &&
+                    $addressBooks[$row['id']][$readOnlyPropertyName] === 0) {
+                    // Old share is already read-write, no more permissions can be gained
+                    continue;
+                }
+            }
+
+            [, $name] = \Sabre\Uri\split($row['principaluri']);
+            $uri = $row['uri'] . '_shared_by_' . $name;
+            $displayName = $row['displayname'] . ' (' . $this->getUserDisplayName($name) . ')';
+
+            $addressBooks[$row['id']] = [
+                'id' => $row['id'],
+                'uri' => $uri,
+                'principaluri' => $principalUriOriginal,
+                '{DAV:}displayname' => $displayName,
+                '{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
+                '{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
+                '{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
+                '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}owner-principal' => $row['principaluri'],
+                $readOnlyPropertyName => $readOnly,
+            ];
+
+            $this->addOwnerPrincipal($addressBooks[$row['id']]);
+        }
+        $result->closeCursor();
+
+        return array_values($addressBooks);
+    }
+
+    public function getUsersOwnAddressBooks($principalUri) {
+        $principalUri = $this->convertPrincipal($principalUri, true);
+        $query = $this->db->getQueryBuilder();
+        $query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
+            ->from('addressbooks')
+            ->where($query->expr()->eq('principaluri', $query->createNamedParameter($principalUri)));
+
+        $addressBooks = [];
+
+        $result = $query->execute();
+        while ($row = $result->fetch()) {
+            $addressBooks[$row['id']] = [
+                'id' => $row['id'],
+                'uri' => $row['uri'],
+                'principaluri' => $this->convertPrincipal($row['principaluri'], false),
+                '{DAV:}displayname' => $row['displayname'],
+                '{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
+                '{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
+                '{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
+            ];
+
+            $this->addOwnerPrincipal($addressBooks[$row['id']]);
+        }
+        $result->closeCursor();
+
+        return array_values($addressBooks);
+    }
+
+    private function getUserDisplayName($uid) {
+        if (!isset($this->userDisplayNames[$uid])) {
+            $user = $this->userManager->get($uid);
+
+            if ($user instanceof IUser) {
+                $this->userDisplayNames[$uid] = $user->getDisplayName();
+            } else {
+                $this->userDisplayNames[$uid] = $uid;
+            }
+        }
+
+        return $this->userDisplayNames[$uid];
+    }
+
+    /**
+     * @param int $addressBookId
+     */
+    public function getAddressBookById(int $addressBookId): ?array {
+        $query = $this->db->getQueryBuilder();
+        $result = $query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
+            ->from('addressbooks')
+            ->where($query->expr()->eq('id', $query->createNamedParameter($addressBookId, IQueryBuilder::PARAM_INT)))
+            ->executeQuery();
+        $row = $result->fetch();
+        $result->closeCursor();
+        if (!$row) {
+            return null;
+        }
+
+        $addressBook = [
+            'id' => $row['id'],
+            'uri' => $row['uri'],
+            'principaluri' => $row['principaluri'],
+            '{DAV:}displayname' => $row['displayname'],
+            '{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
+            '{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
+            '{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
+        ];
+
+        $this->addOwnerPrincipal($addressBook);
+
+        return $addressBook;
+    }
+
+    public function getAddressBooksByUri(string $principal, string $addressBookUri): ?array {
+        $query = $this->db->getQueryBuilder();
+        $result = $query->select(['id', 'uri', 'displayname', 'principaluri', 'description', 'synctoken'])
+            ->from('addressbooks')
+            ->where($query->expr()->eq('uri', $query->createNamedParameter($addressBookUri)))
+            ->andWhere($query->expr()->eq('principaluri', $query->createNamedParameter($principal)))
+            ->setMaxResults(1)
+            ->executeQuery();
+
+        $row = $result->fetch();
+        $result->closeCursor();
+        if ($row === false) {
+            return null;
+        }
+
+        $addressBook = [
+            'id' => $row['id'],
+            'uri' => $row['uri'],
+            'principaluri' => $row['principaluri'],
+            '{DAV:}displayname' => $row['displayname'],
+            '{' . Plugin::NS_CARDDAV . '}addressbook-description' => $row['description'],
+            '{http://calendarserver.org/ns/}getctag' => $row['synctoken'],
+            '{http://sabredav.org/ns}sync-token' => $row['synctoken'] ?: '0',
+        ];
+
+        $this->addOwnerPrincipal($addressBook);
+
+        return $addressBook;
+    }
+
+    /**
+     * Updates properties for an address book.
+     *
+     * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+     * To do the actual updates, you must tell this object which properties
+     * you're going to process with the handle() method.
+     *
+     * Calling the handle method is like telling the PropPatch object "I
+     * promise I can handle updating this property".
+     *
+     * Read the PropPatch documentation for more info and examples.
+     *
+     * @param string $addressBookId
+     * @param \Sabre\DAV\PropPatch $propPatch
+     * @return void
+     */
+    public function updateAddressBook($addressBookId, \Sabre\DAV\PropPatch $propPatch) {
+        $supportedProperties = [
+            '{DAV:}displayname',
+            '{' . Plugin::NS_CARDDAV . '}addressbook-description',
+        ];
+
+        $propPatch->handle($supportedProperties, function ($mutations) use ($addressBookId) {
+            $updates = [];
+            foreach ($mutations as $property => $newValue) {
+                switch ($property) {
+                    case '{DAV:}displayname':
+                        $updates['displayname'] = $newValue;
+                        break;
+                    case '{' . Plugin::NS_CARDDAV . '}addressbook-description':
+                        $updates['description'] = $newValue;
+                        break;
+                }
+            }
+            $query = $this->db->getQueryBuilder();
+            $query->update('addressbooks');
+
+            foreach ($updates as $key => $value) {
+                $query->set($key, $query->createNamedParameter($value));
+            }
+            $query->where($query->expr()->eq('id', $query->createNamedParameter($addressBookId)))
+                ->executeStatement();
+
+            $this->addChange($addressBookId, "", 2);
+
+            $addressBookRow = $this->getAddressBookById((int)$addressBookId);
+            $shares = $this->getShares((int)$addressBookId);
+            $this->dispatcher->dispatchTyped(new AddressBookUpdatedEvent((int)$addressBookId, $addressBookRow, $shares, $mutations));
+
+            return true;
+        });
+    }
+
+    /**
+     * Creates a new address book
+     *
+     * @param string $principalUri
+     * @param string $url Just the 'basename' of the url.
+     * @param array $properties
+     * @return int
+     * @throws BadRequest
+     */
+    public function createAddressBook($principalUri, $url, array $properties) {
+        $values = [
+            'displayname' => null,
+            'description' => null,
+            'principaluri' => $principalUri,
+            'uri' => $url,
+            'synctoken' => 1
+        ];
+
+        foreach ($properties as $property => $newValue) {
+            switch ($property) {
+                case '{DAV:}displayname':
+                    $values['displayname'] = $newValue;
+                    break;
+                case '{' . Plugin::NS_CARDDAV . '}addressbook-description':
+                    $values['description'] = $newValue;
+                    break;
+                default:
+                    throw new BadRequest('Unknown property: ' . $property);
+            }
+        }
+
+        // Fallback to make sure the displayname is set. Some clients may refuse
+        // to work with addressbooks not having a displayname.
+        if (is_null($values['displayname'])) {
+            $values['displayname'] = $url;
+        }
+
+        $query = $this->db->getQueryBuilder();
+        $query->insert('addressbooks')
+            ->values([
+                'uri' => $query->createParameter('uri'),
+                'displayname' => $query->createParameter('displayname'),
+                'description' => $query->createParameter('description'),
+                'principaluri' => $query->createParameter('principaluri'),
+                'synctoken' => $query->createParameter('synctoken'),
+            ])
+            ->setParameters($values)
+            ->execute();
+
+        $addressBookId = $query->getLastInsertId();
+        $addressBookRow = $this->getAddressBookById($addressBookId);
+        $this->dispatcher->dispatchTyped(new AddressBookCreatedEvent($addressBookId, $addressBookRow));
+
+        return $addressBookId;
+    }
+
+    /**
+     * Deletes an entire addressbook and all its contents
+     *
+     * @param mixed $addressBookId
+     * @return void
+     */
+    public function deleteAddressBook($addressBookId) {
+        $addressBookId = (int)$addressBookId;
+        $addressBookData = $this->getAddressBookById($addressBookId);
+        $shares = $this->getShares($addressBookId);
+
+        $query = $this->db->getQueryBuilder();
+        $query->delete($this->dbCardsTable)
+            ->where($query->expr()->eq('addressbookid', $query->createParameter('addressbookid')))
+            ->setParameter('addressbookid', $addressBookId, IQueryBuilder::PARAM_INT)
+            ->executeStatement();
+
+        $query->delete('addressbookchanges')
+            ->where($query->expr()->eq('addressbookid', $query->createParameter('addressbookid')))
+            ->setParameter('addressbookid', $addressBookId, IQueryBuilder::PARAM_INT)
+            ->executeStatement();
+
+        $query->delete('addressbooks')
+            ->where($query->expr()->eq('id', $query->createParameter('id')))
+            ->setParameter('id', $addressBookId, IQueryBuilder::PARAM_INT)
+            ->executeStatement();
+
+        $this->sharingBackend->deleteAllShares($addressBookId);
+
+        $query->delete($this->dbCardsPropertiesTable)
+            ->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId, IQueryBuilder::PARAM_INT)))
+            ->executeStatement();
+
+        if ($addressBookData) {
+            $this->dispatcher->dispatchTyped(new AddressBookDeletedEvent($addressBookId, $addressBookData, $shares));
+        }
+    }
+
+    /**
+     * Returns all cards for a specific addressbook id.
+     *
+     * This method should return the following properties for each card:
+     *   * carddata - raw vcard data
+     *   * uri - Some unique url
+     *   * lastmodified - A unix timestamp
+     *
+     * It's recommended to also return the following properties:
+     *   * etag - A unique etag. This must change every time the card changes.
+     *   * size - The size of the card in bytes.
+     *
+     * If these last two properties are provided, less time will be spent
+     * calculating them. If they are specified, you can also omit carddata.
+     * This may speed up certain requests, especially with large cards.
+     *
+     * @param mixed $addressbookId
+     * @return array
+     */
+    public function getCards($addressbookId) {
+        $query = $this->db->getQueryBuilder();
+        $query->select(['id', 'uri', 'lastmodified', 'etag', 'size', 'carddata', 'uid'])
+            ->from($this->dbCardsTable)
+            ->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressbookId)));
+
+        $cards = [];
+
+        $result = $query->execute();
+        while ($row = $result->fetch()) {
+            $row['etag'] = '"' . $row['etag'] . '"';
+
+            $modified = false;
+            $row['carddata'] = $this->readBlob($row['carddata'], $modified);
+            if ($modified) {
+                $row['size'] = strlen($row['carddata']);
+            }
+
+            $cards[] = $row;
+        }
+        $result->closeCursor();
+
+        return $cards;
+    }
+
+    /**
+     * Returns a specific card.
+     *
+     * The same set of properties must be returned as with getCards. The only
+     * exception is that 'carddata' is absolutely required.
+     *
+     * If the card does not exist, you must return false.
+     *
+     * @param mixed $addressBookId
+     * @param string $cardUri
+     * @return array
+     */
+    public function getCard($addressBookId, $cardUri) {
+        $query = $this->db->getQueryBuilder();
+        $query->select(['id', 'uri', 'lastmodified', 'etag', 'size', 'carddata', 'uid'])
+            ->from($this->dbCardsTable)
+            ->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
+            ->andWhere($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
+            ->setMaxResults(1);
+
+        $result = $query->execute();
+        $row = $result->fetch();
+        if (!$row) {
+            return false;
+        }
+        $row['etag'] = '"' . $row['etag'] . '"';
+
+        $modified = false;
+        $row['carddata'] = $this->readBlob($row['carddata'], $modified);
+        if ($modified) {
+            $row['size'] = strlen($row['carddata']);
+        }
+
+        return $row;
+    }
+
+    /**
+     * Returns a list of cards.
+     *
+     * This method should work identical to getCard, but instead return all the
+     * cards in the list as an array.
+     *
+     * If the backend supports this, it may allow for some speed-ups.
+     *
+     * @param mixed $addressBookId
+     * @param array $uris
+     * @return array
+     */
+    public function getMultipleCards($addressBookId, array $uris) {
+        if (empty($uris)) {
+            return [];
+        }
+
+        $chunks = array_chunk($uris, 100);
+        $cards = [];
+
+        $query = $this->db->getQueryBuilder();
+        $query->select(['id', 'uri', 'lastmodified', 'etag', 'size', 'carddata', 'uid'])
+            ->from($this->dbCardsTable)
+            ->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
+            ->andWhere($query->expr()->in('uri', $query->createParameter('uri')));
+
+        foreach ($chunks as $uris) {
+            $query->setParameter('uri', $uris, IQueryBuilder::PARAM_STR_ARRAY);
+            $result = $query->execute();
+
+            while ($row = $result->fetch()) {
+                $row['etag'] = '"' . $row['etag'] . '"';
+
+                $modified = false;
+                $row['carddata'] = $this->readBlob($row['carddata'], $modified);
+                if ($modified) {
+                    $row['size'] = strlen($row['carddata']);
+                }
+
+                $cards[] = $row;
+            }
+            $result->closeCursor();
+        }
+        return $cards;
+    }
+
+    /**
+     * Creates a new card.
+     *
+     * The addressbook id will be passed as the first argument. This is the
+     * same id as it is returned from the getAddressBooksForUser method.
+     *
+     * The cardUri is a base uri, and doesn't include the full path. The
+     * cardData argument is the vcard body, and is passed as a string.
+     *
+     * It is possible to return an ETag from this method. This ETag is for the
+     * newly created resource, and must be enclosed with double quotes (that
+     * is, the string itself must contain the double quotes).
+     *
+     * You should only return the ETag if you store the carddata as-is. If a
+     * subsequent GET request on the same card does not have the same body,
+     * byte-by-byte and you did return an ETag here, clients tend to get
+     * confused.
+     *
+     * If you don't return an ETag, you can just return null.
+     *
+     * @param mixed $addressBookId
+     * @param string $cardUri
+     * @param string $cardData
+     * @param bool $checkAlreadyExists
+     * @return string
+     */
+    public function createCard($addressBookId, $cardUri, $cardData, bool $checkAlreadyExists = true) {
+        $etag = md5($cardData);
+        $uid = $this->getUID($cardData);
+
+        if ($checkAlreadyExists) {
+            $q = $this->db->getQueryBuilder();
+            $q->select('uid')
+                ->from($this->dbCardsTable)
+                ->where($q->expr()->eq('addressbookid', $q->createNamedParameter($addressBookId)))
+                ->andWhere($q->expr()->eq('uid', $q->createNamedParameter($uid)))
+                ->setMaxResults(1);
+            $result = $q->executeQuery();
+            $count = (bool)$result->fetchOne();
+            $result->closeCursor();
+            if ($count) {
+                throw new \Sabre\DAV\Exception\BadRequest('VCard object with uid already exists in this addressbook collection.');
+            }
+        }
+
+        $query = $this->db->getQueryBuilder();
+        $query->insert('cards')
+            ->values([
+                'carddata' => $query->createNamedParameter($cardData, IQueryBuilder::PARAM_LOB),
+                'uri' => $query->createNamedParameter($cardUri),
+                'lastmodified' => $query->createNamedParameter(time()),
+                'addressbookid' => $query->createNamedParameter($addressBookId),
+                'size' => $query->createNamedParameter(strlen($cardData)),
+                'etag' => $query->createNamedParameter($etag),
+                'uid' => $query->createNamedParameter($uid),
+            ])
+            ->execute();
+
+        $etagCacheKey = "$addressBookId#$cardUri";
+        $this->etagCache[$etagCacheKey] = $etag;
+
+        $this->addChange($addressBookId, $cardUri, 1);
+        $this->updateProperties($addressBookId, $cardUri, $cardData);
+
+        $addressBookData = $this->getAddressBookById($addressBookId);
+        $shares = $this->getShares($addressBookId);
+        $objectRow = $this->getCard($addressBookId, $cardUri);
+        $this->dispatcher->dispatchTyped(new CardCreatedEvent($addressBookId, $addressBookData, $shares, $objectRow));
+
+        return '"' . $etag . '"';
+    }
+
+    /**
+     * Updates a card.
+     *
+     * The addressbook id will be passed as the first argument. This is the
+     * same id as it is returned from the getAddressBooksForUser method.
+     *
+     * The cardUri is a base uri, and doesn't include the full path. The
+     * cardData argument is the vcard body, and is passed as a string.
+     *
+     * It is possible to return an ETag from this method. This ETag should
+     * match that of the updated resource, and must be enclosed with double
+     * quotes (that is: the string itself must contain the actual quotes).
+     *
+     * You should only return the ETag if you store the carddata as-is. If a
+     * subsequent GET request on the same card does not have the same body,
+     * byte-by-byte and you did return an ETag here, clients tend to get
+     * confused.
+     *
+     * If you don't return an ETag, you can just return null.
+     *
+     * @param mixed $addressBookId
+     * @param string $cardUri
+     * @param string $cardData
+     * @return string
+     */
+    public function updateCard($addressBookId, $cardUri, $cardData) {
+        $uid = $this->getUID($cardData);
+        $etag = md5($cardData);
+        $query = $this->db->getQueryBuilder();
+
+        // check for recently stored etag and stop if it is the same
+        $etagCacheKey = "$addressBookId#$cardUri";
+        if (isset($this->etagCache[$etagCacheKey]) && $this->etagCache[$etagCacheKey] === $etag) {
+            return '"' . $etag . '"';
+        }
+
+        $query->update($this->dbCardsTable)
+            ->set('carddata', $query->createNamedParameter($cardData, IQueryBuilder::PARAM_LOB))
+            ->set('lastmodified', $query->createNamedParameter(time()))
+            ->set('size', $query->createNamedParameter(strlen($cardData)))
+            ->set('etag', $query->createNamedParameter($etag))
+            ->set('uid', $query->createNamedParameter($uid))
+            ->where($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
+            ->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
+            ->execute();
+
+        $this->etagCache[$etagCacheKey] = $etag;
+
+        $this->addChange($addressBookId, $cardUri, 2);
+        $this->updateProperties($addressBookId, $cardUri, $cardData);
+
+        $addressBookData = $this->getAddressBookById($addressBookId);
+        $shares = $this->getShares($addressBookId);
+        $objectRow = $this->getCard($addressBookId, $cardUri);
+        $this->dispatcher->dispatchTyped(new CardUpdatedEvent($addressBookId, $addressBookData, $shares, $objectRow));
+        return '"' . $etag . '"';
+    }
+
+    /**
+     * Deletes a card
+     *
+     * @param mixed $addressBookId
+     * @param string $cardUri
+     * @return bool
+     */
+    public function deleteCard($addressBookId, $cardUri) {
+        $addressBookData = $this->getAddressBookById($addressBookId);
+        $shares = $this->getShares($addressBookId);
+        $objectRow = $this->getCard($addressBookId, $cardUri);
+
+        try {
+            $cardId = $this->getCardId($addressBookId, $cardUri);
+        } catch (\InvalidArgumentException $e) {
+            $cardId = null;
+        }
+        $query = $this->db->getQueryBuilder();
+        $ret = $query->delete($this->dbCardsTable)
+            ->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)))
+            ->andWhere($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
+            ->executeStatement();
+
+        $this->addChange($addressBookId, $cardUri, 3);
+
+        if ($ret === 1) {
+            if ($cardId !== null) {
+                $this->dispatcher->dispatchTyped(new CardDeletedEvent($addressBookId, $addressBookData, $shares, $objectRow));
+                $this->purgeProperties($addressBookId, $cardId);
+            }
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * The getChanges method returns all the changes that have happened, since
+     * the specified syncToken in the specified address book.
+     *
+     * This function should return an array, such as the following:
+     *
+     * [
+     *   'syncToken' => 'The current synctoken',
+     *   'added'   => [
+     *      'new.txt',
+     *   ],
+     *   'modified'   => [
+     *      'modified.txt',
+     *   ],
+     *   'deleted' => [
+     *      'foo.php.bak',
+     *      'old.txt'
+     *   ]
+     * ];
+     *
+     * The returned syncToken property should reflect the *current* syncToken
+     * of the calendar, as reported in the {http://sabredav.org/ns}sync-token
+     * property. This is needed here too, to ensure the operation is atomic.
+     *
+     * If the $syncToken argument is specified as null, this is an initial
+     * sync, and all members should be reported.
+     *
+     * The modified property is an array of nodenames that have changed since
+     * the last token.
+     *
+     * The deleted property is an array with nodenames, that have been deleted
+     * from collection.
+     *
+     * The $syncLevel argument is basically the 'depth' of the report. If it's
+     * 1, you only have to report changes that happened only directly in
+     * immediate descendants. If it's 2, it should also include changes from
+     * the nodes below the child collections. (grandchildren)
+     *
+     * The $limit argument allows a client to specify how many results should
+     * be returned at most. If the limit is not specified, it should be treated
+     * as infinite.
+     *
+     * If the limit (infinite or not) is higher than you're willing to return,
+     * you should throw a Sabre\DAV\Exception\TooMuchMatches() exception.
+     *
+     * If the syncToken is expired (due to data cleanup) or unknown, you must
+     * return null.
+     *
+     * The limit is 'suggestive'. You are free to ignore it.
+     *
+     * @param string $addressBookId
+     * @param string $syncToken
+     * @param int $syncLevel
+     * @param int|null $limit
+     * @return array
+     */
+    public function getChangesForAddressBook($addressBookId, $syncToken, $syncLevel, $limit = null) {
+        // Current synctoken
+        $qb = $this->db->getQueryBuilder();
+        $qb->select('synctoken')
+            ->from('addressbooks')
+            ->where(
+                $qb->expr()->eq('id', $qb->createNamedParameter($addressBookId))
+            );
+        $stmt = $qb->executeQuery();
+        $currentToken = $stmt->fetchOne();
+        $stmt->closeCursor();
+
+        if (is_null($currentToken)) {
+            return [];
+        }
+
+        $result = [
+            'syncToken' => $currentToken,
+            'added' => [],
+            'modified' => [],
+            'deleted' => [],
+        ];
+
+        if ($syncToken) {
+            $qb = $this->db->getQueryBuilder();
+            $qb->select('uri', 'operation')
+                ->from('addressbookchanges')
+                ->where(
+                    $qb->expr()->andX(
+                        $qb->expr()->gte('synctoken', $qb->createNamedParameter($syncToken)),
+                        $qb->expr()->lt('synctoken', $qb->createNamedParameter($currentToken)),
+                        $qb->expr()->eq('addressbookid', $qb->createNamedParameter($addressBookId))
+                    )
+                )->orderBy('synctoken');
+
+            if (is_int($limit) && $limit > 0) {
+                $qb->setMaxResults($limit);
+            }
+
+            // Fetching all changes
+            $stmt = $qb->executeQuery();
+
+            $changes = [];
+
+            // This loop ensures that any duplicates are overwritten, only the
+            // last change on a node is relevant.
+            while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
+                $changes[$row['uri']] = $row['operation'];
+            }
+            $stmt->closeCursor();
+
+            foreach ($changes as $uri => $operation) {
+                switch ($operation) {
+                    case 1:
+                        $result['added'][] = $uri;
+                        break;
+                    case 2:
+                        $result['modified'][] = $uri;
+                        break;
+                    case 3:
+                        $result['deleted'][] = $uri;
+                        break;
+                }
+            }
+        } else {
+            $qb = $this->db->getQueryBuilder();
+            $qb->select('uri')
+                ->from('cards')
+                ->where(
+                    $qb->expr()->eq('addressbookid', $qb->createNamedParameter($addressBookId))
+                );
+            // No synctoken supplied, this is the initial sync.
+            $stmt = $qb->executeQuery();
+            $result['added'] = $stmt->fetchAll(\PDO::FETCH_COLUMN);
+            $stmt->closeCursor();
+        }
+        return $result;
+    }
+
+    /**
+     * Adds a change record to the addressbookchanges table.
+     *
+     * @param mixed $addressBookId
+     * @param string $objectUri
+     * @param int $operation 1 = add, 2 = modify, 3 = delete
+     * @return void
+     */
+    protected function addChange($addressBookId, $objectUri, $operation) {
+        $sql = 'INSERT INTO `*PREFIX*addressbookchanges`(`uri`, `synctoken`, `addressbookid`, `operation`) SELECT ?, `synctoken`, ?, ? FROM `*PREFIX*addressbooks` WHERE `id` = ?';
+        $stmt = $this->db->prepare($sql);
+        $stmt->execute([
+            $objectUri,
+            $addressBookId,
+            $operation,
+            $addressBookId
+        ]);
+        $stmt = $this->db->prepare('UPDATE `*PREFIX*addressbooks` SET `synctoken` = `synctoken` + 1 WHERE `id` = ?');
+        $stmt->execute([
+            $addressBookId
+        ]);
+    }
+
+    /**
+     * @param resource|string $cardData
+     * @param bool $modified
+     * @return string
+     */
+    private function readBlob($cardData, &$modified = false) {
+        if (is_resource($cardData)) {
+            $cardData = stream_get_contents($cardData);
+        }
+
+        // Micro optimisation
+        // don't loop through
+        if (strpos($cardData, 'PHOTO:data:') === 0) {
+            return $cardData;
+        }
+
+        $cardDataArray = explode("\r\n", $cardData);
+
+        $cardDataFiltered = [];
+        $removingPhoto = false;
+        foreach ($cardDataArray as $line) {
+            if (strpos($line, 'PHOTO:data:') === 0
+                && strpos($line, 'PHOTO:data:image/') !== 0) {
+                // Filter out PHOTO data of non-images
+                $removingPhoto = true;
+                $modified = true;
+                continue;
+            }
+
+            if ($removingPhoto) {
+                if (strpos($line, ' ') === 0) {
+                    continue;
+                }
+                // No leading space means this is a new property
+                $removingPhoto = false;
+            }
+
+            $cardDataFiltered[] = $line;
+        }
+        return implode("\r\n", $cardDataFiltered);
+    }
+
+    /**
+     * @param list<array{href: string, commonName: string, readOnly: bool}> $add
+     * @param list<string> $remove
+     */
+    public function updateShares(IShareable $shareable, array $add, array $remove): void {
+        $addressBookId = $shareable->getResourceId();
+        $addressBookData = $this->getAddressBookById($addressBookId);
+        $oldShares = $this->getShares($addressBookId);
+
+        $this->sharingBackend->updateShares($shareable, $add, $remove);
+
+        $this->dispatcher->dispatchTyped(new AddressBookShareUpdatedEvent($addressBookId, $addressBookData, $oldShares, $add, $remove));
+    }
+
+    /**
+     * Search contacts in a specific address-book
+     *
+     * @param int $addressBookId
+     * @param string $pattern which should match within the $searchProperties
+     * @param array $searchProperties defines the properties within the query pattern should match
+     * @param array $options = array() to define the search behavior
+     *    - 'escape_like_param' - If set to false wildcards _ and % are not escaped, otherwise they are
+     *    - 'limit' - Set a numeric limit for the search results
+     *    - 'offset' - Set the offset for the limited search results
+     *    - 'wildcard' - Whether the search should use wildcards
+     * @psalm-param array{escape_like_param?: bool, limit?: int, offset?: int, wildcard?: bool} $options
+     * @return array an array of contacts which are arrays of key-value-pairs
+     */
+    public function search($addressBookId, $pattern, $searchProperties, $options = []): array {
+        return $this->searchByAddressBookIds([$addressBookId], $pattern, $searchProperties, $options);
+    }
+
+    /**
+     * Search contacts in all address-books accessible by a user
+     *
+     * @param string $principalUri
+     * @param string $pattern
+     * @param array $searchProperties
+     * @param array $options
+     * @return array
+     */
+    public function searchPrincipalUri(string $principalUri,
+                                        string $pattern,
+                                        array $searchProperties,
+                                        array $options = []): array {
+        $addressBookIds = array_map(static function ($row):int {
+            return (int) $row['id'];
+        }, $this->getAddressBooksForUser($principalUri));
+
+        return $this->searchByAddressBookIds($addressBookIds, $pattern, $searchProperties, $options);
+    }
+
+    /**
+     * @param array $addressBookIds
+     * @param string $pattern
+     * @param array $searchProperties
+     * @param array $options
+     * @psalm-param array{types?: bool, escape_like_param?: bool, limit?: int, offset?: int, wildcard?: bool} $options
+     * @return array
+     */
+    private function searchByAddressBookIds(array $addressBookIds,
+                                            string $pattern,
+                                            array $searchProperties,
+                                            array $options = []): array {
+        $escapePattern = !\array_key_exists('escape_like_param', $options) || $options['escape_like_param'] !== false;
+        $useWildcards = !\array_key_exists('wildcard', $options) || $options['wildcard'] !== false;
+
+        $query2 = $this->db->getQueryBuilder();
+
+        $addressBookOr = $query2->expr()->orX();
+        foreach ($addressBookIds as $addressBookId) {
+            $addressBookOr->add($query2->expr()->eq('cp.addressbookid', $query2->createNamedParameter($addressBookId)));
+        }
+
+        if ($addressBookOr->count() === 0) {
+            return [];
+        }
+
+        $propertyOr = $query2->expr()->orX();
+        foreach ($searchProperties as $property) {
+            if ($escapePattern) {
+                if ($property === 'EMAIL' && strpos($pattern, ' ') !== false) {
+                    // There can be no spaces in emails
+                    continue;
+                }
+
+                if ($property === 'CLOUD' && preg_match('/[^a-zA-Z0-9 :_.@\/\-\']/', $pattern) === 1) {
+                    // There can be no chars in cloud ids which are not valid for user ids plus :/
+                    // worst case: CA61590A-BBBC-423E-84AF-E6DF01455A53@https://my.nxt/srv/
+                    continue;
+                }
+            }
+
+            $propertyOr->add($query2->expr()->eq('cp.name', $query2->createNamedParameter($property)));
+        }
+
+        if ($propertyOr->count() === 0) {
+            return [];
+        }
+
+        $query2->selectDistinct('cp.cardid')
+            ->from($this->dbCardsPropertiesTable, 'cp')
+            ->andWhere($addressBookOr)
+            ->andWhere($propertyOr);
+
+        // No need for like when the pattern is empty
+        if ('' !== $pattern) {
+            if (!$useWildcards) {
+                $query2->andWhere($query2->expr()->eq('cp.value', $query2->createNamedParameter($pattern)));
+            } elseif (!$escapePattern) {
+                $query2->andWhere($query2->expr()->ilike('cp.value', $query2->createNamedParameter($pattern)));
+            } else {
+                $query2->andWhere($query2->expr()->ilike('cp.value', $query2->createNamedParameter('%' . $this->db->escapeLikeParameter($pattern) . '%')));
+            }
+        }
+
+        if (isset($options['limit'])) {
+            $query2->setMaxResults($options['limit']);
+        }
+        if (isset($options['offset'])) {
+            $query2->setFirstResult($options['offset']);
+        }
+
+        $result = $query2->execute();
+        $matches = $result->fetchAll();
+        $result->closeCursor();
+        $matches = array_map(function ($match) {
+            return (int)$match['cardid'];
+        }, $matches);
+
+        $cards = [];
+        $query = $this->db->getQueryBuilder();
+        $query->select('c.addressbookid', 'c.carddata', 'c.uri')
+            ->from($this->dbCardsTable, 'c')
+            ->where($query->expr()->in('c.id', $query->createParameter('matches')));
+
+        foreach (array_chunk($matches, 1000) as $matchesChunk) {
+            $query->setParameter('matches', $matchesChunk, IQueryBuilder::PARAM_INT_ARRAY);
+            $result = $query->executeQuery();
+            $cards = array_merge($cards, $result->fetchAll());
+            $result->closeCursor();
+        }
+
+        return array_map(function ($array) {
+            $array['addressbookid'] = (int) $array['addressbookid'];
+            $modified = false;
+            $array['carddata'] = $this->readBlob($array['carddata'], $modified);
+            if ($modified) {
+                $array['size'] = strlen($array['carddata']);
+            }
+            return $array;
+        }, $cards);
+    }
+
+    /**
+     * @param int $bookId
+     * @param string $name
+     * @return array
+     */
+    public function collectCardProperties($bookId, $name) {
+        $query = $this->db->getQueryBuilder();
+        $result = $query->selectDistinct('value')
+            ->from($this->dbCardsPropertiesTable)
+            ->where($query->expr()->eq('name', $query->createNamedParameter($name)))
+            ->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($bookId)))
+            ->execute();
+
+        $all = $result->fetchAll(PDO::FETCH_COLUMN);
+        $result->closeCursor();
+
+        return $all;
+    }
+
+    /**
+     * get URI from a given contact
+     *
+     * @param int $id
+     * @return string
+     */
+    public function getCardUri($id) {
+        $query = $this->db->getQueryBuilder();
+        $query->select('uri')->from($this->dbCardsTable)
+            ->where($query->expr()->eq('id', $query->createParameter('id')))
+            ->setParameter('id', $id);
+
+        $result = $query->execute();
+        $uri = $result->fetch();
+        $result->closeCursor();
+
+        if (!isset($uri['uri'])) {
+            throw new \InvalidArgumentException('Card does not exists: ' . $id);
+        }
+
+        return $uri['uri'];
+    }
+
+    /**
+     * return contact with the given URI
+     *
+     * @param int $addressBookId
+     * @param string $uri
+     * @returns array
+     */
+    public function getContact($addressBookId, $uri) {
+        $result = [];
+        $query = $this->db->getQueryBuilder();
+        $query->select('*')->from($this->dbCardsTable)
+            ->where($query->expr()->eq('uri', $query->createNamedParameter($uri)))
+            ->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
+        $queryResult = $query->execute();
+        $contact = $queryResult->fetch();
+        $queryResult->closeCursor();
+
+        if (is_array($contact)) {
+            $modified = false;
+            $contact['etag'] = '"' . $contact['etag'] . '"';
+            $contact['carddata'] = $this->readBlob($contact['carddata'], $modified);
+            if ($modified) {
+                $contact['size'] = strlen($contact['carddata']);
+            }
+
+            $result = $contact;
+        }
+
+        return $result;
+    }
+
+    /**
+     * Returns the list of people whom this address book is shared with.
+     *
+     * Every element in this array should have the following properties:
+     *   * href - Often a mailto: address
+     *   * commonName - Optional, for example a first + last name
+     *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+     *   * readOnly - boolean
+     *
+     * @return list<array{href: string, commonName: string, status: int, readOnly: bool, '{http://owncloud.org/ns}principal': string, '{http://owncloud.org/ns}group-share': bool}>
+     */
+    public function getShares(int $addressBookId): array {
+        return $this->sharingBackend->getShares($addressBookId);
+    }
+
+    /**
+     * update properties table
+     *
+     * @param int $addressBookId
+     * @param string $cardUri
+     * @param string $vCardSerialized
+     */
+    protected function updateProperties($addressBookId, $cardUri, $vCardSerialized) {
+        $cardId = $this->getCardId($addressBookId, $cardUri);
+        $vCard = $this->readCard($vCardSerialized);
+
+        $this->purgeProperties($addressBookId, $cardId);
+
+        $query = $this->db->getQueryBuilder();
+        $query->insert($this->dbCardsPropertiesTable)
+            ->values(
+                [
+                    'addressbookid' => $query->createNamedParameter($addressBookId),
+                    'cardid' => $query->createNamedParameter($cardId),
+                    'name' => $query->createParameter('name'),
+                    'value' => $query->createParameter('value'),
+                    'preferred' => $query->createParameter('preferred')
+                ]
+            );
+
+
+        $this->db->beginTransaction();
+
+        try {
+            foreach ($vCard->children() as $property) {
+                if (!in_array($property->name, self::$indexProperties)) {
+                    continue;
+                }
+                $preferred = 0;
+                foreach ($property->parameters as $parameter) {
+                    if ($parameter->name === 'TYPE' && strtoupper($parameter->getValue()) === 'PREF') {
+                        $preferred = 1;
+                        break;
+                    }
+                }
+                $query->setParameter('name', $property->name);
+                $query->setParameter('value', mb_strcut($property->getValue(), 0, 254));
+                $query->setParameter('preferred', $preferred);
+                $query->execute();
+            }
+            $this->db->commit();
+        } catch (\Exception $e) {
+            $this->db->rollBack();
+        }
+    }
+
+    /**
+     * read vCard data into a vCard object
+     *
+     * @param string $cardData
+     * @return VCard
+     */
+    protected function readCard($cardData) {
+        return Reader::read($cardData);
+    }
+
+    /**
+     * delete all properties from a given card
+     *
+     * @param int $addressBookId
+     * @param int $cardId
+     */
+    protected function purgeProperties($addressBookId, $cardId) {
+        $query = $this->db->getQueryBuilder();
+        $query->delete($this->dbCardsPropertiesTable)
+            ->where($query->expr()->eq('cardid', $query->createNamedParameter($cardId)))
+            ->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
+        $query->execute();
+    }
+
+    /**
+     * Get ID from a given contact
+     */
+    protected function getCardId(int $addressBookId, string $uri): int {
+        $query = $this->db->getQueryBuilder();
+        $query->select('id')->from($this->dbCardsTable)
+            ->where($query->expr()->eq('uri', $query->createNamedParameter($uri)))
+            ->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
+
+        $result = $query->execute();
+        $cardIds = $result->fetch();
+        $result->closeCursor();
+
+        if (!isset($cardIds['id'])) {
+            throw new \InvalidArgumentException('Card does not exists: ' . $uri);
+        }
+
+        return (int)$cardIds['id'];
+    }
+
+    /**
+     * For shared address books the sharee is set in the ACL of the address book
+     *
+     * @param int $addressBookId
+     * @param list<array{privilege: string, principal: string, protected: bool}> $acl
+     * @return list<array{privilege: string, principal: string, protected: bool}>
+     */
+    public function applyShareAcl(int $addressBookId, array $acl): array {
+        return $this->sharingBackend->applyShareAcl($addressBookId, $acl);
+    }
+
+    private function convertPrincipal(string $principalUri, bool $toV2): string {
+        if ($this->principalBackend->getPrincipalPrefix() === 'principals') {
+            [, $name] = \Sabre\Uri\split($principalUri);
+            if ($toV2 === true) {
+                return "principals/users/$name";
+            }
+            return "principals/$name";
+        }
+        return $principalUri;
+    }
+
+    private function addOwnerPrincipal(array &$addressbookInfo): void {
+        $ownerPrincipalKey = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}owner-principal';
+        $displaynameKey = '{' . \OCA\DAV\DAV\Sharing\Plugin::NS_NEXTCLOUD . '}owner-displayname';
+        if (isset($addressbookInfo[$ownerPrincipalKey])) {
+            $uri = $addressbookInfo[$ownerPrincipalKey];
+        } else {
+            $uri = $addressbookInfo['principaluri'];
+        }
+
+        $principalInformation = $this->principalBackend->getPrincipalByPath($uri);
+        if (isset($principalInformation['{DAV:}displayname'])) {
+            $addressbookInfo[$displaynameKey] = $principalInformation['{DAV:}displayname'];
+        }
+    }
+
+    /**
+     * Extract UID from vcard
+     *
+     * @param string $cardData the vcard raw data
+     * @return string the uid
+     * @throws BadRequest if no UID is available or vcard is empty
+     */
+    private function getUID(string $cardData): string {
+        if ($cardData !== '') {
+            $vCard = Reader::read($cardData);
+            if ($vCard->UID) {
+                $uid = $vCard->UID->getValue();
+                return $uid;
+            }
+            // should already be handled, but just in case
+            throw new BadRequest('vCards on CardDAV servers MUST have a UID property');
+        }
+        // should already be handled, but just in case
+        throw new BadRequest('vCard can not be empty');
+    }
 }