owncloud / core

	 * @param int $limit

	 * @return array

	 */

	function getChangesForAddressBook($addressBookId, $syncToken, $syncLevel, $limit = null) {

		// Current synctoken

		$stmt = $this->db->prepare('SELECT `synctoken` FROM `*PREFIX*addressbooks` WHERE `id` = ?');

		$stmt->execute([ $addressBookId ]);

		$currentToken = $stmt->fetchColumn(0);

		if (is_null($currentToken)) return null;

		$result = [

			'syncToken' => $currentToken,

			'added'     => [],

			'modified'  => [],

			'deleted'   => [],

		];

		if ($syncToken) {

			$query = "SELECT `uri`, `operation` FROM `*PREFIX*addressbookchanges` WHERE `synctoken` >= ? AND `synctoken` < ? AND `addressbookid` = ? ORDER BY `synctoken`";

			if ($limit>0) {

				$query .= " `LIMIT` " . (int)$limit;

			}

			// Fetching all changes

			$stmt = $this->db->prepare($query);

			$stmt->execute([$syncToken, $currentToken, $addressBookId]);

			$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'];

			}

			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 {

			// No synctoken supplied, this is the initial sync.

			$query = "SELECT `uri` FROM `*PREFIX*cards` WHERE `addressbookid` = ?";

			$stmt = $this->db->prepare($query);

			$stmt->execute([$addressBookId]);

			$result['added'] = $stmt->fetchAll(\PDO::FETCH_COLUMN);

		}

		return $result;

	}

	/**

	 * Adds a change record to the addressbookchanges table.

	 * @param int $limit

	 * @return array

	 */

	function getChangesForCalendar($calendarId, $syncToken, $syncLevel, $limit = null) {

		// Current synctoken

		$stmt = $this->db->prepare('SELECT `synctoken` FROM `*PREFIX*calendars` WHERE `id` = ?');

		$stmt->execute([ $calendarId ]);

		$currentToken = $stmt->fetchColumn(0);

		if (is_null($currentToken)) {

			return null;

		}

		$result = [

			'syncToken' => $currentToken,

			'added'     => [],

			'modified'  => [],

			'deleted'   => [],

		];

		if ($syncToken) {

			$query = "SELECT `uri`, `operation` FROM `*PREFIX*calendarchanges` WHERE `synctoken` >= ? AND `synctoken` < ? AND `calendarid` = ? ORDER BY `synctoken`";

			if ($limit>0) {

				$query.= " `LIMIT` " . (int)$limit;

			}

			// Fetching all changes

			$stmt = $this->db->prepare($query);

			$stmt->execute([$syncToken, $currentToken, $calendarId]);

			$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'];

			}

			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 {

			// No synctoken supplied, this is the initial sync.

			$query = "SELECT `uri` FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ?";

			$stmt = $this->db->prepare($query);

			$stmt->execute([$calendarId]);

			$result['added'] = $stmt->fetchAll(\PDO::FETCH_COLUMN);

		}

		return $result;

	}

	/**

	 * Returns a list of subscriptions for a principal.