1 files changed, 113 insertions, 0 deletions
diff --git a/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php b/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php
new file mode 100644
index 00000000000..6ac36fea448
--- /dev/null
+++ b/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php
@@ -0,0 +1,113 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\DAV\CardDAV\Integration;
+
+use Sabre\CardDAV\IAddressBook;
+use Sabre\DAV;
+
+/**
+ * @since 19.0.0
+ */
+abstract class ExternalAddressBook implements IAddressBook, DAV\IProperties {
+
+	/** @var string */
+	private const PREFIX = 'app-generated';
+
+	/**
+	 * @var string
+	 *
+	 * Double dash is a valid delimiter,
+	 * because it will always split the URIs correctly:
+	 * - our prefix contains only one dash and won't be split
+	 * - appIds are not allowed to contain dashes as per spec:
+	 * > must contain only lowercase ASCII characters and underscore
+	 * - explode has a limit of three, so even if the app-generated
+	 *   URI has double dashes, it won't be split
+	 */
+	private const DELIMITER = '--';
+
+	/** @var string */
+	private $appId;
+
+	/** @var string */
+	private $uri;
+
+	/**
+	 * @param string $appId
+	 * @param string $uri
+	 */
+	public function __construct(string $appId, string $uri) {
+		$this->appId = $appId;
+		$this->uri = $uri;
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	final public function getName() {
+		return implode(self::DELIMITER, [
+			self::PREFIX,
+			$this->appId,
+			$this->uri,
+		]);
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	final public function setName($name) {
+		throw new DAV\Exception\MethodNotAllowed('Renaming address books is not yet supported');
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	final public function createDirectory($name) {
+		throw new DAV\Exception\MethodNotAllowed('Creating collections in address book objects is not allowed');
+
+	}
+
+	/**
+	 * Checks whether the address book uri is app-generated
+	 *
+	 * @param string $uri
+	 *
+	 * @return bool
+	 */
+	public static function isAppGeneratedAddressBook(string $uri): bool {
+		return strpos($uri, self::PREFIX) === 0 && substr_count($uri, self::DELIMITER) >= 2;
+	}
+
+	/**
+	 * Splits an app-generated uri into appId and uri
+	 *
+	 * @param string $uri
+	 *
+	 * @return array
+	 */
+	public static function splitAppGeneratedAddressBookUri(string $uri): array {
+		$array = array_slice(explode(self::DELIMITER, $uri, 3), 1);
+		// Check the array has expected amount of elements
+		// and none of them is an empty string
+		if (\count($array) !== 2 || \in_array('', $array, true)) {
+			throw new \InvalidArgumentException('Provided address book uri was not app-generated');
+		}
+
+		return $array;
+	}
+
+	/**
+	 * Checks whether a address book name the user wants to create violates
+	 * the reserved name for URIs
+	 *
+	 * @param string $uri
+	 *
+	 * @return bool
+	 */
+	public static function doesViolateReservedName(string $uri): bool {
+		return strpos($uri, self::PREFIX) === 0;
+	}
+
+}