1 files changed, 110 insertions, 51 deletions

diff --git a/apps/files_external/lib/Service/BackendService.php b/apps/files_external/lib/Service/BackendService.php
index 49af01f5bf9..3a688ee66e6 100644
--- a/apps/files_external/lib/Service/BackendService.php
+++ b/apps/files_external/lib/Service/BackendService.php
@@ -1,34 +1,23 @@
 <?php
+
 /**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Morris Jobke <hey@morrisjobke.de>
- * @author Robin McCorkell <robin@mccorkell.me.uk>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
- *
+ * SPDX-FileCopyrightText: 2018-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
  */
-
 namespace OCA\Files_External\Service;
 
-use \OCP\IConfig;
-
-use \OCA\Files_External\Lib\Backend\Backend;
-use \OCA\Files_External\Lib\Auth\AuthMechanism;
-use \OCA\Files_External\Lib\Config\IBackendProvider;
-use \OCA\Files_External\Lib\Config\IAuthMechanismProvider;
+use OCA\Files_External\Config\IConfigHandler;
+use OCA\Files_External\ConfigLexicon;
+use OCA\Files_External\Lib\Auth\AuthMechanism;
+use OCA\Files_External\Lib\Backend\Backend;
+use OCA\Files_External\Lib\Config\IAuthMechanismProvider;
+use OCA\Files_External\Lib\Config\IBackendProvider;
+use OCA\Files_External\Lib\MissingDependency;
+use OCP\EventDispatcher\GenericEvent;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\IAppConfig;
+use OCP\Server;
 
 /**
  * Service class to manage backend definitions
@@ -36,18 +25,15 @@ use \OCA\Files_External\Lib\Config\IAuthMechanismProvider;
 class BackendService {
 
 	/** Visibility constants for VisibilityTrait */
-	const VISIBILITY_NONE = 0;
-	const VISIBILITY_PERSONAL = 1;
-	const VISIBILITY_ADMIN = 2;
+	public const VISIBILITY_NONE = 0;
+	public const VISIBILITY_PERSONAL = 1;
+	public const VISIBILITY_ADMIN = 2;
 	//const VISIBILITY_ALIENS = 4;
 
-	const VISIBILITY_DEFAULT = 3; // PERSONAL | ADMIN
+	public const VISIBILITY_DEFAULT = 3; // PERSONAL | ADMIN
 
 	/** Priority constants for PriorityTrait */
-	const PRIORITY_DEFAULT = 100;
-
-	/** @var IConfig */
-	protected $config;
+	public const PRIORITY_DEFAULT = 100;
 
 	/** @var bool */
 	private $userMountingAllowed = true;
@@ -67,21 +53,17 @@ class BackendService {
 	/** @var IAuthMechanismProvider[] */
 	private $authMechanismProviders = [];
 
-	/**
-	 * @param IConfig $config
-	 */
+	/** @var callable[] */
+	private $configHandlerLoaders = [];
+
+	private $configHandlers = [];
+
 	public function __construct(
-		IConfig $config
+		protected IAppConfig $appConfig,
 	) {
-		$this->config = $config;
-
 		// Load config values
-		if ($this->config->getAppValue('files_external', 'allow_user_mounting', 'yes') !== 'yes') {
-			$this->userMountingAllowed = false;
-		}
-		$this->userMountingBackends = explode(',',
-			$this->config->getAppValue('files_external', 'user_mounting_backends', '')
-		);
+		$this->userMountingAllowed = $appConfig->getValueBool('files_external', ConfigLexicon::ALLOW_USER_MOUNTING);
+		$this->userMountingBackends = explode(',', $appConfig->getValueString('files_external', ConfigLexicon::USER_MOUNTING_BACKENDS));
 
 		// if no backend is in the list an empty string is in the array and user mounting is disabled
 		if ($this->userMountingBackends === ['']) {
@@ -99,7 +81,19 @@ class BackendService {
 		$this->backendProviders[] = $provider;
 	}
 
+	private function callForRegistrations() {
+		static $eventSent = false;
+		if (!$eventSent) {
+			Server::get(IEventDispatcher::class)->dispatch(
+				'OCA\\Files_External::loadAdditionalBackends',
+				new GenericEvent()
+			);
+			$eventSent = true;
+		}
+	}
+
 	private function loadBackendProviders() {
+		$this->callForRegistrations();
 		foreach ($this->backendProviders as $provider) {
 			$this->registerBackends($provider->getBackends());
 		}
@@ -117,6 +111,7 @@ class BackendService {
 	}
 
 	private function loadAuthMechanismProviders() {
+		$this->callForRegistrations();
 		foreach ($this->authMechanismProviders as $provider) {
 			$this->registerAuthMechanisms($provider->getAuthMechanisms());
 		}
@@ -193,8 +188,9 @@ class BackendService {
 	 * @return Backend[]
 	 */
 	public function getAvailableBackends() {
-		return array_filter($this->getBackends(), function($backend) {
-			return !($backend->checkDependencies());
+		return array_filter($this->getBackends(), function ($backend) {
+			$missing = array_filter($backend->checkDependencies(), fn (MissingDependency $dependency) => !$dependency->isOptional());
+			return count($missing) === 0;
 		});
 	}
 
@@ -232,7 +228,7 @@ class BackendService {
 	 * @return AuthMechanism[]
 	 */
 	public function getAuthMechanismsByScheme(array $schemes) {
-		return array_filter($this->getAuthMechanisms(), function($authMech) use ($schemes) {
+		return array_filter($this->getAuthMechanisms(), function ($authMech) use ($schemes) {
 			return in_array($authMech->getScheme(), $schemes, true);
 		});
 	}
@@ -263,8 +259,8 @@ class BackendService {
 	 * @return bool
 	 */
 	protected function isAllowedUserBackend(Backend $backend) {
-		if ($this->userMountingAllowed &&
-			array_intersect($backend->getIdentifierAliases(), $this->userMountingBackends)
+		if ($this->userMountingAllowed
+			&& array_intersect($backend->getIdentifierAliases(), $this->userMountingBackends)
 		) {
 			return true;
 		}
@@ -280,4 +276,67 @@ class BackendService {
 	protected function isAllowedAuthMechanism(AuthMechanism $authMechanism) {
 		return true; // not implemented
 	}
+
+	/**
+	 * registers a configuration handler
+	 *
+	 * The function of the provided $placeholder is mostly to act a sorting
+	 * criteria, so longer placeholders are replaced first. This avoids
+	 * "$user" overwriting parts of "$userMail" and "$userLang", for example.
+	 * The provided value should not contain the $ prefix, only a-z0-9 are
+	 * allowed. Upper case letters are lower cased, the replacement is case-
+	 * insensitive.
+	 *
+	 * The configHandlerLoader should just instantiate the handler on demand.
+	 * For now all handlers are instantiated when a mount is loaded, independent
+	 * of whether the placeholder is present or not. This may change in future.
+	 *
+	 * @since 16.0.0
+	 */
+	public function registerConfigHandler(string $placeholder, callable $configHandlerLoader) {
+		$placeholder = trim(strtolower($placeholder));
+		if (!(bool)\preg_match('/^[a-z0-9]*$/', $placeholder)) {
+			throw new \RuntimeException(sprintf(
+				'Invalid placeholder %s, only [a-z0-9] are allowed', $placeholder
+			));
+		}
+		if ($placeholder === '') {
+			throw new \RuntimeException('Invalid empty placeholder');
+		}
+		if (isset($this->configHandlerLoaders[$placeholder]) || isset($this->configHandlers[$placeholder])) {
+			throw new \RuntimeException(sprintf('A handler is already registered for %s', $placeholder));
+		}
+		$this->configHandlerLoaders[$placeholder] = $configHandlerLoader;
+	}
+
+	protected function loadConfigHandlers():void {
+		$this->callForRegistrations();
+		$newLoaded = false;
+		foreach ($this->configHandlerLoaders as $placeholder => $loader) {
+			$handler = $loader();
+			if (!$handler instanceof IConfigHandler) {
+				throw new \RuntimeException(sprintf(
+					'Handler for %s is not an instance of IConfigHandler', $placeholder
+				));
+			}
+			$this->configHandlers[$placeholder] = $handler;
+			$newLoaded = true;
+		}
+		$this->configHandlerLoaders = [];
+		if ($newLoaded) {
+			// ensure those with longest placeholders come first,
+			// to avoid substring matches
+			uksort($this->configHandlers, function ($phA, $phB) {
+				return strlen($phB) <=> strlen($phA);
+			});
+		}
+	}
+
+	/**
+	 * @since 16.0.0
+	 */
+	public function getConfigHandlers() {
+		$this->loadConfigHandlers();
+		return $this->configHandlers;
+	}
 }