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diff --git a/apps/files_external/lib/Service/BackendService.php b/apps/files_external/lib/Service/BackendService.php
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+++ b/apps/files_external/lib/Service/BackendService.php
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+<?php
+/**
+ * @author Morris Jobke <hey@morrisjobke.de>
+ * @author Robin McCorkell <robin@mccorkell.me.uk>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @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/>
+ *
+ */
+
+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;
+
+/**
+ * Service class to manage backend definitions
+ */
+class BackendService {
+
+	/** Visibility constants for VisibilityTrait */
+	const VISIBILITY_NONE = 0;
+	const VISIBILITY_PERSONAL = 1;
+	const VISIBILITY_ADMIN = 2;
+	//const VISIBILITY_ALIENS = 4;
+
+	const VISIBILITY_DEFAULT = 3; // PERSONAL | ADMIN
+
+	/** Priority constants for PriorityTrait */
+	const PRIORITY_DEFAULT = 100;
+
+	/** @var IConfig */
+	protected $config;
+
+	/** @var bool */
+	private $userMountingAllowed = true;
+
+	/** @var string[] */
+	private $userMountingBackends = [];
+
+	/** @var Backend[] */
+	private $backends = [];
+
+	/** @var IBackendProvider[] */
+	private $backendProviders = [];
+
+	/** @var AuthMechanism[] */
+	private $authMechanisms = [];
+
+	/** @var IAuthMechanismProvider[] */
+	private $authMechanismProviders = [];
+
+	/**
+	 * @param IConfig $config
+	 */
+	public function __construct(
+		IConfig $config
+	) {
+		$this->config = $config;
+
+		// Load config values
+		if ($this->config->getAppValue('files_external', 'allow_user_mounting', 'yes') !== 'yes') {
+			$this->userMountingAllowed = false;
+		}
+		$this->userMountingBackends = explode(',',
+			$this->config->getAppValue('files_external', 'user_mounting_backends', '')
+		);
+
+		// if no backend is in the list an empty string is in the array and user mounting is disabled
+		if ($this->userMountingBackends === ['']) {
+			$this->userMountingAllowed = false;
+		}
+	}
+
+	/**
+	 * Register a backend provider
+	 *
+	 * @since 9.1.0
+	 * @param IBackendProvider $provider
+	 */
+	public function registerBackendProvider(IBackendProvider $provider) {
+		$this->backendProviders[] = $provider;
+	}
+
+	private function loadBackendProviders() {
+		foreach ($this->backendProviders as $provider) {
+			$this->registerBackends($provider->getBackends());
+		}
+		$this->backendProviders = [];
+	}
+
+	/**
+	 * Register an auth mechanism provider
+	 *
+	 * @since 9.1.0
+	 * @param IAuthMechanismProvider $provider
+	 */
+	public function registerAuthMechanismProvider(IAuthMechanismProvider $provider) {
+		$this->authMechanismProviders[] = $provider;
+	}
+
+	private function loadAuthMechanismProviders() {
+		foreach ($this->authMechanismProviders as $provider) {
+			$this->registerAuthMechanisms($provider->getAuthMechanisms());
+		}
+		$this->authMechanismProviders = [];
+	}
+
+	/**
+	 * Register a backend
+	 *
+	 * @deprecated 9.1.0 use registerBackendProvider()
+	 * @param Backend $backend
+	 */
+	public function registerBackend(Backend $backend) {
+		if (!$this->isAllowedUserBackend($backend)) {
+			$backend->removeVisibility(BackendService::VISIBILITY_PERSONAL);
+		}
+		foreach ($backend->getIdentifierAliases() as $alias) {
+			$this->backends[$alias] = $backend;
+		}
+	}
+
+	/**
+	 * @deprecated 9.1.0 use registerBackendProvider()
+	 * @param Backend[] $backends
+	 */
+	public function registerBackends(array $backends) {
+		foreach ($backends as $backend) {
+			$this->registerBackend($backend);
+		}
+	}
+	/**
+	 * Register an authentication mechanism
+	 *
+	 * @deprecated 9.1.0 use registerAuthMechanismProvider()
+	 * @param AuthMechanism $authMech
+	 */
+	public function registerAuthMechanism(AuthMechanism $authMech) {
+		if (!$this->isAllowedAuthMechanism($authMech)) {
+			$authMech->removeVisibility(BackendService::VISIBILITY_PERSONAL);
+		}
+		foreach ($authMech->getIdentifierAliases() as $alias) {
+			$this->authMechanisms[$alias] = $authMech;
+		}
+	}
+
+	/**
+	 * @deprecated 9.1.0 use registerAuthMechanismProvider()
+	 * @param AuthMechanism[] $mechanisms
+	 */
+	public function registerAuthMechanisms(array $mechanisms) {
+		foreach ($mechanisms as $mechanism) {
+			$this->registerAuthMechanism($mechanism);
+		}
+	}
+
+	/**
+	 * Get all backends
+	 *
+	 * @return Backend[]
+	 */
+	public function getBackends() {
+		$this->loadBackendProviders();
+		// only return real identifiers, no aliases
+		$backends = [];
+		foreach ($this->backends as $backend) {
+			$backends[$backend->getIdentifier()] = $backend;
+		}
+		return $backends;
+	}
+
+	/**
+	 * Get all available backends
+	 *
+	 * @return Backend[]
+	 */
+	public function getAvailableBackends() {
+		return array_filter($this->getBackends(), function($backend) {
+			return !($backend->checkDependencies());
+		});
+	}
+
+	/**
+	 * @param string $identifier
+	 * @return Backend|null
+	 */
+	public function getBackend($identifier) {
+		$this->loadBackendProviders();
+		if (isset($this->backends[$identifier])) {
+			return $this->backends[$identifier];
+		}
+		return null;
+	}
+
+	/**
+	 * Get all authentication mechanisms
+	 *
+	 * @return AuthMechanism[]
+	 */
+	public function getAuthMechanisms() {
+		$this->loadAuthMechanismProviders();
+		// only return real identifiers, no aliases
+		$mechanisms = [];
+		foreach ($this->authMechanisms as $mechanism) {
+			$mechanisms[$mechanism->getIdentifier()] = $mechanism;
+		}
+		return $mechanisms;
+	}
+
+	/**
+	 * Get all authentication mechanisms for schemes
+	 *
+	 * @param string[] $schemes
+	 * @return AuthMechanism[]
+	 */
+	public function getAuthMechanismsByScheme(array $schemes) {
+		return array_filter($this->getAuthMechanisms(), function($authMech) use ($schemes) {
+			return in_array($authMech->getScheme(), $schemes, true);
+		});
+	}
+
+	/**
+	 * @param string $identifier
+	 * @return AuthMechanism|null
+	 */
+	public function getAuthMechanism($identifier) {
+		$this->loadAuthMechanismProviders();
+		if (isset($this->authMechanisms[$identifier])) {
+			return $this->authMechanisms[$identifier];
+		}
+		return null;
+	}
+
+	/**
+	 * @return bool
+	 */
+	public function isUserMountingAllowed() {
+		return $this->userMountingAllowed;
+	}
+
+	/**
+	 * Check a backend if a user is allowed to mount it
+	 *
+	 * @param Backend $backend
+	 * @return bool
+	 */
+	protected function isAllowedUserBackend(Backend $backend) {
+		if ($this->userMountingAllowed &&
+			array_intersect($backend->getIdentifierAliases(), $this->userMountingBackends)
+		) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Check an authentication mechanism if a user is allowed to use it
+	 *
+	 * @param AuthMechanism $authMechanism
+	 * @return bool
+	 */
+	protected function isAllowedAuthMechanism(AuthMechanism $authMechanism) {
+		return true; // not implemented
+	}
+}