<?php
/**
 * @author Arthur Schiwon <blizzz@owncloud.com>
 * @author Bart Visscher <bartv@thisnet.nl>
 * @author Jakob Sack <mail@jakobsack.de>
 * @author Lukas Reschke <lukas@owncloud.com>
 * @author Markus Goetz <markus@woboq.com>
 * @author Michael Gapczynski <GapczynskiM@gmail.com>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Roeland Jago Douma <rullzer@owncloud.com>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 * @author Vincent Petry <pvince81@owncloud.com>
 *
 * @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\DAV\Connector\Sabre;

use Exception;
use OCP\ISession;
use OCP\IUserSession;
use Sabre\DAV\Auth\Backend\AbstractBasic;
use Sabre\DAV\Exception\NotAuthenticated;
use Sabre\DAV\Exception\ServiceUnavailable;
use Sabre\HTTP\RequestInterface;
use Sabre\HTTP\ResponseInterface;

class Auth extends AbstractBasic {
	const DAV_AUTHENTICATED = 'AUTHENTICATED_TO_DAV_BACKEND';

	/** @var ISession */
	private $session;
	/** @var IUserSession */
	private $userSession;

	/**
	 * @param ISession $session
	 * @param IUserSession $userSession
	 */
	public function __construct(ISession $session,
								IUserSession $userSession) {
		$this->session = $session;
		$this->userSession = $userSession;
		$this->principalPrefix = 'principals/users/';
	}

	/**
	 * Whether the user has initially authenticated via DAV
	 *
	 * This is required for WebDAV clients that resent the cookies even when the
	 * account was changed.
	 *
	 * @see https://github.com/owncloud/core/issues/13245
	 *
	 * @param string $username
	 * @return bool
	 */
	public function isDavAuthenticated($username) {
		return !is_null($this->session->get(self::DAV_AUTHENTICATED)) &&
		$this->session->get(self::DAV_AUTHENTICATED) === $username;
	}

	/**
	 * Validates a username and password
	 *
	 * This method should return true or false depending on if login
	 * succeeded.
	 *
	 * @param string $username
	 * @param string $password
	 * @return bool
	 */
	protected function validateUserPass($username, $password) {
		if ($this->userSession->isLoggedIn() &&
			$this->isDavAuthenticated($this->userSession->getUser()->getUID())
		) {
			\OC_Util::setupFS($this->userSession->getUser()->getUID());
			$this->session->close();
			return true;
		} else {
			\OC_Util::setUpFS(); //login hooks may need early access to the filesystem
			if($this->userSession->login($username, $password)) {
				\OC_Util::setUpFS($this->userSession->getUser()->getUID());
				$this->session->set(self::DAV_AUTHENTICATED, $this->userSession->getUser()->getUID());
				$this->session->close();
				return true;
			} else {
				$this->session->close();
				return false;
			}
		}
	}

	/**
	 * Returns information about the currently logged in username.
	 *
	 * If nobody is currently logged in, this method should return null.
	 *
	 * @return string|null
	 */
	public function getCurrentUser() {
		$user = $this->userSession->getUser() ? $this->userSession->getUser()->getUID() : null;
		if($user !== null && $this->isDavAuthenticated($user)) {
			return $user;
		}

		if($user !== null && is_null($this->session->get(self::DAV_AUTHENTICATED))) {
			return $user;
		}

		return null;
	}

	/**
	 * @param RequestInterface $request
	 * @param ResponseInterface $response
	 * @return array
	 * @throws NotAuthenticated
	 * @throws ServiceUnavailable
	 */
	function check(RequestInterface $request, ResponseInterface $response) {
		try {
			$result = $this->auth($request, $response);
			return $result;
		} catch (NotAuthenticated $e) {
			throw $e;
		} catch (Exception $e) {
			$class = get_class($e);
			$msg = $e->getMessage();
			throw new ServiceUnavailable("$class: $msg");
		}
    }

	/**
	 * @param RequestInterface $request
	 * @param ResponseInterface $response
	 * @return array
	 */
	private function auth(RequestInterface $request, ResponseInterface $response) {
		if (\OC_User::handleApacheAuth() ||
			//Fix for broken webdav clients
			($this->userSession->isLoggedIn() && is_null($this->session->get(self::DAV_AUTHENTICATED))) ||
			//Well behaved clients that only send the cookie are allowed
			($this->userSession->isLoggedIn() && $this->session->get(self::DAV_AUTHENTICATED) === $this->userSession->getUser()->getUID() && $request->getHeader('Authorization') === null)
		) {
			$user = $this->userSession->getUser()->getUID();
			\OC_Util::setupFS($user);
			$this->currentUser = $user;
			$this->session->close();
			return [true, $this->principalPrefix . $user];
		}

		if (!$this->userSession->isLoggedIn() && in_array('XMLHttpRequest', explode(',', $request->getHeader('X-Requested-With')))) {
			// do not re-authenticate over ajax, use dummy auth name to prevent browser popup
			$response->addHeader('WWW-Authenticate','DummyBasic realm="' . $this->realm . '"');
			$response->setStatus(401);
			throw new \Sabre\DAV\Exception\NotAuthenticated('Cannot authenticate over ajax calls');
		}

		return parent::check($request, $response);
	}
}