<?php
  
  /**
   * ownCloud
   *
   * @author Florin Peter
   * @copyright 2013 Florin Peter <owncloud@florin-peter.de>
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
   * License as published by the Free Software Foundation; either
   * version 3 of the License, or any later version.
   *
   * This library 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 along with this library.  If not, see <http://www.gnu.org/licenses/>.
   *
   */
  
  namespace OCA\Encryption;
  
  /**
   * @brief Class to manage registration of hooks an various helper methods
   * @package OCA\Encryption
   */
  class Helper {
  
  	/**
  	 * @brief register share related hooks
  	 *
  	 */
  	public static function registerShareHooks() {
  
  		\OCP\Util::connectHook('OCP\Share', 'pre_shared', 'OCA\Encryption\Hooks', 'preShared');
  		\OCP\Util::connectHook('OCP\Share', 'post_shared', 'OCA\Encryption\Hooks', 'postShared');
  		\OCP\Util::connectHook('OCP\Share', 'post_unshare', 'OCA\Encryption\Hooks', 'postUnshare');
  	}
  
  	/**
  	 * @brief register user related hooks
  	 *
  	 */
  	public static function registerUserHooks() {
  
  		\OCP\Util::connectHook('OC_User', 'post_login', 'OCA\Encryption\Hooks', 'login');
  		\OCP\Util::connectHook('OC_User', 'post_setPassword', 'OCA\Encryption\Hooks', 'setPassphrase');
  		\OCP\Util::connectHook('OC_User', 'pre_setPassword', 'OCA\Encryption\Hooks', 'preSetPassphrase');
  		\OCP\Util::connectHook('OC_User', 'post_createUser', 'OCA\Encryption\Hooks', 'postCreateUser');
  		\OCP\Util::connectHook('OC_User', 'post_deleteUser', 'OCA\Encryption\Hooks', 'postDeleteUser');
  	}
  
  	/**
  	 * @brief register filesystem related hooks
  	 *
  	 */
  	public static function registerFilesystemHooks() {
  
  		\OCP\Util::connectHook('OC_Filesystem', 'post_rename', 'OCA\Encryption\Hooks', 'postRename');
  	}
  
  	/**
  	 * @brief register app management related hooks
  	 *
  	 */
  	public static function registerAppHooks() {
  
  		\OCP\Util::connectHook('OC_App', 'pre_disable', 'OCA\Encryption\Hooks', 'preDisable');
  	}
  
  	/**
  	 * @brief setup user for files_encryption
  	 *
  	 * @param Util $util
  	 * @param string $password
  	 * @return bool
  	 */
  	public static function setupUser($util, $password) {
  		// Check files_encryption infrastructure is ready for action
  		if (!$util->ready()) {
  
  			\OCP\Util::writeLog('Encryption library', 'User account "' . $util->getUserId()
  													  . '" is not ready for encryption; configuration started', \OCP\Util::DEBUG);
  
  			if (!$util->setupServerSide($password)) {
  				return false;
  			}
  		}
  
  		return true;
  	}
  
  	/**
  	 * @brief enable recovery
  	 *
  	 * @param $recoveryKeyId
  	 * @param $recoveryPassword
  	 * @internal param \OCA\Encryption\Util $util
  	 * @internal param string $password
  	 * @return bool
  	 */
  	public static function adminEnableRecovery($recoveryKeyId, $recoveryPassword) {
  
  		$view = new \OC\Files\View('/');
  
  		if ($recoveryKeyId === null) {
  			$recoveryKeyId = 'recovery_' . substr(md5(time()), 0, 8);
  			\OC_Appconfig::setValue('files_encryption', 'recoveryKeyId', $recoveryKeyId);
  		}
  
  		if (!$view->is_dir('/owncloud_private_key')) {
  			$view->mkdir('/owncloud_private_key');
  		}
  
  		if (
  			(!$view->file_exists("/public-keys/" . $recoveryKeyId . ".public.key")
  			 || !$view->file_exists("/owncloud_private_key/" . $recoveryKeyId . ".private.key"))
  		) {
  
  			$keypair = \OCA\Encryption\Crypt::createKeypair();
  
  			\OC_FileProxy::$enabled = false;
  
  			// Save public key
  
  			if (!$view->is_dir('/public-keys')) {
  				$view->mkdir('/public-keys');
  			}
  
  			$view->file_put_contents('/public-keys/' . $recoveryKeyId . '.public.key', $keypair['publicKey']);
  
  			// Encrypt private key empty passphrase
  			$encryptedPrivateKey = \OCA\Encryption\Crypt::symmetricEncryptFileContent($keypair['privateKey'], $recoveryPassword);
  
  			// Save private key
  			$view->file_put_contents('/owncloud_private_key/' . $recoveryKeyId . '.private.key', $encryptedPrivateKey);
  
  			\OC_FileProxy::$enabled = true;
  
  			// Set recoveryAdmin as enabled
  			\OC_Appconfig::setValue('files_encryption', 'recoveryAdminEnabled', 1);
  
  			$return = true;
  
  		} else { // get recovery key and check the password
  			$util = new \OCA\Encryption\Util(new \OC_FilesystemView('/'), \OCP\User::getUser());
  			$return = $util->checkRecoveryPassword($recoveryPassword);
  			if ($return) {
  				\OC_Appconfig::setValue('files_encryption', 'recoveryAdminEnabled', 1);
  			}
  		}
  
  		return $return;
  	}
  
  
  	/**
  	 * @brief disable recovery
  	 *
  	 * @param $recoveryPassword
  	 * @return bool
  	 */
  	public static function adminDisableRecovery($recoveryPassword) {
  		$util = new Util(new \OC_FilesystemView('/'), \OCP\User::getUser());
  		$return = $util->checkRecoveryPassword($recoveryPassword);
  
  		if ($return) {
  			// Set recoveryAdmin as disabled
  			\OC_Appconfig::setValue('files_encryption', 'recoveryAdminEnabled', 0);
  		}
  
  		return $return;
  	}
  
  
  	/**
  	 * @brief checks if access is public/anonymous user
  	 * @return bool
  	 */
  	public static function isPublicAccess() {
  		if (\OCP\USER::getUser() === false
  			|| (isset($_GET['service']) && $_GET['service'] == 'files'
  				&& isset($_GET['t']))
  		) {
  			return true;
  		} else {
  			return false;
  		}
  	}
  
  	/**
  	 * @brief Format a path to be relative to the /user/files/ directory
  	 * @param string $path the absolute path
  	 * @return string e.g. turns '/admin/files/test.txt' into 'test.txt'
  	 */
  	public static function stripUserFilesPath($path) {
  		$trimmed = ltrim($path, '/');
  		$split = explode('/', $trimmed);
  		$sliced = array_slice($split, 2);
  		$relPath = implode('/', $sliced);
  
  		return $relPath;
  	}
  
  	/**
  	 * @brief redirect to a error page
  	 */
  	public static function redirectToErrorPage() {
  		$location = \OC_Helper::linkToAbsolute('apps/files_encryption/files', 'error.php');
  		$post = 0;
  		if(count($_POST) > 0) {
  			$post = 1;
  		}
  		header('Location: ' . $location . '?p=' . $post);
  		exit();
  	}
  
  	/**
  	 * check requirements for encryption app.
  	 * @return bool true if requirements are met
  	 */
  	public static function checkRequirements() {
  		$result = true;
  
  		//openssl extension needs to be loaded
  		$result &= extension_loaded("openssl");
  		// we need php >= 5.3.3
  		$result &= version_compare(phpversion(), '5.3.3', '>=');
  
  		return (bool) $result;
  	}
  	
  	/**
  	 * check some common errors if the server isn't configured properly for encryption
  	 * @return bool true if configuration seems to be OK
  	 */
  	public static function checkConfiguration() {
  		if(openssl_pkey_new(array('private_key_bits' => 4096))) {
  			return true;
  		} else {
  			while ($msg = openssl_error_string()) {
  				\OCP\Util::writeLog('Encryption library', 'openssl_pkey_new() fails:  ' . $msg, \OCP\Util::ERROR);
  			}
  			return false;
  		}
  	}
  
  	/**
  	 * @brief glob uses different pattern than regular expressions, escape glob pattern only
  	 * @param unescaped path
  	 * @return escaped path
  	 */
  	public static function escapeGlobPattern($path) {
  		return preg_replace('/(\*|\?|\[)/', '[$1]', $path);
  	}
  }