diff --git a/lib/api/document.php b/lib/api/document.php
index 8886a38..2f22d29 100644
--- a/lib/api/document.php
+++ b/lib/api/document.php
@@ -1,211 +1,242 @@
 <?php
 /**
  +--------------------------------------------------------------------------+
  | This file is part of the Kolab File API                                  |
  |                                                                          |
  | Copyright (C) 2012-2015, Kolab Systems AG                                |
  |                                                                          |
  | This program is free software: you can redistribute it and/or modify     |
  | it under the terms of the GNU Affero General Public License as published |
  | by the Free Software Foundation, either version 3 of the License, or     |
  | (at your option) any later version.                                      |
  |                                                                          |
  | 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 |
  | along with this program. If not, see <http://www.gnu.org/licenses/>      |
  +--------------------------------------------------------------------------+
  | Author: Aleksander Machniak <machniak@kolabsys.com>                      |
  +--------------------------------------------------------------------------+
 */
 
 class file_api_document extends file_api_common
 {
     /**
      * Request handler
      */
     public function handle()
     {
         $method     = $_SERVER['REQUEST_METHOD'];
         $this->args = $_GET;
 
         if ($method == 'POST' && !empty($_SERVER['HTTP_X_HTTP_METHOD'])) {
             $method = $_SERVER['HTTP_X_HTTP_METHOD'];
         }
 
-        // Sessions and invitations management
-        if (strpos($this->args['method'], 'document_') === 0) {
+        // Invitation notifications
+        if ($this->args['method'] == 'invitations') {
+            return $this->invitations();
+        }
+        // Session and invitations management
+        else if (strpos($this->args['method'], 'document_') === 0) {
             if ($_SERVER['REQUEST_METHOD'] == 'POST') {
                 $post = file_get_contents('php://input');
                 $this->args += (array) json_decode($post, true);
                 unset($post);
             }
 
             if (empty($this->args['id'])) {
                 throw new Exception("Missing document ID.", file_api_core::ERROR_CODE);
             }
  
             switch ($this->args['method']) {
                 case 'document_delete':
                     return $this->document_delete($this->args['id']);
 
                 case 'document_invite':
                     return $this->document_invite($this->args['id']);
 
 //                case 'document_request':
 //                case 'document_decline':
 //                case 'document_accept':
                 case 'document_remove':
                     return $this->document_remove($this->args['id']);
             }
         }
         // Document content actions for Manticore
         else if ($method == 'PUT' || $method == 'GET') {
             if (empty($this->args['id'])) {
                 throw new Exception("Missing document ID.", file_api_core::ERROR_CODE);
             }
 
             $file = $this->get_file_path($this->args['id']);
 
             return $this->{'document_' . strtolower($method)}($file);
         }
 
         throw new Exception("Unknown method", file_api_core::ERROR_INVALID);
     }
 
     /**
      * Get file path from manticore session identifier
      */
     protected function get_file_path($id)
     {
         $manticore = new file_manticore($this->api);
 
         return $manticore->session_file($id);
     }
 
+    /**
+     * Get invitations list
+     */
+    protected function invitations()
+    {
+        $timestamp = time();
+
+        // Initial tracking request, return just the current timestamp
+        if ($this->args['timestamp'] == -1) {
+            return array('timestamp' => $timestamp);
+        }
+
+        $manticore = new file_manticore($this->api);
+        $filter    = array();
+
+        if ($this->args['timestamp']) {
+            $filter['timestamp'] = $this->args['timestamp'];
+        }
+
+        $list = $manticore->invitations_list($filter);
+
+        return array(
+            'list'      => $list,
+            'timestamp' => $timestamp,
+        );
+    }
+
     /**
      * Close (delete) manticore session
      */
     protected function document_delete($id)
     {
         $manticore = new file_manticore($this->api);
 
         if (!$manticore->session_delete($id)) {
             throw new Exception("Failed deleting the document session.", file_api_core::ERROR_CODE);
         }
     }
 
     /**
      * Invite/add a session participant(s)
      */
     protected function document_invite($id)
     {
         $manticore = new file_manticore($this->api);
         $users     = $this->args['users'];
 
         if (empty($users)) {
             throw new Exception("Invalid arguments.", file_api_core::ERROR_CODE);
         }
 
         foreach ((array) $users as $user) {
             if (!empty($user['user'])) {
                 $manticore->invitation_create($id, $user['user'], file_manticore::STATUS_INVITED);
 
                 $result[] = array(
                     'session_id' => $id,
                     'user'       => $user['user'],
 //                    'name' => $user['name'],
                     'status'     => file_manticore::STATUS_INVITED,
                 );
             }
         }
 
         return array(
             'list' => $result,
         );
     }
 
     /**
      * Remove a session participant(s)
      */
     protected function document_remove($id)
     {
         $manticore = new file_manticore($this->api);
         $users     = $this->args['users'];
 
         if (empty($users)) {
             throw new Exception("Invalid arguments.", file_api_core::ERROR_CODE);
         }
 
         foreach ((array) $users as $user) {
             $manticore->invitation_delete($id, $user);
             $result[] = $user;
         }
 
         return array(
             'list' => $result,
         );
     }
 
     /**
      * Update document file content
      */
     protected function document_put($file)
     {
         list($driver, $path) = $this->api->get_driver($file);
 
         $length   = rcube_utils::request_header('Content-Length');
         $tmp_dir  = unslashify($this->api->config->get('temp_dir'));
         $tmp_path = tempnam($tmp_dir, 'chwalaUpload');
 
         // Create stream to copy input into a temp file
         $input    = fopen('php://input', 'r');
         $tmp_file = fopen($tmp_path, 'w');
 
         if (!$input || !$tmp_file) {
             throw new Exception("Failed opening input or temp file stream.", file_api_core::ERROR_CODE);
         }
 
         // Create temp file from the input
         $copied = stream_copy_to_stream($input, $tmp_file);
 
         fclose($input);
         fclose($tmp_file);
 
         if ($copied < $length) {
             throw new Exception("Failed writing to temp file.", file_api_core::ERROR_CODE);
         }
 
         $file = array(
             'path' => $tmp_path,
             'type' => rcube_mime::file_content_type($tmp_path, $file),
         );
 
         $driver->file_update($path, $file);
 
         // remove the temp file
         unlink($tmp_path);
     }
 
     /**
      * Return document file content
      */
     protected function document_get($file)
     {
         list($driver, $path) = $this->api->get_driver($file);
 
         try {
             $params = array('force-type' => 'application/vnd.oasis.opendocument.text');
 
             $driver->file_get($path, $params);
         }
         catch (Exception $e) {
             header("HTTP/1.0 " . file_api_core::ERROR_CODE . " " . $e->getMessage());
         }
 
         exit;
     }
 }
diff --git a/lib/file_api.php b/lib/file_api.php
index e5706ac..f9f9a8c 100644
--- a/lib/file_api.php
+++ b/lib/file_api.php
@@ -1,442 +1,442 @@
 <?php
 /*
  +--------------------------------------------------------------------------+
  | This file is part of the Kolab File API                                  |
  |                                                                          |
  | Copyright (C) 2012-2013, Kolab Systems AG                                |
  |                                                                          |
  | This program is free software: you can redistribute it and/or modify     |
  | it under the terms of the GNU Affero General Public License as published |
  | by the Free Software Foundation, either version 3 of the License, or     |
  | (at your option) any later version.                                      |
  |                                                                          |
  | 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 |
  | along with this program. If not, see <http://www.gnu.org/licenses/>      |
  +--------------------------------------------------------------------------+
  | Author: Aleksander Machniak <machniak@kolabsys.com>                      |
  +--------------------------------------------------------------------------+
 */
 
 class file_api extends file_api_core
 {
     public $session;
     public $config;
     public $browser;
     public $output_type = file_api_core::OUTPUT_JSON;
 
 
     public function __construct()
     {
         $rcube = rcube::get_instance();
         $rcube->add_shutdown_function(array($this, 'shutdown'));
 
         $this->config = $rcube->config;
         $this->session_init();
 
         if ($_SESSION['env']) {
             $this->env = $_SESSION['env'];
         }
 
         $this->locale_init();
     }
 
     /**
      * Process the request and dispatch it to the requested service
      */
     public function run()
     {
         $this->request = strtolower($_GET['method']);
 
         // Check the session, authenticate the user
         if (!$this->session_validate()) {
             $this->session->destroy(session_id());
             $this->session->regenerate_id(false);
 
             if ($username = $this->authenticate()) {
                 $_SESSION['user'] = $username;
                 $_SESSION['time'] = time();
                 $_SESSION['env']  = $this->env;
 
                 // remember client API version
                 if (is_numeric($_GET['version'])) {
                     $_SESSION['version'] = $_GET['version'];
                 }
 
                 if ($this->request == 'authenticate') {
                     $this->output_success(array(
                         'token'        => session_id(),
                         'capabilities' => $this->capabilities(),
                     ));
                 }
             }
             else {
                 throw new Exception("Invalid session", 403);
             }
         }
 
         // Call service method
         $result = $this->request_handler($this->request);
 
         // Send success response, errors should be handled by driver class
         // by throwing exceptions or sending output by itself
         $this->output_success($result);
     }
 
     /**
      * Session validation check and session start
      */
     private function session_validate()
     {
         $sess_id = rcube_utils::request_header('X-Session-Token') ?: $_REQUEST['token'];
 
         if (empty($sess_id)) {
             session_start();
             return false;
         }
 
         session_id($sess_id);
         session_start();
 
         if (empty($_SESSION['user'])) {
             return false;
         }
 
         $timeout = $this->config->get('session_lifetime', 0) * 60;
         if ($timeout && $_SESSION['time'] && $_SESSION['time'] < time() - $timeout) {
             return false;
         }
         // update session time
         $_SESSION['time'] = time();
 
         return true;
     }
 
     /**
      * Initializes session
      */
     private function session_init()
     {
         $rcube     = rcube::get_instance();
         $sess_name = $this->config->get('session_name');
         $lifetime  = $this->config->get('session_lifetime', 0) * 60;
 
         if ($lifetime) {
             ini_set('session.gc_maxlifetime', $lifetime * 2);
         }
 
         ini_set('session.name', $sess_name ? $sess_name : 'file_api_sessid');
         ini_set('session.use_cookies', 0);
         ini_set('session.serialize_handler', 'php');
 
         // Roundcube Framework >= 1.2
         if (in_array('factory', get_class_methods('rcube_session'))) {
             $this->session = rcube_session::factory($this->config);
         }
         // Rouncube Framework < 1.2
         else {
             $this->session = new rcube_session($rcube->get_dbh(), $this->config);
             $this->session->set_secret($this->config->get('des_key') . dirname($_SERVER['SCRIPT_NAME']));
             $this->session->set_ip_check($this->config->get('ip_check'));
         }
 
         $this->session->register_gc_handler(array($rcube, 'gc'));
 
         // this is needed to correctly close session in shutdown function
         $rcube->session = $this->session;
     }
 
     /**
      * Script shutdown handler
      */
     public function shutdown()
     {
         // write performance stats to logs/console
         if ($this->config->get('devel_mode')) {
             if (function_exists('memory_get_peak_usage'))
                 $mem = memory_get_peak_usage();
             else if (function_exists('memory_get_usage'))
                 $mem = memory_get_usage();
 
             $log = trim($this->request . ($mem ? sprintf(' [%.1f MB]', $mem/1024/1024) : ''));
             if (defined('FILE_API_START')) {
                 rcube::print_timer(FILE_API_START, $log);
             }
             else {
                 rcube::console($log);
             }
         }
     }
 
     /**
      * Authentication request handler (HTTP Auth)
      */
     private function authenticate()
     {
         if (isset($_POST['username'])) {
             $username = $_POST['username'];
             $password = $_POST['password'];
         }
         else if (!empty($_SERVER['PHP_AUTH_USER'])) {
             $username = $_SERVER['PHP_AUTH_USER'];
             $password = $_SERVER['PHP_AUTH_PW'];
         }
         // when used with (f)cgi no PHP_AUTH* variables are available without defining a special rewrite rule
         else if (!isset($_SERVER['PHP_AUTH_USER'])) {
             // "Basic didhfiefdhfu4fjfjdsa34drsdfterrde..."
             if (isset($_SERVER["REMOTE_USER"])) {
                 $basicAuthData = base64_decode(substr($_SERVER["REMOTE_USER"], 6));
             }
             else if (isset($_SERVER["REDIRECT_REMOTE_USER"])) {
                 $basicAuthData = base64_decode(substr($_SERVER["REDIRECT_REMOTE_USER"], 6));
             }
             else if (isset($_SERVER["Authorization"])) {
                 $basicAuthData = base64_decode(substr($_SERVER["Authorization"], 6));
             }
             else if (isset($_SERVER["HTTP_AUTHORIZATION"])) {
                 $basicAuthData = base64_decode(substr($_SERVER["HTTP_AUTHORIZATION"], 6));
             }
 
             if (isset($basicAuthData) && !empty($basicAuthData)) {
                 list($username, $password) = explode(":", $basicAuthData);
             }
         }
 
         if (!empty($username)) {
             $backend = $this->get_backend();
             $result  = $backend->authenticate($username, $password);
 
             if (empty($result)) {
 /*
                 header('WWW-Authenticate: Basic realm="' . $this->app_name .'"');
                 header('HTTP/1.1 401 Unauthorized');
                 exit;
 */
                 throw new Exception("Invalid password or username", file_api_core::ERROR_CODE);
             }
         }
 
         return $username;
     }
 
     /**
      * Storage/System method handler
      */
     private function request_handler($request)
     {
         // handle "global" requests that don't require api driver
         switch ($request) {
             case 'ping':
                 return array();
 
             case 'quit':
                 $this->session->destroy(session_id());
                 return array();
 
             case 'configure':
                 foreach (array_keys($this->env) as $name) {
                     if (isset($_GET[$name])) {
                         $this->env[$name] = $_GET[$name];
                     }
                 }
                 $_SESSION['env'] = $this->env;
 
                 return $this->env;
 
             case 'upload_progress':
                 return $this->upload_progress();
 
             case 'mimetypes':
                 return $this->supported_mimetypes();
 
             case 'capabilities':
                 return $this->capabilities();
         }
 
         // handle request
         if ($request && preg_match('/^[a-z0-9_-]+$/', $request)) {
             $aliases = array(
                 // request name aliases for backward compatibility
                 'lock'          => 'lock_create',
                 'unlock'        => 'lock_delete',
                 'folder_rename' => 'folder_move',
             );
 
             // Redirect all document_* actions into 'document' action
-            if (strpos($request, 'document_') === 0) {
+            if (preg_match('/^(invitations|document_[a-z]+)$/', $request)) {
                 $request = 'document';
             }
 
             $request = $aliases[$request] ?: $request;
 
             require_once __DIR__ . "/api/common.php";
             include_once __DIR__ . "/api/$request.php";
 
             $class_name = "file_api_$request";
             if (class_exists($class_name, false)) {
                 $handler = new $class_name($this);
                 return $handler->handle();
             }
         }
 
         throw new Exception("Unknown method", file_api_core::ERROR_INVALID);
     }
 
     /**
      * File upload progress handler
      */
     protected function upload_progress()
     {
         if (function_exists('apc_fetch')) {
             $prefix   = ini_get('apc.rfc1867_prefix');
             $uploadid = rcube_utils::get_input_value('id', rcube_utils::INPUT_GET);
             $status   = apc_fetch($prefix . $uploadid);
 
             if (!empty($status)) {
                 $status['percent'] = round($status['current']/$status['total']*100);
                 if ($status['percent'] < 100) {
                     $diff = max(1, time() - intval($status['start_time']));
                     // calculate time to end of uploading (in seconds)
                     $status['eta'] = intval($diff * (100 - $status['percent']) / $status['percent']);
                     // average speed (bytes per second)
                     $status['rate'] = intval($status['current'] / $diff);
                 }
             }
 
             $status['id'] = $uploadid;
 
             return $status; // id, done, total, current, percent, start_time, eta, rate
         }
 
         throw new Exception("Not supported", file_api_core::ERROR_CODE);
     }
 
     /**
      * Returns complete File URL
      *
      * @param string $file File name (with path)
      *
      * @return string File URL
      */
     public function file_url($file)
     {
         return file_utils::script_uri(). '?method=file_get'
             . '&file=' . urlencode($file)
             . '&token=' . urlencode(session_id());
     }
 
     /**
      * Returns web browser object
      *
      * @return rcube_browser Web browser object
      */
     public function get_browser()
     {
         if ($this->browser === null) {
             $this->browser = new rcube_browser;
         }
 
         return $this->browser;
     }
 
     /**
      * Send success response
      *
      * @param mixed $data Data
      */
     public function output_success($data)
     {
         if (!is_array($data)) {
             $data = array();
         }
 
         $response = array('status' => 'OK', 'result' => $data);
 
         if (!empty($_REQUEST['req_id'])) {
             $response['req_id'] = $_REQUEST['req_id'];
         }
 
         $this->output_send($response);
     }
 
     /**
      * Send error response
      *
      * @param mixed $response Response data
      * @param int   $code     Error code
      */
     public function output_error($response, $code = null)
     {
         if (is_string($response)) {
             $response = array('reason' => $response);
         }
 
         $response['status'] = 'ERROR';
 
         if ($code) {
             $response['code'] = $code;
         }
 
         if (!empty($_REQUEST['req_id'])) {
             $response['req_id'] = $_REQUEST['req_id'];
         }
 
         if (empty($response['code'])) {
             $response['code'] = file_api_core::ERROR_CODE;
         }
 
         $this->output_send($response);
     }
 
     /**
      * Send response
      *
      * @param mixed $data Data
      */
     protected function output_send($data)
     {
         // Send response
         header("Content-Type: {$this->output_type}; charset=utf-8");
         echo json_encode($data);
         exit;
     }
 
     /**
      * Returns API version supported by the client
      */
     public function client_version()
     {
         return $_SESSION['version'];
     }
 
     /**
      * Create a human readable string for a number of bytes
      *
      * @param int Number of bytes
      *
      * @return string Byte string
      */
     public function show_bytes($bytes)
     {
         if ($bytes >= 1073741824) {
             $gb  = $bytes/1073741824;
             $str = sprintf($gb >= 10 ? "%d " : "%.1f ", $gb) . 'GB';
         }
         else if ($bytes >= 1048576) {
             $mb  = $bytes/1048576;
             $str = sprintf($mb >= 10 ? "%d " : "%.1f ", $mb) . 'MB';
         }
         else if ($bytes >= 1024) {
             $str = sprintf("%d ",  round($bytes/1024)) . 'KB';
         }
         else {
             $str = sprintf('%d ', $bytes) . 'B';
         }
 
         return $str;
     }
 }
diff --git a/lib/file_manticore.php b/lib/file_manticore.php
index 7f10db3..46b04e7 100644
--- a/lib/file_manticore.php
+++ b/lib/file_manticore.php
@@ -1,567 +1,624 @@
 <?php
 /**
  +--------------------------------------------------------------------------+
  | This file is part of the Kolab File API                                  |
  |                                                                          |
  | Copyright (C) 2012-2015, Kolab Systems AG                                |
  |                                                                          |
  | This program is free software: you can redistribute it and/or modify     |
  | it under the terms of the GNU Affero General Public License as published |
  | by the Free Software Foundation, either version 3 of the License, or     |
  | (at your option) any later version.                                      |
  |                                                                          |
  | 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 |
  | along with this program. If not, see <http://www.gnu.org/licenses/>      |
  +--------------------------------------------------------------------------+
  | Author: Aleksander Machniak <machniak@kolabsys.com>                      |
  +--------------------------------------------------------------------------+
 */
 
 /**
  * Document editing sessions handling
  */
 class file_manticore
 {
     protected $api;
     protected $rc;
     protected $request;
     protected $sessions_table    = 'chwala_sessions';
     protected $invitations_table = 'chwala_invitations';
 
     const STATUS_INVITED   = 'invited';
     const STATUS_REQUESTED = 'requested';
     const STATUS_ACCEPTED  = 'accepted';
     const STATUS_DECLINED  = 'declined';
 
 
     /**
      * Class constructor
      *
      * @param file_api Chwala API app instance
      */
     public function __construct($api)
     {
         $this->rc  = rcube::get_instance();
         $this->api = $api;
 
         $db = $this->rc->get_dbh();
         $this->sessions_table    = $db->table_name($this->sessions_table);
         $this->invitations_table = $db->table_name($this->invitations_table);
     }
 
     /**
      * Return viewer URI for specified file/session. This creates
      * a new collaborative editing session when needed.
      *
      * @param string $file        File path
      * @param string &$session_id Optional session ID to join to
      *
      * @return string Manticore URI
      * @throws Exception
      */
     public function session_start($file, &$session_id = null)
     {
         list($driver, $path) = $this->api->get_driver($file);
 
         $backend = $this->api->get_backend();
         $uri     = $driver->path2uri($path);
 
         if ($session_id) {
             $session = $this->session_info($session_id);
 
             if (empty($session)) {
                 throw new Exception("Document session not found.", file_api_core::ERROR_CODE);
             }
 
             // check session ownership
             if ($session['owner'] != $_SESSION['user']) {
                 // check if the user was invited
-                $invitations = $this->invitations_list($session_id);
+                $invitations = $this->invitations_find(array('session_id' => $session_id, 'user' => $_SESSION['user']));
                 $states      = array(self::STATUS_DECLINED, self::STATUS_REQUESTED);
 
                 if (empty($invitations) || in_array($invitations[0]['status'], $states)) {
                     throw new Exception("No permission to join the editing session.", file_api_core::ERROR_CODE);
                 }
 
                 // automatically accept the invitation, if not done yet
                 if ($invitations[0]['status'] == self::STATUS_INVITED) {
                     $this->invitation_update($session_id, $_SESSION['user'], self::STATUS_ACCEPTED);
                 }
             }
 
             // authenticate to Manticore, we need auth token for frame_uri
             $req = $this->get_request();
 
             // @TODO: make sure the session exists in Manticore?
         }
         else {
             // @TODO: to prevent from creating a new sessions for the same file+user
             // (e.g. when user uses F5 to refresh the page), we should check
             // if such a session exist
 
             $session_id = rcube_utils::bin2ascii(md5(time() . $uri, true));
             $data       = array();
             $owner      = $_SESSION['user'];
 
             // we'll store user credentials if the file comes from
             // an external source that requires authentication
             if ($backend != $driver) {
                 $auth = $driver->auth_info();
                 $auth['password']  = $this->rc->encrypt($auth['password']);
                 $data['auth_info'] = $auth;
             }
 
             $res = $this->session_create($session_id, $uri, $owner, $data);
 
             if (!$res) {
                 throw new Exception("Failed creating document editing session", file_api_core::ERROR_CODE);
             }
         }
 
         return $this->frame_uri($session_id);
     }
 
     /**
      * Get file path (not URI) from session.
      *
      * @param string $id Session ID
      *
      * @return string File path
      * @throws Exception
      */
     public function session_file($id)
     {
         $session = $this->session_info($id);
 
         if (empty($session)) {
             throw new Exception("Document session not found.", file_api_core::ERROR_CODE);
         }
 
         $path = $this->uri2path($session['uri']);
 
         if (empty($path)) {
             throw new Exception("Document session not found.", file_api_core::ERROR_CODE);
         }
 
         // @TODO: check permissions to the session
 
         return $path;
     }
 
     /**
      * Get editing session info
      *
      * @param string $id               Session identifier
      * @param bool   $with_invitations Return invitations list
      */
     public function session_info($id, $with_invitations = false)
     {
         $db     = $this->rc->get_dbh();
         $result = $db->query("SELECT * FROM `{$this->sessions_table}`"
             . " WHERE `id` = ?", $id);
 
         if ($row = $db->fetch_assoc($result)) {
             $session = $this->session_info_parse($row);
 
             if ($with_invitations && $session['is_owner']) {
                 $session['invitations'] = $this->invitations_find(array('session_id' => $id));
             }
 
             return $session;
         }
     }
 
     /**
      * Find editing sessions for specified path
      */
     public function session_find($path, $invitations = true)
     {
         // create an URI for specified path
         list($driver, $path) = $this->api->get_driver($path);
 
         $uri = trim($driver->path2uri($path), '/') . '/';
 
         // get existing sessions
         $sessions = array();
         $filter   = array('file', 'owner', 'is_owner');
         $db       = $this->rc->get_dbh();
         $result   = $db->query("SELECT * FROM `{$this->sessions_table}`"
             . " WHERE `uri` LIKE '" . $db->escape($uri) . "%'");
 
         while ($row = $db->fetch_assoc($result)) {
             if ($path = $this->uri2path($row['uri'])) {
                 $sessions[$row['id']] = $this->session_info_parse($row, $path, $filter);
             }
         }
 
         // set 'is_invited' flag
         if ($invitations && !empty($sessions)) {
-            $invitations = $this->invitations_list();
+            $invitations = $this->invitations_find(array('user' => $_SESSION['user']));
             $states      = array(self::STATUS_INVITED, self::STATUS_ACCEPTED);
 
             foreach ($invitations as $invitation) {
                 if (!empty($sessions[$invitation['session_id']]) && in_array($invitation['status'], $states)) {
                     $sessions[$invitation['session_id']]['is_invited'] = true;
                 }
             }
         }
 
         return $sessions;
     }
 
     /**
      * Delete editing session (only owner can do that)
      *
      * @param string $id    Session identifier
      * @param bool   $local Remove session only from local database
      */
     public function session_delete($id, $local = false)
     {
         $db     = $this->rc->get_dbh();
         $result = $db->query("DELETE FROM `{$this->sessions_table}`"
             . " WHERE `id` = ? AND `owner` = ?",
             $id, $_SESSION['user']);
 
         $success = $db->affected_rows($result) > 0;
 
         // Send document delete to Manticore
         if ($success && !$local) {
             $req = $this->get_request();
             $res = $req->document_delete($id);
         }
 
         return $success;
     }
 
     /**
      * Create editing session
      */
     protected function session_create($id, $uri, $owner, $data)
     {
         // Do this before starting the session in Manticore,
         // it will immediately call api/document to get the file body
         $db     = $this->rc->get_dbh();
         $result = $db->query("INSERT INTO `{$this->sessions_table}`"
             . " (`id`, `uri`, `owner`, `data`) VALUES (?, ?, ?, ?)",
             $id, $uri, $owner, json_encode($data));
 
         $success = $db->affected_rows($result) > 0;
 
         // create the session in Manticore
         if ($success) {
             $req = $this->get_request();
             $res = $req->document_create(array(
                 'id'     => $id,
                 'title'  => '', // @TODO: maybe set to a file path without extension?
                 'access' => array(
                     array(
                         'identity'   => $owner,
                         'permission' => file_manticore_api::ACCESS_WRITE,
                     ),
                 ),
             ));
 
             if (!$res) {
                 $this->session_delete($id, true);
                 return false;
             }
         }
 
         return $success;
     }
 
     /**
-     * Find invitations for current user
-     *
+     * Find invitations for current user. This will return all
+     * invitations related to the user including his sessions.
      *
+     * @param array $filter Search filter (see self::invitations_find())
      *
      * @return array Invitations list
      */
-    public function invitations_list($session_id = null)
+    public function invitations_list($filter = array())
     {
-        $invitations = array();
-        $db          = $this->rc->get_dbh();
-        $result      = $db->query("SELECT * FROM `{$this->invitations_table}`"
-            . " WHERE `user`= ?"
-            . ($session_id ? " AND `session_id` = " . $db->quote($session_id) : "")
-            . " ORDER BY `changed`", $_SESSION['user']);
+        $filter['user'] = $_SESSION['user'];
 
-        while ($row = $db->fetch_assoc($result)) {
-            $invitations[] = $row;
+        // list of invitations to the user or requested by him
+        $result = $this->invitations_find($filter, true);
+
+        unset($filter['user']);
+        $filter['owner'] = $_SESSION['user'];
+
+        // other invitations that belong to the sessions owned by the user
+        if ($other = $this->invitations_find($filter, true)) {
+            $result = array_merge($result, $other);
         }
 
-        return $invitations;
+        return $result;
     }
 
     /**
-     * Find invitations for specified session_id
+     * Find invitations for specified filter
+     *
+     * @param array $filter Search filter (see self::invitations_find())
+     *                      - session_id: session identifier
+     *                      - timestamp: "changed > ?" filter
+     *                      - user: Invitation user identifier
+     *                      - owner: Session owner identifier
+     * @param bool $extended Return session file names
+     *
+     * @return array Invitations list
      */
-    public function invitations_find($filter)
+    public function invitations_find($filter, $extended = false)
     {
-        $invitations = array();
-        $db          = $this->rc->get_dbh();
+        $db     = $this->rc->get_dbh();
+        $query  = '';
+        $select = "i.*";
 
         foreach ($filter as $column => $value) {
-            $filter[$column] = "`$column` = " . $db->quote($value);
+            if ($column == 'timestamp') {
+                $where[] = "i.`changed` > " . $db->fromunixtime($value);
+            }
+            else if ($column == 'owner') {
+                $join[] = "`{$this->sessions_table}` s ON (i.`session_id` = s.`id`)";
+                $where[] = "s.`owner` = " . $db->quote($value);
+            }
+            else {
+                $where[] = "i.`$column` = " . $db->quote($value);
+            }
         }
 
-        $where  = implode(' AND ', $filter);
-        $result = $db->query("SELECT * FROM `{$this->invitations_table}`"
-            . " WHERE $where ORDER BY `changed`");
+        if ($extended) {
+            $select .= ", s.`uri`";
+            $join[]  = "`{$this->sessions_table}` s ON (i.`session_id` = s.`id`)";
+        }
+
+        if (!empty($join)) {
+            $query .= ' JOIN ' . implode(' JOIN ', array_unique($join));
+        }
+
+        if (!empty($where)) {
+            $query .= ' WHERE ' . implode(' AND ', array_unique($where));
+        }
+
+        $result = $db->query("SELECT $select FROM `{$this->invitations_table}` i"
+            . "$query ORDER BY `changed`");
+
+        if ($db->is_error($result)) {
+            throw new Exception("Internal error.", file_api_core::ERROR_CODE);
+        }
+
+        $invitations = array();
 
         while ($row = $db->fetch_assoc($result)) {
+            if ($extended) {
+                try {
+                    // add unix-timestamp of the `changed` date to the result
+                    $dt = new DateTime($row['changed']);
+                    $row['timestamp'] = $dt->format('U');
+                }
+                catch(Exception $e) { }
+
+                // add filename to the result
+                $filename = parse_url($row['uri'], PHP_URL_PATH);
+                $filename = pathinfo($filename, PATHINFO_BASENAME);
+                $filename = rawurldecode($filename);
+
+                $row['filename'] = $filename;
+                unset($row['uri']);
+            }
+
             $invitations[] = $row;
         }
 
         return $invitations;
     }
 
     /**
      * Create an invitation
      *
      * @param string $session_id Document session identifier
      * @param string $user       User identifier
      * @param string $status     Invitation status (invited, requested)
      *
      * @throws Exception
      */
     public function invitation_create($session_id, $user, $status = 'invited')
     {
         if ($status != self::STATUS_INVITED && $status != self::STATUS_REQUESTED) {
             throw new Exception("Invalid invitation status.", file_api_core::ERROR_CODE);
         }
 
         // get session information
         $session = $this->session_info($session_id);
 
         if (empty($session)) {
             throw new Exception("Document session not found.", file_api_core::ERROR_CODE);
         }
 
         // check session ownership, only owner can create 'new' invitations
         if ($status == self::STATUS_INVITED && $session['owner'] != $_SESSION['user']) {
             throw new Exception("No permission to create an invitation.", file_api_core::ERROR_CODE);
         }
 
         if ($session['owner'] == $user) {
             throw new Exception("Not possible to create an invitation for the session creator.", file_api_core::ERROR_CODE);
         }
 
         // Update Manticore 'access' array
         if ($status == self::STATUS_INVITED) {
             $req = $this->get_request();
             $res = $req->editor_add($session_id, $user, file_manticore_api::ACCESS_WRITE);
 
             if (!$res) {
                 throw new Exception("Failed to create an invitation.", file_api_core::ERROR_CODE);
             }
         }
 
         // insert invitation
         $db     = $this->rc->get_dbh();
         $result = $db->query("INSERT INTO `{$this->invitations_table}`"
             . " (`session_id`, `user`, `status`, `changed`)"
             . " VALUES (?, ?, ?, " . $db->now() . ")",
             $session_id, $user, $status);
 
         if (!$db->affected_rows($result)) {
             throw new Exception("Failed to create an invitation.", file_api_core::ERROR_CODE);
         }
     }
 
     /**
      * Delete an invitation (only session owner can do that)
      *
      * @param string $session_id Session identifier
      * @param string $user       User identifier
      *
      * @throws Exception
      */
     public function invitation_delete($session_id, $user)
     {
         $db     = $this->rc->get_dbh();
         $result = $db->query("DELETE FROM `{$this->invitations_table}`"
             . " WHERE `session_id` = ? AND `user` = ?"
                 . " AND EXISTS (SELECT 1 FROM `{$this->sessions_table}` WHERE `id` = ? AND `owner` = ?)",
             $session_id, $user, $session_id, $_SESSION['user']);
 
         if (!$db->affected_rows($result)) {
             throw new Exception("Failed to delete an invitation.", file_api_core::ERROR_CODE);
         }
 
         // Update Manticore 'access' array
         $req = $this->get_request();
         $res = $req->editor_delete($session_id, $user);
 
         if (!$res) {
             throw new Exception("Failed to remove an invitation.", file_api_core::ERROR_CODE);
         }
     }
 
     /**
      * Update an invitation status
      *
      * @param string $session_id Session identifier
      * @param string $user       User identifier
      * @param string $status     Invitation status (accepted, declined)
      *
      * @throws Exception
      */
     public function invitation_update($session_id, $user, $status)
     {
         if ($status != self::STATUS_ACCEPTED && $status != self::STATUS_DECLINED) {
             throw new Exception("Invalid invitation status.", file_api_core::ERROR_CODE);
         }
 
         // get session information
         $session = $this->session_info($session_id);
 
         if (empty($session)) {
             throw new Exception("Document session not found.", file_api_core::ERROR_CODE);
         }
 
         // check session ownership
         if ($user != $_SESSION['user'] && $session['owner'] != $_SESSION['user']) {
             throw new Exception("No permission to update an invitation.", file_api_core::ERROR_CODE);
         }
 
         $db     = $this->rc->get_dbh();
         $result = $db->query("UPDATE `{$this->invitations_table}`"
             . " SET `status` = ?, `changed` = " . $db->now()
             . " WHERE `session_id` = ? AND `user` = ?",
             $status, $session_id, $user);
 
         if (!$db->affected_rows($result)) {
             throw new Exception("Failed to update an invitation status.", file_api_core::ERROR_CODE);
         }
 
         // Update Manticore 'access' array if an owner accepted an invitation request
         if ($status == self::STATUS_ACCEPTED && $_SESSION['user'] == $session['owner']) {
             // @todo
         }
     }
 
     /**
      * Parse session info data
      */
     protected function session_info_parse($record, $path = null, $filter = array())
     {
 /*
         if (is_string($data) && !empty($data)) {
             $data = json_decode($data, true);
         }
 */
         $session = array();
         $fields  = array('id', 'uri', 'owner');
 
         foreach ($fields as $field) {
             if (isset($record[$field])) {
                 $session[$field] = $record[$field];
             }
         }
 
         if ($path) {
             $session['file'] = $path;
         }
 
         // @TODO: is_invited?, last_modified?
 
         if ($session['owner'] == $_SESSION['user']) {
             $session['is_owner'] = true;
         }
 
         if (!empty($filter)) {
             $session = array_intersect_key($session, array_flip($filter));
         }
 
         return $session;
     }
 
     /**
      * Generate URI of Manticore editing session
      */
     protected function frame_uri($id)
     {
         $base_url = rtrim($this->rc->config->get('fileapi_manticore'), ' /');
 
         return $base_url . '/document/' . $id . '/' . $_SESSION['manticore_token'];
     }
 
     /**
      * Get file path from the URI
      */
     protected function uri2path($uri)
     {
         $backend = $this->api->get_backend();
 
         try {
             return $backend->uri2path($uri);
         }
         catch (Exception $e) {
                 // do nothing
         }
 
         foreach ($this->api->get_drivers(true) as $driver) {
             try {
                 $path  = $driver->uri2path($uri);
                 $title = $driver->title();
 
                 if ($title) {
                     $path = $title . file_storage::SEPARATOR . $path;
                 }
 
                 return $path;
             }
             catch (Exception $e) {
                 // do nothing
             }
         }
     }
 
     /**
      * Return Manticore user/session info
      */
     public function user_info()
     {
         $req = $this->get_request();
         $res = $req->get('api/users/me');
 
         return $res->get();
     }
 
     /**
      * Initialize Manticore API request handler
      */
     protected function get_request()
     {
         if (!$this->request) {
             $uri = rcube_utils::resolve_url($this->rc->config->get('fileapi_manticore'));
             $this->request = new file_manticore_api($uri);
 
             // Use stored session token, check if it's still valid
             if ($_SESSION['manticore_token']) {
                 $is_valid = $this->request->set_session_token($_SESSION['manticore_token'], true);
 
                 if ($is_valid) {
                     return $this->request;
                 }
             }
 
             $backend = $this->api->get_backend();
             $auth    = $backend->auth_info();
 
             $_SESSION['manticore_token'] = $this->request->login($auth['username'], $auth['password']);
 
             if (empty($_SESSION['manticore_token'])) {
                 throw new Exception("Unable to login to Manticore server.", file_api_core::ERROR_CODE);
             }
         }
 
         return $this->request;
     }
 }
diff --git a/public_html/js/files_api.js b/public_html/js/files_api.js
index 8c9501a..aa7c0ae 100644
--- a/public_html/js/files_api.js
+++ b/public_html/js/files_api.js
@@ -1,927 +1,993 @@
-/*
+/**
  +--------------------------------------------------------------------------+
  | This file is part of the Kolab File API                                  |
  |                                                                          |
- | Copyright (C) 2012-2013, Kolab Systems AG                                |
+ | Copyright (C) 2012-2015, Kolab Systems AG                                |
  |                                                                          |
  | This program is free software: you can redistribute it and/or modify     |
  | it under the terms of the GNU Affero General Public License as published |
  | by the Free Software Foundation, either version 3 of the License, or     |
  | (at your option) any later version.                                      |
  |                                                                          |
  | 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 |
  | along with this program. If not, see <http://www.gnu.org/licenses/>      |
  +--------------------------------------------------------------------------+
  | Author: Aleksander Machniak <machniak@kolabsys.com>                      |
  +--------------------------------------------------------------------------+
 */
 
 function files_api()
 {
   var ref = this;
 
   // default config
   this.sessions = {};
   this.translations = {};
   this.env = {
     url: 'api/',
     directory_separator: '/',
     resources_dir: 'resources'
   };
 
 
   /*********************************************************/
   /*********          Basic utilities              *********/
   /*********************************************************/
 
   // set environment variable(s)
   this.set_env = function(p, value)
   {
     if (p != null && typeof p === 'object' && !value)
       for (var n in p)
         this.env[n] = p[n];
     else
       this.env[p] = value;
   };
 
   // add a localized label(s) to the client environment
   this.tdef = function(p, value)
   {
     if (typeof p == 'string')
       this.translations[p] = value;
     else if (typeof p == 'object')
       $.extend(this.translations, p);
   };
 
   // return a localized string
   this.t = function(label)
   {
     if (this.translations[label])
       return this.translations[label];
     else
       return label;
   };
 
   // print a message into browser console
   this.log = function(msg)
   {
     if (window.console && console.log)
       console.log(msg);
   };
 
   /********************************************************/
   /*********        Remote request methods        *********/
   /********************************************************/
 
   // send a http POST request to the API service
   this.post = function(action, data, func)
   {
     var url = this.env.url + '?method=' + action;
 
     if (!func) func = 'response';
 
     this.set_request_time();
 
     return $.ajax({
       type: 'POST', url: url, data: JSON.stringify(data), dataType: 'json',
       contentType: 'application/json; charset=utf-8',
-      success: function(response) { ref[func](response); },
+      success: function(response) { if (typeof func == 'function') func(response); else ref[func](response); },
       error: function(o, status, err) { ref.http_error(o, status, err); },
       cache: false,
       beforeSend: function(xmlhttp) { xmlhttp.setRequestHeader('X-Session-Token', ref.env.token); }
     });
   };
 
   // send a http GET request to the API service
   this.get = function(action, data, func)
   {
     var url = this.env.url;
 
     if (!func) func = 'response';
 
     this.set_request_time();
     data.method = action;
 
     return $.ajax({
       type: 'GET', url: url, data: data, dataType: 'json',
-      success: function(response) { ref[func](response); },
+      success: function(response) { if (typeof func == 'function') func(response); else ref[func](response); },
       error: function(o, status, err) { ref.http_error(o, status, err); },
       cache: false,
       beforeSend: function(xmlhttp) { xmlhttp.setRequestHeader('X-Session-Token', ref.env.token); }
     });
   };
 
   // send request with auto-selection of POST/GET method
   this.request = function(action, data, func)
   {
     // Use POST for modification actions with probable big request size
     var method = /_(create|delete|move|copy|update|auth|subscribe|unsubscribe|invite|decline|request|accept|remove)$/.test(action) ? 'post' : 'get';
     return this[method](action, data, func);
   };
 
   // handle HTTP request errors
   this.http_error = function(request, status, err)
   {
     var errmsg = request.statusText;
 
     this.set_busy(false);
     request.abort();
 
     if (request.status && errmsg)
       this.display_message(this.t('servererror') + ' (' + errmsg + ')', 'error');
   };
 
   this.response = function(response)
   {
     this.update_request_time();
     this.set_busy(false);
 
     return this.response_parse(response);
   };
 
   this.response_parse = function(response)
   {
     if (!response || response.status != 'OK') {
       // Logout on invalid-session error
       if (response && response.code == 403)
         this.logout(response);
       else
         this.display_message(response && response.reason ? response.reason : this.t('servererror'), 'error');
 
       return false;
     }
 
     return true;
   };
 
 
   /*********************************************************/
   /*********             Utilities                 *********/
   /*********************************************************/
 
   // Called on "session expired" session
   this.logout = function(response) {};
 
   // set state
   this.set_busy = function(state, message) {};
 
   // displays error message
   this.display_message = function(label, type) {};
 
   // called when a request timed out
   this.request_timed_out = function() {};
 
   // called on start of the request
   this.set_request_time = function() {};
 
   // called on request response
   this.update_request_time = function() {};
 
 
   /*********************************************************/
   /*********             Helpers                   *********/
   /*********************************************************/
 
   // compose a valid url with the given parameters
   this.url = function(action, query)
   {
     var k, param = {},
       querystring = typeof query === 'string' ? '&' + query : '';
 
     if (typeof action !== 'string')
       query = action;
     else if (!query || typeof query !== 'object')
       query = {};
 
     // overwrite task name
     if (action)
       query.method = action;
 
     // remove undefined values
     for (k in query) {
       if (query[k] !== undefined && query[k] !== null)
         param[k] = query[k];
     }
 
     return '?' + $.param(param) + querystring;
   };
 
   // fill folder selector with options
   this.folder_select_element = function(select, params)
   {
     var options = [],
       selected = params && params.selected ? params.selected : this.env.folder;
 
     if (params && params.empty)
       options.push($('<option>').val('').text('---'));
 
     $.each(this.env.folders, function(i, f) {
       var n, name = escapeHTML(f.name);
 
       // skip read-only folders
       if (params && params.writable && (f.readonly || f.virtual)) {
         var folder, found = false, prefix = i + ref.env.directory_separator;
 
         // for virtual folders check if there's any writable subfolder
         for (n in ref.env.folders) {
           if (n.indexOf(prefix) === 0) {
             folder = ref.env.folders[n];
             if (!folder.virtual && !folder.readonly) {
               found = true;
               break;
             }
           }
         }
 
         if (!found)
           return;
       }
 
       for (n=0; n<f.depth; n++)
         name = '&nbsp;&nbsp;&nbsp;' + name;
 
       options.push($('<option>').val(i).html(name));
     });
 
     select.empty().append(options);
 
     if (selected)
       select.val(selected);
   };
 
   // Folder list parser, converts it into structure
   this.folder_list_parse = function(list, num, subscribed)
   {
     var i, n, j, items, items_len, f, tmp, folder, readonly,
       subs_support, subs_prefixes = {}, found,
       separator = this.env.directory_separator,
       len = list ? list.length : 0, folders = {};
 
     if (!num) num = 1;
 
     if (subscribed === undefined)
       subscribed = true;
 
     // prepare subscriptions support detection
     if (len && this.env.caps) {
       subs_support = !!this.env.caps.SUBSCRIPTIONS;
       $.each(this.env.caps.MOUNTPOINTS || [], function(i, v) {
         subs_prefixes[i] = !!v.SUBSCRIPTIONS;
       });
     }
 
     for (i=0; i<len; i++) {
       folder = list[i];
       readonly = false;
 
       // in extended format folder is an object
       if (typeof folder !== 'string') {
         readonly = folder.readonly;
         folder = folder.folder;
       }
 
       items = folder.split(separator);
       items_len = items.length;
 
       for (n=0; n<items_len-1; n++) {
         tmp = items.slice(0, n+1);
         f = tmp.join(separator);
         if (!folders[f])
           folders[f] = {name: tmp.pop(), depth: n, id: 'f'+num++, virtual: 1};
       }
 
       folders[folder] = {
         name: items.pop(),
         depth: items_len-1,
         id: 'f' + num++,
         readonly: readonly
       };
 
       // set subscription flag, leave undefined if the source does not support subscriptions
       found = false;
       for (j in subs_prefixes) {
         if (folder === j) {
           // this is a mount point
           found = true;
           break;
         }
         if (folder.indexOf(j + separator) === 0) {
           if (subs_prefixes[j])
             folders[folder].subscribed = subscribed;
           found = true;
           break;
         }
       }
 
       if (!found && subs_support)
         folders[folder].subscribed = subscribed;
     }
 
     return folders;
   };
 
   // folder structure presentation (structure icons)
   this.folder_list_tree = function(folders)
   {
     var i, n, diff, tree = [], folder;
 
     for (i in folders) {
       items = i.split(this.env.directory_separator);
       items_len = items.length;
 
       // skip root
       if (items_len < 2) {
         tree = [];
         continue;
       }
 
       folders[i].tree = [1];
 
       for (n=0; n<tree.length; n++) {
         folder = tree[n];
         diff = folders[folder].depth - (items_len - 1);
         if (diff >= 0)
           folders[folder].tree[diff] = folders[folder].tree[diff] ? folders[folder].tree[diff] + 2 : 2;
       }
 
       tree.push(i);
     }
 
     for (i in folders) {
       if (tree = folders[i].tree) {
         var html = '', divs = [];
         for (n=0; n<folders[i].depth; n++) {
           if (tree[n] > 2)
             divs.push({'class': 'l3', width: 15});
           else if (tree[n] > 1)
             divs.push({'class': 'l2', width: 15});
           else if (tree[n] > 0)
             divs.push({'class': 'l1', width: 15});
           // separator
           else if (divs.length && !divs[divs.length-1]['class'])
             divs[divs.length-1].width += 15;
           else
             divs.push({'class': null, width: 15});
         }
 
         for (n=divs.length-1; n>=0; n--) {
           if (divs[n]['class'])
             html += '<span class="tree '+divs[n]['class']+'" />';
           else
             html += '<span style="width:'+divs[n].width+'px" />';
         }
 
         if (html)
           $('#' + folders[i].id + ' span.branch').html(html);
       }
     }
   };
 
   // Get editing sessions on the specified file
   this.file_sessions = function(file)
   {
     var sessions = [], folder = this.file_path(file);
 
     $.each(this.sessions[folder] || {}, function(session_id, session) {
       if (session.file == file) {
         session.id = session_id;
         sessions.push(session);
       }
     });
 
     return sessions;
   };
 
   // convert content-type string into class name
   this.file_type_class = function(type)
   {
     if (!type)
       return '';
 
     type = type.replace(/[^a-z0-9]/g, '_');
 
     return type;
   };
 
   // convert bytes into number with size unit
   this.file_size = function(size)
   {
     if (size >= 1073741824)
       return parseFloat(size/1073741824).toFixed(2) + ' GB';
     if (size >= 1048576)
       return parseFloat(size/1048576).toFixed(2) + ' MB';
     if (size >= 1024)
       return parseInt(size/1024) + ' kB';
 
     return parseInt(size || 0) + ' B';
   };
 
   // Extract file name from full path
   this.file_name = function(path)
   {
     var path = path.split(this.env.directory_separator);
     return path.pop();
   };
 
   // Extract file path from full path
   this.file_path = function(path)
   {
     var path = path.split(this.env.directory_separator);
     path.pop();
     return path.join(this.env.directory_separator);
   };
 
   // compare two sortable objects
   this.sort_compare = function(data1, data2)
   {
     var key = this.env.sort_col || 'name';
 
     if (key == 'mtime')
       key = 'modified';
 
     data1 = data1[key];
     data2 = data2[key];
 
     if (key == 'size' || key == 'modified')
       // numeric comparison
       return this.env.sort_reverse ? data2 - data1 : data1 - data2;
     else {
       // use Array.sort() for string comparison
       var arr = [data1, data2];
       arr.sort(function (a, b) {
         // @TODO: use localeCompare() arguments for better results
         return a.localeCompare(b);
       });
 
       if (this.env.sort_reverse)
         arr.reverse();
 
       return arr[0] === data2 ? 1 : -1;
     }
   };
 
   // Checks if specified mimetype is supported natively by the browser (return 1)
   // or can be displayed in the browser using File API viewer (return 2)
   // or using Manticore - WebODF collaborative editor (return 4)
   this.file_type_supported = function(type, capabilities)
   {
     var i, t, res = 0, regexps = [], img = 'jpg|jpeg|gif|bmp|png',
       caps = this.env.browser_capabilities || {},
       doc = /^application\/vnd.oasis.opendocument.(text)$/i;
 
     // Manticore?
     if (capabilities && capabilities.MANTICORE && doc.test(type))
       res |= 4;
 
     if (caps.tif)
       img += '|tiff';
 
     if ((new RegExp('^image/(' + img + ')$', 'i')).test(type))
       res |= 1;
 
     // prefer text viewer for any text type
     if (/^text\/(?!(pdf|x-pdf))/i.test(type))
       res |= 2;
 
     if (caps.pdf) {
       regexps.push(/^application\/(pdf|x-pdf|acrobat|vnd.pdf)/i);
       regexps.push(/^text\/(pdf|x-pdf)/i);
     }
 
     if (caps.flash)
       regexps.push(/^application\/x-shockwave-flash/i);
 
     for (i in regexps)
       if (regexps[i].test(type))
         res |= 1;
 
     for (i in navigator.mimeTypes) {
       t = navigator.mimeTypes[i].type;
       if (t == type && navigator.mimeTypes[i].enabledPlugin)
         res |= 1;
     }
 
     // types with viewer support
     if ($.inArray(type, this.env.supported_mimetypes) > -1)
       res |= 2;
 
     return res;
   };
 
   // Return browser capabilities
   this.browser_capabilities = function()
   {
     var i, caps = [], ctypes = ['pdf', 'flash', 'tif'];
 
     for (i in ctypes)
       if (this.env.browser_capabilities[ctypes[i]])
         caps.push(ctypes[i]);
 
     return caps;
   };
 
   // Checks browser capabilities eg. PDF support, TIF support
   this.browser_capabilities_check = function()
   {
     if (!this.env.browser_capabilities)
       this.env.browser_capabilities = {};
 
     if (this.env.browser_capabilities.pdf === undefined)
       this.env.browser_capabilities.pdf = this.pdf_support_check();
 
     if (this.env.browser_capabilities.flash === undefined)
       this.env.browser_capabilities.flash = this.flash_support_check();
 
     if (this.env.browser_capabilities.tif === undefined)
       this.tif_support_check();
   };
 
   this.tif_support_check = function()
   {
     var img = new Image(), ref = this;
 
     img.onload = function() { ref.env.browser_capabilities.tif = 1; };
     img.onerror = function() { ref.env.browser_capabilities.tif = 0; };
     img.src = this.env.resources_dir + '/blank.tif';
   };
 
   this.pdf_support_check = function()
   {
     var plugin = navigator.mimeTypes ? navigator.mimeTypes["application/pdf"] : {},
       plugins = navigator.plugins,
       len = plugins.length,
       regex = /Adobe Reader|PDF|Acrobat/i,
       ref = this;
 
     if (plugin && plugin.enabledPlugin)
         return 1;
 
     if (window.ActiveXObject) {
       try {
         if (axObj = new ActiveXObject("AcroPDF.PDF"))
           return 1;
       }
       catch (e) {}
       try {
         if (axObj = new ActiveXObject("PDF.PdfCtrl"))
           return 1;
       }
       catch (e) {}
     }
 
     for (i=0; i<len; i++) {
       plugin = plugins[i];
       if (typeof plugin === 'String') {
         if (regex.test(plugin))
           return 1;
       }
       else if (plugin.name && regex.test(plugin.name))
         return 1;
     }
 
     return 0;
   };
 
   this.flash_support_check = function()
   {
     var plugin = navigator.mimeTypes ? navigator.mimeTypes["application/x-shockwave-flash"] : {};
 
     if (plugin && plugin.enabledPlugin)
         return 1;
 
     if (window.ActiveXObject) {
       try {
         if (axObj = new ActiveXObject("ShockwaveFlash.ShockwaveFlash"))
           return 1;
       }
       catch (e) {}
     }
 
     return 0;
   };
 
   // converts number of seconds into HH:MM:SS format
   this.time_format = function(s)
   {
     s = parseInt(s);
 
     if (s >= 60*60*24)
       return '-';
 
     return (new Date(1970, 1, 1, 0, 0, s, 0)).toTimeString().replace(/.*(\d{2}:\d{2}:\d{2}).*/, '$1');
   };
 
   // same as str.split(delimiter) but it ignores delimiters within quoted strings
   this.explode_quoted_string = function(str, delimiter)
   {
     var result = [],
       strlen = str.length,
       q, p, i, chr, last;
 
     for (q = p = i = 0; i < strlen; i++) {
       chr = str.charAt(i);
       if (chr == '"' && last != '\\') {
         q = !q;
       }
       else if (!q && chr == delimiter) {
         result.push(str.substring(p, i));
         p = i + 1;
       }
       last = chr;
     }
 
     result.push(str.substr(p));
     return result;
   };
 };
 
 /**
  * Class implementing Manticore Client API
  *
  * Configuration:
  *    iframe - manticore iframe element
  *    title_input - document title element
  *    export_menu - export formats list
  *    members_list - collaborators list
  *    photo_url - <img> src for a collaborator
  *    photo_default_url - default image of a collaborator
- *    set_busy, display_message, hide_message, gettext - methods
+ *
+ *    set_busy, display_message, hide_message, gettext - common methods
+ *
+ *    api - Chwala files_api instance
+ *    interval - how often to check for invitations in seconds (default: 60)
+ *    owner - user identifier
+ *    invitationMore - add "more" link into invitation notices
  */
 function manticore_api(conf)
 {
-  var domain,
+  var domain, manticore,
     locks = {},
     callbacks = {},
     members = {},
-    self = this,
-    manticore = conf.iframe.contentWindow;
-
-  if (/^(https?:\/\/[^/]+)/i.test(conf.iframe.src))
-    domain = RegExp.$1;
-
-  // Register 'message' event to receive messages from Manticore iframe
-  window.addEventListener('message', function(event) {
-    if (event.source == manticore && event.origin == domain) {
-      self.message_handler(event.data);
-    }
-  });
-
-  // Bind for document title changes
-  if (conf.title_input)
-    $(conf.title_input).change(function() { self.set_title($(this).val()); });
+    self = this;
 
   // Sets state
   this.set_busy = function(state, message)
   {
     if (conf.set_busy)
       return conf.set_busy(state, message);
   };
 
   // Displays error/notification message
-  this.display_message = function(label, type)
+  this.display_message = function(label, type, is_txt)
   {
     if (conf.display_message)
-      return conf.display_message(label, type);
+      return conf.display_message(label, type, is_txt, 10);
 
     if (type == 'error')
-      alert(this.gettext(label));
+      alert(is_txt ? label : this.gettext(label));
   };
 
   // Hides the error/notification message
   this.hide_message = function(id)
   {
     if (conf.hide_message)
       return conf.hide_message(id);
   };
 
   // Localization method
   this.gettext = function(label)
   {
     if (conf.gettext)
       return conf.gettext(label);
 
     return label;
   };
 
-  // Display loading message
-  this.init_lock = this.set_busy(true, 'loading');
-
   // Handle messages from Manticore
   this.message_handler = function(data)
   {
     var result;
 
     console.log(data);
 
     if (callbacks[data.id])
       result = callbacks[data.id](data);
     if (result !== false && data.name && conf[data.name])
       result = conf[data.name](data);
 
     delete callbacks[data.id];
 
     if (locks[data.id]) {
       this.set_busy(false);
       this.hide_message(data.id);
       delete locks[data.id];
     }
 
     if (result === false)
       return;
 
     switch (data.name) {
       case 'ready':
         this.ready();
         break;
 
       case 'titleChanged':
         if (conf.title_input)
           $(conf.title_input).val(data.value);
         break;
 
       case 'memberAdded':
         // @TODO: display notification?
         if (conf.members_list)
           $(conf.members_list).append(this.member_item(data));
         break;
 
       case 'memberRemoved':
         // @TODO: display notification?
         if (conf.members_list) {
           $('#' + members[data.memberId].id, conf.members_list).remove();
           delete members[data.memberId];
         }
         break;
     }
   };
 
   this.post = function(action, data, callback, lock_label)
   {
     if (!data) data = {};
 
     if (lock_label) {
       data.id = this.set_busy(true, this.gettext(lock_label));
       locks[data.id] = true;
     }
 
     if (!data.id)
       data.id = (new Date).getTime();
 
     // make sure the id is not in use
     while (callbacks[data.id])
       data.id++;
 
     data.name = action;
 
     callbacks[data.id] = callback;
 
     console.log(data);
 
     manticore.postMessage(data, domain);
   };
 
   this.ready = function()
   {
     if (this.init_lock) {
       this.set_busy(false);
       this.hide_message(this.init_lock);
       delete this.init_lock;
     }
 
     if (conf.export_menu)
       this.export_menu(conf.export_menu);
 
     if (conf.members_list)
       this.get_members(function(data) {
         var images = [], id = (new Date).getTime();
         $.each(data.value || [], function() {
           images.push(self.member_item(this, id++));
         });
         $(conf.members_list).html('').append(images);
       });
 
     if (conf.title_input)
       this.get_title(function(data) {
         $(conf.title_input).val(data.value);
       });
   };
 
   // Save current document
   this.save = function(callback)
   {
     this.post('actionSave', {}, callback, 'saving');
   };
 
   // Export/download current document
   this.export = function(type, callback)
   {
     this.post('actionExport', {value: type}, callback);
   };
 
   // Get supported export formats and create content of menu element
   this.export_menu = function(menu)
   {
     this.post('getExportFormats', {}, function(data) {
       var items = [];
 
       $.each(data.value || [], function(i, v) {
         items.push($('<li>').attr({role: 'menuitem'}).append(
           $('<a>').attr({href: '#', role: 'button', tabindex: 0, 'aria-disabled': false, 'class': 'active'})
             .text(v.label).click(function() { self.export(v.format); })
         ));
       });
 
       $(menu).html('').append(items);
     });
   };
 
   // Get document title
   this.get_title = function(callback)
   {
     this.post('getTitle', {}, callback);
   };
 
   // Set document title
   this.set_title = function(title, callback)
   {
     this.post('setTitle', {value: title}, callback);
   };
 
   // Get document session members
   this.get_members = function(callback)
   {
     this.post('getMembers', {}, callback);
   };
 
   // Creates session member image element
   this.member_item = function(member, id)
   {
     member.id = 'member' + (id || (new Date).getTime());
     member.name = member.fullName + ' (' + member.email + ')';
 
     members[member.memberId] = member;
 
     var img = $('<img>').attr({title: member.name, id: member.id, 'class': 'photo', src: conf.photo_default_url})
         .css({'border-color': member.color})
         .text(name);
 
     if (conf.photo_url) {
       img.attr('src', conf.photo_url.replace(/%email/, urlencode(member.email)));
       if (conf.photo_default_url)
         img.error(function() { this.src = conf.photo_default_url; });
     }
 
     return img;
   };
+
+  // track changes in invitations
+  this.track_invitations = function()
+  {
+    conf.api.request('invitations', {timestamp: this.invitations_timestamp || -1}, this.parse_invitations);
+    this.invitations_timeout = setTimeout(function() { self.track_invitations(); }, (conf.interval || 60) * 1000);
+  };
+
+  // parse 'invitations' response
+  this.parse_invitations = function(response)
+  {
+    if (!conf.api.response(response) || !response.result)
+      return;
+
+    var invitation_change = function(invitation, suffix) {
+      var msg = self.gettext(invitation.status + 'notice' + (suffix || ''));
+
+      msg = msg.replace('$user', invitation.user).replace('$file', invitation.filename);
+
+      if (conf.invitationMore)
+        msg = $('<div>').append($('<span>').text(msg))
+          .append($('<a>').text(self.gettext('more')).attr('id', invitation.id)).html();
+
+      self.display_message(msg, 'notice', true);
+
+      if (conf.invitationChange)
+        conf.invitationChange(invitation);
+    }
+
+    $.each(response.result.list || [], function(i, invitation) {
+      invitation.id = 'i' + (response.result.timestamp + i);
+      invitation.is_session_owner = invitation.user == conf.owner;
+
+      // display notifications
+      if (invitation.is_session_owner) {
+        // @todo: add Accept, Decline buttons for 'invited' invitations
+        if (invitation.status == 'invited' || invitation.status == 'declined') {
+          invitation_change(invitation);
+        }
+      }
+      else {
+        // @todo: add Accept, Decline buttons for 'requested' invitations
+        if (invitation.status == 'accepted' || invitation.status == 'declined' || invitation.status == 'requested') {
+          invitation_change(invitation, 'owner');
+        }
+      }
+    });
+
+    self.invitations_timestamp = response.result.timestamp;
+  };
+
+  if (!conf)
+    conf = {};
+
+  // Got Manticore iframe, use Client API
+  if (conf.iframe) {
+    manticore = conf.iframe.contentWindow;
+
+    if (/^(https?:\/\/[^/]+)/i.test(conf.iframe.src))
+      domain = RegExp.$1;
+
+    // Register 'message' event to receive messages from Manticore iframe
+    window.addEventListener('message', function(event) {
+      if (event.source == manticore && event.origin == domain) {
+        self.message_handler(event.data);
+      }
+    });
+
+    // Bind for document title changes
+    if (conf.title_input)
+      $(conf.title_input).change(function() { self.set_title($(this).val()); });
+
+    // Display loading message
+    this.init_lock = this.set_busy(true, 'loading');
+  }
+
+  if (conf.api)
+    this.track_invitations();
 };
 
 // Add escape() method to RegExp object
 // http://dev.rubyonrails.org/changeset/7271
 RegExp.escape = function(str)
 {
   return String(str).replace(/([.*+?^=!:${}()|[\]\/\\])/g, '\\$1');
 };
 
 // define String's startsWith() method for old browsers
 if (!String.prototype.startsWith) {
   String.prototype.startsWith = function(search, position) {
     position = position || 0;
     return this.slice(position, search.length) === search;
   };
 };
 
 // make a string URL safe (and compatible with PHP's rawurlencode())
 function urlencode(str)
 {
   if (window.encodeURIComponent)
     return encodeURIComponent(str).replace('*', '%2A');
 
   return escape(str)
     .replace('+', '%2B')
     .replace('*', '%2A')
     .replace('/', '%2F')
     .replace('@', '%40');
 };
 
 function escapeHTML(str)
 {
   return str === undefined ? '' : String(str)
     .replace(/&/g, '&amp;')
     .replace(/>/g, '&gt;')
     .replace(/</g, '&lt;');
 };
 
 function object_is_empty(obj)
 {
   if (obj)
     for (var i in obj)
       if (i !== null)
         return true;
 
   return false;
 }