diff --git a/lib/file_manticore.php b/lib/file_manticore.php
index 61295cc..e91f13d 100644
--- a/lib/file_manticore.php
+++ b/lib/file_manticore.php
@@ -1,668 +1,670 @@
 <?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 $user;
     protected $sessions_table    = 'chwala_sessions';
     protected $invitations_table = 'chwala_invitations';
     protected $icache            = array();
 
     const STATUS_INVITED   = 'invited';
     const STATUS_REQUESTED = 'requested';
     const STATUS_ACCEPTED  = 'accepted';
     const STATUS_DECLINED  = 'declined';
     const STATUS_DECLINED_OWNER = 'declined-owner'; // same as 'declined' but done by the session owner
     const STATUS_ACCEPTED_OWNER = 'accepted-owner'; // same as 'accepted' but done by the session owner
 
 
     /**
      * Class constructor
      *
      * @param file_api Chwala API app instance
      */
     public function __construct($api)
     {
         $this->rc   = rcube::get_instance();
         $this->api  = $api;
         $this->user = $_SESSION['user'];
 
         $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'] != $this->user) {
                 // check if the user was invited
                 $invitations = $this->invitations_find(array('session_id' => $session_id, 'user' => $this->user));
                 $states      = array(self::STATUS_INVITED, self::STATUS_ACCEPTED, self::STATUS_ACCEPTED_OWNER);
 
                 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, $this->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      = $this->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)
     {
         $session = $this->icache["session:$id"];
 
         if (!$session) {
             $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);
 
                 $this->icache["session:$id"] = $session;
             }
         }
 
         if ($session) {
             if ($session['owner'] == $this->user) {
                 $session['is_owner'] = true;
             }
 
             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_find(array('user' => $this->user));
             $states      = array(self::STATUS_INVITED, self::STATUS_ACCEPTED, self::STATUS_ACCEPTED_OWNER);
 
             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, $this->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)
     {
         // get user name
         $owner_name = $this->api->resolve_user($owner) ?: '';
 
         // 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`, `owner_name`, `data`)"
             . " VALUES (?, ?, ?, ?, ?)",
             $id, $uri, $owner, $owner_name, json_encode($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. This will return all
      * invitations related to the user including his sessions.
      *
      * @param array $filter Search filter (see self::invitations_find())
      *
      * @return array Invitations list
      */
     public function invitations_list($filter = array())
     {
         $filter['user'] = $this->user;
 
         // list of invitations to the user or requested by him
         $result = $this->invitations_find($filter, true);
 
         unset($filter['user']);
         $filter['owner'] = $this->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 $result;
     }
 
     /**
      * 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, $extended = false)
     {
         $db     = $this->rc->get_dbh();
         $query  = '';
         $select = "i.*";
 
         foreach ($filter as $column => $value) {
             if ($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);
             }
         }
 
         if ($extended) {
             $select .= ", s.`uri`, s.`owner`, s.`owner_name`";
             $join[]  = "`{$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 (use null for current user)
      * @param string $status     Invitation status (invited, requested)
      * @param string $comment    Invitation description/comment
      * @param string &$user_name Optional user name
      *
      * @throws Exception
      */
     public function invitation_create($session_id, $user, $status = 'invited', $comment = '', &$user_name = '')
     {
         if (empty($user)) {
             $user = $this->user;
         }
 
         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'] != $this->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);
             }
         }
 
         // get user name
-        $user_name = $this->api->resolve_user($user) ?: '';
+        if (empty($user_name)) {
+            $user_name = $this->api->resolve_user($user) ?: '';
+        }
 
         // insert invitation
         $db     = $this->rc->get_dbh();
         $result = $db->query("INSERT INTO `{$this->invitations_table}`"
             . " (`session_id`, `user`, `user_name`, `status`, `comment`, `changed`)"
             . " VALUES (?, ?, ?, ?, ?, " . $db->now() . ")",
             $session_id, $user, $user_name, $status, $comment ?: '');
 
         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, $this->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 (use null for current user)
      * @param string $status     Invitation status (accepted, declined)
      * @param string $comment    Invitation description/comment
      *
      * @throws Exception
      */
     public function invitation_update($session_id, $user, $status, $comment = '')
     {
         if (empty($user)) {
             $user = $this->user;
         }
 
         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 != $this->user && $session['owner'] != $this->user) {
             throw new Exception("No permission to update an invitation.", file_api_core::ERROR_CODE);
         }
 
         if ($session['owner'] == $this->user) {
             $status = $status . '-owner';
         }
 
         $db     = $this->rc->get_dbh();
         $result = $db->query("UPDATE `{$this->invitations_table}`"
             . " SET `status` = ?, `comment` = ?, `changed` = " . $db->now()
             . " WHERE `session_id` = ? AND `user` = ?",
             $status, $comment ?: '', $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_OWNER) {
             $req = $this->get_request();
             $res = $req->editor_add($session_id, $user, file_manticore_api::ACCESS_WRITE);
 
             if (!$res) {
                 throw new Exception("Failed to update an invitation status.", file_api_core::ERROR_CODE);
             }
         }
     }
 
     /**
      * 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'] == $this->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;
     }
 }