public function talk(string $id_chat, string $message): ?int
  {
    if ( $this->check() && ($chat = $this->info($id_chat)) && !$chat['blocked'] ){
      $users = $this->get_participants($id_chat);
      if ( \in_array($this->user->get_id(), $users, true) ){
        $time = microtime(true);
        $st = bbn\util\enc::crypt(json_encode(['time' => $time, 'user' => $this->user->get_id(), 'message' => $message]));
        $day = date('Y-m-d');
        foreach ( $users as $user ){
          $dir = BBN_DATA_PATH.'users/'.$user.'/chat/'.$id_chat.'/'.$day;
          if ( bbn\file\dir::create_path($dir) ){
            file_put_contents($dir.'/'.$time.'.msg', $st);
          }
        }
        return $this->db->update('bbn_chats', ['last_message' => $time], ['id' => $id_chat]);
      }
    }
    return null;
  }