/**
  * @throws \Exception
  * @return CommandResponse
  */
 public function execute()
 {
     $songIndex = $this->_playlist->tracks()->count() + 1;
     $this->_playlist->tracks()->attach($this->_track, ['position' => $songIndex]);
     Playlist::whereId($this->_playlist->id)->update(['track_count' => DB::raw('(SELECT COUNT(id) FROM playlist_track WHERE playlist_id = ' . $this->_playlist->id . ')')]);
     return CommandResponse::succeed(['message' => 'Track added!']);
 }