protected function idToUri($ids, $type)
    {
        $type = 'spotify:' . $type . ':';

        $ids = array_map(function ($id) use ($type) {
            if (substr($id, 0, strlen($type)) != $type) {
                $id = $type . $id;
            }

            return $id;
        }, (array) $ids);

        return (count($ids) == 1) ? $ids[0] : $ids;
    }