// first element = url
  // second element = parent
  def formatURL(element: Tuple2[String, String]): String = {
     val parts = element._1.split('/').foldLeft(element._2.split('/')) {
       case (cur, dir) =>
         if (dir == ".") cur // stay in current directory
         else if (dir == "..") cur.dropRight(1) // go up in the tree
         else cur :+ dir // cd into directory
   }

    return parts.mkString("/") // build the string back
  }