option refactoring

Game

  def click(x: Int, y: Int) {
    val mx = screen.calculateTileIndex(screen.sx+x)
    val my = screen.calculateTileIndex(screen.sy+y)
    val tile = map.tiles(mx,my)
    
    performPossibleUnitAction(tile.unit, mx, my)
  }
  
  private def performPossibleUnitAction(tileUnit:Option[Unit], mx: Int,  my: Int) {
    (tileUnit, selectedUnit) match {
      case (None, Some(unit)) => {
        unit.moveTo(mx, my)
      }
      case (Some(newSelectedUnit), Some(oldSelectedUnit)) => {
        newSelectedUnit.select()
        oldSelectedUnit.unselect()
      }
      case (Some(unit), None) => {
        selectedUnit = Option(unit)
        unit.select()
      }
      case (None, None) => //do nothing
    }
  }