structure CommonUpdate =
struct
  open AppType

  open DrawMessage
  open FileMessage
  open InputMessage
  open UpdateMessage

  fun getSaveSquaresMsg (model: app_type) =
    let
      val {canvasWidth, canvasHeight, squares, ...} = model
      val str = CollisionTree.toSaveString (squares, canvasWidth, canvasHeight)
      val msg = SAVE_SQUARES str
    in
      (model, [FILE msg])
    end

  fun getLoadSquaresMsg model =
    (model, [FILE LOAD_SQUARES])

  fun getExportSquaresMsg (model: app_type) =
    let
      val {squares, canvasWidth, canvasHeight, ...} = model
      val exportString =
        CollisionTree.toExportString (squares, canvasWidth, canvasHeight)
      val msg = EXPORT_SQUARES exportString
    in
      (model, [FILE msg])
    end

  (* unimplemented *)
  fun useSquaresInNormalMode (model, squares) = (model, [])

  fun squaresLoadError model = (model, [])
end