structure AppUpdate =
struct
  open AppType

  local
    fun helpGetTrianglesVector (lst, acc) =
      case lst of
        {x1, y1, x2, y2, x3, y3} :: tl =>
          let val vec = Vector.fromList [x1, y1, x2, y2, x3, y3]
          in helpGetTrianglesVector (tl, vec :: acc)
          end
      | [] => acc
  in
    fun getTrianglesVector (app: app_type) =
      let val lst = helpGetTrianglesVector (#triangles app, [])
      in Vector.concat lst
      end
  end

  fun genClickPoints (windowWidth, windowHeight) =
    let
      val w = Real32.fromInt windowWidth / 40.0
      val h = Real32.fromInt windowHeight / 40.0
    in
      Vector.tabulate (41, fn idx => Real32.fromInt idx * w)
    end

  local
    val clickPoints = genClickPoints (500, 500)

    fun getVerticalClickPos (idx, horizontalPos, mouseX, mouseY, r, g, b) =
      if idx = Vector.length clickPoints then
        #[]
      else
        let
          val curVerticalPos = Vector.sub (clickPoints, idx)
        in
          if mouseY < curVerticalPos - 7.0 orelse mouseY > curVerticalPos + 7.0 then
            getVerticalClickPos
              (idx + 1, horizontalPos, mouseX, mouseY, r, g, b)
          else
            let
              val hpos = horizontalPos - 250.0
              val vpos = ~(curVerticalPos - 250.0)
              val left = (hpos - 5.0) / 250.0
              val right = (hpos + 5.0) / 250.0
              val bottom = (vpos - 5.0) / 250.0
              val top = (vpos + 5.0) / 250.0
            in
              #[ left, bottom, r, g, b
               , right, bottom, r, g, b
               , left, top, r, g, b

               , left, top, r, g, b
               , right, bottom, r, g, b
               , right, top, r, g, b
               ]
            end
        end

    fun getHorizontalClickPos (idx, mouseX, mouseY, r, g, b) =
      if idx = Vector.length clickPoints then
        #[]
      else
        let
          val curPos = Vector.sub (clickPoints, idx)
        in
          if mouseX < curPos - 7.0 orelse mouseX > curPos + 7.0 then
            getHorizontalClickPos (idx + 1, mouseX, mouseY, r, g, b)
          else
            getVerticalClickPos (0, curPos, mouseX, mouseY, r, g, b)
        end
  in
    (*
     * This function returns a vector containing the position data of the
     * clicked square.
     * If a square wasn't found at the clicked position, 
     * an empty vector is returned.
     *)
    fun getClickPos (mouseX, mouseY, r, g, b) =
      getHorizontalClickPos
        (0, Real32.fromInt mouseX, Real32.fromInt mouseY, r, g, b)
  end

  fun update (model, mouseX, mouseY, inputMsg) =
    let
      open DrawMessage
      open InputMessage
    in
      case inputMsg of
        MOUSE_MOVE {x = mouseX, y = mouseY} =>
          let
            val _ = print "mouse moved\n"
            val drawMsg = DRAW_BUTTON (getClickPos
              (mouseX, mouseY, 1.0, 0.0, 0.0))
          in
            (model, drawMsg, mouseX, mouseY)
          end
      | MOUSE_LEFT_RELEASE =>
          let
            val _ = print "mouse released\n"
            val drawMsg = DRAW_BUTTON (getClickPos
              (mouseX, mouseY, 1.0, 0.0, 0.0))
          in
            (model, drawMsg, mouseX, mouseY)
          end
      | MUSE_LEFT_CLICK =>
          let
            val _ = print "mouse clicked\n"
            val buttonVec = getClickPos (mouseX, mouseY, 0.0, 0.0, 1.0)
            val drawMsg = DRAW_BUTTON buttonVec
          in
            (model, drawMsg, mouseX, mouseY)
          end
    end
end