structure AppUpdate =
struct
  open AppType

  open DrawMessage
  open FileMessage
  open InputMessage
  open UpdateMessage

  fun getDotVecFromIndices (model: app_type, hIdx, vIdx) =
    let
      val {windowWidth, windowHeight, xClickPoints, yClickPoints, ...} = model
      val xpos = Vector.sub (xClickPoints, hIdx)
      val ypos = Vector.sub (yClickPoints, vIdx)

      val endXpos =
        if hIdx + 1 = Vector.length xClickPoints then
          xpos
        else
          Vector.sub (xClickPoints, hIdx + 1)

      val endYpos =
        if vIdx + 1 = Vector.length yClickPoints then
          ypos
        else
          Vector.sub (yClickPoints, vIdx + 1)

      val tl =
        ClickPoints.getDrawDotRgb
          (xpos, ypos, 0.0, 0.0, 1.0, windowWidth, windowHeight)
      val tr =
        ClickPoints.getDrawDotRgb
          (endXpos, ypos, 0.0, 0.0, 1.0, windowWidth, windowHeight)
      val bl =
        ClickPoints.getDrawDotRgb
          (xpos, endYpos, 0.0, 0.0, 1.0, windowWidth, windowHeight)
      val br =
        ClickPoints.getDrawDotRgb
          (endXpos, endYpos, 0.0, 0.0, 1.0, windowWidth, windowHeight)
    in
      Vector.concat [tl, tr, bl, br]
    end

  fun mouseMoveOrRelease (model: app_type) =
    let
      val drawVec =
        case ClickPoints.getClickPositionFromMouse model of
          SOME (hIdx, vIdx) => getDotVecFromIndices (model, hIdx, vIdx)
        | NONE => Vector.fromList []

      val drawMsg = DRAW_DOT drawVec
      val drawMsg = [DRAW drawMsg]
    in
      (model, drawMsg)
    end

  fun getDrawDotMsgWhenArrowIsAtBoundary model =
    let
      val {arrowX, arrowY, ...} = model
      val dotVec = getDotVecFromIndices (model, arrowX, arrowY)
      val drawMsg = DRAW_DOT dotVec
      val drawMsg = [DRAW drawMsg]
    in
      (model, drawMsg)
    end

  fun moveArrowUp (model: app_type) =
    let
      val {arrowX, arrowY, ...} = model
    in
      if arrowY > 0 then
        let
          val newArrowY = arrowY - 1
          val model = AppWith.arrowY (model, newArrowY)

          val dotVec = getDotVecFromIndices (model, arrowX, newArrowY)
          val drawMsg = DRAW_DOT dotVec
          val drawMsg = [DRAW drawMsg]
        in
          (model, drawMsg)
        end
      else
        getDrawDotMsgWhenArrowIsAtBoundary model
    end

  fun moveArrowLeft (model: app_type) =
    let
      val {arrowX, arrowY, ...} = model
    in
      if arrowX > 0 then
        let
          val newArrowX = arrowX - 1
          val model = AppWith.arrowX (model, newArrowX)

          val dotVec = getDotVecFromIndices (model, newArrowX, arrowY)
          val drawMsg = DRAW_DOT dotVec
          val drawMsg = [DRAW drawMsg]
        in
          (model, drawMsg)
        end
      else
        getDrawDotMsgWhenArrowIsAtBoundary model
    end

  fun moveArrowRight (model: app_type) =
    let
      val {arrowX, arrowY, xClickPoints, ...} = model
    in
      if arrowX < Vector.length xClickPoints - 2 then
        let
          val newArrowX = arrowX + 1
          val model = AppWith.arrowX (model, newArrowX)

          val dotVec = getDotVecFromIndices (model, newArrowX, arrowY)
          val drawMsg = DRAW_DOT dotVec
          val drawMsg = [DRAW drawMsg]
        in
          (model, drawMsg)
        end
      else
        getDrawDotMsgWhenArrowIsAtBoundary model
    end

  fun moveArrowDown (model: app_type) =
    let
      val {arrowX, arrowY, yClickPoints, ...} = model
    in
      if arrowY < Vector.length yClickPoints - 2 then
        let
          val newArrowY = arrowY + 1
          val model = AppWith.arrowY (model, newArrowY)

          val dotVec = getDotVecFromIndices (model, arrowX, newArrowY)
          val drawMsg = DRAW_DOT dotVec
          val drawMsg = [DRAW drawMsg]
        in
          (model, drawMsg)
        end
      else
        getDrawDotMsgWhenArrowIsAtBoundary model
    end
end