open System.Windows.Forms
open System.Drawing

type Direction =
| Up
| Down
| Left
| Right

type MoveEll () as this =

    inherit Control()

    let mutable raggio = 50
    let mutable raggioS = 10
    let mutable cbx , cby = 250,250
    let mutable alfa = raggio * 2
    let mutable csx, csy = cbx + alfa, cby + alfa
    let mutable dir = Up
    let mutable pressed = false
    let isClose (p : Point) (l : Point) =
        let dx = p.X - l.X
        let dy = p.Y - l.Y
        (dx * dx + dy * dy) < raggio * raggio


    let timer = new Timer(Interval=30)

    do this.SetStyle(ControlStyles.OptimizedDoubleBuffer,true)

    do timer.Tick.Add( fun e ->
        match dir with
        |   Up -> if csy > cby - alfa then csy <- csy - 30
                  else dir <- Left
                  this.Invalidate()

        |   Down -> if csy < cby + alfa then csy <- csy + 30
                    else dir <- Right
                    this.Invalidate()

        |   Left -> if csx > cbx - alfa then csx <- csx - 30
                    else dir <- Down
                    this.Invalidate()

        |   Right -> if csx < cbx + alfa then csx <- csx + 30
                     else dir <- Up
                     this.Invalidate()
        )


    override this.OnMouseDown e =
      let pc = new Point(cbx,cby)
      let pmouse = new Point(e.X,e.Y)
      if (isClose pc pmouse) then

        if pressed then
                pressed <- false
                timer.Stop()
        else
                pressed <- true
                timer.Start()

      this.Invalidate()

    override this.OnResize e =

        timer.Stop()
        dir <- Up
        csx <- cbx + alfa
        csy <- cby + alfa
        this.Invalidate()

    override this.OnPaint e =
        let g = e.Graphics
        let r = raggio
        let rs = raggioS
        if pressed then
            g.FillEllipse(Brushes.Green,cbx-r,cby-r,r*2,r*2)
        else
            g.FillEllipse(Brushes.Red,cbx-r,cby-r,r*2,r*2)
        g.FillEllipse(Brushes.Black,csx-rs,csy-rs,rs*2,rs*2)



let f = new Form (Text="CrossFingers" , TopMost=true)
f.Size <- new Size(500,500)
let mc = new MoveEll(Dock = DockStyle.Fill)
f.Controls.Add(mc)
f.Show()