import Color exposing (..)
import Graphics.Collage exposing (..)
import Graphics.Element exposing (..)
import Mouse
import Window


main : Signal Element
main =
  Signal.map3 scene Mouse.position anchor Window.dimensions

scene : (Int,Int) -> (Int,Int) -> (Int,Int) -> Element
scene (x,y) (z,a) (w,h) =
  let (dx,dy) =
        (toFloat x - toFloat w / 2, toFloat h / 2 - toFloat y)
      (dz,da) =
        (toFloat z - toFloat w / 2, toFloat h / 2 - toFloat a)
  in
      collage w h
        [ ngon 3 100
            |> filled blue
            |> rotate (atan2 (da - dy) (dz - dx))
            |> move (dz, da)
        , ngon 6 30
            |> filled orange
            |> move (dx, dy)
        ]

anchor : Signal (Int, Int)
anchor =
  Signal.foldp
    avera
    (0,0)
    Mouse.position

avera : (Int, Int) -> (Int, Int) -> (Int, Int)
avera (newx, newy) (oldx, oldy) =
  ( round (toFloat oldx * 0.99 + toFloat newx * 0.01)
  , round (toFloat oldy * 0.99 + toFloat newy * 0.01)
  )