-- State.hs
module Graphics.GD.State where

import Control.Monad.State.Lazy (State(..),modify,execState)
import qualified Graphics.GD as GD

data GDCmd = SetPixel GD.Point GD.Color

data GD' = GD' { gdCmds :: [GDCmd] }
type GD a = State GD' a

consCmd :: GDCmd -> GD ()
consCmd cmd = modify $ \gd -> gd { gdCmds = cmd : (gdCmds gd) }

setPixel :: GD.Point -> GD.Color -> GD ()
setPixel = (consCmd .) . SetPixel

newImage :: GD.Size -> GD () -> IO GD.Image
newImage size f = do
    im <- GD.newImage size
    mapM_ (flip runCmd $ im) $ gdCmds $ execState f $ GD' []
    return im

runCmd :: GDCmd -> GD.Image -> IO ()
runCmd (SetPixel pt c) = GD.setPixel pt c