transit.hs

import Data.IORef

data Scene = Scene { keyboardHandler :: Char -> IO ()
                   , stepHandler     :: IO ()
                   , drawHandler     :: IO ()
                   }

mkTitle :: IORef Scene -> IO Scene
mkTitle transit = do
    x <- newIORef 0
    return $ Scene { keyboardHandler = \key -> if key == 'e' -- Enter
                                                   then do
                                                       let game = mkGame x transit
                                                       writeIORef transit game
                                                   else return ()
                   , stepHandler = modifyIORef x (+1)
                   , drawHandler = print =<< readIORef x -- Graphics.drawCircle(x, h)
                   }

mkGame :: IORef Int -> IORef Scene -> Scene
mkGame x transit = do
    Scene { keyboardHandler = \key -> if key == 'c' -- ESC
                                          then do
                                              title <- mkTitle transit
                                              writeIORef transit title
                                          else return ()
          , stepHandler = modifyIORef x (subtract 1)
          , drawHandler = print =<< readIORef x -- Graphics.drawCircle(x, h)
          }

main = do
    let dummy = Scene (const (return ())) (return ()) (return ())
    sceneRef <- newIORef dummy
    title <- mkTitle sceneRef
    writeIORef sceneRef title
    loop sceneRef
    where
    loop sceneRef = do
        -- c <- getChar
        scene <- readIORef sceneRef
        -- keyboardHandler scene c
        stepHandler scene
        drawHandler scene
        loop sceneRef