Nsryjdtyk

This is function, that works correctly, but it seems to be too ugly.
panel argument is never used for anything but pushing into refreshGamePanel,
and it seems to be too much case statements. How can I cleanup this?

runGameLoop :: Game -> Panel -> Curses GameResult

runGameLoop game panel

  = if victory game then return Victory else

      refreshGamePanel game panel >> render >> getPanelWindow panel >>=

        flip getEvent (Just 1)

        >>=

         event' ->

          case event' of

              Nothing -> runGameLoop game panel

              Just event -> case event of

                EventSpecialKey (KeyFunction 2) -> return Restart

                EventSpecialKey (KeyFunction 10) -> return Quit

                EventSpecialKey key' -> case keyToDirection key' of

                  Nothing -> runGameLoop game panel

                  Just dir -> runGameLoop (makeMove game dir) panel

                _ -> runGameLoop game panel

There is a nice language extension in GHC called ViewPatterns. Together with LambdaCase that fature allows you to shorten your code, I think. And do notation will be much more readable for imperative part.

runGameLoop game panel | victory game = return Victory

                       | otherwise = continue

    where

      anyEvent = gatPanelWindow panel >>= flip getEvent (Just 1)

      isRestart = (EventSpecialKey (KeyFunction 2) ==)

      isQuit = (EventSpecialKey (KeyFunction 10) ==)

      continue = do

          refreshGamePanel game panel

          render

          anyEvent >>= case

              Just (isRestart -> True) -> return Restart

              Just (isQuit -> True) -> return Quit

              Just (EventSpecialKey (keyToDirection -> Just dir)) ->

                  runGameLoop (makeMove game dir) panel

              _ -> runGameLoop game panel

Another variant is to consider using of Monad Maybe instance

runGameLoop game panel = nextStep where

    anyEvent = gatPanelWindow panel >>= flip getEvent (Just 1)

    nextStep = if victory game then return Victory else do

        refreshGamePanel game panel

        render

        liftM react anyEvent >>= case

            Just continuation -> continuation

            Nothing -> runGameLoop game panel

    react event' = do

        event' >>= case

            EventSpecialKey (KeyFunction 2) -> return (return Restart)

            EventSpecialKey (KeyFunction 10) -> return (return Quit)

            EventSpecialKey key -> do

                dir <- keyToDirection key

                return (runGameLoop (makeMove game dir) panel)

            _ -> Nothing