-- Allows to create a massive inputHandler that can handle anything
-- after you specify what you want it to do.

module InputHandling
( InputHandler(..),
-- Compose multiple InputHandlers into one InputHandler that handles
-- all of them.
composeInputHandlers,

handle, 
handleSpecialKey
) where

import Graphics.Gloss.Interface.IO.Game

----------------------------- Constants ------------------------------

type InputHandler a = Event -> (a -> a)

----------------------------------------------------------------------

composeInputHandlers :: [InputHandler a] -> InputHandler a
composeInputHandlers []       ev a = a
composeInputHandlers (ih:ihs) ev a = composeInputHandlers ihs ev (ih ev a)

handle :: Event -> (a -> a) -> Event -> (a -> a)
handle (EventKey key _ _ _) = handleKey key
-- handle (EventMotion _)      = undefined
-- handle (EventResize _)      = undefined
handle _                    = (\_ -> (\_ -> id))

handleKey :: Key -> (a -> a) -> Event -> (a -> a)
handleKey (SpecialKey  key) = handleSpecialKey key
handleKey (Char        _  ) = (\_ -> (\_ -> id))
handleKey (MouseButton _  ) = (\_ -> (\_ -> id))

handleSpecialKey :: SpecialKey -> (a -> a) -> Event -> (a -> a)
handleSpecialKey sk1 f (EventKey (SpecialKey sk2) Down _ _)
    | sk1 == sk2 = f
    | otherwise  = id
handleSpecialKey _   _ _ = id