module InputHandler 
( Event

, handleInput
, composeInputHandler

, handleSpace
, handleEnter
, handleUp
, handleDown
, handleLeft
, handleRight
) where

import Graphics.Gloss
import qualified Graphics.Gloss.Interface.IO.Game as Game

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

-- Something that happens, most often a keypress
type Event = Game.Event

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

-- Handle input by taking a keyCheck function that checks wheter or not
-- a key is being presse
handleInput :: Game.SpecialKey -> (a -> a) -> Event -> a -> a
handleInput key convert ev currentState
    | isKey key ev = convert currentState
    | otherwise    = currentState

-- Compose multiple InputHandlers into one combined InputHandler.
composeInputHandler :: [Event -> a -> a] -> Event -> a -> a
composeInputHandler (ih:ihs) ev a = composeInputHandler ihs ev (ih ev a)
composeInputHandler []       ev a = a

-- Check if the requested key is pressed.
isKey :: Game.SpecialKey -> Event -> Bool
isKey k1 (Game.EventKey (Game.SpecialKey k2) Game.Down _ _) = k1 == k2
isKey _  _                                                  = False

------------------ A couple of default inputhandlers -----------------

handleSpace :: (a -> a) -> Event -> a -> a
handleSpace = handleInput Game.KeySpace

handleEnter :: (a -> a) -> Event -> a -> a
handleEnter = handleInput Game.KeyEnter

handleUp :: (a -> a) -> Event -> a -> a
handleUp = handleInput Game.KeyUp

handleDown :: (a -> a) -> Event -> a -> a
handleDown = handleInput Game.KeyDown

handleLeft :: (a -> a) -> Event -> a -> a
handleLeft = handleInput Game.KeyLeft

handleRight :: (a -> a) -> Event -> a -> a
handleRight = handleInput Game.KeyRight