{-# LANGUAGE PatternGuards #-}
module Interface
	( handleInput
	, stepState)
where
import State
import qualified Graphics.Gloss.Interface.Pure.Game	as G

-- Input ------------------------------------------------------------------------------------------
-- | Handle an input event.
handleInput :: G.Event -> State -> State

handleInput (G.EventKey key keyState _ (x, y)) state
	-- move the view position.
	| G.MouseButton G.LeftButton	<- key
	, G.Down			<- keyState
	= state	{ stateModeInterface	= ModeInterfaceMove 
		, stateViewPos
			= ( fromRational $ toRational x
			  , fromRational $ toRational y) }

	-- set the target position.
	| G.MouseButton G.RightButton	<- key
	, G.Down			<- keyState
	= state	{ stateTargetPos
			= Just ( fromRational $ toRational x
			       , fromRational $ toRational y) }

	| G.MouseButton G.LeftButton	<- key
	, G.Up				<- keyState
	= state	{ stateModeInterface	= ModeInterfaceIdle }

handleInput (G.EventMotion (x, y)) state
	| stateModeInterface state == ModeInterfaceMove
	= state { stateViewPos
			= ( fromRational $ toRational x
			  , fromRational $ toRational y) }

-- t : Turn target indicator off.
handleInput (G.EventKey key keyState _ _) state
	| G.Char 't'			<- key
	, G.Down			<- keyState
	= state	{ stateTargetPos	= Nothing }

-- w : Display the whole world.
handleInput (G.EventKey key keyState _ _) state
	| G.Char 'w'			<- key
	, G.Down			<- keyState
	= state	{ stateModeDisplay	= ModeDisplayWorld }

-- n : Display the normalised world.
handleInput (G.EventKey key keyState _ _) state
	| G.Char 'n'			<- key
	, G.Down			<- keyState
	= state	{ stateModeDisplay	= ModeDisplayNormalised }

-- a : Toggle approximate visibility
handleInput (G.EventKey key keyState _ _) state
	| G.Char 'a'			<- key
	, G.Down			<- keyState
	= state { stateModeOverlay
			= case stateModeOverlay state of
				ModeOverlayVisApprox	-> ModeOverlayNone
				_			-> ModeOverlayVisApprox }	

handleInput _ state
	= state

-- Step -------------------------------------------------------------------------------------------
-- | Advance the state one iteration
stepState :: Float -> State -> State
stepState _ state = state