module World
	( Segment
	, World(..)
	, initialWorld
	, normaliseWorld)
where
import Graphics.Gloss
import Geometry.Randomish
import Geometry.Segment
import qualified Array	as A
import Array		(Array)


-- We keep this unpacked so we can use unboxed vector.
-- index, x1, y1, x2, y2
data World 
	= World
	{ worldSegments	:: Array Segment }


-- | Generate the initial world.
initialWorld :: IO World
initialWorld
 = do	let n		= 100
	let minZ	= -300
	let maxZ	= 300
	
	let minDelta	= -100
	let maxDelta	=  100
	
	let centers	= randomishPoints 1234 n minZ     maxZ
	let deltas	= randomishPoints 4321 n minDelta maxDelta

	let makePoint n' (cX, cY) (dX, dY)
			= (n', (cX, cY), (cX + dX, cY + dY))

	let segs	= A.zipWith3 makePoint (A.enumFromTo 0 (n - 1)) centers deltas
	
	return $ World segs


-- | Normalise the world so that the given point is at the origin,
--   and split segements that cross the y=0 line.
normaliseWorld :: Point -> World -> World 
normaliseWorld (px, py) world
 = let	segments_trans	= A.map (translateSegment (-px) (-py)) 
			$ worldSegments world
			
	segments_split	= splitSegmentsOnY 0 segments_trans
			
   in	world { worldSegments = segments_split }