{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, TypeSynonymInstances #-}

module Vector where

import Control.Applicative
import FRP.Elerea.Param
import Graphics.Rendering.OpenGL

data Vec = V { getX :: {-# UNPACK #-} !GLfloat, getY :: {-# UNPACK #-} !GLfloat }

infixl 7 ^*.
infixl 7 .*^
infixl 7 ^/.
infixl 7 `dot`
infixl 7 `cross`
infixl 6 ^+^
infixl 6 ^-^

class Vector2D v c | v -> c where
  (^+^) :: v -> v -> v
  (^-^) :: v -> v -> v
  (^*.) :: v -> c -> v
  (.*^) :: c -> v -> v
  (^/.) :: v -> c -> v
  vnull :: v
  dot :: v -> v -> c
  cross :: v -> v -> c
  vlen :: v -> c
  mul :: v -> v -> v

instance Vector2D Vec GLfloat where
  V x1 y1 ^+^ V x2 y2 = V (x1+x2) (y1+y2)
  V x1 y1 ^-^ V x2 y2 = V (x1-x2) (y1-y2)
  V x y ^*. t = V (x*t) (y*t)
  t .*^ V x y = V (x*t) (y*t)
  V x y ^/. t = V (x/t) (y/t)
  vnull = V 0 0
  V x1 y1 `dot` V x2 y2 = x1*x2+y1*y2
  V x1 y1 `cross` V x2 y2 = x1*y2-x2*y1
  vlen (V x y) = sqrt (x*x+y*y)
  V x1 y1 `mul` V x2 y2 = V (x1*x2) (y1*y2)

instance Vector2D (Signal Vec) (Signal GLfloat) where
  (^+^) = liftA2 (^+^)
  (^-^) = liftA2 (^-^)
  (^*.) = liftA2 (^*.)
  (.*^) = liftA2 (.*^)
  (^/.) = liftA2 (^/.)
  vnull = pure vnull
  dot = liftA2 dot
  cross = liftA2 cross
  vlen = fmap vlen
  mul = liftA2 mul