--{-# LANGUAGE DeriveAnyClass #-}
--{-# LANGUAGE DeriveGeneric #-}
--{-# LANGUAGE StandaloneDeriving #-}
--{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

{- |
WARNING: orphan instances concerning Aeson classes and Linear.Quaternion datatypes have been introduced.
The warnings have been disabled.
-}
module Quaternion (
    rotateToZ,
    vToQuat,
    module Linear.Quaternion,
) where

import Data.Aeson
import Geometry.Data
import Geometry.Vector3D
import Linear.Quaternion
import qualified Linear.Quaternion as Q

instance ToJSON a => ToJSON (Q.Quaternion a) where
    toEncoding = genericToEncoding defaultOptions

instance FromJSON a => FromJSON (Q.Quaternion a)

-- apply a rotation as if the z axis moves to the new point.
-- i think this may instead do as if the new point moves to be on z axis
rotateToZ :: Point3 -> Point3 -> Point3
rotateToZ z1
    | cprod == V3 0 0 0 = id
    | otherwise = Q.rotate $ Q.axisAngle cprod (angleVV3 z1 (V3 0 0 1))
  where
    cprod = crossProd z1 (V3 0 0 1)

vToQuat :: Point3 -> Point3 -> Q.Quaternion Float
vToQuat a b
    | cprod == V3 0 0 0 = Q.axisAngle (V3 0 0 1) 0
    | otherwise = Q.axisAngle cprod (angleVV3 a b)
  where
    cprod = crossProd a b

--deriving instance (Flat a => Flat (Quaternion a))