{-# LANGUAGE PackageImports, LambdaCase, OverloadedStrings, RecordWildCards #-}
import System.Environment
import "GLFW-b" Graphics.UI.GLFW as GLFW
import Data.Text (unpack,Text)
import Data.List (groupBy,nub)
import Data.Maybe
import Control.Monad
import Data.Map (Map)
import qualified Data.Map as Map
import qualified Data.Vector as V
import qualified Data.ByteString as SB

import LambdaCube.GL as LambdaCubeGL -- renderer
import LambdaCube.GL.Mesh as LambdaCubeGL

import Codec.Picture as Juicy
import Data.Aeson
import Codec.Wavefront

import MtlParser

----------------------------------------------------
--  See:  http://lambdacube3d.com/getting-started
----------------------------------------------------

objToMesh :: WavefrontOBJ -> [(Mesh,Maybe Text)]
objToMesh WavefrontOBJ{..} = [(toMesh faceGroup, elMtl . head $ faceGroup) | faceGroup <- faces] where
  faces = groupBy (\a b -> elMtl a == elMtl b) (V.toList objFaces)
  toMesh l = Mesh
    { mAttributes   = Map.fromList
        [ ("position",  A_V4F position)
        , ("normal",    A_V3F normal)
        , ("uvw",       A_V3F texcoord)
        ]
    , mPrimitive    = P_Triangles
    } where
        triangulate (Triangle a b c) = [a,b,c]
        triangulate (Quad a b c d) = [a,b,c, c,d,a]
        triangulate _ = []
        defaultPosition = Location 0 0 0 0
        defaultNormal = Normal 0 0 0
        defaultTexCoord = TexCoord 0 0 0
        v !- i = v V.!? (i-1)
        toVertex FaceIndex{..} = ( let Location x y z w = fromMaybe defaultPosition (objLocations !- faceLocIndex)            in V4 x y z w
                                 , let Normal x y z     = fromMaybe defaultNormal ((objNormals !-) =<< faceNorIndex)          in V3 x y z
                                 , let TexCoord x y z   = fromMaybe defaultTexCoord ((objTexCoords !-) =<< faceTexCoordIndex) in V3 x y z
                                 )
        (position,normal,texcoord) = V.unzip3 . V.concat . map (V.fromList . map toVertex . triangulate . elValue) $ l


loadOBJ :: String -> IO (Either String ([(Mesh,Maybe Text)],MtlLib))
loadOBJ fname = fromFile fname >>= \case -- load geometry
  Left err -> putStrLn err >> return (Left err)
  Right obj@WavefrontOBJ{..} -> do
    -- load materials
    mtlLib <- mconcat . V.toList <$> mapM (readMtl . unpack) objMtlLibs
    return $ Right (objToMesh obj,mtlLib)

loadOBJToGPU :: String -> IO (Either String ([(GPUMesh, Maybe Text)], MtlLib))
loadOBJToGPU fname = loadOBJ fname >>= \case
  Left err -> return $ Left err
  Right (subModels,mtlLib) -> do
    gpuSubModels <- forM subModels $ \(mesh,mat) -> LambdaCubeGL.uploadMeshToGPU mesh >>= \a -> return (a,mat)
    return $ Right (gpuSubModels,mtlLib)

uploadMtlLib :: MtlLib -> IO (Map Text (ObjMaterial,TextureData))
uploadMtlLib mtlLib = do
  -- collect used textures
  let usedTextures = nub . concatMap (maybeToList . mtl_map_Kd) $ Map.elems mtlLib
      whiteImage = Juicy.ImageRGB8 $ Juicy.generateImage (\_ _ -> Juicy.PixelRGB8 255 255 255) 1 1
      checkerImage = Juicy.ImageRGB8 $ Juicy.generateImage (\x y -> if mod (x + y) 2 == 0 then Juicy.PixelRGB8 0 0 0 else Juicy.PixelRGB8 255 255 0) 2 2
  checkerTex <- LambdaCubeGL.uploadTexture2DToGPU checkerImage
  -- load images and upload to gpu
  textureLib <- forM (Map.fromList $ zip usedTextures usedTextures) $ \fname -> Juicy.readImage fname >>= \case
    Left err  -> putStrLn err >> return checkerTex
    Right img -> LambdaCubeGL.uploadTexture2DToGPU img
  whiteTex <- LambdaCubeGL.uploadTexture2DToGPU whiteImage
  -- pair textures and materials
  return $ (\a -> (a, maybe whiteTex (fromMaybe checkerTex . flip Map.lookup textureLib) . mtl_map_Kd $ a)) <$> mtlLib

addOBJToObjectArray :: GLStorage -> String -> [(GPUMesh, Maybe Text)] -> Map Text (ObjMaterial,TextureData) -> IO [LambdaCubeGL.Object]
addOBJToObjectArray storage slotName objMesh mtlLib = forM objMesh $ \(mesh,mat) -> do
  obj <- LambdaCubeGL.addMeshToObjectArray storage slotName ["diffuseTexture","diffuseColor"] mesh -- diffuseTexture and diffuseColor values can change on each model
  case mat >>= flip Map.lookup mtlLib of
    Nothing -> return ()
    Just (ObjMaterial{..},t) -> LambdaCubeGL.updateObjectUniforms obj $ do
      "diffuseTexture" @= return t -- set model's diffuse texture
      "diffuseColor" @= let (r,g,b) = mtl_Kd in return (V4 r g b mtl_Tr)
  return obj

main :: IO ()
main = do
    Just pipelineDesc <- decodeStrict <$> SB.readFile "hello_obj.json"

    win <- initWindow "LambdaCube 3D DSL OBJ viewer" 640 640

    -- setup render data
    let inputSchema = makeSchema $ do
          defObjectArray "objects" Triangles $ do
            "position"  @: Attribute_V4F
            "normal"    @: Attribute_V3F
            "uvw"       @: Attribute_V3F
          defUniforms $ do
            "time"            @: Float
            "diffuseTexture"  @: FTexture2D
            "diffuseColor"    @: V4F

    storage <- LambdaCubeGL.allocStorage inputSchema

    objName <- head . (++ ["cube.obj"]) <$> getArgs
    -- load OBJ geometry and material descriptions
    Right (objMesh,mtlLib) <- loadOBJToGPU objName
    -- load materials textures
    gpuMtlLib <- uploadMtlLib mtlLib
    -- add OBJ to pipeline input
    addOBJToObjectArray storage "objects" objMesh gpuMtlLib

    -- allocate GL pipeline
    renderer <- LambdaCubeGL.allocRenderer pipelineDesc
    LambdaCubeGL.setStorage renderer storage >>= \case -- check schema compatibility
      Just err -> putStrLn err
      Nothing  -> loop
        where loop = do
                -- update graphics input
                GLFW.getWindowSize win >>= \(w,h) -> LambdaCubeGL.setScreenSize storage (fromIntegral w) (fromIntegral h)
                LambdaCubeGL.updateUniforms storage $ do
                  "time" @= do
                              Just t <- GLFW.getTime
                              return (realToFrac t :: Float)
                -- render
                LambdaCubeGL.renderFrame renderer
                GLFW.swapBuffers win
                GLFW.pollEvents

                let keyIsPressed k = fmap (==KeyState'Pressed) $ GLFW.getKey win k
                escape <- keyIsPressed Key'Escape
                if escape then return () else loop

    LambdaCubeGL.disposeRenderer renderer
    LambdaCubeGL.disposeStorage storage
    GLFW.destroyWindow win
    GLFW.terminate

initWindow :: String -> Int -> Int -> IO Window
initWindow title width height = do
    GLFW.init
    GLFW.defaultWindowHints
    mapM_ GLFW.windowHint
      [ WindowHint'ContextVersionMajor 3
      , WindowHint'ContextVersionMinor 3
      , WindowHint'OpenGLProfile OpenGLProfile'Core
      , WindowHint'OpenGLForwardCompat True
      ]
    Just win <- GLFW.createWindow width height title Nothing Nothing
    GLFW.makeContextCurrent $ Just win
    return win