{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE TupleSections              #-}

{-# OPTIONS_GHC -Wno-unused-foralls #-}
{-# OPTIONS_GHC -Wno-unused-matches #-}
module Graphics.GPipe.Internal.FrameBuffer where

import           Control.Monad                           (void, when)
import           Control.Monad.IO.Class                  (MonadIO (liftIO))
import           Control.Monad.Trans.Class               (MonadTrans (lift))
import           Control.Monad.Trans.Except              (ExceptT, throwE)
import           Control.Monad.Trans.State.Lazy          (StateT (..), get, put)
import qualified Control.Monad.Trans.State.Strict        as StrictState
import           Control.Monad.Trans.Writer.Lazy         (Writer, execWriter,
                                                          tell)
import           Data.IORef                              (mkWeakIORef, newIORef,
                                                          readIORef)
import qualified Data.IntMap.Polymorphic                 as IMap
import           Data.Text.Lazy                          (Text)
import qualified Data.Text.Lazy                          as LT
import qualified Data.Text.Lazy.IO                       as LT
import           Foreign.Marshal.Alloc                   (alloca)
import           Foreign.Marshal.Array                   (withArray)
import           Foreign.Marshal.Utils                   (fromBool, with)
import           Foreign.Ptr                             (nullPtr)
import           Foreign.Storable                        (peek)
import           Graphics.GL.Core45
import           Graphics.GL.Types                       (GLenum, GLuint)
import           Graphics.GPipe.Internal.Compiler        (Drawcall (Drawcall),
                                                          getFboError)
import           Graphics.GPipe.Internal.Context         (FBOKey,
                                                          FBOKeys (FBOKeys),
                                                          Render (Render),
                                                          RenderState (perWindowRenderState),
                                                          Window (getWinName),
                                                          asSync, getFBO,
                                                          getLastRenderWin,
                                                          setFBO)
import           Graphics.GPipe.Internal.Expr            (ExprM,
                                                          ExprResult (ExprResult),
                                                          F, FFloat, GlobDeclM,
                                                          S (..), discard,
                                                          runExprM,
                                                          tellAssignment',
                                                          tellGlobal,
                                                          tellGlobalLn, tshow)
import           Graphics.GPipe.Internal.Format          (ColorRenderable (clearColor),
                                                          ColorSampleable (Color, ColorElement, fromColor, typeStr),
                                                          ContextColorFormat,
                                                          DepthRenderable,
                                                          DepthStencil, Format,
                                                          StencilRenderable)
import           Graphics.GPipe.Internal.FragmentStream  (FragmentStream (..),
                                                          FragmentStreamData (..))
import           Graphics.GPipe.Internal.IDs             (WinId)
import           Graphics.GPipe.Internal.PrimitiveStream (PrimitiveStreamData (PrimitiveStreamData))
import           Graphics.GPipe.Internal.Shader          (Shader (..), ShaderM,
                                                          tellDrawcall)
import           Graphics.GPipe.Internal.Texture         (ComparisonFunction,
                                                          Image, getGlCompFunc,
                                                          getImageBinding,
                                                          getImageFBOKey,
                                                          imageEquals)
import           Language.GLSL.Optimizer                (optimizeShader)
import           Linear.V4                               (V4 (..))
import qualified System.Environment                      as Env

-- | A monad in which individual color images can be drawn.
newtype DrawColors os s a = DrawColors (StateT Int (Writer [Int -> (ExprM (), GlobDeclM (), s -> (IO FBOKey, IO (), IO ()))]) a) deriving (Functor, Applicative, Monad)

runDrawColors :: DrawColors os s a -> (ExprM (), GlobDeclM (), s -> (IO [FBOKey], IO (), IO ()))
runDrawColors (DrawColors m) = foldl sf (return (), return (), const (return [], return (), return ())) $ zip [0 ..] $ execWriter (runStateT m 0)
    where
        sf (ms, mg, mio) (n, f) = let (sh, g, io) = f n in (ms >> sh, mg >> g, sf' mio io)
        sf' mio io s =
            let (a, b, c) = mio s
                (x, y, z) = io s
            in  ( do
                    ns <- a
                    n <- x
                    return $ ns ++ [n]
                , b >> y
                , c >> z
                )

-- | Draw color values into a color renderable texture image.
drawColor :: forall c s os. ColorRenderable c => (s -> (Image (Format c), ColorMask c, UseBlending)) -> FragColor c -> DrawColors os s ()
drawColor sf c = DrawColors $ do
    n <- get
    put $ n + 1
    lift $
        tell
            [ \ix -> make3 (setColor cf ix c) $ \s ->
                let (i, mask, o) = sf s
                    n' = fromIntegral n
                    useblend = if o then glEnablei GL_BLEND n' else glDisablei GL_BLEND n'
                in  ( getImageFBOKey i
                    , getImageBinding i (GL_COLOR_ATTACHMENT0 + n')
                    , do
                        useblend
                        setGlColorMask cf n' mask
                    )
            ]
    where
        cf = undefined :: c

-- | Draw all fragments in a 'FragmentStream' using the provided function that
--   passes each fragment value into a 'DrawColors' monad. The first argument is
--   a function that retrieves a 'Blending' setting from the shader environment,
--   which will be used for all 'drawColor' actions in the 'DrawColors' monad
--   where 'UseBlending' is 'True'. (OpenGL 3.3 unfortunately doesn't support
--   having different blending settings for different color targets.)
--
--   TODO: we're using OpenGL 4.5 now. Is this still true?
draw :: forall a os f s. (s -> Blending)
    -> FragmentStream a
    -> (a -> DrawColors os s ())
    -> Shader os s ()

-- | Like 'draw', but performs a depth test on each fragment first. The
--   'DrawColors' monad is then only run for fragments where the depth test
--   passes.
drawDepth :: forall a os f s d. DepthRenderable d
    => (s -> (Blending, Image (Format d), DepthOption))
    -> FragmentStream (a, FragDepth)
    -> (a -> DrawColors os s ())
    -> Shader os s ()

-- | Like 'draw', but performs a stencil test on each fragment first. The
--   'DrawColors' monad is then only run for fragments where the stencil test
--   passes.
drawStencil :: forall a os f s st. StencilRenderable st
    => (s -> (Blending, Image (Format st), StencilOptions))
    -> FragmentStream a
    -> (a -> DrawColors os s ())
    -> Shader os s ()

-- | Like 'draw', but performs a stencil test and a depth test (in that order)
--   on each fragment first. The 'DrawColors' monad is then only run for
--   fragments where the stencil and depth test passes.
drawDepthStencil :: forall a os f s d st. (DepthRenderable d, StencilRenderable st)
    => (s -> (Blending, Image (Format d), Image (Format st), DepthStencilOption))
    -> FragmentStream (a, FragDepth)
    -> (a -> DrawColors os s ())
    -> Shader os s ()

makeFBOKeys :: IO [FBOKey] -> IO (Maybe FBOKey) -> IO (Maybe FBOKey) -> IO FBOKeys
makeFBOKeys c d s =
    FBOKeys <$> c <*> d <*> s

draw sf fs m = Shader $ tellDrawcalls fs $ \c -> let (sh, g, ioc) = runDrawColors (m c) in (sh, g, f ioc)
    where
        f ioc s =
            let (fbokeyio, fboio, io) = ioc s
                b = sf s
            in  ( Right (makeFBOKeys fbokeyio (return Nothing) (return Nothing), fboio)
                , io >> glDisable GL_DEPTH_TEST >> glDisable GL_STENCIL_TEST >> setGlBlend b
                )

drawDepth sf fs m = Shader $ tellDrawcalls fs $ \(c, d) -> let (sh, g, ioc) = runDrawColors (m c) in (sh >> setDepth d, g, f ioc)
    where
        f ioc s =
            let (fbokeyio, fboio, io) = ioc s
                (b, di, o) = sf s
            in  ( Right
                    ( makeFBOKeys fbokeyio (Just <$> getImageFBOKey di) (return Nothing)
                    , fboio >> getImageBinding di GL_DEPTH_ATTACHMENT
                    )
                , io >> glDisable GL_STENCIL_TEST >> setGlBlend b >> setGlDepthOptions o
                )

drawStencil sf fs m = Shader $ tellDrawcalls fs $ \c -> let (sh, g, ioc) = runDrawColors (m c) in (sh, g, f ioc)
    where
        f ioc s =
            let (fbokeyio, fboio, io) = ioc s
                (b, si, o) = sf s
            in  ( Right
                    ( makeFBOKeys fbokeyio (return Nothing) (Just <$> getImageFBOKey si)
                    , fboio >> getImageBinding si GL_STENCIL_ATTACHMENT
                    )
                , io >> glDisable GL_DEPTH_TEST >> setGlBlend b >> setGlStencilOptions o OpZero OpZero
                )

drawDepthStencil sf fs m = Shader $ tellDrawcalls fs $ \(c, d) -> let (sh, g, ioc) = runDrawColors (m c) in (sh >> setDepth d, g, f ioc)
    where
        f ioc s =
            let (fbokeyio, fboio, io) = ioc s
                (b, di, si, o) = sf s
            in  ( Right
                    ( makeFBOKeys fbokeyio (Just <$> getImageFBOKey di) (Just <$> getImageFBOKey si)
                    , fboio >> getCombinedBinding di si
                    )
                , io >> setGlBlend b >> setGlDepthStencilOptions o
                )
        getCombinedBinding di si
            | imageEquals di si = getImageBinding di GL_DEPTH_STENCIL_ATTACHMENT
            | otherwise = getImageBinding di GL_DEPTH_ATTACHMENT >> getImageBinding si GL_STENCIL_ATTACHMENT

-- | Draw color values from a 'FragmentStream' into the window.
drawWindowColor :: forall os s c ds. ContextColorFormat c
    => (s -> (Window os c ds, ContextColorOption c))
    -> FragmentStream (FragColor c) -> Shader os s ()

-- | Perform a depth test for each fragment from a 'FragmentStream' in the
--   window. This doesn't draw any color values and only affects the depth
--   buffer.
drawWindowDepth :: forall os s c ds. DepthRenderable ds
    => (s -> (Window os c ds, DepthOption))
    -> FragmentStream FragDepth -> Shader os s ()

-- | Perform a depth test for each fragment from a 'FragmentStream' and write a
--   color value from each fragment that passes the test into the window.
drawWindowColorDepth :: forall os s c ds. (ContextColorFormat c, DepthRenderable ds)
    => (s -> (Window os c ds, ContextColorOption c, DepthOption))
    -> FragmentStream (FragColor c, FragDepth) -> Shader os s ()

-- | Perform a stencil test for each fragment from a 'FragmentStream' in the
--   window. This doesn't draw any color values and only affects the stencil buffer.
drawWindowStencil :: forall os s c ds. StencilRenderable ds
    => (s -> (Window os c ds, StencilOptions))
    -> FragmentStream () -> Shader os s ()

-- | Perform a stencil test for each fragment from a 'FragmentStream' and write
--   a color value from each fragment that passes the test into the window.
drawWindowColorStencil :: forall os s c ds. (ContextColorFormat c, StencilRenderable ds)
    => (s -> (Window os c ds, ContextColorOption c, StencilOptions))
    -> FragmentStream (FragColor c) -> Shader os s ()

-- | Perform a stencil test and depth test (in that order) for each fragment
--   from a 'FragmentStream' in the window. This doesnt draw any color values
--   and only affects the depth and stencil buffer.
drawWindowDepthStencil :: forall os s c ds. (DepthRenderable ds, StencilRenderable ds)
    => (s -> (Window os c ds, DepthStencilOption))
    -> FragmentStream FragDepth -> Shader os s ()

-- | Perform a stencil test and depth test (in that order) for each fragment
--   from a 'FragmentStream' and write a color value from each fragment that
--   passes the tests into the window.
drawWindowColorDepthStencil :: forall os s c ds. (ContextColorFormat c, DepthRenderable ds, StencilRenderable ds)
    => (s -> (Window os c ds, ContextColorOption c, DepthStencilOption))
    -> FragmentStream (FragColor c, FragDepth) -> Shader os s ()

drawWindowColor sf fs = Shader $ tellDrawcalls fs $ \a -> make3 (setColor cf 0 a) io
    where
        io s = let (w, op) = sf s in (Left (getWinName w), glDisable GL_DEPTH_TEST >> glDisable GL_STENCIL_TEST >> setGlContextColorOptions cf op)
        cf = undefined :: c

drawWindowDepth sf fs = Shader $ tellDrawcalls fs $ \a -> (setDepth a, return (), io)
    where
        io s = let (w, op) = sf s in (Left (getWinName w), glDisable GL_STENCIL_TEST >> setGlDepthOptions op)

drawWindowColorDepth sf fs = Shader $ tellDrawcalls fs $ \(c, d) -> let (s, g) = setColor cf 0 c in (s >> setDepth d, g, io)
    where
        io s = let (w, cop, dop) = sf s in (Left (getWinName w), glDisable GL_STENCIL_TEST >> setGlContextColorOptions cf cop >> setGlDepthOptions dop)
        cf = undefined :: c

drawWindowStencil sf fs = Shader $ tellDrawcalls fs $ const (return (), return (), io)
    where
        io s = let (w, op) = sf s in (Left (getWinName w), glDisable GL_DEPTH_TEST >> setGlStencilOptions op OpZero OpZero)

drawWindowColorStencil sf fs = Shader $ tellDrawcalls fs $ \a -> make3 (setColor cf 0 a) io
    where
        io s = let (w, cop, dop) = sf s in (Left (getWinName w), glDisable GL_DEPTH_TEST >> setGlContextColorOptions cf cop >> setGlStencilOptions dop OpZero OpZero)
        cf = undefined :: c

drawWindowDepthStencil sf fs = Shader $ tellDrawcalls fs $ \a -> (setDepth a, return (), io)
    where
        io s = let (w, op) = sf s in (Left (getWinName w), setGlDepthStencilOptions op)

drawWindowColorDepthStencil sf fs = Shader $ tellDrawcalls fs $ \(c, d) -> let (s, g) = setColor cf 0 c in (s >> setDepth d, g, io)
    where
        io s = let (w, cop, dop) = sf s in (Left (getWinName w), setGlContextColorOptions cf cop >> setGlDepthStencilOptions dop)
        cf = undefined :: c

tellDrawcalls :: FragmentStream a -> (a -> (ExprM (), GlobDeclM (), s -> (Either WinId (IO FBOKeys, IO ()), IO ()))) -> ShaderM s ()
tellDrawcalls (FragmentStream xs) f = do
    let g (x, fd) = tellDrawcall $ makeDrawcall (f x) fd
    mapM_ g xs

makeDrawcall ::
    (   ExprM (), -- sh - shader
        GlobDeclM (), -- shd - shader declarations
        s -> (Either WinId (IO FBOKeys, IO ()), IO ()) -- wOrIo - where to draw, as a window ID or a FBO (only this second case seems to be used)
    ) ->
    FragmentStreamData ->
    IO (Drawcall s)
makeDrawcall (sh, shd, wOrIo) (FragmentStreamData rastN False shaderpos (PrimitiveStreamData primN ubuff) keep) =
    do
        ExprResult fsource funis fsamps _ prevDecls prevS <- runExprM shd (discard keep >> sh)
        ExprResult vsource vunis vsamps vinps _ _ <- runExprM prevDecls (prevS >> shaderpos)
        let prefix = "generated-shaders/shader" <> show primN
        dumpGeneratedFile prefix ".frag" fsource
        dumpGeneratedFile prefix ".vert" vsource
        return $ Drawcall wOrIo Nothing primN (Just rastN) vsource Nothing (Just fsource) vinps vunis vsamps [] [] funis fsamps ubuff
makeDrawcall (sh, shd, wOrIo) (FragmentStreamData rastN True shaderpos (PrimitiveStreamData primN ubuff) keep) =
    do
        ExprResult fsource funis fsamps _ prevDecls prevS <- runExprM shd (discard keep >> sh)
        ExprResult gsource gunis gsamps _ prevDecls2 prevS2 <- runExprM prevDecls (prevS >> shaderpos)
        ExprResult vsource vunis vsamps vinps _ _ <- runExprM prevDecls2 prevS2
        let prefix = "generated-shaders/shader" <> show primN
        dumpGeneratedFile prefix ".frag" fsource
        dumpGeneratedFile prefix ".geom" gsource
        dumpGeneratedFile prefix ".vert" vsource
        return $ Drawcall wOrIo Nothing primN (Just rastN) vsource (Just gsource) (Just fsource) vinps vunis vsamps gunis gsamps funis fsamps ubuff

dumpGeneratedFile :: FilePath -> String -> Text -> IO ()
dumpGeneratedFile prefix extension text = do
    shouldWrite <- ("GPIPE_DEBUG" `elem`) . map fst <$> Env.getEnvironment
    when shouldWrite $ do
      LT.writeFile (prefix <> ".out" <> extension) text
      LT.writeFile (prefix <> ".opt" <> extension) $
            case optimizeShader text of
                Left err -> "// " <> LT.pack err
                Right ok -> ok

setColor :: forall c. ColorSampleable c => c -> Int -> FragColor c -> (ExprM (), GlobDeclM ())
setColor ct n c =
    let name = "out" <> tshow n
        typeS = typeStr ct
    in  ( do
            xs <- mapM unS (fromColor ct c :: [S F (ColorElement c)])
            tellAssignment' name (typeS <> "(" <> LT.intercalate "," xs <> ")")
        , do
            tellGlobal "layout(location = "
            tellGlobal $ tshow n
            tellGlobal ") out "
            tellGlobal typeS
            tellGlobal " "
            tellGlobalLn name
        )

setDepth :: FFloat -> ExprM ()
setDepth (S d) = do
    d' <- d
    when (d' /= "gl_FragDepth") $
        tellAssignment' "gl_FragDepth" d'

make3 :: (t, t1) -> t2 -> (t, t1, t2)
make3 (a, b) c = (a, b, c)

type FragColor c = Color c (S F (ColorElement c))

type FragDepth = FFloat

setGlColorMask :: ColorSampleable f => f -> GLuint -> Color f Bool -> IO ()
setGlColorMask c i mask = glColorMaski i x y z w
    where
        [x, y, z, w] = map fromBool $ take 4 $ fromColor c mask ++ [False, False, False]

setGlContextColorOptions :: ColorSampleable f => f -> ContextColorOption f -> IO ()
setGlContextColorOptions c (ContextColorOption blend mask) = do
    setGlColorMask c 0 mask
    setGlBlend blend
    case blend of
        NoBlending -> glDisable GL_BLEND
        LogicOp _  -> glDisable GL_BLEND
        _          -> glEnable GL_BLEND

setGlBlend :: Blending -> IO ()
setGlBlend NoBlending = return ()
setGlBlend (BlendRgbAlpha (e, ea) (BlendingFactors sf df, BlendingFactors sfa dfa) (V4 r g b a)) = do
    glBlendEquationSeparate (getGlBlendEquation e) (getGlBlendEquation ea)
    glBlendFuncSeparate (getGlBlendFunc sf) (getGlBlendFunc df) (getGlBlendFunc sfa) (getGlBlendFunc dfa)
    when (usesConstantColor sf || usesConstantColor df || usesConstantColor sfa || usesConstantColor dfa) $
        glBlendColor (realToFrac r) (realToFrac g) (realToFrac b) (realToFrac a)
setGlBlend (LogicOp op) = glEnable GL_COLOR_LOGIC_OP >> glLogicOp (getGlLogicOp op)

setGlDepthOptions :: DepthOption -> IO ()
setGlDepthOptions (DepthOption df dm) = do
    glEnable GL_DEPTH_TEST
    glDepthFunc (getGlCompFunc df)
    glDepthMask $ fromBool dm

setGlStencilOptions :: FrontBack StencilOption -> StencilOp -> StencilOp -> IO ()
setGlStencilOptions (FrontBack (StencilOption ft fr ff fp frm fwm) (StencilOption bt br bf bp brm bwm)) fdf bdf = do
    glEnable GL_STENCIL_TEST
    glStencilFuncSeparate GL_FRONT (getGlCompFunc ft) (fromIntegral fr) (fromIntegral frm)
    glStencilOpSeparate GL_FRONT (getGlStencilOp ff) (getGlStencilOp fdf) (getGlStencilOp fp)
    glStencilMaskSeparate GL_FRONT (fromIntegral fwm)
    glStencilFuncSeparate GL_BACK (getGlCompFunc bt) (fromIntegral br) (fromIntegral brm)
    glStencilOpSeparate GL_BACK (getGlStencilOp bf) (getGlStencilOp bdf) (getGlStencilOp bp)
    glStencilMaskSeparate GL_BACK (fromIntegral bwm)

setGlDepthStencilOptions :: DepthStencilOption -> IO ()
setGlDepthStencilOptions (DepthStencilOption sop dop (FrontBack fdf bdf)) = do
    setGlDepthOptions dop
    setGlStencilOptions sop fdf bdf

data ContextColorOption f = ContextColorOption Blending (ColorMask f)

data DepthOption = DepthOption DepthFunction DepthMask

type StencilOptions = FrontBack StencilOption

data StencilOption = StencilOption
    { stencilTest         :: ComparisonFunction
    , stencilReference    :: Int
    , opWhenStencilFail   :: StencilOp
    , opWhenStencilPass   :: StencilOp
    , stencilReadBitMask  :: Word
    , stencilWriteBitMask :: Word
    }

data DepthStencilOption = DepthStencilOption
    { dsStencilOptions              :: StencilOptions
    , dsDepthOption                 :: DepthOption
    , opWhenStencilPassButDepthFail :: FrontBack StencilOp
    }

data FrontBack a = FrontBack {front :: a, back :: a}

-- | 'True' for each color component that should be written to the target.
type ColorMask f = Color f Bool

-- | 'True' if the depth component should be written to the target.
type DepthMask = Bool

-- | The function used to compare the fragment's depth and the depth buffers depth with. E.g. 'Less' means "where fragment's depth is less than the buffers current depth".
type DepthFunction = ComparisonFunction

-- | Indicates whether this color draw should use the 'Blending' setting given to the draw action. If this is 'False', the fragment's color value will simply replace the
--   target value.
type UseBlending = Bool

-- | Denotes how each fragment's color value should be blended with the target value.
data Blending
    = -- | The fragment's color will simply replace the target value.
        NoBlending
    | -- | The fragment's color will be blended using an equation and a set of factors for the RGB components, and a separate equation and set of factors for the Alpha component (if present), and a 'ConstantColor' that may be referenced from the 'BlendingFactors'. The 'ConstantColor' may be 'undefined' if none of the 'BlendingFactors' needs it.
        --   This kind of blending will only be made on colors with a 'Float' representation (e.g. 'RGB8' or 'RGB32F', but not 'RGB8I'), integer colors will simply replace the target value.
        BlendRgbAlpha (BlendEquation, BlendEquation) (BlendingFactors, BlendingFactors) ConstantColor
    | -- | A logical operation that will be done on the bits of the fragment color and the target color. This kind of blending is only done on colors that has a
        --   integral /internal/ representation (e.g. 'RGB8' or 'RGB8I', but not 'RGB32F'; note the difference with @BlendRgbAlpha@ restriction). For targets with an internal floating point representation, the fragment value will simply replace the target value.
        LogicOp LogicOp

type ConstantColor = V4 Float

-- | A set of blending factors used for the source (fragment) and the destination (target).
data BlendingFactors = BlendingFactors {blendFactorSrc :: BlendingFactor, blendFactorDst :: BlendingFactor}

-- | The equation used to combine the source (fragment) and the destination (target) after they have been multiplied with their respective 'BlendingFactor's.
data BlendEquation
    = FuncAdd
    | FuncSubtract
    | FuncReverseSubtract
    | Min
    | Max

-- | A factor that the source (fragment) or the destination (target) will be multiplied with before combined with the other in the 'BlendEquation'.
data BlendingFactor
    = Zero
    | One
    | SrcColor
    | OneMinusSrcColor
    | DstColor
    | OneMinusDstColor
    | SrcAlpha
    | OneMinusSrcAlpha
    | DstAlpha
    | OneMinusDstAlpha
    | ConstantColor
    | OneMinusConstantColor
    | ConstantAlpha
    | OneMinusConstantAlpha
    | SrcAlphaSaturate

usesConstantColor :: BlendingFactor -> Bool
usesConstantColor ConstantColor         = True
usesConstantColor OneMinusConstantColor = True
usesConstantColor ConstantAlpha         = True
usesConstantColor OneMinusConstantAlpha = True
usesConstantColor _                     = False

-- | A bitwise logical operation that will be used to combine colors that has an integral internal representation.
data LogicOp
    = Clear
    | And
    | AndReverse
    | Copy
    | AndInverted
    | Noop
    | Xor
    | Or
    | Nor
    | Equiv
    | Invert
    | OrReverse
    | CopyInverted
    | OrInverted
    | Nand
    | Set

-- | Denotes the operation that will be performed on the target's stencil value
data StencilOp
    = OpZero
    | OpKeep
    | OpReplace
    | OpIncr
    | OpIncrWrap
    | OpDecr
    | OpDecrWrap
    | OpInvert

-----------

-- | Fill a color image with a constant color value
clearImageColor :: forall c os. ColorRenderable c => Image (Format c) -> Color c (ColorElement c) -> Render os ()
clearImageColor i c = do
    (cwid, cd, doAsync) <- getLastRenderWin
    key <- Render $ lift $ lift $ lift $ getImageFBOKey i
    let fbokey = FBOKeys [key] Nothing Nothing
    mfbo <- Render $ lift $ lift $ lift $ getFBO cd fbokey
    case mfbo of
        Just fbo -> Render $ liftIO $ doAsync $ do
            fbo' <- readIORef fbo
            glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
        Nothing -> Render $ maybeThrow $ liftIO $ asSync doAsync $ do
            fbo' <- alloca (\ptr -> glGenFramebuffers 1 ptr >> peek ptr)
            fbo <- newIORef fbo'
            void $ mkWeakIORef fbo (doAsync $ with fbo' $ glDeleteFramebuffers 1)
            setFBO cd fbokey fbo
            glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
            glEnable GL_FRAMEBUFFER_SRGB
            getImageBinding i GL_COLOR_ATTACHMENT0
            withArray [GL_COLOR_ATTACHMENT0] $ glDrawBuffers 1
            getFboError

    Render $ liftIO $ doAsync $ do
        glDisable GL_SCISSOR_TEST
        glColorMask glTrue glTrue glTrue glTrue
        clearColor (undefined :: c) c
        glEnable GL_SCISSOR_TEST

-- | Fill a depth image with a constant depth value (in the range [0,1])
clearImageDepth :: DepthRenderable d => Image (Format d) -> Float -> Render os ()
clearImageDepth i d = do
    (cwid, cd, doAsync) <- getLastRenderWin
    key <- Render $ lift $ lift $ lift $ getImageFBOKey i
    let fbokey = FBOKeys [] (Just key) Nothing
    mfbo <- Render $ lift $ lift $ lift $ getFBO cd fbokey
    case mfbo of
        Just fbo -> Render $
            liftIO $
                doAsync $ do
                    fbo' <- readIORef fbo
                    glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
        Nothing -> Render $
            maybeThrow $
                liftIO $
                    asSync doAsync $ do
                        fbo' <- alloca (\ptr -> glGenFramebuffers 1 ptr >> peek ptr)
                        fbo <- newIORef fbo'
                        void $ mkWeakIORef fbo (doAsync $ with fbo' $ glDeleteFramebuffers 1)
                        setFBO cd fbokey fbo
                        glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
                        glEnable GL_FRAMEBUFFER_SRGB
                        getImageBinding i GL_DEPTH_ATTACHMENT
                        glDrawBuffers 0 nullPtr
                        getFboError
    Render $
        liftIO $
            doAsync $ do
                glDisable GL_SCISSOR_TEST
                glDepthMask glTrue
                with (realToFrac d) $ glClearBufferfv GL_DEPTH 0
                glEnable GL_SCISSOR_TEST

-- | Fill a depth image with a constant stencil value
clearImageStencil :: StencilRenderable s => Image (Format s) -> Int -> Render os ()
clearImageStencil i s = do
    (cwid, cd, doAsync) <- getLastRenderWin
    key <- Render $ lift $ lift $ lift $ getImageFBOKey i
    let fbokey = FBOKeys [] Nothing (Just key)
    mfbo <- Render $ lift $ lift $ lift $ getFBO cd fbokey
    case mfbo of
        Just fbo -> Render $
            liftIO $
                doAsync $ do
                    fbo' <- readIORef fbo
                    glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
        Nothing -> Render $
            maybeThrow $
                liftIO $
                    asSync doAsync $ do
                        fbo' <- alloca (\ptr -> glGenFramebuffers 1 ptr >> peek ptr)
                        fbo <- newIORef fbo'
                        void $ mkWeakIORef fbo (doAsync $ with fbo' $ glDeleteFramebuffers 1)
                        setFBO cd fbokey fbo
                        glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
                        glEnable GL_FRAMEBUFFER_SRGB
                        getImageBinding i GL_STENCIL_ATTACHMENT
                        glDrawBuffers 0 nullPtr
                        getFboError
    Render $
        liftIO $
            doAsync $ do
                glDisable GL_SCISSOR_TEST
                glStencilMask maxBound
                with (fromIntegral s) $ glClearBufferiv GL_STENCIL 0
                glEnable GL_SCISSOR_TEST

-- | Fill a combined depth stencil image with a constant depth value (in the range [0,1]) and a constant stencil value
clearImageDepthStencil :: Image (Format DepthStencil) -> Float -> Int -> Render os ()
clearImageDepthStencil i d s = do
    (cwid, cd, doAsync) <- getLastRenderWin
    key <- Render $ lift $ lift $ lift $ getImageFBOKey i
    let fbokey = FBOKeys [] Nothing (Just key)
    mfbo <- Render $ lift $ lift $ lift $ getFBO cd fbokey
    case mfbo of
        Just fbo -> Render $
            liftIO $
                doAsync $ do
                    fbo' <- readIORef fbo
                    glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
        Nothing -> Render $
            maybeThrow $
                liftIO $
                    asSync doAsync $ do
                        fbo' <- alloca (\ptr -> glGenFramebuffers 1 ptr >> peek ptr)
                        fbo <- newIORef fbo'
                        void $ mkWeakIORef fbo (doAsync $ with fbo' $ glDeleteFramebuffers 1)
                        setFBO cd fbokey fbo
                        glBindFramebuffer GL_DRAW_FRAMEBUFFER fbo'
                        glEnable GL_FRAMEBUFFER_SRGB
                        getImageBinding i GL_DEPTH_STENCIL_ATTACHMENT
                        glDrawBuffers 0 nullPtr
                        getFboError
    Render $
        liftIO $
            doAsync $ do
                glDisable GL_SCISSOR_TEST
                glDepthMask glTrue
                glStencilMask maxBound
                glClearBufferfi GL_DEPTH_STENCIL 0 (realToFrac d) (fromIntegral s)
                glEnable GL_SCISSOR_TEST

inWin :: Window os c ds -> IO () -> Render os ()
inWin w m = Render $ do
    rs <- lift $ lift StrictState.get
    case IMap.lookup (getWinName w) (perWindowRenderState rs) of
        Nothing           -> return () -- Window deleted, do nothing
        Just (_, doAsync) -> liftIO $ doAsync m

-- | Fill the window's back buffer with a constant color value
clearWindowColor :: forall os c ds. ContextColorFormat c => Window os c ds -> Color c Float -> Render os ()
clearWindowColor w c = inWin w $ do
    glBindFramebuffer GL_DRAW_FRAMEBUFFER 0
    glDisable GL_SCISSOR_TEST
    glColorMask glTrue glTrue glTrue glTrue
    withArray (map realToFrac (fromColor (undefined :: c) c ++ replicate 3 0 :: [Float])) $ glClearBufferfv GL_COLOR 0
    glEnable GL_SCISSOR_TEST

-- | Fill the window's back depth buffer with a constant depth value (in the range [0,1])
clearWindowDepth :: DepthRenderable ds => Window os c ds -> Float -> Render os ()
clearWindowDepth w d = inWin w $ do
    glBindFramebuffer GL_DRAW_FRAMEBUFFER 0
    glDisable GL_SCISSOR_TEST
    glDepthMask glTrue
    with (realToFrac d) $ glClearBufferfv GL_DEPTH 0
    glEnable GL_SCISSOR_TEST

-- | Fill the window's back stencil buffer with a constant stencil value
clearWindowStencil :: StencilRenderable ds => Window os c ds -> Int -> Render os ()
clearWindowStencil w s = inWin w $ do
    glBindFramebuffer GL_DRAW_FRAMEBUFFER 0
    glDisable GL_SCISSOR_TEST
    glStencilMask maxBound
    with (fromIntegral s) $ glClearBufferiv GL_STENCIL 0
    glEnable GL_SCISSOR_TEST

-- | Fill the window's back depth and stencil buffers with a constant depth value (in the range [0,1]) and a constant stencil value
clearWindowDepthStencil :: Window os c DepthStencil -> Float -> Int -> Render os ()
clearWindowDepthStencil w d s = inWin w $ do
    glBindFramebuffer GL_DRAW_FRAMEBUFFER 0
    glDisable GL_SCISSOR_TEST
    glDepthMask glTrue
    glStencilMask maxBound
    glClearBufferfi GL_DEPTH_STENCIL 0 (realToFrac d) (fromIntegral s)
    glEnable GL_SCISSOR_TEST

maybeThrow :: Monad m => ExceptT e m (Maybe e) -> ExceptT e m ()
maybeThrow = (>>= mapM_ throwE)

---------------
glTrue :: Num n => n
glTrue = fromBool True

getGlBlendEquation :: BlendEquation -> GLenum
getGlBlendEquation FuncAdd             = GL_FUNC_ADD
getGlBlendEquation FuncSubtract        = GL_FUNC_SUBTRACT
getGlBlendEquation FuncReverseSubtract = GL_FUNC_REVERSE_SUBTRACT
getGlBlendEquation Min                 = GL_MIN
getGlBlendEquation Max                 = GL_MAX

getGlBlendFunc :: BlendingFactor -> GLenum
getGlBlendFunc Zero                  = GL_ZERO
getGlBlendFunc One                   = GL_ONE
getGlBlendFunc SrcColor              = GL_SRC_COLOR
getGlBlendFunc OneMinusSrcColor      = GL_ONE_MINUS_SRC_COLOR
getGlBlendFunc DstColor              = GL_DST_COLOR
getGlBlendFunc OneMinusDstColor      = GL_ONE_MINUS_DST_COLOR
getGlBlendFunc SrcAlpha              = GL_SRC_ALPHA
getGlBlendFunc OneMinusSrcAlpha      = GL_ONE_MINUS_SRC_ALPHA
getGlBlendFunc DstAlpha              = GL_DST_ALPHA
getGlBlendFunc OneMinusDstAlpha      = GL_ONE_MINUS_DST_ALPHA
getGlBlendFunc ConstantColor         = GL_CONSTANT_COLOR
getGlBlendFunc OneMinusConstantColor = GL_ONE_MINUS_CONSTANT_COLOR
getGlBlendFunc ConstantAlpha         = GL_CONSTANT_ALPHA
getGlBlendFunc OneMinusConstantAlpha = GL_ONE_MINUS_CONSTANT_ALPHA
getGlBlendFunc SrcAlphaSaturate      = GL_SRC_ALPHA_SATURATE

getGlLogicOp :: LogicOp -> GLenum
getGlLogicOp Clear        = GL_CLEAR
getGlLogicOp And          = GL_AND
getGlLogicOp AndReverse   = GL_AND_REVERSE
getGlLogicOp Copy         = GL_COPY
getGlLogicOp AndInverted  = GL_AND_INVERTED
getGlLogicOp Noop         = GL_NOOP
getGlLogicOp Xor          = GL_XOR
getGlLogicOp Or           = GL_OR
getGlLogicOp Nor          = GL_NOR
getGlLogicOp Equiv        = GL_EQUIV
getGlLogicOp Invert       = GL_INVERT
getGlLogicOp OrReverse    = GL_OR_REVERSE
getGlLogicOp CopyInverted = GL_COPY_INVERTED
getGlLogicOp OrInverted   = GL_OR_INVERTED
getGlLogicOp Nand         = GL_NAND
getGlLogicOp Set          = GL_SET

getGlStencilOp :: StencilOp -> GLenum
getGlStencilOp OpZero     = GL_ZERO
getGlStencilOp OpKeep     = GL_KEEP
getGlStencilOp OpReplace  = GL_REPLACE
getGlStencilOp OpIncr     = GL_INCR
getGlStencilOp OpIncrWrap = GL_INCR_WRAP
getGlStencilOp OpDecr     = GL_DECR
getGlStencilOp OpDecrWrap = GL_DECR_WRAP
getGlStencilOp OpInvert   = GL_INVERT