    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GL.Texturing.Parameters
    -- Copyright   :  (c) Sven Panne 2002-2006
    -- License     :  BSD-style (see the file libraries/OpenGL/LICENSE)
    --
    -- Maintainer  :  sven.panne@aedion.de
    -- Stability   :  stable
    -- Portability :  portable
    --
    -- This module corresponds to section 3.8.4 (Texture Parameters), section 3.8.7
    -- (Texture Wrap Mode), section 3.8.8 (Texture Minification), and section 3.8.9
    -- (Texture Magnification) of the OpenGL 2.1 specs.
    --
    --------------------------------------------------------------------------------

    module Graphics.Rendering.OpenGL.GL.Texturing.Parameters (
       TextureFilter(..), MinificationFilter, MagnificationFilter, textureFilter,
       Repetition(..), Clamping(..), textureWrapMode,
       textureBorderColor, LOD, textureObjectLODBias, maxTextureLODBias,
       textureLODRange, textureMaxAnisotropy, maxTextureMaxAnisotropy,
       textureLevelRange, generateMipmap, depthTextureMode, textureCompareMode,
       textureCompareFailValue, TextureCompareOperator(..), textureCompareOperator
    ) where

    import Graphics.Rendering.OpenGL.GL.BasicTypes (
       GLint, GLfloat, GLclampf, Capability(..) )
    import Graphics.Rendering.OpenGL.GL.Capability (
       marshalCapability, unmarshalCapability )
    import Graphics.Rendering.OpenGL.GL.ComparisonFunction (
       marshalComparisonFunction, unmarshalComparisonFunction )
    import Graphics.Rendering.OpenGL.GL.CoordTrans ( TextureCoordName(..) )
    import Graphics.Rendering.OpenGL.GL.PerFragment ( ComparisonFunction )
    import Graphics.Rendering.OpenGL.GL.PixelRectangles (
       PixelInternalFormat(..) )
    import Graphics.Rendering.OpenGL.GL.QueryUtils (
       GetPName(GetMaxTextureMaxAnisotropy,GetMaxTextureLODBias), getFloat1)
    import Graphics.Rendering.OpenGL.GL.StateVar (
       GettableStateVar, makeGettableStateVar,
       StateVar, makeStateVar )
    import Graphics.Rendering.OpenGL.GL.Texturing.Specification (
       Level, TextureTarget(..) )
    import Graphics.Rendering.OpenGL.GL.Texturing.TexParameter (
       TexParameter(TextureMinFilter,TextureMagFilter,TextureWrapS,TextureWrapT,
                    TextureWrapR,TextureBorderColor,TextureMinLOD,TextureMaxLOD,
                    TextureBaseLevel,TextureMaxLevel,TextureMaxAnisotropy,
                    TextureLODBias,GenerateMipmap,DepthTextureMode,
                    TextureCompareMode,TextureCompareFunc,TextureCompareFailValue,
                    TextureCompare,TextureCompareOperator),
       texParami, texParamf, texParamC4f, combineTexParams, combineTexParamsMaybe )
    import Graphics.Rendering.OpenGL.GL.Texturing.PixelInternalFormat (
       marshalPixelInternalFormat, unmarshalPixelInternalFormat )
    import Graphics.Rendering.OpenGL.GL.VertexSpec( Color4(..) )
    import Graphics.Rendering.OpenGL.GLU.ErrorsInternal ( recordInvalidEnum )

    --------------------------------------------------------------------------------

    data TextureFilter =
         Nearest
       | Linear'
       deriving ( Eq, Ord, Show )

    type MinificationFilter = (TextureFilter, Maybe TextureFilter)

    type MagnificationFilter = TextureFilter

    -- We treat MagnificationFilter as a degenerated case of MinificationFilter
    magToMin :: MagnificationFilter -> MinificationFilter
    magToMin magFilter = (magFilter, Nothing)

    minToMag :: MinificationFilter -> MagnificationFilter
    minToMag (magFilter, Nothing) = magFilter
    minToMag minFilter = error ("minToMag: illegal value " ++ show minFilter)

    marshalMinificationFilter :: MinificationFilter -> GLint
    marshalMinificationFilter x = case x of
       (Nearest, Nothing     ) -> 0x2600
       (Linear', Nothing     ) -> 0x2601
       (Nearest, Just Nearest) -> 0x2700
       (Linear', Just Nearest) -> 0x2701
       (Nearest, Just Linear') -> 0x2702
       (Linear', Just Linear') -> 0x2703

    marshalMagnificationFilter :: MagnificationFilter -> GLint
    marshalMagnificationFilter = marshalMinificationFilter . magToMin

    unmarshalMinificationFilter :: GLint -> MinificationFilter
    unmarshalMinificationFilter x
       | x ==  0x2600 = (Nearest, Nothing     )
       | x ==  0x2601 = (Linear', Nothing     )
       | x ==  0x2700 = (Nearest, Just Nearest)
       | x ==  0x2701 = (Linear', Just Nearest)
       | x ==  0x2702 = (Nearest, Just Linear')
       | x ==  0x2703 = (Linear', Just Linear')
       | otherwise = error ("unmarshalMinificationFilter: illegal value " ++ show x)

    unmarshalMagnificationFilter :: GLint -> MagnificationFilter
    unmarshalMagnificationFilter = minToMag . unmarshalMinificationFilter

    --------------------------------------------------------------------------------

    textureFilter :: TextureTarget -> StateVar (MinificationFilter, MagnificationFilter)
    textureFilter =
       combineTexParams
          (texParami unmarshalMinificationFilter  marshalMinificationFilter  TextureMinFilter)
          (texParami unmarshalMagnificationFilter marshalMagnificationFilter TextureMagFilter)

    --------------------------------------------------------------------------------

    data Repetition =
         Repeated
       | Mirrored
       deriving ( Eq, Ord, Show )

    data Clamping =
         Clamp
       | Repeat
       | ClampToEdge
       | ClampToBorder
       deriving ( Eq, Ord, Show )

    marshalTextureWrapMode :: (Repetition, Clamping) -> GLint
    marshalTextureWrapMode x = case x of
       (Repeated, Clamp) -> 0x2900
       (Repeated, Repeat) -> 0x2901
       (Repeated, ClampToEdge) -> 0x812f
       (Repeated, ClampToBorder) -> 0x812d
       (Mirrored, Clamp) -> 0x8742
       (Mirrored, Repeat) -> 0x8370
       (Mirrored, ClampToEdge) -> 0x8743
       (Mirrored, ClampToBorder) -> 0x8912

    unmarshalTextureWrapMode :: GLint -> (Repetition, Clamping)
    unmarshalTextureWrapMode x
       | x == 0x2900 = (Repeated, Clamp)
       | x == 0x2901 = (Repeated, Repeat)
       | x == 0x812f = (Repeated, ClampToEdge)
       | x == 0x812d = (Repeated, ClampToBorder)
       | x == 0x8742 = (Mirrored, Clamp)
       | x == 0x8370 = (Mirrored, Repeat)
       | x == 0x8743 = (Mirrored, ClampToEdge)
       | x == 0x8912 = (Mirrored, ClampToBorder)
       | otherwise = error ("unmarshalTextureWrapMode: illegal value " ++ show x)

    --------------------------------------------------------------------------------

    textureWrapMode :: TextureTarget -> TextureCoordName -> StateVar (Repetition,Clamping)
    textureWrapMode t coord = case coord of
       S -> wrap TextureWrapS
       T -> wrap TextureWrapT
       R -> wrap TextureWrapR
       Q -> invalidTextureCoord
       where wrap c = texParami unmarshalTextureWrapMode marshalTextureWrapMode c t

    invalidTextureCoord :: StateVar (Repetition,Clamping)
    invalidTextureCoord =
       makeStateVar
          (do recordInvalidEnum; return (Repeated, Repeat))
          (const recordInvalidEnum)

    --------------------------------------------------------------------------------

    textureBorderColor :: TextureTarget -> StateVar (Color4 GLfloat)
    textureBorderColor = texParamC4f TextureBorderColor

    --------------------------------------------------------------------------------

    type LOD = GLfloat

    textureObjectLODBias :: TextureTarget -> StateVar LOD
    textureObjectLODBias = texParamf id id TextureLODBias

    maxTextureLODBias :: GettableStateVar LOD
    maxTextureLODBias =
       makeGettableStateVar (getFloat1 id GetMaxTextureLODBias)

    textureLODRange :: TextureTarget -> StateVar (LOD,LOD)
    textureLODRange =
       combineTexParams
          (texParamf id id TextureMinLOD)
          (texParamf id id TextureMaxLOD)

    --------------------------------------------------------------------------------

    textureMaxAnisotropy :: TextureTarget -> StateVar GLfloat
    textureMaxAnisotropy = texParamf id id TextureMaxAnisotropy

    maxTextureMaxAnisotropy :: GettableStateVar GLfloat
    maxTextureMaxAnisotropy =
       makeGettableStateVar (getFloat1 id GetMaxTextureMaxAnisotropy)

    --------------------------------------------------------------------------------

    textureLevelRange :: TextureTarget -> StateVar (Level,Level)
    textureLevelRange =
       combineTexParams
          (texParami id id TextureBaseLevel)
          (texParami id id TextureMaxLevel)

    --------------------------------------------------------------------------------

    generateMipmap :: TextureTarget -> StateVar Capability
    generateMipmap = texParami unmarshal marshal GenerateMipmap
       where unmarshal = unmarshalCapability . fromIntegral
             marshal = fromIntegral . marshalCapability

    --------------------------------------------------------------------------------

    -- Only Luminance', Intensity, and Alpha' allowed
    depthTextureMode :: TextureTarget -> StateVar PixelInternalFormat
    depthTextureMode =
       texParami unmarshalPixelInternalFormat marshalPixelInternalFormat DepthTextureMode

    --------------------------------------------------------------------------------

    marshalTextureCompareMode :: Capability -> GLint
    marshalTextureCompareMode x = case x of
       Disabled -> 0x0     -- i.e. None
       Enabled -> 0x884e   -- i.e. CompareRToTexture

    unmarshalTextureCompareMode :: GLint -> Capability
    unmarshalTextureCompareMode x
       | x == 0x0 = Disabled
       | x == 0x884e = Enabled
       | otherwise = error ("unmarshalTextureCompareMode: illegal value " ++ show x)

    --------------------------------------------------------------------------------

    textureCompareMode :: TextureTarget -> StateVar (Maybe ComparisonFunction)
    textureCompareMode =
       combineTexParamsMaybe
          (texParami unmarshalTextureCompareMode marshalTextureCompareMode TextureCompareMode)
          (texParami unmarshal marshal TextureCompareFunc)
       where unmarshal = unmarshalComparisonFunction . fromIntegral
             marshal = fromIntegral . marshalComparisonFunction

    --------------------------------------------------------------------------------

    textureCompareFailValue :: TextureTarget -> StateVar GLclampf
    textureCompareFailValue = texParamf id id TextureCompareFailValue

    --------------------------------------------------------------------------------

    data TextureCompareOperator =
         LequalR
       | GequalR
       deriving ( Eq, Ord, Show )

    marshalTextureCompareOperator :: TextureCompareOperator -> GLint
    marshalTextureCompareOperator x = case x of
       LequalR -> 0x819c
       GequalR -> 0x819d

    unmarshalTextureCompareOperator :: GLint -> TextureCompareOperator
    unmarshalTextureCompareOperator x
       | x == 0x819c = LequalR
       | x == 0x819d = GequalR
       | otherwise = error ("unmarshalTextureCompareOperator: illegal value " ++ show x)

    --------------------------------------------------------------------------------

    textureCompareOperator :: TextureTarget -> StateVar (Maybe TextureCompareOperator)
    textureCompareOperator =
       combineTexParamsMaybe
          (texParami (unmarshalCapability . fromIntegral) (fromIntegral. marshalCapability) TextureCompare)
          (texParami unmarshalTextureCompareOperator marshalTextureCompareOperator TextureCompareOperator)