{-# LANGUAGE OverloadedStrings #-}
module Graphics.Rendering.Rect.Image(
    Atlas, buildAtlas, Texture(..), atlasLookup) where

import qualified Data.HashMap.Lazy as HM
import Data.Text (Text)
import Codec.Picture (DynamicImage(..), Image(..), PixelRGBA8(..), PixelYCbCr8(..),
                        pixelMap, generateImage)
import Codec.Picture.Types (promoteImage, dynamicMap)

import Control.Monad.IO.Class (MonadIO(..))
import Control.Monad (forM)
import Data.Maybe (fromMaybe)

import Typograffiti.GL
import Graphics.GL.Core32
import Graphics.GL.Types
import Graphics.GL.Ext.EXT.Cmyka
import Graphics.GL.Ext.SGIX.Ycrcb
import Graphics.GL.Compatibility32

import Data.Vector.Storable (unsafeWith, unsafeCast, Vector)
import Foreign.Ptr (castPtr)
import Foreign.Marshal.Array (allocaArray, peekArray)

data Atlas = Atlas { unAtlas :: HM.HashMap Text GLuint }

buildAtlas :: MonadIO m => (Text -> IO DynamicImage) -> [Text] -> m Atlas
buildAtlas cb [] = return $ Atlas HM.empty
buildAtlas cb srcs = do
    -- TODO Merge textures into an actual atlas.
    let len = length srcs
    textures <- liftIO $ allocaArray (toEnum len) $ \ptr -> do
        glGenTextures (toEnum len) ptr
        peekArray len ptr
    imgs <- liftIO $ forM srcs cb

    forM (zip textures imgs) $ \(texture, dyn) -> do
        -- NOTE: `unsafe` crashes with a divide-by-zero given a `Vector ()`
        let img = dynamicMap (unsafeCast . imageData) $ adjustGL dyn :: Vector Word
        let (format, word) = glFormat dyn
        liftIO $ glBindTexture GL_TEXTURE_2D texture
        liftIO $ unsafeWith img $ -- FIXME: Crashes
            glTexImage2D GL_TEXTURE_2D 0 GL_RGBA
                    (toEnum $ dynamicMap imageWidth dyn)
                    (toEnum $ dynamicMap imageHeight dyn)
                    0 format word . castPtr
        liftIO $ glTexParameteri GL_TEXTURE_2D GL_TEXTURE_MIN_FILTER GL_LINEAR
        liftIO $ glTexParameteri GL_TEXTURE_2D GL_TEXTURE_MAG_FILTER GL_LINEAR
        liftIO $ glTexParameteri GL_TEXTURE_2D GL_TEXTURE_WRAP_S GL_REPEAT
        liftIO $ glTexParameteri GL_TEXTURE_2D GL_TEXTURE_WRAP_T GL_REPEAT

    return $ Atlas $ HM.fromList $ zip srcs textures

data Texture = Texture GLuint
atlasLookup :: Text -> Atlas -> Texture
atlasLookup key = Texture . fromMaybe 0 . HM.lookup key . unAtlas

-- OpenGL deals in CrCb not CbCr...
adjustGL (ImageYCbCr8 img) = ImageYCbCr8 $ pixelMap swapCrCb img
  where swapCrCb (PixelYCbCr8 y cb cr) = PixelYCbCr8 y cr cb
adjustGL img = img
glFormat (ImageY8 _) = (GL_LUMINANCE, GL_UNSIGNED_BYTE)
glFormat (ImageY16 _) = (GL_LUMINANCE, GL_UNSIGNED_SHORT)
glFormat (ImageY32 _) = (GL_LUMINANCE, GL_UNSIGNED_INT)
glFormat (ImageYF _) = (GL_LUMINANCE, GL_FLOAT)
glFormat (ImageYA8 _) = (GL_LUMINANCE_ALPHA, GL_BYTE)
glFormat (ImageYA16 _) = (GL_LUMINANCE_ALPHA, GL_UNSIGNED_SHORT)
glFormat (ImageRGB8 _) = (GL_RGB, GL_UNSIGNED_BYTE)
glFormat (ImageRGB16 _) = (GL_RGB, GL_UNSIGNED_SHORT)
glFormat (ImageRGBF _) = (GL_RGB, GL_FLOAT)
glFormat (ImageRGBA8 _) = (GL_RGBA, GL_UNSIGNED_BYTE)
glFormat (ImageRGBA16 _) = (GL_RGBA, GL_UNSIGNED_BYTE)
glFormat (ImageYCbCr8 _) = (GL_YCRCB_444_SGIX, GL_UNSIGNED_BYTE)
glFormat (ImageCMYK8 _) = (GL_CMYK_EXT, GL_UNSIGNED_BYTE)
glFormat (ImageCMYK16 _) = (GL_CMYK_EXT, GL_UNSIGNED_SHORT)