    {-# LANGUAGE ConstraintKinds #-}
    {-# LANGUAGE DeriveDataTypeable    #-}
    {-# LANGUAGE EmptyDataDecls        #-}
    {-# LANGUAGE FlexibleContexts      #-}
    {-# LANGUAGE GADTs                 #-}
    {-# LANGUAGE MultiParamTypeClasses #-}
    {-# LANGUAGE TypeFamilies          #-}
    {-# LANGUAGE UndecidableInstances  #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Diagrams.TwoD.Image
    -- Copyright   :  (c) 2011 diagrams-lib team (see LICENSE)
    -- License     :  BSD-style (see LICENSE)
    -- Maintainer  :  diagrams-discuss@googlegroups.com
    --
    -- Importing external images into diagrams.  Usage example: To create
    -- a diagram from an embedded image with width 1 and height set
    -- according to the aspect ratio, use @image img # scaleUToX 1@, where
    -- @img@ is a value of type @DImage n e@, created with a function like
    -- 'loadImageEmb', 'loadImageExt', or 'raster'.
    -----------------------------------------------------------------------------

    module Diagrams.TwoD.Image
        (
          DImage(..), ImageData(..)
        , Embedded, External, Native
        , image
        , embeddedImage
        , loadImageEmb
        , loadImageEmbBS
        , loadImageExt
        , uncheckedImageRef
        , raster
        , rasterDia
        ) where

    import           Codec.Picture
    import           Codec.Picture.Types  (dynamicMap)

    import           Data.Colour          (AlphaColour)
    import           Data.Semigroup
    import           Data.Typeable        (Typeable)

    import           Diagrams.Core

    import           Diagrams.Attributes  (colorToSRGBA)
    import           Diagrams.TwoD.Path   (isInsideEvenOdd)
    import           Diagrams.Path        (Path)
    import           Diagrams.TwoD.Shapes (rect)
    import Diagrams.Query
    import           Diagrams.TwoD.Types

    import           Data.ByteString

    import           Linear.Affine

    data Embedded deriving Typeable
    data External deriving Typeable
    data Native (t :: *) deriving Typeable

    -- | 'ImageData' is either a JuicyPixels @DynamicImage@ tagged as 'Embedded' or
    --   a reference tagged as 'External'. Additionally 'Native' is provided for
    --   external libraries to hook into.
    data ImageData :: * -> * where
      ImageRaster :: DynamicImage -> ImageData Embedded
      ImageRef    :: FilePath -> ImageData External
      ImageNative :: t -> ImageData (Native t)

    -------------------------------------------------------------------------------
    -- | An image primitive, the two ints are width followed by height.
    --   Will typically be created by @loadImageEmb@ or @loadImageExt@ which,
    --   will handle setting the width and height to the actual width and height
    --   of the image.
    data DImage :: * -> * -> * where
      DImage :: ImageData t -> Int -> Int -> Transformation V2 n -> DImage n t
      deriving Typeable

    type instance V (DImage n a) = V2
    type instance N (DImage n a) = n

    instance RealFloat n => HasQuery (DImage n a) Any where
      getQuery (DImage _ w h _) = -- transform t $
        Query $ \p -> Any (isInsideEvenOdd r p)
        where
        r = rectPath (fromIntegral w) (fromIntegral h)

    instance Fractional n => Transformable (DImage n a) where
      transform t1 (DImage iD w h t2) = DImage iD w h (t1 <> t2)

    instance Fractional n => HasOrigin (DImage n a) where
      moveOriginTo p = translate (origin .-. p)

    -- | Make a 'DImage' into a 'Diagram'.
    image :: (TypeableFloat n, Typeable a, Renderable (DImage n a) b)
          => DImage n a -> QDiagram b V2 n Any
    image img
      = mkQD (Prim img)
             (getEnvelope r)
             (getTrace r)
             mempty
             (Query $ \p -> Any (isInsideEvenOdd r p))
      where
        r = rectPath (fromIntegral w) (fromIntegral h)
        -- should we use the transform here?
        DImage _ w h _ = img

    rectPath :: RealFloat n => n -> n -> Path V2 n
    rectPath = rect

    -- | Read a JuicyPixels @DynamicImage@ and wrap it in a 'DImage'.
    --   The width and height of the image are set to their actual values.
    embeddedImage :: Num n => DynamicImage -> DImage n Embedded
    embeddedImage img = DImage (ImageRaster img) w h mempty
      where
        w = dynamicMap imageWidth img
        h = dynamicMap imageHeight img

    -- | Use JuicyPixels to read a file in any format and wrap it in a 'DImage'.
    --   The width and height of the image are set to their actual values.
    loadImageEmb :: Num n => FilePath -> IO (Either String (DImage n Embedded))
    loadImageEmb path = fmap embeddedImage `fmap` readImage path

    -- | A pure variant of 'loadImageEmb'
    loadImageEmbBS :: Num n => ByteString -> Either String (DImage n Embedded)
    loadImageEmbBS bs = embeddedImage `fmap` decodeImage bs

    -- | Check that a file exists, and use JuicyPixels to figure out
    --   the right size, but save a reference to the image instead
    --   of the raster data
    loadImageExt :: Num n => FilePath -> IO (Either String (DImage n External))
    loadImageExt path = do
      dImg <- readImage path
      return $ case dImg of
        Left msg  -> Left msg
        Right img -> Right $ DImage (ImageRef path) w h mempty
          where
            w = dynamicMap imageWidth img
            h = dynamicMap imageHeight img

    -- | Make an "unchecked" image reference; have to specify a
    --   width and height. Unless the aspect ratio of the external
    --   image is the w :: h, then the image will be distorted.
    uncheckedImageRef :: Num n => FilePath -> Int -> Int -> DImage n External
    uncheckedImageRef path w h = DImage (ImageRef path) w h mempty

    -- | Crate a diagram from raw raster data.
    rasterDia :: (TypeableFloat n, Renderable (DImage n Embedded) b)
              => (Int -> Int -> AlphaColour Double) -> Int -> Int -> QDiagram b V2 n Any
    rasterDia f w h = image $ raster f w h

    -- | Create an image "from scratch" by specifying the pixel data
    raster :: Num n => (Int -> Int -> AlphaColour Double) -> Int -> Int -> DImage n Embedded
    raster f w h = DImage (ImageRaster (ImageRGBA8 img)) w h mempty
      where
        img = generateImage g w h
        g x y = fromAlphaColour $ f x y

    fromAlphaColour :: AlphaColour Double -> PixelRGBA8
    fromAlphaColour c = PixelRGBA8 r g b a
      where
        (r, g, b, a) = (int r', int g', int b', int a')
        (r', g', b', a') = colorToSRGBA c
        int x = round (255 * x)

    instance Fractional n => (Renderable (DImage n a) NullBackend) where
      render _ _ = mempty