module Renderer where

import SDL (($=))

import qualified Graphics.Rendering.OpenGL as GL

import qualified Data.ByteString as BS

import Foreign

-- internal imports

import Types

initSpriteRenderObjects = do
  quadVAO <- GL.genObjectName
  quadVBO <- GL.genObjectName

  GL.bindBuffer GL.ArrayBuffer $= Just quadVBO
  withArray rawVertices $ \ptr ->
    GL.bufferData GL.ArrayBuffer $=
      ( fromIntegral $ length rawVertices * sizeOf (0 :: Float)
      , ptr
      , GL.StaticDraw
      )

  GL.bindVertexArrayObject $= Just quadVAO

  GL.vertexAttribArray (GL.AttribLocation 0) $= GL.Enabled

  GL.vertexAttribPointer (GL.AttribLocation 0) $=
    ( GL.ToFloat
    , GL.VertexArrayDescriptor 4 GL.Float 0 (plusPtr nullPtr 0)
    )

  GL.bindBuffer GL.ArrayBuffer $= Nothing
  GL.bindVertexArrayObject $= Nothing

  return (RenderObjects quadVAO quadVBO)
  where
    rawVertices :: [Float]
    rawVertices =
      [ 0, 1, 0, 0
      , 1, 0, 1, 0
      , 0, 0, 0, 0
    
      , 0, 1, 0, 1
      , 1, 1, 1, 1
      , 1, 0, 1, 0
      ]

initSpriteShaderObjects = do
  vertexShaderSrc <- BS.readFile "shader/vertex.sl"
  fragmentShaderSrc <- BS.readFile "shader/fragment.sl"

  vertexShader <- GL.createShader Gl.VertexShader
  fragmentShader <- GL.createShader Gl.FragmentShader

  GL.shaderSourceBS vertexShader $= vertexShaderSrc
  GL.ShaderSourceBS fragmentShader $= fragmentShaderSrc

  GL.compileShader vertexShader
  GL.compileShader fragmentShader

  shaderProgram <- GL.createProgram

  GL.attachShader shaderProgram vertexShader
  GL.attachShader shaderProgram fragmentShader

  GL.linkProgram shaderProgram

  return (SpriteShaderObjects vertexShader fragmentShader shaderProgram)

loadSprites :: IO (AssetDetails SpriteRenderObjects SpriteShaderObjects Sprite)
loadSprites = do
  rawImg <- readImage "assets/img/lynx.jpg"
  let img = case eRawImg of
    Left err -> error err
    Right dynImg -> convertRGBA8 dynImg

  vertObj <- initSpriteRenderObjects
  shadObj <- initSpriteShaderobjects

  return AssetDetails
    { adVertObj = vertObj
    , adShadObj = shadObj
    , adDataObj = M.singleton "lynx" (Sprite (V2 0 0) img)
    }