{-# LANGUAGE Rank2Types #-}
module Test.Common where

import Control.Monad.Exception (MonadException)
import Control.Monad.IO.Class (MonadIO)
import Data.Traversable (forM)

import Graphics.GPipe

xAxis :: [(V3 Float, V3 Float)]
xAxis = zip (repeat $ V3 1 0 0) -- red
    [V3 (-1) 0 0, V3 1 0 0, V3 0.8 (-0.1) 0, V3 0.8 0 0, V3 1 (-0.1) 0]

yAxis :: [(V3 Float, V3 Float)]
yAxis = zip (repeat $ V3 0 1 0) -- green
    [V3 0 (-1) 0, V3 0 1 0, V3 0 0.8 (-0.1), V3 0 0.9 (-0.05), V3 0 1 (-0.1)]

zAxis :: [(V3 Float, V3 Float)]
zAxis = zip (repeat $ V3 0 0 1) -- blue
    [V3 0 0 (-1), V3 0 0 1, V3 (-0.1) 0 0.8, V3 (-0.1) 0 1]

plane :: [(V3 Float, V3 Float)]
plane = zip (repeat $ V3 1 1 1) -- white
    [V3 (-2) (-0.1) (-2), V3 (-2) (-0.1) 2, V3 2 (-0.1) 2, V3 2 (-0.1) (-2), V3 (-2) (-0.1) (-2)]

-- TODO: make tests
--   * basic
--   * split-thread load/render
--   * render multiple windows

data ShaderEnv os = ShaderEnv
    { extractProjU :: (Buffer os (Uniform (V4 (B4 Float))), Int)
    , extractLinePA :: PrimitiveArray Lines (B3 Float, B3 Float)
    , extractRastOpts :: (Side, ViewPort, DepthRange)
    }

initBuffers
    :: MonadIO m
    => [[(V3 Float, V3 Float)]]
    -> ContextT w os f m ([Buffer os (B3 Float, B3 Float)], Buffer os (Uniform (V4 (B4 Float))))
initBuffers rawMeshes = do
    -- make mesh buffers
    meshesB <- forM rawMeshes $ \pts -> do
        buf <- newBuffer $ length pts
        writeBuffer buf 0 pts
        return buf
    -- make projection matrix buffer
    projMatB <- newBuffer 1
    return (meshesB, projMatB)

projectLines :: forall os f. Shader os f (ShaderEnv os) (FragmentStream (V3 FFloat, FFloat))
projectLines = do
    projMat <- getUniform extractProjU
    linePS <- toPrimitiveStream extractLinePA
    -- project points
    let projectedLinePS = (\(c, p) -> (projMat !* point p, c)) <$> linePS
    lineFS <- rasterize extractRastOpts projectedLinePS
    -- write fragment depths and return frags
    return $ withRasterizedInfo (\fr inf -> (fr, depth inf)) lineFS
    where
        depth RasterizedInfo {rasterizedFragCoord = (V4 _ _ z _)} = z

-- TODO: just adds the draw call to the end of the shader & glues some init functions together
initRenderContext
    :: (MonadIO m, MonadException m)
    => [[(V3 Float, V3 Float)]]
    -> ContextT w os (ContextFormat RGBFloat Depth) m
        ( [Buffer os (B3 Float, B3 Float)]
        , Buffer os (Uniform (V4 (B4 Float)))
        , CompiledShader os (ContextFormat RGBFloat Depth) (ShaderEnv os)
        )
initRenderContext rawMeshes = do
    projShader <- compileShader (projectLines >>= drawContextColorDepth (const (ContextColorOption NoBlending $ pure True, DepthOption Less True)))
    (meshesB, projMatB) <- initBuffers rawMeshes
    return (meshesB, projMatB, projShader)

computeProjMat :: Float -> V2 Int -> M44 Float
computeProjMat frac (V2 w h) = camera2clip !*! world2camera !*! model2world
    where
        t = frac * 2 * pi
        model2world = identity
        world2camera = lookAt
            -- eye: camera position in world coordinates
            (V3 (3 * sin t) (0.5 + cos (t * 2)) (3 * cos t))
            (V3 0 0.1 0) -- center: camera look-at target position in world coords
            (V3 0 1 0) -- up: camera up-vector
        camera2clip = perspective
            (pi / 3) -- 60deg field of view "in y direction"
            (fromIntegral w / fromIntegral h) -- aspect ratio
            1 100 -- near and far clipping plane

basicRenderer
    :: V2 Int
    -> ( [Buffer os (B3 Float, B3 Float)]
       , Buffer os (Uniform (V4 (B4 Float)))
       , CompiledShader os (ContextFormat RGBFloat Depth) (ShaderEnv os)
       )
    -> Render os (ContextFormat RGBFloat Depth) ()
basicRenderer size (meshesB, projMatB, projShader) = do
    clearContextColor 0.2 -- grey
    clearContextDepth 1 -- far plane
    meshPAs <- forM meshesB $ \mesh -> do
        meshVA <- newVertexArray mesh
        return $ toPrimitiveArray LineStrip meshVA
    projShader $ ShaderEnv (projMatB, 0) (mconcat meshPAs) (Front, ViewPort 0 size, DepthRange 0 1)

mainloop
    ::  (MonadIO m, MonadException m)
    => (Int, Int)
    -> ( [Buffer os (B3 Float, B3 Float)]
       , Buffer os (Uniform (V4 (B4 Float)))
       , CompiledShader os (ContextFormat RGBFloat Depth) (ShaderEnv os)
       )
    -> ContextT w os (ContextFormat RGBFloat Depth) m ()
mainloop frame resources@(_, projMatB, _)
    | done frame = return ()
    | otherwise = do
        -- compute a projection matrix & write it to the buffer
        size <- getContextBuffersSize
        writeBuffer projMatB 0 [computeProjMat (frac frame) size]
        -- render the scene and then loop
        render $ basicRenderer size resources
        swapContextBuffers
        mainloop (next frame) resources
    where
        done (maxFrame, curFrame) = curFrame > maxFrame
        frac (maxFrame, curFrame) = fromIntegral curFrame / fromIntegral maxFrame
        next = fmap (+1)