{-# LANGUAGE ScopedTypeVariables #-}

{-| A convenience function for rendering any of the graphs implemented in this package to a standalone window.

Example usage:

> import Control.Monad
> import Control.Monad.Trans.Either
> import Control.Concurrent
> import Pipes
> import qualified Pipes.Prelude as P
> import System.Random
> import Graphics.Rendering.OpenGL
> 
> import Graphics.DynamicGraph.Waterfall
> import Graphics.DynamicGraph.Window
> 
> randomVect :: Producer [GLfloat] IO ()
> randomVect =  P.repeatM $ do
>     res <- replicateM 1000 randomIO
>     threadDelay 10000
>     return res
> 
> main = eitherT putStrLn return $ do
>     res <- lift setupGLFW
>     unless res (left "Unable to initilize GLFW")
>
>     waterfall <- window 1024 480 $ renderWaterfall 1000 1000 jet_mod
> 
>     lift $ runEffect $ randomVect >-> waterfall

-}
module Graphics.DynamicGraph.Window (
    window,
    module Graphics.DynamicGraph.Util
    ) where

import Control.Monad.Trans.Either
import Control.Concurrent hiding (yield)
import Control.Concurrent.MVar
import Data.IORef
import Control.Monad

import Graphics.UI.GLFW as G
import Graphics.GLUtil
import Graphics.Rendering.OpenGL
import Pipes

import Graphics.DynamicGraph.Util

{-| A convenience function for rendering any of the graphs implemented in this package to a standalone window.
    
    Creates the window before returning.

    Returns either an error message or a consumer that draws to the window.
-}
window :: IsPixelData a 
       => Int                                  -- ^ Window width
       -> Int                                  -- ^ Window height
       -> IO (Consumer a IO ())                -- ^ The Consumer that draws on the window. Obtain this from one of the other modules in this package. Must be given in an IO monad so that it can be initialised with the OpenGL context created within this function.
       -> EitherT String IO (Consumer a IO ()) 
window width height renderPipe = do
    mv :: MVar a <- lift newEmptyMVar
    completion <- lift newEmptyMVar

    closed <- lift $ newIORef False

    lift $ forkOS $ void $ do
        res <- runEitherT $ do
            res' <- lift $ createWindow width height "" Nothing Nothing
            win <- maybe (left "error creating window") return res'
            lift $ setWindowSizeCallback win $ Just $ \win x y -> 
                viewport $= (Position 0 0, Size (fromIntegral x) (fromIntegral y))
            lift $ setWindowCloseCallback win $ Just $ \win -> writeIORef closed True
            lift $ makeContextCurrent (Just win)
            lift $ clearColor $= Color4 0 0 0 0

            renderPipe <- lift renderPipe

            let thePipe = forever $ do 
                    lift pollEvents
                    dat <- lift $ takeMVar mv
                    lift $ makeContextCurrent (Just win)
                    lift pollEvents
                    lift $ clear [ColorBuffer]
                    yield dat
                    lift $ swapBuffers win
            return $ runEffect $ thePipe >-> renderPipe

        case res of
            Left  err        -> replaceMVar completion $ left err
            Right renderLoop -> do
                replaceMVar completion $ right ()
                renderLoop

    join $ lift $ takeMVar completion

    return $ 
        let pipe = do
                c <- lift $ readIORef closed
                unless c $ do
                    x <- await
                    lift $ replaceMVar mv x
                    pipe
        in pipe