{-# LANGUAGE PatternGuards, GeneralizedNewtypeDeriving #-}

import Game
import Level
import Render
import Tank

import GLDriver
import GLX

import Control.Concurrent (threadDelay)
import Control.Monad.State
import Data.Maybe
import Data.Time.Clock


data MainState = MainState
               { driver   :: !SomeDriver
               , time     :: !UTCTime
               }

newtype MainT m a = MainT (StateT MainState m a)
    deriving (Monad, MonadState MainState, MonadIO, MonadTrans)

type Main = MainT Game

runMain :: MainState -> Main a -> Game (a, MainState)
runMain st (MainT a) = runStateT a st


main :: IO ()
main = do
  gl <- initGL glxDriver
  
  when (initialized gl) $ do
         currentTime <- getCurrentTime
         let mainState = MainState {driver = SomeDriver gl, time = currentTime}
             gameState = GameState {level = testLevel, tanks = [Tank 0.0 0.0 0]}
         
         setup 800 600
         runGame gameState $ runMain mainState $ mainLoop
         
         deinitGL gl

minFrameTime :: NominalDiffTime
minFrameTime = 0.01

mainLoop :: Main ()
mainLoop = do
  gl <- gets driver
  t <- gets time
  run <- liftIO $ handleEvents gl
  
  lift render
  
  liftIO $ swapBuffers gl
  
  rtime <- liftIO getCurrentTime
  let drender = diffUTCTime rtime t
  when (drender < minFrameTime) $
       liftIO $ threadDelay $ truncate $ 1e6*(minFrameTime - drender)
  
  currenttime <- liftIO getCurrentTime
  let d = round $ 1e3*(diffUTCTime currenttime t)
  
  lift $ modify $ \state -> state {tanks = (Tank ((posx . head . tanks $ state)+(0.0001* fromIntegral d)) 0.0 0):(tail . tanks $ state)}
  
  liftIO $ print $ d
  
  let newtime = addUTCTime ((1e-3)*(fromIntegral d)) t
  
  modify $ \state -> state {time = newtime}
  
  when run $ mainLoop


handleEvents :: Driver a => a -> IO Bool
handleEvents gl = do
  event <- nextEvent gl
  if (isJust event)
      then
          handleEvent $ fromJust event
      else
          return True

handleEvent :: SomeEvent -> IO Bool
handleEvent ev
    | Just (ResizeEvent w h) <- fromEvent ev = do
                                  resize w h
                                  return True
    | Just QuitEvent <- fromEvent ev = return False
    | otherwise                      = return True