Module.hs

{-# OPTIONS_GHC -fno-warn-orphans #-}
{-|
Module      : Game.GoreAndAsh.Logging.Module
Description : Monad transformer for logging module
Copyright   : (c) Anton Gushcha, 2015-2016
License     : BSD3
Maintainer  : ncrashed@gmail.com
Stability   : experimental
Portability : POSIX

Contains description of logging monad transformer and instance for
'GameModule' class.
-}
module Game.GoreAndAsh.Logging.Module(
    LoggingT(..)
  ) where

import Control.Monad.Catch
import Control.Monad.Fix 
import Control.Monad.State.Strict
import qualified Data.Sequence as S
import qualified Data.Text.IO as T

import Game.GoreAndAsh
import Game.GoreAndAsh.Logging.State

-- | Monad transformer of logging core module.
--
-- [@s@] - State of next core module in modules chain;
--
-- [@m@] - Next monad in modules monad stack;
--
-- [@a@] - Type of result value;
--
-- How to embed module:
-- 
-- @
-- type AppStack = ModuleStack [LoggingT, ... other modules ... ] IO
--
-- newtype AppMonad a = AppMonad (AppStack a)
--   deriving (Functor, Applicative, Monad, MonadFix, MonadIO, LoggingMonad)
-- @
--
-- The module is pure within first phase (see 'ModuleStack' docs) and could be used
-- with 'Identity' end monad.
newtype LoggingT s m a = LoggingT { runLoggingT :: StateT (LoggingState s) m a }
  deriving (Functor, Applicative, Monad, MonadState (LoggingState s), MonadFix, MonadTrans, MonadIO, MonadThrow, MonadCatch, MonadMask)

instance GameModule m s => GameModule (LoggingT s m) (LoggingState s) where 
  type ModuleState (LoggingT s m) = LoggingState s
  runModule (LoggingT m) s = do
    ((a, s'), nextState) <- runModule (runStateT m s) (loggingNextState s)
    printAllMsgs s'
    return (a, s' { 
        loggingMsgs = S.empty
      , loggingNextState = nextState 
      })
    where 
      printAllMsgs LoggingState{..} = liftIO $ mapM_ T.putStrLn loggingMsgs      

  newModuleState = do
    s <- newModuleState
    return $ LoggingState {
        loggingMsgs = S.empty
      , loggingNextState = s
      }

  withModule _ = id
  cleanupModule _ = return ()