hoodle-parser-0.4: src/Text/Hoodle/Parse/Util.hs

-----------------------------------------------------------------------------
-- |
-- Module      : Text.Hoodle.Parse.Util
-- Copyright   : (c) 2015 Ian-Woo Kim
--
-- License     : BSD3
-- Maintainer  : Ian-Woo Kim <ianwookim@gmail.com>
-- Stability   : experimental
-- Portability : GHC
--
-----------------------------------------------------------------------------

module Text.Hoodle.Parse.Util where

import           Control.Applicative
import           Control.Monad.IO.Class
import           Data.Attoparsec.ByteString.Char8
import qualified Data.ByteString.Char8 as B
import           System.Directory
--
import           Data.Hoodle.Simple
--
import qualified Text.Hoodle.Parse.Attoparsec as PA

-- |
withHoodle :: (MonadIO m, Functor m) => FilePath -> (Hoodle -> m a) -> m (Maybe a)
withHoodle fname act = do
    b <- liftIO $ doesFileExist fname
    if not b
      then return Nothing
      else do
        bstr <- liftIO $ B.readFile fname
        case parseOnly PA.hoodle bstr of
          Left _err -> return Nothing
          Right hdl -> Just <$> act hdl