{- |
Conduit interfaces for uniform IO targets.
-}
module System.IO.Uniform.Conduit (
  runConduit,
  source,
  sink
  ) where

import System.IO.Uniform
import Control.Monad.Extra
import qualified Data.Conduit as C
import Control.Monad.IO.Class
import Data.ByteString (ByteString)

chunkSize :: Int
chunkSize = 4000

{- |
Places a target at both ends of a conduit pipe.
-}
runConduit :: (MonadIO m, UniformIO u) => u -> C.ConduitM ByteString ByteString m a -> m a
runConduit trg f = C.runConduit $ source trg `C.fuse` f `C.fuseUpstream` sink trg

source :: (MonadIO m, UniformIO u) => u -> C.Source m ByteString
source u =  unlessM (liftIO $ isEOF u) $ do
  dt <- liftIO $ uRead u chunkSize
  C.yield dt
  source u

sink :: (UniformIO u, MonadIO m) => u -> C.Sink ByteString m ()
sink u = do
  dt <- C.await
  case dt of
    Just dt' -> liftIO $ uPut u dt'
    Nothing -> liftIO $ uClose u