module Data.Conduit.ResumableSink (
ResumableSink(..), connectResumeSink, newResumableSink, closeResumableSink,
(+$$), (++$$), (-++$$)
)
where
import Data.Conduit.Internal
import Data.Conduit
import Data.Void
data ResumableSink m i r = ResumableSink (Sink i m r)
connectResumeSink
:: Monad m => Source m i -> ResumableSink m i r -> m (Either r (ResumableSink m i r))
connectResumeSink left0 (ResumableSink right0) =
go (return ()) left0 right0
where
go :: Monad m => m () -> Source m i -> Sink i m r -> m (Either r (ResumableSink m i r))
go leftFinal left right =
case right of
Done r -> leftFinal >> (return . Left $ r)
PipeM mp -> mp >>= go leftFinal left
HaveOutput _ _ o -> absurd o
Leftover p i -> go leftFinal (HaveOutput left leftFinal i) p
NeedInput rp _ ->
case left of
Leftover p () -> go leftFinal p right
HaveOutput left' leftFinal' o -> go leftFinal' left' (rp o)
NeedInput _ lc -> go leftFinal (lc ()) right
Done () -> return . Right $ ResumableSink right
PipeM mp -> mp >>= \left' -> go leftFinal left' right
newResumableSink :: Monad m => Sink i m r -> ResumableSink m i r
newResumableSink s = ResumableSink s
closeResumableSink :: Monad m => ResumableSink m i r -> m r
closeResumableSink (ResumableSink sink) =
go sink
where
go right =
case right of
Leftover p i -> do
res <- connectResumeSink (HaveOutput (return ()) (return ()) i) (ResumableSink p)
case res of
Left r -> return r
Right rs -> closeResumableSink rs
HaveOutput _ _ o -> absurd o
NeedInput _ r -> go (r ())
Done r -> return r
PipeM mp -> mp >>= go
(+$$) :: Monad m => Source m i -> Sink i m r -> m (Either r (ResumableSink m i r))
source +$$ sink = source `connectResumeSink` (newResumableSink sink)
(++$$) :: Monad m => Source m i -> ResumableSink m i r -> m (Either r (ResumableSink m i r))
(++$$) = connectResumeSink
(-++$$) :: Monad m => Source m i -> ResumableSink m i r -> m r
source -++$$ (ResumableSink sink) = do
r <- source $$ sink
return r