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