readBlob.hs

import Streaming.Prelude qualified as S
import Streaming qualified as S

-- FIXME: move-to-library
readBlob :: forall m . ( MonadIO m
                       , HasStorage m
                       , Block ByteString ~ ByteString
                       )
         => HashRef
         -> m (Maybe ByteString)

readBlob hr = do
  sto <- getStorage
  let readBlock h = liftIO $ getBlock sto h

  chunks <- S.toList_ $
              deepScan ScanDeep (const $ S.yield Nothing) (fromHashRef hr) readBlock $ \ha -> do
                unless (fromHashRef hr == ha) do
                  readBlock ha >>= S.yield

  let mfo acc el = case (acc, el) of
       (Nothing, Just s) -> Just [s]
       (_, Nothing) -> Nothing
       (Just ss, Just s)  -> Just (s:ss)

  pure $ LBS.concat . reverse <$> foldl mfo Nothing chunks