1 files changed, 93 insertions, 0 deletions

diff --git a/src/Network/BitTorrent/Exchange/Session/Metadata.hs b/src/Network/BitTorrent/Exchange/Session/Metadata.hs
new file mode 100644
index 00000000..7e14f493
--- /dev/null
+++ b/src/Network/BitTorrent/Exchange/Session/Metadata.hs
@@ -0,0 +1,93 @@
+{-# LANGUAGE TemplateHaskell #-}
+module Network.BitTorrent.Exchange.Session.Metadata
+       ( -- * Metadata transfer state
+         Status
+       , nullStatus
+
+         -- * Metadata updates
+       , Updates
+       , runUpdates
+
+         -- * Metadata piece control
+       , scheduleBlock
+       , resetPending
+       , cancelPending
+       , pushBlock
+       ) where
+
+import Control.Concurrent
+import Control.Lens
+import Control.Monad.State
+import Data.ByteString as BS
+import Data.ByteString.Lazy as BL
+import Data.List as L
+
+import Data.BEncode as BE
+import Data.Torrent
+import Data.Torrent.InfoHash
+import Data.Torrent.Piece as Torrent
+import Network.BitTorrent.Core
+import Network.BitTorrent.Exchange.Block   as Block
+import Network.BitTorrent.Exchange.Message as Message hiding (Status)
+
+
+data Status = Status
+  { _pending :: [(PeerAddr IP, PieceIx)]
+  , _bucket  :: Bucket
+  }
+
+makeLenses ''Status
+
+nullStatus :: PieceSize -> Status
+nullStatus ps = Status [] (Block.empty ps)
+
+type Updates a = State Status a
+
+runUpdates :: MVar Status -> Updates a -> IO a
+runUpdates v m = undefined
+
+scheduleBlock :: PeerAddr IP -> Updates (Maybe PieceIx)
+scheduleBlock addr = do
+  bkt <- use bucket
+  case spans metadataPieceSize bkt of
+    []              -> return Nothing
+    ((off, _ ) : _) -> do
+      let pix = undefined
+      pending %= ((addr, pix) :)
+      return (Just pix)
+
+cancelPending :: PieceIx -> Updates ()
+cancelPending pix = pending %= L.filter ((pix ==) . snd)
+
+resetPending :: PeerAddr IP -> Updates ()
+resetPending addr = pending %= L.filter ((addr ==) . fst)
+
+parseInfoDict :: BS.ByteString -> InfoHash -> Result InfoDict
+parseInfoDict chunk topic =
+  case BE.decode chunk of
+    Right (infodict @ InfoDict {..})
+      | topic == idInfoHash -> return infodict
+      |      otherwise      -> Left "broken infodict"
+    Left err -> Left $ "unable to parse infodict " ++ err
+
+-- todo use incremental parsing to avoid BS.concat call
+pushBlock :: PeerAddr IP -> Torrent.Piece BS.ByteString -> InfoHash
+          -> Updates (Maybe InfoDict)
+pushBlock addr Torrent.Piece {..} topic = do
+  p <- use pending
+  when ((addr, pieceIndex) `L.notElem` p) $ error "not requested"
+  cancelPending pieceIndex
+
+  bucket %= Block.insert (metadataPieceSize * pieceIndex) pieceData
+  b <- use bucket
+  case toPiece b of
+    Nothing     -> return Nothing
+    Just chunks ->
+        case parseInfoDict (BL.toStrict chunks) topic of
+          Right x -> do
+              pending .= []
+              return (Just x)
+          Left  e -> do
+              pending .= []
+              bucket  .= Block.empty (Block.size b)
+              return Nothing