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{-# LANGUAGE OverloadedStrings, DeriveGeneric, GeneralizedNewtypeDeriving #-}
{-# LANGUAGE FlexibleContexts, FlexibleInstances, ScopedTypeVariables #-}
module WebSockets (
connectionOptions,
runClientApp,
clientApp,
protocolError,
relayFromSocket,
relayToSocket,
negotiateWireVersion,
WireProtocol(..),
Mode(..),
ClientSends(..),
ServerSends(..),
) where
import Types
import SessionID
import ProtocolBuffers
import PrevActivity
import Network.WebSockets hiding (Message)
import Control.Concurrent.STM
import Control.Concurrent.STM.TMChan
import Control.Concurrent.Async
import Control.Exception
import GHC.Generics (Generic)
import Data.Aeson (FromJSON, ToJSON)
import Data.ProtocolBuffers
import qualified Data.Aeson
import qualified Data.Serialize
import qualified Data.Text as T
import qualified Data.ByteString.Lazy as L
import Data.List
import Data.Monoid
import Control.Monad
-- | Enable compression.
connectionOptions :: ConnectionOptions
connectionOptions = defaultConnectionOptions
{ connectionCompressionOptions =
PermessageDeflateCompression defaultPermessageDeflate
}
-- For some reason, runClient throws ConnectionClosed
-- when the server hangs up cleanly. Catch this unwanted exception.
-- See https://github.com/jaspervdj/websockets/issues/142
runClientApp :: ClientApp a -> IO (Maybe a)
runClientApp app = do
rv <- newEmptyTMVarIO
let go conn = do
r <- app conn
atomically $ putTMVar rv r
catchJust catchconnclosed
(runClientWith "localhost" 8081 "/" connectionOptions [] go)
(\_ -> return ())
atomically (tryReadTMVar rv)
where
catchconnclosed ConnectionClosed = Just ()
catchconnclosed _ = Nothing
-- | Make a client that sends and receives AnyMessages over a websocket.
clientApp
:: Mode
-> (sent -> AnyMessage)
-> (AnyMessage -> Maybe received)
-> (TMChan sent -> TMChan (MissingHashes received) -> SessionID -> IO a)
-> ClientApp a
clientApp mode mksent filterreceived a conn = do
-- Ping every 30 seconds to avoid timeouts caused by proxies etc.
forkPingThread conn 30
_v <- negotiateWireVersion conn
sendBinaryData conn (SelectMode ClientSends mode)
r <- receiveData conn
case r of
Ready ServerSends sid -> bracket setup cleanup (go sid)
WireProtocolError e -> error e
_ -> protocolError conn "Did not get expected Ready message from server"
where
setup = do
schan <- newTMChanIO
rchan <- newTMChanIO
sthread <- async $ relayToSocket conn mksent $
atomically (readTMChan schan)
rthread <- async $ do
relayFromSocket conn $ \v -> do
case filterreceived v of
Nothing -> return ()
Just r -> atomically $ writeTMChan rchan (MissingHashes r)
-- Server sent Done, so close channels.
atomically $ do
closeTMChan schan
closeTMChan rchan
return (schan, rchan, sthread, rthread)
cleanup (schan, _, sthread, rthread) = do
sendBinaryData conn Done
atomically $ closeTMChan schan
-- Wait for any more data from the server.
-- These often die with a ConnectionClosed.
void $ waitCatch sthread
cancel rthread
void $ waitCatch rthread
go sid (schan, rchan, _, _) = a schan rchan sid
relayFromSocket :: Connection -> (AnyMessage -> IO ()) -> IO ()
relayFromSocket conn sender = go
where
go = do
r <- receiveData conn
case r of
AnyMessage msg -> do
sender msg
go
Done -> return ()
WireProtocolError e -> protocolError conn e
_ -> protocolError conn "Protocol error"
relayToSocket :: Connection -> (received -> AnyMessage) -> IO (Maybe received) -> IO ()
relayToSocket conn mksent getter = go
where
go = do
mmsg <- getter
case mmsg of
Nothing -> return ()
Just msg -> do
let MissingHashes wiremsg =
removeHashes $ mksent msg
sendBinaryData conn $ AnyMessage wiremsg
go
-- | Framing protocol used over a websocket connection.
--
-- This is an asynchronous protocol; both client and server can send
-- messages at the same time.
--
-- Messages that only one can send are tagged with ClientSends or
-- ServerSends.
data WireProtocol
= Version [WireVersion]
| SelectMode ClientSends Mode
| Ready ServerSends SessionID
| AnyMessage AnyMessage
| Done
| WireProtocolError String
data ServerSends = ServerSends
data ClientSends = ClientSends
instance WebSocketsData WireProtocol where
toLazyByteString (Version v) = "V" <> Data.Aeson.encode v
toLazyByteString (SelectMode _ m) = "M" <> Data.Aeson.encode m
toLazyByteString (Ready _ sid) = "R" <> Data.Aeson.encode sid
toLazyByteString (AnyMessage msg) = "L" <>
let pmsg = toProtocolBuffer msg :: AnyMessageP
in Data.Serialize.runPutLazy (encodeMessage pmsg)
toLazyByteString Done = "D"
toLazyByteString (WireProtocolError s) = "E" <> Data.Aeson.encode s
fromLazyByteString b = case L.splitAt 1 b of
("V", v) -> maybe (WireProtocolError "invalid JSON in Version")
Version
(Data.Aeson.decode v)
("M", m) -> maybe (WireProtocolError "invalid JSON in Mode")
(SelectMode ClientSends)
(Data.Aeson.decode m)
("R", sid) -> maybe (WireProtocolError "invalid JSON in SessionID")
(Ready ServerSends)
(Data.Aeson.decode sid)
("L", l) -> case Data.Serialize.runGetLazy decodeMessage l of
Left err -> WireProtocolError $ "Protocol buffers decode error: " ++ err
Right (pmsg :: AnyMessageP) -> AnyMessage (fromProtocolBuffer pmsg)
("D", "") -> Done
("E", s) -> maybe (WireProtocolError "invalid JSON in WireProtocolError")
WireProtocolError
(Data.Aeson.decode s)
_ -> WireProtocolError "received unknown websocket message"
fromDataMessage = fromLazyByteString . fromDataMessage
protocolError :: Connection -> String -> IO a
protocolError conn err = do
sendBinaryData conn (WireProtocolError err)
sendClose conn Done
error err
newtype WireVersion = WireVersion T.Text
deriving (Show, Eq, Generic, Ord)
instance FromJSON WireVersion
instance ToJSON WireVersion
supportedWireVersions :: [WireVersion]
supportedWireVersions = [WireVersion "1"]
-- | Send supportedWireVersions and at the same time receive it from
-- the remote side. The highest version present in both lists will be used.
negotiateWireVersion :: Connection -> IO WireVersion
negotiateWireVersion conn = do
(_, resp) <- concurrently
(sendBinaryData conn $ Version supportedWireVersions)
(receiveData conn)
case resp of
Version remoteversions -> case reverse (intersect (sort supportedWireVersions) (sort remoteversions)) of
(v:_) -> return v
[] -> protocolError conn $
"Unable to negotiate protocol Version. I support: " ++ show supportedWireVersions ++ " They support: " ++ show remoteversions
_ -> protocolError conn "Protocol error, did not receive Version"
-- | Modes of operation that can be requested for a websocket connection.
data Mode
= InitMode T.Text -- ^ Text is unused, but reserved for expansion
| ConnectMode T.Text -- ^ Text specifies the SessionID to connect to
deriving (Show, Eq, Generic)
instance FromJSON Mode
instance ToJSON Mode where
|