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|
{-# LANGUAGE OverloadedStrings, DeriveGeneric, GeneralizedNewtypeDeriving, FlexibleContexts, FlexibleInstances #-}
module WebSockets (
connectionOptions,
runClientApp,
clientApp,
protocolError,
relayFromSocket,
relayToSocket,
negotiateWireVersion,
WireProtocol(..),
Mode(..),
ClientSends(..),
ServerSends(..),
) where
import Types
import SessionID
import Network.WebSockets hiding (Message)
import Control.Concurrent.STM
import Control.Concurrent.Async
import Control.Exception
import GHC.Generics (Generic)
import Data.Aeson (FromJSON, ToJSON)
import qualified Data.Aeson
import qualified Data.Binary
import qualified Data.Text as T
import qualified Data.ByteString.Lazy as L
import Data.List
import Data.Monoid
-- | 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 LogMessages over a websocket.
clientApp
:: Mode
-> (sent -> LogMessage)
-> (LogMessage -> Maybe received)
-> (TChan sent -> TChan 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 <- newTChanIO
rchan <- newTChanIO
sthread <- async $ relayFromSocket conn $ \v ->
case filterreceived v of
Nothing -> return ()
Just r -> atomically $ writeTChan rchan r
rthread <- async $ relayToSocket conn $
Just . mksent <$> atomically (readTChan schan)
return (schan, rchan, sthread, rthread)
cleanup (_, _, sthread, rthread) = do
sendBinaryData conn Done
cancel sthread
cancel rthread
go sid (schan, rchan, _, _) = a schan rchan sid
relayFromSocket :: Connection -> (LogMessage -> IO ()) -> IO ()
relayFromSocket conn sender = go
where
go = do
r <- receiveData conn
case r of
LogMessage msg -> do
sender msg
go
Done -> return ()
WireProtocolError e -> protocolError conn e
_ -> protocolError conn "Protocol error"
relayToSocket :: Connection -> (IO (Maybe LogMessage)) -> IO ()
relayToSocket conn getter = go
where
go = do
mmsg <- getter
case mmsg of
Nothing -> go
Just msg -> do
sendBinaryData conn (LogMessage msg)
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
| LogMessage LogMessage
| 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 (LogMessage msg) = "L" <> Data.Binary.encode msg
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.Binary.decodeOrFail l of
Left (_, _, err) -> WireProtocolError $ "Binary decode error: " ++ err
Right (_, _, msg) -> LogMessage msg
("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
|
