{-# LANGUAGE OverloadedStrings #-}

import           Conduit ( Conduit, await, leftover, yield, liftIO
                         , (=$), ($$), ($$+), ($$++), ($$+-))
import           Control.Concurrent.Async (race_)
import           Data.ByteString (ByteString)
import qualified Data.ByteString as S
import qualified Data.ByteString.Char8 as C
import           Data.Conduit.Network ( runTCPServer, runTCPClient
                                      , serverSettings, clientSettings
                                      , appSource, appSink)
import           Data.Monoid ((<>))
import           GHC.IO.Handle (hSetBuffering, BufferMode(NoBuffering))
import           GHC.IO.Handle.FD (stdout)

import Shadowsocks.Encrypt (getEncDec)
import Shadowsocks.Util

initLocal :: Conduit ByteString IO ByteString
initLocal = do
    await
    yield "\x05\x00"
    await >>= maybe (return ()) (\request -> do
        let (addrType, destAddr, destPort, _) = unpackRequest (S.drop 3 request)
            packed = packRequest addrType destAddr destPort
        yield "\x05\x00\x00\x01\x00\x00\x00\x00\x10\x10"
        liftIO $ C.putStrLn $ "connecting " <> destAddr
                                            <> ":" <> C.pack (show destPort)
        leftover packed)

initRemote :: (ByteString -> IO ByteString)
           -> Conduit ByteString IO ByteString
initRemote encrypt = do
    mAddrToSend <- await
    case mAddrToSend of
        Just addrToSend -> do
            enc <- liftIO $ encrypt addrToSend
            yield enc
        Nothing -> return ()

main :: IO ()
main = do
    hSetBuffering stdout NoBuffering
    config <- parseConfigOptions
    let localSettings = serverSettings (local_port config) "*"
        remoteSettings = clientSettings (server_port config)
                                        (C.pack $ server config)
    C.putStrLn $ "starting local at " <> C.pack (show $ local_port config)
    runTCPServer localSettings $ \client -> do
        (encrypt, decrypt) <- getEncDec (method config) (password config)
        (clientSource, ()) <- appSource client $$+ initLocal =$ appSink client
        runTCPClient remoteSettings $ \appServer -> do
            (clientSource', ()) <-
                clientSource $$++ initRemote encrypt =$ appSink appServer
            race_
                (clientSource' $$+- cryptConduit encrypt =$ appSink appServer)
                (appSource appServer $$ cryptConduit decrypt =$ appSink client)