{-# LANGUAGE CPP                        #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE LambdaCase                 #-}
{-# LANGUAGE OverloadedStrings          #-}
module Network.QueryResponse.TCP where

#ifdef THREAD_DEBUG
import Control.Concurrent.Lifted.Instrument
#else
import Control.Concurrent.Lifted
import GHC.Conc                  (labelThread,forkIO)
import ForkLabeled
#endif

import Control.Arrow
import Control.Concurrent.STM
import Control.Concurrent.STM.TMVar
import Control.Monad
import Data.ByteString (ByteString,hPut)
import Data.Function
import Data.Hashable
import Data.Maybe
import Data.Ord
import Data.Time.Clock.POSIX
import Data.Word
import Data.String (IsString(..))
import Network.BSD
import Network.Socket as Socket
import System.Timeout
import System.IO
import System.IO.Error

import DebugTag
import DebugUtil
import DPut
import Connection.Tcp (socketFamily)
import qualified Data.MinMaxPSQ as MM
import Network.QueryResponse

data TCPSession st
    = PendingTCPSession
    | TCPSession
        { tcpHandle :: Handle
        , tcpState  :: st
        , tcpThread :: ThreadId
        }

newtype TCPAddress = TCPAddress SockAddr
 deriving (Eq,Ord,Show)

instance Hashable TCPAddress where
    hashWithSalt salt (TCPAddress x) = case x of
        SockAddrInet port addr   -> hashWithSalt salt (fromIntegral port :: Word16,addr)
        SockAddrInet6 port b c d -> hashWithSalt salt (fromIntegral port :: Word16,b,c,d)
        _                        -> 0

data TCPCache st = TCPCache
    { lru    :: TVar (MM.MinMaxPSQ' TCPAddress (Down POSIXTime) (TCPSession st))
    , tcpMax :: Int
    }

-- This is a suitable /st/ parameter to 'TCPCache'
data SessionProtocol x y = SessionProtocol
    { streamGoodbye :: IO ()        -- ^ "Goodbye" protocol upon termination.
    , streamDecode  :: IO (Maybe x) -- ^ Parse inbound messages.
    , streamEncode  :: y -> IO ()   -- ^ Serialize outbound messages.
    }

data StreamHandshake addr x y = StreamHandshake
    { streamHello :: addr -> Handle -> IO (SessionProtocol x y) -- ^ "Hello" protocol upon fresh connection.
    , streamAddr  :: addr -> SockAddr
    }

killSession :: TCPSession (SessionProtocol x y) -> IO ()
killSession TCPSession{tcpState=st,tcpHandle=h,tcpThread=t} = do
    catchIOError (streamGoodbye st >> hClose h)
                 (\e -> return ())
    killThread t
killSession _ = return ()

showStat :: IsString p => TCPSession st -> p
showStat r = case r of PendingTCPSession -> "pending."
                       TCPSession {}     -> "established."

tcp_timeout :: Int
tcp_timeout = 10000000


removeOnFail :: TCPCache (SessionProtocol x y) -> Handle -> TCPAddress -> IO () -> IO ()
removeOnFail tcpcache h addr action = action `catchIOError` \e -> do
    join $ atomically $ do
        c <- readTVar (lru tcpcache)
        case MM.lookup' addr c of
            Just (tm, v@TCPSession {tcpHandle=stored}) | h == stored -> do
                modifyTVar' (lru tcpcache) $ MM.delete addr
                return $ killSession v
            _ -> return $ return ()
    dput XTCP $ "TCP-send " ++ show addr ++ " " ++ show e

lookupSession :: TCPCache st -> POSIXTime -> TCPAddress -> Bool -> STM (Maybe (Down POSIXTime, TCPSession st))
lookupSession tcpcache now saddr bDoCon = do
        c <- readTVar (lru tcpcache)
        let v = MM.lookup' saddr c
        case v of
            Nothing | bDoCon -> writeTVar (lru tcpcache)
                                $ MM.insert' saddr PendingTCPSession (Down now) c
                    | otherwise -> return ()
            Just (tm, v) -> writeTVar (lru tcpcache)
                                $ MM.insert' saddr v (Down now) c
        return v

acquireConnection :: TMVar (Arrival a addr x)
                           -> TCPCache (SessionProtocol x y)
                           -> StreamHandshake addr x y
                           -> addr
                           -> Bool
                           -> IO (Maybe (y -> IO ()))
acquireConnection mvar tcpcache stream addr bDoCon = do
    now <- getPOSIXTime
    -- dput XTCP $ "acquireConnection 0 " ++ show (streamAddr stream addr)
    let saddr = TCPAddress $ streamAddr stream addr
    entry <- atomically $ lookupSession tcpcache now saddr bDoCon
    -- dput XTCP $ "acquireConnection 1 " ++ show (streamAddr stream addr, fmap (second showStat) entry)
    case entry of
        Nothing -> fmap join $ forM (guard bDoCon) $ \() -> do
            proto <- getProtocolNumber "tcp"
            sock <- socket (socketFamily $ streamAddr stream addr) Stream proto
            mh <- catchIOError (do h <- timeout tcp_timeout $ do
                                       connect sock (streamAddr stream addr) `catchIOError` (\e -> close sock)
                                       h <- socketToHandle sock ReadWriteMode
                                       hSetBuffering h NoBuffering
                                       return h
                                   return h)
                               $ \e -> return Nothing
            when (isNothing mh) $ do
                atomically $ modifyTVar' (lru tcpcache) $ MM.delete saddr
                Socket.close sock
            ret <- fmap join $ forM mh $ \h -> do
             mst <- catchIOError (Just <$> streamHello stream addr h)
                                 (\e -> return Nothing)
             case mst of
               Nothing -> do
                atomically $ modifyTVar' (lru tcpcache) $ MM.delete saddr
                return Nothing
               Just st -> do
                dput XTCP $ "TCP Connected! " ++ show (streamAddr stream addr)
                signal <- newTVarIO False
                let showAddr a = show (streamAddr stream a)
                rthread <- forkLabeled ("tcp:"++showAddr addr) $ do
                  atomically (readTVar signal >>= check)
                  fix $ \loop -> do
                    x <- streamDecode st
                    dput XTCP $ "TCP streamDecode " ++ show (streamAddr stream addr) ++ " --> " ++ maybe "Nothing" (const "got") x
                    case x of
                        Just u -> do
                            m <- timeout tcp_timeout $ atomically (putTMVar mvar $ Arrival addr u)
                            when (isNothing m) $ do
                                dput XTCP $ "TCP "++show (streamAddr stream addr) ++ " dropped packet."
                                atomically $ tryTakeTMVar mvar
                                return ()
                            loop
                        Nothing -> do
                            dput XTCP $ "TCP disconnected: " ++ show (streamAddr stream addr)
                            do atomically $ modifyTVar' (lru tcpcache) $ MM.delete saddr
                            c <- atomically $ readTVar (lru tcpcache)
                            now <- getPOSIXTime
                            forM_ (zip [1..] $ MM.toList c) $ \(i,MM.Binding (TCPAddress addr) r (Down tm)) -> do
                                dput XTCP $ unwords [show i ++ ".", "Still connected:",  show addr, show (now - tm), showStat r]
                            mreport <- timeout tcp_timeout $ threadReport False -- XXX: Paranoid timeout
                            case mreport of
                                Just treport -> dput XTCP treport
                                Nothing      -> dput XTCP "TCP ERROR: threadReport timed out."
                            hClose h `catchIOError` \e -> return ()
                let v = TCPSession
                        { tcpHandle = h
                        , tcpState  = st
                        , tcpThread = rthread
                        }
                t <- getPOSIXTime
                retires <- atomically $ do
                    c <- readTVar (lru tcpcache)
                    let (rs,c') = MM.takeView (tcpMax tcpcache)
                                $ MM.insert' saddr v (Down t) c
                    writeTVar (lru tcpcache) c'
                    writeTVar signal True
                    return rs
                forM_ retires $ \(MM.Binding (TCPAddress k) r _) -> void $ forkLabeled ("tcp-close:"++show k) $ do
                    dput XTCP $ "TCP dropped: " ++ show k
                    killSession r
                return $ Just $ \y -> removeOnFail tcpcache h saddr $ streamEncode st y
            when (isNothing ret) $ do
                atomically $ modifyTVar' (lru tcpcache) $ MM.delete saddr
            return ret
        Just (tm, PendingTCPSession)
            | not bDoCon -> return Nothing
            | otherwise  -> fmap join $ timeout tcp_timeout $ atomically $ do
                c <- readTVar (lru tcpcache)
                let v = MM.lookup' saddr c
                case v of
                    Just (_,TCPSession{tcpHandle=h,tcpState=st})
                             -> return $ Just $ \y -> removeOnFail tcpcache h saddr $ streamEncode st y
                    Nothing  -> return Nothing
                    _        -> retry
        Just (tm, v@TCPSession {tcpHandle=h,tcpState=st}) -> return $ Just $ \y -> removeOnFail tcpcache h saddr $ streamEncode st y

closeAll :: TCPCache (SessionProtocol x y) -> StreamHandshake addr x y -> IO ()
closeAll tcpcache stream = do
    dput XTCP "TCP.closeAll called."
    cache <- atomically $ swapTVar (lru tcpcache) MM.empty
    forM_ (MM.toList cache) $ \(MM.Binding (TCPAddress addr) r tm) -> do
        killSession r

-- Use a cache of TCP client connections for sending (and receiving) packets.
-- The boolean value prepended to the message allows the sender to specify
-- whether or not a new connection will be initiated if neccessary.  If 'False'
-- is passed, then the packet will be sent only if there already exists a
-- connection.
tcpTransport :: Int -- ^ maximum number of TCP links to maintain.
                -> StreamHandshake addr x y
                -> IO (TCPCache (SessionProtocol x y), TransportA err addr x (Bool,y))
tcpTransport maxcon stream = do
    msgvar <- atomically newEmptyTMVar
    tcpcache <- atomically $ (`TCPCache` maxcon) <$> newTVar (MM.empty)
    return $ (,) tcpcache Transport
        { awaitMessage   = do
            x <- takeTMVar msgvar
            return (x, return ())
        , sendMessage    = \addr (bDoCon,y) -> do
                                void . forkLabeled "tcp-send" $ do
                                    msock <- acquireConnection msgvar tcpcache stream addr bDoCon
                                    mapM_ ($ y) msock
                                  `catchIOError` \e -> dput XTCP $ "TCP-send: " ++ show e
        , setActive      = \case False -> closeAll tcpcache stream >> atomically (putTMVar msgvar Terminated)
                                 True  -> return ()
        }