{-# LANGUAGE OverloadedStrings #-}
module XMPPServer
    ( xmppServer
    ) where
import Control.Monad.Trans.Resource (runResourceT)
import Control.Monad.Trans (lift)
import Control.Monad.IO.Class (MonadIO, liftIO)
import Control.Monad.Fix (fix)
import Control.Monad
import Control.Concurrent (forkIO)
import Control.Concurrent.STM
-- import Control.Concurrent.STM.TChan
import Network.Socket
import XMPPTypes (withPort)
import Text.Printf
import System.Posix.Signals
import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as Strict8
-- import qualified Data.ByteString.Lazy.Char8 as Lazy8

import Data.Conduit
import qualified Data.Conduit.List as CL
import qualified Data.Conduit.Binary as CB
import Data.Conduit.Blaze (builderToByteStringFlush)

import qualified Text.XML.Stream.Render as XML
import qualified Text.XML.Stream.Parse as XML
import Data.XML.Types as XML
import Data.Maybe (catMaybes,fromJust)
import Data.Monoid ( (<>) )
import Data.Text (Text)
import qualified Data.Text as Text (pack)

import qualified Control.Concurrent.STM.UpdateStream as Slotted
import ControlMaybe
import Nesting
import EventUtil
import Server

peerport = 5269
clientport = 5222


-- TODO: http://xmpp.org/rfcs/rfc6120.html#rules-remote-error

addrToText :: SockAddr -> Text
addrToText (addr@(SockAddrInet _ _)) = Text.pack $ stripColon (show addr)
 where stripColon s = pre where (pre,port) = break (==':') s
addrToText (addr@(SockAddrInet6 _ _ _ _)) = Text.pack $ stripColon (show addr)
 where stripColon s = if null bracket then pre else pre ++ "]"
          where
            (pre,bracket) = break (==']') s

wlog s = putStrLn s
 where _ = s :: String
wlogb s = Strict8.putStrLn s

xmlStream :: ReadCommand -> WriteCommand -> ( Source IO XML.Event
                                            , Sink (Flush XML.Event) IO () )
xmlStream conread conwrite = (xsrc,xsnk)
 where
    xsrc = src $= XML.parseBytes XML.def
    xsnk = -- XML.renderBytes XML.def =$ snk
        XML.renderBuilderFlush XML.def 
        =$= builderToByteStringFlush 
        =$= discardFlush 
        =$ snk
      where
        discardFlush :: Monad m => ConduitM (Flush a) a m ()
        discardFlush = awaitForever $ \x -> do
            let unchunk (Chunk a) = a
                ischunk (Chunk _) = True
                ischunk _         = False
            when (ischunk x) $ yield (unchunk x)

    src = do
        v <- lift conread
        maybe (return ()) -- lift . wlog $ "conread: Nothing")
              (\v -> yield v >> src)
              v
    snk = awaitForever $ liftIO . conwrite
        

type FlagCommand = STM Bool
type ReadCommand = IO (Maybe ByteString)
type WriteCommand = ByteString -> IO Bool

data Stanza
    = UnrecognizedStanza { stanzaChan :: TChan (Maybe XML.Event) }
    | PingStanza { stanzaId :: Maybe Text
                 , stanzaChan :: TChan (Maybe XML.Event) }
    | PongStanza { -- stanzaId :: Maybe Text
                   stanzaChan :: TChan (Maybe XML.Event) }

copyToChannel f chan = awaitForever copy
 where
    copy x = do 
        liftIO . atomically $ writeTChan chan (f x)
        yield x


prettyPrint prefix xs = 
    liftIO $ 
        CL.sourceList xs
        $= XML.renderBytes (XML.def { XML.rsPretty=True })
        =$= CB.lines 
        $$ CL.mapM_ (wlogb . (prefix <>))

grockStanzaIQGet :: Monad m => XML.Event -> NestingXML o m (Maybe (TChan (Maybe Event) -> Stanza))
grockStanzaIQGet stanza = do
    let mid   = lookupAttrib "id" (tagAttrs stanza)
        -- mfrom = lookupAttrib "from" (tagAttrs stanza)
    mtag <- nextElement 
    flip (maybe $ return Nothing)  mtag $ \tag -> do
    case tagName tag of
        "{urn:xmpp:ping}ping" -> do
            return $ Just (PingStanza mid)
        _ -> return Nothing

ioWriteChan c v = liftIO . atomically $ writeTChan c v

xmppInbound :: ConnectionKey -> FlagCommand 
                -> Source IO XML.Event
                -> TChan Stanza
                -> TChan Stanza
                -> Sink XML.Event IO ()
xmppInbound k pingflag src stanzas output = doNestingXML $ do
    withXML $ \begindoc -> do
    when (begindoc==EventBeginDocument) $ do
    whenJust nextElement $ \xml -> do
    withJust (elementAttrs "stream" xml) $ \stream_attrs -> do
    fix $ \loop -> do
    -- liftIO . wlog $ "waiting for stanza."
    chan <- liftIO $ atomically newTChan
    whenJust nextElement $ \stanza -> do
        stanza_lvl <- nesting
        ioWriteChan chan (Just stanza)
        copyToChannel Just chan =$= do
          dispatch <- 
            case () of
                _ | stanza `isServerIQOf` "get" -> grockStanzaIQGet stanza
                _ -> return $ Just UnrecognizedStanza
          flip (maybe $ return ()) dispatch $ \dispatch -> 
            case dispatch chan of
              d@(PingStanza {}) -> do
                let to = "todo"
                    from = "todo"
                let pong = peerPong (stanzaId d) to from
                pongChan <- liftIO $ atomically newTChan
                ioWriteChan output (PongStanza pongChan)
                mapM_ (ioWriteChan pongChan . Just) pong
                ioWriteChan pongChan Nothing
              disp -> ioWriteChan stanzas disp
          awaitCloser stanza_lvl
        ioWriteChan chan Nothing
        loop
    

chanContents :: TChan x -> IO [x]
chanContents ch = do
        x  <- atomically $ do
            bempty <- isEmptyTChan ch
            if bempty
                then return Nothing
                else fmap Just $ readTChan ch
        maybe (return [])
              (\x -> do
                xs <- chanContents ch
                return (x:xs))
              x

readUntilNothing :: TChan (Maybe x) -> IO [x]
readUntilNothing ch = do
        x  <- atomically $ readTChan ch
        maybe (return [])
              (\x -> do
                xs <- readUntilNothing ch
                return (x:xs))
              x


greetPeer =
    [ EventBeginDocument
    , EventBeginElement (streamP "stream")
        [ attr "xmlns"   "jabber:server"
        , attr "version" "1.0"
        ]
    ]

goodbyePeer = 
    [ EventEndElement (streamP "stream")
    , EventEndDocument
    ]

data XMPPState
    = PingSlot
 deriving (Eq,Ord)


peerPing :: Maybe Text -> Text -> Text -> [XML.Event]
peerPing mid to from = 
       [ EventBeginElement "{jabber:server}iq"
         $ (case mid of
            Just c -> (("id",[ContentText c]):)
            _      -> id               )
            [ ("type",[ContentText "get"])
            , attr "to"   to
            , attr "from" from
            ]
       , EventBeginElement "{urn:xmpp:ping}ping" []
       , EventEndElement "{urn:xmpp:ping}ping"
       , EventEndElement "{jabber:server}iq" ]

peerPong mid to from =
       [ EventBeginElement "{jabber:server}iq"
         $(case mid of
               Just c -> (("id",[ContentText c]):)
               _      -> id)
               [ attr "type" "result"
               , attr "to"   to
               , attr "from" from
               ]
       , EventEndElement "{jabber:server}iq"
       ]


forkConnection :: ConnectionKey
                -> FlagCommand
                -> Source IO XML.Event
                -> Sink (Flush XML.Event) IO ()
                -> TChan Stanza
                ->  IO (TChan Stanza)
forkConnection k pingflag src snk stanzas = do
    rdone <- atomically newEmptyTMVar
    slots <- atomically $ Slotted.new isEventBeginElement isEventEndElement
    needsFlush <- atomically $ newTVar False
    let _ = slots :: Slotted.UpdateStream XMPPState XML.Event
    let greet_src = do
            CL.sourceList greetPeer =$= CL.map Chunk
            yield Flush
        slot_src = do
            what <- lift . atomically $ foldr1 orElse
                [Slotted.pull slots >>= \x -> do
                    writeTVar needsFlush True
                    return $ do
                    yield (Chunk x)
                    slot_src
                ,do Slotted.isEmpty slots >>= check
                    readTVar needsFlush >>= check
                    writeTVar needsFlush False
                    return $ do
                    yield Flush
                    slot_src
                ,readTMVar rdone >> return (return ())
                ]
            what
    forkIO $ do (greet_src >> slot_src) $$ snk
                wlog $ "end post-queue fork: " ++ show k
    output <- atomically newTChan
    forkIO $ do
        -- mapM_ (atomically . Slotted.push slots Nothing) greetPeer
        fix $ \loop -> do
            what <- atomically $ foldr1 orElse
                [readTChan output >>= \stanza -> return $ do
                    let xchan = stanzaChan stanza
                    fix $ \inner -> do
                        what <- atomically $ orElse
                            (readTChan xchan >>= \mxml -> return $ do
                                case mxml of
                                  Just xml -> do
                                    atomically $ Slotted.push slots Nothing xml
                                    inner
                                  Nothing -> loop)
                            (readTMVar rdone >> return (return ()))
                        what
                ,do pingflag >>= check
                    return $ do
                    let to = addrToText (callBackAddress k)
                        from = "todo" -- Look it up from Server object
                                      -- or pass it with Connection event.
                        mid = Just "ping"
                    mapM_ (atomically . Slotted.push slots (Just $ PingSlot))
                          (peerPing mid to from)
                    loop
                ,readTMVar rdone >> return (return ())
                ]
            what
        wlog $ "end pre-queue fork: " ++ show k
    forkIO $ do
        -- src $$ awaitForever (lift . putStrLn . takeWhile (/=' ') . show)
        src $$ xmppInbound k pingflag src stanzas output
        atomically $ putTMVar rdone ()
        wlog $ "end reader fork: " ++ show k
    return output

data ConnectionKey
       = PeerKey { callBackAddress :: SockAddr }
       | ClientKey { localAddress :: SockAddr }
 deriving (Show, Ord, Eq)

{-
data Peer = Peer
    { peerWanted :: TVar Bool -- ^ False when this peer is on a you-call-me basis
    , peerState :: TVar PeerState
    }
data PeerState
    = PeerPendingConnect UTCTime
    | PeerPendingAccept UTCTime
    | PeerConnected (TChan Stanza)
-}

peerKey (sock,addr) = do
    peer <- 
      sIsConnected sock >>= \c -> 
        if c then getPeerName sock -- addr is normally socketName
             else return addr      -- Weird hack: addr is would-be peer name
    return $ PeerKey (peer `withPort` fromIntegral peerport)

clientKey (sock,addr) = return $ ClientKey addr

monitor sv params = do
    chan <- return $ serverEvent sv
    stanzas <- atomically newTChan
    fix $ \loop -> do
    action <- atomically $ foldr1 orElse
      [ readTChan chan >>= \(k,e) -> return $ do 
        case e of
            Connection pingflag conread conwrite -> do
                 wlog $ tomsg k "Connection"
                 let (xsrc,xsnk) = xmlStream conread conwrite
                 forkConnection k pingflag xsrc xsnk stanzas
                 return ()
            ConnectFailure addr -> do
                wlog $ tomsg k "ConnectFailure"
            EOF        -> wlog $ tomsg k "EOF"
            HalfConnection In -> do
                wlog $ tomsg k "ReadOnly"
                control sv (Connect (callBackAddress k) params)
            HalfConnection Out -> wlog $ tomsg k "WriteOnly"
            RequiresPing -> wlog $ tomsg k "RequiresPing"
            _ -> return ()
      , readTChan stanzas >>= \stanza -> return $ do
        xs <- readUntilNothing (stanzaChan stanza)
        wlog ""
        prettyPrint "STANZA: " xs
      ]
    action
    loop
 where
    tomsg k str =  printf "%12s %s" str (show k)
        where
            _ = str :: String


xmppServer :: (MonadResource m, MonadIO m) => m (Server ConnectionKey,ConnectionParameters ConnectionKey)
xmppServer = do
    sv <- server
    let peer_params = (connectionDefaults peerKey)
                          { pingInterval = 10000
                          , timeout = 10000
                          , duplex = False }
        client_params = connectionDefaults clientKey
    liftIO $ do
        forkIO $ monitor sv peer_params
        control sv (Listen peerport peer_params)
        -- todo
        -- control sv (Listen clientport client_params)
    return (sv,peer_params)