path: root/Presence/XMPPServer.hs

{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE FlexibleInstances #-} -- instance for TChan Event
{-# LANGUAGE DoAndIfThenElse #-}
{-# LANGUAGE ExistentialQuantification #-}
module XMPPServer
    ( xmppServer
    , forkXmpp
    , quitXmpp
    , ClientAddress
    , PeerAddress
    , Local(..)
    , Remote(..)
    , ConnectionData(..)
    , ConnectionType(..)
    , XMPPServerParameters(..)
    , XMPPServer
    , classifyConnection
    , addrToPeerKey
    , addrFromClientKey
    , xmppConnections
    , xmppEventChannel
    , StanzaWrap(..)
    , Stanza(..)
    , StanzaType(..)
    , StanzaOrigin(..)
    , cloneStanza
    , LangSpecificMessage(..)
    , peerKeyToText
    , addrToText
    , sendModifiedStanzaToPeer
    , sendModifiedStanzaToClient
    , presenceProbe
    , presenceSolicitation
    , makePresenceStanza
    , makeInformSubscription
    , makeRosterUpdate
    , makeMessage
    , JabberShow(..)
    , Server
    , flushPassThrough
    , greet'
    , (<&>)
    , grokStanza
    ) where

import ConnectionKey
import qualified Control.Concurrent.STM.UpdateStream as Slotted
import Nesting
import Connection.Tcp
import EventUtil
import ControlMaybe
import LockedChan
import Connection (PeerAddress(..))
import qualified Connection
import Util
import Network.Address (getBindAddress, sockAddrPort)

import Data.Bits
import Data.Word
import Debug.Trace
import Control.Monad.Trans (lift)
import Control.Monad.IO.Class (MonadIO, liftIO)
import Control.Monad.Fix (fix)
import Control.Monad
#ifdef THREAD_DEBUG
import Control.Concurrent.Lifted.Instrument (forkIO,myThreadId,labelThread,ThreadId,MVar,putMVar,takeMVar,newMVar)
#else
import Control.Concurrent.Lifted (forkIO,myThreadId,ThreadId)
import GHC.Conc                  (labelThread)
#endif
import Control.Concurrent.STM
-- import Control.Concurrent.STM.TChan
import Network.SocketLike
import Text.Printf
import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as Strict8
-- import qualified Data.ByteString.Lazy.Char8 as Lazy8
import Data.Int (Int8)

import Data.Conduit
import qualified Data.Conduit.List as CL
import qualified Data.Conduit.Binary as CB
#if MIN_VERSION_conduit_extra(1,1,7)
import Data.Conduit.ByteString.Builder (builderToByteStringFlush)
#else
import Data.Conduit.Blaze (builderToByteStringFlush)
#endif
import Control.Monad.Catch (MonadThrow)

import DNSCache (withPort)
import qualified Text.XML.Stream.Render as XML hiding (content)
import qualified Text.XML.Stream.Parse as XML
import Data.XML.Types as XML
import Data.Maybe
import Data.Monoid ( (<>) )
import Data.Text (Text)
import qualified Data.Text as Text (pack,unpack,words,intercalate,drop)
import Data.Char (chr,ord)
import qualified Data.Map as Map
import Data.Set (Set, (\\) )
import qualified Data.Set as Set
import Data.String ( IsString(..) )
import qualified System.Random
import Data.Void (Void)
import DPut
import DebugTag

-- peerport :: PortNumber
-- peerport = 5269
-- clientport :: PortNumber
-- clientport = 5222

my_uuid :: Text
my_uuid = "154ae29f-98f2-4af4-826d-a40c8a188574"

data JabberShow = Offline
                | ExtendedAway
                | Away
                | DoNotDisturb
                | Available
                | Chatty
 deriving (Show,Enum,Ord,Eq,Read)

data MessageThread = MessageThread {
        msgThreadParent  :: Maybe Text,
        msgThreadContent :: Text
    }
  deriving (Show,Eq)

data LangSpecificMessage =
    LangSpecificMessage { msgBody :: Maybe Text
                        , msgSubject :: Maybe Text
                        }
  deriving (Show,Eq)

data RosterEventType
    = RequestedSubscription
    | NewBuddy -- preceded by PresenceInformSubscription True
    | RemovedBuddy -- preceded by PresenceInformSubscription False
    | PendingSubscriber -- same as PresenceRequestSubscription
    | NewSubscriber
    | RejectSubscriber
 deriving (Show,Read,Ord,Eq,Enum)

data ClientHack = SimulatedChatErrors
 deriving (Show,Read,Ord,Eq,Enum)

data StanzaType
    = Unrecognized
    | Ping
    | Pong
    | RequestResource (Maybe Text) (Maybe Text) -- ^ Client's name for this host followed by client's requested resource id.
    | SetResource
    | SessionRequest
    | UnrecognizedQuery Name
    | RequestRoster
    | Roster
    | RosterEvent { rosterEventType :: RosterEventType
                  , rosterUser :: Text
                  , rosterContact :: Text }
    | Error StanzaError XML.Event
    | PresenceStatus { presenceShow :: JabberShow
                     , presencePriority :: Maybe Int8
                     , presenceStatus :: [(Lang,Text)]
                     , presenceWhiteList :: [Text]
                     }
    | PresenceInformError
    | PresenceInformSubscription Bool
    | PresenceRequestStatus
    | PresenceRequestSubscription Bool
    | Message { msgThread :: Maybe MessageThread
              , msgLangMap :: [(Lang,LangSpecificMessage)]
              }
    | NotifyClientVersion { versionName :: Text
                          , versionVersion :: Text }
    | InternalEnableHack ClientHack
    | InternalCacheId Text
 deriving (Show,Eq)

data StanzaOrigin = LocalPeer
                  | PeerOrigin PeerAddress (TChan Stanza)
                  | ClientOrigin ClientAddress (TChan Stanza)


data StanzaWrap a = Stanza
    { stanzaType :: StanzaType
    , stanzaId :: Maybe Text
    , stanzaTo :: Maybe Text
    , stanzaFrom :: Maybe Text
    , stanzaChan :: a
    , stanzaClosers ::  TVar (Maybe [XML.Event])
    , stanzaInterrupt :: TMVar ()
    , stanzaOrigin :: StanzaOrigin
    }

type Stanza = StanzaWrap (LockedChan XML.Event)

newtype Local a = Local a deriving (Eq,Ord,Show)
newtype Remote a = Remote a deriving (Eq,Ord,Show)

data XMPPServerParameters =
    XMPPServerParameters
    { -- | Called when a client requests a resource id.  The first Maybe indicates
      --   the name the client referred to this server by.  The second Maybe is the
      --   client's preferred resource name.
      --
      -- Note: The returned domain will be discarded and replaced with the result of
      -- 'xmppTellMyNameToClient'.
      xmppChooseResourceName :: ClientAddress -> Remote SockAddr -> Maybe Text -> Maybe Text -> IO Text
    , -- | This should indicate the server's hostname that all client's see.
      xmppTellMyNameToClient :: ClientAddress -> IO Text
    , xmppTellMyNameToPeer   :: Local SockAddr -> IO Text
    , xmppTellClientHisName  :: ClientAddress -> IO Text
    , xmppTellPeerHisName    :: PeerAddress -> IO Text
    , xmppNewConnection      :: SockAddr -> ConnectionData -> TChan Stanza -> IO ()
    , xmppEOF                :: SockAddr -> ConnectionData -> IO ()
    , xmppRosterBuddies      :: ClientAddress -> IO [Text]
    , xmppRosterSubscribers  :: ClientAddress -> IO [Text]
    , xmppRosterSolicited    :: ClientAddress -> IO [Text]
    , xmppRosterOthers       :: ClientAddress -> IO [Text]
    , -- | Called when after sending a roster to a client.  Usually this  means
      -- the client status should change from "available" to "interested".
      xmppSubscribeToRoster  :: ClientAddress -> IO ()
    -- , xmppLookupClientJID :: SockAddr -> IO Text
    , xmppDeliverMessage     :: (IO ()) -> Stanza -> IO ()
      -- | Called whenever a local client's presence changes.
    , xmppInformClientPresence :: ClientAddress -> Stanza -> IO ()
      -- | Called whenever a remote peer's presence changes.
    , xmppInformPeerPresence :: PeerAddress -> Stanza -> IO ()
    , -- | Called when a remote peer requests our status.
      xmppAnswerProbe        :: PeerAddress -> Stanza -> TChan Stanza -> IO ()
    , xmppClientSubscriptionRequest :: IO () -> ClientAddress -> Stanza -> TChan Stanza -> IO ()
    , -- | Called when a remote peer sends subscription request.
      xmppPeerSubscriptionRequest :: IO () -> PeerAddress -> Stanza -> TChan Stanza -> IO ()
    , xmppClientInformSubscription :: IO () -> ClientAddress -> Stanza -> IO ()
    , -- | Called when a remote peer informs us of our subscription status.
      xmppPeerInformSubscription :: IO () -> PeerAddress -> Stanza -> IO ()
    , xmppVerbosity          :: IO Int
    , xmppClientBind         :: Maybe SockAddr
    , xmppPeerBind           :: Maybe SockAddr
    }


enableClientHacks ::
    forall t a.
    (Eq a, IsString a) =>
    a -> t -> TChan Stanza -> IO ()
enableClientHacks "Pidgin" version replyto = do
    wlog "Enabling hack SimulatedChatErrors for client Pidgin"
    donevar <- atomically newEmptyTMVar
    sendReply donevar
              (InternalEnableHack SimulatedChatErrors)
              []
              replyto
enableClientHacks "irssi-xmpp" version replyto = do
    wlog "Enabling hack SimulatedChatErrors for client irssi-xmpp"
    donevar <- atomically newEmptyTMVar
    sendReply donevar
              (InternalEnableHack SimulatedChatErrors)
              []
              replyto
enableClientHacks _ _ _ = return ()

cacheMessageId :: Text -> TChan Stanza -> IO ()
cacheMessageId id' replyto = do
    wlog $ "Caching id " ++ Text.unpack id'
    donevar <- atomically newEmptyTMVar
    sendReply donevar
              (InternalCacheId id')
              []
              replyto


-- TODO: http://xmpp.org/rfcs/rfc6120.html#rules-remote-error
-- client connection
-- socat script to send stanza fragment
-- copyToChannel can keep a stack of closers to append to finish-off a stanza
-- the TMVar () from forkConnection can be passed and with a stanza to detect interruption

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

-- Shows (as Text) the IP address associated with the given SockAddr.
peerKeyToText :: PeerAddress -> Text
peerKeyToText (PeerAddress addr) = addrToText addr


wlog :: String -> IO ()
wlog = dput XJabber

wlogb :: ByteString -> IO ()
wlogb = wlog . Strict8.unpack

flushPassThrough :: Monad m => ConduitT a b m () -> ConduitT (Flush a) (Flush b) m ()
flushPassThrough c = getZipConduit $ ZipConduit (onlyChunks .| mapOutput Chunk c) <* ZipConduit onlyFlushes
  where
    onlyChunks  :: Monad m => ConduitT (Flush a) a m ()
    onlyFlushes :: Monad m => ConduitT (Flush a) (Flush b) m ()
    onlyChunks           = awaitForever yieldChunk
    onlyFlushes          = awaitForever yieldFlush
    yieldFlush Flush     = yield Flush
    yieldFlush _         = return ()
    yieldChunk (Chunk x) = yield x
    yieldChunk _         = return ()

xmlStream :: ReadCommand -> WriteCommand -> ( ConduitT () XML.Event IO ()
                                            , ConduitT (Flush XML.Event) Void IO () )
xmlStream conread conwrite = (xsrc,xsnk)
 where
    xsrc = src .| XML.parseBytes XML.def
    xsnk :: ConduitT (Flush Event) Void IO ()
    xsnk = -- XML.renderBytes XML.def =$ snk
        flushPassThrough (XML.renderBuilder XML.def)
        .| builderToByteStringFlush
        .| discardFlush
        .| snk
      where
        discardFlush :: Monad m => ConduitM (Flush a) a m ()
        discardFlush = awaitForever yieldChunk
        yieldChunk (Chunk x) = yield x
        yieldChunk _ = return ()

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


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

cloneStanza :: StanzaWrap (LockedChan a) -> IO (StanzaWrap (LockedChan a))
cloneStanza stanza = do
    dupped <- cloneLChan (stanzaChan stanza)
    return stanza { stanzaChan = dupped }

copyToChannel
  :: MonadIO m =>
     (Event -> a) -> LockedChan a -> TVar (Maybe [Event]) -> ConduitM Event Event m ()
copyToChannel f chan closer_stack = awaitForever copy
 where
    copy x = do
        liftIO . atomically $ writeLChan chan (f x)
        case x of
            EventBeginDocument {} -> do
                let clsr = closerFor x
                liftIO . atomically $
                    modifyTVar' closer_stack (fmap (clsr:))
            EventEndDocument {} -> do
                liftIO . atomically $
                    modifyTVar' closer_stack (fmap (drop 1))
            _ -> return ()
        yield x


prettyPrint :: ByteString -> ConduitM Event Void IO ()
prettyPrint prefix =
        XML.renderBytes (XML.def { XML.rsPretty=True })
        .| CB.lines
        .| CL.mapM_ (wlogb . (prefix <>))

swapNamespace :: Monad m => Text -> Text -> ConduitM Event Event m ()
swapNamespace old new = awaitForever (yield . swapit old new)

swapit :: Text -> Text -> Event -> Event
swapit old new (EventBeginElement n as) | nameNamespace n==Just old =
    EventBeginElement (n { nameNamespace = Just new }) as
swapit old new (EventEndElement n) | nameNamespace n==Just old =
    EventEndElement (n { nameNamespace = Just new })
swapit old new x = x

fixHeaders :: Monad m => Stanza -> ConduitM Event Event m ()
fixHeaders Stanza { stanzaType=typ, stanzaTo=mto, stanzaFrom=mfrom } = do
    x <- await
    maybe (return ()) f x
 where
    f (EventBeginElement n as) = do yield $ EventBeginElement n (update n as)
                                    awaitForever yield
    f x = yield x >> awaitForever yield
    update n as = as3
     where
        as' = maybe as (setAttrib "to" as) mto
        as'' = maybe as' (setAttrib "from" as') mfrom
        as3 = case typ of
                PresenceStatus {} | nameNamespace n == Just "jabber:client"
                  -> delAttrib "whitelist" as''
                PresenceStatus {} | otherwise
                  -> case presenceWhiteList typ of
                        [] -> delAttrib "whitelist" as''
                        ws -> setAttrib "whitelist" as'' (Text.intercalate " " ws)
                _ -> as''

        setAttrib akey as aval = attr akey aval:filter ((/=akey) . fst) as
        delAttrib akey as = filter ((/=akey) . fst) as

conduitToChan
  :: ConduitT () Event IO ()
     -> IO (LockedChan Event, TVar (Maybe [Event]), TMVar a)
conduitToChan c = do
    chan <- atomically newLockedChan
    clsrs <- atomically $ newTVar (Just [])
    quitvar <- atomically $ newEmptyTMVar
    forkIO $ do
        runConduit $ c .| copyToChannel id chan clsrs .| awaitForever (const $ return ())
        atomically $ writeTVar clsrs Nothing
    return (chan,clsrs,quitvar)

conduitToStanza
  :: StanzaType
     -> Maybe Text -- ^ id
     -> Maybe Text -- ^ from
     -> Maybe Text -- ^ to
     -> ConduitT () Event IO ()
     -> IO Stanza
conduitToStanza stype mid from to c = do
    (chan,clsrs,quitvar) <- conduitToChan c
    return
        Stanza  { stanzaType = stype
                , stanzaId = mid
                , stanzaTo = to
                , stanzaFrom = from
                , stanzaChan = chan
                , stanzaClosers = clsrs
                , stanzaInterrupt = quitvar
                , stanzaOrigin = LocalPeer
                }


ioWriteChan :: MonadIO m => TChan a -> a -> m ()
ioWriteChan c v = liftIO . atomically $ writeTChan c v

stanzaToConduit :: MonadIO m => Stanza -> ConduitM i Event m ()
stanzaToConduit stanza = do
    let xchan = stanzaChan stanza
        xfin = stanzaClosers stanza
        rdone = stanzaInterrupt stanza
        loop = return ()
    xchan <- liftIO $ unlockChan xchan
    fix $ \inner -> do
        what <- liftIO . atomically $ foldr1 orElse
            [readTChan xchan >>= \xml -> return $ do
                yield xml -- atomically $ Slotted.push slots Nothing xml
                inner
            ,do mb <- readTVar xfin
                cempty <- isEmptyTChan xchan
                if isNothing mb
                    then if cempty then return loop else retry
                    else do done <- tryReadTMVar rdone
                            check (isJust done)
                            trace "todo: send closers" retry
            ,do isEmptyTChan xchan >>= check
                readTMVar rdone
                return (return ())]
        what


sendModifiedStanzaToPeer :: Stanza -> TChan Stanza -> IO ()
sendModifiedStanzaToPeer stanza chan = do
    (echan,clsrs,quitvar) <- conduitToChan c
    ioWriteChan chan
        stanza  { stanzaChan = echan
                , stanzaClosers = clsrs
                , stanzaInterrupt = quitvar
                , stanzaType = processedType (stanzaType stanza)
                -- TODO id? origin?
                }
 where
    old = "jabber:client"
    new = "jabber:server"
    c = stanzaToConduit stanza .| swapNamespace old new .| fixHeaders stanza
    processedType (Error cond tag) = Error cond (swapit old new tag)
    processedType x = x


-- Modifies a server-to-server stanza to send it to a client.  This changes the
-- namespace and also filters some non-supported attributes.  Any other
-- modifications need to be made by the caller.
sendModifiedStanzaToClient :: Stanza -> TChan Stanza -> IO ()
sendModifiedStanzaToClient stanza chan = do
    (echan,clsrs,quitvar) <- conduitToChan c
    -- wlog $ "send-to-client " ++ show (stanzaId stanza)
    ioWriteChan chan
        stanza  { stanzaChan = echan
                , stanzaClosers = clsrs
                , stanzaInterrupt = quitvar
                , stanzaType = processedType (stanzaType stanza)
                -- TODO id? origin?
                }
 where
    old = "jabber:server"
    new = "jabber:client"
    c = stanzaToConduit stanza .| swapNamespace old new .| fixHeaders stanza
    processedType (Error cond tag) = Error cond (swapit old new tag)
    processedType x = x


-- id,to, and from are taken as-is from reply list
-- todo: this should probably be restricted to IO monad
sendReply :: (Functor m, MonadIO m) => TMVar () -> StanzaType -> [Event] -> TChan Stanza -> m ()
sendReply donevar stype reply replychan = do
    let stanzaTag = listToMaybe reply
        mid   = stanzaTag >>= lookupAttrib "id" . tagAttrs
        mfrom = stanzaTag >>= lookupAttrib "from" . tagAttrs
        mto = stanzaTag >>= lookupAttrib "to" . tagAttrs
        isInternal (InternalEnableHack {}) = True
        isInternal (InternalCacheId {}) = True
        isInternal _ = False
    forM_
         (fmap (const ()) stanzaTag `mplus` guard (isInternal stype))
         . const $ do
    replyStanza <- liftIO . atomically $ do
        replyChan <- newLockedChan
        replyClsrs <- newTVar (Just [])
        return Stanza { stanzaType = stype
                      , stanzaId = mid
                      , stanzaTo = mto      -- as-is from reply list
                      , stanzaFrom = mfrom  -- as-is from reply list
                      , stanzaChan = replyChan
                      , stanzaClosers = replyClsrs
                      , stanzaInterrupt = donevar
                      , stanzaOrigin = LocalPeer
                      }
    ioWriteChan replychan replyStanza
    void . liftIO . forkIO $ do
        mapM_ (liftIO . atomically . writeLChan (stanzaChan replyStanza)) reply
        liftIO . atomically $ writeTVar (stanzaClosers replyStanza) Nothing
        -- liftIO $ wlog "finished reply stanza"

stanzaFromList :: StanzaType -> [Event] -> IO Stanza
stanzaFromList stype reply = do
    let stanzaTag = listToMaybe reply
        mid   = stanzaTag >>= lookupAttrib "id" . tagAttrs
        mfrom = stanzaTag >>= lookupAttrib "from" . tagAttrs
        mto = stanzaTag >>= lookupAttrib "to" . tagAttrs
        {-
        isInternal (InternalEnableHack {}) = True
        isInternal (InternalCacheId {}) = True
        isInternal _ = False
        -}
    (donevar,replyChan,replyClsrs) <- atomically $ do
        donevar <- newEmptyTMVar -- TMVar ()
        replyChan <- newLockedChan
        replyClsrs <- newTVar (Just [])
        return (donevar,replyChan, replyClsrs)
    forkIO $ do
        forM_ reply $ atomically . writeLChan replyChan
        atomically $ do putTMVar donevar ()
                        writeTVar replyClsrs Nothing
    return Stanza { stanzaType = stype
                  , stanzaId = mid
                  , stanzaTo = mto      -- as-is from reply list
                  , stanzaFrom = mfrom  -- as-is from reply list
                  , stanzaChan = replyChan
                  , stanzaClosers = replyClsrs
                  , stanzaInterrupt = donevar
                  , stanzaOrigin = LocalPeer
                  }

grokStanzaIQGet :: Monad m => XML.Event -> NestingXML o m (Maybe StanzaType)
grokStanzaIQGet stanza = do
    mtag <- nextElement
    forM  mtag $ \tag -> do
    case tagName tag of
        "{urn:xmpp:ping}ping"     -> return Ping
        "{jabber:iq:roster}query" -> return RequestRoster
        name                      -> return $ UnrecognizedQuery name

parseClientVersion :: NestingXML o IO (Maybe StanzaType)
parseClientVersion = parseit Nothing Nothing
 where
    reportit mname mver = return $ do
        name <- mname
        ver <- mver
        return NotifyClientVersion { versionName=name, versionVersion=ver }
    parseit :: Maybe Text -> Maybe Text -> NestingXML o IO (Maybe StanzaType)
    parseit mname mver = do
        mtag <- nextElement
        fromMaybe (reportit mname mver) $ mtag <&> \tag -> do
        case tagName tag of
            "{jabber:iq:version}name" -> do
                x <- XML.content
                parseit (Just x) mver
            "{jabber:iq:version}version" -> do
                x <- XML.content
                parseit mname (Just x)
            _ -> parseit mname mver


grokStanzaIQResult :: XML.Event -> NestingXML o IO (Maybe StanzaType)
grokStanzaIQResult stanza = do
    mtag <- nextElement
    fromMaybe (return $ Just Pong) $ mtag <&> \tag -> do
    case tagName tag of
        "{jabber:iq:version}query" | nameNamespace (tagName stanza)==Just "jabber:client"
            -> parseClientVersion
        _ -> return Nothing

grokStanzaIQSet :: XML.Event -> NestingXML o IO (Maybe StanzaType)
grokStanzaIQSet stanza = do
    mtag <- nextElement
    case tagName <$> mtag of
        Just "{urn:ietf:params:xml:ns:xmpp-bind}bind"
            -> do mchild <- nextElement
                  case tagName <$> mchild of
                    Just "{urn:ietf:params:xml:ns:xmpp-bind}resource"
                            -> do rsc <- XML.content -- TODO: MonadThrow???
                                  return . Just $ RequestResource Nothing (Just rsc)
                    Just _  -> return Nothing
                    Nothing -> return . Just $ RequestResource Nothing Nothing
        Just "{urn:ietf:params:xml:ns:xmpp-session}session"
            -> return $ Just SessionRequest
        _   -> return Nothing


{-
C->Unrecognized <iq
C->Unrecognized   type="set"
C->Unrecognized   id="purpleae62d88f"
C->Unrecognized   xmlns="jabber:client">
C->Unrecognized     <bind xmlns="urn:ietf:params:xml:ns:xmpp-bind"/>
C->Unrecognized </iq>
-}
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


parsePresenceStatus
  :: ( MonadThrow m
     , MonadIO m
     ) => Text -> XML.Event -> NestingXML o m (Maybe StanzaType)
parsePresenceStatus ns stanzaTag = do

    let toStat "away" = Away
        toStat "xa"   = ExtendedAway
        toStat "dnd"  = DoNotDisturb
        toStat "chat" = Chatty

    showv <- liftIO . atomically $ newTVar Available
    priov <- liftIO . atomically $ newTVar Nothing
    statusv <- liftIO . atomically $ newTChan
    fix $ \loop -> do
        mtag <- nextElement
        forM_ mtag $ \tag -> do
        when (nameNamespace (tagName tag) == Just ns) $ do
            case nameLocalName (tagName tag) of
                "show" -> do t <- XML.content
                             liftIO . atomically $ writeTVar showv (toStat t)
                "priority" -> do t <- XML.content
                                 liftIO . handleIO_ (return ()) $ do
                                 prio <- readIO (Text.unpack t)
                                 atomically $ writeTVar priov (Just prio)
                "status" -> do t <- XML.content
                               lang <- xmlLang
                               ioWriteChan statusv (maybe "" id lang,t)
                _ -> return ()
        loop
    show <- liftIO . atomically $ readTVar showv
    prio <- liftIO . atomically $ readTVar priov
    status <- liftIO $ chanContents statusv -- Could use unsafeInterleaveIO to
                                            -- avoid multiple passes, but whatever.
    let wlist = do
            w <- maybeToList $ lookupAttrib "whitelist" (tagAttrs stanzaTag)
            Text.words w
    return . Just $ PresenceStatus { presenceShow = show
                                   , presencePriority = prio
                                   , presenceStatus = status
                                   , presenceWhiteList = wlist
                                   }
grokPresence
  :: ( MonadThrow m
     , MonadIO m
     ) => Text -> XML.Event -> NestingXML o m (Maybe StanzaType)
grokPresence ns stanzaTag = do
    let typ = lookupAttrib "type" (tagAttrs stanzaTag)
    case typ of
        Nothing -> parsePresenceStatus ns stanzaTag
        Just "unavailable"  -> fmap (fmap (\p -> p {presenceShow=Offline}))
                                   $ parsePresenceStatus ns stanzaTag
        Just "error"        -> return . Just $ PresenceInformError
        Just "unsubscribed" -> return . Just $ PresenceInformSubscription False
        Just "subscribed"   -> return . Just $ PresenceInformSubscription True
        Just "probe"        -> return . Just $ PresenceRequestStatus
        Just "unsubscribe"  -> return . Just $ PresenceRequestSubscription False
        Just "subscribe"    -> return . Just $ PresenceRequestSubscription True
        _                   -> return Nothing

parseMessage
  :: ( MonadThrow m
     , MonadIO m
     ) => Text -> XML.Event -> NestingXML o m StanzaType
parseMessage ns stanza = do
    let bodytag = Name { nameNamespace = Just ns
                       , nameLocalName = "body"
                       , namePrefix = Nothing }
        subjecttag = Name { nameNamespace = Just ns
                          , nameLocalName = "subject"
                          , namePrefix = Nothing }
        threadtag = Name { nameNamespace = Just ns
                         , nameLocalName = "thread"
                         , namePrefix = Nothing }
    let emptyMsg = LangSpecificMessage { msgBody=Nothing, msgSubject=Nothing }
        parseChildren (th,cmap) = do
            child <- nextElement
            lvl <- nesting
            xmllang <- xmlLang
            let lang = maybe "" id xmllang
            let c = maybe emptyMsg id (Map.lookup lang cmap)
            -- log $ " child: "<> bshow child
            case child of
                Just tag | tagName tag==bodytag
                                    -> do
                                        txt <- XML.content
                                        awaitCloser lvl
                                        parseChildren (th,Map.insert lang (c { msgBody=Just txt }) cmap)
                Just tag | tagName tag==subjecttag
                                    -> do
                                        txt <- XML.content
                                        awaitCloser lvl
                                        parseChildren (th,Map.insert lang (c { msgSubject=Just txt }) cmap)
                Just tag | tagName tag==threadtag
                                    -> do
                                        txt <- XML.content
                                        awaitCloser lvl
                                        parseChildren (th {msgThreadContent=txt},cmap)
                Just tag -> do
                            -- let nm    = tagName tag
                            --    attrs = tagAttrs tag
                            --    -- elems = msgElements c
                            -- txt <- XML.content
                            awaitCloser lvl
                            parseChildren (th,Map.insert lang c cmap)
                Nothing -> return (th,cmap)
    (th,langmap) <- parseChildren ( MessageThread {msgThreadParent=Nothing, msgThreadContent=""}
                                  , Map.empty )
    return Message {
        msgLangMap = Map.toList langmap,
        msgThread = if msgThreadContent th/="" then Just th else Nothing
    }

findConditionTag :: Monad m => NestingXML o m (Maybe XML.Event)
findConditionTag = do
    mx <- nextElement
    fmap join $ forM mx $ \x -> do
    case nameNamespace (tagName x) of
        Just "urn:ietf:params:xml:ns:xmpp-stanzas" -> return (Just x)
        _                                          -> findConditionTag

conditionFromText :: Text -> Maybe StanzaError
conditionFromText t = fmap fst $ listToMaybe ss
 where
    es = [BadRequest .. UnexpectedRequest]
    ts = map (\e->(e,errorTagLocalName e)) es
    ss = dropWhile ((/=t) . snd) ts

findErrorTag :: Monad m => Text -> NestingXML o m (Maybe StanzaError)
findErrorTag ns = do
    x <- nextElement
    fmap join $ forM x $ \x ->
      case tagName x of
        n | nameNamespace n==Just ns && nameLocalName n=="error"
            -> do
                 mtag <- findConditionTag
                 return $ do
                    tag <- {- trace ("mtag = "++show mtag) -} mtag
                    let t = nameLocalName (tagName tag)
                    conditionFromText t
        _ -> findErrorTag ns

grokMessage
  :: ( MonadThrow m
     , MonadIO m
     ) => Text -> XML.Event -> NestingXML o m (Maybe StanzaType)
grokMessage ns stanzaTag = do
    let typ = lookupAttrib "type" (tagAttrs stanzaTag)
    case typ of
        Just "error" -> do
            mb <- findErrorTag ns
            return $ do
                e <- mb
                return $ Error e stanzaTag
        _ -> do t <- parseMessage ns stanzaTag
                return $ Just t



grokStanza
  ::  Text -> XML.Event -> NestingXML o IO (Maybe StanzaType)
grokStanza "jabber:server" stanzaTag =
            case () of
                _ | stanzaTag `isServerIQOf` "get" -> grokStanzaIQGet stanzaTag
                _ | stanzaTag `isServerIQOf` "result" -> grokStanzaIQResult stanzaTag
                _ | tagName stanzaTag == "{jabber:server}presence" -> grokPresence "jabber:server" stanzaTag
                _ | tagName stanzaTag == "{jabber:server}message" -> grokMessage "jabber:server" stanzaTag
                _ -> return $ Just Unrecognized

grokStanza "jabber:client" stanzaTag =
            case () of
                _ | stanzaTag `isClientIQOf` "get" -> grokStanzaIQGet stanzaTag
                _ | stanzaTag `isClientIQOf` "set" -> grokStanzaIQSet stanzaTag
                _ | stanzaTag `isClientIQOf` "result" -> grokStanzaIQResult stanzaTag
                _ | tagName stanzaTag == "{jabber:client}presence" -> grokPresence "jabber:client" stanzaTag
                _ | tagName stanzaTag == "{jabber:client}message" -> grokMessage "jabber:client" stanzaTag
                _ -> return $ Just Unrecognized

mkname :: Text -> Text -> XML.Name
mkname namespace name = (Name name (Just namespace) Nothing)

makeMessage :: Text -> Text -> Text -> Text -> IO Stanza
makeMessage namespace from to bod =
    stanzaFromList typ
     $ [ EventBeginElement (mkname namespace "message")
            [ attr "from" from
            , attr "to" to
            ]
       , EventBeginElement (mkname namespace "body") []
       , EventContent (ContentText bod)
       , EventEndElement (mkname namespace "body")
       , EventEndElement (mkname namespace "message") ]
 where
    typ = Message { msgThread = Nothing
                  , msgLangMap = [("", lsm)]
                  }
    lsm = LangSpecificMessage
            { msgBody = Just bod
            , msgSubject = Nothing }

makeInformSubscription :: Text -> Text -> Text -> Bool -> IO Stanza
makeInformSubscription namespace from to approved =
    stanzaFromList (PresenceInformSubscription approved)
      $ [ EventBeginElement (mkname namespace "presence")
            [ attr "from" from
            , attr "to" to
            , attr "type" $ if approved then "subscribed"
                                        else "unsubscribed" ]
        , EventEndElement (mkname namespace "presence")]

makePresenceStanza :: Text -> Maybe Text -> JabberShow -> IO Stanza
makePresenceStanza namespace mjid pstat = do
    stanzaFromList PresenceStatus { presenceShow = pstat
                                  , presencePriority = Nothing
                                  , presenceStatus = []
                                  , presenceWhiteList = []
                                  }
      $ [ EventBeginElement (mkname namespace "presence")
            (setFrom $ typ pstat) ]
        ++ (shw pstat >>= jabberShow) ++
        [ EventEndElement (mkname namespace "presence")]
 where
    setFrom = maybe id
                    (\jid -> (attr "from" jid :) )
                    mjid
    typ Offline = [attr "type" "unavailable"]
    typ _       = []
    shw ExtendedAway = ["xa"]
    shw Chatty       = ["chat"]
    shw Away         = ["away"]
    shw DoNotDisturb = ["dnd"]
    shw _            = []
    jabberShow stat =
      [ EventBeginElement "{jabber:client}show" []
      , EventContent (ContentText stat)
      , EventEndElement "{jabber:client}show" ]

makeRosterUpdate :: Text -> Text -> [(Name, Text)] -> IO Stanza
makeRosterUpdate tojid contact as = do
    let attrs = map (uncurry attr) as
    stanzaFromList Unrecognized
      [ EventBeginElement "{jabber:client}iq"
            [ attr "to"   tojid
            , attr "id"   "someid"
            , attr "type" "set"
            ]
      , EventBeginElement "{jabber:iq:roster}query" []
      , EventBeginElement "{jabber:iq:roster}item" (attr "jid" contact : attrs)
      , EventEndElement   "{jabber:iq:roster}item"
      , EventEndElement   "{jabber:iq:roster}query"
      , EventEndElement "{jabber:client}iq"
      ]

makePong :: Text -> Maybe Text -> Text -> Text -> [XML.Event]
makePong namespace mid to from =
       -- Note: similar to session reply
       [ EventBeginElement (mkname namespace "iq")
         $(case mid of
               Just c -> (("id",[ContentText c]):)
               _      -> id)
               [ attr "type" "result"
               , attr "to"   to
               , attr "from" from
               ]
       , EventEndElement (mkname namespace "iq")
       ]

data ClientOrPeer = IsClient | IsPeer

xmppInbound :: ConnectionData
                -> XMPPServerParameters -- ^ XXX: unused
                -> (Text, IO Text, IO Text, TChan Stanza -> StanzaOrigin)
                -> FlagCommand  -- ^ action to check whether the connection needs a ping (XXX: unused)
                -> TChan Stanza -- ^ channel to announce incoming stanzas on
                -> TChan Stanza -- ^ channel used to send stanzas
                -> TMVar ()     -- ^ mvar that is filled when the connection quits
                -> ConduitM Event o IO ()
xmppInbound cdta xmpp (namespace,tellmyname,tellyourname,mkorigin) pingflag stanzas output donevar = doNestingXML $ do
    withXML $ \begindoc -> do
    when (begindoc==EventBeginDocument) $ do
    whenJust nextElement $ \xml -> do
    withJust (elementAttrs "stream" xml) $ \stream_attrs -> do
    -- liftIO $ dput XMisc $ "STREAM ATTRS "++show stream_attrs
    let stream_name   = lookupAttrib "to"   stream_attrs
        stream_remote = lookupAttrib "from" stream_attrs
     -- xmpp_version = lookupAttrib "version" stream_attrs
    liftIO $ atomically $ writeTVar (cdRemoteName cdta) stream_remote
    fix $ \loop -> do
    -- liftIO . wlog $ "waiting for stanza."
    (chan,clsrs) <- liftIO . atomically $
        liftM2 (,) newLockedChan (newTVar (Just []))
    whenJust nextElement $ \stanzaTag -> do
        stanza_lvl <- nesting
        liftIO . atomically $ do
            writeLChan chan stanzaTag
            modifyTVar' clsrs (fmap (closerFor stanzaTag:))
        copyToChannel id chan clsrs .| do
          let mid   = lookupAttrib "id"   $ tagAttrs stanzaTag
              mfrom = lookupAttrib "from" $ tagAttrs stanzaTag
              mto   = lookupAttrib "to"   $ tagAttrs stanzaTag
          dispatch <- grokStanza namespace stanzaTag
          let unrecog = do
                let stype = Unrecognized
                s <- liftIO . atomically $ do
                      return Stanza
                              { stanzaType = stype
                              , stanzaId = mid
                              , stanzaTo = mto
                              , stanzaFrom = mfrom
                              , stanzaChan = chan
                              , stanzaClosers = clsrs
                              , stanzaInterrupt = donevar
                              , stanzaOrigin = mkorigin output
                              }
                ioWriteChan stanzas s
          you <- liftIO tellyourname
          me <- liftIO tellmyname
          fromMaybe unrecog $ dispatch <&> \dispatch ->
            case dispatch of
              -- Checking that the to-address matches this server.
              -- Otherwise it could be a client-to-client ping or a
              -- client-to-server for some other server.
              -- For now, assuming its for the immediate connection.
              Ping | mto==Just me || mto==Nothing -> do
                let pongto = maybe you id mfrom
                    pongfrom = maybe me id mto
                    pong = makePong namespace mid pongto pongfrom
                sendReply donevar Pong pong output
                do -- TODO: Remove this, it is only to generate a debug print
                   ioWriteChan stanzas Stanza
                            { stanzaType = Ping
                            , stanzaId = mid
                            , stanzaTo = mto
                            , stanzaFrom = mfrom
                            , stanzaChan = chan
                            , stanzaClosers = clsrs
                            , stanzaInterrupt = donevar
                            , stanzaOrigin = mkorigin output
                            }
              stype -> ioWriteChan stanzas Stanza
                            { stanzaType      = case stype of
                                RequestResource _ rsc -> RequestResource stream_name rsc
                                _                     -> stype
                            , stanzaId        = mid
                            , stanzaTo        = mto
                            , stanzaFrom      = mfrom
                            , stanzaChan      = chan
                            , stanzaClosers   = clsrs
                            , stanzaInterrupt = donevar
                            , stanzaOrigin    = mkorigin output
                            }
          awaitCloser stanza_lvl
        liftIO . atomically $ writeTVar clsrs Nothing
        loop


while :: IO Bool -> IO a -> IO [a]
while cond body = do
    b <- cond
    if b then do x <- body
                 xs <- while cond body
                 return (x:xs)
         else return []

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


streamFeatures :: Text -> [XML.Event]
streamFeatures "jabber:client" =
    [ EventBeginElement (streamP "features") []
    , EventBeginElement "{urn:ietf:params:xml:ns:xmpp-bind}bind" []
    , EventEndElement "{urn:ietf:params:xml:ns:xmpp-bind}bind"

    {-
    -- , "  <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>"
    , " <mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>"
    -- , " <mechanism>DIGEST-MD5</mechanism>"
    , " <mechanism>PLAIN</mechanism>"
    , " </mechanisms> "
    -}

    , EventEndElement (streamP "features")
    ]
streamFeatures "jabber:server" =
    []


greet' :: Text -> Text -> [XML.Event]
greet' namespace host = EventBeginDocument : greet'' namespace host

greet'' :: Text -> Text -> [Event]
greet'' namespace host =
    [ EventBeginElement (streamP "stream")
        [("from",[ContentText host])
        ,("id",[ContentText "someid"])
        ,("xmlns",[ContentText namespace])
        ,("xmlns:stream",[ContentText "http://etherx.jabber.org/streams"])
        ,("version",[ContentText "1.0"])
        ]
    ] ++ streamFeatures namespace

consid :: Maybe Text -> [(Name, [Content])] -> [(Name, [Content])]
consid Nothing = id
consid (Just sid) = (("id",[ContentText sid]):)


data XMPPState
    = PingSlot
 deriving (Eq,Ord)

makePing :: Text -> Maybe Text -> Text -> Text -> [XML.Event]
makePing namespace mid to from =
       [ EventBeginElement (mkname namespace "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 $ mkname namespace "iq"]

iq_bind_reply :: Maybe Text -> Text -> [XML.Event]
iq_bind_reply mid jid =
    [ EventBeginElement "{jabber:client}iq" (consid mid [("type",[ContentText "result"])])
    , EventBeginElement "{urn:ietf:params:xml:ns:xmpp-bind}bind"
        [("xmlns",[ContentText "urn:ietf:params:xml:ns:xmpp-bind"])]
    , EventBeginElement "{urn:ietf:params:xml:ns:xmpp-bind}jid" []
    , EventContent (ContentText jid)
    , EventEndElement "{urn:ietf:params:xml:ns:xmpp-bind}jid"
    , EventEndElement  "{urn:ietf:params:xml:ns:xmpp-bind}bind"
    , EventEndElement "{jabber:client}iq"

    {-
    -- query for client version
    , EventBeginElement "{jabber:client}iq"
                            [ attr "to" jid
                            , attr "from" hostname
                            , attr "type" "get"
                            , attr "id" "version"]
    , EventBeginElement "{jabber:iq:version}query" []
    , EventEndElement "{jabber:iq:version}query"
    , EventEndElement "{jabber:client}iq"
    -}
    ]

iq_session_reply :: Maybe Text -> Text -> [XML.Event]
iq_session_reply mid host =
    -- Note: similar to Pong
    [ EventBeginElement "{jabber:client}iq"
        (consid mid [("from",[ContentText host])
                    ,("type",[ContentText "result"])
                    ])
    , EventEndElement "{jabber:client}iq"
    ]

iq_service_unavailable :: Maybe Text -> Text -> XML.Name -> [XML.Event]
iq_service_unavailable mid host {- mjid -} req =
    [ EventBeginElement "{jabber:client}iq"
        (consid mid [attr "type" "error"
                    ,attr "from" host])
    , EventBeginElement req []
    , EventEndElement req
    , EventBeginElement "{jabber:client}error"
        [ attr "type" "cancel"
        , attr "code" "503" ]
    , EventBeginElement "{urn:ietf:params:xml:ns:xmpp-stanzas}service-unavailable" []
    , EventEndElement "{urn:ietf:params:xml:ns:xmpp-stanzas}service-unavailable"
    , EventEndElement "{jabber:client}error"
    , EventEndElement "{jabber:client}iq"
    ]


wrapStanzaList :: [XML.Event] -> STM [Either (StanzaWrap XML.Event) XML.Event]
wrapStanzaList xs = do
    wrap <- do
        clsrs <- newTVar Nothing
        donev <- newTMVar ()
        return $ \ x ->
            Stanza { stanzaType = Unrecognized
                   , stanzaId = mid
                   , stanzaTo = mto
                   , stanzaFrom = mfrom
                   , stanzaClosers = clsrs
                   , stanzaInterrupt = donev
                   , stanzaOrigin = LocalPeer
                   , stanzaChan = x
                   }
    return $ map (Left . wrap) (take 1 xs) ++ map Right (drop 1 xs)
  where
    m = listToMaybe xs
    mto = m >>= lookupAttrib "to" . tagAttrs
    mfrom = m >>= lookupAttrib "from" . tagAttrs
    mid = m >>= lookupAttrib "id" . tagAttrs

wrapStanzaConduit :: Monad m => StanzaWrap a -> ConduitM Event (Either (StanzaWrap Event) Event) m ()
wrapStanzaConduit stanza = do
    mfirst <- await
    forM_ mfirst $ \first -> do
    yield . Left $ stanza { stanzaChan = first }
    awaitForever $ yield . Right



{-
greet namespace =
    [ EventBeginDocument
    , EventBeginElement (streamP "stream")
        [ attr "xmlns"   namespace
        , attr "version" "1.0"
        ]
    ]
-}

goodbye :: [XML.Event]
goodbye =
    [ EventEndElement (streamP "stream")
    , EventEndDocument
    ]

simulateChatError :: StanzaError -> Maybe Text -> [Event]
simulateChatError err mfrom =
    [ EventBeginElement "{jabber:client}message"
         ((maybe id (\t->(attr "from" t:)) mfrom)
           [attr "type" "normal" ])
    , EventBeginElement "{jabber:client}body" []
    , EventContent $ ContentText ("/me " <> errorText err)
    , EventEndElement "{jabber:client}body"
    , EventBeginElement "{http://jabber.org/protocol/xhtml-im}html" []
      , EventBeginElement "{http://www.w3.org/1999/xhtml}body" []
        , EventBeginElement "{http://www.w3.org/1999/xhtml}p"
             [ attr "style" "font-weight:bold; color:red"
             ]
        , EventContent $ ContentText ("/me " <> errorText err)
        , EventEndElement "{http://www.w3.org/1999/xhtml}p"
      , EventEndElement "{http://www.w3.org/1999/xhtml}body"
    , EventEndElement "{http://jabber.org/protocol/xhtml-im}html"
    , EventEndElement "{jabber:client}message"
    ]


-- | Create a friend-request stanza.
presenceSolicitation :: Text -- ^ JID of sender making request.
                     -> Text -- ^ JID of recipient who needs to approve it.
                     -> IO Stanza
presenceSolicitation = presenceStanza (PresenceRequestSubscription True) "subscribe"

presenceProbe :: Text -> Text -> IO Stanza
presenceProbe = presenceStanza PresenceRequestStatus "probe"

presenceStanza :: StanzaType -> Text -> Text -> Text -> IO Stanza
presenceStanza stanza_type type_attr me jid =
    stanzaFromList stanza_type
        [ EventBeginElement "{jabber:server}presence"
                [ attr "to" jid
                , attr "from" me
                , attr "type" type_attr
                ]
        , EventEndElement "{jabber:server}presence" ]

slotsToSource ::
    Slotted.UpdateStream XMPPState (Either (StanzaWrap XML.Event) XML.Event)
    -> TVar Int
    -> TVar (Maybe (StanzaWrap XML.Event))
    -> TVar Bool
    -> TMVar ()
    -> ConduitT () (Flush XML.Event) IO ()
slotsToSource slots nesting lastStanza needsFlush rdone =
    fix $ \slot_src -> join . lift . atomically $ foldr1 orElse
                [Slotted.pull slots >>= \x -> do
                    x <- case x of
                            Left wrapped -> do
                                writeTVar nesting 1
                                writeTVar lastStanza (Just wrapped)
                                return $ stanzaChan wrapped
                            Right x      -> do
                                when (isEventBeginElement x)
                                    $ modifyTVar' nesting (+1)
                                when (isEventEndElement x) $ do
                                    n <- readTVar nesting
                                    when (n==1) $ writeTVar lastStanza Nothing
                                    modifyTVar' nesting (subtract 1)
                                return x
                    writeTVar needsFlush True
                    return $ do
                    -- liftIO $ wlog $ "yielding Chunk: " ++ show x
                    yield (Chunk x)
                    slot_src
                ,do Slotted.isEmpty slots >>= check
                    readTVar needsFlush >>= check
                    writeTVar needsFlush False
                    return $ do
                    -- liftIO $ wlog "yielding Flush"
                    yield Flush
                    slot_src
                ,readTMVar rdone >> return (return ())
                ]

forkConnection :: Server PeerAddress ConnectionData releaseKey XML.Event
                -> XMPPServerParameters
                -> PeerAddress -- SockAddr (XXX(what?): remote for peer, local for client)
                -> ConnectionData
                -> FlagCommand
                -> ConduitT () XML.Event IO ()
                -> ConduitT (Flush XML.Event) Void IO ()
                -> TChan Stanza
                -> MVar ()
                -> IO (TChan Stanza)
forkConnection sv xmpp saddr cdta pingflag src snk stanzas pp_mvar = do
    let auxAddr = cdAddr cdta
        clientOrServer@(namespace,tellmyname,telltheirname,_) = case auxAddr of
            Right _    -> ("jabber:client", xmppTellMyNameToClient xmpp (ClientAddress $ peerAddress saddr)
                                          , xmppTellClientHisName xmpp (ClientAddress $ peerAddress saddr)
                                          , ClientOrigin (ClientAddress $ peerAddress saddr))
            Left laddr -> ("jabber:server", xmppTellMyNameToPeer xmpp laddr
                                          , xmppTellPeerHisName xmpp saddr
                                          , PeerOrigin saddr)
    me <- tellmyname
    rdone <- atomically newEmptyTMVar
    let isStarter (Left _) = True
        isStarter (Right e) | isEventBeginElement e = True
        isStarter _ = False
        isStopper (Left _) = False
        isStopper (Right e) | isEventEndElement e = True
        isStopper _ = False
    slots <- atomically $ Slotted.new isStarter isStopper
    needsFlush <- atomically $ newTVar False
    lastStanza <- atomically $ newTVar Nothing
    nesting <- atomically $ newTVar 0
    let _ = slots :: Slotted.UpdateStream XMPPState (Either (StanzaWrap XML.Event) XML.Event)
    let greet_src = do
            CL.sourceList (greet' namespace me) .| CL.map Chunk
            yield Flush
        slot_src = slotsToSource slots nesting lastStanza needsFlush rdone
    -- client.PeerAddress {peerAddress = [::1]:5222}
    let lbl n = concat [ n
                       , Text.unpack (Text.drop 7 namespace) -- "client" or "server"
                       , "."
                       , case cdProfile cdta of
                            _ | Right _ <- cdAddr cdta -> show saddr
                            "."                        -> show saddr
                            mytoxname                  -> show saddr {- TODO: remote tox peer name? -} ]

    forkIO $ do myThreadId >>= flip labelThread (lbl "xmpp-post.")
                -- This thread handles messages after they are pulled out of
                -- the slots-queue.  Hence, xmpp-post, for post- slots-queue.

                -- Read all slots-queued XML events or stanzas and yield them
                -- upstream.  This should continue until the connection is
                -- closed.
                runConduit $ (greet_src >> slot_src) .| snk

                -- Connection is now closed.  Here we handle any unsent stanzas.
                last <- atomically $ readTVar lastStanza
                es <- while (atomically . fmap not $ Slotted.isEmpty slots)
                            (atomically . Slotted.pull $ slots)
                let es' = mapMaybe metadata es -- We only care about full stanzas.
                    metadata (Left s) = Just s
                    metadata _        = Nothing
                -- TODO: Issuing RecipientUnavailable for all errors is a presence leak
                --          and protocol violation
                -- TODO: IDMangler can be used for better targetted error delivery.
                let fail stanza = do
                            wlog $ "failed delivery: " ++ show (stanzaId stanza)
                            quitVar <- atomically newEmptyTMVar
                            reply <- makeErrorStanza stanza
                            tag <- stanzaFirstTag stanza
                            -- sendReply quitVar (Error RecipientUnavailable tag) reply replyto
                            replystanza <- stanzaFromList (Error RecipientUnavailable tag) reply
                            xmppDeliverMessage xmpp (wlog $ "discarded error delivery fail") replystanza
                    notError s = case stanzaType s of
                                    Error {} -> False
                                    _        -> True
                -- TODO: Probably some stanzas should be queued or saved for re-connect.
                mapM_ fail $ filter notError (maybeToList last ++ es')
                wlog $ "end xmpp-post fork: " ++ (lbl "")

    output <- atomically newTChan
    hacks <- atomically $ newTVar Map.empty
    msgids <- atomically $ newTVar []
    forkIO $ do
        -- Here is the pre- slots-queue thread which handles messages as they
        -- arrive and assigns slots to them if that is appropriate.

        -- mapM_ (atomically . Slotted.push slots Nothing) greetPeer
        myThreadId >>= flip labelThread (lbl "xmpp-pre.")

        verbosity <- xmppVerbosity xmpp
        fix $ \loop -> do
            what <- atomically $ foldr1 orElse
                [readTChan output >>= \stanza -> return $ do
                    wantStanzas <- getVerbose XJabber
                    let notping f
                            | not wantStanzas = return ()
                            | (verbosity==1)  = case stanzaType stanza of Pong -> return ()
                                                                          _ -> f
                            | (verbosity>=2)  = f
                            | otherwise       = return ()
                    -- isempty <- atomically $ isEmptyTChan (stanzaChan stanza)
                    -- kwlog $ "queuing: "++show (isempty, stanzaId stanza)
                    notping $ do
                        dup <- cloneStanza stanza
                        let typ = Strict8.pack $ c ++ "<-"++(concat . take 1 . words $ show (stanzaType dup))++" "
                            c = case auxAddr of
                                    Right _ -> "C"
                                    Left  _ -> "P"
                        wlog ""
                        liftIO $ takeMVar pp_mvar
                        runConduit $ stanzaToConduit dup .| prettyPrint typ
                        liftIO $ putMVar pp_mvar ()
                    -- wlog $ "hacks: "++show (stanzaId stanza)
                    case stanzaType stanza of
                        InternalEnableHack hack -> do
                            -- wlog $ "enable hack: " ++ show hack
                            atomically $ modifyTVar' hacks (Map.insert hack ())
                        InternalCacheId x -> do
                            -- wlog $ "cache id thread: " ++ show x
                            atomically $ modifyTVar' msgids (take 3 . (x:))
                        _ -> return ()
                    runConduit $ stanzaToConduit stanza .| wrapStanzaConduit stanza
                        .| awaitForever
                            -- TODO: PresenceStatus stanzas should be pushed to appropriate slots
                            (liftIO . atomically . Slotted.push slots Nothing)
                    case stanzaType stanza of
                        Error err tag | tagName tag=="{jabber:client}message" -> do
                            wlog $ "handling Error hacks"
                            b <- atomically $ do m <- readTVar hacks
                                                 cached <- readTVar msgids
                                                 fromMaybe (return False) $ stanzaId stanza <&> \id' -> do
                                                 return $ Map.member SimulatedChatErrors m
                                                            && elem id' cached
                            ids <- atomically $ readTVar msgids
                            wlog $ "ids = " ++ show (b,stanzaId stanza, ids)
                            when b $ do
                            let sim = simulateChatError err (stanzaFrom stanza)
                            wlog $ "sending simulated chat for error message."
                            runConduit $ CL.sourceList sim .| wrapStanzaConduit stanza -- not quite right, but whatever
                                .| awaitForever
                                    (liftIO . atomically . Slotted.push slots Nothing)
                        Error e _ -> do
                            wlog $ "no hacks for error: " ++ show e
                        _ -> return ()
                    loop
                ,do pingflag >>= check
                    return $ do
                    to <- telltheirname
                    let from = me -- Look it up from Server object
                                  -- or pass it with Connection event.
                        mid = Just "ping"
                        ping0 = makePing namespace mid to from
                    ping <- atomically $ wrapStanzaList ping0
                    mapM_ (atomically . Slotted.push slots (Just $ PingSlot))
                          ping
                    wlog ""
                    runConduit $ CL.sourceList ping0 .| prettyPrint (case auxAddr of
                        Right _ -> "C<-Ping"
                        Left  _ -> "P<-Ping ")
                    loop
                ,readTMVar rdone >> return (return ())
                ]
            what
        wlog $ "end xmpp-pre fork: " ++ show (lbl "")
    forkIO $ do
        myThreadId >>= flip labelThread (lbl "xmpp-reader.")
        -- src $$ awaitForever (lift . putStrLn . takeWhile (/=' ') . show)
        runConduit $ src .| xmppInbound cdta xmpp clientOrServer pingflag stanzas output rdone
        atomically $ putTMVar rdone ()
        wlog $ "end reader fork: " ++ lbl ""
    return output

{-
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 :: SocketLike sock => Maybe SockAddr -> sock -> IO (PeerAddress,ConnectionData)
peerKey bind_addr sock = do
    laddr <- getSocketName sock
    raddr <-
      sIsConnected sock >>= \c ->
        if c then getPeerName sock -- addr is normally socketName
             else return laddr     -- Weird hack: addr is would-be peer name
    -- Assume remote peers are listening on the same port that we do.
    let peerport = fromIntegral $ fromMaybe 5269 $ do
                        p <- bind_addr >>= sockAddrPort
                        guard (p /= 0) -- Make sure we never use port 0 because it is used
                                       -- to distinguish fake address connection keys.
                        return p
    rname <- atomically $ newTVar Nothing
    -- dput XMan $ "peerKey " ++ show (PeerAddress $ raddr `withPort` peerport,laddr)
    return $ ( PeerAddress $ raddr `withPort` peerport
             , ConnectionData { cdAddr       = Left (Local laddr)
                              , cdType       = XMPP
                              , cdProfile    = "."
                              , cdRemoteName = rname } )

clientKey :: SocketLike sock => sock -> IO (PeerAddress,ConnectionData)
clientKey sock = do
    laddr <- getSocketName sock -- [::1]:5222  bind address, same for all clients
    raddr <- getPeerName sock   -- [::1]:????? unique key
    when (Just 0 == sockAddrPort raddr) $ do
        dput XMan $ unwords [ "BUG: XMPP Client"
                            , show (laddr,raddr)
                            , "is using port zero.  This could interfere"
                            , "with Tox peer sessions." ]
    rname <- atomically $ newTVar Nothing
    -- dput XMan $ "clientKey " ++ show (PeerAddress laddr,raddr)
    return $ ( PeerAddress raddr -- Actually a ClientAddress, but _xmpp_sv conkey type is PeerAddress.
             , ConnectionData { cdAddr       = Right (Remote raddr) -- FIXME: This is a bad way to detect client/peer.
                              , cdType       = XMPP
                              , cdProfile    = "."
                              , cdRemoteName = rname } )


xmlifyRosterItems :: Monad m => Set Text -> Text -> Set Text -> ConduitM i Event m ()
xmlifyRosterItems solicited stype set = mapM_ item (Set.toList set)
 where
  item jid = do yield $ EventBeginElement "{jabber:iq:roster}item"
                        ([ attr "jid" jid
                         , attr "subscription" stype
                         ]++if Set.member jid solicited
                             then [attr "ask" "subscribe"]
                             else [] )
                yield $ EventEndElement "{jabber:iq:roster}item"

sendRoster ::
    StanzaWrap a
    -> XMPPServerParameters
    -> ClientAddress
    -> TChan Stanza
    -> IO ()
sendRoster query xmpp clientKey replyto = do
    let maddr = case stanzaOrigin query of
             ClientOrigin addr _ -> Just addr
             PeerOrigin {}       -> Nothing -- remote peer requested roster?
             LocalPeer           -> Nothing -- local peer requested roster?
    forM_ maddr $ \k -> do
    hostname <- xmppTellMyNameToClient xmpp clientKey
    let getlist f = do
            bs <- f xmpp k
            return (Set.fromList bs) -- js)
    buddies     <- getlist xmppRosterBuddies
    subscribers <- getlist xmppRosterSubscribers
    solicited   <- getlist xmppRosterSolicited
    subnone0    <- getlist xmppRosterOthers
    jid <- xmppTellClientHisName xmpp k -- LookupClientJID xmpp k
    let subnone = Set.union solicited subnone0 \\ Set.union buddies subscribers
    let subto = buddies \\ subscribers
    let subfrom = subscribers \\ buddies
    let subboth = Set.intersection buddies subscribers
    let roster = do
            yield $ EventBeginElement "{jabber:client}iq"
                        (consid (stanzaId query)
                            [ attr "to" jid
                            , attr "type" "result" ])
            yield $ EventBeginElement "{jabber:iq:roster}query" [] -- todo: ver?
            xmlifyRosterItems solicited "to" subto
            xmlifyRosterItems solicited "from" subfrom
            xmlifyRosterItems solicited "both" subboth
            xmlifyRosterItems solicited "none" subnone
            yield $ EventEndElement "{jabber:iq:roster}query"
            yield $ EventEndElement "{jabber:client}iq"

    conduitToStanza Roster
                    (stanzaId query)
                    Nothing
                    (Just jid)
                    roster >>= ioWriteChan replyto
    {-
    let debugpresence =
                [ EventBeginElement "{jabber:client}presence"
                    [ attr "from" "guest@oxio4inifatsetlx.onion"
                    , attr "to" jid]
                , EventEndElement "{jabber:client}presence"
                ]
    quitvar <- atomically newEmptyTMVar
    sendReply quitvar Unrecognized debugpresence replyto
    -}


socketFromKey :: Server PeerAddress ConnectionData releaseKey XML.Event -> ClientAddress -> IO (Remote SockAddr)
socketFromKey sv (ClientAddress addr) = do
    map <- atomically $ readTVar (conmap sv)
    let mcd = Map.lookup (PeerAddress addr) map
        oops = Remote addr -- No connection data, so using incorrect address.
    case mcd of
        Nothing -> return oops
        Just cd -> return $ either (const oops) id $ cdAddr $ cdata cd

class StanzaFirstTag a where
    stanzaFirstTag :: StanzaWrap a -> IO XML.Event
instance StanzaFirstTag (TChan XML.Event) where
    stanzaFirstTag stanza = do
        e <-atomically $ peekTChan (stanzaChan stanza)
        return e
instance StanzaFirstTag (LockedChan XML.Event) where
    stanzaFirstTag stanza = do
        e <-atomically $ peekLChan (stanzaChan stanza)
        return e
instance StanzaFirstTag XML.Event where
    stanzaFirstTag stanza = return (stanzaChan stanza)

data StanzaError
    = BadRequest
    | Conflict
    | FeatureNotImplemented
    | Forbidden
    | Gone
    | InternalServerError
    | ItemNotFound
    | JidMalformed
    | NotAcceptable
    | NotAllowed
    | NotAuthorized
    | PaymentRequired
    | RecipientUnavailable
    | Redirect
    | RegistrationRequired
    | RemoteServerNotFound
    | RemoteServerTimeout
    | ResourceConstraint
    | ServiceUnavailable
    | SubscriptionRequired
    | UndefinedCondition
    | UnexpectedRequest
 deriving (Show,Enum,Ord,Eq)

xep0086 ::
    forall t t1. (Num t1, IsString t) => StanzaError -> (t, t1)
xep0086 e =
  case e of
    BadRequest            -> ("modify", 400)
    Conflict              -> ("cancel", 409)
    FeatureNotImplemented -> ("cancel", 501)
    Forbidden             -> ("auth", 403)
    Gone                  -> ("modify", 302)
    InternalServerError   -> ("wait", 500)
    ItemNotFound          -> ("cancel", 404)
    JidMalformed          -> ("modify", 400)
    NotAcceptable         -> ("modify", 406)
    NotAllowed            -> ("cancel", 405)
    NotAuthorized         -> ("auth", 401)
    PaymentRequired       -> ("auth", 402)
    RecipientUnavailable  -> ("wait", 404)
    Redirect              -> ("modify", 302)
    RegistrationRequired  -> ("auth", 407)
    RemoteServerNotFound  -> ("cancel", 404)
    RemoteServerTimeout   -> ("wait", 504)
    ResourceConstraint    -> ("wait", 500)
    ServiceUnavailable    -> ("cancel", 503)
    SubscriptionRequired  -> ("auth", 407)
    UndefinedCondition    -> ("", 500)
    UnexpectedRequest     -> ("wait", 400)

errorText :: StanzaError -> Text
errorText e =
 case e of
    BadRequest            -> "Bad request"
    Conflict              -> "Conflict"
    FeatureNotImplemented -> "This feature is not implemented"
    Forbidden             -> "Forbidden"
    Gone                  -> "Recipient can no longer be contacted"
    InternalServerError   -> "Internal server error"
    ItemNotFound          -> "Item not found"
    JidMalformed          -> "JID Malformed"
    NotAcceptable         -> "Message was rejected"
    NotAllowed            -> "Not allowed"
    NotAuthorized         -> "Not authorized"
    PaymentRequired       -> "Payment is required"
    RecipientUnavailable  -> "Recipient is unavailable"
    Redirect              -> "Redirect"
    RegistrationRequired  -> "Registration required"
    RemoteServerNotFound  -> "Recipient's server not found"
    RemoteServerTimeout   -> "Remote server timeout"
    ResourceConstraint    -> "The server is low on resources"
    ServiceUnavailable    -> "The service is unavailable"
    SubscriptionRequired  -> "A subscription is required"
    UndefinedCondition    -> "Undefined condition"
    UnexpectedRequest     -> "Unexpected request"

eventContent :: Maybe [Content] -> Text
eventContent cs = maybe "" (foldr1 (<>) . map content1) cs
            where content1 (ContentText t)   = t
                  content1 (ContentEntity t) = t

errorTagLocalName :: forall a. Show a => a -> Text
errorTagLocalName e = Text.pack . drop 1 $ do
    c <- show e
    if 'A' <= c && c <= 'Z'
    then [ '-', chr( ord c - ord 'A' + ord 'a') ]
    else return c

makeErrorStanza :: StanzaFirstTag a => StanzaWrap a -> IO [XML.Event]
makeErrorStanza stanza = do
    startTag <- stanzaFirstTag stanza
    let n = tagName startTag
        endTag = EventEndElement n
        amap0 = Map.fromList (tagAttrs startTag)
        mto   = Map.lookup "to" amap0
        mfrom = Map.lookup "from" amap0
        mtype = Map.lookup "type" amap0
        mid = Map.lookup "id" amap0
        amap1 = Map.alter (const mto) "from" amap0
        -- amap2 = Map.alter (const $ Just $ [ContentText "blackbird"]) {-mfrom)-} "to" amap1
        amap2 = Map.alter (const mfrom) "to" amap1
        amap3 = Map.insert "type" [XML.ContentText "error"] amap2
        startTag' = EventBeginElement
                        (tagName startTag)
                        (Map.toList amap3)
        -- err = Gone -- FeatureNotImplemented -- UndefinedCondition -- RecipientUnavailable
        err = RecipientUnavailable
        errname = n { nameLocalName = "error" }
        -- errattrs = [attr "type" "wait"] --  "modify"]
        errorAttribs e xs = ys ++ xs -- todo replace instead of append
            where (typ,code) = xep0086 e
                  ys = [attr "type" typ, attr "code" (Text.pack . show $ code)]
        errorTagName = Name { nameNamespace = Just "urn:ietf:params:xml:ns:xmpp-stanzas"
                            , nameLocalName = errorTagLocalName err
                            , namePrefix = Nothing }
        errattrs = errorAttribs err []
    let wlogd v s = do
            wlog $ "error "++show (lookupAttrib "id" $ tagAttrs startTag)++" " ++ v ++ " = " ++ show s
    {-
    wlogd "amap0" amap0
    wlogd "mto" mto
    wlogd "mfrom" mfrom
    wlogd "amap3" amap3
    -}
    if eventContent mtype=="error" then return [] else do
    return [ startTag'
           , EventBeginElement errname errattrs
           , EventBeginElement errorTagName []
           , EventEndElement errorTagName
           , EventEndElement errname
            {-
           , EventBeginElement "{jabber:client}body" []
           , EventContent (ContentText "what?")
           , EventEndElement "{jabber:client}body"
            -}
           {-
           , EventBeginElement "{154ae29f-98f2-4af4-826d-a40c8a188574}dummy" []
           , EventEndElement "{154ae29f-98f2-4af4-826d-a40c8a188574}dummy"
           -}
           , endTag
           ]

monitor ::
    Server PeerAddress ConnectionData releaseKey XML.Event
    -> ConnectionParameters PeerAddress ConnectionData
    -> XMPPServerParameters
    -> IO b
monitor sv params xmpp = do
    chan <- return $ serverEvent sv
    stanzas <- atomically newTChan
    quitVar <- atomically newEmptyTMVar
    pp_mvar <- newMVar () -- Lock for synchronous pretty-printing of stanzas in log.
    fix $ \loop -> do
    action <- atomically $ foldr1 orElse
      [ readTChan chan >>= \((addr,u),e) -> return $ do
        case e of
            Connection pingflag xsrc xsnk
                -> do wlog $ tomsg addr "Connection"
                      outs <- forkConnection sv xmpp addr u pingflag xsrc xsnk stanzas pp_mvar
                      -- /addr/ may be a peer or a client.  So we'll strip off
                      -- the PeerAddress constructor before exposing it.
                      xmppNewConnection xmpp (peerAddress addr) u outs
            ConnectFailure addr
                -> do return () -- wlog $ tomsg k "ConnectFailure"
            EOF -> do wlog $ tomsg addr "EOF"
                      -- /addr/ may be a peer or a client.  So we'll strip off
                      -- the PeerAddress constructor before exposing it.
                      xmppEOF xmpp (peerAddress addr) u
            HalfConnection In
                -> do wlog $ tomsg addr "ReadOnly"
                      case cdAddr u of
                        Left (Local _) -> control sv (Connect (peerAddress addr) params)
                        _              -> return () -- Don't call-back client connections.
            HalfConnection Out
                -> do wlog $ tomsg addr "WriteOnly"
            RequiresPing
                -> do return () -- wlog $ tomsg k "RequiresPing"
      , readTChan stanzas >>= \stanza -> return $ do
        {-
        dup <- case stanzaType stanza of
                -- Must dup anything that is going to be delivered...
                Message {} -> do
                    dup <- cloneStanza stanza -- dupped so we can make debug print
                    return dup
                Error {} -> do
                    dup <- cloneStanza stanza -- dupped so we can make debug print
                    return dup
                _ -> return stanza
        -}
        dup <- cloneStanza stanza

        forkIO $ do
            case stanzaOrigin stanza of
                ClientOrigin k replyto ->
                    case stanzaType stanza of
                        RequestResource clientsNameForMe wanted -> do
                            sockaddr <- socketFromKey sv k
                            rsc0 <- xmppChooseResourceName xmpp k sockaddr clientsNameForMe wanted
                            hostname <- xmppTellMyNameToClient xmpp k
                            let rsc = unsplitJID (n,hostname,r) where (n,_,r) = splitJID rsc0
                            let reply = iq_bind_reply (stanzaId stanza) rsc
                            -- sendReply quitVar SetResource reply replyto
                            let requestVersion :: ConduitT i XML.Event IO ()
                                requestVersion = do
                                  yield $ EventBeginElement "{jabber:client}iq"
                                              [ attr "to" rsc
                                              , attr "from" hostname
                                              , attr "type" "get"
                                              , attr "id" "version"]
                                  yield $ EventBeginElement "{jabber:iq:version}query" []
                                  yield $ EventEndElement "{jabber:iq:version}query"
                                  yield $ EventEndElement "{jabber:client}iq"
                                  {-
                                  -- XXX Debug chat:
                                  yield $ EventBeginElement "{jabber:client}message"
                                          [ attr "from" $ eventContent (Just [ContentText rsc])
                                          , attr "type" "normal" ] -- "blackbird" ]
                                  yield $ EventBeginElement "{jabber:client}body" []
                                  yield $ EventContent $ ContentText ("hello?")
                                  yield $ EventEndElement "{jabber:client}body"
                                  yield $ EventEndElement "{jabber:client}message"
                                  -}
                            sendReply quitVar SetResource reply replyto
                            conduitToStanza (UnrecognizedQuery "{jabber:iq:version}query")
                                  Nothing -- id
                                  (Just hostname) -- from
                                  (Just rsc) -- to
                                  requestVersion
                              >>= ioWriteChan replyto
                        SessionRequest -> do
                            me <- xmppTellMyNameToClient xmpp k
                            let reply = iq_session_reply (stanzaId stanza) me
                            sendReply quitVar Pong reply replyto
                        RequestRoster -> do
                            sendRoster stanza xmpp k replyto
                            xmppSubscribeToRoster xmpp k
                        PresenceStatus {} -> do
                            xmppInformClientPresence xmpp k stanza
                        PresenceRequestSubscription {} -> do
                            let fail = return () -- todo
                            xmppClientSubscriptionRequest xmpp fail k stanza replyto
                        PresenceInformSubscription {} -> do
                            let fail = return () -- todo
                            xmppClientInformSubscription xmpp fail k stanza
                        NotifyClientVersion name version -> do
                            enableClientHacks name version replyto
                        UnrecognizedQuery query -> do
                            me <- xmppTellMyNameToClient xmpp k
                            let reply = iq_service_unavailable (stanzaId stanza) me query
                            sendReply quitVar (Error ServiceUnavailable (head reply)) reply replyto
                        Message {} -> do
                            -- wlog $ "LANGMAP "++show (stanzaId stanza, msgLangMap (stanzaType stanza))
                            maybe (return ()) (flip cacheMessageId replyto) $ do
                                guard . not . null . mapMaybe (msgBody . snd) $ msgLangMap (stanzaType stanza)
                                stanzaId stanza
                        _ -> return ()
                PeerOrigin k replyto ->
                    case stanzaType stanza of
                        PresenceRequestStatus {} -> do
                            xmppAnswerProbe xmpp k stanza replyto
                        PresenceStatus {} -> do
                            xmppInformPeerPresence xmpp k stanza
                        PresenceRequestSubscription {} -> do
                            let fail = return () -- todo
                            xmppPeerSubscriptionRequest xmpp fail k stanza replyto
                        PresenceInformSubscription {} -> do
                            let fail = return () -- todo
                            xmppPeerInformSubscription xmpp fail k stanza
                        _ -> return ()
                _ -> return ()
            let deliver replyto = do
                    -- TODO: Issuing RecipientUnavailable for all errors is a presence leak
                    --          and protocol violation
                    let fail = do
                            wlog $ "Failed delivery id="++show (stanzaId stanza) -- TODO
                            reply <- makeErrorStanza stanza
                            tag <- stanzaFirstTag stanza
                            sendReply quitVar (Error RecipientUnavailable tag) reply replyto
                    xmppDeliverMessage xmpp fail stanza
                    -- -- bad idea:
                    -- let newStream = greet'' "jabber:client" "blackbird"
                    -- sendReply quitVar Error newStream replyto
            case stanzaType stanza of
                Message {} -> do
                  case stanzaOrigin stanza of
                    LocalPeer {} -> return ()
                    ClientOrigin _ replyto -> deliver replyto
                    PeerOrigin   _ replyto -> deliver replyto
                Error {} -> do
                  case stanzaOrigin stanza of
                    LocalPeer {} -> return ()
                    ClientOrigin _ replyto -> deliver replyto
                    PeerOrigin   _ replyto -> deliver replyto
                _ -> return ()
        -- We need to clone in the case the stanza is passed on as for Message.
        wantStanzas <- getVerbose XJabber
        verbosity <- xmppVerbosity xmpp
        let notping f | not wantStanzas = return ()
                      | (verbosity==1)  = case stanzaType stanza of Pong -> return ()
                                                                    _    -> f
                      | (verbosity>=2)  = f
                      | otherwise       = return ()
        notping $ do
        let typ = Strict8.pack $ c ++ "->"++(concat . take 1 . words $ show (stanzaType stanza))++" "
            c = case stanzaOrigin stanza of
                    LocalPeer       -> "*"
                    ClientOrigin {} -> "C"
                    PeerOrigin {}   -> "P"
        wlog ""
        liftIO $ takeMVar pp_mvar
        runConduit $ stanzaToConduit dup .| prettyPrint typ
        liftIO $ putMVar pp_mvar ()
      ]
    action
    loop
 where
    tomsg k str =  printf "%12s %s" str (show k)
        where
            _ = str :: String

data ConnectionType = XMPP | Tox
    deriving (Eq,Ord,Enum,Show,Read)

data ConnectionData = ConnectionData
    { cdAddr :: Either (Local SockAddr)  -- Peer connection local address
                       (Remote SockAddr) -- unused, todo:remove. (was client connection remote address).
    , cdType    :: ConnectionType
    , cdProfile :: Text -- Currently ignored for clients.  Instead, see
                        -- 'clientProfile' field of 'ClientState'.
                        --
                        -- For peers: "." for XMPP, otherwise the ".tox" hostname
                        --  of this local node.

      -- Initially Nothing, when the remote end identifies itself by a given name,
      -- the result will be stored here.
    , cdRemoteName :: TVar (Maybe Text)
    }

addrToPeerKey :: Remote SockAddr -> PeerAddress
addrToPeerKey (Remote raddr) = PeerAddress raddr

addrFromClientKey :: ClientAddress -> Local SockAddr
addrFromClientKey (ClientAddress laddr) = Local laddr

classifyConnection :: SockAddr -> ConnectionData -> Either (PeerAddress, Local SockAddr)
                                                           (ClientAddress, Remote SockAddr)
classifyConnection saddr dta = case cdAddr dta of
    Left  laddr -> Left  (PeerAddress saddr, laddr)
    Right raddr -> Right (ClientAddress saddr, raddr)

data XMPPServer
    = forall releaseKey.
      XMPPServer { _xmpp_sv          :: Server PeerAddress ConnectionData releaseKey XML.Event
                                        -- ^ Internally, we're using PeerAddress for both clients
                                        -- and peers.  For the external interface, we mark client
                                        -- addresses as 'ClientAddress' and not 'PeerAddress'.
                 , _xmpp_man         :: Connection.Manager TCPStatus Text
                 , _xmpp_peer_params :: ConnectionParameters PeerAddress ConnectionData
                 , _xmpp_peer_bind   :: SockAddr
                 }

xmppConnections :: XMPPServer -> IO (Connection.Manager TCPStatus Text)
xmppConnections xsv@XMPPServer{_xmpp_man = m} = return m

xmppEventChannel :: XMPPServer -> TChan ((PeerAddress, ConnectionData), ConnectionEvent Event)
xmppEventChannel XMPPServer{_xmpp_sv=sv} = serverEvent sv

quitXmpp :: XMPPServer -> IO ()
quitXmpp XMPPServer{_xmpp_sv=sv} = control sv Quit

xmppServer :: MonadIO m => Allocate releaseKey m
                        -> Maybe SockAddr -- ^ Listen address for server-to-server protocol.
                        -> m XMPPServer
xmppServer allocate bind_addr = do
    sv <- server allocate xmlStream
    liftIO $ do
        gen <- System.Random.getStdGen
        peer_bind <- maybe (getBindAddress "5269" True) return bind_addr
        let (r,gen') = System.Random.next gen
            fuzz = r `mod` 2000 -- maximum 2 seconds of ping fuzz
            peer_params :: ConnectionParameters PeerAddress ConnectionData
            peer_params = (connectionDefaults $ peerKey $ Just peer_bind)
                              { pingInterval = 15000 + fuzz
                              , timeout      = 2000
                              , duplex       = False }
        tcp <- tcpManager (\(PeerAddress addr) -> (addr, peer_params, 10000)) sv
        return XMPPServer { _xmpp_sv          = sv
                          , _xmpp_man         = tcp
                          , _xmpp_peer_params = peer_params
                          , _xmpp_peer_bind   = peer_bind
                          }

forkXmpp :: MonadIO m => XMPPServer -> XMPPServerParameters -> m ThreadId
forkXmpp XMPPServer { _xmpp_sv          = sv
                    , _xmpp_peer_params = peer_params
                    , _xmpp_peer_bind   = peer_bind
                    }
         xmpp = liftIO $ do
    let client_params :: ConnectionParameters PeerAddress ConnectionData
        client_params = (connectionDefaults clientKey)
                              { pingInterval = 0
                              , timeout      = 0
                              }
    mt <- forkIO $ do myThreadId >>= flip labelThread ("XMPP.monitor")
                      monitor sv peer_params xmpp
    dput XMisc $ "Starting peer listen"
    control sv (Listen peer_bind peer_params)
    dput XMisc $ "Starting client listen"
    client_bind <- maybe (getBindAddress "5222" True) return $ xmppClientBind xmpp
    control sv (Listen client_bind client_params)
    return mt


#if MIN_VERSION_stm(2,4,0)
#else
-- |Clone a 'TChan': similar to dupTChan, but the cloned channel starts with the
-- same content available as the original channel.
--
-- Terrible inefficient implementation provided to build against older libraries.
cloneTChan :: TChan a -> STM (TChan a)
cloneTChan chan = do
    contents <- chanContents' chan
    chan2 <- dupTChan chan
    mapM_ (writeTChan chan) contents
    return chan2
 where
    chanContents' chan = do
        b <- isEmptyTChan chan
        if b then return [] else do
        x <- readTChan chan
        xs <- chanContents' chan
        return (x:xs)
#endif