{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE FlexibleInstances #-} -- instance for TChan Event
{-# LANGUAGE DoAndIfThenElse #-}
module XMPPServer
    ( xmppServer
    , ConnectionKey(..)
    , XMPPServerParameters(..)
    , XMPPServer
    , addPeer
    , StanzaWrap(..)
    , Stanza(..)
    , StanzaType(..)
    , StanzaOrigin(..)
    , cloneStanza
    , LangSpecificMessage(..)
    , peerKeyToText
    , addrToText
    , sendModifiedStanzaToPeer
    , sendModifiedStanzaToClient
    , presenceProbe
    , presenceSolicitation
    , makePresenceStanza
    , makeInformSubscription
    , makeRosterUpdate
    , makeMessage
    , JabberShow(..)
    ) where

import Debug.Trace
import System.IO (hFlush,stdout)
import Control.Monad.Trans.Resource
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 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.Int (Int8)

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 hiding (content)
import qualified Text.XML.Stream.Parse as XML
import Data.XML.Types as XML
import Data.Maybe
import Data.List (nub)
import Data.Monoid ( (<>) )
import Data.Text (Text)
import qualified Data.Text as Text (pack,unpack,words,intercalate)
import Data.Char (toUpper,chr,ord)
import Data.Map (Map)
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 System.Endian (toBE32)

import ConnectionKey
import qualified Control.Concurrent.STM.UpdateStream as Slotted
import Nesting
import Server
import EventUtil
import ControlMaybe
import LockedChan
import PeerResolve
import Blaze.ByteString.Builder (Builder)

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)
    | 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 | NetworkOrigin ConnectionKey (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)

data XMPPServerParameters =
    XMPPServerParameters
    { xmppChooseResourceName :: ConnectionKey -> SockAddr -> Maybe Text -> IO Text
    , xmppTellMyNameToClient :: IO Text
    , xmppTellMyNameToPeer :: SockAddr -> IO Text
    , xmppTellClientHisName :: ConnectionKey -> IO Text
    , xmppTellPeerHisName :: ConnectionKey -> IO Text
    , xmppNewConnection :: ConnectionKey -> SockAddr -> TChan Stanza -> IO ()
    , xmppEOF :: ConnectionKey -> IO ()
    , xmppRosterBuddies      :: ConnectionKey -> IO [Text]
    , xmppRosterSubscribers  :: ConnectionKey -> IO [Text]
    , xmppRosterSolicited    :: ConnectionKey -> IO [Text]
    , xmppRosterOthers       :: ConnectionKey -> IO [Text]
    , xmppSubscribeToRoster :: ConnectionKey -> IO ()
    -- , xmppLookupClientJID :: ConnectionKey -> IO Text
    , xmppTellClientNameOfPeer :: ConnectionKey -> [Text] -> IO Text
    , xmppDeliverMessage :: (IO ()) -> Stanza -> IO ()
    , xmppInformClientPresence :: ConnectionKey -> Stanza -> IO ()
    , xmppInformPeerPresence :: ConnectionKey -> Stanza -> IO ()
    , xmppAnswerProbe :: ConnectionKey -> Stanza -> TChan Stanza -> IO ()
    , xmppClientSubscriptionRequest :: IO () -> ConnectionKey -> Stanza -> TChan Stanza -> IO () 
    , xmppPeerSubscriptionRequest :: IO () -> ConnectionKey -> Stanza -> TChan Stanza -> IO () 
    , xmppClientInformSubscription :: IO () -> ConnectionKey -> Stanza -> IO ()
    , xmppPeerInformSubscription :: IO () -> ConnectionKey -> Stanza -> IO ()
    }


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

peerKeyToText :: ConnectionKey -> Text
peerKeyToText (PeerKey { callBackAddress=addr }) = addrToText addr
peerKeyToText (ClientKey { localAddress=addr }) = "ErrorClIeNt0"


wlog :: String -> IO ()
wlog s = putStrLn s >> hFlush stdout

wlogb :: ByteString -> IO ()
wlogb s = Strict8.putStrLn s >> hFlush stdout

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

xmlStream :: ReadCommand -> WriteCommand -> ( Source IO XML.Event
                                            , Sink (Flush XML.Event) IO () )
xmlStream conread conwrite = (xsrc,xsnk)
 where
    xsrc = src $= XML.parseBytes XML.def
    xsnk :: Sink (Flush Event) IO ()
    xsnk = -- XML.renderBytes XML.def =$ 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
  :: Conduit () IO Event
     -> IO (LockedChan Event, TVar (Maybe [Event]), TMVar a)
conduitToChan c = do
    chan <- atomically newLockedChan
    clsrs <- atomically $ newTVar (Just [])
    quitvar <- atomically $ newEmptyTMVar
    forkIO $ do
        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
     -> Conduit () IO Event
     -> 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


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
    flip (maybe $ return ())
         (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 
    flip (maybe $ return Nothing)  mtag $ \tag -> do
    case tagName tag of
        "{urn:xmpp:ping}ping" -> return $ Just Ping
        "{jabber:iq:roster}query" -> return $ Just RequestRoster
        name -> return . Just $ 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
        flip (maybe $ 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 
    flip (maybe $ 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 
    flip (maybe $ return Nothing)  mtag $ \tag -> do
    case tagName tag of
        "{urn:ietf:params:xml:ns:xmpp-bind}bind" -> do
            mchild <- nextElement
            case fmap tagName mchild of
                Just "{urn:ietf:params:xml:ns:xmpp-bind}resource" -> do
                    rsc <- XML.content -- TODO: MonadThrow???
                    return . Just $ RequestResource (Just rsc)
                Just _ -> return Nothing
                Nothing -> return . Just $ RequestResource Nothing
        "{urn:ietf:params:xml:ns:xmpp-session}session" -> do
            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
        flip (maybe $ return ()) 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
    x <- nextElement
    flip (maybe $ return Nothing) x $ \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
    flip (maybe $ return Nothing) x $ \x -> do
    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")
       ]


xmppInbound :: Server ConnectionKey SockAddr
                -> XMPPServerParameters
                -> ConnectionKey
                -> SockAddr
                -> FlagCommand -- ^ action to check whether the connection needs a ping
                -> TChan Stanza -- ^ channel to announce incomming stanzas on
                -> TChan Stanza -- ^ channel used to send stanzas
                -> TMVar () -- ^ mvar that is filled when the connection quits
                -> Sink XML.Event IO ()
xmppInbound sv xmpp k laddr pingflag stanzas output donevar = doNestingXML $ do
    let (namespace,tellmyname,tellyourname) = case k of
            ClientKey {} -> ( "jabber:client"
                            , xmppTellMyNameToClient xmpp
                            , xmppTellClientHisName xmpp k
                            )
            PeerKey {} -> ( "jabber:server"
                          , xmppTellMyNameToPeer xmpp laddr
                          , xmppTellPeerHisName xmpp k
                          )
    me <- liftIO tellmyname
    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,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 = NetworkOrigin k output
                              }
                ioWriteChan stanzas s
          you <- liftIO tellyourname
          flip (maybe $ 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
#ifdef PINGNOISE
                -- 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 = NetworkOrigin k output
                            }
#endif
              stype -> ioWriteChan stanzas Stanza
                            { stanzaType = stype
                            , stanzaId = mid
                            , stanzaTo = mto
                            , stanzaFrom = mfrom
                            , stanzaChan = chan
                            , stanzaClosers = clsrs
                            , stanzaInterrupt = donevar
                            , stanzaOrigin = NetworkOrigin k 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
    flip (maybe $ return ()) 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"
    ]


presenceSolicitation :: Text -> Text -> 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" ]

forkConnection :: Server ConnectionKey SockAddr
                -> XMPPServerParameters
                -> ConnectionKey
                -> SockAddr
                -> FlagCommand
                -> Source IO XML.Event
                -> Sink (Flush XML.Event) IO ()
                -> TChan Stanza
                ->  IO (TChan Stanza)
forkConnection sv xmpp k laddr pingflag src snk stanzas = do
    let (namespace,tellmyname) = case k of
                        ClientKey {} -> ("jabber:client", xmppTellMyNameToClient xmpp)
                        PeerKey {} -> ("jabber:server",xmppTellMyNameToPeer xmpp laddr)
    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 = do
            what <- 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 ())
                ]
            what
    forkIO $ do (greet_src >> slot_src) $$ snk
                last <- atomically $ readTVar lastStanza
                es <- while (atomically . fmap not $ Slotted.isEmpty slots)
                            (atomically . Slotted.pull $ slots)
                let es' = mapMaybe metadata es
                    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 post-queue fork: " ++ show k
    output <- atomically newTChan
    hacks <- atomically $ newTVar Map.empty
    msgids <- atomically $ newTVar []
    forkIO $ do
        -- mapM_ (atomically . Slotted.push slots Nothing) greetPeer
        fix $ \loop -> do
            what <- atomically $ foldr1 orElse
                [readTChan output >>= \stanza -> return $ do
#ifndef PINGNOISE
                    let notping f = case stanzaType stanza of Pong -> return ()
                                                              _ -> f
#else
                    let notping f = f
#endif
                    -- 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 k of
                                    ClientKey {} -> "C"
                                    PeerKey {}   -> "P"
                        wlog ""
                        stanzaToConduit dup $$ prettyPrint typ
                    -- 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 ()
                    stanzaToConduit stanza =$= wrapStanzaConduit stanza
                        $$ awaitForever
                            -- TODO: PresenceStatus stanzas should be pushed to appropriate slots
                            $ liftIO . atomically . Slotted.push slots Nothing
                    case stanzaType stanza of
                        Error err tag | tagName tag=="{jabber:client}message" -> do
                            wlog $ "handling Error hacks"
                            b <- atomically $ do m <- readTVar hacks
                                                 cached <- readTVar msgids
                                                 flip (maybe $ return False) (stanzaId stanza) $ \id' -> do
                                                 return $ Map.member SimulatedChatErrors m
                                                            && elem id' cached
                            ids <- atomically $ readTVar msgids
                            wlog $ "ids = " ++ show (b,stanzaId stanza, ids)
                            when b $ do
                            let sim = simulateChatError err (stanzaFrom stanza)
                            wlog $ "sending simulated chat for error message."
                            CL.sourceList sim =$= wrapStanzaConduit stanza -- not quite right, but whatever
                                $$ 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 <- xmppTellPeerHisName xmpp k -- addrToText (callBackAddress k)
                    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
#ifdef PINGNOISE
                    wlog ""
                    CL.sourceList ping0 $$ prettyPrint $ case k of
                        ClientKey {} -> "C<-Ping"
                        PeerKey {} -> "P<-Ping "
#endif
                    loop
                ,readTMVar rdone >> return (return ())
                ]
            what
        wlog $ "end pre-queue fork: " ++ show k
    forkIO $ do
        -- src $$ awaitForever (lift . putStrLn . takeWhile (/=' ') . show)
        src $$ xmppInbound sv xmpp k laddr pingflag stanzas output rdone
        atomically $ putTMVar rdone ()
        wlog $ "end reader fork: " ++ show k
    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 :: (Socket,SockAddr) -> IO (ConnectionKey,SockAddr)
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
    laddr <- getSocketName sock
    return $ (PeerKey (peer `withPort` fromIntegral peerport),laddr)

clientKey :: (Socket,SockAddr) -> IO (ConnectionKey,SockAddr)
clientKey (sock,addr) = do
    paddr <- getPeerName sock
    return $ (ClientKey addr,paddr)

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
    -> TChan Stanza
    -> IO ()
sendRoster query xmpp replyto = do
    let k = case stanzaOrigin query of
             NetworkOrigin k _ -> Just k
             LocalPeer -> Nothing -- local peer requested roster?
    flip (maybe $ return ()) k $ \k -> do
    hostname <- xmppTellMyNameToClient xmpp
    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 <- case k of
                ClientKey {} -> xmppTellClientHisName xmpp k -- LookupClientJID xmpp k
                PeerKey {}   -> xmppTellClientNameOfPeer xmpp k (Set.toList buddies)
    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 ConnectionKey SockAddr -> ConnectionKey -> IO SockAddr
socketFromKey sv k = do
    map <- atomically $ readTVar (conmap sv)
    let mcd = Map.lookup k map
    case mcd of
        Nothing -> case k of
                    ClientKey addr -> return addr
                    PeerKey addr -> return addr 
                        -- XXX: ? wrong address
                        -- Shouldnt happen anyway.
        Just cd -> return $ 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 ConnectionKey SockAddr
    -> ConnectionParameters ConnectionKey SockAddr
    -> XMPPServerParameters
    -> IO b
monitor sv params xmpp = do
    chan <- return $ serverEvent sv
    stanzas <- atomically newTChan
    quitVar <- atomically newEmptyTMVar
    fix $ \loop -> do
    action <- atomically $ foldr1 orElse
      [ readTChan chan >>= \((k,u),e) -> return $ do 
        case e of
            Connection pingflag conread conwrite -> do
                 wlog $ tomsg k "Connection"
                 let (xsrc,xsnk) = xmlStream conread conwrite
                 outs <- forkConnection sv xmpp k u pingflag xsrc xsnk stanzas
                 xmppNewConnection xmpp k u outs
                 return ()
            ConnectFailure addr -> return () -- wlog $ tomsg k "ConnectFailure"
            EOF        -> do wlog $ tomsg k "EOF"
                             xmppEOF xmpp k
            HalfConnection In -> do
                wlog $ tomsg k "ReadOnly"
                control sv (Connect (callBackAddress k) params)
            HalfConnection Out -> wlog $ tomsg k "WriteOnly"
            RequiresPing -> return () -- wlog $ tomsg k "RequiresPing"
            _ -> return ()
      , 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
                NetworkOrigin k@(ClientKey {}) replyto -> 
                    case stanzaType stanza of
                        RequestResource wanted -> do
                            sockaddr <- socketFromKey sv k
                            rsc <- xmppChooseResourceName xmpp k sockaddr wanted
                            let reply = iq_bind_reply (stanzaId stanza) rsc
                            -- sendReply quitVar SetResource reply replyto
                            hostname <- xmppTellMyNameToClient xmpp
                            let requestVersion :: Producer IO XML.Event
                                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
                            let reply = iq_session_reply (stanzaId stanza) me
                            sendReply quitVar Pong reply replyto
                        RequestRoster -> do
                            sendRoster stanza xmpp 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
                            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 ()
                NetworkOrigin k@(PeerKey {}) 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 ()
                    NetworkOrigin _ replyto -> deliver replyto
                Error {} -> do
                  case stanzaOrigin stanza of
                    LocalPeer {} -> return ()
                    NetworkOrigin k replyto -> do
                         -- wlog $ "delivering error: " ++show (stanzaId stanza)
                         -- wlog $ " from: " ++ show k
                         deliver replyto
                _ -> return ()
        -- We need to clone in the case the stanza is passed on as for Message.
#ifndef PINGNOISE
        let notping f = case stanzaType stanza of Pong -> return ()
                                                  _ -> f
        notping $ do
#endif
        let typ = Strict8.pack $ c ++ "->"++(concat . take 1 . words $ show (stanzaType stanza))++" "
            c = case stanzaOrigin stanza of
                    LocalPeer -> "*"
                    NetworkOrigin (ClientKey {}) _ -> "C"
                    NetworkOrigin (PeerKey {})   _ -> "P"
        wlog ""
        stanzaToConduit dup $$ prettyPrint typ
        
      ]
    action
    loop
 where
    tomsg k str =  printf "%12s %s" str (show k)
        where
            _ = str :: String

data XMPPServer
    = XMPPServer { _xmpp_sv :: Server ConnectionKey SockAddr
                 , _xmpp_peer_params :: ConnectionParameters ConnectionKey SockAddr
                 }

addPeer :: XMPPServer -> SockAddr -> IO ()
addPeer sv addr = do
    control (_xmpp_sv sv) (ConnectWithEndlessRetry addr (_xmpp_peer_params sv) 10000)

xmppServer :: ( MonadResource m
              , MonadIO m
              ) => XMPPServerParameters -> m XMPPServer
xmppServer xmpp = do
    sv <- server
    -- some fuzz helps avoid simultaneity
    pingfuzz <- liftIO $ do
        gen <- System.Random.getStdGen
        let (r,gen') = System.Random.next gen
        return $ r `mod` 2000 -- maximum 2 seconds of fuzz
    liftIO . wlog $ "pingfuzz = " ++ show pingfuzz
    let peer_params = (connectionDefaults peerKey)
                          { pingInterval = 15000 + pingfuzz
                          , timeout = 2000
                          , duplex = False }
        client_params = (connectionDefaults clientKey)
                          { pingInterval = 0
                          , timeout = 0
                          }
    liftIO $ do
        forkIO $ monitor sv peer_params xmpp
        control sv (Listen peerport peer_params)
        control sv (Listen clientport client_params)
    return XMPPServer { _xmpp_sv = sv, _xmpp_peer_params = peer_params }

#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