path: root/xmppServer.hs

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TupleSections #-}
import System.Posix.Signals
import Control.Concurrent (threadDelay,forkIO,forkOS,killThread,throwTo)
import Control.Concurrent.STM
import Control.Concurrent.STM.TMVar
import Control.Monad.Trans.Resource (runResourceT)
import Control.Monad.Trans
import Control.Monad.IO.Class (MonadIO, liftIO)
import Network.Socket ( SockAddr(..) )
import System.Endian (fromBE32)
import Data.List (nub, (\\), intersect, groupBy, sort, sortBy )
import Data.Ord (comparing )
import Data.Monoid ( (<>) )
import qualified Data.Text as Text
import qualified Data.Text.IO as Text
import qualified Data.Text.Encoding as Text
import Control.Monad
import qualified Network.BSD as BSD
import qualified Data.Text as Text
import Data.Text (Text)
import qualified Data.Map as Map
import Data.Map (Map)
import Control.Exception ({-evaluate,-}handle,SomeException(..),bracketOnError,ErrorCall(..))
import System.IO.Error (isDoesNotExistError)
import System.Posix.User (getUserEntryForID,userName)
import qualified Data.ByteString.Lazy.Char8 as L
import qualified ConfigFiles
import Data.Maybe (maybeToList,listToMaybe,mapMaybe)
import Data.Bits
import Data.Int (Int8)

import TraversableT
import UTmp (ProcessID,users)
import LocalPeerCred
import XMPPServer
import PeerResolve

type UserName = Text
type ResourceName = Text

unsplitJID :: (Maybe UserName,Text,Maybe ResourceName) -> Text
unsplitJID (n,h,r) = username <> h <> resource
 where
    username = maybe "" (<>"@") n
    resource = maybe "" ("/"<>) r

splitJID :: Text -> (Maybe UserName,Text,Maybe ResourceName)
splitJID bjid = 
    let xs = splitAll '@' bjid
        ys = splitAll '/' (last xs)
        splitAll c bjid = take 1 xs0 ++ map (Text.drop 1) (drop 1 xs0)
            where xs0 = Text.groupBy (\x y-> y/=c) bjid
        server = head ys
        name = case xs of
                (n:s:_) -> Just n
                (s:_)   -> Nothing
        rsrc = case ys of
                (s:_:_) -> Just $ last ys
                _       -> Nothing
    in (name,server,rsrc)

isPeerKey :: ConnectionKey -> Bool
isPeerKey k = case k of { PeerKey {} -> True ; _ -> False }

isClientKey :: ConnectionKey -> Bool
isClientKey k = case k of { ClientKey {} -> True ; _ -> False }

textHostName = fmap Text.pack BSD.getHostName

localJID user resource = do
    hostname <- textHostName
    return $ user <> "@" <> hostname <> "/" <> resource

cf_available :: Int8
cf_available = 0x1
cf_interested :: Int8
cf_interested = 0x2

data ClientState = ClientState
    { clientResource :: Text
    , clientUser :: Text
    , clientPid :: Maybe ProcessID
    , clientStatus :: TVar (Maybe Stanza)
    , clientFlags :: TVar Int8
    }

-- | True if the client has sent an initial presence
clientIsAvailable c  = do
    flgs <- readTVar (clientFlags c)
    return $ flgs .&. cf_available /= 0

-- | True if the client has requested a roster
clientIsInterested c = do
    flgs <- readTVar (clientFlags c)
    return $ flgs .&. cf_interested /= 0

data LocalPresence = LocalPresence
    { networkClients :: Map ConnectionKey ClientState
    -- TODO: loginClients
    }

data RemotePresence = RemotePresence
    { resources :: Map Text Stanza
    -- , localSubscribers :: Map Text ()
    -- ^ subset of clientsByUser who should be
    -- notified about this presence.
    }



pcSingletonNetworkClient key client =
    LocalPresence
    { networkClients = Map.singleton key client
    } 

pcInsertNetworkClient key client pc =
    pc { networkClients = Map.insert key client (networkClients pc) }

pcRemoveNewtworkClient key pc = if pcIsEmpty pc' then Nothing
                                                 else Just pc'
 where
    pc' = pc { networkClients = Map.delete key (networkClients pc) }

pcIsEmpty pc = Map.null (networkClients pc)


data PresenceState = PresenceState
    { clients :: TVar (Map ConnectionKey ClientState)
    , clientsByUser :: TVar (Map Text LocalPresence)
    , remotesByPeer :: TVar (Map ConnectionKey
                                 (Map UserName
                                      RemotePresence))
    , associatedPeers :: TVar (Map SockAddr ())
    , server :: TMVar XMPPServer
    , keyToChan :: TVar (Map ConnectionKey Conn)
    }



getConsolePids :: PresenceState -> IO [(Text,ProcessID)]
getConsolePids state = do
    us <- UTmp.users
    return $ map (\(_,tty,pid)->(lazyByteStringToText tty,pid)) us

lazyByteStringToText = (foldr1 (<>) . map Text.decodeUtf8 . L.toChunks)
textToLazyByteString s = L.fromChunks [Text.encodeUtf8 s]

identifyTTY' ttypids uid inode = ttypid
 where ttypids' = map (\(tty,pid)->(L.fromChunks [Text.encodeUtf8 tty], pid)) ttypids
       ttypid = fmap textify $ identifyTTY ttypids' uid inode
       textify (tty,pid) = (fmap lazyByteStringToText tty, pid)

chooseResourceName state k addr desired = do
    muid <- getLocalPeerCred' addr
    (mtty,pid) <- getTTYandPID muid
    user <- getJabberUserForId muid
    status <- atomically $ newTVar Nothing
    flgs <- atomically $ newTVar 0
    let client = ClientState { clientResource = maybe "fallback" id mtty
                             , clientUser = user
                             , clientPid = pid
                             , clientStatus = status
                             , clientFlags = flgs }

    do -- forward-lookup of the buddies so that it is cached for reversing.
       buds <- configText ConfigFiles.getBuddies (clientUser client)
       forM_ buds $ \bud -> do
            let (_,h,_) = splitJID bud
            forkIO $ void $ resolvePeer h

    atomically $ do
        modifyTVar' (clients state) $ Map.insert k client
        modifyTVar' (clientsByUser state) $ flip Map.alter (clientUser client)
            $ \mb -> Just $ maybe (pcSingletonNetworkClient k client)
                                  (pcInsertNetworkClient k client)
                                  mb

    localJID (clientUser client) (clientResource client)
    
  where
    getTTYandPID muid = do
        -- us <- fmap (map (second fst) . Map.toList) . readTVarIO $ activeUsers state
        ttypids <- getConsolePids state
        -- let tailOf3 ((_,a),b) = (a,b)
        (t,pid) <- case muid of
                      Just (uid,inode) -> identifyTTY' ttypids uid inode
                      Nothing          -> return (Nothing,Nothing)
        let rsc = t `mplus` fmap ( ("pid."<>) . Text.pack . show ) pid
        return (rsc,pid)

    getJabberUserForId muid =
             maybe (return "nobody") 
                   (\(uid,_) -> 
                        handle (\(SomeException _) -> 
                                return . (<> "uid.") . Text.pack . show $ uid)
                          $ do
                             user <- fmap userName $ getUserEntryForID uid
                             return (Text.pack user)
                        )
                   muid

forClient state k fallback f = do
    mclient <- atomically $ do
        cs <- readTVar (clients state)
        return $ Map.lookup k cs
    maybe fallback f mclient

tellClientHisName state k = forClient state k fallback go
 where
    fallback  = localJID "nobody" "fallback"
    go client = localJID (clientUser client) (clientResource client)

toMapUnit xs = Map.fromList $ map (,()) xs

resolveAllPeers :: [Text] -> IO (Map SockAddr ())
resolveAllPeers hosts = fmap (toMapUnit . concat) $ Prelude.mapM (fmap (take 1) . resolvePeer) hosts


rosterGetStuff
  :: (L.ByteString -> IO [L.ByteString])
     -> PresenceState -> ConnectionKey -> IO [Text]
rosterGetStuff what state k = forClient state k (return [])
    $ \client -> do
    jids <- configText what (clientUser client)
    let hosts = map ((\(_,h,_)->h) . splitJID) jids
    addrs <- resolveAllPeers hosts 
    peers <- atomically $ readTVar (associatedPeers state)
    addrs <- return $ addrs `Map.difference` peers
    sv <- atomically $ takeTMVar $ server state
    -- Grok peers to associate with from the roster:
    forM_ (Map.keys addrs) $ \addr -> do
        putStrLn $ "new addr: "++show addr
        addPeer sv addr
    -- Update local set of associated peers
    atomically $ do
        writeTVar (associatedPeers state) (addrs `Map.union` peers)
        putTMVar (server state) sv
    return jids

rosterGetBuddies :: PresenceState -> ConnectionKey -> IO [Text]
rosterGetBuddies state k = rosterGetStuff ConfigFiles.getBuddies state k

rosterGetSolicited :: PresenceState -> ConnectionKey -> IO [Text]
rosterGetSolicited = rosterGetStuff ConfigFiles.getSolicited

rosterGetOthers :: PresenceState -> ConnectionKey -> IO [Text]
rosterGetOthers = rosterGetStuff ConfigFiles.getOthers

rosterGetSubscribers :: PresenceState -> ConnectionKey -> IO [Text]
rosterGetSubscribers = rosterGetStuff ConfigFiles.getSubscribers

data Conn = Conn { connChan :: TChan Stanza
                 , auxAddr :: SockAddr }

configText what u = fmap (map lazyByteStringToText)
                        $ what (textToLazyByteString u)

getBuddies' :: Text -> IO [Text]
getBuddies' = configText ConfigFiles.getBuddies
getSolicited' :: Text -> IO [Text]
getSolicited' = configText ConfigFiles.getSolicited

sendProbesAndSolicitations state k laddr chan = do
    -- get all buddies & solicited matching k for all users
    xs <- runTraversableT $ do
        cbu <- lift $ atomically $ readTVar $ clientsByUser state
        user <- liftT $ Map.keys cbu
        (isbud,getter) <- liftT [(True ,getBuddies'  )
                                ,(False,getSolicited')]
        bud  <- liftMT $ getter user
        let (u,h,r) = splitJID bud
        addr <- liftMT $ nub `fmap` resolvePeer h
        liftT $ guard (PeerKey addr == k)
        -- Note: Earlier I was tempted to do all the IO
        -- within the TraversableT monad.  That apparently
        -- is a bad idea.  Perhaps due to laziness and an
        -- unforced list?  Instead, we will return a list
        -- of (Bool,Text) for processing outside.
        return (isbud,u,if isbud then "" else user)
    -- XXX: The following O(n²) nub may be a little
    --      too onerous.
    forM_ (nub xs) $ \(isbud,u,user) -> do
        let make = if isbud then presenceProbe 
                            else presenceSolicitation
            toh = peerKeyToText k
            jid = unsplitJID (u,toh,Nothing)
            me = addrToText laddr
            from = if isbud then me -- probe from server
                            else -- solicitation from particular user
                                 unsplitJID (Just user,me,Nothing)
        stanza <- make from jid
        -- send probes for buddies, solicitations for solicited.
        putStrLn $ "probing "++show k++" for: " ++ show (isbud,jid)
        atomically $ writeTChan chan stanza
    -- reverse xs `seq` return ()

newConn state k addr outchan = do
    atomically $ modifyTVar' (keyToChan state)
        $ Map.insert k Conn { connChan = outchan
                            , auxAddr  = addr }
    when (isPeerKey k)
        $ sendProbesAndSolicitations state k addr outchan

delclient k mlp = do
    lp <- mlp
    let nc = Map.delete k $ networkClients lp
    guard $ not (Map.null nc)
    return $ lp { networkClients = nc }

eofConn state k = do
    atomically $ modifyTVar' (keyToChan state) $ Map.delete k
    case k of
        ClientKey {} -> do
            forClient state k (return ()) $ \client -> do
            stanza <- makePresenceStanza "jabber:server" Nothing Offline
            informClientPresence state k stanza
            atomically $ do
                modifyTVar' (clientsByUser state)
                    $ Map.alter (delclient k) (clientUser client)
        PeerKey {} -> do
            let h = peerKeyToText k
            jids <- atomically $ do
                rbp <- readTVar (remotesByPeer state)
                return $ do
                    umap <- maybeToList $ Map.lookup k rbp
                    (u,rp) <- Map.toList umap
                    r <- Map.keys (resources rp)
                    return $ unsplitJID (Just u, h, Just r)
            forM_ jids $ \jid -> do
            stanza <- makePresenceStanza "jabber:client" (Just jid) Offline
            informPeerPresence state k stanza

{-
rewriteJIDForClient1:: Text -> IO (Maybe ((Maybe Text,Text,Maybe Text),SockAddr))
rewriteJIDForClient1 jid = do
    let (n,h,r) = splitJID jid
    maddr <- fmap listToMaybe $ resolvePeer h
    flip (maybe $ return Nothing) maddr $ \addr -> do
        h' <- peerKeyToResolvedName (PeerKey addr)
        return $ Just ((n,h',r), addr)
-}

todo = error "Unimplemented"


-- | for example:  2001-db8-85a3-8d3-1319-8a2e-370-7348.ipv6-literal.net
ip6literal :: Text -> Text
ip6literal addr = Text.map dash addr <> ".ipv6-literal.net"
 where
    dash ':' = '-'
    dash x   = x

-- | The given address is taken to be the local address for the socket this JID
-- came in on.  The returned JID parts are suitable for unsplitJID to create a
-- valid JID for communicating to a client.  The returned Bool is True when the
-- host part refers to this local host (i.e. it equals the given SockAddr).
-- If there are multiple results, it will prefer one which is a member of the
-- given list in the last argument.
rewriteJIDForClient :: SockAddr -> Text -> [Text] -> IO (Bool,(Maybe Text,Text,Maybe Text))
rewriteJIDForClient laddr jid buds = do
    let (n,h,r) = splitJID jid
    maddr <- parseAddress (strip_brackets h)
    flip (maybe $ return (False,(n,ip6literal h,r))) maddr $ \addr -> do
    let mine =  laddr `withPort` 0  == addr `withPort` 0
    h' <- if mine then textHostName
                  else peerKeyToResolvedName buds (PeerKey addr)
    return (mine,(n,h',r))

sameAddress laddr addr = laddr `withPort` 0  == addr `withPort` 0

peerKeyToResolvedName :: [Text] -> ConnectionKey -> IO Text
peerKeyToResolvedName buds k@(ClientKey { localAddress=addr }) = return "ErrorClIeNt1"
peerKeyToResolvedName buds pk = do
    ns <- peerKeyToResolvedNames pk
    let hs = map (\jid -> let (_,h,_)=splitJID jid in h) buds
        ns' = sortBy (comparing $ not . flip elem hs) ns
    return $ maybe (peerKeyToText pk) id (listToMaybe ns')


multiplyJIDForClient :: SockAddr -> Text -> IO (Bool,[(Maybe Text,Text,Maybe Text)])
multiplyJIDForClient laddr jid = do
    let (n,h,r) = splitJID jid
    maddr <- parseAddress (strip_brackets h)
    flip (maybe $ return (False,[(n,ip6literal h,r)])) maddr $ \addr -> do
    let mine =  sameAddress laddr addr
    names <- if mine then fmap (:[]) textHostName
                     else peerKeyToResolvedNames (PeerKey addr)
    return (mine,map (\h' -> (n,h',r)) names)


addrTextToKey h = do
    maddr <- parseAddress (strip_brackets h)
    return (fmap PeerKey maddr)

guardPortStrippedAddress h laddr = do
    maddr <- fmap (fmap (`withPort` 0)) $ parseAddress (strip_brackets h)
    let laddr' = laddr `withPort` 0
    return $ maddr >>= guard . (==laddr')


-- | Accepts a textual representation of a domainname
-- JID suitable for client connections, and returns the
-- coresponding ipv6 address JID suitable for peers paired
-- with a SockAddr with the address part of that JID in
-- binary form.  If no suitable address could be resolved
-- for the given name, Nothing is returned.
rewriteJIDForPeer :: Text -> IO (Maybe (Text,SockAddr))
rewriteJIDForPeer jid = do
    let (n,h,r) = splitJID jid
    maddr <- fmap listToMaybe $ resolvePeer h
    return $ flip fmap maddr $ \addr ->
        let h' = addrToText addr
            to' = unsplitJID (n,h',r)
        in (to',addr)

-- | deliver <message/> or error stanza
deliverMessage state fail msg = 
    case stanzaOrigin msg of
      NetworkOrigin senderk@(ClientKey {}) _ -> do
        -- Case 1.  Client -> Peer
        mto <- do
            flip (maybe $ return Nothing) (stanzaTo msg) $ \to -> do
            rewriteJIDForPeer to
        flip (maybe fail {- reverse lookup failure -})
             mto
            $ \(to',addr) -> do
        let k = PeerKey addr
        chans <- atomically $ readTVar (keyToChan state)
        flip (maybe fail) (Map.lookup k chans) $ \(Conn { connChan=chan
                                                        , auxAddr=laddr }) -> do
        (n,r) <- forClient state senderk (return (Nothing,Nothing))
                        $ \c -> return (Just (clientUser c), Just (clientResource c))
        -- original 'from' address is discarded.
        let from' = unsplitJID (n,addrToText laddr,r)
        -- dup <- atomically $ cloneStanza (msg { stanzaTo=Just to', stanzaFrom=Just from' })
        let dup = (msg { stanzaTo=Just to', stanzaFrom=Just from' })
        sendModifiedStanzaToPeer dup chan
      NetworkOrigin senderk@(PeerKey {}) _ -> do
        key_to_chan <- atomically $ readTVar (keyToChan state)
        flip (maybe fail) (Map.lookup senderk key_to_chan)
            $ \(Conn { connChan=sender_chan
                     , auxAddr=laddr }) -> do
        flip (maybe fail) (stanzaTo msg) $ \to -> do
        (mine,(n,h,r)) <- rewriteJIDForClient laddr to []
        if not mine then fail else do
        let to' = unsplitJID (n,h,r)
        cmap <- atomically . readTVar $ clientsByUser state
        flip (maybe fail) n $ \n -> do
        flip (maybe fail) (Map.lookup n cmap) $ \presence_container -> do
        buds <- configText ConfigFiles.getBuddies n
        from' <- do
            flip (maybe $ return Nothing) (stanzaFrom msg) $ \from -> do
            (_,trip) <- rewriteJIDForClient laddr from buds
            return . Just $ unsplitJID trip
        let ks = Map.keys (networkClients presence_container)
            chans = mapMaybe (flip Map.lookup key_to_chan) ks
        if null chans then fail else do
        forM_ chans $ \Conn { connChan=chan} -> do
        putStrLn $ "sending "++show (stanzaId msg)++" to clients "++show ks
        -- TODO: Cloning isn't really neccessary unless there are multiple
        -- destinations and we should probably transition to minimal cloning,
        -- or else we should distinguish between announcable stanzas and
        -- consumable stanzas and announcables use write-only broadcast
        -- channels that must be cloned in order to be consumed.
        -- For now, we are doing redundant cloning.
        dup <- cloneStanza (msg { stanzaTo=Just to'
                                , stanzaFrom=from' })
        sendModifiedStanzaToClient dup
                                  chan


setClientFlag state k flag = 
        atomically $ do
            cmap <- readTVar (clients state)
            flip (maybe $ return ()) (Map.lookup k cmap) $ \client -> do
            modifyTVar' (clientFlags client) (\flgs -> flgs .|. flag)

informSentRoster state k = do
    setClientFlag state k cf_interested


subscribedPeers user = do
    jids <- configText ConfigFiles.getSubscribers user
    let hosts = map ((\(_,h,_)->h) . splitJID) jids
    fmap Map.keys $ resolveAllPeers hosts 

-- | this JID is suitable for peers, not clients.
clientJID con client = unsplitJID ( Just $ clientUser client
                                  , addrToText $ auxAddr con
                                  , Just $ clientResource client)

-- | Send presence notification to subscribed peers.
-- Note that a full JID from address will be added to the
-- stanza if it is not present.
informClientPresence state k stanza = do
    dup <- cloneStanza stanza
    atomically $ do
        mb <- fmap (Map.lookup k) $ readTVar (clients state)
        flip (maybe $ return ()) mb $ \cstate -> do
        writeTVar (clientStatus cstate) $ Just dup
    forClient state k (return ()) $ \client -> do
    is_avail <- atomically $ clientIsAvailable client
    when (not is_avail) $ do
        setClientFlag state k cf_available
        sendCachedPresence state k
    addrs <- subscribedPeers (clientUser client)
    ktc <- atomically $ readTVar (keyToChan state)
    let connected = mapMaybe (flip Map.lookup ktc . PeerKey) addrs
    forM_ connected $ \con -> do
    let from' = clientJID con client
    mto <- runTraversableT $ do
            to <- liftT $ stanzaTo stanza
            (to',_) <- liftMT $ rewriteJIDForPeer to
            return to'
    dup <- cloneStanza stanza
    sendModifiedStanzaToPeer dup { stanzaFrom = Just from'
                                 , stanzaTo = mto }
                             (connChan con)

informPeerPresence state k stanza = do
    -- Presence must indicate full JID with resource...
    putStrLn $ "xmppInformPeerPresence checking from address..." 
    flip (maybe $ return ()) (stanzaFrom stanza) $ \from -> do
    let (muser,h,mresource) = splitJID from
    putStrLn $ "xmppInformPeerPresence from  = " ++ show from
    -- flip (maybe $ return ()) mresource       $ \resource -> do
    flip (maybe $ return ()) muser           $ \user -> do
    
    clients <- atomically $ do

        -- Update remotesByPeer...
        rbp <- readTVar (remotesByPeer state)
        let umap = maybe Map.empty id $ Map.lookup k rbp
            rp = case (presenceShow $ stanzaType stanza) of
                    Offline ->
                        maybe Map.empty
                              (\resource -> 
                                  maybe (Map.empty)
                                     (Map.delete resource . resources)
                                   $ Map.lookup user umap)
                              mresource
                    
                    _ ->maybe Map.empty
                              (\resource ->
                                  maybe (Map.singleton resource stanza) 
                                     (Map.insert resource stanza . resources )
                                    $ Map.lookup user umap)
                              mresource
            umap' = Map.insert user (RemotePresence rp) umap
        
        flip (maybe $ return []) (case presenceShow $ stanzaType stanza of
                                     Offline -> Just ()
                                     _ -> mresource >> Just ())
            $ \_ -> do
        writeTVar (remotesByPeer state) $ Map.insert k umap' rbp
        -- TODO: Store or delete the stanza (remotesByPeer)
        
        -- all clients, we'll filter available/authorized later

        ktc <- readTVar (keyToChan state)
        runTraversableT $ do
        (ck,client) <- liftMT $ fmap Map.toList $ readTVar (clients state)
        con <- liftMaybe $ Map.lookup ck ktc 
        return (ck,con,client)
    putStrLn $ "xmppInformPeerPresence (length clients="++show (length clients)++")"
    forM_ clients $ \(ck,con,client) -> do
        -- (TODO: appropriately authorized clients only.)
        -- For now, all "available" clients (available = sent initial presence)
        is_avail <- atomically $ clientIsAvailable client
        when is_avail $ do
        putStrLn $ "reversing for client: " ++ show from
        froms <- do
            let ClientKey laddr = ck
            (_,trip) <- multiplyJIDForClient laddr from
            return (map unsplitJID trip)
                    
        putStrLn $ "sending to client: " ++ show (stanzaType stanza,froms)
        forM_ froms $ \from' -> do
        dup <- cloneStanza stanza
        sendModifiedStanzaToClient (dup { stanzaFrom=Just from' })
                                   (connChan con)

answerProbe state mto k chan = do
    -- putStrLn $ "answerProbe! " ++ show (stanzaType stanza)
    ktc <- atomically $ readTVar (keyToChan state)
    muser <- runTraversableT $ do
        to <- liftT $ mto
        conn <- liftT $ Map.lookup k ktc
        let (mu,h,_) = splitJID to -- TODO: currently resource-id is ignored on presence
                                   --  probes.  Is this correct? Check the spec.
        liftMT $ guardPortStrippedAddress h (auxAddr conn)
        u <- liftT mu
        let ch = addrToText (auxAddr conn)
        return (u,conn,ch)

    flip (maybe $ return ()) muser $ \(u,conn,ch) -> do

    resolved_subs <- resolvedFromRoster ConfigFiles.getSubscribers u
    let gaddrs = groupBy (\a b -> snd a == snd b) (sort resolved_subs)
        whitelist = do
            xs <- gaddrs
            x <- take 1 xs
            guard $ snd x==k
            mapMaybe fst xs

    -- -- only subscribed peers should get probe replies
    -- addrs <- subscribedPeers u

    -- TODO: notify remote peer that they are unsubscribed?
    --   reply <- makeInformSubscription "jabber:server" to from False
    when (not $ null whitelist) $ do

    replies <- runTraversableT $ do
        cbu <- lift . atomically $ readTVar (clientsByUser state)
        lpres <- liftMaybe $ Map.lookup u cbu
        clientState <- liftT $ Map.elems (networkClients lpres)
        stanza <- liftIOMaybe $ atomically (readTVar (clientStatus clientState))
        stanza <- lift $ cloneStanza stanza
        let jid = unsplitJID (Just $ clientUser clientState
                             , ch
                             ,Just $ clientResource clientState)
        return stanza { stanzaFrom = Just jid
                      , stanzaType = (stanzaType stanza)
                        { presenceWhiteList = whitelist }
                      }

    forM_ replies $ \reply -> do
        sendModifiedStanzaToPeer reply chan

    -- if no presence, send offline message
    when (null replies) $ do
        let jid = unsplitJID (Just u,ch,Nothing)
        pstanza <- makePresenceStanza "jabber:server" (Just jid) Offline
        atomically $ writeTChan (connChan conn) pstanza

sendCachedPresence state k = do
    forClient state k (return ()) $ \client -> do
    rbp <- atomically $ readTVar (remotesByPeer state)
    jids <- configText ConfigFiles.getBuddies (clientUser client)
    let hosts = map ((\(_,h,_)->h) . splitJID) jids
    addrs <- resolveAllPeers hosts 
    let onlines = rbp `Map.intersection` Map.mapKeys PeerKey addrs
        ClientKey laddr = k
    mcon <- atomically $ do ktc <- readTVar (keyToChan state)
                            return $ Map.lookup k ktc
    flip (maybe $ return ()) mcon $ \con -> do
    forM_ (Map.toList onlines) $ \(pk, umap) -> do
        forM_ (Map.toList umap) $ \(user,rp) -> do
        let h = peerKeyToText pk
        forM_ (Map.toList $ resources rp) $ \(resource,stanza) -> do
        let jid = unsplitJID (Just user,h,Just resource)
        (mine,js) <- multiplyJIDForClient laddr jid
        forM_ js $ \jid -> do
        let from' = unsplitJID jid
        dup <- cloneStanza stanza
        sendModifiedStanzaToClient (dup { stanzaFrom=Just from' })
                                   (connChan con)

    pending <- configText ConfigFiles.getPending (clientUser client)
    hostname <- textHostName
    forM_ pending $ \pending_jid -> do
        let cjid = unsplitJID ( Just $ clientUser client
                              , hostname
                              , Nothing )
        ask <- presenceSolicitation pending_jid cjid
        sendModifiedStanzaToClient ask (connChan con)

    -- Note: relying on self peer connection to send
    -- send local buddies.
    return ()

addToRosterFile doit whose to addrs =
    modifyRosterFile doit whose to addrs True

removeFromRosterFile doit whose to addrs =
    modifyRosterFile doit whose to addrs False

modifyRosterFile doit whose to addrs bAdd = do
    let (mu,_,_) = splitJID to
        cmp jid = runTraversableT $ do
            let (msu,stored_h,mr) = splitJID (lazyByteStringToText jid)
            -- Delete from file if a resource is present in file
            (\f -> maybe f (const mzero) mr) $ do
            -- Delete from file if no user is present in file
            flip (maybe mzero) msu $ \stored_u -> do
            -- do not delete anything if no user was specified
            flip (maybe $ return jid) mu $ \u -> do
            -- do not delete if stored user is same as specified
            if stored_u /= u then return jid else do
            stored_addrs <- lift $ resolvePeer stored_h
            -- do not delete if failed to resolve
            if null stored_addrs then return jid else do
            -- delete if specified address matches stored
            if null (stored_addrs \\ addrs) then mzero else do
            -- keep
            return jid
    doit (textToLazyByteString whose)
         cmp
         (guard bAdd >> Just (textToLazyByteString to))

clientSubscriptionRequest :: PresenceState -> IO () -> ConnectionKey -> Stanza -> TChan Stanza -> IO ()
clientSubscriptionRequest state fail k stanza chan = do
    forClient state k fail $ \client -> do
    flip (maybe fail) (stanzaTo stanza) $ \to -> do
    putStrLn $ "Forwarding solictation to peer"
    let (mu,h,_) = splitJID to
    to <- return $ unsplitJID (mu,h,Nothing) -- delete resource
    flip (maybe fail) mu $ \u -> do
    addrs <- resolvePeer h
    if null addrs then fail else do
    -- add to-address to from's solicited
    addToRosterFile ConfigFiles.modifySolicited (clientUser client) to addrs
    removeFromRosterFile ConfigFiles.modifyBuddies (clientUser client) to addrs
    resolved_subs <- resolvedFromRoster ConfigFiles.getSubscribers (clientUser client)
    let is_subscribed = not . null $ intersect (map ((mu,).PeerKey) addrs) resolved_subs
    -- subscribers: "from"
    -- buddies: "to"

    (ktc,ap) <- atomically $ 
        liftM2 (,) (readTVar $ keyToChan state)
                   (readTVar $ associatedPeers state)
    
    case stanzaType stanza of
     PresenceRequestSubscription True -> do
        hostname <- textHostName
        let cjid = unsplitJID (Just $ clientUser client, hostname,Nothing)
        chans <- clientCons state ktc (clientUser client)
        forM_ chans $ \( Conn { connChan=chan }, client ) -> do
            -- roster update ask="subscribe"
            update <- makeRosterUpdate cjid to
                [ ("ask","subscribe")
                , if is_subscribed then ("subscription","from")
                                   else ("subscription","none")
                ]
            sendModifiedStanzaToClient update chan
     _ -> return ()

    let dsts = Map.fromList $ map ((,()) . PeerKey) addrs
        cdsts = ktc `Map.intersection` dsts
    forM_ (Map.toList cdsts) $ \(pk,con) -> do
        -- if already connected, send solicitation ...
        -- let from = clientJID con client
        let from = unsplitJID ( Just $ clientUser client
                              , addrToText $ auxAddr con
                              , Nothing )
        mb <- rewriteJIDForPeer to
        flip (maybe $ return ()) mb $ \(to',addr) -> do
        dup <- cloneStanza stanza
        sendModifiedStanzaToPeer (dup { stanzaTo = Just to'
                                      , stanzaFrom = Just from })
                                 (connChan con)
    let addrm = Map.fromList (map (,()) addrs)
    when (not . Map.null $ addrm Map.\\ ap) $ do
        -- Add peer if we are not already associated ...
        sv <- atomically $ takeTMVar $ server state
        addPeer sv (head addrs)
        atomically $ putTMVar (server state) sv


resolvedFromRoster
  :: (L.ByteString -> IO [L.ByteString])
     -> UserName -> IO [(Maybe UserName, ConnectionKey)]
resolvedFromRoster doit u = do
    subs <- configText doit u
    runTraversableT $ do
            (mu,h,_) <- liftT $ splitJID `fmap` subs
            addr <- liftMT $ fmap nub $ resolvePeer h
            return (mu,PeerKey addr)

clientCons state ktc u = do
    mlp <- atomically $ do
            cmap <- readTVar $ clientsByUser state
            return $ Map.lookup u cmap
    let ks = do lp <- maybeToList mlp
                Map.toList (networkClients lp)
        doit (k,client) = do
            con <- Map.lookup k ktc
            return (con,client)
    return $ mapMaybe doit ks

peerSubscriptionRequest :: PresenceState -> IO () -> ConnectionKey -> Stanza -> TChan Stanza -> IO ()
peerSubscriptionRequest state fail k stanza chan = do
    putStrLn $ "Handling pending subscription from remote"
    flip (maybe fail) (stanzaFrom stanza) $ \from -> do
    flip (maybe fail) (stanzaTo stanza) $ \to -> do
    let (mto_u,h,_) = splitJID to
        (mfrom_u,from_h,_) = splitJID from
    to <- return $ unsplitJID (mto_u,h,Nothing) -- delete resource
    from <- return $ unsplitJID (mfrom_u,from_h,Nothing) -- delete resource
    ktc <- atomically . readTVar $ keyToChan state
    flip (maybe fail) (Map.lookup k ktc)
         $ \Conn { auxAddr=laddr } -> do
    (mine,totup) <- rewriteJIDForClient laddr to []
    if not mine then fail else do
    (_,fromtup) <- rewriteJIDForClient laddr from []
    flip (maybe fail) mto_u $ \u -> do
    flip (maybe fail) mfrom_u $ \from_u -> do
    resolved_subs <- resolvedFromRoster ConfigFiles.getSubscribers u
    let already_subscribed = elem (mfrom_u,k) resolved_subs
        is_wanted = case stanzaType stanza of
                      PresenceRequestSubscription b -> b
                      _ -> False -- Shouldn't happen.
    --    Section 8 says (for presence of type "subscribe", the server MUST
    --    adhere to the rules defined under Section 3 and summarized under
    --    see Appendix A. (pariticularly Appendex A.3.1)
    if already_subscribed == is_wanted
     then do
        -- contact ∈ subscribers --> SHOULD NOT, already handled
        -- already subscribed, reply and quit
        -- (note: swapping to and from for reply)
        reply <- makeInformSubscription "jabber:server" to from is_wanted
        sendModifiedStanzaToPeer reply chan
        answerProbe state (Just to) k chan
     else do

    -- TODO: if peer-connection is to self, then auto-approve local user.
    
    -- add from-address to to's pending
    addrs <- resolvePeer from_h

    -- Catch exception in case the user does not exist
    if null addrs then fail else do

    let from' = unsplitJID fromtup

    already_pending <-
      if is_wanted then
        addToRosterFile ConfigFiles.modifyPending u from' addrs
      else do
        removeFromRosterFile ConfigFiles.modifySubscribers u from' addrs
        reply <- makeInformSubscription "jabber:server" to from is_wanted
        sendModifiedStanzaToPeer reply chan
        return False

    -- contact ∉ subscribers & contact ∈ pending --> SHOULD NOT
    when (not already_pending) $ do
    -- contact ∉ subscribers & contact ∉ pending --> MUST

    chans <- clientCons state ktc u
    forM_ chans $ \( Conn { connChan=chan }, client ) -> do
    -- send to clients
    -- TODO: interested/available clients only?
    dup <- cloneStanza stanza
    sendModifiedStanzaToClient dup { stanzaFrom = Just $ from'
                                   , stanzaTo = Just $ unsplitJID totup }
                               chan


clientInformSubscription state fail k stanza = do
    forClient state k fail $ \client -> do
    flip (maybe fail) (stanzaTo stanza) $ \to -> do
    putStrLn $ "clientInformSubscription"
    let (mu,h,mr) = splitJID to
    addrs <- resolvePeer h
    -- remove from pending
    buds <- resolvedFromRoster ConfigFiles.getBuddies (clientUser client)
    let is_buddy = not . null $ map ((mu,) . PeerKey) addrs `intersect` buds
    removeFromRosterFile ConfigFiles.modifyPending (clientUser client) to addrs
    let (relationship,addf,remf) =
         case stanzaType stanza of
           PresenceInformSubscription True ->
                ( ("subscription", if is_buddy then "both"
                                               else "from" )
                , ConfigFiles.modifySubscribers
                , ConfigFiles.modifyOthers )
           _ -> ( ("subscription", if is_buddy then "to"
                                               else "none" )
                , ConfigFiles.modifyOthers
                , ConfigFiles.modifySubscribers )
    addToRosterFile      addf (clientUser client) to addrs
    removeFromRosterFile remf (clientUser client) to addrs

    do
        cbu <- atomically $ readTVar (clientsByUser state)
        putStrLn $ "cbu = " ++ show (fmap (fmap clientPid . networkClients) cbu)

    -- send roster update to clients
    (clients,ktc) <- atomically $ do
        cbu <- readTVar (clientsByUser state)
        let mlp = Map.lookup (clientUser client) cbu
        let cs = maybe [] (Map.toList . networkClients) mlp
        ktc <- readTVar (keyToChan state)
        return (cs,ktc)
    forM_ clients $ \(ck, client) -> do
        is_intereseted <- atomically $ clientIsInterested client
        putStrLn $ "clientIsInterested: "++show is_intereseted
        is_intereseted <- atomically $ clientIsInterested client
        when is_intereseted $ do
        flip (maybe $ return ()) (Map.lookup ck ktc) $ \con -> do
        hostname <- textHostName
        -- TODO: Should cjid include the resource?
        let cjid = unsplitJID (mu, hostname, Nothing)
        update <- makeRosterUpdate cjid to [relationship]
        sendModifiedStanzaToClient update (connChan con)

    -- notify peer
    let dsts = Map.fromList $ map ((,()) . PeerKey) addrs
        cdsts = ktc `Map.intersection` dsts
    forM_ (Map.toList cdsts) $ \(pk,con) -> do
        let from = clientJID con client
            to' = unsplitJID (mu, peerKeyToText pk, Nothing)
        dup <- cloneStanza stanza
        sendModifiedStanzaToPeer (dup { stanzaTo = Just $ to'
                                      , stanzaFrom = Just from })
                                 (connChan con)
        answerProbe state (Just from) pk (connChan con)
    
peerInformSubscription state fail k stanza = do
    putStrLn $ "TODO: peerInformSubscription"
    -- remove from solicited
    flip (maybe fail) (stanzaFrom stanza) $ \from -> do
    ktc <- atomically $ readTVar (keyToChan state)
    flip (maybe fail) (Map.lookup k ktc)
        $ \(Conn { connChan=sender_chan
                 , auxAddr=laddr }) -> do
    (_,(from_u,from_h,_)) <- rewriteJIDForClient laddr from []
    let from'' = unsplitJID (from_u,from_h,Nothing)
        muser = do
            to <- stanzaTo stanza
            let (mu,to_h,to_r) = splitJID to
            mu
    -- TODO muser = Nothing when wanted=False
    -- should probably mean unsubscribed for all users.
    -- This would allow us to answer anonymous probes with 'unsubscribed'.
    flip (maybe fail) muser $ \user -> do
    addrs <- resolvePeer from_h
    was_solicited <- removeFromRosterFile ConfigFiles.modifySolicited user from'' addrs
    subs <- resolvedFromRoster ConfigFiles.getSubscribers user
    let is_sub = not . null $ map ((from_u,) . PeerKey) addrs `intersect` subs
    let (relationship,addf,remf) =
         case stanzaType stanza of
           PresenceInformSubscription True ->
                ( ("subscription", if is_sub then "both"
                                             else "to" )
                , ConfigFiles.modifyBuddies
                , ConfigFiles.modifyOthers )
           _ -> ( ("subscription", if is_sub then "from"
                                             else "none")
                , ConfigFiles.modifyOthers
                , ConfigFiles.modifyBuddies )
    addToRosterFile      addf user from'' addrs
    removeFromRosterFile remf user from'' addrs

    hostname <- textHostName
    let to' = unsplitJID (Just user, hostname, Nothing)
    chans <- clientCons state ktc user
    forM_ chans $ \(Conn { connChan=chan }, client) -> do
    update <- makeRosterUpdate to' from'' [relationship]
    is_intereseted <- atomically $ clientIsInterested client
    when is_intereseted $ do
        sendModifiedStanzaToClient update chan
    -- TODO: interested/availabe clients only?
    dup <- cloneStanza stanza
    sendModifiedStanzaToClient dup { stanzaFrom = Just $ from''
                                   , stanzaTo = Just to' }
                               chan

main = runResourceT $ do
    state <- liftIO . atomically $ do
        clients <- newTVar Map.empty
        clientsByUser <- newTVar Map.empty
        remotesByPeer <- newTVar Map.empty
        associatedPeers <- newTVar Map.empty
        xmpp <- newEmptyTMVar
        keyToChan <- newTVar Map.empty
        return PresenceState
            { clients = clients
            , clientsByUser = clientsByUser
            , remotesByPeer = remotesByPeer
            , associatedPeers = associatedPeers
            , keyToChan = keyToChan
            , server = xmpp
            }
    sv <- xmppServer
        XMPPServerParameters
        { xmppChooseResourceName = chooseResourceName state
        , xmppTellClientHisName = tellClientHisName state
        , xmppTellMyNameToClient = textHostName
        , xmppTellMyNameToPeer = \addr -> return $ addrToText addr
        , xmppTellPeerHisName = return . peerKeyToText
        , xmppTellClientNameOfPeer = flip peerKeyToResolvedName
        , xmppNewConnection = newConn state
        , xmppEOF = eofConn state
        , xmppRosterBuddies = rosterGetBuddies state
        , xmppRosterSubscribers = rosterGetSubscribers state
        , xmppRosterSolicited = rosterGetSolicited state
        , xmppRosterOthers = rosterGetOthers state
        , xmppSubscribeToRoster = informSentRoster state
        , xmppDeliverMessage = deliverMessage state
        , xmppInformClientPresence = informClientPresence state
        , xmppInformPeerPresence = informPeerPresence state
        , xmppAnswerProbe = \k stanza chan -> answerProbe state (stanzaTo stanza) k chan
        , xmppClientSubscriptionRequest = clientSubscriptionRequest state
        , xmppPeerSubscriptionRequest = peerSubscriptionRequest state
        , xmppClientInformSubscription = clientInformSubscription state
        , xmppPeerInformSubscription = peerInformSubscription state
        }
    liftIO $ do
    atomically $ putTMVar (server state) sv

    quitVar <- newEmptyTMVarIO
    installHandler sigTERM (CatchOnce (atomically $ putTMVar quitVar True)) Nothing
    installHandler sigINT (CatchOnce (atomically $ putTMVar quitVar True)) Nothing
    quitMessage <- atomically $ takeTMVar quitVar

    putStrLn "goodbye."
    return ()