/*
 * Copyright (C) 2005-2008 Jive Software. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jivesoftware.openfire.spi;

import org.dom4j.Element;
import org.dom4j.QName;
import org.jivesoftware.openfire.IQRouter;
import org.jivesoftware.openfire.MessageRouter;
import org.jivesoftware.openfire.PacketException;
import org.jivesoftware.openfire.PresenceRouter;
import org.jivesoftware.openfire.RemotePacketRouter;
import org.jivesoftware.openfire.RoutableChannelHandler;
import org.jivesoftware.openfire.RoutingTable;
import org.jivesoftware.openfire.SessionManager;
import org.jivesoftware.openfire.XMPPServer;
import org.jivesoftware.openfire.auth.UnauthorizedException;
import org.jivesoftware.openfire.carbons.Received;
import org.jivesoftware.openfire.cluster.ClusterEventListener;
import org.jivesoftware.openfire.cluster.ClusterManager;
import org.jivesoftware.openfire.cluster.NodeID;
import org.jivesoftware.openfire.component.ExternalComponentManager;
import org.jivesoftware.openfire.container.BasicModule;
import org.jivesoftware.openfire.forward.Forwarded;
import org.jivesoftware.openfire.handler.PresenceUpdateHandler;
import org.jivesoftware.openfire.server.OutgoingSessionPromise;
import org.jivesoftware.openfire.server.RemoteServerManager;
import org.jivesoftware.openfire.session.ClientSession;
import org.jivesoftware.openfire.session.ConnectionSettings;
import org.jivesoftware.openfire.session.DomainPair;
import org.jivesoftware.openfire.session.LocalClientSession;
import org.jivesoftware.openfire.session.LocalOutgoingServerSession;
import org.jivesoftware.openfire.session.OutgoingServerSession;
import org.jivesoftware.openfire.session.RemoteSessionLocator;
import org.jivesoftware.util.JiveGlobals;
import org.jivesoftware.util.cache.Cache;
import org.jivesoftware.util.cache.CacheFactory;
import org.jivesoftware.util.cache.CacheUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xmpp.packet.IQ;
import org.xmpp.packet.JID;
import org.xmpp.packet.Message;
import org.xmpp.packet.Packet;
import org.xmpp.packet.Presence;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.locks.Lock;

/**
 * Routing table that stores routes to client sessions, outgoing server sessions
 * and components. As soon as a user authenticates with the server its client session
 * will be added to the routing table. Whenever the client session becomes available
 * or unavailable the routing table will be updated too.<p>
 *
 * When running inside of a cluster the routing table will also keep references to routes
 * hosted in other cluster nodes. A {@link RemotePacketRouter} will be use to route packets
 * to routes hosted in other cluster nodes.<p>
 *
 * Failure to route a packet will end up sending {@link IQRouter#routingFailed(JID, Packet)},
 * {@link MessageRouter#routingFailed(JID, Packet)} or {@link PresenceRouter#routingFailed(JID, Packet)}
 * depending on the packet type that tried to be sent.
 *
 * @author Gaston Dombiak
 */
public class RoutingTableImpl extends BasicModule implements RoutingTable, ClusterEventListener {

    private static final Logger Log = LoggerFactory.getLogger(RoutingTableImpl.class);
    
    public static final String C2S_CACHE_NAME = "Routing Users Cache";
    public static final String ANONYMOUS_C2S_CACHE_NAME = "Routing AnonymousUsers Cache";
    public static final String S2S_CACHE_NAME = "Routing Servers Cache";
    public static final String COMPONENT_CACHE_NAME = "Routing Components Cache";
    public static final String C2S_SESSION_NAME = "Routing User Sessions";

    /**
     * Cache (unlimited, never expire) that holds outgoing sessions to remote servers from this server.
     * Key: server domain pair, Value: nodeID
     */
    private Cache<DomainPair, NodeID> serversCache;
    /**
     * Cache (unlimited, never expire) that holds components connected to the server.
     * Key: component domain, Value: list of nodeIDs hosting the component
     */
    private Cache<String, HashSet<NodeID>> componentsCache;
    /**
     * Cache (unlimited, never expire) that holds sessions of user that have authenticated with the server.
     * Key: full JID, Value: {nodeID, available/unavailable}
     */
    private Cache<String, ClientRoute> usersCache;
    /**
     * Cache (unlimited, never expire) that holds sessions of anonymous user that have authenticated with the server.
     * Key: full JID, Value: {nodeID, available/unavailable}
     */
    private Cache<String, ClientRoute> anonymousUsersCache;
    /**
     * Cache (unlimited, never expire) that holds set of connected resources of authenticated users
     * (includes anonymous).
     * Key: bare JID, Value: set of full JIDs of the user
     */
    private Cache<String, HashSet<String>> usersSessions;

    private String serverName;
    private XMPPServer server;
    private LocalRoutingTable localRoutingTable;
    private RemotePacketRouter remotePacketRouter;
    private IQRouter iqRouter;
    private MessageRouter messageRouter;
    private PresenceRouter presenceRouter;
    private PresenceUpdateHandler presenceUpdateHandler;

    public RoutingTableImpl() {
        super("Routing table");
        serversCache = CacheFactory.createCache(S2S_CACHE_NAME);
        componentsCache = CacheFactory.createCache(COMPONENT_CACHE_NAME);
        usersCache = CacheFactory.createCache(C2S_CACHE_NAME);
        anonymousUsersCache = CacheFactory.createCache(ANONYMOUS_C2S_CACHE_NAME);
        usersSessions = CacheFactory.createCache(C2S_SESSION_NAME);
        localRoutingTable = new LocalRoutingTable();
    }

    @Override
    public void addServerRoute(DomainPair address, LocalOutgoingServerSession destination) {
        localRoutingTable.addRoute(address, destination);
        Lock lock = serversCache.getLock(address);
        try {
            lock.lock();
            serversCache.put(address, server.getNodeID());
        }
        finally {
            lock.unlock();
        }
    }

    @Override
    public void addComponentRoute(JID route, RoutableChannelHandler destination) {
        DomainPair pair = new DomainPair("", route.getDomain());
        String address = route.getDomain();
        localRoutingTable.addRoute(pair, destination);
        Lock lock = componentsCache.getLock(address);
        try {
            lock.lock();
            HashSet<NodeID> nodes = componentsCache.get(address);
            if (nodes == null) {
                nodes = new HashSet<>();
            }
            nodes.add(server.getNodeID());
            componentsCache.put(address, nodes);
        } finally {
            lock.unlock();
        }
    }

    @Override
    public boolean addClientRoute(JID route, LocalClientSession destination) {
        boolean added;
        boolean available = destination.getPresence().isAvailable();
        Log.debug("Adding client route {}", route);
        localRoutingTable.addRoute(new DomainPair("", route.toString()), destination);
        if (destination.getAuthToken().isAnonymous()) {
            Lock lockAn = anonymousUsersCache.getLock(route.toString());
            try {
                lockAn.lock();
                added = anonymousUsersCache.put(route.toString(), new ClientRoute(server.getNodeID(), available)) ==
                        null;
            }
            finally {
                lockAn.unlock();
            }
            // Add the session to the list of user sessions
            if (route.getResource() != null && (!available || added)) {
                Lock lock = usersSessions.getLock(route.toBareJID());
                try {
                    lock.lock();
                    usersSessions.put(route.toBareJID(), new HashSet<>(Collections.singletonList(route.toString())));
                }
                finally {
                    lock.unlock();
                }
            }
        }
        else {
            Lock lockU = usersCache.getLock(route.toString());
            try {
                lockU.lock();
                added = usersCache.put(route.toString(), new ClientRoute(server.getNodeID(), available)) == null;
            }
            finally {
                lockU.unlock();
            }
            // Add the session to the list of user sessions
            if (route.getResource() != null && (!available || added)) {
                Lock lock = usersSessions.getLock(route.toBareJID());
                try {
                    lock.lock();
                    HashSet<String> jids = usersSessions.get(route.toBareJID());
                    if (jids == null) {
                        jids = new HashSet<>();
                    }
                    jids.add(route.toString());
                    usersSessions.put(route.toBareJID(), jids);
                }
                finally {
                    lock.unlock();
                }
            }
        }
        return added;
    }

    @Override
    public void broadcastPacket(Message packet, boolean onlyLocal) {
        // Send the message to client sessions connected to this JVM
        for(ClientSession session : localRoutingTable.getClientRoutes()) {
            session.process(packet);
        }

        // Check if we need to broadcast the message to client sessions connected to remote cluter nodes
        if (!onlyLocal && remotePacketRouter != null) {
            remotePacketRouter.broadcastPacket(packet);
        }
    }

    /*
     * (non-Javadoc)
     * @see org.jivesoftware.openfire.RoutingTable#routePacket(org.xmpp.packet.JID, org.xmpp.packet.Packet, boolean)
     * 
     * @param jid the recipient of the packet to route.
     * @param packet the packet to route.
     * @param fromServer true if the packet was created by the server. This packets should
     *        always be delivered
     * @throws PacketException thrown if the packet is malformed (results in the sender's
     *      session being shutdown).
     */
    @Override
    public void routePacket(JID jid, Packet packet, boolean fromServer) throws PacketException {
        boolean routed = false;
        try {
            if (serverName.equals(jid.getDomain())) {
                // Packet sent to our domain.
                routed = routeToLocalDomain(jid, packet, fromServer);
            }
            else if (jid.getDomain().endsWith(serverName) && hasComponentRoute(jid)) {
                // Packet sent to component hosted in this server
                routed = routeToComponent(jid, packet);
            }
            else {
                // Packet sent to remote server
                routed = routeToRemoteDomain(jid, packet);
            }
        } catch (Exception ex) {
            // Catch here to ensure that all packets get handled, despite various processing
            // exceptions, rather than letting any fall through the cracks. For example,
            // an IAE could be thrown when running in a cluster if a remote member becomes 
            // unavailable before the routing caches are updated to remove the defunct node.
            // We have also occasionally seen various flavors of NPE and other oddities, 
            // typically due to unexpected environment or logic breakdowns. 
            Log.error("Primary packet routing failed", ex); 
        }

        if (!routed) {
            if (Log.isDebugEnabled()) {
                Log.debug("Failed to route packet to JID: {} packet: {}", jid, packet.toXML());
            }
            if (packet instanceof IQ) {
                iqRouter.routingFailed(jid, packet);
            }
            else if (packet instanceof Message) {
                messageRouter.routingFailed(jid, packet);
            }
            else if (packet instanceof Presence) {
                presenceRouter.routingFailed(jid, packet);
            }
        }
    }

    /**
     * Routes packets that are sent to the XMPP domain itself (excluding subdomains).
     * 
     * @param jid
     *            the recipient of the packet to route.
     * @param packet
     *            the packet to route.
     * @param fromServer
     *            true if the packet was created by the server. This packets
     *            should always be delivered
     * @throws PacketException
     *             thrown if the packet is malformed (results in the sender's
     *             session being shutdown).
     * @return {@code true} if the packet was routed successfully,
     *         {@code false} otherwise.
     */
    private boolean routeToLocalDomain(JID jid, Packet packet,
            boolean fromServer) {
        boolean routed = false;
        Element privateElement = packet.getElement().element(QName.get("private", Received.NAMESPACE));
        boolean isPrivate = privateElement != null;
        // The receiving server and SHOULD remove the <private/> element before delivering to the recipient.
        packet.getElement().remove(privateElement);

        if (jid.getResource() == null) {
            // Packet sent to a bare JID of a user
            if (packet instanceof Message) {
                // Find best route of local user
                routed = routeToBareJID(jid, (Message) packet, isPrivate);
            }
            else {
                throw new PacketException("Cannot route packet of type IQ or Presence to bare JID: " + packet.toXML());
            }
        }
        else {
            // Packet sent to local user (full JID)
            ClientRoute clientRoute = getClientRouteForLocalUser(jid);
            if (clientRoute != null) {
                if (!clientRoute.isAvailable() && routeOnlyAvailable(packet, fromServer) &&
		                !presenceUpdateHandler.hasDirectPresence(packet.getTo(), packet.getFrom())
                        && !PresenceUpdateHandler.isPresenceUpdateReflection( packet )) {
                    Log.debug("Unable to route packet. Packet should only be sent to available sessions and the route is not available. {} ", packet.toXML());
                    routed = false;
                } else {
                    if (localRoutingTable.isLocalRoute(jid)) {
                        if (!isPrivate && packet instanceof Message) {
                            ccMessage(jid, (Message) packet);
                        }

                        // This is a route to a local user hosted in this node
                        try {
                            localRoutingTable.getRoute(jid).process(packet);
                            routed = true;
                        } catch (UnauthorizedException e) {
                            Log.error("Unable to route packet " + packet.toXML(), e);
                        }
                    }
                    else {
                        // This is a route to a local user hosted in other node
                        if (remotePacketRouter != null) {
                            routed = remotePacketRouter
                                    .routePacket(clientRoute.getNodeID().toByteArray(), jid, packet);
                            if (!routed) {
                                removeClientRoute(jid); // drop invalid client route
                            }
                        }
                    }
                }
            }
        }
        return routed;
    }

    private void ccMessage(JID originalRecipient, Message message) {
        // We don't want to CC a message that is already a CC
        final Element receivedElement = message.getChildElement(Received.NAME, Received.NAMESPACE);
        final boolean isCC = receivedElement != null;
        if (message.getType() == Message.Type.chat && !isCC) {
            List<JID> routes = getRoutes(originalRecipient.asBareJID(), null);
            for (JID ccJid : routes) {
                // The receiving server MUST NOT send a forwarded copy to the full JID the original <message/> stanza was addressed to, as that recipient receives the original <message/> stanza.
                if (!ccJid.equals(originalRecipient)) {
                    ClientSession clientSession = getClientRoute(ccJid);
                    if (clientSession.isMessageCarbonsEnabled()) {
                        Message carbon = new Message();
                        // The wrapping message SHOULD maintain the same 'type' attribute value;
                        carbon.setType(message.getType());
                        // the 'from' attribute MUST be the Carbons-enabled user's bare JID
                        carbon.setFrom(ccJid.asBareJID());
                        // and the 'to' attribute MUST be the full JID of the resource receiving the copy
                        carbon.setTo(ccJid);
                        // The content of the wrapping message MUST contain a <received/> element qualified by the namespace "urn:xmpp:carbons:2", which itself contains a <forwarded/> element qualified by the namespace "urn:xmpp:forward:0" that contains the original <message/>.
                        carbon.addExtension(new Received(new Forwarded(message)));

                        try {
                            final RoutableChannelHandler localRoute = localRoutingTable.getRoute(ccJid);
                            if (localRoute != null) {
                                // This session is on a local cluster node
                                localRoute.process(carbon);
                            } else {
                                // The session is not on a local cluster node, so try a remote
                                final ClientRoute remoteRoute = getClientRouteForLocalUser(ccJid);
                                if (remotePacketRouter != null // If we're in a cluster
                                    && remoteRoute != null // and we've found a route to the other node
                                    && !remoteRoute.getNodeID().equals(XMPPServer.getInstance().getNodeID())) { // and it really is a remote node
                                    // Try and route the packet to the remote session
                                    remotePacketRouter.routePacket(remoteRoute.getNodeID().toByteArray(), ccJid, carbon);
                                } else {
                                    Log.warn("Unable to find route to CC remote user {}", ccJid);
                                }
                            }
                        } catch (UnauthorizedException e) {
                            Log.error("Unable to route packet {}", message, e);
                        }
                    }
                }
            }
        }
    }

    private ClientRoute getClientRouteForLocalUser(JID jid) {
        ClientRoute clientRoute = usersCache.get(jid.toString());
        if (clientRoute == null) {
            clientRoute = anonymousUsersCache.get(jid.toString());
        }
        return clientRoute;
    }

    /**
     * Routes packets that are sent to components of the XMPP domain (which are
     * subdomains of the XMPP domain)
     * 
     * @param jid
     *            the recipient of the packet to route.
     * @param packet
     *            the packet to route.
     * @throws PacketException
     *             thrown if the packet is malformed (results in the sender's
     *             session being shutdown).
     * @return {@code true} if the packet was routed successfully,
     *         {@code false} otherwise.
     */
    private boolean routeToComponent(JID jid, Packet packet) {
        if (!hasComponentRoute(jid) 
                && !ExternalComponentManager.hasConfiguration(jid.getDomain())) {
            return false;
        }
        
        // First check if the component is being hosted in this JVM
        boolean routed = false;
        RoutableChannelHandler route = localRoutingTable.getRoute(new JID(null, jid.getDomain(), null, true));
        if (route != null) {
            try {
                route.process(packet);
                routed = true;
            } catch (UnauthorizedException e) {
                Log.error("Unable to route packet " + packet.toXML(), e);
            }
        }
        else {
            // Check if other cluster nodes are hosting this component
            Set<NodeID> nodes = componentsCache.get(jid.getDomain());
            if (nodes != null) {
                for (NodeID nodeID : nodes) {
                    if (server.getNodeID().equals(nodeID)) {
                        // This is a route to a local component hosted in this node (route
                        // could have been added after our previous check)
                        try {
                            RoutableChannelHandler localRoute = localRoutingTable.getRoute(new JID(null, jid.getDomain(), null, true));
                            if (localRoute != null) {
                                localRoute.process(packet);
                                routed = true;
                                break;
                            }
                        } catch (UnauthorizedException e) {
                            Log.error("Unable to route packet " + packet.toXML(), e);
                        }
                    }
                    else {
                        // This is a route to a local component hosted in other node
                        if (remotePacketRouter != null) {
                            routed = remotePacketRouter.routePacket(nodeID.toByteArray(), jid, packet);
                            if (routed) {
                                break;
                            }
                        }
                    }
                }
            }
        }
        return routed;
    }

    /**
     * Routes packets that are sent to other XMPP domains than the local XMPP
     * domain.
     * 
     * @param jid
     *            the recipient of the packet to route.
     * @param packet
     *            the packet to route.
     * @throws PacketException
     *             thrown if the packet is malformed (results in the sender's
     *             session being shutdown).
     * @return {@code true} if the packet was routed successfully,
     *         {@code false} otherwise.
     */
    private boolean routeToRemoteDomain(JID jid, Packet packet) {
        if ( !JiveGlobals.getBooleanProperty( ConnectionSettings.Server.ALLOW_ANONYMOUS_OUTBOUND_DATA, false ) )
        {
            // Disallow anonymous local users to send data to other domains than the local domain.
            if ( isAnonymousRoute( packet.getFrom() ) )
            {
                Log.info( "The anonymous user '{}' attempted to send data to '{}', which is on a remote domain. Openfire is configured to not allow anonymous users to send data to remote domains.", packet.getFrom(), jid );
                return false;
            }
        }

        boolean routed = false;
        DomainPair pair = new DomainPair(packet.getFrom().getDomain(), jid.getDomain());
        NodeID nodeID = serversCache.get(pair);
        if (nodeID != null) {
            if (server.getNodeID().equals(nodeID)) {
                // This is a route to a remote server connected from this node
                try {
                    localRoutingTable.getRoute(pair).process(packet);
                    routed = true;
                } catch (UnauthorizedException e) {
                    Log.error("Unable to route packet " + packet.toXML(), e);
                }
            }
            else {
                // This is a route to a remote server connected from other node
                if (remotePacketRouter != null) {
                    routed = remotePacketRouter.routePacket(nodeID.toByteArray(), jid, packet);
                }
            }
        }
        else if (!RemoteServerManager.canAccess(jid.getDomain())) { // Check if the remote domain is in the blacklist
            Log.info( "Will not route: Remote domain {} is not accessible according to our configuration (typical causes: server federation is disabled, or domain is blacklisted).", jid.getDomain() );
            routed = false;
        }
        else {
            // Return a promise of a remote session. This object will queue packets pending
            // to be sent to remote servers
            OutgoingSessionPromise.getInstance().process(packet);
            routed = true;
        }
        return routed;
    }
    
    /**
     * Returns true if the specified packet must only be route to available client sessions.
     *
     * @param packet the packet to route.
     * @param fromServer true if the packet was created by the server.
     * @return true if the specified packet must only be route to available client sessions.
     */
    private boolean routeOnlyAvailable(Packet packet, boolean fromServer) {
        if (fromServer) {
            // Packets created by the server (no matter their FROM value) must always be delivered no
            // matter the available presence of the user
            return false;
        }
        boolean onlyAvailable = true;
        JID from = packet.getFrom();
        boolean hasSender = from != null;
        if (packet instanceof IQ) {
            onlyAvailable = hasSender && !(serverName.equals(from.getDomain()) && from.getResource() == null) &&
                    !componentsCache.containsKey(from.getDomain());
        }
        else if (packet instanceof Message || packet instanceof Presence) {
            onlyAvailable = !hasSender ||
                    (!serverName.equals(from.toString()) && !componentsCache.containsKey(from.getDomain()));
        }
        return onlyAvailable;
    }

    /**
     * Deliver the message sent to the bare JID of a local user to the best connected resource. If the
     * target user is not online then messages will be stored offline according to the offline strategy.
     * However, if the user is connected from only one resource then the message will be delivered to
     * that resource. In the case that the user is connected from many resources the logic will be the
     * following:
     * <ol>
     *  <li>Select resources with highest priority</li>
     *  <li>Select resources with highest show value (chat, available, away, xa, dnd)</li>
     *  <li>Select resource with most recent activity</li>
     * </ol>
     *
     * Admins can override the above logic and just send the message to all connected resources
     * with highest priority by setting the system property {@code route.all-resources} to
     * {@code true}.
     *
     * @param recipientJID the bare JID of the target local user.
     * @param packet the message to send.
     * @return true if at least one target session was found
     */
    private boolean routeToBareJID(JID recipientJID, Message packet, boolean isPrivate) {
        List<ClientSession> sessions = new ArrayList<>();
        // Get existing AVAILABLE sessions of this user or AVAILABLE to the sender of the packet
        for (JID address : getRoutes(recipientJID, packet.getFrom())) {
            ClientSession session = getClientRoute(address);
            if (session != null && session.isInitialized()) {
                sessions.add(session);
            }
        }

        // Get the sessions with non-negative priority for message carbons processing.
        List<ClientSession> nonNegativePrioritySessions = getNonNegativeSessions(sessions, 0);

        if (packet.getType() == Message.Type.error) {
            // Errors should be dropped at this point.
            Log.debug("Error stanza to bare JID discarded: {}", packet.toXML());
            return true; // Not offline.
        }

        if (packet.getType() == Message.Type.groupchat) {
            // Surreal message type; cannot occur.
            Log.debug("Groupchat stanza to bare JID discarded: {}", packet.toXML());
            return false; // Maybe offline has an idea?
        }

        if (nonNegativePrioritySessions.isEmpty()) {
            // No session is available so store offline
            Log.debug("Unable to route packet. No session is available so store offline. {} ", packet.toXML());
            return false;
        }

        // Check for message carbons enabled sessions and send the message to them.
        for (ClientSession session : nonNegativePrioritySessions) {
            if (packet.getType() == Message.Type.headline) {
                // Headline messages are broadcast.
                session.process(packet);
            // Deliver to each session, if is message carbons enabled.
            } else if (shouldCarbonCopyToResource(session, packet, isPrivate)) {
                session.process(packet);
            // Deliver to each session if property route.really-all-resources is true
            // (in case client does not support carbons)
            } else if (JiveGlobals.getBooleanProperty("route.really-all-resources", false)) {
                session.process(packet);
            }
        }

        if (packet.getType() == Message.Type.headline) {
            return true;
        }

        if (JiveGlobals.getBooleanProperty("route.really-all-resources", false)) {
            return true;
        }

        // Get the highest priority sessions for normal processing.
        List<ClientSession> highestPrioritySessions = getHighestPrioritySessions(nonNegativePrioritySessions);

        if (highestPrioritySessions.size() == 1) {
            // Found only one session so deliver message (if it hasn't already been processed because it has message carbons enabled)
            if (!shouldCarbonCopyToResource(highestPrioritySessions.get(0), packet, isPrivate)) {
                highestPrioritySessions.get(0).process(packet);
            }
        }
        else {
            // Many sessions have the highest priority (be smart now) :)
            if (!JiveGlobals.getBooleanProperty("route.all-resources", false)) {
                // Sort sessions by show value (e.g. away, xa)
                highestPrioritySessions.sort(new Comparator<ClientSession>() {

                    @Override
                    public int compare(ClientSession o1, ClientSession o2) {
                        int thisVal = getShowValue(o1);
                        int anotherVal = getShowValue(o2);
                        return (Integer.compare(thisVal, anotherVal));
                    }

                    /**
                     * Priorities are: chat, available, away, xa, dnd.
                     */
                    private int getShowValue(ClientSession session) {
                        Presence.Show show = session.getPresence().getShow();
                        if (show == Presence.Show.chat) {
                            return 1;
                        } else if (show == null) {
                            return 2;
                        } else if (show == Presence.Show.away) {
                            return 3;
                        } else if (show == Presence.Show.xa) {
                            return 4;
                        } else {
                            return 5;
                        }
                    }
                });

                // Get same sessions with same max show value
                List<ClientSession> targets = new ArrayList<>();
                Presence.Show showFilter = highestPrioritySessions.get(0).getPresence().getShow();
                for (ClientSession session : highestPrioritySessions) {
                    if (session.getPresence().getShow() == showFilter) {
                        targets.add(session);
                    }
                    else {
                        break;
                    }
                }

                // Get session with most recent activity (and highest show value)
                targets.sort((o1, o2) -> o2.getLastActiveDate().compareTo(o1.getLastActiveDate()));

                // Make sure, we don't send the packet again, if it has already been sent by message carbons.
                ClientSession session = targets.get(0);
                if (!shouldCarbonCopyToResource(session, packet, isPrivate)) {
                    // Deliver stanza to session with highest priority, highest show value and most recent activity
                    session.process(packet);
                }
            }
            else {
                for (ClientSession session : highestPrioritySessions) {
                    // Make sure, we don't send the packet again, if it has already been sent by message carbons.
                    if (!shouldCarbonCopyToResource(session, packet, isPrivate)) {
                        session.process(packet);
                    }
                }
            }
        }
        return true;
    }

    private boolean shouldCarbonCopyToResource(ClientSession session, Message message, boolean isPrivate) {
        return !isPrivate && session.isMessageCarbonsEnabled() && message.getType() == Message.Type.chat;
    }

    /**
     * Returns the sessions that had the highest presence priority that is non-negative.
     *
     * @param sessions the list of user sessions that filter and get the ones with highest priority.
     * @return the sessions that had the highest presence non-negative priority or empty collection
     *         if all were negative.
     */
    private List<ClientSession> getHighestPrioritySessions(List<ClientSession> sessions) {
        int highest = Integer.MIN_VALUE;
        // Get the highest priority amongst the sessions
        for (ClientSession session : sessions) {
            int priority = session.getPresence().getPriority();
            if (priority >= 0 && priority > highest) {
                highest = priority;
            }
        }
        // Get sessions that have the highest priority
        return getNonNegativeSessions(sessions, highest);
    }

    /**
     * Gets the non-negative session from a minimal priority.
     *
     * @param sessions The sessions.
     * @param min      The minimal priority.
     * @return The filtered sessions.
     */
    private List<ClientSession> getNonNegativeSessions(List<ClientSession> sessions, int min) {
        if (min < 0) {
            return Collections.emptyList();
        }
        // Get sessions with priority >= min
        List<ClientSession> answer = new ArrayList<>(sessions.size());
        for (ClientSession session : sessions) {
            if (session.getPresence().getPriority() >= min) {
                answer.add(session);
            }
        }
        return answer;
    }

    @Override
    public ClientSession getClientRoute(JID jid) {
        // Check if this session is hosted by this cluster node
        ClientSession session = (ClientSession) localRoutingTable.getRoute(jid);
        if (session == null) {
            // The session is not in this JVM so assume remote
            RemoteSessionLocator locator = server.getRemoteSessionLocator();
            if (locator != null) {
                // Check if the session is hosted by other cluster node
                ClientRoute route = getClientRouteForLocalUser(jid);
                if (route != null) {
                    session = locator.getClientSession(route.getNodeID().toByteArray(), jid);
                }
            }
        }
        return session;
    }

    @Override
    public Collection<ClientSession> getClientsRoutes(boolean onlyLocal) {
        // Add sessions hosted by this cluster node
        Collection<ClientSession> sessions = new ArrayList<>(localRoutingTable.getClientRoutes());
        if (!onlyLocal) {
            // Add sessions not hosted by this JVM
            RemoteSessionLocator locator = server.getRemoteSessionLocator();
            if (locator != null) {
                // Add sessions of non-anonymous users hosted by other cluster nodes
                for (Map.Entry<String, ClientRoute> entry : usersCache.entrySet()) {
                    ClientRoute route = entry.getValue();
                    if (!server.getNodeID().equals(route.getNodeID())) {
                        sessions.add(locator.getClientSession(route.getNodeID().toByteArray(), new JID(entry.getKey())));
                    }
                }
                // Add sessions of anonymous users hosted by other cluster nodes
                for (Map.Entry<String, ClientRoute> entry : anonymousUsersCache.entrySet()) {
                    ClientRoute route = entry.getValue();
                    if (!server.getNodeID().equals(route.getNodeID())) {
                        sessions.add(locator.getClientSession(route.getNodeID().toByteArray(), new JID(entry.getKey())));
                    }
                }
            }
        }
        return sessions;
    }

    @Override
    public OutgoingServerSession getServerRoute(DomainPair jids) {
        // Check if this session is hosted by this cluster node
        OutgoingServerSession session = (OutgoingServerSession) localRoutingTable.getRoute(jids);
        if (session == null) {
            // The session is not in this JVM so assume remote
            RemoteSessionLocator locator = server.getRemoteSessionLocator();
            if (locator != null) {
                // Check if the session is hosted by other cluster node
                NodeID nodeID = serversCache.get(jids);
                if (nodeID != null) {
                    session = locator.getOutgoingServerSession(nodeID.toByteArray(), jids);
                }
            }
        }
        return session;
    }

    @Override
    public Collection<String> getServerHostnames() {
        Set<String> domains = new HashSet<>();
        for (DomainPair pair : serversCache.keySet()) {
            domains.add(pair.getRemote());
        }
        return domains;
    }

    @Override
    public Collection<DomainPair> getServerRoutes() {
        return serversCache.keySet();
    }

    @Override
    public int getServerSessionsCount() {
        return localRoutingTable.getServerRoutes().size();
    }

    @Override
    public Collection<String> getComponentsDomains() {
        return componentsCache.keySet();
    }

    @Override
    public boolean hasClientRoute(JID jid) {
        return usersCache.containsKey(jid.toString()) || isAnonymousRoute(jid);
    }

    @Override
    public boolean isAnonymousRoute(JID jid) {
        if ( jid.getResource() != null ) {
            // Check if there's a anonymous route for the JID.
            return anonymousUsersCache.containsKey( jid.toString() );
        } else {
            // Anonymous routes are mapped by full JID. if there's no full JID, check for any route for the node-part.
            return anonymousUsersCache.keySet().stream().anyMatch( key -> key.startsWith( jid.toString() ) );
        }
    }

    @Override
    public boolean isLocalRoute(JID jid) {
        return localRoutingTable.isLocalRoute(jid);
    }

    @Override
    public boolean hasServerRoute(DomainPair pair) {
        return serversCache.containsKey(pair);
    }

    @Override
    public boolean hasComponentRoute(JID jid) {
        return componentsCache.containsKey(jid.getDomain());
    }

    @Override
    public List<JID> getRoutes(JID route, JID requester) {
        List<JID> jids = new ArrayList<>();
        if (serverName.equals(route.getDomain())) {
            // Address belongs to local user
            if (route.getResource() != null) {
                // Address is a full JID of a user
                ClientRoute clientRoute = getClientRouteForLocalUser(route);
                if (clientRoute != null &&
                        (clientRoute.isAvailable() || presenceUpdateHandler.hasDirectPresence(route, requester))) {
                    jids.add(route);
                }
            }
            else {
                // Address is a bare JID so return all AVAILABLE resources of user
                Lock lock = usersSessions.getLock(route.toBareJID());
                try {
                    lock.lock(); // temporarily block new sessions for this JID
                    Collection<String> sessions = usersSessions.get(route.toBareJID());
                    if (sessions != null) {
                        // Select only available sessions
                        for (String jid : sessions) {
                            ClientRoute clientRoute = usersCache.get(jid);
                            if (clientRoute == null) {
                                clientRoute = anonymousUsersCache.get(jid);
                            }
                            if (clientRoute != null && (clientRoute.isAvailable() ||
                                    presenceUpdateHandler.hasDirectPresence(new JID(jid), requester))) {
                                jids.add(new JID(jid));
                            }
                        }
                    }
                }
                finally {
                    lock.unlock();
                }
            }
        }
        else if (route.getDomain().contains(serverName)) {
            // Packet sent to component hosted in this server
            if (componentsCache.containsKey(route.getDomain())) {
                jids.add(new JID(route.getDomain()));
            }
        }
        else {
            // Packet sent to remote server
            jids.add(route);
        }
        return jids;
    }

    @Override
    public boolean removeClientRoute(JID route) {
        boolean anonymous = false;
        String address = route.toString();
        ClientRoute clientRoute;
        Lock lockU = usersCache.getLock(address);
        try {
            lockU.lock();
            clientRoute = usersCache.remove(address);
        }
        finally {
            lockU.unlock();
        }
        if (clientRoute == null) {
            Lock lockA = anonymousUsersCache.getLock(address);
            try {
                lockA.lock();
                clientRoute = anonymousUsersCache.remove(address);
                anonymous = true;
            }
            finally {
                lockA.unlock();
            }
        }
        if (clientRoute != null && route.getResource() != null) {
            Lock lock = usersSessions.getLock(route.toBareJID());
            try {
                lock.lock();
                if (anonymous) {
                    usersSessions.remove(route.toBareJID());
                }
                else {
                    HashSet<String> jids = usersSessions.get(route.toBareJID());
                    if (jids != null) {
                        jids.remove(route.toString());
                        if (!jids.isEmpty()) {
                            usersSessions.put(route.toBareJID(), jids);
                        }
                        else {
                            usersSessions.remove(route.toBareJID());
                        }
                    }
                }
            }
            finally {
                lock.unlock();
            }
        }
        Log.debug("Removing client route {}", route);
        localRoutingTable.removeRoute(new DomainPair("", route.toString()));
        return clientRoute != null;
    }

    @Override
    public boolean removeServerRoute(DomainPair route) {
        boolean removed;
        Lock lock = serversCache.getLock(route);
        try {
            lock.lock();
            removed = serversCache.remove(route) != null;
        }
        finally {
            lock.unlock();
        }
        localRoutingTable.removeRoute(route);
        return removed;
    }

    @Override
    public boolean removeComponentRoute(JID route) {
        return removeComponentRoute(route, server.getNodeID());
    }

    /**
     * Remove local or remote component route.
     *
     * @param route the route of the component to be removed.
     * @param nodeID The node to which the to-be-removed component was connected to.
     */
    private boolean removeComponentRoute(JID route, NodeID nodeID) {
        String address = route.getDomain();
        boolean removed = false;
        Lock lock = componentsCache.getLock(address);
        try {
            lock.lock();
            HashSet<NodeID> nodes = componentsCache.get(address);
            if (nodes != null) {
                removed = nodes.remove(nodeID);
                if (nodes.isEmpty()) {
                    componentsCache.remove(address);
                }
                else {
                    componentsCache.put(address, nodes);
                }
            }
        } finally {
            lock.unlock();
        }
        localRoutingTable.removeRoute(new DomainPair("", address));
        return removed;
    }

    @Override
    public void setRemotePacketRouter(RemotePacketRouter remotePacketRouter) {
        this.remotePacketRouter = remotePacketRouter;
    }

    @Override
    public RemotePacketRouter getRemotePacketRouter() {
        return remotePacketRouter;
    }

    @Override
    public void initialize(XMPPServer server) {
        super.initialize(server);
        this.server = server;
        serverName = server.getServerInfo().getXMPPDomain();
        iqRouter = server.getIQRouter();
        messageRouter = server.getMessageRouter();
        presenceRouter = server.getPresenceRouter();
        presenceUpdateHandler = server.getPresenceUpdateHandler();
        // Listen to cluster events
        ClusterManager.addListener(this);
    }

    @Override
    public void start() throws IllegalStateException {
        super.start();
        localRoutingTable.start();
    }

    @Override
    public void stop() {
        super.stop();
        localRoutingTable.stop();

        try
        {
            // Purge our own components from the cache for the benefit of other cluster nodes.
            CacheUtil.removeValueFromMultiValuedCache( componentsCache, XMPPServer.getInstance().getNodeID() );
        }
        catch ( Exception e )
        {
            Log.warn( "An exception occurred while trying to remove locally connected external components from the clustered cache. Other cluster nodes might continue to see our external components, even though we this instance is stopping.", e );
        }
    }

    @Override
    public void joinedCluster()
    {
        // Upon joining a cluster, the server can get a new ID. Here, all old IDs are replaced with the new identity.
        final NodeID defaultNodeID = server.getDefaultNodeID();
        final NodeID nodeID = server.getNodeID();
        if ( !defaultNodeID.equals( nodeID ) ) // In more recent versions of Openfire, the ID does not change.
        {
            CacheUtil.replaceValueInCache( serversCache, defaultNodeID, nodeID );
            CacheUtil.replaceValueInMultivaluedCache( componentsCache, defaultNodeID, nodeID );
            CacheUtil.replaceValueInCacheByMapping( usersCache,
                                                    clientRoute -> { if ( clientRoute.getNodeID().equals( defaultNodeID ) ) { clientRoute.setNodeID( nodeID ); } return clientRoute; } );
            CacheUtil.replaceValueInCacheByMapping( anonymousUsersCache,
                                                    clientRoute -> { if ( clientRoute.getNodeID().equals( defaultNodeID ) ) { clientRoute.setNodeID( nodeID ); } return clientRoute; } );
        }
        // Broadcast presence of local sessions to remote sessions when subscribed to presence
        // Probe presences of remote sessions when subscribed to presence of local session
        // Send pending subscription requests to local sessions from remote sessions
        // Deliver offline messages sent to local sessions that were unavailable in other nodes
        // Send available presences of local sessions to other resources of the same user
        PresenceUpdateHandler presenceUpdateHandler = XMPPServer.getInstance().getPresenceUpdateHandler();
        for (LocalClientSession session : localRoutingTable.getClientRoutes()) {
            // Simulate that the local session has just became available
            session.setInitialized(false);
            // Simulate that current session presence has just been received
            presenceUpdateHandler.process(session.getPresence());
        }
    }

    @Override
    public void joinedCluster(byte[] nodeID) {
        // Do nothing
    }

    @Override
    public void leftCluster() {
        if (!XMPPServer.getInstance().isShuttingDown()) {
            // Upon leaving a cluster, the server uses its non-clustered/default ID again. Here, all clustered IDs are replaced with the new identity.
            final NodeID defaultNodeID = server.getDefaultNodeID();
            final NodeID nodeID = server.getNodeID();
            if ( !defaultNodeID.equals( nodeID ) ) // In more recent versions of Openfire, the ID does not change.
            {
                CacheUtil.replaceValueInCache( serversCache, nodeID, defaultNodeID );
                CacheUtil.replaceValueInMultivaluedCache( componentsCache, nodeID, defaultNodeID );
                CacheUtil.replaceValueInCacheByMapping( usersCache,
                                                        clientRoute -> { if ( clientRoute.getNodeID().equals( nodeID ) ) { clientRoute.setNodeID( defaultNodeID ); } return clientRoute; } );
                CacheUtil.replaceValueInCacheByMapping( anonymousUsersCache,
                                                        clientRoute -> { if ( clientRoute.getNodeID().equals( nodeID ) ) { clientRoute.setNodeID( defaultNodeID ); } return clientRoute; } );
            }
            // The local cluster node left the cluster.
            //
            // Determine what routes were available only on other cluster nodes than the local one.
            // These need to be cleaned up, as they're no longer available to the local cluster node.

            // Drop outgoing server routes from all other nodes.
            final Set<DomainPair> removedOutgoingServerSessions = CacheUtil.retainValueInCache( serversCache, defaultNodeID );
            removedOutgoingServerSessions.forEach( removedOutgoingServerSession -> {
                Log.debug( "The local cluster node left the cluster. The outoing server session for '{}' was living on another cluster nodes, and is no longer available.", removedOutgoingServerSession.getRemote() );
                localRoutingTable.removeRoute( removedOutgoingServerSession );
            } );

            // Drop component routes from all other nodes.
            final Map<Boolean, Map<String, HashSet<NodeID>>> modified = CacheUtil.retainValueInMultiValuedCache( componentsCache, defaultNodeID );
            modified.get( false ).keySet().forEach( removedComponentDomain -> {
                Log.debug( "The local cluster node left the cluster. The component session for '{}' was living on one (or more) other cluster nodes, and is no longer available.", removedComponentDomain );
                localRoutingTable.removeRoute(new DomainPair("", removedComponentDomain ));
            } );

            // Drop routes for all client sessions connected via other cluster nodes.
            final List<String> remoteClientRoutes = new ArrayList<>();
            for (Map.Entry<String, ClientRoute> entry : usersCache.entrySet()) {
                if (!entry.getValue().getNodeID().equals(defaultNodeID)) {
                    remoteClientRoutes.add(entry.getKey());
                }
            }
            for (Map.Entry<String, ClientRoute> entry : anonymousUsersCache.entrySet()) {
                if (!entry.getValue().getNodeID().equals(defaultNodeID)) {
                    remoteClientRoutes.add(entry.getKey());
                }
            }
            Log.debug( "The local cluster node left the cluster. A total of {} client sessions were living on one (or more) other cluster nodes, and are no longer available.", remoteClientRoutes.size() );
            for (String route : remoteClientRoutes) {
                // This call takes responsibility for cleaning up the state in RoutingTableImpl as well as SessionManager.
                // The detour is needed, as SessionManager does not keep track what client is associated to what cluster node.
                SessionManager.getInstance().removeRemoteClientSession( new JID(route) );
            }
        }
    }

    @Override
    public void leftCluster(byte[] nodeID) {
        
        // When a peer server leaves the cluster, any remote routes that were
        // associated with the defunct node must be dropped from the routing 
        // caches that are shared by the remaining cluster member(s).
        
        // drop routes for all client sessions connected via the defunct cluster node
            List<String> remoteClientRoutes = new ArrayList<>();
            for (Map.Entry<String, ClientRoute> entry : usersCache.entrySet()) {
                if (entry.getValue().getNodeID().equals(nodeID)) {
                    remoteClientRoutes.add(entry.getKey());
                }
            }
            for (Map.Entry<String, ClientRoute> entry : anonymousUsersCache.entrySet()) {
                if (entry.getValue().getNodeID().equals(nodeID)) {
                    remoteClientRoutes.add(entry.getKey());
                }
            }
            Log.debug( "Cluster node {} just left the cluster. A total of {} client sessions was living there, and are no longer available.", NodeID.getInstance( nodeID ), remoteClientRoutes.size() );
            for (String route : remoteClientRoutes) {
                // This call takes responsibility for cleaning up the state in RoutingTableImpl as well as SessionManager.
                // The detour is needed, as SessionManager does not keep track what client is associated to what cluster node.
                SessionManager.getInstance().removeRemoteClientSession( new JID(route) );
            }

        // remove routes for server domains that were accessed through the defunct node
        final Set<DomainPair> removedServers = CacheUtil.removeValueFromCache( serversCache, NodeID.getInstance( nodeID ) );
        removedServers.forEach( removedServer -> {
            Log.debug( "Cluster node {} just left the cluster, and was the only node on which the outgoing server route to '{}' was living. This route will be removed.", NodeID.getInstance( nodeID ), removedServer.getRemote() );
            localRoutingTable.removeRoute( removedServer );
        } );

        // remove component routes for the defunct node
        final Map<Boolean, Map<String, HashSet<NodeID>>> modifiedComponents = CacheUtil.removeValueFromMultiValuedCache( componentsCache, NodeID.getInstance( nodeID ) );
        modifiedComponents.get( false ).keySet().forEach( removedComponentDomain -> {
            Log.debug( "Cluster node {} just left the cluster, and was the only node on which the external component session for '{}' was living. This route will be removed", NodeID.getInstance( nodeID ), removedComponentDomain );
            localRoutingTable.removeRoute(new DomainPair("", removedComponentDomain ));
        } );
    }

    @Override
    public void markedAsSeniorClusterMember() {
        // Do nothing
    }
}