/**
 * $RCSfile: PresenceSubscribeHandler.java,v $
 * $Revision: 3136 $
 * $Date: 2005-12-01 02:06:16 -0300 (Thu, 01 Dec 2005) $
 *
 * Copyright (C) 2004 Jive Software. All rights reserved.
 *
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution.
 */

package org.jivesoftware.wildfire.handler;

import org.jivesoftware.util.CacheManager;
import org.jivesoftware.util.LocaleUtils;
import org.jivesoftware.util.Log;
import org.jivesoftware.wildfire.*;
import org.jivesoftware.wildfire.container.BasicModule;
import org.jivesoftware.wildfire.roster.Roster;
import org.jivesoftware.wildfire.roster.RosterItem;
import org.jivesoftware.wildfire.user.UserAlreadyExistsException;
import org.jivesoftware.wildfire.user.UserManager;
import org.jivesoftware.wildfire.user.UserNotFoundException;
import org.xmpp.packet.JID;
import org.xmpp.packet.Packet;
import org.xmpp.packet.PacketError;
import org.xmpp.packet.Presence;

import java.util.Hashtable;
import java.util.Map;

/**
 * Implements the presence protocol. Clients use this protocol to
 * update presence and roster information.
 * <p/>
 * The handler must properly detect the presence type, update the user's roster,
 * and inform presence subscribers of the session's updated presence
 * status. Presence serves many purposes in Jabber so this handler will
 * likely be the most complex of all handlers in the server.
 * <p/>
 * There are four basic types of presence updates:
 * <ul>
 * <li>Simple presence updates - addressed to the server (or to address), these updates
 * are properly addressed by the server, and multicast to
 * interested subscribers on the user's roster. An empty, missing,
 * or "unavailable" type attribute indicates a simple update (there
 * is no "available" type although it should be accepted by the server.
 * <li>Directed presence updates - addressed to particular jabber entities,
 * these presence updates are properly addressed and directly delivered
 * to the entity without broadcast to roster subscribers. Any update type
 * is possible except those reserved for subscription requests.
 * <li>Subscription requests - these updates request presence subscription
 * status changes. Such requests always affect the roster.  The server must:
 * <ul>
 * <li>update the roster with the proper subscriber info
 * <li>push the roster changes to the user
 * <li>forward the update to the correct parties.
 * </ul>
 * The valid types include "subscribe", "subscribed", "unsubscribed",
 * and "unsubscribe".
 * <li>XMPPServer probes - Provides a mechanism for servers to query the presence
 * status of users on another server. This allows users to immediately
 * know the presence status of users when they come online rather than way
 * for a presence update broadcast from the other server or tracking them
 * as they are received.  Requires S2S capabilities.
 * </ul>
 * <p/>
 * <h2>Warning</h2>
 * There should be a way of determining whether a session has
 * authorization to access this feature. I'm not sure it is a good
 * idea to do authorization in each handler. It would be nice if
 * the framework could assert authorization policies across channels.
 *
 * @author Iain Shigeoka
 */
public class PresenceSubscribeHandler extends BasicModule implements ChannelHandler {

    private RoutingTable routingTable;
    private XMPPServer localServer;
    private PacketDeliverer deliverer;
    private PresenceManager presenceManager;
    private UserManager userManager;

    public PresenceSubscribeHandler() {
        super("Presence subscription handler");
    }

    public void process(Packet xmppPacket) throws PacketException {
        Presence presence = (Presence)xmppPacket;
        try {
            JID senderJID = presence.getFrom();
            JID recipientJID = presence.getTo();
            Presence.Type type = presence.getType();
            try {
                Roster senderRoster = getRoster(senderJID);
                boolean senderSubChanged = false;
                if (senderRoster != null) {
                    senderSubChanged = manageSub(recipientJID, true, type, senderRoster);
                }
                Roster recipientRoster = getRoster(recipientJID);
                boolean recipientSubChanged = false;
                if (recipientRoster != null) {
                    recipientSubChanged = manageSub(senderJID, false, type, recipientRoster);
                }

                // Do not forward the packet to the recipient if the presence is of type subscribed
                // and the recipient user has not changed its subscription state.
                if (!(type == Presence.Type.subscribed && recipientRoster != null &&
                        !recipientSubChanged)) {

                    // If the user is already subscribed to the *local* user's presence then do not 
                    // forward the subscription request and instead send an auto-reply on behalf
                    // of the user
                    if (type == Presence.Type.subscribe && recipientRoster != null &&
                        !recipientSubChanged) {
                        try {
                            RosterItem.SubType subType = recipientRoster.getRosterItem(senderJID)
                                    .getSubStatus();
                            if (subType == RosterItem.SUB_FROM || subType == RosterItem.SUB_BOTH) {
                                // auto-reply by sending a presence stanza of type "subscribed"
                                // to the contact on behalf of the user
                                Presence reply = new Presence();
                                reply.setTo(senderJID);
                                reply.setFrom(recipientJID);
                                reply.setType(Presence.Type.subscribed);
                                deliverer.deliver(reply);
                                return;
                            }
                        }
                        catch (UserNotFoundException e) {
                            // Weird case: Roster item does not exist. Should never happen
                        }
                    }

                    // Try to obtain a handler for the packet based on the routes. If the handler is
                    // a module, the module will be able to handle the packet. If the handler is a
                    // Session the packet will be routed to the client. If a route cannot be found
                    // then the packet will be delivered based on its recipient and sender.
                    ChannelHandler handler = routingTable.getRoute(recipientJID);
                    if (handler != null) {
                        Presence presenteToSend = presence.createCopy();
                        // Stamp the presence with the user's bare JID as the 'from' address
                        presenteToSend.setFrom(senderJID.toBareJID());
                        handler.process(presenteToSend);
                    }
                    else {
                        deliverer.deliver(presence.createCopy());
                    }

                    if (type == Presence.Type.subscribed) {
                        // Send the presence of the local user to the remote user. The remote user
                        // subscribed to the presence of the local user and the local user accepted
                        presenceManager.probePresence(recipientJID, senderJID);
                    }
                }

                if (type == Presence.Type.unsubscribed) {
                    // Send unavailable presence from all of the local user's available resources
                    // to the remote user
                    presenceManager.sendUnavailableFromSessions(recipientJID, senderJID);
                }
            }
            catch (SharedGroupException e) {
                Presence result = presence.createCopy();
                JID sender = result.getFrom();
                result.setFrom(presence.getTo());
                result.setTo(sender);
                result.setError(PacketError.Condition.not_acceptable);
                deliverer.deliver(result);
            }
        }
        catch (Exception e) {
            Log.error(LocaleUtils.getLocalizedString("admin.error"), e);
        }
    }

    /**
     * <p>Obtain the roster for the given address or null if the address doesn't have a roster.</p>
     *
     * @param address The address to check
     * @return The roster or null if the address is not managed on the server
     */
    private Roster getRoster(JID address) {
        String username = null;
        Roster roster = null;
        if (localServer.isLocal(address) && userManager.isRegisteredUser(address.getNode())) {
            username = address.getNode();
            // Check for a cached roster:
            roster = (Roster)CacheManager.getCache("username2roster").get(username);
            if (roster == null) {
                synchronized(address.toString().intern()) {
                    roster = (Roster)CacheManager.getCache("username2roster").get(username);
                    if (roster == null) {
                        // Not in cache so load a new one:
                        roster = new Roster(username);
                        CacheManager.getCache("username2roster").put(username, roster);
                    }
                }
            }
        }
        return roster;
    }

    /**
     * Manage the subscription request. This method retrieves a user's roster
     * and updates it's state, storing any changes made, and updating the roster
     * owner if changes occured.
     *
     * @param target    The roster target's jid (the item's jid to be changed)
     * @param isSending True if the request is being sent by the owner
     * @param type      The subscription change type (subscribe, unsubscribe, etc.)
     * @return true if the subscription state has changed.
     */
    private boolean manageSub(JID target, boolean isSending, Presence.Type type, Roster roster)
            throws UserAlreadyExistsException, SharedGroupException
    {
        RosterItem item = null;
        RosterItem.AskType oldAsk = null;
        RosterItem.SubType oldSub = null;
        RosterItem.RecvType oldRecv = null;
        try {
            if (roster.isRosterItem(target)) {
                item = roster.getRosterItem(target);
            }
            else {
                if (Presence.Type.unsubscribed == type || Presence.Type.unsubscribe == type) {
                    // Do not create a roster item when processing a confirmation of
                    // an unsubscription or receiving an unsubscription request from
                    // an unknown user
                    return false;
                }
                item = roster.createRosterItem(target);
            }
            // Get a snapshot of the item state
            oldAsk = item.getAskStatus();
            oldSub = item.getSubStatus();
            oldRecv = item.getRecvStatus();
            // Update the item state based in the received presence type
            updateState(item, type, isSending);
            // Update the roster IF the item state has changed
            if (oldAsk != item.getAskStatus() || oldSub != item.getSubStatus() ||
                    oldRecv != item.getRecvStatus()) {
                roster.updateRosterItem(item);
            }
        }
        catch (UserNotFoundException e) {
            // Should be there because we just checked that it's an item
            Log.error(LocaleUtils.getLocalizedString("admin.error"), e);
        }
        return oldSub != item.getSubStatus();
    }

    /**
     * <p>The transition state table.</p>
     * <p>The root 'old state' transition table is a Map of RosterItem.SubType keys to match
     * to the old state of the item. Each key returns a Map containing the next
     * transition table. Transitions are defined as:</p>
     * <ul>
     * <li>'send/receive' table: Lookup whether this updates was sent or received: obtain 'action' table - key: Presence.Type subcribe action, value: Map (transition table).</li>
     * <li>'new state' table: the changed item values</li>
     * </ul>
     */
    private static Hashtable stateTable = new Hashtable();

    static {
        Hashtable subrTable;
        Hashtable subsTable;
        Hashtable sr;

        sr = new Hashtable();
        subrTable = new Hashtable();
        subsTable = new Hashtable();
        sr.put("recv", subrTable);
        sr.put("send", subsTable);
        stateTable.put(RosterItem.SUB_NONE, sr);
        // Item wishes to subscribe from owner
        // Set flag and update roster if this is a new state, this is the normal way to begin
        // a roster subscription negotiation.
        subrTable.put(Presence.Type.subscribe, new Change(RosterItem.RECV_SUBSCRIBE, null, null)); // no transition
        // Item granted subscription to owner
        // The item's state immediately goes from NONE to TO and ask is reset
        subrTable.put(Presence.Type.subscribed, new Change(null, RosterItem.SUB_TO, RosterItem.ASK_NONE));
        // Item wishes to unsubscribe from owner
        // This makes no sense, there is no subscription to remove
        subrTable.put(Presence.Type.unsubscribe, new Change(null, null, null));
        // Owner has subscription to item revoked
        // Valid response if item requested subscription and we're denying request
        subrTable.put(Presence.Type.unsubscribed, new Change(null, null, RosterItem.ASK_NONE));
        // Owner asking to subscribe to item this is the normal way to begin
        // a roster subscription negotiation.
        subsTable.put(Presence.Type.subscribe, new Change(null, null, RosterItem.ASK_SUBSCRIBE));
        // Item granted a subscription from owner
        subsTable.put(Presence.Type.subscribed, new Change(RosterItem.RECV_NONE, RosterItem.SUB_FROM, null));
        // Owner asking to unsubscribe to item
        // This makes no sense (there is no subscription to unsubscribe from)
        subsTable.put(Presence.Type.unsubscribe, new Change(null, null, null));
        // Item has subscription from owner revoked
        // Valid response if item requested subscription and we're denying request
        subsTable.put(Presence.Type.unsubscribed, new Change(RosterItem.RECV_NONE, null, null));

        sr = new Hashtable();
        subrTable = new Hashtable();
        subsTable = new Hashtable();
        sr.put("recv", subrTable);
        sr.put("send", subsTable);
        stateTable.put(RosterItem.SUB_FROM, sr);
        // Owner asking to subscribe to item
        // Set flag and update roster if this is a new state, this is the normal way to begin
        // a mutual roster subscription negotiation.
        subsTable.put(Presence.Type.subscribe, new Change(null, null, RosterItem.ASK_SUBSCRIBE));
        // Item granted a subscription from owner
        // This may be necessary if the recipient didn't get an earlier subscribed grant
        // or as a denial of an unsubscribe request
        subsTable.put(Presence.Type.subscribed, new Change(RosterItem.RECV_NONE, null, null));
        // Owner asking to unsubscribe to item
        // This makes no sense (there is no subscription to unsubscribe from)
        subsTable.put(Presence.Type.unsubscribe, new Change(null, RosterItem.SUB_NONE, null));
        // Item has subscription from owner revoked
        // Immediately transition to NONE state
        subsTable.put(Presence.Type.unsubscribed, new Change(RosterItem.RECV_NONE, RosterItem.SUB_NONE, null));
        // Item wishes to subscribe from owner
        // Item already has a subscription so only interesting if item had requested unsubscribe
        // Set flag and update roster if this is a new state, this is the normal way to begin
        // a mutual roster subscription negotiation.
        subrTable.put(Presence.Type.subscribe, new Change(RosterItem.RECV_NONE, null, null));
        // Item granted subscription to owner
        // The item's state immediately goes from FROM to BOTH and ask is reset
        subrTable.put(Presence.Type.subscribed, new Change(null, RosterItem.SUB_BOTH, RosterItem.ASK_NONE));
        // Item wishes to unsubscribe from owner
        // This is the normal mechanism of removing subscription
        subrTable.put(Presence.Type.unsubscribe, new Change(RosterItem.RECV_UNSUBSCRIBE, RosterItem.SUB_NONE, null));
        // Owner has subscription to item revoked
        // Valid response if owner requested subscription and item is denying request
        subrTable.put(Presence.Type.unsubscribed, new Change(null, null, RosterItem.ASK_NONE));

        sr = new Hashtable();
        subrTable = new Hashtable();
        subsTable = new Hashtable();
        sr.put("recv", subrTable);
        sr.put("send", subsTable);
        stateTable.put(RosterItem.SUB_TO, sr);
        // Owner asking to subscribe to item
        // We're already subscribed, may be trying to unset a unsub request
        subsTable.put(Presence.Type.subscribe, new Change(null, null, RosterItem.ASK_NONE));
        // Item granted a subscription from owner
        // Sets mutual subscription
        subsTable.put(Presence.Type.subscribed, new Change(RosterItem.RECV_NONE, RosterItem.SUB_BOTH, null));
        // Owner asking to unsubscribe to item
        // Normal method of removing subscription
        subsTable.put(Presence.Type.unsubscribe, new Change(null, RosterItem.SUB_NONE, RosterItem.ASK_UNSUBSCRIBE));
        // Item has subscription from owner revoked
        // No subscription to unsub, makes sense if denying subscription request or for
        // situations where the original unsubscribed got lost
        subsTable.put(Presence.Type.unsubscribed, new Change(RosterItem.RECV_NONE, null, null));
        // Item wishes to subscribe from owner
        // This is the normal way to negotiate a mutual subscription
        subrTable.put(Presence.Type.subscribe, new Change(RosterItem.RECV_SUBSCRIBE, null, null));
        // Item granted subscription to owner
        // Owner already subscribed to item, could be a unsub denial or a lost packet
        subrTable.put(Presence.Type.subscribed, new Change(null, null, RosterItem.ASK_NONE));
        // Item wishes to unsubscribe from owner
        // There is no subscription. May be trying to cancel earlier subscribe request.
        subrTable.put(Presence.Type.unsubscribe, new Change(RosterItem.RECV_NONE, RosterItem.SUB_NONE, null));
        // Owner has subscription to item revoked
        // Setting subscription to none
        subrTable.put(Presence.Type.unsubscribed, new Change(null, RosterItem.SUB_NONE, RosterItem.ASK_NONE));

        sr = new Hashtable();
        subrTable = new Hashtable();
        subsTable = new Hashtable();
        sr.put("recv", subrTable);
        sr.put("send", subsTable);
        stateTable.put(RosterItem.SUB_BOTH, sr);
        // Owner asking to subscribe to item
        // Makes sense if trying to cancel previous unsub request
        subsTable.put(Presence.Type.subscribe, new Change(null, null, RosterItem.ASK_NONE));
        // Item granted a subscription from owner
        // This may be necessary if the recipient didn't get an earlier subscribed grant
        // or as a denial of an unsubscribe request
        subsTable.put(Presence.Type.subscribed, new Change(RosterItem.RECV_NONE, null, null));
        // Owner asking to unsubscribe to item
        // Set flags
        subsTable.put(Presence.Type.unsubscribe, new Change(null, RosterItem.SUB_FROM, RosterItem.ASK_UNSUBSCRIBE));
        // Item has subscription from owner revoked
        // Immediately transition them to TO state
        subsTable.put(Presence.Type.unsubscribed, new Change(RosterItem.RECV_NONE, RosterItem.SUB_TO, null));
        // Item wishes to subscribe to owner
        // Item already has a subscription so only interesting if item had requested unsubscribe
        // Set flag and update roster if this is a new state, this is the normal way to begin
        // a mutual roster subscription negotiation.
        subrTable.put(Presence.Type.subscribe, new Change(RosterItem.RECV_NONE, null, null));
        // Item granted subscription to owner
        // Redundant unless denying unsub request
        subrTable.put(Presence.Type.subscribed, new Change(null, null, RosterItem.ASK_NONE));
        // Item wishes to unsubscribe from owner
        // This is the normal mechanism of removing subscription
        subrTable.put(Presence.Type.unsubscribe, new Change(RosterItem.RECV_UNSUBSCRIBE, RosterItem.SUB_TO, null));
        // Owner has subscription to item revoked
        // Immediately downgrade state to FROM
        subrTable.put(Presence.Type.unsubscribed, new Change(RosterItem.RECV_NONE, RosterItem.SUB_FROM, RosterItem.ASK_NONE));
    }

    /**
     * <p>Indicate a state change.</p>
     * <p>Use nulls to indicate fields that should not be changed.</p>
     */
    private static class Change {
        public Change(RosterItem.RecvType recv, RosterItem.SubType sub, RosterItem.AskType ask) {
            newRecv = recv;
            newSub = sub;
            newAsk = ask;
        }

        public RosterItem.RecvType newRecv;
        public RosterItem.SubType newSub;
        public RosterItem.AskType newAsk;
    }

    /**
     * Determine and call the update method based on the item's subscription state.
     * The method also turns the action and sending status into an integer code
     * for easier processing (switch statements).
     * <p/>
     * Code relies on states being in numerical order without skipping.
     * In addition, the receive states must parallel the send states
     * so that (send state X) + STATE_RECV_SUBSCRIBE == (receive state X)
     * where X is subscribe, subscribed, etc.
     * </p>
     *
     * @param item      The item to be updated
     * @param action    The new state change request
     * @param isSending True if the roster owner of the item is sending the new state change request
     */
    private static void updateState(RosterItem item, Presence.Type action, boolean isSending) {
        Map srTable = (Map)stateTable.get(item.getSubStatus());
        Map changeTable = (Map)srTable.get(isSending ? "send" : "recv");
        Change change = (Change)changeTable.get(action);
        boolean modified = false;
        if (change.newAsk != null && change.newAsk != item.getAskStatus()) {
            item.setAskStatus(change.newAsk);
        }
        if (change.newSub != null && change.newSub != item.getSubStatus()) {
            item.setSubStatus(change.newSub);
            modified = true;
        }
        if (change.newRecv != null && change.newRecv != item.getRecvStatus()) {
            item.setRecvStatus(change.newRecv);
        }
    }

    public void initialize(XMPPServer server) {
        super.initialize(server);
        localServer = server;
        routingTable = server.getRoutingTable();
        deliverer = server.getPacketDeliverer();
        presenceManager = server.getPresenceManager();
        userManager = server.getUserManager();
    }
}