package org.jivesoftware.openfire.streammanagement;

import java.math.BigInteger;
import java.net.UnknownHostException;
import java.nio.charset.StandardCharsets;
import java.util.*;

import org.dom4j.Element;
import org.dom4j.QName;
import org.dom4j.dom.DOMElement;
import org.jivesoftware.openfire.Connection;
import org.jivesoftware.openfire.PacketRouter;
import org.jivesoftware.openfire.XMPPServer;
import org.jivesoftware.openfire.auth.AuthToken;
import org.jivesoftware.openfire.auth.UnauthorizedException;
import org.jivesoftware.openfire.session.ClientSession;
import org.jivesoftware.openfire.session.LocalClientSession;
import org.jivesoftware.openfire.session.LocalSession;
import org.jivesoftware.openfire.session.Session;
import org.jivesoftware.util.JiveGlobals;
import org.jivesoftware.util.StringUtils;
import org.jivesoftware.util.XMPPDateTimeFormat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xmpp.packet.*;

/**
 * XEP-0198 Stream Manager.
 * Handles client/server messages acknowledgement.
 *
 * @author jonnyheavey
 */
public class StreamManager {

	private final Logger Log;
	private boolean resume = false;
    public static class UnackedPacket {
		public final long x;
        public final Date timestamp = new Date();
        public final Packet packet;
        
        public UnackedPacket(long x, Packet p) {
			this.x = x;
            packet = p;
        }
    }
    
    public static final String SM_ACTIVE = "stream.management.active";

    /**
     * Stanza namespaces
     */
    public static final String NAMESPACE_V2 = "urn:xmpp:sm:2";
    public static final String NAMESPACE_V3 = "urn:xmpp:sm:3";

    /**
     * Session (stream) to client.
     */
    private final LocalSession session;

	/**
     * Namespace to be used in stanzas sent to client (depending on XEP-0198 version used by client)
     */
    private String namespace;

    /**
     * Count of how many stanzas/packets
     * sent from the client that the server has processed
     */
    private long serverProcessedStanzas = 0;

    /**
 	 * Count of how many stanzas/packets
     * sent from the server that the client has processed
     */
    private long clientProcessedStanzas = 0;

    static private long mask = new BigInteger("2").pow(32).longValue() - 1; // This is used to emulate rollover.

    /**
     * Collection of stanzas/packets sent to client that haven't been acknowledged.
     */
    private Deque<UnackedPacket> unacknowledgedServerStanzas = new LinkedList<>();

    public StreamManager(LocalSession session) {
		String address;
		try {
			address = session.getConnection().getHostAddress();
		}
		catch ( UnknownHostException e )
		{
			address = null;
		}

		this.Log = LoggerFactory.getLogger(StreamManager.class + "["+ (address == null ? "(unknown address)" : address) +"]" );
    	this.session = session;
    }

    /**
     * Returns true if a stream is resumable.
     *
     * @return True if a stream is resumable.
     */
    public boolean getResume() {
        return resume;
    }

    /**
	 * Processes a stream management element.
	 *
	 * @param element The stream management element to be processed.
	 */
	public void process( Element element )
	{
		switch(element.getName()) {
			case "enable":
			    String resumeString = element.attributeValue("resume");
			    boolean resume = false;
			    if (resumeString != null) {
			        if (resumeString.equalsIgnoreCase("true") || resumeString.equalsIgnoreCase("yes") || resumeString.equals("1")) {
			            resume = true;
                    }
                }
				enable( element.getNamespace().getStringValue(), resume );
				break;
            case "resume":
                long h = new Long(element.attributeValue("h"));
                String previd = element.attributeValue("previd");
                startResume( element.getNamespaceURI(), previd, h);
                break;
			case "r":
				sendServerAcknowledgement();
				break;
			case "a":
				processClientAcknowledgement( element);
				break;
			default:
				sendUnexpectedError();
		}
	}

    /**
     * Should this session be allowed to resume?
     * This is used while processed <enable/> and <resume/>
     *
     * @return True if the session is allowed to resume.
     */
	private boolean allowResume() {
        boolean allow = false;
        // Ensure that resource binding has occurred.
        if (session instanceof ClientSession) {
            AuthToken authToken = ((LocalClientSession)session).getAuthToken();
            if (authToken != null) {
                if (!authToken.isAnonymous()) {
                    allow = true;
                }
            }
        }
        return allow;
    }

	/**
	 * Attempts to enable Stream Management for the entity identified by the provided JID.
	 *
	 * @param namespace The namespace that defines what version of SM is to be enabled.
     * @param resume Whether the client is requesting a resumable session.
	 */
	private void enable( String namespace, boolean resume )
	{


	    boolean offerResume = allowResume();
		// Ensure that resource binding has occurred.
        if (session.getStatus() != Session.STATUS_AUTHENTICATED) {
            this.namespace = namespace;
            sendUnexpectedError();
            return;
        }

		String smId = null;

		synchronized ( this )
		{
			// Do nothing if already enabled
			if ( isEnabled() )
			{
				sendUnexpectedError();
				return;
			}
			this.namespace = namespace;

			this.resume = resume && offerResume;
			if ( this.resume ) {
			    // Create SM-ID.
                smId = StringUtils.encodeBase64( session.getAddress().getResource() + "\0" + session.getStreamID().getID());
            }
		}

		// Send confirmation to the requestee.
        Element enabled = new DOMElement(QName.get("enabled", namespace));
		if (this.resume) {
            enabled.addAttribute("resume", "true");
            enabled.addAttribute( "id", smId);
        }
		session.deliverRawText(enabled.asXML());
	}

	private void startResume(String namespace, String previd, long h) {
        this.namespace = namespace;
        // Ensure that resource binding has NOT occurred.
        if (!allowResume() ) {
            sendUnexpectedError();
            return;
        }
        if (session.getStatus() == Session.STATUS_AUTHENTICATED) {
            sendUnexpectedError();
            return;
        }
        AuthToken authToken = null;
        // Ensure that resource binding has occurred.
        if (session instanceof ClientSession) {
            authToken = ((LocalClientSession) session).getAuthToken();
        }
        if (authToken == null) {
            sendUnexpectedError();
            return;
        }
        // Decode previd.
        String resource;
        String streamId;
        try {
            StringTokenizer toks = new StringTokenizer(new String(StringUtils.decodeBase64(previd), StandardCharsets.UTF_8), "\0");
            resource = toks.nextToken();
            streamId = toks.nextToken();
        } catch (Exception e) {
            Log.debug("Exception from previd decode:", e);
            sendUnexpectedError();
            return;
        }
        JID fullJid = new JID(authToken.getUsername(), authToken.getDomain(), resource, true);

        // Locate existing session.
        LocalClientSession otherSession = (LocalClientSession)XMPPServer.getInstance().getRoutingTable().getClientRoute(fullJid);
        if (otherSession == null) {
            sendError(new PacketError(PacketError.Condition.item_not_found));
            return;
        }
        if (!otherSession.getStreamID().getID().equals(streamId)) {
            sendError(new PacketError(PacketError.Condition.item_not_found));
            return;
        }
        // Previd identifies proper session. Now check SM status
        if (!otherSession.getStreamManager().namespace.equals(namespace)) {
            sendError(new PacketError(PacketError.Condition.unexpected_request));
            return;
        }
        if (!otherSession.getStreamManager().resume) {
            sendError(new PacketError(PacketError.Condition.unexpected_request));
            return;
        }
        if (!otherSession.isDetached()) {
            otherSession.setDetached();
        }
        // If we're all happy, disconnect this session.
        Connection conn = session.getConnection();
        session.setDetached();
        // Connect new session.
        otherSession.reattach(conn, h);
        // Perform resumption on new session.
        session.close();
    }

    /**
     * Called when a session receives a closing stream tag, this prevents the
     * session from being detached.
     */
    public void formalClose() {
	    this.resume = false;
    }

	/**
     * Sends XEP-0198 acknowledgement &lt;a /&gt; to client from server
     */
	public void sendServerAcknowledgement() {
		if(isEnabled()) {
			String ack = String.format("<a xmlns='%s' h='%s' />", namespace, serverProcessedStanzas & mask);
			session.deliverRawText( ack );
		}
	}

	/**
	 * Sends XEP-0198 request <r /> to client from server
	 */
	private void sendServerRequest() {
		if(isEnabled()) {
		    if (session.isDetached()) {
		        Log.debug("Session is detached, won't request an ack.");
		        return;
            }
			String request = String.format("<r xmlns='%s' />", namespace);
			session.deliverRawText( request );
		}
	}

	/**
	 * Send an error if a XEP-0198 stanza is received at an unexpected time.
	 * e.g. before resource-binding has completed.
	 */
	private void sendUnexpectedError() {
	    sendError(new PacketError( PacketError.Condition.unexpected_request ));
	}

    /**
     * Send a generic failed error.
     *
     * @param error PacketError describing the failure.
     */
    private void sendError(PacketError error) {
        session.deliverRawText(
            String.format("<failed xmlns='%s'>", namespace)
                + String.format("<%s xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>", error.getCondition().toXMPP())
                + "</failed>"
        );
        this.namespace = null; // isEnabled() is testing this.
    }

    /**
     * Process client acknowledgements for a given value of h.
     *
     * @param h Last handled stanza to be acknowledged.
     */
	private void processClientAcknowledgement(long h) {
        synchronized (this) {

            if ( !unacknowledgedServerStanzas.isEmpty() && h > unacknowledgedServerStanzas.getLast().x ) {
                Log.warn( "Client acknowledges stanzas that we didn't send! Client Ack h: {}, our last stanza: {}", h, unacknowledgedServerStanzas.getLast().x );
            }

            clientProcessedStanzas = h;

            // Remove stanzas from temporary storage as now acknowledged
            Log.trace( "Before processing client Ack (h={}): {} unacknowledged stanzas.", h, unacknowledgedServerStanzas.size() );

            // Pop all acknowledged stanzas.
            while( !unacknowledgedServerStanzas.isEmpty() && unacknowledgedServerStanzas.getFirst().x <= h )
            {
                unacknowledgedServerStanzas.removeFirst();
            }

            // Ensure that unacknowledged stanzas are purged after the client rolled over 'h' which occurs at h= (2^32)-1
            final int maxUnacked = getMaximumUnacknowledgedStanzas();
            final boolean clientHadRollOver = h < maxUnacked && !unacknowledgedServerStanzas.isEmpty() && unacknowledgedServerStanzas.getLast().x > mask - maxUnacked;
            if ( clientHadRollOver )
            {
                Log.info( "Client rolled over 'h'. Purging high-numbered unacknowledged stanzas." );
                while ( !unacknowledgedServerStanzas.isEmpty() && unacknowledgedServerStanzas.getLast().x > mask - maxUnacked)
                {
                    unacknowledgedServerStanzas.removeLast();
                }
            }

            Log.trace( "After processing client Ack (h={}): {} unacknowledged stanzas.", h, unacknowledgedServerStanzas.size());
        }
    }

	/**
	 * Receive and process acknowledgement packet from client
	 * @param ack XEP-0198 acknowledgement <a /> stanza to process
	 */
	private void processClientAcknowledgement(Element ack) {
		if(isEnabled()) {
			if (ack.attribute("h") != null) {
				final long h = Long.valueOf(ack.attributeValue("h"));

				Log.debug( "Received acknowledgement from client: h={}", h );
				processClientAcknowledgement(h);
			}
		}
	}

	/**
	 * Registers that Openfire sends a stanza to the client (which is expected to be acknowledged later).
	 * @param packet The stanza that is sent.
	 */
	public void sentStanza(Packet packet) {

		if(isEnabled()) {
			final long requestFrequency = JiveGlobals.getLongProperty( "stream.management.requestFrequency", 5 );
			final int size;

			synchronized (this)
			{
				// The next ID is one higher than the last stanza that was sent (which might be unacknowledged!)
				final long x = 1 + ( unacknowledgedServerStanzas.isEmpty() ? clientProcessedStanzas : unacknowledgedServerStanzas.getLast().x );
				unacknowledgedServerStanzas.addLast( new StreamManager.UnackedPacket( x, packet.createCopy() ) );

				size = unacknowledgedServerStanzas.size();

				Log.trace( "Added stanza of type '{}' to collection of unacknowledged stanzas (x={}). Collection size is now {}.", packet.getElement().getName(), x, size );

				// Prevent keeping to many stanzas in memory.
				if ( size > getMaximumUnacknowledgedStanzas() )
				{
					Log.warn( "To many stanzas go unacknowledged for this connection. Clearing queue and disabling functionality." );
					namespace = null;
					unacknowledgedServerStanzas.clear();
					return;
				}
			}

			// When we have a sizable amount of unacknowledged stanzas, request acknowledgement.
			if ( size % requestFrequency == 0 ) {
				Log.debug( "Requesting acknowledgement from peer, as we have {} or more unacknowledged stanzas.", requestFrequency );
				sendServerRequest();
			}
		}

	}

	public void onClose(PacketRouter router, JID serverAddress) {
		// Re-deliver unacknowledged stanzas from broken stream (XEP-0198)
		synchronized (this) {
			if(isEnabled()) {
				namespace = null; // disable stream management.
				for (StreamManager.UnackedPacket unacked : unacknowledgedServerStanzas) {
					if (unacked.packet instanceof Message) {
						Message m = (Message) unacked.packet;
						if (m.getExtension("delay", "urn:xmpp:delay") == null) {
							Element delayInformation = m.addChildElement("delay", "urn:xmpp:delay");
							delayInformation.addAttribute("stamp", XMPPDateTimeFormat.format(unacked.timestamp));
							delayInformation.addAttribute("from", serverAddress.toBareJID());
						}
						router.route(unacked.packet);
					}
				}
			}
		}

	}

	public void onResume(JID serverAddress, long h) {
	    Log.debug("Agreeing to resume");
	    Element resumed = new DOMElement(QName.get("resumed", namespace));
	    resumed.addAttribute("previd", StringUtils.encodeBase64( session.getAddress().getResource() + "\0" + session.getStreamID().getID()));
	    resumed.addAttribute("h", Long.toString(clientProcessedStanzas));
	    session.getConnection().deliverRawText(resumed.asXML());
        Log.debug("Resuming session: Ack for {}", h);
        processClientAcknowledgement(h);
        Log.debug("Processing remaining unacked stanzas");
        // Re-deliver unacknowledged stanzas from broken stream (XEP-0198)
        synchronized (this) {
            if(isEnabled()) {
                for (StreamManager.UnackedPacket unacked : unacknowledgedServerStanzas) {
                    try {
                        if (unacked.packet instanceof Message) {
                            Message m = (Message) unacked.packet;
                            if (m.getExtension("delay", "urn:xmpp:delay") == null) {
                                Element delayInformation = m.addChildElement("delay", "urn:xmpp:delay");
                                delayInformation.addAttribute("stamp", XMPPDateTimeFormat.format(unacked.timestamp));
                                delayInformation.addAttribute("from", serverAddress.toBareJID());
                            }
                            session.getConnection().deliver(m);
                        } else if (unacked.packet instanceof Presence) {
                            Presence p = (Presence) unacked.packet;
                            if (p.getExtension("delay", "urn:xmpp:delay") == null) {
                                Element delayInformation = p.addChildElement("delay", "urn:xmpp:delay");
                                delayInformation.addAttribute("stamp", XMPPDateTimeFormat.format(unacked.timestamp));
                                delayInformation.addAttribute("from", serverAddress.toBareJID());
                            }
                            session.getConnection().deliver(p);
                        } else {
                            session.getConnection().deliver(unacked.packet);
                        }
                    } catch (UnauthorizedException e) {
                        Log.warn("Caught unauthorized exception, which seems worrying: ", e);
                    }
                }

                sendServerRequest();
            }
        }
    }

	/**
	 * Determines whether Stream Management enabled for session this
	 * manager belongs to.
	 * @return true when stream management is enabled, otherwise false.
	 */
	public boolean isEnabled() {
		return namespace != null;
	}

	/**
	 * Increments the count of stanzas processed by the server since
	 * Stream Management was enabled.
	 */
	public void incrementServerProcessedStanzas() {
		if(isEnabled()) {
			this.serverProcessedStanzas++;
		}
	}

	/**
	 * The maximum amount of stanzas we keep, waiting for ack.
	 * @return The maximum number of stanzas.
	 */
	private int getMaximumUnacknowledgedStanzas()
	{
		return JiveGlobals.getIntProperty( "stream.management.max-unacked", 10000 );
	}
}
