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package org.gnunet.consensus;

import org.gnunet.mq.ClientMessageQueue;
import org.gnunet.mq.Envelope;
import org.gnunet.mq.MessageQueue;
import org.gnunet.mq.NotifySentHandler;
import org.gnunet.util.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Multi-peer set reconciliation.
 */
public class Consensus {
    /**
     * Class logger.
     */
    private static final Logger logger = LoggerFactory
            .getLogger(Consensus.class);

    /**
     * Callback for new elements arriving from the service.
     * Also used to notify of consensus failure.
     */
    private final NewElementCallback newElementCallback;

    /**
     * Client connected to the consensus service.
     */
    private Client client;

    /**
     * Message queue for 'client'.
     */
    private MessageQueue client_mq;

    /**
     * Called when conclude has finished.
     */
    private ConcludeCallback concludeCallback;

    /**
     * Message dispatch for messages from the consensus service.
     */
    private class ConsensusMessageReceiver extends RunaboutMessageReceiver {
        public void visit(ConcludeDoneMessage m) {
            if (null == concludeCallback)
            {
                logger.error("unexpected conclude done message");
                return;
            }
            concludeCallback.onConcludeDone();
        }

        public void visit(NewElementMessage m) {
            ConsensusElement element = new ConsensusElement();
            element.element_type = m.element_type;
            element.data = m.element_data;
            newElementCallback.onNewElement(element);
        }

        @Override
        public void handleError() {
            newElementCallback.onNewElement(null);
        }
    }

    /**
     * Create a consensus session.  The set being reconciled is initially
     * empty.  Only reconcile with other peers after
     * GNUNET_CONSENSUS_reconcile has been called.
     *
     * @param num_peers number of peers in the session
     * @param peers array of peers participating in this consensus session
     *              Inclusion of the local peer is optional.
     * @param sessionId session identifier
     *                   Allows a group of peers to have more than consensus session.
     * @param newElementCallback callback, called when a new element is added to the set by
     *                    another peer
     */
    public Consensus(Configuration cfg, int num_peers, PeerIdentity[] peers, HashCode sessionId,
                     NewElementCallback newElementCallback) {
        client = new Client("consensus", cfg);
        client_mq = new ClientMessageQueue(client, new ConsensusMessageReceiver());
        this.newElementCallback = newElementCallback;
    }

    public void insertElement (ConsensusElement element, final InsertDoneCallback idc) {
        InsertElementMessage m = new InsertElementMessage();
        m.element_data = element.data;
        m.element_type = element.element_type;
        Envelope ev = new Envelope(m);
        ev.notifySent(new NotifySentHandler() {
            @Override
            public void onSent() {
                idc.onInsertDone();
            }
        });
        client_mq.send(ev);
    }

    public void conclude(ConcludeCallback concludeCallback) {
        if (null == concludeCallback)
            throw new AssertionError("conclude with empty callback");
        if (null != this.concludeCallback)
            throw new AssertionError("called conclude twice");
        this.concludeCallback = concludeCallback;
    }

    /**
     * Destroy a consensus handle (free all state associated with
     * it, no longer call any of the callbacks).
     */
    public void destroy() {
        client_mq.destroy();
        client_mq = null;
        client.disconnect();
        client = null;
    }
}