/*
 * #%L
 * Netarchivesuite - harvester
 * %%
 * Copyright (C) 2005 - 2014 The Royal Danish Library, the Danish State and University Library,
 *             the National Library of France and the Austrian National Library.
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */

package dk.netarkivet.harvester.distribute;

import javax.jms.Message;
import javax.jms.MessageListener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import dk.netarkivet.common.distribute.JMSConnection;
import dk.netarkivet.common.distribute.NetarkivetMessage;
import dk.netarkivet.common.exceptions.ArgumentNotValid;
import dk.netarkivet.common.exceptions.PermissionDenied;
import dk.netarkivet.harvester.harvesting.distribute.CrawlProgressMessage;
import dk.netarkivet.harvester.harvesting.distribute.CrawlStatusMessage;
import dk.netarkivet.harvester.harvesting.distribute.DoOneCrawlMessage;
import dk.netarkivet.harvester.harvesting.distribute.FrontierReportMessage;
import dk.netarkivet.harvester.harvesting.distribute.HarvesterReadyMessage;
import dk.netarkivet.harvester.harvesting.distribute.HarvesterRegistrationRequest;
import dk.netarkivet.harvester.harvesting.distribute.HarvesterRegistrationResponse;
import dk.netarkivet.harvester.harvesting.distribute.JobEndedMessage;
import dk.netarkivet.harvester.indexserver.distribute.IndexRequestMessage;

/**
 * This default message handler shields of all unimplemented methods from the HarvesterMessageVisitor interface.
 * <p>
 * Classes should not implement HarvesterMessageVisitor but extend this class.
 *
 * @see HarvesterMessageVisitor
 */
public abstract class HarvesterMessageHandler implements HarvesterMessageVisitor, MessageListener {
    private static final Logger log = LoggerFactory.getLogger(HarvesterMessageHandler.class);

    /**
     * Unpacks and calls accept() on the message object.
     * <p>
     * This method catches <b>all</b> exceptions and logs them.
     *
     * @param msg an ObjectMessage
     */
    @Override
    public void onMessage(Message msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        log.trace("Message received:\n{}", msg.toString());
        try {
            NetarkivetMessage unpackedMsg = JMSConnection.unpack(msg);
            ((HarvesterMessage) unpackedMsg).accept(this);
        } catch (Throwable t) {
            log.warn("Error processing message '{}'", msg, t);
        }
    }

    /**
     * Handles when a handler receives a message it is not prepare to handle.
     *
     * @param msg The received message.
     * @throws PermissionDenied Always
     */
    private void deny(HarvesterMessage msg) {
        throw new PermissionDenied("'" + this + "' provides no handling for " + msg + " of type "
                + msg.getClass().getName() + " and should not be invoked!");
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a CrawlStatusMessage
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(CrawlStatusMessage msg) throws PermissionDenied {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a DoOneCrawlMessage
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(DoOneCrawlMessage msg) throws PermissionDenied {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link CrawlProgressMessage}
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(CrawlProgressMessage msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link FrontierReportMessage}
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(FrontierReportMessage msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link JobEndedMessage}
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(JobEndedMessage msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link HarvesterReadyMessage}
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(HarvesterReadyMessage msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link IndexReadyMessage}
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(IndexReadyMessage msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link IndexRequestMessage}
     * @throws PermissionDenied when invoked
     */
    @Override
    public void visit(IndexRequestMessage msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link HarvesterRegistrationRequest}
     */
    @Override
    public void visit(HarvesterRegistrationRequest msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

    /**
     * This method should be overridden and implemented by a sub class if message handling is wanted.
     *
     * @param msg a {@link HarvesterRegistrationResponse}
     */
    @Override
    public void visit(HarvesterRegistrationResponse msg) {
        ArgumentNotValid.checkNotNull(msg, "msg");
        deny(msg);
    }

}