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/*
 * Copyright (c) 1998-2009, Peter T Mount

 * All rights reserved.
 *
 * 
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 3 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 Public License for more details.
 * 
 *
 * 
 *   You should have received a copy of the GNU General Public License along
 *   with this program.  If not, see .
 * 
 *
 * 
 *        GNU GENERAL PUBLIC LICENSE - CLASSPATH EXCEPTION
 * 
 *
 * 
 *   Linking this library statically or dynamically with other modules
 *   is making a combined work based on this library. Thus, the terms
 *   and conditions of the GNU General Public License cover the whole
 *   combination.
 * 
 *
 * 
 *   As a special exception, the copyright holders of this library give
 *   you permission to link this library with independent modules to
 *   produce an executable, regardless of the license terms of these
 *   independent modules, and to copy and distribute the resulting
 *   executable under terms of your choice, provided that you also meet,
 *   for each linked independent module, the terms and conditions of the
 *   license of that module.
 * 
 *
 * 
 *   An independent module is a module which is either not derived from or based
 *   on this library, or a module who's classes extend those within this library
 *   as part of the implementation of the library.
 * 
 *
 * 
 *   If you modify this library, you may extend this exception to your version
 *   of the library, but you are not obligated to do so. If you do not wish to
 *   do so, delete this exception statement from your version.
 * 
 */
package uk.org.retep.xmpp;

import java.util.Comparator;
import uk.org.retep.annotations.Singleton;

/**
 *
 * @author peter
 */
@Singleton
public class JIDComparator
        implements Comparator
{

    private static final JIDComparator instance = new JIDComparator();

    public static JIDComparator getInstance()
    {
        return instance;
    }

    @Override
    public int compare( final JID a, final JID b )
    {
        // Test the domain, then process node if they match, and then resource after that
        int r = a.getDomain().compareTo( b.getDomain() );

        if( r != 0 )
        {
            return r;
        }

        // Now the node
        if( a.getNode() == null && b.getNode() == null )
        {
            // both null, then that's as far as we go, they are identical
            return 0;
        }
        else if( a.getNode() == null && b.getNode() != null )
        {
            // Null goes after non-null values
            return Integer.MAX_VALUE;
        }
        else if( a.getNode() != null && b.getNode() == null )
        {
            // same but a < b
            return Integer.MIN_VALUE;
        }

        r = a.getNode().compareTo( b.getNode() );

        if( r != 0 )
        {
            return r;
        }

        // finally the resource
        if( a.getResource() == null && b.getResource() == null )
        {
            return 0;
        }
        else if( a.getResource() == null && b.getResource() != null )
        {
            return Integer.MAX_VALUE;
        }
        else if( a.getResource() != null && b.getResource() == null )
        {
            return Integer.MIN_VALUE;
        }

        return a.getResource().compareTo( b.getResource() );
    }
}