/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2000 Intersect Software Corporation

This library 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 library 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
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/

package net.wotonomy.foundation.internal;

import java.io.Serializable;
import java.util.Comparator;

/**
 * A Comparator that will sort elements based on the property specified in the
 * constructor.
 *
 * @author michael@mpowers.net
 * @author $Author: cgruber $
 * @version $Revision: 893 $
 */
public class PropertyComparator<T> implements Comparator<T>, Serializable {
	private static final long serialVersionUID = -3028294144521868334L;
	private String property;

	/**
	 * Standard constructor to configure the comparator.
	 * 
	 * @param aProperty A property whose value is used to sort elements.
	 */
	public PropertyComparator(String aProperty) {
		property = aProperty;
	}

	// interface Comparator

	@SuppressWarnings("unchecked")
	@Override
	public int compare(Object o1, Object o2) {
		Object v1 = Introspector.get(o1, property);
		Object v2 = Introspector.get(o2, property);
		if (v1 instanceof Comparable<?>) {
			return ((Comparable<Object>) v1).compareTo(v2);
		} else if (v2 instanceof Comparable) {
			return ((Comparable<Object>) v2).compareTo(v1);
		} else {
			if (v1 == null) {
				if (v2 == null) {
					return 0; // both nulls are equal
				}
				return -1; // null is less than any object
			} else if (v2 == null) {
				return 1; // any object is greater than null
			}
		}
		// last resort: compare string conversions
		return v1.toString().compareTo(v2.toString());
	}

	@Override
	public boolean equals(Object obj) {
		return (obj instanceof PropertyComparator);
	}
}

/*
 * $Log$ Revision 1.2 2006/02/16 13:11:47 cgruber Check in all sources in
 * eclipse-friendly maven-enabled packages.
 *
 * Revision 1.1.1.1 2000/12/21 15:52:07 mpowers Contributing wotonomy.
 *
 * Revision 1.2 2000/12/20 16:25:46 michael Added log to all files.
 *
 *
 */