/*
 * This is eMonocot, a global online biodiversity information resource.
 *
 * Copyright © 2011–2015 The Board of Trustees of the Royal Botanic Gardens, Kew and The University of Oxford
 *
 * eMonocot is free software: you can redistribute it and/or modify it under the terms of the
 * GNU Affero General Public License as published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * eMonocot 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 Affero General Public License for more details.
 *
 * The complete text of the GNU Affero General Public License is in the source repository as the file
 * ‘COPYING’.  It is also available from <http://www.gnu.org/licenses/>.
 */
package org.emonocot.model.compare;

import java.util.Comparator;

import org.apache.commons.collections.comparators.NullComparator;
import org.emonocot.model.Reference;

public class ReferenceComparator implements Comparator<Reference> {

	private NullComparator nullSafeStringComparator;

	public ReferenceComparator() {
		Comparator<String> stringComparator = new Comparator<String>() {

			@Override
			public int compare(String o1, String o2) {
				return o1.compareTo(o2);
			}

		};
		nullSafeStringComparator = new NullComparator(stringComparator, false);
	}

	@Override
	public int compare(Reference o1, Reference o2) {
		int compareDate = nullSafeStringComparator.compare(o1.getDate(), o2.getDate());
		if(compareDate == 0) {
			int compareAuthor = nullSafeStringComparator.compare(o1.getCreator(), o2.getCreator());
			if(compareAuthor == 0) {
				int compareTitle = nullSafeStringComparator.compare(o1.getTitle(), o2.getTitle());
				if(compareTitle == 0) {
					return nullSafeStringComparator.compare(o1.getBibliographicCitation(), o2.getBibliographicCitation());
				} else {
					return compareTitle;
				}
			} else {
				return compareAuthor;
			}
		} else {
			return -1 * compareDate;
		}
	}

}