/*
 * Generic graph library
 * Copyright (C) 2000,2003,2004 University of Maryland
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

// $Revision: 1.10 $

package edu.umd.cs.findbugs.graph;

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

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;

/**
 * Comparator to compare GraphVertex objects by their visitation times in a
 * search; for example, it could compare the finishing times produced by
 * DepthFirstSearch.
 */
public class VisitationTimeComparator<VertexType extends GraphVertex<VertexType>> implements Comparator<VertexType>, Serializable {
    private static final long serialVersionUID = 0L;

    /**
     * Compare in ascending order.
     */
    public static final int ASCENDING = 0;

    /**
     * Compare in descending order.
     */
    public static final int DESCENDING = 1;

    private final int[] m_visitationTimeList;

    private final int m_direction;

    /**
     * Constructor.
     *
     * @param visitationTimeList
     *            array of visitation times indexed by vertex label
     * @param direction
     *            either ASCENDING or DESCENDING
     */
    @SuppressFBWarnings("EI2")
    public VisitationTimeComparator(int[] visitationTimeList, int direction) {
        m_visitationTimeList = visitationTimeList;
        m_direction = direction;

        if (direction != ASCENDING && direction != DESCENDING) {
            throw new IllegalArgumentException();
        }
    }

    @Override
    public int compare(VertexType v1, VertexType v2) {
        int f1 = m_visitationTimeList[v1.getLabel()];
        int f2 = m_visitationTimeList[v2.getLabel()];

        if (m_direction == ASCENDING) {
            return f1 - f2;
        } else {
            return f2 - f1;
        }
    }

}

