/*
 * Sun Public License Notice
 *
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 *
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2000 Sun
 * Microsystems, Inc. All Rights Reserved.
 */
package org.netbeans.lib.cvsclient.admin;

/**
 * A class for comparing the file's date and the CVS/Entries date.
 *
 * @author  Thomas Singer
 * @version Sep 29, 2001
 */
public class DateComparator {

    private static final long SECONDS_PER_HOUR = 3600;

    private static final DateComparator singleton = new DateComparator();

    /**
     * Returns an instance of a DateComparator.
     */
    public static DateComparator getInstance() {
        return singleton;
    }

    /**
     * This class is a singleton. There is no need to subclass or
     * instantiate it outside.
     */
    private DateComparator() {
    }

    /**
     * Compares the specified dates, whether they should be treated as equal.
     * Returns true to indicate equality.
     */
    public boolean equals(final long fileTime, final long entryTime) {
        final long fileTimeSeconds = fileTime / 1000;
        final long entryTimeSeconds = entryTime / 1000;
        final long difference = Math.abs(fileTimeSeconds - entryTimeSeconds);
        // differences smaller than 3 seconds are treated as equal
        if (difference < 3) {
            return true;
        }

        // 1-hour-differences (caused by daylight-saving) are treated as equal
        if (difference >= SECONDS_PER_HOUR - 3
                && difference <= SECONDS_PER_HOUR + 3) {
            return true;
        }
        return false;
    }
}