/*
 * All content copyright Terracotta, Inc., unless otherwise indicated. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy
 * of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 */

package com.xxl.job.admin.core.cron;

import java.io.Serializable;
import java.text.ParseException;
import java.util.*;

/**
 * Provides a parser and evaluator for unix-like cron expressions. Cron expressions
 * provide the ability to specify complex time combinations such as &quot;At 8:00am every
 * Monday through Friday&quot; or &quot;At 1:30am every last Friday of the month&quot;.
 * <P>
 * Cron expressions are comprised of 6 required fields and one optional field separated by
 * white space. The fields respectively are described as follows:
 *
 * <table cellspacing="8">
 * <tr>
 * <th align="left">Field Name</th>
 * <th align="left">&nbsp;</th>
 * <th align="left">Allowed Values</th>
 * <th align="left">&nbsp;</th>
 * <th align="left">Allowed Special Characters</th>
 * </tr>
 * <tr>
 * <td align="left"><code>Seconds</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>0-59</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * /</code></td>
 * </tr>
 * <tr>
 * <td align="left"><code>Minutes</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>0-59</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * /</code></td>
 * </tr>
 * <tr>
 * <td align="left"><code>Hours</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>0-23</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * /</code></td>
 * </tr>
 * <tr>
 * <td align="left"><code>Day-of-month</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>1-31</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * ? / L W</code></td>
 * </tr>
 * <tr>
 * <td align="left"><code>Month</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>0-11 or JAN-DEC</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * /</code></td>
 * </tr>
 * <tr>
 * <td align="left"><code>Day-of-Week</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>1-7 or SUN-SAT</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * ? / L #</code></td>
 * </tr>
 * <tr>
 * <td align="left"><code>Year (Optional)</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>empty, 1970-2199</code></td>
 * <td align="left">&nbsp;</th>
 * <td align="left"><code>, - * /</code></td>
 * </tr>
 * </table>
 * <P>
 * The '*' character is used to specify all values. For example, &quot;*&quot; in the
 * minute field means &quot;every minute&quot;.
 * <P>
 * The '?' character is allowed for the day-of-month and day-of-week fields. It is used to
 * specify 'no specific value'. This is useful when you need to specify something in one
 * of the two fields, but not the other.
 * <P>
 * The '-' character is used to specify ranges For example &quot;10-12&quot; in the hour
 * field means &quot;the hours 10, 11 and 12&quot;.
 * <P>
 * The ',' character is used to specify additional values. For example
 * &quot;MON,WED,FRI&quot; in the day-of-week field means &quot;the days Monday,
 * Wednesday, and Friday&quot;.
 * <P>
 * The '/' character is used to specify increments. For example &quot;0/15&quot; in the
 * seconds field means &quot;the seconds 0, 15, 30, and 45&quot;. And &quot;5/15&quot; in
 * the seconds field means &quot;the seconds 5, 20, 35, and 50&quot;. Specifying '*'
 * before the '/' is equivalent to specifying 0 is the value to start with. Essentially,
 * for each field in the expression, there is a set of numbers that can be turned on or
 * off. For seconds and minutes, the numbers range from 0 to 59. For hours 0 to 23, for
 * days of the month 0 to 31, and for months 0 to 11 (JAN to DEC). The &quot;/&quot;
 * character simply helps you turn on every &quot;nth&quot; value in the given set. Thus
 * &quot;7/6&quot; in the month field only turns on month &quot;7&quot;, it does NOT mean
 * every 6th month, please note that subtlety.
 * <P>
 * The 'L' character is allowed for the day-of-month and day-of-week fields. This
 * character is short-hand for &quot;last&quot;, but it has different meaning in each of
 * the two fields. For example, the value &quot;L&quot; in the day-of-month field means
 * &quot;the last day of the month&quot; - day 31 for January, day 28 for February on
 * non-leap years. If used in the day-of-week field by itself, it simply means
 * &quot;7&quot; or &quot;SAT&quot;. But if used in the day-of-week field after another
 * value, it means &quot;the last xxx day of the month&quot; - for example &quot;6L&quot;
 * means &quot;the last friday of the month&quot;. You can also specify an offset from the
 * last day of the month, such as "L-3" which would mean the third-to-last day of the
 * calendar month. <i>When using the 'L' option, it is important not to specify lists, or
 * ranges of values, as you'll get confusing/unexpected results.</i>
 * <P>
 * The 'W' character is allowed for the day-of-month field. This character is used to
 * specify the weekday (Monday-Friday) nearest the given day. As an example, if you were
 * to specify &quot;15W&quot; as the value for the day-of-month field, the meaning is:
 * &quot;the nearest weekday to the 15th of the month&quot;. So if the 15th is a Saturday,
 * the trigger will fire on Friday the 14th. If the 15th is a Sunday, the trigger will
 * fire on Monday the 16th. If the 15th is a Tuesday, then it will fire on Tuesday the
 * 15th. However if you specify &quot;1W&quot; as the value for day-of-month, and the 1st
 * is a Saturday, the trigger will fire on Monday the 3rd, as it will not 'jump' over the
 * boundary of a month's days. The 'W' character can only be specified when the
 * day-of-month is a single day, not a range or list of days.
 * <P>
 * The 'L' and 'W' characters can also be combined for the day-of-month expression to
 * yield 'LW', which translates to &quot;last weekday of the month&quot;.
 * <P>
 * The '#' character is allowed for the day-of-week field. This character is used to
 * specify &quot;the nth&quot; XXX day of the month. For example, the value of
 * &quot;6#3&quot; in the day-of-week field means the third Friday of the month (day 6 =
 * Friday and &quot;#3&quot; = the 3rd one in the month). Other examples: &quot;2#1&quot;
 * = the first Monday of the month and &quot;4#5&quot; = the fifth Wednesday of the month.
 * Note that if you specify &quot;#5&quot; and there is not 5 of the given day-of-week in
 * the month, then no firing will occur that month. If the '#' character is used, there
 * can only be one expression in the day-of-week field (&quot;3#1,6#3&quot; is not valid,
 * since there are two expressions).
 * <P>
 * <!--The 'C' character is allowed for the day-of-month and day-of-week fields. This
 * character is short-hand for "calendar". This means values are calculated against the
 * associated calendar, if any. If no calendar is associated, then it is equivalent to
 * having an all-inclusive calendar. A value of "5C" in the day-of-month field means "the
 * first day included by the calendar on or after the 5th". A value of "1C" in the
 * day-of-week field means "the first day included by the calendar on or after Sunday".-->
 * <P>
 * The legal characters and the names of months and days of the week are not case
 * sensitive.
 *
 * <p>
 * <b>NOTES:</b>
 * <ul>
 * <li>Support for specifying both a day-of-week and a day-of-month value is not complete
 * (you'll need to use the '?' character in one of these fields).</li>
 * <li>Overflowing ranges is supported - that is, having a larger number on the left hand
 * side than the right. You might do 22-2 to catch 10 o'clock at night until 2 o'clock in
 * the morning, or you might have NOV-FEB. It is very important to note that overuse of
 * overflowing ranges creates ranges that don't make sense and no effort has been made to
 * determine which interpretation CronExpression chooses. An example would be "0 0 14-6 ?
 * * FRI-MON".</li>
 * </ul>
 * </p>
 *
 * @author Sharada Jambula, James House
 * @author Contributions from Mads Henderson
 * @author Refactoring from CronTrigger to CronExpression by Aaron Craven
 *
 * Borrowed from quartz v2.3.1
 *
 */
public final class CronExpression implements Serializable, Cloneable {

	private static final long serialVersionUID = 12423409423L;

	protected static final int SECOND = 0;

	protected static final int MINUTE = 1;

	protected static final int HOUR = 2;

	protected static final int DAY_OF_MONTH = 3;

	protected static final int MONTH = 4;

	protected static final int DAY_OF_WEEK = 5;

	protected static final int YEAR = 6;

	protected static final int ALL_SPEC_INT = 99; // '*'

	protected static final int NO_SPEC_INT = 98; // '?'

	protected static final Integer ALL_SPEC = ALL_SPEC_INT;

	protected static final Integer NO_SPEC = NO_SPEC_INT;

	protected static final Map<String, Integer> monthMap = new HashMap<String, Integer>(20);

	protected static final Map<String, Integer> dayMap = new HashMap<String, Integer>(60);
	static {
		monthMap.put("JAN", 0);
		monthMap.put("FEB", 1);
		monthMap.put("MAR", 2);
		monthMap.put("APR", 3);
		monthMap.put("MAY", 4);
		monthMap.put("JUN", 5);
		monthMap.put("JUL", 6);
		monthMap.put("AUG", 7);
		monthMap.put("SEP", 8);
		monthMap.put("OCT", 9);
		monthMap.put("NOV", 10);
		monthMap.put("DEC", 11);

		dayMap.put("SUN", 1);
		dayMap.put("MON", 2);
		dayMap.put("TUE", 3);
		dayMap.put("WED", 4);
		dayMap.put("THU", 5);
		dayMap.put("FRI", 6);
		dayMap.put("SAT", 7);
	}

	private final String cronExpression;

	private TimeZone timeZone = null;

	protected transient TreeSet<Integer> seconds;

	protected transient TreeSet<Integer> minutes;

	protected transient TreeSet<Integer> hours;

	protected transient TreeSet<Integer> daysOfMonth;

	protected transient TreeSet<Integer> months;

	protected transient TreeSet<Integer> daysOfWeek;

	protected transient TreeSet<Integer> years;

	protected transient boolean lastdayOfWeek = false;

	protected transient int nthdayOfWeek = 0;

	protected transient boolean lastdayOfMonth = false;

	protected transient boolean nearestWeekday = false;

	protected transient int lastdayOffset = 0;

	protected transient boolean expressionParsed = false;

	public static final int MAX_YEAR = Calendar.getInstance().get(Calendar.YEAR) + 100;

	/**
	 * Constructs a new <CODE>CronExpression</CODE> based on the specified parameter.
	 * @param cronExpression String representation of the cron expression the new object
	 * should represent
	 * @throws java.text.ParseException if the string expression cannot be parsed into a
	 * valid <CODE>CronExpression</CODE>
	 */
	public CronExpression(String cronExpression) throws ParseException {
		if (cronExpression == null) {
			throw new IllegalArgumentException("cronExpression cannot be null");
		}

		this.cronExpression = cronExpression.toUpperCase(Locale.US);

		buildExpression(this.cronExpression);
	}

	/**
	 * Constructs a new {@code CronExpression} as a copy of an existing instance.
	 * @param expression The existing cron expression to be copied
	 */
	public CronExpression(CronExpression expression) {
		/*
		 * We don't call the other constructor here since we need to swallow the
		 * ParseException. We also elide some of the sanity checking as it is not
		 * logically trippable.
		 */
		this.cronExpression = expression.getCronExpression();
		try {
			buildExpression(cronExpression);
		}
		catch (ParseException ex) {
			throw new AssertionError();
		}
		if (expression.getTimeZone() != null) {
			setTimeZone((TimeZone) expression.getTimeZone().clone());
		}
	}

	/**
	 * Indicates whether the given date satisfies the cron expression. Note that
	 * milliseconds are ignored, so two Dates falling on different milliseconds of the
	 * same second will always have the same result here.
	 * @param date the date to evaluate
	 * @return a boolean indicating whether the given date satisfies the cron expression
	 */
	public boolean isSatisfiedBy(Date date) {
		Calendar testDateCal = Calendar.getInstance(getTimeZone());
		testDateCal.setTime(date);
		testDateCal.set(Calendar.MILLISECOND, 0);
		Date originalDate = testDateCal.getTime();

		testDateCal.add(Calendar.SECOND, -1);

		Date timeAfter = getTimeAfter(testDateCal.getTime());

		return ((timeAfter != null) && (timeAfter.equals(originalDate)));
	}

	/**
	 * Returns the next date/time <I>after</I> the given date/time which satisfies the
	 * cron expression.
	 * @param date the date/time at which to begin the search for the next valid date/time
	 * @return the next valid date/time
	 */
	public Date getNextValidTimeAfter(Date date) {
		return getTimeAfter(date);
	}

	/**
	 * Returns the next date/time <I>after</I> the given date/time which does <I>not</I>
	 * satisfy the expression
	 * @param date the date/time at which to begin the search for the next invalid
	 * date/time
	 * @return the next valid date/time
	 */
	public Date getNextInvalidTimeAfter(Date date) {
		long difference = 1000;

		// move back to the nearest second so differences will be accurate
		Calendar adjustCal = Calendar.getInstance(getTimeZone());
		adjustCal.setTime(date);
		adjustCal.set(Calendar.MILLISECOND, 0);
		Date lastDate = adjustCal.getTime();

		Date newDate;

		// FUTURE_TODO: (QUARTZ-481) IMPROVE THIS! The following is a BAD solution to this
		// problem. Performance will be very bad here, depending on the cron expression.
		// It is, however A solution.

		// keep getting the next included time until it's farther than one second
		// apart. At that point, lastDate is the last valid fire time. We return
		// the second immediately following it.
		while (difference == 1000) {
			newDate = getTimeAfter(lastDate);
			if (newDate == null) {
				break;
			}

			difference = newDate.getTime() - lastDate.getTime();

			if (difference == 1000) {
				lastDate = newDate;
			}
		}

		return new Date(lastDate.getTime() + 1000);
	}

	/**
	 * Returns the time zone for which this <code>CronExpression</code> will be resolved.
	 */
	public TimeZone getTimeZone() {
		if (timeZone == null) {
			timeZone = TimeZone.getDefault();
		}

		return timeZone;
	}

	/**
	 * Sets the time zone for which this <code>CronExpression</code> will be resolved.
	 */
	public void setTimeZone(TimeZone timeZone) {
		this.timeZone = timeZone;
	}

	/**
	 * Returns the string representation of the <CODE>CronExpression</CODE>
	 * @return a string representation of the <CODE>CronExpression</CODE>
	 */
	@Override
	public String toString() {
		return cronExpression;
	}

	/**
	 * Indicates whether the specified cron expression can be parsed into a valid cron
	 * expression
	 * @param cronExpression the expression to evaluate
	 * @return a boolean indicating whether the given expression is a valid cron
	 * expression
	 */
	public static boolean isValidExpression(String cronExpression) {

		try {
			new CronExpression(cronExpression);
		}
		catch (ParseException pe) {
			return false;
		}

		return true;
	}

	public static void validateExpression(String cronExpression) throws ParseException {

		new CronExpression(cronExpression);
	}

	////////////////////////////////////////////////////////////////////////////
	//
	// Expression Parsing Functions
	//
	////////////////////////////////////////////////////////////////////////////

	protected void buildExpression(String expression) throws ParseException {
		expressionParsed = true;

		try {

			if (seconds == null) {
				seconds = new TreeSet<Integer>();
			}
			if (minutes == null) {
				minutes = new TreeSet<Integer>();
			}
			if (hours == null) {
				hours = new TreeSet<Integer>();
			}
			if (daysOfMonth == null) {
				daysOfMonth = new TreeSet<Integer>();
			}
			if (months == null) {
				months = new TreeSet<Integer>();
			}
			if (daysOfWeek == null) {
				daysOfWeek = new TreeSet<Integer>();
			}
			if (years == null) {
				years = new TreeSet<Integer>();
			}

			int exprOn = SECOND;

			StringTokenizer exprsTok = new StringTokenizer(expression, " \t", false);

			while (exprsTok.hasMoreTokens() && exprOn <= YEAR) {
				String expr = exprsTok.nextToken().trim();

				// throw an exception if L is used with other days of the month
				if (exprOn == DAY_OF_MONTH && expr.indexOf('L') != -1 && expr.length() > 1 && expr.contains(",")) {
					throw new ParseException(
							"Support for specifying 'L' and 'LW' with other days of the month is not implemented", -1);
				}
				// throw an exception if L is used with other days of the week
				if (exprOn == DAY_OF_WEEK && expr.indexOf('L') != -1 && expr.length() > 1 && expr.contains(",")) {
					throw new ParseException(
							"Support for specifying 'L' with other days of the week is not implemented", -1);
				}
				if (exprOn == DAY_OF_WEEK && expr.indexOf('#') != -1
						&& expr.indexOf('#', expr.indexOf('#') + 1) != -1) {
					throw new ParseException("Support for specifying multiple \"nth\" days is not implemented.", -1);
				}

				StringTokenizer vTok = new StringTokenizer(expr, ",");
				while (vTok.hasMoreTokens()) {
					String v = vTok.nextToken();
					storeExpressionVals(0, v, exprOn);
				}

				exprOn++;
			}

			if (exprOn <= DAY_OF_WEEK) {
				throw new ParseException("Unexpected end of expression.", expression.length());
			}

			if (exprOn <= YEAR) {
				storeExpressionVals(0, "*", YEAR);
			}

			TreeSet<Integer> dow = getSet(DAY_OF_WEEK);
			TreeSet<Integer> dom = getSet(DAY_OF_MONTH);

			// Copying the logic from the UnsupportedOperationException below
			boolean dayOfMSpec = !dom.contains(NO_SPEC);
			boolean dayOfWSpec = !dow.contains(NO_SPEC);

			if (!dayOfMSpec || dayOfWSpec) {
				if (!dayOfWSpec || dayOfMSpec) {
					throw new ParseException(
							"Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.",
							0);
				}
			}
		}
		catch (ParseException pe) {
			throw pe;
		}
		catch (Exception e) {
			throw new ParseException("Illegal cron expression format (" + e.toString() + ")", 0);
		}
	}

	protected int storeExpressionVals(int pos, String s, int type) throws ParseException {

		int incr = 0;
		int i = skipWhiteSpace(pos, s);
		if (i >= s.length()) {
			return i;
		}
		char c = s.charAt(i);
		if ((c >= 'A') && (c <= 'Z') && (!s.equals("L")) && (!s.equals("LW")) && (!s.matches("^L-[0-9]*[W]?"))) {
			String sub = s.substring(i, i + 3);
			int sval = -1;
			int eval = -1;
			if (type == MONTH) {
				sval = getMonthNumber(sub) + 1;
				if (sval <= 0) {
					throw new ParseException("Invalid Month value: '" + sub + "'", i);
				}
				if (s.length() > i + 3) {
					c = s.charAt(i + 3);
					if (c == '-') {
						i += 4;
						sub = s.substring(i, i + 3);
						eval = getMonthNumber(sub) + 1;
						if (eval <= 0) {
							throw new ParseException("Invalid Month value: '" + sub + "'", i);
						}
					}
				}
			}
			else if (type == DAY_OF_WEEK) {
				sval = getDayOfWeekNumber(sub);
				if (sval < 0) {
					throw new ParseException("Invalid Day-of-Week value: '" + sub + "'", i);
				}
				if (s.length() > i + 3) {
					c = s.charAt(i + 3);
					if (c == '-') {
						i += 4;
						sub = s.substring(i, i + 3);
						eval = getDayOfWeekNumber(sub);
						if (eval < 0) {
							throw new ParseException("Invalid Day-of-Week value: '" + sub + "'", i);
						}
					}
					else if (c == '#') {
						try {
							i += 4;
							nthdayOfWeek = Integer.parseInt(s.substring(i));
							if (nthdayOfWeek < 1 || nthdayOfWeek > 5) {
								throw new Exception();
							}
						}
						catch (Exception e) {
							throw new ParseException("A numeric value between 1 and 5 must follow the '#' option", i);
						}
					}
					else if (c == 'L') {
						lastdayOfWeek = true;
						i++;
					}
				}

			}
			else {
				throw new ParseException("Illegal characters for this position: '" + sub + "'", i);
			}
			if (eval != -1) {
				incr = 1;
			}
			addToSet(sval, eval, incr, type);
			return (i + 3);
		}

		if (c == '?') {
			i++;
			if ((i + 1) < s.length() && (s.charAt(i) != ' ' && s.charAt(i + 1) != '\t')) {
				throw new ParseException("Illegal character after '?': " + s.charAt(i), i);
			}
			if (type != DAY_OF_WEEK && type != DAY_OF_MONTH) {
				throw new ParseException("'?' can only be specified for Day-of-Month or Day-of-Week.", i);
			}
			if (type == DAY_OF_WEEK && !lastdayOfMonth) {
				int val = daysOfMonth.last();
				if (val == NO_SPEC_INT) {
					throw new ParseException("'?' can only be specified for Day-of-Month -OR- Day-of-Week.", i);
				}
			}

			addToSet(NO_SPEC_INT, -1, 0, type);
			return i;
		}

		if (c == '*' || c == '/') {
			if (c == '*' && (i + 1) >= s.length()) {
				addToSet(ALL_SPEC_INT, -1, incr, type);
				return i + 1;
			}
			else if (c == '/' && ((i + 1) >= s.length() || s.charAt(i + 1) == ' ' || s.charAt(i + 1) == '\t')) {
				throw new ParseException("'/' must be followed by an integer.", i);
			}
			else if (c == '*') {
				i++;
			}
			c = s.charAt(i);
			if (c == '/') { // is an increment specified?
				i++;
				if (i >= s.length()) {
					throw new ParseException("Unexpected end of string.", i);
				}

				incr = getNumericValue(s, i);

				i++;
				if (incr > 10) {
					i++;
				}
				checkIncrementRange(incr, type, i);
			}
			else {
				incr = 1;
			}

			addToSet(ALL_SPEC_INT, -1, incr, type);
			return i;
		}
		else if (c == 'L') {
			i++;
			if (type == DAY_OF_MONTH) {
				lastdayOfMonth = true;
			}
			if (type == DAY_OF_WEEK) {
				addToSet(7, 7, 0, type);
			}
			if (type == DAY_OF_MONTH && s.length() > i) {
				c = s.charAt(i);
				if (c == '-') {
					ValueSet vs = getValue(0, s, i + 1);
					lastdayOffset = vs.value;
					if (lastdayOffset > 30) {
						throw new ParseException("Offset from last day must be <= 30", i + 1);
					}
					i = vs.pos;
				}
				if (s.length() > i) {
					c = s.charAt(i);
					if (c == 'W') {
						nearestWeekday = true;
						i++;
					}
				}
			}
			return i;
		}
		else if (c >= '0' && c <= '9') {
			int val = Integer.parseInt(String.valueOf(c));
			i++;
			if (i >= s.length()) {
				addToSet(val, -1, -1, type);
			}
			else {
				c = s.charAt(i);
				if (c >= '0' && c <= '9') {
					ValueSet vs = getValue(val, s, i);
					val = vs.value;
					i = vs.pos;
				}
				i = checkNext(i, s, val, type);
				return i;
			}
		}
		else {
			throw new ParseException("Unexpected character: " + c, i);
		}

		return i;
	}

	private void checkIncrementRange(int incr, int type, int idxPos) throws ParseException {
		if (incr > 59 && (type == SECOND || type == MINUTE)) {
			throw new ParseException("Increment > 60 : " + incr, idxPos);
		}
		else if (incr > 23 && (type == HOUR)) {
			throw new ParseException("Increment > 24 : " + incr, idxPos);
		}
		else if (incr > 31 && (type == DAY_OF_MONTH)) {
			throw new ParseException("Increment > 31 : " + incr, idxPos);
		}
		else if (incr > 7 && (type == DAY_OF_WEEK)) {
			throw new ParseException("Increment > 7 : " + incr, idxPos);
		}
		else if (incr > 12 && (type == MONTH)) {
			throw new ParseException("Increment > 12 : " + incr, idxPos);
		}
	}

	protected int checkNext(int pos, String s, int val, int type) throws ParseException {

		int end = -1;
		int i = pos;

		if (i >= s.length()) {
			addToSet(val, end, -1, type);
			return i;
		}

		char c = s.charAt(pos);

		if (c == 'L') {
			if (type == DAY_OF_WEEK) {
				if (val < 1 || val > 7) {
					throw new ParseException("Day-of-Week values must be between 1 and 7", -1);
				}
				lastdayOfWeek = true;
			}
			else {
				throw new ParseException("'L' option is not valid here. (pos=" + i + ")", i);
			}
			TreeSet<Integer> set = getSet(type);
			set.add(val);
			i++;
			return i;
		}

		if (c == 'W') {
			if (type == DAY_OF_MONTH) {
				nearestWeekday = true;
			}
			else {
				throw new ParseException("'W' option is not valid here. (pos=" + i + ")", i);
			}
			if (val > 31) {
				throw new ParseException(
						"The 'W' option does not make sense with values larger than 31 (max number of days in a month)",
						i);
			}
			TreeSet<Integer> set = getSet(type);
			set.add(val);
			i++;
			return i;
		}

		if (c == '#') {
			if (type != DAY_OF_WEEK) {
				throw new ParseException("'#' option is not valid here. (pos=" + i + ")", i);
			}
			i++;
			try {
				nthdayOfWeek = Integer.parseInt(s.substring(i));
				if (nthdayOfWeek < 1 || nthdayOfWeek > 5) {
					throw new Exception();
				}
			}
			catch (Exception e) {
				throw new ParseException("A numeric value between 1 and 5 must follow the '#' option", i);
			}

			TreeSet<Integer> set = getSet(type);
			set.add(val);
			i++;
			return i;
		}

		if (c == '-') {
			i++;
			c = s.charAt(i);
			int v = Integer.parseInt(String.valueOf(c));
			end = v;
			i++;
			if (i >= s.length()) {
				addToSet(val, end, 1, type);
				return i;
			}
			c = s.charAt(i);
			if (c >= '0' && c <= '9') {
				ValueSet vs = getValue(v, s, i);
				end = vs.value;
				i = vs.pos;
			}
			if (i < s.length() && ((c = s.charAt(i)) == '/')) {
				i++;
				c = s.charAt(i);
				int v2 = Integer.parseInt(String.valueOf(c));
				i++;
				if (i >= s.length()) {
					addToSet(val, end, v2, type);
					return i;
				}
				c = s.charAt(i);
				if (c >= '0' && c <= '9') {
					ValueSet vs = getValue(v2, s, i);
					int v3 = vs.value;
					addToSet(val, end, v3, type);
					i = vs.pos;
					return i;
				}
				else {
					addToSet(val, end, v2, type);
					return i;
				}
			}
			else {
				addToSet(val, end, 1, type);
				return i;
			}
		}

		if (c == '/') {
			if ((i + 1) >= s.length() || s.charAt(i + 1) == ' ' || s.charAt(i + 1) == '\t') {
				throw new ParseException("'/' must be followed by an integer.", i);
			}

			i++;
			c = s.charAt(i);
			int v2 = Integer.parseInt(String.valueOf(c));
			i++;
			if (i >= s.length()) {
				checkIncrementRange(v2, type, i);
				addToSet(val, end, v2, type);
				return i;
			}
			c = s.charAt(i);
			if (c >= '0' && c <= '9') {
				ValueSet vs = getValue(v2, s, i);
				int v3 = vs.value;
				checkIncrementRange(v3, type, i);
				addToSet(val, end, v3, type);
				i = vs.pos;
				return i;
			}
			else {
				throw new ParseException("Unexpected character '" + c + "' after '/'", i);
			}
		}

		addToSet(val, end, 0, type);
		i++;
		return i;
	}

	public String getCronExpression() {
		return cronExpression;
	}

	public String getExpressionSummary() {
		StringBuilder buf = new StringBuilder();

		buf.append("seconds: ");
		buf.append(getExpressionSetSummary(seconds));
		buf.append("\n");
		buf.append("minutes: ");
		buf.append(getExpressionSetSummary(minutes));
		buf.append("\n");
		buf.append("hours: ");
		buf.append(getExpressionSetSummary(hours));
		buf.append("\n");
		buf.append("daysOfMonth: ");
		buf.append(getExpressionSetSummary(daysOfMonth));
		buf.append("\n");
		buf.append("months: ");
		buf.append(getExpressionSetSummary(months));
		buf.append("\n");
		buf.append("daysOfWeek: ");
		buf.append(getExpressionSetSummary(daysOfWeek));
		buf.append("\n");
		buf.append("lastdayOfWeek: ");
		buf.append(lastdayOfWeek);
		buf.append("\n");
		buf.append("nearestWeekday: ");
		buf.append(nearestWeekday);
		buf.append("\n");
		buf.append("NthDayOfWeek: ");
		buf.append(nthdayOfWeek);
		buf.append("\n");
		buf.append("lastdayOfMonth: ");
		buf.append(lastdayOfMonth);
		buf.append("\n");
		buf.append("years: ");
		buf.append(getExpressionSetSummary(years));
		buf.append("\n");

		return buf.toString();
	}

	protected String getExpressionSetSummary(java.util.Set<Integer> set) {

		if (set.contains(NO_SPEC)) {
			return "?";
		}
		if (set.contains(ALL_SPEC)) {
			return "*";
		}

		StringBuilder buf = new StringBuilder();

		Iterator<Integer> itr = set.iterator();
		boolean first = true;
		while (itr.hasNext()) {
			Integer iVal = itr.next();
			String val = iVal.toString();
			if (!first) {
				buf.append(",");
			}
			buf.append(val);
			first = false;
		}

		return buf.toString();
	}

	protected String getExpressionSetSummary(java.util.ArrayList<Integer> list) {

		if (list.contains(NO_SPEC)) {
			return "?";
		}
		if (list.contains(ALL_SPEC)) {
			return "*";
		}

		StringBuilder buf = new StringBuilder();

		Iterator<Integer> itr = list.iterator();
		boolean first = true;
		while (itr.hasNext()) {
			Integer iVal = itr.next();
			String val = iVal.toString();
			if (!first) {
				buf.append(",");
			}
			buf.append(val);
			first = false;
		}

		return buf.toString();
	}

	protected int skipWhiteSpace(int i, String s) {
		for (; i < s.length() && (s.charAt(i) == ' ' || s.charAt(i) == '\t'); i++) {
		}

		return i;
	}

	protected int findNextWhiteSpace(int i, String s) {
		for (; i < s.length() && (s.charAt(i) != ' ' || s.charAt(i) != '\t'); i++) {
		}

		return i;
	}

	protected void addToSet(int val, int end, int incr, int type) throws ParseException {

		TreeSet<Integer> set = getSet(type);

		if (type == SECOND || type == MINUTE) {
			if ((val < 0 || val > 59 || end > 59) && (val != ALL_SPEC_INT)) {
				throw new ParseException("Minute and Second values must be between 0 and 59", -1);
			}
		}
		else if (type == HOUR) {
			if ((val < 0 || val > 23 || end > 23) && (val != ALL_SPEC_INT)) {
				throw new ParseException("Hour values must be between 0 and 23", -1);
			}
		}
		else if (type == DAY_OF_MONTH) {
			if ((val < 1 || val > 31 || end > 31) && (val != ALL_SPEC_INT) && (val != NO_SPEC_INT)) {
				throw new ParseException("Day of month values must be between 1 and 31", -1);
			}
		}
		else if (type == MONTH) {
			if ((val < 1 || val > 12 || end > 12) && (val != ALL_SPEC_INT)) {
				throw new ParseException("Month values must be between 1 and 12", -1);
			}
		}
		else if (type == DAY_OF_WEEK) {
			if ((val == 0 || val > 7 || end > 7) && (val != ALL_SPEC_INT) && (val != NO_SPEC_INT)) {
				throw new ParseException("Day-of-Week values must be between 1 and 7", -1);
			}
		}

		if ((incr == 0 || incr == -1) && val != ALL_SPEC_INT) {
			if (val != -1) {
				set.add(val);
			}
			else {
				set.add(NO_SPEC);
			}

			return;
		}

		int startAt = val;
		int stopAt = end;

		if (val == ALL_SPEC_INT && incr <= 0) {
			incr = 1;
			set.add(ALL_SPEC); // put in a marker, but also fill values
		}

		if (type == SECOND || type == MINUTE) {
			if (stopAt == -1) {
				stopAt = 59;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 0;
			}
		}
		else if (type == HOUR) {
			if (stopAt == -1) {
				stopAt = 23;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 0;
			}
		}
		else if (type == DAY_OF_MONTH) {
			if (stopAt == -1) {
				stopAt = 31;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1;
			}
		}
		else if (type == MONTH) {
			if (stopAt == -1) {
				stopAt = 12;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1;
			}
		}
		else if (type == DAY_OF_WEEK) {
			if (stopAt == -1) {
				stopAt = 7;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1;
			}
		}
		else if (type == YEAR) {
			if (stopAt == -1) {
				stopAt = MAX_YEAR;
			}
			if (startAt == -1 || startAt == ALL_SPEC_INT) {
				startAt = 1970;
			}
		}

		// if the end of the range is before the start, then we need to overflow into
		// the next day, month etc. This is done by adding the maximum amount for that
		// type, and using modulus max to determine the value being added.
		int max = -1;
		if (stopAt < startAt) {
			switch (type) {
			case SECOND:
				max = 60;
				break;
			case MINUTE:
				max = 60;
				break;
			case HOUR:
				max = 24;
				break;
			case MONTH:
				max = 12;
				break;
			case DAY_OF_WEEK:
				max = 7;
				break;
			case DAY_OF_MONTH:
				max = 31;
				break;
			case YEAR:
				throw new IllegalArgumentException("Start year must be less than stop year");
			default:
				throw new IllegalArgumentException("Unexpected type encountered");
			}
			stopAt += max;
		}

		for (int i = startAt; i <= stopAt; i += incr) {
			if (max == -1) {
				// ie: there's no max to overflow over
				set.add(i);
			}
			else {
				// take the modulus to get the real value
				int i2 = i % max;

				// 1-indexed ranges should not include 0, and should include their max
				if (i2 == 0 && (type == MONTH || type == DAY_OF_WEEK || type == DAY_OF_MONTH)) {
					i2 = max;
				}

				set.add(i2);
			}
		}
	}

	TreeSet<Integer> getSet(int type) {
		switch (type) {
		case SECOND:
			return seconds;
		case MINUTE:
			return minutes;
		case HOUR:
			return hours;
		case DAY_OF_MONTH:
			return daysOfMonth;
		case MONTH:
			return months;
		case DAY_OF_WEEK:
			return daysOfWeek;
		case YEAR:
			return years;
		default:
			return null;
		}
	}

	protected ValueSet getValue(int v, String s, int i) {
		char c = s.charAt(i);
		StringBuilder s1 = new StringBuilder(String.valueOf(v));
		while (c >= '0' && c <= '9') {
			s1.append(c);
			i++;
			if (i >= s.length()) {
				break;
			}
			c = s.charAt(i);
		}
		ValueSet val = new ValueSet();

		val.pos = (i < s.length()) ? i : i + 1;
		val.value = Integer.parseInt(s1.toString());
		return val;
	}

	protected int getNumericValue(String s, int i) {
		int endOfVal = findNextWhiteSpace(i, s);
		String val = s.substring(i, endOfVal);
		return Integer.parseInt(val);
	}

	protected int getMonthNumber(String s) {
		Integer integer = monthMap.get(s);

		if (integer == null) {
			return -1;
		}

		return integer;
	}

	protected int getDayOfWeekNumber(String s) {
		Integer integer = dayMap.get(s);

		if (integer == null) {
			return -1;
		}

		return integer;
	}

	////////////////////////////////////////////////////////////////////////////
	//
	// Computation Functions
	//
	////////////////////////////////////////////////////////////////////////////

	public Date getTimeAfter(Date afterTime) {

		// Computation is based on Gregorian year only.
		Calendar cl = new java.util.GregorianCalendar(getTimeZone());

		// move ahead one second, since we're computing the time *after* the
		// given time
		afterTime = new Date(afterTime.getTime() + 1000);
		// CronTrigger does not deal with milliseconds
		cl.setTime(afterTime);
		cl.set(Calendar.MILLISECOND, 0);

		boolean gotOne = false;
		// loop until we've computed the next time, or we've past the endTime
		while (!gotOne) {

			// if (endTime != null && cl.getTime().after(endTime)) return null;
			if (cl.get(Calendar.YEAR) > 2999) { // prevent endless loop...
				return null;
			}

			SortedSet<Integer> st = null;
			int t = 0;

			int sec = cl.get(Calendar.SECOND);
			int min = cl.get(Calendar.MINUTE);

			// get second.................................................
			st = seconds.tailSet(sec);
			if (st != null && st.size() != 0) {
				sec = st.first();
			}
			else {
				sec = seconds.first();
				min++;
				cl.set(Calendar.MINUTE, min);
			}
			cl.set(Calendar.SECOND, sec);

			min = cl.get(Calendar.MINUTE);
			int hr = cl.get(Calendar.HOUR_OF_DAY);
			t = -1;

			// get minute.................................................
			st = minutes.tailSet(min);
			if (st != null && st.size() != 0) {
				t = min;
				min = st.first();
			}
			else {
				min = minutes.first();
				hr++;
			}
			if (min != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, min);
				setCalendarHour(cl, hr);
				continue;
			}
			cl.set(Calendar.MINUTE, min);

			hr = cl.get(Calendar.HOUR_OF_DAY);
			int day = cl.get(Calendar.DAY_OF_MONTH);
			t = -1;

			// get hour...................................................
			st = hours.tailSet(hr);
			if (st != null && st.size() != 0) {
				t = hr;
				hr = st.first();
			}
			else {
				hr = hours.first();
				day++;
			}
			if (hr != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, 0);
				cl.set(Calendar.DAY_OF_MONTH, day);
				setCalendarHour(cl, hr);
				continue;
			}
			cl.set(Calendar.HOUR_OF_DAY, hr);

			day = cl.get(Calendar.DAY_OF_MONTH);
			int mon = cl.get(Calendar.MONTH) + 1;
			// '+ 1' because calendar is 0-based for this field, and we are
			// 1-based
			t = -1;
			int tmon = mon;

			// get day...................................................
			boolean dayOfMSpec = !daysOfMonth.contains(NO_SPEC);
			boolean dayOfWSpec = !daysOfWeek.contains(NO_SPEC);
			if (dayOfMSpec && !dayOfWSpec) { // get day by day of month rule
				st = daysOfMonth.tailSet(day);
				if (lastdayOfMonth) {
					if (!nearestWeekday) {
						t = day;
						day = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
						day -= lastdayOffset;
						if (t > day) {
							mon++;
							if (mon > 12) {
								mon = 1;
								tmon = 3333; // ensure test of mon != tmon further below
												// fails
								cl.add(Calendar.YEAR, 1);
							}
							day = 1;
						}
					}
					else {
						t = day;
						day = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
						day -= lastdayOffset;

						java.util.Calendar tcal = java.util.Calendar.getInstance(getTimeZone());
						tcal.set(Calendar.SECOND, 0);
						tcal.set(Calendar.MINUTE, 0);
						tcal.set(Calendar.HOUR_OF_DAY, 0);
						tcal.set(Calendar.DAY_OF_MONTH, day);
						tcal.set(Calendar.MONTH, mon - 1);
						tcal.set(Calendar.YEAR, cl.get(Calendar.YEAR));

						int ldom = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
						int dow = tcal.get(Calendar.DAY_OF_WEEK);

						if (dow == Calendar.SATURDAY && day == 1) {
							day += 2;
						}
						else if (dow == Calendar.SATURDAY) {
							day -= 1;
						}
						else if (dow == Calendar.SUNDAY && day == ldom) {
							day -= 2;
						}
						else if (dow == Calendar.SUNDAY) {
							day += 1;
						}

						tcal.set(Calendar.SECOND, sec);
						tcal.set(Calendar.MINUTE, min);
						tcal.set(Calendar.HOUR_OF_DAY, hr);
						tcal.set(Calendar.DAY_OF_MONTH, day);
						tcal.set(Calendar.MONTH, mon - 1);
						Date nTime = tcal.getTime();
						if (nTime.before(afterTime)) {
							day = 1;
							mon++;
						}
					}
				}
				else if (nearestWeekday) {
					t = day;
					day = daysOfMonth.first();

					java.util.Calendar tcal = java.util.Calendar.getInstance(getTimeZone());
					tcal.set(Calendar.SECOND, 0);
					tcal.set(Calendar.MINUTE, 0);
					tcal.set(Calendar.HOUR_OF_DAY, 0);
					tcal.set(Calendar.DAY_OF_MONTH, day);
					tcal.set(Calendar.MONTH, mon - 1);
					tcal.set(Calendar.YEAR, cl.get(Calendar.YEAR));

					int ldom = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
					int dow = tcal.get(Calendar.DAY_OF_WEEK);

					if (dow == Calendar.SATURDAY && day == 1) {
						day += 2;
					}
					else if (dow == Calendar.SATURDAY) {
						day -= 1;
					}
					else if (dow == Calendar.SUNDAY && day == ldom) {
						day -= 2;
					}
					else if (dow == Calendar.SUNDAY) {
						day += 1;
					}

					tcal.set(Calendar.SECOND, sec);
					tcal.set(Calendar.MINUTE, min);
					tcal.set(Calendar.HOUR_OF_DAY, hr);
					tcal.set(Calendar.DAY_OF_MONTH, day);
					tcal.set(Calendar.MONTH, mon - 1);
					Date nTime = tcal.getTime();
					if (nTime.before(afterTime)) {
						day = daysOfMonth.first();
						mon++;
					}
				}
				else if (st != null && st.size() != 0) {
					t = day;
					day = st.first();
					// make sure we don't over-run a short month, such as february
					int lastDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
					if (day > lastDay) {
						day = daysOfMonth.first();
						mon++;
					}
				}
				else {
					day = daysOfMonth.first();
					mon++;
				}

				if (day != t || mon != tmon) {
					cl.set(Calendar.SECOND, 0);
					cl.set(Calendar.MINUTE, 0);
					cl.set(Calendar.HOUR_OF_DAY, 0);
					cl.set(Calendar.DAY_OF_MONTH, day);
					cl.set(Calendar.MONTH, mon - 1);
					// '- 1' because calendar is 0-based for this field, and we
					// are 1-based
					continue;
				}
			}
			else if (dayOfWSpec && !dayOfMSpec) { // get day by day of week rule
				if (lastdayOfWeek) { // are we looking for the last XXX day of
					// the month?
					int dow = daysOfWeek.first(); // desired
					// d-o-w
					int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
					int daysToAdd = 0;
					if (cDow < dow) {
						daysToAdd = dow - cDow;
					}
					if (cDow > dow) {
						daysToAdd = dow + (7 - cDow);
					}

					int lDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));

					if (day + daysToAdd > lDay) { // did we already miss the
						// last one?
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, 1);
						cl.set(Calendar.MONTH, mon);
						// no '- 1' here because we are promoting the month
						continue;
					}

					// find date of last occurrence of this day in this month...
					while ((day + daysToAdd + 7) <= lDay) {
						daysToAdd += 7;
					}

					day += daysToAdd;

					if (daysToAdd > 0) {
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, day);
						cl.set(Calendar.MONTH, mon - 1);
						// '- 1' here because we are not promoting the month
						continue;
					}

				}
				else if (nthdayOfWeek != 0) {
					// are we looking for the Nth XXX day in the month?
					int dow = daysOfWeek.first(); // desired
					// d-o-w
					int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
					int daysToAdd = 0;
					if (cDow < dow) {
						daysToAdd = dow - cDow;
					}
					else if (cDow > dow) {
						daysToAdd = dow + (7 - cDow);
					}

					boolean dayShifted = false;
					if (daysToAdd > 0) {
						dayShifted = true;
					}

					day += daysToAdd;
					int weekOfMonth = day / 7;
					if (day % 7 > 0) {
						weekOfMonth++;
					}

					daysToAdd = (nthdayOfWeek - weekOfMonth) * 7;
					day += daysToAdd;
					if (daysToAdd < 0 || day > getLastDayOfMonth(mon, cl.get(Calendar.YEAR))) {
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, 1);
						cl.set(Calendar.MONTH, mon);
						// no '- 1' here because we are promoting the month
						continue;
					}
					else if (daysToAdd > 0 || dayShifted) {
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, day);
						cl.set(Calendar.MONTH, mon - 1);
						// '- 1' here because we are NOT promoting the month
						continue;
					}
				}
				else {
					int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
					int dow = daysOfWeek.first(); // desired
					// d-o-w
					st = daysOfWeek.tailSet(cDow);
					if (st != null && st.size() > 0) {
						dow = st.first();
					}

					int daysToAdd = 0;
					if (cDow < dow) {
						daysToAdd = dow - cDow;
					}
					if (cDow > dow) {
						daysToAdd = dow + (7 - cDow);
					}

					int lDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));

					if (day + daysToAdd > lDay) { // will we pass the end of
						// the month?
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, 1);
						cl.set(Calendar.MONTH, mon);
						// no '- 1' here because we are promoting the month
						continue;
					}
					else if (daysToAdd > 0) { // are we swithing days?
						cl.set(Calendar.SECOND, 0);
						cl.set(Calendar.MINUTE, 0);
						cl.set(Calendar.HOUR_OF_DAY, 0);
						cl.set(Calendar.DAY_OF_MONTH, day + daysToAdd);
						cl.set(Calendar.MONTH, mon - 1);
						// '- 1' because calendar is 0-based for this field,
						// and we are 1-based
						continue;
					}
				}
			}
			else { // dayOfWSpec && !dayOfMSpec
				throw new UnsupportedOperationException(
						"Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.");
			}
			cl.set(Calendar.DAY_OF_MONTH, day);

			mon = cl.get(Calendar.MONTH) + 1;
			// '+ 1' because calendar is 0-based for this field, and we are
			// 1-based
			int year = cl.get(Calendar.YEAR);
			t = -1;

			// test for expressions that never generate a valid fire date,
			// but keep looping...
			if (year > MAX_YEAR) {
				return null;
			}

			// get month...................................................
			st = months.tailSet(mon);
			if (st != null && st.size() != 0) {
				t = mon;
				mon = st.first();
			}
			else {
				mon = months.first();
				year++;
			}
			if (mon != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, 0);
				cl.set(Calendar.HOUR_OF_DAY, 0);
				cl.set(Calendar.DAY_OF_MONTH, 1);
				cl.set(Calendar.MONTH, mon - 1);
				// '- 1' because calendar is 0-based for this field, and we are
				// 1-based
				cl.set(Calendar.YEAR, year);
				continue;
			}
			cl.set(Calendar.MONTH, mon - 1);
			// '- 1' because calendar is 0-based for this field, and we are
			// 1-based

			year = cl.get(Calendar.YEAR);
			t = -1;

			// get year...................................................
			st = years.tailSet(year);
			if (st != null && st.size() != 0) {
				t = year;
				year = st.first();
			}
			else {
				return null; // ran out of years...
			}

			if (year != t) {
				cl.set(Calendar.SECOND, 0);
				cl.set(Calendar.MINUTE, 0);
				cl.set(Calendar.HOUR_OF_DAY, 0);
				cl.set(Calendar.DAY_OF_MONTH, 1);
				cl.set(Calendar.MONTH, 0);
				// '- 1' because calendar is 0-based for this field, and we are
				// 1-based
				cl.set(Calendar.YEAR, year);
				continue;
			}
			cl.set(Calendar.YEAR, year);

			gotOne = true;
		} // while( !done )

		return cl.getTime();
	}

	/**
	 * Advance the calendar to the particular hour paying particular attention to daylight
	 * saving problems.
	 * @param cal the calendar to operate on
	 * @param hour the hour to set
	 */
	protected void setCalendarHour(Calendar cal, int hour) {
		cal.set(java.util.Calendar.HOUR_OF_DAY, hour);
		if (cal.get(java.util.Calendar.HOUR_OF_DAY) != hour && hour != 24) {
			cal.set(java.util.Calendar.HOUR_OF_DAY, hour + 1);
		}
	}

	/**
	 * NOT YET IMPLEMENTED: Returns the time before the given time that the
	 * <code>CronExpression</code> matches.
	 */
	public Date getTimeBefore(Date endTime) {
		// FUTURE_TODO: implement QUARTZ-423
		return null;
	}

	/**
	 * NOT YET IMPLEMENTED: Returns the final time that the <code>CronExpression</code>
	 * will match.
	 */
	public Date getFinalFireTime() {
		// FUTURE_TODO: implement QUARTZ-423
		return null;
	}

	protected boolean isLeapYear(int year) {
		return ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));
	}

	protected int getLastDayOfMonth(int monthNum, int year) {

		switch (monthNum) {
		case 1:
			return 31;
		case 2:
			return (isLeapYear(year)) ? 29 : 28;
		case 3:
			return 31;
		case 4:
			return 30;
		case 5:
			return 31;
		case 6:
			return 30;
		case 7:
			return 31;
		case 8:
			return 31;
		case 9:
			return 30;
		case 10:
			return 31;
		case 11:
			return 30;
		case 12:
			return 31;
		default:
			throw new IllegalArgumentException("Illegal month number: " + monthNum);
		}
	}

	private void readObject(java.io.ObjectInputStream stream) throws java.io.IOException, ClassNotFoundException {

		stream.defaultReadObject();
		try {
			buildExpression(cronExpression);
		}
		catch (Exception ignore) {
		} // never happens
	}

	@Override
	@Deprecated
	public Object clone() {
		return new CronExpression(this);
	}

}

class ValueSet {

	public int value;

	public int pos;

}
