/*******************************************************************************
 * Copyright (c) 2005, 2010 Andrea Bittau, University College London, and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Andrea Bittau - initial API and implementation from the PsychoPath XPath 2.0
 *     Mukul Gandhi - bug 273760 - wrong namespace for functions and data types
 *     Mukul Gandhi - improved string_value() implementation (motivated by bug, 281822)
 *     David Carver - bug 282223 - implementation of xs:duration.
 *                  - bug 262765 - additional tweak to convert 24:00:00 to 00:00:00
 *     David Carver - bug 280547 - fix dates for comparison 
 *     Mukul Gandhi - bug 280798 - PsychoPath support for JDK 1.4
 *******************************************************************************/

package org.eclipse.wst.xml.xpath2.processor.internal.types;

import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;

import javax.xml.datatype.Duration;
import javax.xml.datatype.XMLGregorianCalendar;

import org.eclipse.wst.xml.xpath2.api.DynamicContext;
import org.eclipse.wst.xml.xpath2.api.Item;
import org.eclipse.wst.xml.xpath2.api.ResultBuffer;
import org.eclipse.wst.xml.xpath2.api.ResultSequence;
import org.eclipse.wst.xml.xpath2.api.typesystem.TypeDefinition;
import org.eclipse.wst.xml.xpath2.processor.DynamicError;
import org.eclipse.wst.xml.xpath2.processor.ResultSequenceFactory;
import org.eclipse.wst.xml.xpath2.processor.internal.function.CmpEq;
import org.eclipse.wst.xml.xpath2.processor.internal.function.CmpGt;
import org.eclipse.wst.xml.xpath2.processor.internal.function.CmpLt;
import org.eclipse.wst.xml.xpath2.processor.internal.function.MathMinus;
import org.eclipse.wst.xml.xpath2.processor.internal.function.MathPlus;
import org.eclipse.wst.xml.xpath2.processor.internal.types.builtin.BuiltinTypeLibrary;

/**
 * A representation of a date and time (and optional timezone)
 */
public class XSDateTime extends CalendarType implements CmpEq, CmpLt, CmpGt,

MathMinus, MathPlus,

Cloneable {
	private static final String XS_DATE_TIME = "xs:dateTime";
	private Calendar _calendar;
	private boolean _timezoned;
	private XSDuration _tz;

	/**
	 * Initiates a new representation of a supplied date and time
	 * 
	 * @param cal
	 *            The Calendar representation of the date and time to be stored
	 * @param tz
	 *            The timezone of the date to be stored.
	 */
	public XSDateTime(Calendar cal, XSDuration tz) {
		_calendar = cal;

		_tz = tz;

		if (tz == null)
			_timezoned = false;
		else
			_timezoned = true;
	}

	/**
	 * Creates a copy of this date and time representation
	 * 
	 * @return A copy of this date and time representation
	 */
	public Object clone() throws CloneNotSupportedException {
		Calendar c = (Calendar) calendar().clone();
		XSDuration t = tz();

		if (t != null)
			t = (XSDuration) t.clone();

		return new XSDateTime(c, t);
	}

	/**
	 * Inititates a new representation of the current date and time
	 */
	public XSDateTime() {
		this(new GregorianCalendar(), null);
	}

	/**
	 * Retrieves the datatype name
	 * 
	 * @return "dateTime" which is the dataype name
	 */
	public String type_name() {
		return "dateTime";
	}

	/**
	 * Check to see if a character is numeric
	 * 
	 * @param x
	 *            Character to be tested
	 * @return True if the character is numeric. False otherwise.
	 */
	public static boolean is_digit(char x) {
		if ('0' <= x && x <= '9')
			return true;
		return false;
	}

	/**
	 * Parses a String representation of a date and time and retrieves the year,
	 * month and day from it
	 * 
	 * @param str
	 *            The String representation of the date (and optional timezone)
	 * @return Integer array of size 3. Element 1 is the year, element 2 is the
	 *         month and element 3 is the day
	 */
	public static int[] parse_date(String str) {
		int state = 0; // 0 expect year or minus
		// 1 getting year
		// 2 getting month
		// 3 getting day

		int[] ret = new int[3];

		for (int i = 0; i < ret.length; i++)
			ret[i] = 0;

		String token = "";
		for (int i = 0; i < str.length(); i++) {
			char x = str.charAt(i);

			switch (state) {
			case 0:
				if (is_digit(x)) {
					token += x;
				} else if (x == '-') {
					token += x;
				} else
					return null;
				state = 1;
				break;

			case 1:
				// we got the year in theory...
				if (x == '-') {

					// check out the unsigned year
					String uy = token;
					if (uy.startsWith("-"))
						uy = uy.substring(1, uy.length());
					int uyl = uy.length();

					if (uyl < 4)
						return null;

					if (uyl == 4) {
						if (uy.compareTo("0000") == 0)
							return null;
					} else if (uy.charAt(0) == '0')
						return null;

					// semms good to me
					ret[0] = Integer.parseInt(token);
					token = "";
					state = 2;
				} else if (is_digit(x))
					token += x;
				else
					return null;
				break;

			case 2:
				// we got the month
				if (x == '-') {
					if (token.length() != 2)
						return null;

					ret[1] = Integer.parseInt(token);
					token = "";
					state = 3;
				} else if (is_digit(x))
					token += x;
				else
					return null;
				break;

			case 3:
				// getting day
				if (is_digit(x))
					token += x;
				else
					return null;
				break;

			default:
				assert false;
				return ret;
			}
		}
		if (state != 3)
			return null;

		// got the day
		if (token.length() != 2)
			return null;

		ret[2] = Integer.parseInt(token);

		return ret;
	}

	// return
	// hour
	// minute
	// seconds
	/**
	 * Parses a String representation of a date and time and retrieves the hour,
	 * minute and seconds from it
	 * 
	 * @param str
	 *            The String representation of the date (and optional timezone)
	 * @return Integer array of size 3. Element 1 is the hour, element 2 is the
	 *         minute and element 3 is the seconds
	 */
	public static double[] parse_time(String str) {
		int state = 0; // 0 getting minute
		// 1 getting hour
		// 2 getting seconds [the whole part]
		// 3 getting fraction of seconds

		double[] ret = new double[3];

		String token = "";

		for (int i = 0; i < str.length(); i++) {
			char x = str.charAt(i);

			switch (state) {
			case 0:
			case 1:
				// got minute / hour
				if (x == ':') {
					if (token.length() != 2)
						return null;
					ret[state] = Integer.parseInt(token);
					state++;
					token = "";
				} else if (is_digit(x))
					token += x;
				else
					return null;
				break;

			case 2:
				if (is_digit(x)) {
					token += x;
					if (token.length() > 2)
						return null;
				} else if (x == '.') {
					token += x;
					state = 3;
				} else
					return null;
				break;

			case 3:
				if (is_digit(x))
					token += x;
				else
					return null;
				break;

			default:
				assert false;
				return null;
			}
		}
		if (!(state == 3 || state == 2))
			return null;

		// get seconds
		// this is whole + dot + nothing else
		if (token.length() == 3)
			return null;

		ret[2] = Double.parseDouble(token);

		if (ret[0] == 24.0) {
			ret[0] = 00.0;
		}

		// XXX sanity check args...
		return ret;
	}

	// returns
	// positive/negative
	// hour
	// minute
	/**
	 * Parses a String representation of a date and time and retrieves the
	 * timezone from it
	 * 
	 * @param str
	 *            The String representation of the date (and optional timezone)
	 * @return Integer array of size 3. Element 1 represents whether the
	 *         timezone is ahead or behind GMT, element 2 is the hour
	 *         displacement and element 3 is the minute displacement.
	 */
	public static int[] parse_timezone(String str) {
		int[] ret = new int[3];

		for (int i = 0; i < ret.length; i++)
			ret[i] = 0;
		ret[0] = 1;

		if (str.equals("Z")) {
			return ret;
		}

		// get initial plus/minus
		if (str.startsWith("+"))
			ret[0] = 1;
		else if (str.startsWith("-"))
			ret[0] = -1;
		else
			return null;

		str = str.substring(1, str.length());

		if (str.length() != (2 + 1 + 2))
			return null;

		try {
			ret[1] = Integer.parseInt(str.substring(0, 2));
			ret[2] = Integer.parseInt(str.substring(3, 5));

			// According to schema spec, timezone is limited to
			// this... [well.. almost...]
			if (ret[1] > 14)
				return null;
			if (ret[2] > 59)
				return null;

			return ret;
		} catch (NumberFormatException err) {
			return null;
		}
	}

	/**
	 * Attempts to set a particular field in the Calendar
	 * 
	 * @param cal
	 *            The Calendar object to set the field in
	 * @param item
	 *            The field to set
	 * @param val
	 *            The value to set the field to
	 * @return True if successfully set. False otherwise (due to out of bounds
	 *         for that field)
	 */
	private static boolean set_item(Calendar cal, int item, int val) {
		int min = cal.getActualMinimum(item);

		if (val < min)
			return false;

		int max = cal.getActualMaximum(item);

		if (val > max)
			return false;

		cal.set(item, val);
		return true;
	}

	/**
	 * Parses a String representation of a date and time and constructs a new
	 * XSDateTime object using that information
	 * 
	 * @param str
	 *            The String representation of the date (and optional timezone)
	 * @return The XSDateTime representation of the date and time (and optional
	 *         timezone)
	 */
	public static XSDateTime parseDateTime(String str) {
		// oh no... not again

		// ok its three things:
		// date T time timezone

		int index = str.indexOf('T');
		if (index == -1)
			return null;

		// split date and rest...
		String date = str.substring(0, index);
		String time = str.substring(index + 1, str.length());
		String timezone = null;

		// check for timezone
		index = time.indexOf('+');
		if (index == -1)
			index = time.indexOf('-');
		if (index == -1)
			index = time.indexOf('Z');
		if (index != -1) {
			timezone = time.substring(index, time.length());
			time = time.substring(0, index);
		}

		// get date
		int d[] = parse_date(date);
		if (d == null)
			return null;

		// SANITY CHEX
		TimeZone UTC = TimeZone.getTimeZone("UTC");
		GregorianCalendar cal = new GregorianCalendar(UTC);

		// year
		int year = d[0];
		if (year < 0) {
			year *= -1;
			cal.set(Calendar.ERA, GregorianCalendar.BC);
		} else {
			cal.set(Calendar.ERA, GregorianCalendar.AD);
		}

		// this is a nice bug....
		// if say the current day is 29...
		// then if we set the month to feb for example, and 29 doesn't
		// exist in that year, then the date screws up.
		cal.set(Calendar.DAY_OF_MONTH, 2);
		cal.set(Calendar.MONTH, 2);

		if (!set_item(cal, Calendar.YEAR, year))
			return null;

		if (!set_item(cal, Calendar.MONTH, d[1] - 1))
			return null;

		if (!set_item(cal, Calendar.DAY_OF_MONTH, d[2]))
			return null;

		// get time
		double t[] = parse_time(time);
		if (t == null)
			return null;

		if (!set_item(cal, Calendar.HOUR_OF_DAY, (int) t[0]))
			return null;

		if (!set_item(cal, Calendar.MINUTE, (int) t[1]))
			return null;

		if (!set_item(cal, Calendar.SECOND, (int) t[2]))
			return null;

		double ms = t[2] - ((int) t[2]);
		ms *= 1000;
		if (!set_item(cal, Calendar.MILLISECOND, (int) ms))
			return null;

		// get timezone
		int tz[] = null;
		XSDuration tzd = null;
		if (timezone != null) {
			tz = parse_timezone(timezone);

			if (tz == null)
				return null;

			tzd = new XSDayTimeDuration(0, tz[1], tz[2], 0.0, tz[0] < 0);

		}

		return new XSDateTime(cal, tzd);
	}

	/**
	 * Creates a new result sequence consisting of the retrievable date and time
	 * value in the supplied result sequence
	 * 
	 * @param arg
	 *            The result sequence from which to extract the date and time
	 *            value.
	 * @throws DynamicError
	 * @return A new result sequence consisting of the date and time value
	 *         supplied.
	 */
	public ResultSequence constructor(ResultSequence arg) throws DynamicError {
		if (arg.empty())
			return ResultBuffer.EMPTY;

		AnyAtomicType aat = (AnyAtomicType) arg.first();
		if (aat instanceof NumericType || aat instanceof XSDuration
				|| aat instanceof XSTime || isGDataType(aat)
				|| aat instanceof XSBoolean || aat instanceof XSBase64Binary
				|| aat instanceof XSHexBinary || aat instanceof XSAnyURI) {
			throw DynamicError.invalidType();
		}

		if (!isCastable(aat)) {
			throw DynamicError.cant_cast(null);
		}

		CalendarType dt = castDateTime(aat);

		if (dt == null)
			throw DynamicError.cant_cast(null);

		return dt;
	}

	private boolean isCastable(AnyAtomicType aat) {
		if (aat instanceof XSString || aat instanceof XSUntypedAtomic) {
			return true;
		}

		if (aat instanceof XSTime) {
			return false;
		}

		if (aat instanceof XSDate || aat instanceof XSDateTime) {
			return true;
		}

		return false;
	}

	private CalendarType castDateTime(AnyAtomicType aat) {
		if (aat instanceof XSDate) {
			XSDate date = (XSDate) aat;
			return new XSDateTime(date.calendar(), date.tz());
		}

		if (aat instanceof XSDateTime) {
			XSDateTime dateTime = (XSDateTime) aat;
			return new XSDateTime(dateTime.calendar(), dateTime.tz());
		}

		return parseDateTime(aat.getStringValue());
	}

	/**
	 * Retrieve the year from the date stored
	 * 
	 * @return the year value of the date stored
	 */
	public int year() {
		int y = _calendar.get(Calendar.YEAR);
		if (_calendar.get(Calendar.ERA) == GregorianCalendar.BC)
			y *= -1;

		return y;
	}

	/**
	 * Retrieve the month from the date stored
	 * 
	 * @return the month value of the date stored
	 */
	public int month() {
		return _calendar.get(Calendar.MONTH) + 1;
	}

	/**
	 * Retrieve the day from the date stored
	 * 
	 * @return the day value of the date stored
	 */
	public int day() {
		return _calendar.get(Calendar.DAY_OF_MONTH);
	}

	/**
	 * Retrieve the hour from the date stored
	 * 
	 * @return the hour value of the date stored
	 */
	public int hour() {
		return _calendar.get(Calendar.HOUR_OF_DAY);
	}

	/**
	 * Retrieve the minute from the date stored
	 * 
	 * @return the minute value of the date stored
	 */
	public int minute() {
		return _calendar.get(Calendar.MINUTE);
	}

	/**
	 * Retrieve the seconds from the date stored
	 * 
	 * @return the seconds value of the date stored
	 */
	public double second() {
		double s = _calendar.get(Calendar.SECOND);

		double ms = _calendar.get(Calendar.MILLISECOND);

		ms /= 1000;

		s += ms;
		return s;
	}

	public boolean timezoned() {
		return _timezoned;
	}

	/**
	 * Pads the supplied number to the supplied number of digits by adding 0's
	 * in front of it
	 * 
	 * @param num
	 *            Number that si to be padded (if neccessay)
	 * @param len
	 *            Desired length after padding
	 * @return String representation of the padded integer
	 */
	public static String pad_int(int num, int len) {
		String ret = "";
		String snum = "" + num;

		int pad = len - snum.length();

		// sort out the negative
		if (num < 0) {
			ret += "-";
			snum = snum.substring(1, snum.length());
			pad++;
		}

		StringBuffer buf = new StringBuffer(ret);
		for (int i = 0; i < pad; i++) {
			buf.append("0");
		}
		buf.append(snum);
		ret = buf.toString();
		return ret;
	}

	/**
	 * Retrieves a String representation of the date and time stored
	 * 
	 * @return String representation of the date and time stored
	 */
	public String getStringValue() {
		String ret = "";

		Calendar adjustFortimezone = calendar();

		if (adjustFortimezone.get(Calendar.ERA) == GregorianCalendar.BC) {
			ret += "-";
		}

		ret += pad_int(adjustFortimezone.get(Calendar.YEAR), 4);

		ret += "-";
		ret += pad_int(month(), 2);

		ret += "-";
		ret += pad_int(adjustFortimezone.get(Calendar.DAY_OF_MONTH), 2);

		// time
		ret += "T";

		ret += pad_int(adjustFortimezone.get(Calendar.HOUR_OF_DAY), 2);

		ret += ":";
		ret += pad_int(adjustFortimezone.get(Calendar.MINUTE), 2);

		ret += ":";
		int isecond = (int) second();
		double sec = second();

		if ((sec - (isecond)) == 0.0)
			ret += pad_int(isecond, 2);
		else {
			if (sec < 10.0)
				ret += "0" + sec;
			else
				ret += sec;
		}

		if (timezoned()) {
			int hrs = _tz.hours();
			int min = _tz.minutes();
			double secs = _tz.seconds();
			if (hrs == 0 && min == 0 && secs == 0) {
				ret += "Z";
			} else {
				String tZoneStr = "";
				if (_tz.negative()) {
					tZoneStr += "-";
				} else {
					tZoneStr += "+";
				}
				tZoneStr += pad_int(hrs, 2);
				tZoneStr += ":";
				tZoneStr += pad_int(min, 2);

				ret += tZoneStr;
			}
		}

		return ret;
	}

	/**
	 * Retrive the datatype full pathname
	 * 
	 * @return "xs:dateTime" which is the datatype full pathname
	 */
	public String string_type() {
		return XS_DATE_TIME;
	}

	/**
	 * Retrieves the Calendar representation of the date stored
	 * 
	 * @return Calendar representation of the date stored
	 */
	public Calendar calendar() {
		return _calendar;
	}

	// comparisons
	/**
	 * Equality comparison on this and the supplied dates and times (taking
	 * timezones into account)
	 * 
	 * @param arg
	 *            XSDateTime representation of the date to compare to
	 * @throws DynamicError
	 * @return True if the two dates and times are represent the same exact
	 *         point in time. False otherwise.
	 */
	public boolean eq(AnyType arg, DynamicContext dynamicContext) throws DynamicError {
		XSDateTime val = (XSDateTime) NumericType.get_single_type(arg,
				XSDateTime.class);
		Calendar thiscal = normalizeCalendar(calendar(), tz());
		Calendar thatcal = normalizeCalendar(val.calendar(), val.tz());

		return thiscal.equals(thatcal);
	}

	/**
	 * Comparison on this and the supplied dates and times (taking timezones
	 * into account)
	 * 
	 * @param arg
	 *            XSDateTime representation of the date to compare to
	 * @throws DynamicError
	 * @return True if in time, this date and time lies before the date and time
	 *         supplied. False otherwise.
	 */
	public boolean lt(AnyType arg, DynamicContext context) throws DynamicError {
		XSDateTime val = (XSDateTime) NumericType.get_single_type(arg,
				XSDateTime.class);
		Calendar thiscal = normalizeCalendar(calendar(), tz());
		Calendar thatcal = normalizeCalendar(val.calendar(), val.tz());

		return thiscal.before(thatcal);
	}

	/**
	 * Comparison on this and the supplied dates and times (taking timezones
	 * into account)
	 * 
	 * @param arg
	 *            XSDateTime representation of the date to compare to
	 * @throws DynamicError
	 * @return True if in time, this date and time lies after the date and time
	 *         supplied. False otherwise.
	 */
	public boolean gt(AnyType arg, DynamicContext context) throws DynamicError {
		XSDateTime val = (XSDateTime) NumericType.get_single_type(arg,
				XSDateTime.class);
		Calendar thiscal = normalizeCalendar(calendar(), tz());
		Calendar thatcal = normalizeCalendar(val.calendar(), val.tz());

		return thiscal.after(thatcal);
	}

	/**
	 * Retrieves the timezone associated with the date stored
	 * 
	 * @return the timezone associated with the date stored
	 */
	public XSDuration tz() {
		return _tz;
	}

	// XXX this is incorrect [epoch]
	/**
	 * Currently unsupported method. Retrieves the date in milliseconds since
	 * the begining of epoch
	 * 
	 * @return Number of milliseconds since the begining of the epoch
	 */
	public double value() {
		return calendar().getTimeInMillis() / 1000.0;
	}

	// math
	/**
	 * Mathematical minus operator between this XSDateTime and a supplied result
	 * sequence (XSDateTime, XDTYearMonthDuration and XDTDayTimeDuration are
	 * only valid ones).
	 * 
	 * @param arg
	 *            The supplied ResultSequence that is on the right of the minus
	 *            operator. If this is an XSDateTime, the result will be a
	 *            XDTDayTimeDuration of the duration of time between these two
	 *            dates. If arg is an XDTYearMonthDuration or an
	 *            XDTDayTimeDuration the result will be a XSDateTime of the
	 *            result of the current date minus the duration of time
	 *            supplied.
	 * @return New ResultSequence consisting of the result of the mathematical
	 *         minus operation.
	 */
	public ResultSequence minus(ResultSequence arg) throws DynamicError {
		if (arg.size() != 1)
			DynamicError.throw_type_error();

		Item at = arg.first();

		if (!(at instanceof XSDateTime) && !(at instanceof XSYearMonthDuration)
				&& !(at instanceof XSDayTimeDuration)) {
			DynamicError.throw_type_error();
		}

		if (at instanceof XSDateTime) {
			return minusXSDateTime(arg);
		}

		if (at instanceof XSYearMonthDuration) {
			return minusXSYearMonthDuration(at);
		}

		if (at instanceof XSDayTimeDuration) {
			return minusXSDayTimeDuration(at);
		}
		return null; // unreach

	}

	private ResultSequence minusXSDateTime(ResultSequence arg)
			throws DynamicError {
		XSDateTime val = (XSDateTime) NumericType.get_single_type(arg,
				XSDateTime.class);

		Calendar thisCal = normalizeCalendar(calendar(), tz());
		Calendar thatCal = normalizeCalendar(val.calendar(), val.tz());
		long duration = thisCal.getTimeInMillis()
				- thatCal.getTimeInMillis();
		Duration dtduration = _datatypeFactory.newDuration(duration);
		return ResultSequenceFactory.create_new(XSDayTimeDuration
				.parseDTDuration(dtduration.toString()));
	}

	private ResultSequence minusXSDayTimeDuration(Item at) {
		XSDuration val = (XSDuration) at;
		try {
			XSDateTime res = (XSDateTime) clone();
			XMLGregorianCalendar xmlCal = _datatypeFactory
					.newXMLGregorianCalendar((GregorianCalendar) calendar());
			Duration dtduration = _datatypeFactory
					.newDuration(val.getStringValue());
			xmlCal.add(dtduration.negate());
			res = new XSDateTime(xmlCal.toGregorianCalendar(), res.tz());

			return ResultSequenceFactory.create_new(res);
		} catch (CloneNotSupportedException ex) {

		}
		return null;
	}

	private ResultSequence minusXSYearMonthDuration(Item at) {
		XSYearMonthDuration val = (XSYearMonthDuration) at;

		try {
			XSDateTime res = (XSDateTime) clone();

			res.calendar().add(Calendar.MONTH, val.monthValue() * -1);
			return ResultSequenceFactory.create_new(res);
		} catch (CloneNotSupportedException ex) {

		}
		return null;
	}

	/**
	 * Mathematical addition operator between this XSDateTime and a supplied
	 * result sequence (XDTYearMonthDuration and XDTDayTimeDuration are only
	 * valid ones).
	 * 
	 * @param arg
	 *            The supplied ResultSequence that is on the right of the minus
	 *            operator. If arg is an XDTYearMonthDuration or an
	 *            XDTDayTimeDuration the result will be a XSDateTime of the
	 *            result of the current date minus the duration of time
	 *            supplied.
	 * @return New ResultSequence consisting of the result of the mathematical
	 *         minus operation.
	 */
	public ResultSequence plus(ResultSequence arg) throws DynamicError {
		if (arg.size() != 1)
			DynamicError.throw_type_error();

		Item at = arg.first();

		try {
			if (at instanceof XSYearMonthDuration) {
				XSYearMonthDuration val = (XSYearMonthDuration) at;

				XSDateTime res = (XSDateTime) clone();

				res.calendar().add(Calendar.MONTH, val.monthValue());
				return ResultSequenceFactory.create_new(res);
			} else if (at instanceof XSDayTimeDuration) {
				XSDuration val = (XSDuration) at;

				XSDateTime res = (XSDateTime) clone();

				XMLGregorianCalendar xmlCal = _datatypeFactory
						.newXMLGregorianCalendar(
								(GregorianCalendar) calendar());
				Duration dtduration = _datatypeFactory
						.newDuration(val.getStringValue());
				xmlCal.add(dtduration);
				res = new XSDateTime(xmlCal.toGregorianCalendar(), res.tz());
				return ResultSequenceFactory.create_new(res);
			} else {
				DynamicError.throw_type_error();
				return null; // unreach
			}
		} catch (CloneNotSupportedException err) {
			assert false;
			return null;
		}

	}

	public TypeDefinition getTypeDefinition() {
		return BuiltinTypeLibrary.XS_DATETIME;
	}

}