// DateParser.java
// $Id: DateParser.java,v 1.3 2001/01/04 13:26:19 bmahe Exp $
// (c) COPYRIGHT MIT, INRIA and Keio, 2000.
// Please first read the full copyright statement in file COPYRIGHT.html
package org.w3c.util;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
import java.util.TimeZone;

/**
 * Date parser for ISO 8601 format 
 * http://www.w3.org/TR/1998/NOTE-datetime-19980827
 * @version $Revision: 1.3 $
 * @author  Benoît Mahé (bmahe@w3.org)
 */
public class DateParser {

    private static boolean check(StringTokenizer st, String token) 
	throws InvalidDateException
    {
	try {
	    if (st.nextToken().equals(token)) {
		return true;
	    } else {
		throw new InvalidDateException("Missing ["+token+"]");
	    }
	} catch (NoSuchElementException ex) {
	    return false;
	}
    }

    private static Calendar getCalendar(String isodate) 
    	throws InvalidDateException
    {
	// YYYY-MM-DDThh:mm:ss.sTZD
	StringTokenizer st = new StringTokenizer(isodate, "-T:.+Z", true);

	Calendar calendar = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
	calendar.clear();
	try {
	    // Year
	    if (st.hasMoreTokens()) {
		int year = Integer.parseInt(st.nextToken());
		calendar.set(Calendar.YEAR, year);
	    } else {
		return calendar;
	    }
	    // Month
	    if (check(st, "-") && (st.hasMoreTokens())) {
		int month = Integer.parseInt(st.nextToken()) -1;
		calendar.set(Calendar.MONTH, month);
	    } else {
		return calendar;
	    }
	    // Day
	    if (check(st, "-") && (st.hasMoreTokens())) {
		int day = Integer.parseInt(st.nextToken());
		calendar.set(Calendar.DAY_OF_MONTH, day);
	    } else {
		return calendar;
	    }
	    // Hour
	    if (check(st, "T") && (st.hasMoreTokens())) {
		int hour = Integer.parseInt(st.nextToken());
		calendar.set(Calendar.HOUR_OF_DAY, hour);
	    } else {
		calendar.set(Calendar.HOUR_OF_DAY, 0);
		calendar.set(Calendar.MINUTE, 0);
		calendar.set(Calendar.SECOND, 0);
		calendar.set(Calendar.MILLISECOND, 0);
		return calendar;
	    }
	    // Minutes
	    if (check(st, ":") && (st.hasMoreTokens())) {
		int minutes = Integer.parseInt(st.nextToken());
		calendar.set(Calendar.MINUTE, minutes);
	    } else {
		calendar.set(Calendar.MINUTE, 0);
		calendar.set(Calendar.SECOND, 0);
		calendar.set(Calendar.MILLISECOND, 0);
		return calendar;
	    }

	    //
	    // Not mandatory now
	    //

	    // Secondes
	    if (! st.hasMoreTokens()) {
		return calendar;
	    }
	    String tok = st.nextToken();
	    if (tok.equals(":")) { // secondes
		if (st.hasMoreTokens()) {
		    int secondes = Integer.parseInt(st.nextToken());
		    calendar.set(Calendar.SECOND, secondes);
		    if (! st.hasMoreTokens()) {
			return calendar;
		    }
		    // frac sec
		    tok = st.nextToken();
		    if (tok.equals(".")) {
			// bug fixed, thx to Martin Bottcher
			String nt = st.nextToken();
			while(nt.length() < 3) {
			    nt += "0";
			}
			nt = nt.substring( 0, 3 ); //Cut trailing chars..
			int millisec = Integer.parseInt(nt);
			//int millisec = Integer.parseInt(st.nextToken()) * 10;
			calendar.set(Calendar.MILLISECOND, millisec);
			if (! st.hasMoreTokens()) {
			    return calendar;
			}
			tok = st.nextToken();
		    } else {
			calendar.set(Calendar.MILLISECOND, 0);
		    }
		} else {
		    throw new InvalidDateException("No secondes specified");
		}
	    } else {
		calendar.set(Calendar.SECOND, 0);
		calendar.set(Calendar.MILLISECOND, 0);
	    }
	    // Timezone
	    if (! tok.equals("Z")) { // UTC
		if (! (tok.equals("+") || tok.equals("-"))) {
		    throw new InvalidDateException("only Z, + or - allowed");
		}
		boolean plus = tok.equals("+");
		if (! st.hasMoreTokens()) {
		    throw new InvalidDateException("Missing hour field");
		}
		int tzhour = Integer.parseInt(st.nextToken());
		int tzmin  = 0;
		if (check(st, ":") && (st.hasMoreTokens())) {
		    tzmin = Integer.parseInt(st.nextToken());
		} else {
		    throw new InvalidDateException("Missing minute field");
		}
		if (plus) {
		    calendar.add(Calendar.HOUR, tzhour);
		    calendar.add(Calendar.MINUTE, tzmin);
		} else {
		    calendar.add(Calendar.HOUR, -tzhour);
		    calendar.add(Calendar.MINUTE, -tzmin);
		}
	    }
	} catch (NumberFormatException ex) {
	    throw new InvalidDateException("["+ex.getMessage()+
					   "] is not an integer");
	}
	return calendar;
    }

    /**
     * Parse the given string in ISO 8601 format and build a Date object.
     * @param isodate the date in ISO 8601 format
     * @return a Date instance
     * @exception InvalidDateException if the date is not valid
     */
    public static Date parse(String isodate) 
    	throws InvalidDateException 
    {
	Calendar calendar = getCalendar(isodate);
	return calendar.getTime();
    }

    private static String twoDigit(int i) {
	if (i >=0 && i < 10) {
	    return "0"+String.valueOf(i);
	}
	return String.valueOf(i);
    }

    /**
     * Generate a ISO 8601 date 
     * @param date a Date instance
     * @return a string representing the date in the ISO 8601 format
     */
    public static String getIsoDate(Date date) {
	Calendar calendar = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
	calendar.setTime(date);
	StringBuffer buffer = new StringBuffer();
	buffer.append(calendar.get(Calendar.YEAR));
	buffer.append("-");
	buffer.append(twoDigit(calendar.get(Calendar.MONTH) + 1));
	buffer.append("-");
	buffer.append(twoDigit(calendar.get(Calendar.DAY_OF_MONTH)));
	buffer.append("T");
	buffer.append(twoDigit(calendar.get(Calendar.HOUR_OF_DAY)));
	buffer.append(":");
	buffer.append(twoDigit(calendar.get(Calendar.MINUTE)));
	buffer.append(":");
	buffer.append(twoDigit(calendar.get(Calendar.SECOND)));
	buffer.append(".");
	buffer.append(twoDigit(calendar.get(Calendar.MILLISECOND) / 10));
	buffer.append("Z");
	return buffer.toString();
    }

    public static void test(String isodate) {
	System.out.println("----------------------------------");
	try {
	    Date date = parse(isodate);
	    System.out.println(">> "+isodate);
	    System.out.println(">> "+date.toString()+" ["+date.getTime()+"]");
	    System.out.println(">> "+getIsoDate(date));
	} catch (InvalidDateException ex) {
	    System.err.println(isodate+" is invalid");
	    System.err.println(ex.getMessage());
	}
	System.out.println("----------------------------------");
    }

    public static void test(Date date) {
	String isodate = null;
	System.out.println("----------------------------------");
	try {
	    System.out.println(">> "+date.toString()+" ["+date.getTime()+"]");
	    isodate = getIsoDate(date);
	    System.out.println(">> "+isodate);
	    date = parse(isodate);
	    System.out.println(">> "+date.toString()+" ["+date.getTime()+"]");
	} catch (InvalidDateException ex) {
	    System.err.println(isodate+" is invalid");
	    System.err.println(ex.getMessage());
	}
	System.out.println("----------------------------------");
    }

    public static void main(String args[]) {
	test("1997-07-16T19:20:30.45-02:00");
	test("1997-07-16T19:20:30+01:00");
	test("1997-07-16T19:20:30+01:00");
	test("1997-07-16T19:20");
	test("1997-07-16");
	test("1997-07");
	test("1997");
	test(new Date());
    }
    
}
