/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.log4j.helpers;

import java.util.Calendar;
import java.util.TimeZone;
import java.util.Date;
import java.text.FieldPosition;
import java.text.ParsePosition;

// Contributors: Arndt Schoenewald <arndt@ibm23093i821.mc.schoenewald.de>

/**
 * Formats a {@link Date} in the format "yyyy-MM-dd HH:mm:ss,SSS" for example
 * "1999-11-27 15:49:37,459".
 * 
 * <p>
 * Refer to the <a href=http://www.cl.cam.ac.uk/~mgk25/iso-time.html>summary of
 * the International Standard Date and Time Notation</a> for more information on
 * this format.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @author Andrew Vajoczki
 * 
 * @since 0.7.5
 */
public class ISO8601DateFormat extends AbsoluteTimeDateFormat {
    private static final long serialVersionUID = -759840745298755296L;

    public ISO8601DateFormat() {
    }

    public ISO8601DateFormat(TimeZone timeZone) {
	super(timeZone);
    }

    static private long lastTime;
    static private char[] lastTimeString = new char[20];

    /**
     * Appends a date in the format "YYYY-mm-dd HH:mm:ss,SSS" to <code>sbuf</code>.
     * For example: "1999-11-27 15:49:37,459".
     * 
     * @param sbuf the <code>StringBuffer</code> to write to
     */
    public StringBuffer format(Date date, StringBuffer sbuf, FieldPosition fieldPosition) {

	long now = date.getTime();
	int millis = (int) (now % 1000);

	if ((now - millis) != lastTime || lastTimeString[0] == 0) {
	    // We reach this point at most once per second
	    // across all threads instead of each time format()
	    // is called. This saves considerable CPU time.

	    calendar.setTime(date);

	    int start = sbuf.length();

	    int year = calendar.get(Calendar.YEAR);
	    sbuf.append(year);

	    String month;
	    switch (calendar.get(Calendar.MONTH)) {
	    case Calendar.JANUARY:
		month = "-01-";
		break;
	    case Calendar.FEBRUARY:
		month = "-02-";
		break;
	    case Calendar.MARCH:
		month = "-03-";
		break;
	    case Calendar.APRIL:
		month = "-04-";
		break;
	    case Calendar.MAY:
		month = "-05-";
		break;
	    case Calendar.JUNE:
		month = "-06-";
		break;
	    case Calendar.JULY:
		month = "-07-";
		break;
	    case Calendar.AUGUST:
		month = "-08-";
		break;
	    case Calendar.SEPTEMBER:
		month = "-09-";
		break;
	    case Calendar.OCTOBER:
		month = "-10-";
		break;
	    case Calendar.NOVEMBER:
		month = "-11-";
		break;
	    case Calendar.DECEMBER:
		month = "-12-";
		break;
	    default:
		month = "-NA-";
		break;
	    }
	    sbuf.append(month);

	    int day = calendar.get(Calendar.DAY_OF_MONTH);
	    if (day < 10)
		sbuf.append('0');
	    sbuf.append(day);

	    sbuf.append(' ');

	    int hour = calendar.get(Calendar.HOUR_OF_DAY);
	    if (hour < 10) {
		sbuf.append('0');
	    }
	    sbuf.append(hour);
	    sbuf.append(':');

	    int mins = calendar.get(Calendar.MINUTE);
	    if (mins < 10) {
		sbuf.append('0');
	    }
	    sbuf.append(mins);
	    sbuf.append(':');

	    int secs = calendar.get(Calendar.SECOND);
	    if (secs < 10) {
		sbuf.append('0');
	    }
	    sbuf.append(secs);

	    sbuf.append(',');

	    // store the time string for next time to avoid recomputation
	    sbuf.getChars(start, sbuf.length(), lastTimeString, 0);
	    lastTime = now - millis;
	} else {
	    sbuf.append(lastTimeString);
	}

	if (millis < 100)
	    sbuf.append('0');
	if (millis < 10)
	    sbuf.append('0');

	sbuf.append(millis);
	return sbuf;
    }

    /**
     * This method does not do anything but return <code>null</code>.
     */
    public Date parse(java.lang.String s, ParsePosition pos) {
	return null;
    }
}
