/*
 * 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.Date;
import java.util.Calendar;
import java.util.TimeZone;
import java.text.FieldPosition;
import java.text.ParsePosition;
import java.text.DateFormat;

/**
 * Formats a {@link Date} in the format "HH:mm:ss,SSS" for example,
 * "15:49:37,459".
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @author Andrew Vajoczki
 * 
 * @since 0.7.5
 */
public class AbsoluteTimeDateFormat extends DateFormat {
    private static final long serialVersionUID = -388856345976723342L;

    /**
     * String constant used to specify
     * {@link org.apache.log4j.helpers.AbsoluteTimeDateFormat} in layouts. Current
     * value is <b>ABSOLUTE</b>.
     */
    public final static String ABS_TIME_DATE_FORMAT = "ABSOLUTE";

    /**
     * String constant used to specify
     * {@link org.apache.log4j.helpers.DateTimeDateFormat} in layouts. Current value
     * is <b>DATE</b>.
     */
    public final static String DATE_AND_TIME_DATE_FORMAT = "DATE";

    /**
     * String constant used to specify
     * {@link org.apache.log4j.helpers.ISO8601DateFormat} in layouts. Current value
     * is <b>ISO8601</b>.
     */
    public final static String ISO8601_DATE_FORMAT = "ISO8601";

    public AbsoluteTimeDateFormat() {
	setCalendar(Calendar.getInstance());
    }

    public AbsoluteTimeDateFormat(TimeZone timeZone) {
	setCalendar(Calendar.getInstance(timeZone));
    }

    private static long previousTime;
    private static char[] previousTimeWithoutMillis = new char[9]; // "HH:mm:ss."

    /**
     * Appends to <code>sbuf</code> the time in the format "HH:mm:ss,SSS" for
     * example, "15:49:37,459"
     * 
     * @param date          the date to format
     * @param sbuf          the string buffer to write to
     * @param fieldPosition remains untouched
     */
    public StringBuffer format(Date date, StringBuffer sbuf, FieldPosition fieldPosition) {

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

	if ((now - millis) != previousTime || previousTimeWithoutMillis[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 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(), previousTimeWithoutMillis, 0);

	    previousTime = now - millis;
	} else {
	    sbuf.append(previousTimeWithoutMillis);
	}

	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(String s, ParsePosition pos) {
	return null;
    }
}
