/*
 * Copyright (C) The Apache Software Foundation. All rights reserved.
 *
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.txt file.
 */

package org.apache.log4j.helpers;

import java.util.Date;
import java.util.Calendar;
import java.util.TimeZone;
import java.util.Locale;
import java.text.FieldPosition;
import java.text.ParsePosition;
import java.text.DateFormat;
import java.text.DecimalFormat;
import java.text.NumberFormat;


/**
   Formats a {@link Date} in the format "HH:mm:ssdSSS", where the decimal
   separator, 'd', is locale specific.<br>
   For example, "15:49:37,459" for most European and East European countries,
   or "15:49:37.459" for most of the Americas, most of the Middle East and
   most of East Asia.

   @author Ceki G&uuml;lc&uuml;
   @author Andrew Vajoczki    

   @since 0.7.5
*/
public class AbsoluteTimeDateFormat extends DateFormat {

  /**
     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";

  /*
   * Set default decimal separator.  One or the other has to be chosen, so
   * for historical purposes we choose the comma.
   */
  private char decimalSeparator = ',';

  public
  AbsoluteTimeDateFormat() {
    setCalendar(Calendar.getInstance());
    setDecimalSeparator(Locale.getDefault());
  }

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

  public
  AbsoluteTimeDateFormat(Locale locale) {
    setCalendar(Calendar.getInstance(locale));
    setDecimalSeparator(locale);
  }

  public
  AbsoluteTimeDateFormat(TimeZone timeZone, Locale locale) {
    setCalendar(Calendar.getInstance(timeZone, locale));
    setDecimalSeparator(locale);
  }

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

  /**
     <p>
     Appends to <code>sbuf</code> the millisecond timestamp in <code>Locale</code>
     specific format.
     </p>
     <p>
     For example, "HH:mm:ss,SSS" (e.g. "15:49:37,459") for most European
     and East European countries, or "HH:mm:ss.SSS" (e.g. "15:49:37.459")
     for most of the Americas, most of the Middle East and most of East Asia.
     </p>

     @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) {
      sbuf.append(previousTimeWithoutMillis);
    }
    else {
      // 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(decimalSeparator);

      // store the time string for next time to avoid recomputation
      sbuf.getChars(start, sbuf.length(), previousTimeWithoutMillis, 0);

      previousTime = now - millis;
    }

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

    sbuf.append(millis);
    return sbuf;
  }

  /**
     Sets the decimalSeparator used for displaying Millisecond timestamps.
   */
  private
  void setDecimalSeparator(Locale locale) {
  	NumberFormat nf = NumberFormat.getInstance(locale);
  	if (nf instanceof DecimalFormat) {
      decimalSeparator =
        ((DecimalFormat)nf).getDecimalFormatSymbols().getDecimalSeparator();
  	}
  }

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