{filelink=6273}

//revised from skaringa

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

/**
 * Format and parse an ISO 8601 DateTimeFormat used in XML documents.
 * This lexical representation is the ISO 8601
 * extended format CCYY-MM-DDThh:mm:ss
 * where "CC" represents the century, "YY" the year, "MM" the month
 * and "DD" the day,
 * preceded by an optional leading "-" sign to indicate a negative number.
 * If the sign is omitted, "+" is assumed.
 * The letter "T" is the date/time separator
 * and "hh", "mm", "ss" represent hour, minute and second respectively.
 * This representation may be immediately followed by a "Z" to indicate
 * Coordinated Universal Time (UTC) or, to indicate the time zone,
 * i.e. the difference between the local time and Coordinated Universal Time,
 * immediately followed by a sign, + or -,
 * followed by the difference from UTC represented as hh:mm.
 *
 */
public class ISO8601DateTimeFormat extends DateFormat {

  /**
   * Construct a new ISO8601DateTimeFormat using the default time zone.
   *
   */
  public ISO8601DateTimeFormat() {
    setCalendar(Calendar.getInstance());
  }

  /**
   * Construct a new ISO8601DateTimeFormat using a specific time zone.
   * @param tz The time zone used to format and parse the date.
   */
  public ISO8601DateTimeFormat(TimeZone tz) {
    setCalendar(Calendar.getInstance(tz));
  }

  /**
   * @see DateFormat#parse(String, ParsePosition)
   */
  public Date parse(String text, ParsePosition pos) {

    int i = pos.getIndex();

    try {
      int year = Integer.valueOf(text.substring(i, i + 4)).intValue();
      i += 4;

      if (text.charAt(i) != '-') {
        throw new NumberFormatException();
      }
      i++;

      int month = Integer.valueOf(text.substring(i, i + 2)).intValue() - 1;
      i += 2;

      if (text.charAt(i) != '-') {
        throw new NumberFormatException();
      }
      i++;

      int day = Integer.valueOf(text.substring(i, i + 2)).intValue();
      i += 2;

      if (text.charAt(i) != 'T') {
        throw new NumberFormatException();
      }
      i++;

      int hour = Integer.valueOf(text.substring(i, i + 2)).intValue();
      i += 2;

      if (text.charAt(i) != ':') {
        throw new NumberFormatException();
      }
      i++;

      int mins = Integer.valueOf(text.substring(i, i + 2)).intValue();
      i += 2;

      int secs = 0;
      if (i < text.length() && text.charAt(i) == ':') {
        // handle seconds flexible
        i++;

        secs = Integer.valueOf(text.substring(i, i + 2)).intValue();
        i += 2;
      }

      calendar.set(year, month, day, hour, mins, secs);
      calendar.set(Calendar.MILLISECOND, 0); // no parts of a second

      i = parseTZ(i, text);

    }
    catch (NumberFormatException ex) {
      pos.setErrorIndex(i);
      return null;
    }
    catch (IndexOutOfBoundsException ex) {
      pos.setErrorIndex(i);
      return null;
    }
    finally {
      pos.setIndex(i);
    }

    return calendar.getTime();
  }

  /**
   * Parse the time zone.
   * @param i The position to start parsing.
   * @param text The text to parse.
   * @return The position after parsing has finished.
   */
  protected final int parseTZ(int i, String text) {
    if (i < text.length()) {
      // check and handle the zone/dst offset
      int offset = 0;
      if (text.charAt(i) == 'Z') {
        offset = 0;
        i++;
      }
      else {
        int sign = 1;
        if (text.charAt(i) == '-') {
          sign = -1;
        }
        else if (text.charAt(i) != '+') {
          throw new NumberFormatException();
        }
        i++;

        int offsetHour = Integer.valueOf(text.substring(i, i + 2)).intValue();
        i += 2;

        if (text.charAt(i) != ':') {
          throw new NumberFormatException();
        }
        i++;

        int offsetMin = Integer.valueOf(text.substring(i, i + 2)).intValue();
        i += 2;
        offset = ((offsetHour * 60) + offsetMin) * 60000 * sign;
      }
      int offsetCal =
        calendar.get(Calendar.ZONE_OFFSET) + calendar.get(Calendar.DST_OFFSET);

      calendar.add(Calendar.MILLISECOND, offsetCal - offset);
    }
    return i;
  }

  /**
   * @see DateFormat#format(Date, StringBuffer, FieldPosition)
   */
  public StringBuffer format(
    Date date,
    StringBuffer sbuf,
    FieldPosition fieldPosition) {

    calendar.setTime(date);

    writeCCYYMM(sbuf);

    sbuf.append('T');

    writehhmmss(sbuf);

    writeTZ(sbuf);

    return sbuf;
  }

  /**
   * Write the time zone string.
   * @param sbuf The buffer to append the time zone.
   */
  protected final void writeTZ(StringBuffer sbuf) {
    int offset =
      calendar.get(Calendar.ZONE_OFFSET) + calendar.get(Calendar.DST_OFFSET);
    if (offset == 0) {
      sbuf.append('Z');
    }
    else {
      int offsetHour = offset / 3600000;
      int offsetMin = (offset % 3600000) / 60000;
      if (offset >= 0) {
        sbuf.append('+');
      }
      else {
        sbuf.append('-');
        offsetHour = 0 - offsetHour;
        offsetMin = 0 - offsetMin;
      }
      appendInt(sbuf, offsetHour, 2);
      sbuf.append(':');
      appendInt(sbuf, offsetMin, 2);
    }
  }

  /**
   * Write hour, minutes, and seconds.
   * @param sbuf The buffer to append the string.
   */
  protected final void writehhmmss(StringBuffer sbuf) {
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    appendInt(sbuf, hour, 2);
    sbuf.append(':');

    int mins = calendar.get(Calendar.MINUTE);
    appendInt(sbuf, mins, 2);
    sbuf.append(':');

    int secs = calendar.get(Calendar.SECOND);
    appendInt(sbuf, secs, 2);
  }

  /**
   * Write century, year, and months.
   * @param sbuf The buffer to append the string.
   */
  protected final void writeCCYYMM(StringBuffer sbuf) {
    int year = calendar.get(Calendar.YEAR);
    appendInt(sbuf, year, 4);

    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);
    appendInt(sbuf, day, 2);
  }

  /**
   * Write an integer value with leading zeros.
   * @param buf The buffer to append the string.
   * @param value The value to write.
   * @param length The length of the string to write.
   */
  protected final void appendInt(StringBuffer buf, int value, int length) {
    int len1 = buf.length();
    buf.append(value);
    int len2 = buf.length();
    for (int i = len2; i < len1 + length; ++i) {
      buf.insert(len1, '0');
    }
  }
}