RFC822.java

package org.caudexorigo.time;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.regex.Pattern;

public class RFC822
{
	private static final TimeZone gmt_timeZone = TimeZone.getTimeZone("GMT");

	private static final Pattern rfc_part_splitter = Pattern.compile(",|\\s");
	private static final Pattern rfc_hour_splitter = Pattern.compile(":");

	private static final ConcurrentMap<String, Integer> rfc_month;
	private static final ConcurrentMap<String, Integer> rfc_dow;

	static
	{
		rfc_month = new ConcurrentHashMap<String, Integer>();
		rfc_month.put("Jan", 0);
		rfc_month.put("Feb", 1);
		rfc_month.put("Mar", 2);
		rfc_month.put("Apr", 3);
		rfc_month.put("May", 4);
		rfc_month.put("Jun", 5);
		rfc_month.put("Jul", 6);
		rfc_month.put("Aug", 7);
		rfc_month.put("Sep", 8);
		rfc_month.put("Oct", 9);
		rfc_month.put("Nov", 10);
		rfc_month.put("Dec", 11);

		rfc_dow = new ConcurrentHashMap<String, Integer>();
		rfc_dow.put("Sun", 1);
		rfc_dow.put("Mon", 2);
		rfc_dow.put("Tue", 3);
		rfc_dow.put("Wed", 4);
		rfc_dow.put("Thu", 5);
		rfc_dow.put("Fri", 6);
		rfc_dow.put("Sat", 7);
	}

	private static final ThreadLocal<SimpleDateFormat> rfc_sdf = new ThreadLocal<SimpleDateFormat>()
	{
		@Override
		protected SimpleDateFormat initialValue()
		{
			final String _rfc_pattern = "EEE', 'dd' 'MMM' 'yyyy' 'HH:mm:ss' 'zzz";
			SimpleDateFormat _rfc_format;
			_rfc_format = new SimpleDateFormat(_rfc_pattern, Locale.US);
			_rfc_format.setTimeZone(gmt_timeZone);
			return _rfc_format;
		}
	};

	public static String toISO(String rfc_date) throws ParseException
	{
		Date date = parse(rfc_date);
		return ISO8601.format(date);
	}

	public static Date parse(String rfc_date)
	{
		Calendar calendar = new GregorianCalendar(TimeZone.getTimeZone("UTC"), Locale.US);
		calendar.clear();
		String[] parts = rfc_part_splitter.split(rfc_date);

		// System.out.println(Arrays.toString(parts));

		int month_pos = 0;
		boolean is_month_set = false;

		int dow_pos = 0;
		boolean is_dow_set = false;

		int hour_pos = 0;
		boolean is_hour_set = false;

		for (int i = 0; i < parts.length; i++)
		{
			String part = parts[i];

			if (!is_month_set)
			{
				Integer month_part = rfc_month.get(part);
				if (month_part != null)
				{
					calendar.set(Calendar.MONTH, month_part.intValue());
					month_pos = i;
					is_month_set = true;
				}
			}

			if (!is_dow_set)
			{
				Integer dow_part = rfc_dow.get(part);
				if (dow_part != null)
				{
					calendar.set(Calendar.DAY_OF_WEEK, dow_part.intValue());
					dow_pos = i;
					is_dow_set = true;
				}
			}

			if (!is_hour_set)
			{
				if (part.indexOf(":") > -1)
				{
					String[] hour_parts = rfc_hour_splitter.split(part);

					if (hour_parts.length >= 2 && hour_parts.length <= 3)
					{
						calendar.set(Calendar.HOUR_OF_DAY, Integer.parseInt(hour_parts[0]));
						calendar.set(Calendar.MINUTE, Integer.parseInt(hour_parts[1]));

						if (hour_parts.length == 3)
						{
							calendar.set(Calendar.SECOND, Integer.parseInt(hour_parts[2]));
						}

					}
					else
					{
						throw new RuntimeException("Error parsing date value, illegal hour format: '" + part + "'");
					}
					is_hour_set = true;
					hour_pos = i;
				}
			}
		}

		int day_pos = month_pos - 1;
		int year_pos = month_pos + 1;

		String timeZone = parts[parts.length - 1];

		calendar.set(Calendar.DAY_OF_MONTH, Integer.parseInt(parts[day_pos]));
		calendar.set(Calendar.YEAR, Integer.parseInt(parts[year_pos]));

		if (timeZone.startsWith("+"))
		{
			int offset = Integer.parseInt(timeZone.substring(1)) * 60000;

			// System.out.println("RfcTest.parseRfcDate.offset: " + offset);

			calendar.set(Calendar.ZONE_OFFSET, offset);
		}
		else if (timeZone.startsWith("-"))
		{
			int offset = -1 * Integer.parseInt(timeZone.substring(1)) * 60000;

			// System.out.println("RfcTest.parseRfcDate.offset: " + offset);

			calendar.set(Calendar.ZONE_OFFSET, offset);
		}
		else
		{
			// System.out.println("RfcTest.parseRfcDate.timezone: " + timeZone);
			calendar.setTimeZone(TimeZone.getTimeZone(timeZone));
		}

		return calendar.getTime();
	}

	public static String format(Date date) throws ParseException
	{
		return rfc_sdf.get().format(date);
	}
}