// JulianCalendar.cs
//
// (C) Ulrich Kunitz 2002
//

namespace System.Globalization {

using System;

/// <summary>
/// This is the Julian calendar.
/// </summary>
/// <remarks>
/// <para>The Julian calendar supports only the Common Era from
/// January 1, 1 (Gregorian) to December 31, 9999 (Gregorian).
/// </para>
/// <para>The implementation uses the
/// <see cref="N:CalendricalCalculations"/> namespace.
/// </para>
/// </remarks>
[Serializable]
public class JulianCalendar : Calendar {
	/// <summary>
	/// Default constructor.
	/// </summary>
	public JulianCalendar() {
		M_AbbrEraNames = new string[] {"C.E."};
		M_EraNames = new string[] {"Common Era"};
		if (M_TwoDigitYearMax == 99)
			M_TwoDigitYearMax = 2029;
	}
		
	/// <summary>
	/// The era number for the Common Era (C.E.) or Anno Domini (A.D.)
	/// respective.
	/// </summary>
	public const int JulianEra = 1;

	/// <value>Overridden. Gives the eras supported by the Julian
	/// calendar as an array of integers.
	/// </value>
	public override int[] Eras {
		get {
			return new int[] { JulianEra }; 
		}
	}

	/// <summary>
	/// A protected method checking the era number.
	/// </summary>
	/// <param name="era">The era number.</param>
	/// <exception name="T:System.ArgumentException">
	/// The exception is thrown if the era is not equal
	/// <see cref="M:JulianEra"/>.
	/// </exception>
	protected void M_CheckEra(ref int era) {
		if (era == CurrentEra)
			era = JulianEra;
		if (era != JulianEra)
			throw new ArgumentException("Era value was not valid.");
	}

	/// <summary>
	/// A protected method checking calendar year and the era number.
	/// </summary>
	/// <param name="year">An integer representing the calendar year.
	/// </param>
	/// <param name="era">The era number.</param>
	/// <exception cref="T:System.ArgumentException">
	/// The exception is thrown if the era is not equal
	/// <see cref="M:JulianEra"/>.
	/// </exception>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown if the calendar year is outside of
	/// the allowed range.
	/// </exception>
	protected override void M_CheckYE(int year, ref int era) {
		M_CheckEra(ref era);
		M_ArgumentInRange("year", year, 1, 9999);
	}

	/// <summary>
	/// A protected method checking the calendar year, month, and
	/// era number.
	/// </summary>
	/// <param name="year">An integer representing the calendar year.
	/// </param>
	/// <param name="month">An integer giving the calendar month.
	/// </param>
	/// <param name="era">The era number.</param>
	/// <exception cref="T:System.ArgumentException">
	/// The exception is thrown if the era is not equal
	/// <see cref="M:JulianEra"/>.
	/// </exception>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown if the calendar year or month is
	/// outside of the allowed range.
	/// </exception>
	protected void M_CheckYME(int year, int month, ref int era) {
		M_CheckYE(year, ref era);
		if (month < 1 || month > 12)
			throw new ArgumentOutOfRangeException("month",
				"Month must be between one and twelve.");
	}

	/// <summary>
	/// A protected method checking the calendar day, month, and year
	/// and the era number.
	/// </summary>
	/// <param name="year">An integer representing the calendar year.
	/// </param>
	/// <param name="month">An integer giving the calendar month.
	/// </param>
	/// <param name="day">An integer giving the calendar day.
	/// </param>
	/// <param name="era">The era number.</param>
	/// <exception cref="T:System.ArgumentException">
	/// The exception is thrown if the era is not equal
	/// <see cref="M:JulianEra"/>.
	/// </exception>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown if the calendar year, month, or day is
	/// outside of the allowed range.
	/// </exception>
	protected void M_CheckYMDE(int year, int month, int day, ref int era)
	{
		M_CheckYME(year, month, ref era);
		M_ArgumentInRange("day", day, 1,
			GetDaysInMonth(year, month, era));
		if (year == 9999 && ((month == 10 && day > 19) || month > 10))
			throw new ArgumentOutOfRangeException(
				"The maximum Julian date is 19. 10. 9999.");
	}

	/// <summary>
	/// Overridden. Adds months to a given date.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> to which to add
	/// months.
	/// </param>
	/// <param name="months">The number of months to add.</param>
	/// <returns>A new <see cref="T:System.DateTime"/> value, that
	/// results from adding <paramref name="months"/> to the specified
	/// DateTime.</returns>
	public override DateTime AddMonths(DateTime time, int months) {
		int rd = CCFixed.FromDateTime(time);
		int day, month, year;
		CCJulianCalendar.dmy_from_fixed(
			out day, out month, out year, rd);
		month += months;
		rd = CCJulianCalendar.fixed_from_dmy(day, month, year);
		DateTime t = CCFixed.ToDateTime(rd);
		return t.Add(time.TimeOfDay);
	}

	/// <summary>
	/// Overridden. Adds years to a given date.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> to which to add
	/// years.
	/// </param>
	/// <param name="years">The number of years to add.</param>
	/// <returns>A new <see cref="T:System.DateTime"/> value, that
	/// results from adding <paramref name="years"/> to the specified
	/// DateTime.</returns>
	public override DateTime AddYears(DateTime time, int years) {
		int rd = CCFixed.FromDateTime(time);
		int day, month, year;
		CCJulianCalendar.dmy_from_fixed(
			out day, out month, out year, rd);
		year += years;
		rd = CCJulianCalendar.fixed_from_dmy(day, month, year);
		DateTime t = CCFixed.ToDateTime(rd);
		return t.Add(time.TimeOfDay);
	}
		
	/// <summary>
	/// Overridden. Gets the day of the month from
	/// <paramref name="time"/>.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> that specifies a
	/// date.
	/// </param>
	/// <returns>An integer giving the day of months, starting with 1.
	/// </returns>
	public override int GetDayOfMonth(DateTime time) {
		int rd = CCFixed.FromDateTime(time);
		return CCJulianCalendar.day_from_fixed(rd);
	}

	/// <summary>
	/// Overridden. Gets the day of the week from the specified date.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> that specifies a
	/// date.
	/// </param>
	/// <returns>An integer giving the day of months, starting with 1.
	/// </returns>
	public override DayOfWeek GetDayOfWeek(DateTime time) {
		int rd = CCFixed.FromDateTime(time);
		return (DayOfWeek)CCFixed.day_of_week(rd);
	}

	/// <summary>
	/// Overridden. Gives the number of the day in the year.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> that specifies a
	/// date.
	/// </param>
	/// <returns>An integer representing the day of the year,
	/// starting with 1.</returns>
	public override int GetDayOfYear(DateTime time) {
		int rd = CCFixed.FromDateTime(time);
		int year = CCJulianCalendar.year_from_fixed(rd);
		int rd1_1 = CCJulianCalendar.fixed_from_dmy(1, 1, year);
		return rd - rd1_1 + 1;
	}

	/// <summary>
	/// Overridden. Gives the number of days in the specified month
	/// of the given year and era.
	/// </summary>
	/// <param name="year">An integer that gives the year.
	/// </param>
	/// <param name="month">An integer that gives the month, starting
	/// with 1.</param>
	/// <param name="era">An intger that gives the era of the specified
	/// year.</param>
	/// <returns>An integer that gives the number of days of the
	/// specified month.</returns>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown, if <paramref name="month"/>,
	/// <paramref name="year"/> ,or <paramref name="era"/> is outside
	/// the allowed range.
	/// </exception>
	public override int GetDaysInMonth(int year, int month, int era) {
		M_CheckYME(year, month, ref era);
		int rd1 = CCJulianCalendar.fixed_from_dmy(1, month, year);
		int rd2 = CCJulianCalendar.fixed_from_dmy(1, month+1, year);
		return rd2 - rd1;
	}

	/// <summary>
	/// Overridden. Gives the number of days of the specified
	/// year of the given era. 
	/// </summary>
	/// <param name="year">An integer that specifies the year. 
	/// </param>
	/// <param name="era">An ineger that specifies the era.
	/// </param>
	/// <returns>An integer that gives the number of days of the
	/// specified year.</returns>
	/// <exception cref="T:System.ArgumentOutOfRangeExceiption">
	/// The exception is thrown, if
	/// <paramref name="year"/> is outside the allowed range.
	/// </exception>
	public override int GetDaysInYear(int year, int era) {
		M_CheckYE(year, ref era);
		int rd1 = CCJulianCalendar.fixed_from_dmy(1, 1, year);
		int rd2 = CCJulianCalendar.fixed_from_dmy(1, 1, year+1);
		return rd2 - rd1;
	}
		

	/// <summary>
	/// Overridden. Gives the era of the specified date.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> that specifies a
	/// date.
	/// </param>
	/// <returns>An integer representing the era of the calendar.
	/// </returns>
	public override int GetEra(DateTime time) {
		// should change, if more than one era is supported
		return JulianEra;
	}

	/// <summary>
	/// Overridden. Gives the number of the month of the specified
	/// date.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> that specifies a
	/// date.
	/// </param>
	/// <returns>An integer representing the month, 
	/// starting with 1.</returns>
	public override int GetMonth(DateTime time) {
		int rd = CCFixed.FromDateTime(time);
		return CCJulianCalendar.month_from_fixed(rd);
	}

	/// <summary>
	/// Overridden. Gives the number of months in the specified year 
	/// and era.
	/// </summary>
	/// <param name="year">An integer that specifies the year.
	/// </param>
	/// <param name="era">An integer that specifies the era.
	/// </param>
	/// <returns>An integer that gives the number of the months in the
	/// specified year.</returns>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown, if the year or the era are not valid.
	/// </exception>
	public override int GetMonthsInYear(int year, int era) {
		M_CheckYE(year, ref era);
		return 12;
	}

	/// <summary>
	/// Overridden. Gives the number of the year of the specified
	/// date.
	/// </summary>
	/// <param name="time">The
	/// <see cref="T:System.DateTime"/> that specifies a
	/// date.
	/// </param>
	/// <returns>An integer representing the year, 
	/// starting with 1.</returns>
	public override int GetYear(DateTime time) {
		int rd = CCFixed.FromDateTime(time);
		return CCJulianCalendar.year_from_fixed(rd);
	}

	/// <summary>
	/// Overridden. Tells whether the given day 
	/// is a leap day.
	/// </summary>
	/// <param name="year">An integer that specifies the year in the
	/// given era.
	/// </param>
	/// <param name="month">An integer that specifies the month.
	/// </param>
	/// <param name="day">An integer that specifies the day.
	/// </param>
	/// <param name="era">An integer that specifies the era.
	/// </param>
	/// <returns>A boolean that tells whether the given day is a leap
	/// day.
	/// </returns>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown, if the year, month, day, or era is not
	/// valid.
	/// </exception>
	public override bool IsLeapDay(int year, int month, int day, int era)
	{
		M_CheckYMDE(year, month, day, ref era);
		return IsLeapYear(year) && month == 2 && day == 29;
	}

	/// <summary>
	/// Overridden. Tells whether the given month 
	/// is a leap month.
	/// </summary>
	/// <param name="year">An integer that specifies the year in the
	/// given era.
	/// </param>
	/// <param name="month">An integer that specifies the month.
	/// </param>
	/// <param name="era">An integer that specifies the era.
	/// </param>
	/// <returns>A boolean that tells whether the given month is a leap
	/// month.
	/// </returns>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown, if the year, month, or era is not
	/// valid.
	/// </exception>
	public override bool IsLeapMonth(int year, int month, int era) {
		M_CheckYME(year, month, ref era);
		return false;
	}

	/// <summary>
	/// Overridden. Tells whether the given year
	/// is a leap year.
	/// </summary>
	/// <param name="year">An integer that specifies the year in the
	/// given era.
	/// </param>
	/// <param name="era">An integer that specifies the era.
	/// </param>
	/// <returns>A boolean that tells whether the given year is a leap
	/// year.
	/// </returns>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown, if the year or era is not
	/// valid.
	/// </exception>
	public override bool IsLeapYear(int year, int era) {
		M_CheckYE(year, ref era);
		return CCJulianCalendar.is_leap_year(year);
	}

	/// <summary>
	/// Overridden. Creates the
	/// <see cref="T:System.DateTime"/> from the parameters.
	/// </summary>
	/// <param name="year">An integer that gives the year in the
	/// <paramref name="era"/>.
	/// </param>
	/// <param name="month">An integer that specifies the month.
	/// </param>
	/// <param name="day">An integer that specifies the day.
	/// </param>
	/// <param name="hour">An integer that specifies the hour.
	/// </param>
	/// <param name="minute">An integer that specifies the minute.
	/// </param>
	/// <param name="second">An integer that gives the second.
	/// </param>
	/// <param name="milliseconds">An integer that gives the
	/// milliseconds.
	/// </param>
	/// <param name="era">An integer that specifies the era.
	/// </param>
	/// <returns>
	/// <see cref="T:system.DateTime"/> representig the date and time.
	/// </returns>
	/// <exception cref="T:System.ArgumentOutOfRangeException">
	/// The exception is thrown, if at least one of the parameters
	/// is out of range.
	/// </exception>
	public override DateTime ToDateTime(int year, int month, int day,
		int hour, int minute, int second, int milliseconds,
		int era)
	{
		M_CheckYMDE(year, month, day, ref era);
		M_CheckHMSM(hour, minute, second, milliseconds);
		int rd = CCJulianCalendar.fixed_from_dmy(day, month, year);
		return CCFixed.ToDateTime(rd,
			hour, minute, second, milliseconds);
	}
} // class JulianCalendar
	
} // namespace System.Globalization