using System;

namespace Org.BouncyCastle.Asn1.X509
{
    public class Time
        : Asn1Encodable, IAsn1Choice
    {
        internal Asn1Object time;

		public static Time GetInstance(
            Asn1TaggedObject	obj,
            bool				explicitly)
        {
            return GetInstance(obj.GetObject());
        }

		public Time(
            Asn1Object time)
        {
			if (time == null)
				throw new ArgumentNullException("time");

			if (!(time is DerUtcTime) && !(time is DerGeneralizedTime))
            {
                throw new ArgumentException("unknown object passed to Time");
            }

			this.time = time;
        }

		/**
         * creates a time object from a given date - if the date is between 1950
         * and 2049 a UTCTime object is Generated, otherwise a GeneralizedTime
         * is used.
         */
        public Time(
            DateTime date)
        {
            string d = date.ToString("yyyyMMddHHmmss") + "Z";

			int year = Int32.Parse(d.Substring(0, 4));

			if (year < 1950 || year > 2049)
            {
                time = new DerGeneralizedTime(d);
            }
            else
            {
                time = new DerUtcTime(d.Substring(2));
            }
        }

		public static Time GetInstance(
            object obj)
        {
            if (obj == null || obj is Time)
                return (Time) obj;

			if (obj is DerUtcTime)
                return new Time((DerUtcTime) obj);

			if (obj is DerGeneralizedTime)
                return new Time((DerGeneralizedTime) obj);

			throw new ArgumentException("unknown object in factory: " + obj.GetType().Name, "obj");
        }

		public string GetTime()
        {
            if (time is DerUtcTime)
            {
                return ((DerUtcTime) time).AdjustedTimeString;
            }

			return ((DerGeneralizedTime) time).GetTime();
        }

		/// <summary>
        /// Return our time as DateTime.
        /// </summary>
        /// <returns>A date time.</returns>
        public DateTime ToDateTime()
        {
			try
			{
				if (time is DerUtcTime)
				{
					return ((DerUtcTime)time).ToAdjustedDateTime();
				}
				else
				{
					return ((DerGeneralizedTime)time).ToDateTime();
				}
			}
			catch (FormatException e)
			{
				// this should never happen
				throw new InvalidOperationException("invalid date string: " + e.Message);
			}
        }

		/**
         * Produce an object suitable for an Asn1OutputStream.
         * <pre>
         * Time ::= CHOICE {
         *             utcTime        UTCTime,
         *             generalTime    GeneralizedTime }
         * </pre>
         */
        public override Asn1Object ToAsn1Object()
        {
            return time;
        }

		public override string ToString()
		{
			return GetTime();
		}
	}
}
