using System.Collections;
using System.IO;

namespace Org.BouncyCastle.Asn1
{
    public class DerSequence
        : Asn1Sequence
    {
		public static readonly DerSequence Empty = new DerSequence();

		public static DerSequence FromVector(
			Asn1EncodableVector v)
		{
			return v.Count < 1 ? Empty : new DerSequence(v);
		}

		/**
         * create an empty sequence
         */
        public DerSequence()
			: base(0)
        {
        }

		/**
         * create a sequence containing one object
         */
        public DerSequence(
            Asn1Encodable obj)
			: base(1)
        {
            AddObject(obj);
        }

		public DerSequence(
			params Asn1Encodable[] v)
			: base(v.Length)
		{
			foreach (Asn1Encodable ae in v)
			{
				AddObject(ae);
			}
		}

		/**
         * create a sequence containing a vector of objects.
         */
        public DerSequence(
            Asn1EncodableVector v)
			: base(v.Count)
        {
			foreach (Asn1Encodable ae in v)
			{
				AddObject(ae);
			}
        }

		/*
         * A note on the implementation:
         * <p>
         * As Der requires the constructed, definite-length model to
         * be used for structured types, this varies slightly from the
         * ASN.1 descriptions given. Rather than just outputing Sequence,
         * we also have to specify Constructed, and the objects length.
         */
        internal override void Encode(
            DerOutputStream derOut)
        {
            MemoryStream bOut = new MemoryStream();
            DerOutputStream dOut = new DerOutputStream(bOut);

			foreach (Asn1Encodable obj in this)
			{
				dOut.WriteObject(obj);
            }

			dOut.Close();

			byte[] bytes = bOut.ToArray();

			derOut.WriteEncoded(Asn1Tags.Sequence | Asn1Tags.Constructed, bytes);
        }
    }
}
