using System.IO;
using NBitcoin.BouncyCastle.Utilities;

namespace NBitcoin.BouncyCastle.Asn1
{
    internal 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)
        {
            // TODO Intermediate buffer could be avoided if we could calculate expected length
            var bOut = new MemoryStream();
            var dOut = new DerOutputStream(bOut);

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

            Platform.Dispose(dOut);

            byte[] bytes = bOut.ToArray();

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