using GostCryptography.Asn1.Ber;
using GostCryptography.Properties;

namespace GostCryptography.Asn1.Gost.Gost_28147_89
{
    public sealed class Gost_28147_89_KeyWrapParams : Asn1Type
    {
        public Asn1ObjectIdentifier EncryptionParamSet { get; set; }

        public Asn1OctetString Ukm { get; set; }

        public override void Decode(Asn1BerDecodeBuffer buffer, bool explicitTagging, int implicitLength)
        {
            var elemLength = explicitTagging ? MatchTag(buffer, Asn1Tag.Sequence) : implicitLength;

            EncryptionParamSet = null;
            Ukm = null;

            var context = new Asn1BerDecodeContext(buffer, elemLength);
            var parsedLen = new IntHolder();

            if (!context.MatchElemTag(0, 0, ObjectIdentifierTypeCode, parsedLen, false))
            {
                throw ExceptionUtility.CryptographicException(Resources.Asn1MissingRequiredException, buffer.ByteCount);
            }

            EncryptionParamSet = new Asn1ObjectIdentifier();
            EncryptionParamSet.Decode(buffer, true, parsedLen.Value);

            if (context.MatchElemTag(0, 0, OctetStringTypeCode, parsedLen, false))
            {
                Ukm = new Asn1OctetString();
                Ukm.Decode(buffer, true, parsedLen.Value);

                if (Ukm.Length != 8)
                {
                    throw ExceptionUtility.CryptographicException(Resources.Asn1ConsVioException, nameof(Ukm.Length), Ukm.Length);
                }
            }
        }

        public override int Encode(Asn1BerEncodeBuffer buffer, bool explicitTagging)
        {
            var len = 0;

            if (Ukm != null)
            {
                if (Ukm.Length != 8)
                {
                    throw ExceptionUtility.CryptographicException(Resources.Asn1ConsVioException, nameof(Ukm.Length), Ukm.Length);
                }

                len += Ukm.Encode(buffer, true);
            }

            len += EncryptionParamSet.Encode(buffer, true);

            if (explicitTagging)
            {
                len += buffer.EncodeTagAndLength(Asn1Tag.Sequence, len);
            }

            return len;
        }
    }
}
