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

namespace GostCryptography.Asn1.Gost.PublicKey
{
    public sealed class SubjectPublicKeyInfo : Asn1Type
    {
        public AlgorithmIdentifier Algorithm { get; set; }

        public Asn1BitString SubjectPublicKey { get; set; }
        
        public override void Decode(Asn1BerDecodeBuffer buffer, bool explicitTagging, int implicitLength)
        {
            var elemLength = explicitTagging ? MatchTag(buffer, Asn1Tag.Sequence) : implicitLength;

            Algorithm = null;
            SubjectPublicKey = null;

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

            if (!context.MatchElemTag(0, 0x20, 0x10, parsedLen, false))
            {
                throw ExceptionUtility.CryptographicException(Resources.Asn1MissingRequiredException, buffer.ByteCount);
            }

            Algorithm = new AlgorithmIdentifier();
            Algorithm.Decode(buffer, true, parsedLen.Value);

            if (!context.MatchElemTag(0, 0, 3, parsedLen, false))
            {
                throw ExceptionUtility.CryptographicException(Resources.Asn1MissingRequiredException, buffer.ByteCount);
            }

            SubjectPublicKey = new Asn1BitString();
            SubjectPublicKey.Decode(buffer, true, parsedLen.Value);
        }

        public override int Encode(Asn1BerEncodeBuffer buffer, bool explicitTagging)
        {
            var len = 0;
            len += SubjectPublicKey.Encode(buffer, true);
            len += Algorithm.Encode(buffer, true);

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

            return len;
        }
    }
}