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

namespace GostCryptography.Asn1.Gost.Gost_R3410
{
    /// <summary>
    /// Параметры ключа цифровой подписи ГОСТ Р 34.10
    /// </summary>
    public abstract class Gost_R3410_KeyExchangeParams
    {
        protected Gost_R3410_KeyExchangeParams()
        {
        }

        protected Gost_R3410_KeyExchangeParams(Gost_R3410_KeyExchangeParams other)
        {
            DigestParamSet = other.DigestParamSet;
            PublicKeyParamSet = other.PublicKeyParamSet;
            EncryptionParamSet = other.EncryptionParamSet;
            PublicKey = other.PublicKey;
            PrivateKey = other.PrivateKey;
        }

        /// <summary>
        /// Идентификатор OID параметров хэширования
        /// </summary>
        public string DigestParamSet { get; set; }

        /// <summary>
        /// Идентификатор OID параметров открытого ключа
        /// </summary>
        public string PublicKeyParamSet { get; set; }

        /// <summary>
        /// Идентификатор OID параметров шифрования
        /// </summary>
        public string EncryptionParamSet { get; set; }

        /// <summary>
        /// Открытый ключ
        /// </summary>
        public byte[] PublicKey { get; set; }

        /// <summary>
        /// Закрытый ключ
        /// </summary>
        public byte[] PrivateKey { get; set; }

        public abstract Gost_R3410_KeyExchangeParams Clone();

        protected abstract Gost_R3410_PublicKey CreatePublicKey();

        protected abstract Gost_R3410_PublicKeyParams CreatePublicKeyParams();

        /// <summary>
        /// Расшифровать параметры
        /// </summary>
        public void DecodeParameters(byte[] data)
        {
            if (data == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(data));
            }

            try
            {
                var asnDecoder = new Asn1BerDecodeBuffer(data);
                var publicKeyParams = CreatePublicKeyParams();
                publicKeyParams.Decode(asnDecoder);

                PublicKeyParamSet = publicKeyParams.PublicKeyParamSet.Oid.Value;
                DigestParamSet = publicKeyParams.DigestParamSet?.Oid.Value;
                EncryptionParamSet = publicKeyParams.EncryptionParamSet?.Oid.Value;
            }
            catch (Exception exception)
            {
                throw ExceptionUtility.CryptographicException(exception, Resources.Asn1DecodeError, nameof(Gost_R3410_PublicKeyParams));
            }
        }

        /// <summary>
        /// Зашифровать параметры
        /// </summary>
        public byte[] EncodeParameters()
        {
            byte[] data;

            try
            {
                var publicKeyParams = CreatePublicKeyParams();
                publicKeyParams.PublicKeyParamSet = Asn1ObjectIdentifier.FromString(PublicKeyParamSet);
                publicKeyParams.DigestParamSet = Asn1ObjectIdentifier.FromString(DigestParamSet);
                publicKeyParams.EncryptionParamSet = Asn1ObjectIdentifier.FromString(EncryptionParamSet);

                var asnEncoder = new Asn1BerEncodeBuffer();
                publicKeyParams.Encode(asnEncoder);
                data = asnEncoder.MsgCopy;
            }
            catch (Exception exception)
            {
                throw ExceptionUtility.CryptographicException(exception, Resources.Asn1EncodeError, nameof(Gost_R3410_PublicKeyParams));
            }

            return data;
        }


        /// <summary>
        /// Расшифровать публичный ключ
        /// </summary>
        public void DecodePublicKey(byte[] data)
        {
            if (data == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(data));
            }

            try
            {
                var asnDecoder = new Asn1BerDecodeBuffer(data);
                var publicKey = CreatePublicKey();
                publicKey.Decode(asnDecoder);

                PublicKey = publicKey.Value;
            }
            catch (Exception exception)
            {
                throw ExceptionUtility.CryptographicException(exception, Resources.Asn1DecodeError, nameof(Gost_R3410_PublicKey));
            }
        }

        /// <summary>
        /// Зашифровать публичный ключ
        /// </summary>
        public byte[] EncodePublicKey()
        {
            byte[] data;

            try
            {
                var publicKey = CreatePublicKey();
                publicKey.Value = PublicKey;

                var asnEncoder = new Asn1BerEncodeBuffer();
                publicKey.Encode(asnEncoder);
                data = asnEncoder.MsgCopy;
            }
            catch (Exception exception)
            {
                throw ExceptionUtility.CryptographicException(exception, Resources.Asn1EncodeError, nameof(Gost_R3410_PublicKeyParams));
            }

            return data;
        }
    }
}