using GostCryptography.Asn1.Gost.Gost_28147_89;
using GostCryptography.Asn1.Gost.Gost_R3410;
using GostCryptography.Base;
using GostCryptography.Gost_28147_89;
using GostCryptography.Native;
using GostCryptography.Properties;
using System.Security;
using System.Security.Cryptography;

namespace GostCryptography.Gost_R3410
{
    /// <summary>
    /// Базовый класс всех реализаций общего секретного ключа ГОСТ Р 34.10
    /// </summary>
    public abstract class Gost_R3410_KeyExchangeAlgorithm : GostKeyExchangeAlgorithm
    {
        /// <inheritdoc />
        [SecurityCritical]
        protected Gost_R3410_KeyExchangeAlgorithm(ProviderType providerType, SafeProvHandleImpl provHandle, SafeKeyHandleImpl keyHandle, Gost_R3410_KeyExchangeParams keyExchangeParameters, int keySize, int signatureAlgId) : base(providerType)
        {
            if (provHandle == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(provHandle));
            }

            if (keyHandle == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(keyHandle));
            }

            if (keyExchangeParameters == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(keyExchangeParameters));
            }

            _provHandle = provHandle.DangerousAddRef();
            _keyHandle = keyHandle.DangerousAddRef();
            _keyExchangeParameters = keyExchangeParameters;
            _keySize = keySize;
            _signatureAlgId = signatureAlgId;
        }

        [SecurityCritical]
        private readonly SafeProvHandleImpl _provHandle;
        [SecurityCritical]
        private readonly SafeKeyHandleImpl _keyHandle;
        [SecurityCritical]
        private readonly Gost_R3410_KeyExchangeParams _keyExchangeParameters;

        private readonly int _keySize;
        private readonly int _signatureAlgId;

        /// <inheritdoc />
        [SecuritySafeCritical]
        public override byte[] EncodeKeyExchange(SymmetricAlgorithm keyExchangeAlgorithm, GostKeyExchangeExportMethod keyExchangeExportMethod)
        {
            if (keyExchangeAlgorithm is Gost_28147_89_SymmetricAlgorithm symAlg)
            {
                return EncodeKeyExchangeInternal(symAlg, keyExchangeExportMethod);
            }

            if (keyExchangeAlgorithm is Gost_28147_89_SymmetricAlgorithmBase symAlgBase)
            {
                using (var gostKeyExchangeAlgorithm = new Gost_28147_89_SymmetricAlgorithm(symAlgBase.ProviderType))
                {
                    return gostKeyExchangeAlgorithm.EncodePrivateKey(symAlgBase, keyExchangeExportMethod);
                }
            }

            throw ExceptionUtility.Argument(nameof(keyExchangeAlgorithm), Resources.RequiredGost28147);
        }

        [SecurityCritical]
        private byte[] EncodeKeyExchangeInternal(Gost_28147_89_SymmetricAlgorithm keyExchangeAlgorithm, GostKeyExchangeExportMethod keyExchangeExportMethod)
        {
            switch (keyExchangeExportMethod)
            {
                case GostKeyExchangeExportMethod.GostKeyExport:
                    return EncodeKeyExchangeInternal(keyExchangeAlgorithm, Constants.CALG_SIMPLE_EXPORT);

                case GostKeyExchangeExportMethod.CryptoProKeyExport:
                    return EncodeKeyExchangeInternal(keyExchangeAlgorithm, Constants.CALG_PRO_EXPORT);
            }

            throw ExceptionUtility.ArgumentOutOfRange(nameof(keyExchangeExportMethod));
        }

        [SecurityCritical]
        private byte[] EncodeKeyExchangeInternal(Gost_28147_89_SymmetricAlgorithm keyExchangeAlgorithm, int keyExchangeExportAlgId)
        {
            Gost_28147_89_KeyExchangeInfo keyExchangeInfo;

            SafeKeyHandleImpl keyExchangeHandle = null;

            try
            {
                var importedKeyBytes = CryptoApiHelper.EncodePublicBlob(_keyExchangeParameters, _keySize, _signatureAlgId);
                CryptoApiHelper.ImportCspBlob(importedKeyBytes, _provHandle, _keyHandle, out keyExchangeHandle);
                CryptoApiHelper.SetKeyExchangeExportAlgId(ProviderType, keyExchangeHandle, keyExchangeExportAlgId);

                var symKeyHandle = keyExchangeAlgorithm.GetSafeHandle();
                keyExchangeInfo = CryptoApiHelper.ExportKeyExchange(symKeyHandle, keyExchangeHandle);
            }
            finally
            {
                keyExchangeHandle.TryDispose();
            }

            return keyExchangeInfo.Encode();
        }

        /// <inheritdoc />
        [SecuritySafeCritical]
        public override SymmetricAlgorithm DecodeKeyExchange(byte[] encodedKeyExchangeData, GostKeyExchangeExportMethod keyExchangeExportMethod)
        {
            switch (keyExchangeExportMethod)
            {
                case GostKeyExchangeExportMethod.GostKeyExport:
                    return DecodeKeyExchangeInternal(encodedKeyExchangeData, Constants.CALG_SIMPLE_EXPORT);

                case GostKeyExchangeExportMethod.CryptoProKeyExport:
                    return DecodeKeyExchangeInternal(encodedKeyExchangeData, Constants.CALG_PRO_EXPORT);
            }

            throw ExceptionUtility.ArgumentOutOfRange(nameof(keyExchangeExportMethod));
        }

        [SecurityCritical]
        private SymmetricAlgorithm DecodeKeyExchangeInternal(byte[] encodedKeyExchangeData, int keyExchangeExportAlgId)
        {
            var keyExchangeInfo = new Gost_28147_89_KeyExchangeInfo();
            keyExchangeInfo.Decode(encodedKeyExchangeData);

            SafeKeyHandleImpl symKeyHandle;
            SafeKeyHandleImpl keyExchangeHandle = null;

            try
            {
                var importedKeyBytes = CryptoApiHelper.EncodePublicBlob(_keyExchangeParameters, _keySize, _signatureAlgId);
                CryptoApiHelper.ImportCspBlob(importedKeyBytes, _provHandle, _keyHandle, out keyExchangeHandle);
                CryptoApiHelper.SetKeyExchangeExportAlgId(ProviderType, keyExchangeHandle, keyExchangeExportAlgId);

                symKeyHandle = CryptoApiHelper.ImportKeyExchange(_provHandle, keyExchangeInfo, keyExchangeHandle);
            }
            finally
            {
                keyExchangeHandle.TryDispose();
            }

            return new Gost_28147_89_SymmetricAlgorithm(ProviderType, _provHandle, symKeyHandle);
        }

        /// <inheritdoc />
        [SecuritySafeCritical]
        protected override void Dispose(bool disposing)
        {
            _keyHandle.TryDispose();
            _provHandle.TryDispose();

            base.Dispose(disposing);
        }
    }
}