using GostCryptography.Properties;
using System;
using System.Security.Cryptography;

namespace GostCryptography.Base
{
    /// <summary>
    /// Класс проверки цифровой подписи ГОСТ
    /// </summary>
    public class GostSignatureDeformatter : AsymmetricSignatureDeformatter
    {
        /// <summary>
        /// Конструктор
        /// </summary>
        public GostSignatureDeformatter()
        {
        }

        /// <summary>
        /// Конструктор
        /// </summary>
        /// <param name="publicKey">Открытый ключ для проверки цифровой подписи</param>
        /// <exception cref="ArgumentOutOfRangeException"></exception>
        /// <exception cref="ArgumentNullException"></exception>
        public GostSignatureDeformatter(AsymmetricAlgorithm publicKey) : this()
        {
            SetKey(publicKey);
        }

        private GostAsymmetricAlgorithm _publicKey;

        /// <inheritdoc />
        public override void SetKey(AsymmetricAlgorithm publicKey)
        {
            if (publicKey == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(publicKey));
            }

            if (!(publicKey is GostAsymmetricAlgorithm gostPublicKey))
            {
                if (publicKey.SignatureAlgorithm.IndexOf("gost", StringComparison.OrdinalIgnoreCase) < 0)
                {
                    throw ExceptionUtility.ArgumentOutOfRange(nameof(publicKey), Resources.ShouldSupportGost3410);
                }

                gostPublicKey = new GostExternalAsymmetricAlgorithm(publicKey);
            }

            _publicKey = gostPublicKey;
        }

        /// <inheritdoc />
        public override void SetHashAlgorithm(string hashAlgorithmName)
        {
        }

        /// <inheritdoc />
        public override bool VerifySignature(byte[] hash, byte[] signature)
        {
            if (hash == null)
            {
                throw ExceptionUtility.ArgumentNull(nameof(hash));
            }

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

            var reverseSignature = (byte[])signature.Clone();
            Array.Reverse(reverseSignature);

            return _publicKey.VerifySignature(hash, reverseSignature);
        }
    }
}