DigitalData.Core/DigitalData.Core.Security/Cryptographer/RSADecryptor.cs

using DigitalData.Core.Abstractions.Security;
using DigitalData.Core.Security.Extensions;
using System.Security.Cryptography;

namespace DigitalData.Core.Security.Cryptographer
{
    public class RSADecryptor : RSACryptographer, IRSADecryptor, IRSACryptographer
    {
        private string? _pem;

        public override string Pem { get => _pem ?? throw PemIsNullException; init => _pem = value; }

        public bool IsPemNull => _pem is null;

        public bool IsEncrypted { get; init; }

        private readonly Lazy<IRSAEncryptor> _lazyEncryptor;

        public IRSAEncryptor Encryptor => _lazyEncryptor.Value;

        public RSADecryptor()
        {
            _lazyEncryptor = new(() => new RSAEncryptor()
            {
                Pem = RSA.ExportRSAPublicKeyPem(),
                Padding = Padding
            });
        }

        public byte[] Decrypt(byte[] data) => RSA.Decrypt(data, Padding);

        public string Decrypt(string data) => RSA.Decrypt(data.Base64ToByte(), Padding).BytesToString();

        internal void SetPem(string pem) => _pem = pem;

        public void Init()
        {
            if (_pem is null)
                throw PemIsNullException;

            if (IsEncrypted)
                RSA.ImportFromEncryptedPem(Pem, Secrets.PBE_PASSWORD.AsSpan());
            else
                RSA.ImportFromPem(Pem);
        }

        private InvalidOperationException PemIsNullException => new($"Pem is not initialized. Please ensure that the PEM is set or properly loaded from the file. Issuer: {Issuer}, Audience: {Audience}.");
    }
}