DigitalData.Core/DigitalData.Core.Security.Extensions/RSAExtensions.cs

using DigitalData.Core.Abstractions.Security;
using System.Collections.Concurrent;
using System.Security.Cryptography;

namespace DigitalData.Core.Security.Extensions
{
    public static class RSAExtensions
    {
        public static RSA ToRSA(this string pem)
        {
            var rsa = RSA.Create();
            rsa.ImportFromPem(pem);
            return rsa;
        }
        
        private static string CreatePath(string filename, string? directory = null)
        {
            directory ??= Environment.CurrentDirectory;

            if (!Directory.Exists(directory))
            {
                Directory.CreateDirectory(directory);
            }

            return Path.Combine(directory, $"{filename}.pem");
        }

        private static readonly ConcurrentDictionary<string, SemaphoreSlim> FileLocks = new();

        public static void SavePem(this IRSACryptographer decryptor, string key, string? directory = null)
        {
            var filePath = CreatePath(filename: key, directory : directory);
            var fileLock = FileLocks.GetOrAdd(filePath, _ => new (1, 1));
            fileLock.Wait();
            try
            {
                File.WriteAllText(filePath, decryptor.Pem);
            }
            finally
            {
                fileLock.Release();
            }
        }

        public static async Task SavePemAsync(this IRSACryptographer decryptor, string key, string? directory = null)
        {
            var filePath = CreatePath(filename: key, directory: directory);
            var fileLock = FileLocks.GetOrAdd(filePath, _ => new (1, 1));
            await fileLock.WaitAsync();
            try
            {
                await File.WriteAllTextAsync(filePath, decryptor.Pem);
            }
            finally
            {
                fileLock.Release();
            }
        }
    }
}