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;
        }

        public static bool TryGetEncryptor(this IDictionary<string, IRSAEncryptor> pairs, string issuer, string audience, out IRSAEncryptor? encryptor) 
            => pairs.TryGetValue($"{issuer}:{audience}", out encryptor);

        public static IRSAEncryptor? GetEncryptor(this IDictionary<string, IRSAEncryptor> pairs, string issuer, string audience) 
            => pairs.TryGetEncryptor(issuer: issuer, audience: audience, out var encryptor) ? encryptor : null;

        public static IRSADecryptor GetRSADecryptor(this ICryptFactory factory, string issuer, string audience)
            => factory[$"{issuer}:{audience}"];

        public static bool TryGetRSADecryptor(this ICryptFactory factory, string issuer, string audience, out IRSADecryptor? decryptor)
            => factory.TryGetRSADecryptor($"{issuer}:{audience}", out decryptor);

        public static IRSAEncryptor GetRSAEncryptor(this ICryptFactory factory, string issuer, string audience)
            => factory[$"{issuer}:{audience}"].Encryptor;

        public static bool TryGetRSADecryptor(this ICryptFactory factory, string issuer, string audience, out IRSAEncryptor? encryptor)
        {
            if(factory.TryGetRSADecryptor($"{issuer}:{audience}", out var decryptor) && decryptor is not null)
            {
                encryptor = decryptor.Encryptor;
                return true;
            }
            else
            {
                encryptor = null;
                return false;
            }
        }

        private static string CreatePath(string key, string? directory = null)
        {
            directory ??= Environment.CurrentDirectory;

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

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

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

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

        public static void SavePem(this IRSACryptographer decryptor, string issuer, string audience, string? directory = null)
            => decryptor.SavePem($"{issuer}:{audience}", directory);

        public static async Task SavePemAsync(this IRSACryptographer decryptor, string issuer, string audience, string? directory = null)
            => await decryptor.SavePemAsync($"{issuer}:{audience}", directory);
    }
}