using DigitalData.Core.Security.Cryptographer;
using System.Security.Cryptography;

namespace DigitalData.Core.Security.Config
{
    public class AsymCryptParams : RSAFactoryParams
    {
        public string PemDirectory { get; init; } = string.Empty;

        public string Separator { get; init; } = "_-_";

        public string EncryptorTag { get; init; } = "public";

        public string DecryptorTag { get; init; } = "private";

        public string EncryptedDecryptorTag { get; init; } = "enc-private";

        public IEnumerable<RSADecryptor> Decryptors { get; init; } = new List<RSADecryptor>();

        public IEnumerable<RSAEncryptor> Encryptors { get; init; } = new List<RSAEncryptor>();

        /// <summary>
        /// 0: Issuer - 1: Audience - 2: Type tag - 3: Secret version
        /// </summary>
        private string CreateFileName(params object[] objs) => string.Join(Separator, objs);

        private static (bool IsDecryptor, bool IsEncrypted) StateOf(RSACryptographer crypt) => crypt switch
        {
            RSAEncryptor => (false, false),
            RSADecryptor decryptor => (true, decryptor.Encrypt),
            _ => throw new InvalidOperationException("Unknown cryptographer type. The crypt parameter must be either RSAEncryptor or RSADecryptor.")
        };

        private string TypeTagOf((bool IsDecryptor, bool IsEncrypted) stateOfCrypt) => stateOfCrypt switch
        {
            (false, false) => EncryptorTag,
            (true, false) => DecryptorTag,
            (true, true) => EncryptedDecryptorTag,
            _ => throw new InvalidOperationException("Unknown cryptographer type. The crypt parameter must be either RSAEncryptor or RSADecryptor.")
        };

        private string CreatePem((bool IsDecryptor, bool IsEncrypted) stateOfCrypt) => stateOfCrypt switch
        {
            (true, false) => Instance.RSAFactory.CreateRSAPrivateKeyPem(keySizeInBits: KeySizeInBits),
            (true, true) => Instance.RSAFactory.CreateEncryptedPrivateKeyPem(keySizeInBits: KeySizeInBits, password: Secrets.PBE_PASSWORD,
                pbeEncryptionAlgorithm: PbeEncryptionAlgorithm, hashAlgorithmName: PbeHashAlgorithmName, iterationCount: PbeIterationCount),
            _ => throw new InvalidOperationException("Unknown cryptographer type. The crypt parameter must be either RSAEncryptor or RSADecryptor.")
        };

        public override void OnDeserialized()
        {
            base.OnDeserialized();

            // Create root folder if it does not exist
            if (!Directory.Exists(PemDirectory))
                Directory.CreateDirectory(PemDirectory);

            // merge decryptors and encryptors to process under one loop
            var cryptographers = Encryptors.Cast<RSACryptographer>().Concat(Decryptors.Cast<RSACryptographer>());

            foreach (var crypt in cryptographers)
            {
                // set default path
                if (crypt.IsPemNull)
                {
                    var state = StateOf(crypt);

                    var file_name_params = new List<object> { crypt.Issuer, crypt.Audience, TypeTagOf(state) };
                    if (state.IsEncrypted)
                        file_name_params.Add(Secrets.Version);

                    var file_name = CreateFileName(file_name_params);
                    var path = Path.Combine(PemDirectory, file_name);

                    if (File.Exists(path))
                        crypt.SetPem(File.ReadAllText(path));
                    else
                    {
                        var pem = CreatePem(state);
                        crypt.SetPem(File.ReadAllText(pem));
                        Task.Run(async () => File.WriteAllTextAsync(path: path, pem));
                    }
                }

                crypt.Init();
            }
        }
    }
}