using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using static System.Net.Mime.MediaTypeNames;

namespace TrelloIntegration
{
  /// <summary>
  /// Verschlüsselt und entschlüsselt Trello API-Key und Token mit AES.
  /// </summary>
  public static class TrelloConfig
  {
    /// <summary>
    /// Geheimer Schlüssel für Verschlüsselung (muss sicher gespeichert werden!)
    /// In Produktion besser aus Umgebungsvariablen oder sicherem Speicher lesen.
    /// </summary>
    private const string SecretKey = "DEIN_GEHEIMER_SCHLUESSEL_32_CHAR"; // 32 Zeichen für AES-256

    /// <summary>
    /// Verschlüsselt einen Text und gibt Base64 zurück.
    /// </summary>
    public static string Encrypt(string plainText)
    {
      if (string.IsNullOrEmpty(plainText))
        throw new ArgumentException("Text darf nicht leer sein", nameof(plainText));

      var aes = Aes.Create();
      aes.Key = Encoding.UTF8.GetBytes(SecretKey);
      aes.IV = new byte[16]; // IV für Demo; in Produktion zufällig generieren

      var encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
      var plainBytes = Encoding.UTF8.GetBytes(plainText);
      var cipherBytes = encryptor.TransformFinalBlock(plainBytes, 0, plainBytes.Length);

      // IV + verschlüsselte Daten speichern (für Produktion mit zufälligem IV)
      var combined = new byte[aes.IV.Length + cipherBytes.Length];
      Array.Copy(aes.IV, 0, combined, 0, aes.IV.Length);
      Array.Copy(cipherBytes, 0, combined, aes.IV.Length, cipherBytes.Length);

      return Convert.ToBase64String(combined);
    }

    /// <summary>
    /// Entschlüsselt einen Base64-Text.
    /// </summary>
    public static string Decrypt(string encryptedBase64)
    {
      if (string.IsNullOrEmpty(encryptedBase64))
        throw new ArgumentException("Text darf nicht leer sein", nameof(encryptedBase64));

      var combined = Convert.FromBase64String(encryptedBase64);

      var aes = Aes.Create();
      aes.Key = Encoding.UTF8.GetBytes(SecretKey);

      // IV aus den ersten 16 Bytes extrahieren
      var iv = new byte[16];
      Array.Copy(combined, 0, iv, 0, 16);
      aes.IV = iv;

      var decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
      var cipherBytes = new byte[combined.Length - 16];
      Array.Copy(combined, 16, cipherBytes, 0, cipherBytes.Length);

      var plainBytes = decryptor.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);
      return Encoding.UTF8.GetString(plainBytes);
    }

    /// <summary>
    /// Erstellt verschlüsselte Werte für App.config (einmalig ausführen).
    /// </summary>
    public static void CreateEncryptedConfigValues(string apiKey, string token)
    {
      var encryptedKey = Encrypt(apiKey);
      var encryptedToken = Encrypt(token);

      Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
      config.AppSettings.Settings.Remove("TrelloApiKeyEncrypted");
      config.AppSettings.Settings.Add("TrelloApiKeyEncrypted", encryptedKey);
      config.AppSettings.Settings.Remove("TrelloTokenEncrypted");
      config.AppSettings.Settings.Add("TrelloTokenEncrypted", encryptedToken);
      config.Save();

      Console.WriteLine("=== FÜR APP.CONFIG ===");
      Console.WriteLine($"<add key=\"TrelloApiKeyEncrypted\" value=\"{encryptedKey}\"/>");
      Console.WriteLine($"<add key=\"TrelloTokenEncrypted\" value=\"{encryptedToken}\"/>");
      Console.WriteLine("======================");
    }

    /// <summary>
    /// Gibt den API-Key aus App.config (entschlüsselt).
    /// </summary>
    public static string GetApiKey()
    {
      try
      {
        var encrypted = System.Configuration.ConfigurationManager
            .AppSettings["TrelloApiKeyEncrypted"];
        return string.IsNullOrEmpty(encrypted) ? null : Decrypt(encrypted);
      }
      catch
      {
        return null;
      }
    }

    /// <summary>
    /// Gibt den Token aus App.config (entschlüsselt).
    /// </summary>
    public static string GetToken()
    {
      try
      {
        var encrypted = System.Configuration.ConfigurationManager 
            .AppSettings["TrelloTokenEncrypted"];
        return string.IsNullOrEmpty(encrypted) ? null : Decrypt(encrypted);
      }
      catch
      {
        return null;
      }
    }

    /// <summary>
    /// Prüft, ob verschlüsselte Credentials in App.config vorhanden sind.
    /// </summary>
    public static bool HasCredentials()
    {
      var key = System.Configuration.ConfigurationManager.AppSettings["TrelloApiKeyEncrypted"];
      var token = System.Configuration.ConfigurationManager.AppSettings["TrelloTokenEncrypted"];
      return !string.IsNullOrEmpty(key) && !string.IsNullOrEmpty(token);
    }
  }
}