using Microsoft.Data.Sqlite;
using System.Security.Cryptography;
using System.Text;

namespace SimPas2_Windows.Managers
{
  internal class CreditcardManager
  {
    private readonly string mConnectionString;
    private readonly byte[] mEncryptionKey;
    private readonly string mCulture;

    private string mJpLang;

    public CreditcardManager(string databasePath, byte[] encryptionKey, string culture)
    {
      mConnectionString = $"Data Source={databasePath}";
      mEncryptionKey = encryptionKey ?? throw new ArgumentNullException(nameof(encryptionKey));
      mCulture = culture;

      mJpLang = "ja-JP";
    }

    private bool AlreadyExists(string cardnumber, int? excludeId = null)
    {
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          SELECT COUNT(*) FROM Cc
          WHERE UPPER(Cardnumber) = UPPER(@cardnumber)";
        com.Parameters.AddWithValue("@cardnumber", cardnumber);

        if (excludeId.HasValue)
        {
          com.CommandText += " AND Id != @excludeId";
          com.Parameters.AddWithValue("@excludeId", excludeId.Value);
        }

        return Convert.ToInt32(com.ExecuteScalar()) > 0;
      }
    }

    public void AddCc(string brand, string cardnumber, string expiration, string cvc, string holdername, string note)
    {
      if (string.IsNullOrWhiteSpace(brand) || string.IsNullOrWhiteSpace(cardnumber) || string.IsNullOrWhiteSpace(expiration) || string.IsNullOrWhiteSpace(cvc) || string.IsNullOrWhiteSpace(holdername))
      {
        string err = mCulture == mJpLang
          ? "ブランド、カード番号、氏名、有効期限及び、CVCを御入力下さい。"
          : "Please fill in the brand, card number, full name, expiration, and CVC.";
        throw new ArgumentException(err);
      }

      string encryptedCvc = EncryptCvc(cvc);

      if (AlreadyExists(cardnumber))
      {
        string err = mCulture == mJpLang
          ? $"カード「{brand}/{holdername} ({expiration})」は既に存在します。"
          : $"The card '{brand}/{holdername} ({expiration})' already exists.";
        throw new ArgumentException(err);
      }

      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          INSERT INTO Cc (Brand, Cardnumber, Expiration, Cvc, Holdername, Note)
          VALUES ($brand, $cardnumber, $expiration, $cvc, $holdername, $note)";
        com.Parameters.AddWithValue("$brand", brand);
        com.Parameters.AddWithValue("$cardnumber", cardnumber);
        com.Parameters.AddWithValue("$expiration", expiration);
        com.Parameters.AddWithValue("$cvc", encryptedCvc);
        com.Parameters.AddWithValue("$holdername", holdername);
        com.Parameters.AddWithValue("$note", string.IsNullOrEmpty(note) ? DBNull.Value : note);
        com.ExecuteNonQuery();
      }
    }

    public bool EditCc(int id, string brand, string cardnumber, string expiration, string cvc, string holdername, string note)
    {
      if (string.IsNullOrWhiteSpace(brand) || string.IsNullOrWhiteSpace(cardnumber) || string.IsNullOrWhiteSpace(expiration) || string.IsNullOrWhiteSpace(cvc) || string.IsNullOrWhiteSpace(holdername))
      {
        string err = mCulture == mJpLang
          ? "ブランド、カード番号、氏名、有効期限及び、CVCを御入力下さい。"
          : "Please fill in the brand, card number, full name, expiration, and CVC.";
        throw new ArgumentException(err);
      }

      string encryptedCvc = EncryptCvc(cvc);

      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          UPDATE Cc
          SET Brand = $brand, Cardnumber = $cardnumber, Expiration = $expiration, Cvc = $cvc, Holdername = $holdername, Note = $note
          WHERE Id = $id";
        com.Parameters.AddWithValue("$id", id);
        com.Parameters.AddWithValue("$brand", brand);
        com.Parameters.AddWithValue("$cardnumber", cardnumber);
        com.Parameters.AddWithValue("$expiration", expiration);
        com.Parameters.AddWithValue("$cvc", encryptedCvc);
        com.Parameters.AddWithValue("$holdername", holdername);
        com.Parameters.AddWithValue("$note", string.IsNullOrEmpty(note) ? DBNull.Value : note);
        return com.ExecuteNonQuery() > 0;
      }
    }

    public bool DeleteCc(int id)
    {
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = "DELETE FROM Cc WHERE Id = $id";
        com.Parameters.AddWithValue("$id", id);
        return com.ExecuteNonQuery() > 0;
      }
    }

    public List<(int Id, string Brand, string Cardnumber, string Expiration, string Cvc, string Holdername, string Note)> GetAll(string keyword = "")
    {
      var ccs = new List<(int, string, string, string, string, string, string)>();
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        if (string.IsNullOrWhiteSpace(keyword))
        {
          com.CommandText = @"
          SELECT Id, Brand, Cardnumber, Expiration, Cvc, Holdername, Note FROM Cc
          ORDER BY Brand ASC";
        }
        else
        {
          com.CommandText = @"
          SELECT Id, Brand, Cardnumber, Expiration, Cvc, Holdername, Note FROM Cc
          WHERE Brand LIKE @keyword OR Holdername LIKE @keyword OR Cardnumber LIKE @keyword
          ORDER BY Brand ASC";
          com.Parameters.AddWithValue("@keyword", $"%{keyword}%");
        }

        using (SqliteDataReader reader = com.ExecuteReader())
        {
          while (reader.Read())
          {
            string encryptedCvc = reader.GetString(4);
            string decryptedCvc = DecryptCvc(encryptedCvc);
            ccs.Add((
              reader.GetInt32(0),
              reader.GetString(1),
              reader.GetString(2),
              reader.GetString(3),
              decryptedCvc,
              reader.GetString(5),
              reader.IsDBNull(6) ? string.Empty : reader.GetString(6)
            ));
          }
        }
      }

      return ccs;
    }

    private string EncryptCvc(string answer)
    {
      using (Aes aes = Aes.Create())
      {
        aes.Key = mEncryptionKey;
        aes.GenerateIV();
        byte[] iv = aes.IV;

        using (ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, iv))
        {
          byte[] plainBytes = Encoding.UTF8.GetBytes(answer);
          byte[] encryptedBytes = encryptor.TransformFinalBlock(plainBytes, 0, plainBytes.Length);
          byte[] result = new byte[iv.Length + encryptedBytes.Length];

          Buffer.BlockCopy(iv, 0, result, 0, iv.Length);
          Buffer.BlockCopy(encryptedBytes, 0, result, iv.Length, encryptedBytes.Length);

          return Convert.ToBase64String(result);
        }
      }
    }

    private string DecryptCvc(string encryptedAnswer)
    {
      byte[] combined = Convert.FromBase64String(encryptedAnswer);
      byte[] iv = new byte[16];
      byte[] encryptedBytes = new byte[combined.Length - iv.Length];
      Buffer.BlockCopy(combined, 0, iv, 0, iv.Length);
      Buffer.BlockCopy(combined, iv.Length, encryptedBytes, 0, encryptedBytes.Length);

      using (Aes aes = Aes.Create())
      {
        aes.Key = mEncryptionKey;
        aes.IV = iv;

        using (ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV))
        {
          byte[] decryptedBytes = decryptor.TransformFinalBlock(encryptedBytes, 0, encryptedBytes.Length);
          return Encoding.UTF8.GetString(decryptedBytes);
        }
      }
    }
  }
}