SimPas2-Windows/Managers/PinManager.cs

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

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

    private string mJpLang;

    public PinManager(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 website, int? excludeId = null)
    {
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          SELECT COUNT(*) FROM Pin
          WHERE UPPER(Website) = UPPER(@website)";
        com.Parameters.AddWithValue("@website", website);

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

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

    public void AddPin(string website, string pincode, string note)
    {
      if (string.IsNullOrWhiteSpace(website) || string.IsNullOrWhiteSpace(pincode))
      {
        string err = mCulture == mJpLang
          ? "ウェブサイト及び暗証番号を御入力下さい。"
          : "Please fill in the website and pincode.";
        throw new ArgumentException(err);
      }

      if (AlreadyExists(website))
      {
        string err = mCulture == mJpLang
          ? $"ウェブサイト「{website}」付き暗証番号は既に存在します。"
          : $"A pincode with the website '{website}' already exists.";
        throw new ArgumentException(err);
      }

      string encryptedPin = EncryptPin(pincode);
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"INSERT INTO Pin (Website, Pincode, Note) VALUES ($website, $pincode, $note)";
        com.Parameters.AddWithValue("$website", website);
        com.Parameters.AddWithValue("$pincode", encryptedPin);
        com.Parameters.AddWithValue("$note", string.IsNullOrEmpty(note) ? DBNull.Value : note);
        com.ExecuteNonQuery();
      }
    }

    public bool EditPin(int id, string website, string pincode, string note)
    {
      if (string.IsNullOrWhiteSpace(website) || string.IsNullOrWhiteSpace(pincode))
      {
        string err = mCulture == mJpLang
          ? "ウェブサイト及び暗証番号を御入力下さい。"
          : "Please fill in the website and pincode.";
        throw new ArgumentException(err);
      }

      if (AlreadyExists(website, id))
      {
        string err = mCulture == mJpLang
          ? $"ウェブサイト「{website}」付き暗証番号は既に存在します。"
          : $"A pincode with the website '{website}' already exists.";
        throw new ArgumentException(err);
      }

      string encryptedPin = EncryptPin(pincode);
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"UPDATE Pin SET Website = $website, Pincode = $pincode, Note = $note WHERE Id = $id";
        com.Parameters.AddWithValue("id", id);
        com.Parameters.AddWithValue("$website", website);
        com.Parameters.AddWithValue("$pincode", encryptedPin);
        com.Parameters.AddWithValue("$note", string.IsNullOrEmpty(note) ? DBNull.Value : note);

        return com.ExecuteNonQuery() > 0;
      }
    }

    public bool DeletePin(int id)
    {
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = "DELETE FROM Pin WHERE Id = $id";
        com.Parameters.AddWithValue("$id", id);

        return com.ExecuteNonQuery() > 0;
      }
    }

    public List<(int Id, string Website, string Pincode, string Note)> GetAll(string keyword = "")
    {
      var pins = new List<(int, string, string, string)>();
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();

        if (string.IsNullOrWhiteSpace(keyword))
        {
          com.CommandText = @"
            SELECT Id, Website, Pincode, Note FROM Pin
            ORDER BY Website ASC";
        }
        else
        {
          com.CommandText = @"
            SELECT Id, Website, Pincode, Note FROM Pin
            WHERE Website LIKE @keyword
            ORDER BY Website ASC";
          com.Parameters.AddWithValue("@keyword", $"%{keyword}%");
        }

          using (SqliteDataReader reader = com.ExecuteReader())
          {
            while (reader.Read())
            {
              string encryptedPin = reader.GetString(2);
              string decryptedPin = DecryptPin(encryptedPin);
              pins.Add((
                reader.GetInt32(0),
                reader.GetString(1),
                decryptedPin,
                reader.IsDBNull(3) ? string.Empty : reader.GetString(3)
              ));
            }
          }
      }

      return pins;
    }

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

        using (var encryptor = aes.CreateEncryptor(aes.Key, iv))
        {
          byte[] plainBytes = Encoding.UTF8.GetBytes(plainPassword);
          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 DecryptPin(string encryptedPassword)
    {
      byte[] combined = Convert.FromBase64String(encryptedPassword);
      byte[] iv = new byte[16]; // AES IV is 16 bytes
      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 (var decryptor = aes.CreateDecryptor(aes.Key, aes.IV))
        {
          byte[] decryptedBytes = decryptor.TransformFinalBlock(encryptedBytes, 0, encryptedBytes.Length);
          return Encoding.UTF8.GetString(decryptedBytes);
        }
      }
    }
  }
}