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

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

    private string mJpLang;

    public CryptoManager(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 currency, string name, int? excludeId = null)
    {
      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          SELECT COUNT(*) FROM Crypto
          WHERE UPPER(Currency) = UPPER(@currency) AND UPPER(Name) = UPPER(@name)";
        com.Parameters.AddWithValue("@currency", currency);
        com.Parameters.AddWithValue("@name", name);

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

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

    public void AddCrypto(string currency, string name, string address, string seed, string viewkey, string spendkey, string height, string password, string note)
    {
      if (string.IsNullOrWhiteSpace(currency) || string.IsNullOrWhiteSpace(name) || string.IsNullOrWhiteSpace(address))
      {
        string err = mCulture == mJpLang
          ? "通貨、ウォレット名及び、住所を御入力下さい。"
          : "Please fill in the currency, wallet name, and address.";
        throw new ArgumentException(err);
      }

      string encryptedPassword = !string.IsNullOrWhiteSpace(password) ? EncryptInfo(password) : "";
      string encryptedSeed = !string.IsNullOrWhiteSpace(seed) ? EncryptInfo(seed) : "";
      string encryptedViewkey = !string.IsNullOrWhiteSpace(viewkey) ? EncryptInfo(viewkey) : "";
      string encryptedSpendkey = !string.IsNullOrWhiteSpace(spendkey) ? EncryptInfo(spendkey) : "";

      if (AlreadyExists(currency, name))
      {
        string err = mCulture == mJpLang
          ? $"通貨及びウォレット名「{currency}/{name}」エントリは既に存在します。"
          : $"An entry with the currency and wallet name for '{currency}/{name}' already exists.";
        throw new ArgumentException(err);
      }

      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          INSERT INTO Crypto (Currency, Name, Address, Seed, Viewkey, Spendkey, Height, Password, Note)
          VALUES ($currency, $name, $address, $seed, $viewkey, $spendkey, $height, $password, $note)";
        com.Parameters.AddWithValue("$currency", currency);
        com.Parameters.AddWithValue("$name", name);
        com.Parameters.AddWithValue("$address", address);
        com.Parameters.AddWithValue("$seed", string.IsNullOrEmpty(seed) ? DBNull.Value : encryptedSeed);
        com.Parameters.AddWithValue("$viewkey", string.IsNullOrEmpty(viewkey) ? DBNull.Value : encryptedViewkey);
        com.Parameters.AddWithValue("$spendkey", string.IsNullOrEmpty(spendkey) ? DBNull.Value : encryptedSpendkey);
        com.Parameters.AddWithValue("$height", string.IsNullOrEmpty(height) ? DBNull.Value : height);
        com.Parameters.AddWithValue("$password", string.IsNullOrEmpty(password) ? DBNull.Value : encryptedPassword);
        com.Parameters.AddWithValue("$note", string.IsNullOrEmpty(note) ? DBNull.Value : note);
        com.ExecuteNonQuery();
      }
    }

    public bool EditCrypto(int id, string currency, string name, string address, string seed, string viewkey, string spendkey, string height, string password, string note)
    {
      if (string.IsNullOrWhiteSpace(currency) || string.IsNullOrWhiteSpace(name) || string.IsNullOrWhiteSpace(address))
      {
        string err = mCulture == mJpLang
          ? "通貨、ウォレット名及び、住所を御入力下さい。"
          : "Please fill in the currency, wallet name, and address.";
        throw new ArgumentException(err);
      }
      
      string encryptedPassword = string.IsNullOrEmpty(password) ? string.Empty : EncryptInfo(password);
      string encryptedSeed = string.IsNullOrEmpty(seed) ? string.Empty : EncryptInfo(seed);
      string encryptedViewkey = string.IsNullOrEmpty(viewkey) ? string.Empty : EncryptInfo(viewkey);
      string encryptedSpendkey = string.IsNullOrEmpty(spendkey) ? string.Empty : EncryptInfo(spendkey);

      using (SqliteConnection conn = new SqliteConnection(mConnectionString))
      {
        conn.Open();
        SqliteCommand com = conn.CreateCommand();
        com.CommandText = @"
          UPDATE Crypto
          SET Currency = $currency, Name = $name, Address = $address, Seed = $seed, Viewkey = $viewkey, Spendkey = $spendkey, Height = $height, Password = $password, Note = $note
          WHERE Id = $id";
        com.Parameters.AddWithValue("$id", id);
        com.Parameters.AddWithValue("$currency", currency);
        com.Parameters.AddWithValue("$name", name);
        com.Parameters.AddWithValue("$address", address);
        com.Parameters.AddWithValue("$seed", string.IsNullOrEmpty(seed) ? DBNull.Value : encryptedSeed);
        com.Parameters.AddWithValue("$viewkey", string.IsNullOrEmpty(viewkey) ? DBNull.Value : encryptedViewkey);
        com.Parameters.AddWithValue("$spendkey", string.IsNullOrEmpty(spendkey) ? DBNull.Value : encryptedSpendkey);
        com.Parameters.AddWithValue("$height", string.IsNullOrEmpty(height) ? DBNull.Value : height);
        com.Parameters.AddWithValue("$password", string.IsNullOrEmpty(password) ? DBNull.Value : encryptedPassword);
        com.Parameters.AddWithValue("$note", string.IsNullOrEmpty(note) ? DBNull.Value : note);
        return com.ExecuteNonQuery() > 0;
      }
    }

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

    public List<(int Id, string Currency, string Name, string Address, string Seed, string Viewkey, string Spendkey, string Height, string Password, string Note)> GetAll(string keyword = "")
    {
      var cryptos = new List<(int, string, string, string, 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, Currency, Name, Address, Seed, Viewkey, Spendkey, Height, Password, Note FROM Crypto
          ORDER BY Currency DESC";
        }
        else
        {
          com.CommandText = @"
          SELECT Id, Currency, Name, Address, Seed, Viewkey, Spendkey, Height, Password, Note FROM Crypto
          WHERE Currency LIKE @keyword OR Name LIKE @keyword
          ORDER BY Currency DESC";
          com.Parameters.AddWithValue("@keyword", $"%{keyword}%");
        }

        using (SqliteDataReader reader = com.ExecuteReader())
        {
          while (reader.Read())
          {
            string decryptedSeed = DecryptInfo(reader.GetString(4));
            string decryptedViewkey = reader.IsDBNull(5) ? string.Empty : DecryptInfo(reader.GetString(5));
            string decryptedSpendkey = reader.IsDBNull(6) ? string.Empty : DecryptInfo(reader.GetString(6));
            string decryptedPassword = reader.IsDBNull(8) ? string.Empty : DecryptInfo(reader.GetString(8));

            cryptos.Add((
              reader.GetInt32(0),
              reader.GetString(1),
              reader.GetString(2),
              reader.GetString(3),
              decryptedSeed,
              reader.IsDBNull(5) ? string.Empty : decryptedViewkey,
              reader.IsDBNull(6) ? string.Empty : decryptedSpendkey,
              reader.IsDBNull(7) ? string.Empty : reader.GetString(7),
              reader.IsDBNull(8) ? string.Empty : decryptedPassword,
              reader.IsDBNull(9) ? string.Empty : reader.GetString(9)
            ));
          }
        }
      }

      return cryptos;
    }

    private string EncryptInfo(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 DecryptInfo(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);
        }
      }
    }
  }
}