using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace MySQLBackupLibrary.Classes
{
    class EncryptionHelper
    {
        private static readonly string SaltKey = "{G7OBB2fkNp1RRiq3rYqjxJ8Tu3tfoSqTxWDclYQ2TG24M47Uuk94WHdIBisR}";
        private static readonly string PasswordHash = "1A4S!fas@S52107lLK4856as5r";
        private static readonly string VIKey = "@151fa721b215m9826";

        /**
         * Encrypt a string
         */
        public static string Encrypt(string input)
        {
            byte[] inputBytes = UTF8Encoding.UTF8.GetBytes(input);
            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
            var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.Zeros };
            var encryptor = symmetricKey.CreateEncryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));

            byte[] cipherTextBytes;

            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(inputBytes, 0, inputBytes.Length);
                    cryptoStream.FlushFinalBlock();
                    cipherTextBytes = memoryStream.ToArray();
                    cryptoStream.Close();
                }
                memoryStream.Close();
            }
            return Convert.ToBase64String(cipherTextBytes);
        }

        /**
         * Decrypt a string
         */
        public static string Decrypt(string input)
        {
            byte[] cipherTextBytes = Convert.FromBase64String(input);
            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
            var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.None };

            var decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            var memoryStream = new MemoryStream(cipherTextBytes);
            var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
            byte[] plainTextBytes = new byte[cipherTextBytes.Length];

            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
            memoryStream.Close();
            cryptoStream.Close();
            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount).TrimEnd("\0".ToCharArray());
        }
    }
}