using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace WebsitePanel.WebDavPortal.Cryptography
{
    public class Rfc2898Cryptography : ICryptography
    {
        public string PasswordHash { get; set; }
        public string SaltKey { get; set; }
        public string VIKey { get; set; }

        public Rfc2898Cryptography(string passwordHash, string saltKey, string viKey)
        {
            PasswordHash = passwordHash;
            SaltKey = saltKey;
            VIKey = viKey;
        }

        public string Encrypt(string plainText)
        {
            byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256/8);
            var symmetricKey = new RijndaelManaged {Mode = CipherMode.CBC, Padding = PaddingMode.Zeros};
            ICryptoTransform 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(plainTextBytes, 0, plainTextBytes.Length);
                    cryptoStream.FlushFinalBlock();
                    cipherTextBytes = memoryStream.ToArray();
                    cryptoStream.Close();
                }
                memoryStream.Close();
            }
            return Convert.ToBase64String(cipherTextBytes);
        }

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

            ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            var memoryStream = new MemoryStream(cipherTextBytes);
            var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
            var 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());
        }
    }
}