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

namespace BeWo.Security
{
    public class EncryptionUtils
    {
        private static readonly byte[] _Rc2Iv = { 50, 241, 173, 46, 224, 103, 137, 72 };
        private static readonly byte[] _Rc2Key = { 140, 81, 67, 90, 70, 222, 51, 20, 154, 60, 68, 87, 112, 169, 38, 234 };

        public static string EncryptString(string stringToEncrypt)
        {
            var rc2Csp = new RC2CryptoServiceProvider();
            var encryptor = rc2Csp.CreateEncryptor(_Rc2Key, _Rc2Iv);

            using(var memoryStream = new MemoryStream())
            {
                using(var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                {
                    var toEncrypt = Encoding.UTF8.GetBytes(stringToEncrypt);

                    cryptoStream.Write(toEncrypt, 0, toEncrypt.Length);
                    cryptoStream.FlushFinalBlock();

                    var encrypted = memoryStream.ToArray();

                    return Convert.ToBase64String(encrypted);
                }
            }
        }

        public static string DecryptString(string stringToDecrypt)
        {
            if (String.IsNullOrEmpty(stringToDecrypt))
            {
                return "";
            }
            var rc2Csp = new RC2CryptoServiceProvider();
            var decryptor = rc2Csp.CreateDecryptor(_Rc2Key, _Rc2Iv);

            stringToDecrypt = stringToDecrypt.Replace(' ', '+');
            stringToDecrypt = stringToDecrypt.Trim(',');

            try
            {
                using (var memoryStream = new MemoryStream(Convert.FromBase64String(stringToDecrypt)))
                {
                    using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                    {
                        var bytes = new List<byte>();
                        int b;

                        do
                        {
                            b = cryptoStream.ReadByte();

                            if(b != -1)
                            {
                                bytes.Add(Convert.ToByte(b));
                            }
                        } while(b != -1);

                        return Encoding.UTF8.GetString(bytes.ToArray());
                    }
                }
            }
            catch(CryptographicException)
            {
                // Es wird davon ausgegangen, dass der String nicht verschlüsselt ist.
                return Encoding.UTF8.GetString(Convert.FromBase64String(stringToDecrypt));
            }
        }
    }
}