using System;
using System.Net;
using System.Net.Sockets;
using System.Security.Cryptography;
using System.Text;

namespace Client
{
    class Program
    {
        const int STD_PORT = 1234;
        const string STD_IP = "127.0.0.1";
        const int STD_MSG_SIZE = 1024;
        const int STD_HEAD_LEN = 1;
        const string STD_CRYPTOKEY = "mojKluc";

       

        static string Recive(NetworkStream networkStream)
        {
            try
            {
                byte[] reciveMessage = new byte[STD_MSG_SIZE];
                int lenght = networkStream.Read(reciveMessage, 0, reciveMessage.Length);
                return Encoding.UTF8.GetString(reciveMessage, 0, lenght);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message + e.StackTrace);
                return "";
            }
        }

        static void Send(NetworkStream networkStream, string Message)
        {
            try
            {
                byte[] bytes = Encoding.UTF8.GetBytes(Message);
                networkStream.Write(bytes, 0, bytes.Length);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            
        }

        static string Decrypt(string encrypt, string key)
        {
            try
            {
              
                using (MD5CryptoServiceProvider hashMD5Provider = new MD5CryptoServiceProvider())
                {
                    using (var tripleDes = TripleDES.Create())
                    {
                        tripleDes.Mode = CipherMode.ECB;
                        tripleDes.Padding = PaddingMode.PKCS7;
                        tripleDes.Key = hashMD5Provider.ComputeHash(Encoding.UTF8.GetBytes(key));
                        byte[] byteBuff = Convert.FromBase64String(encrypt);
                        return Encoding.Unicode.GetString(tripleDes.CreateDecryptor().TransformFinalBlock(byteBuff, 0, byteBuff.Length));
                    }
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
                return "";
            }
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Client\n");
            while (true)
            {
                Console.Write("Vnesi ukaz: ");
                string cmd = "";
                do
                {
                    cmd = Console.ReadLine();
                }
                while (cmd == null || cmd == "");

                try
                {
                    TcpClient tcpClient = new TcpClient();
                    tcpClient.Connect(STD_IP, STD_PORT);
                    NetworkStream networkStream = tcpClient.GetStream();
                    Send(networkStream, cmd);

                    string response = Recive(networkStream);
                    Console.WriteLine(response + "\n");

                    if (cmd[0] == 'G')
                    {
                        Console.WriteLine(Decrypt(response,STD_CRYPTOKEY));
                    }

                    tcpClient.Close();
                    if(response == "Q") return;
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.Message);
                    return;
                }

            }
        }
    }
}