using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;

namespace UDPoverTCP_TunelClient
{
    class GatewayUDP_TCP
    {
        private TcpClient tcpClient;
        private UdpClient udpClient;
        private const int DATAGRAM_SIZE = 8196;
        //IPEndPoint object will allow us to read datagrams sent from any source.
        private IPEndPoint remoteIpEndPoint;

        public GatewayUDP_TCP(TcpClient tcp_client, UdpClient udp_client)
        {
            tcpClient = tcp_client;
            udpClient = udp_client;
            remoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);
        }
        public void relayDatagramFromUDPtoTCP()
        {
            try
            {
                Byte[] udpData = null;
                Byte[] dataSize = null;
                // Get a stream object for reading and writing
                NetworkStream tcpStream = tcpClient.GetStream();
                do
                {
                    //Console.WriteLine("Waiting for Datagram ...");
                    // Blocks until a message returns on this socket from a remote host.
                    udpData = udpClient.Receive(ref remoteIpEndPoint);
                    dataSize = System.Text.Encoding.ASCII.GetBytes(udpData.Length.ToString()+'\0');
                    // Send datagram size.
                    tcpStream.Write(dataSize, 0, dataSize.Length);
                    // Send datagram data.
                    tcpStream.Write(udpData, 0, udpData.Length);
                } while (udpData.Length != 0);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
        }
        public void relayDatagramFromTCPtoUDP()
        {
            try
            {
                NetworkStream tcpStream = tcpClient.GetStream();
                int i, udpLength, dataRead, readCount;
                string s_dataLength;
                Byte[] dataSize = new Byte[DATAGRAM_SIZE];
                Byte[] udpData = new Byte[DATAGRAM_SIZE];

                do
                {
                    readCount = 0;
                    // read datagram size, it finishes with 0 delimiter.
                    do {
                        if ((i = tcpStream.Read(dataSize, readCount, 1)) != 1)
                            return;
                        readCount += i;
                    } while(dataSize[readCount-1]!=0);
                    // Translate data bytes to a ASCII string.
                    s_dataLength = System.Text.Encoding.ASCII.GetString(dataSize, 0, readCount);
                    udpLength = Convert.ToInt32(s_dataLength);
                    // Read 
                    dataRead = 0;
                    do
                    {
                        if ((i = tcpStream.Read(udpData, dataRead, udpLength - dataRead)) == 0)
                            return;
                        dataRead += i;
                    } while (dataRead < udpLength);
                    udpClient.Send(udpData, dataRead, remoteIpEndPoint);
                } while (udpLength != 0);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
        }
    }
}