using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace tcpAddResponseProxy
{
    class tcpAddResponseProxy
    {
        static void Main(string[] args)
        {
            // 待ち受けアドレス、ポート
            string localEndpointStr = args[0];
            string localEndpointPortStr = args[1];

            // リダイレクト先アドレス、ポート
            string remoteEndpointStr = args[2];
            string remoteEndpointPortStr = args[3];

            IPEndPoint localEndpoint = new IPEndPoint(IPAddress.Parse(localEndpointStr), int.Parse(localEndpointPortStr));
            IPEndPoint remoteEndpoint = new IPEndPoint(IPAddress.Parse(remoteEndpointStr), int.Parse(remoteEndpointPortStr));

            proxyServer proxy = new proxyServer(localEndpoint, remoteEndpoint);
            Task task = Task.Run(() => proxy.Listen());
            task.Wait();
            proxy.Close();
        }
    }

    class proxyClient
    {
        IPEndPoint remoteEndpoint;

        public proxyClient(IPEndPoint endpoint)
        {
            remoteEndpoint = endpoint;
        }

        public void Send(string data)
        {
            using (TcpClient client = new TcpClient())
            {
                client.Connect(remoteEndpoint);
                Console.WriteLine("{0} {1} Connect to {2}", DateTime.Now, client.GetHashCode(), client.Client.RemoteEndPoint);

                using (NetworkStream stream = client.GetStream())
                {
                    byte[] buff = Encoding.UTF8.GetBytes(data);
                    stream.Write(buff, 0, buff.Length);
                    Console.WriteLine("{0} {1} Send Data:{2}", DateTime.Now, client.GetHashCode(), data);
                }
            }
        }
    }

    class proxyServer
    {
        TcpListener listener;
        IPEndPoint remoteEP;

        public proxyServer(IPEndPoint localEndpoint, IPEndPoint remoteEndpoint)
        {
            listener = new TcpListener(localEndpoint);
            remoteEP = remoteEndpoint;
        }

        public void Close()
        {
            listener.Stop();
            Console.WriteLine("{0} Stop Listen", DateTime.Now);
        }

        public async Task Listen()
        {
            listener.Start();

            Console.WriteLine("{0} Start Listen", DateTime.Now);

            while (true)
            {
                TcpClient connectClient = await listener.AcceptTcpClientAsync();
                Console.WriteLine("{0} {1} Connect from {2}", DateTime.Now, connectClient.Client.GetHashCode(), connectClient.Client.RemoteEndPoint);

                Task task = Task.Run(() =>
                {
                    ProcessingData(connectClient);
                    connectClient.Close();
                });
            }
        }

        private void ProcessingData(TcpClient connectClient)
        {
            byte[] buff = new byte[4096];  // データは4096バイトまで

            StringBuilder sb = new StringBuilder();

            sb.Clear();

            using (connectClient)
            {
                using (NetworkStream stream = connectClient.GetStream())
                {
                    // Node-REDからのリクエストを読み出す
                    int buffIndex = 0;
                    int data;

                    while (buff.Length > buffIndex)
                    {
                        data = stream.ReadByte();

                        if ((-1 == data) || ('\n' == data) || ('\r' == data)) break;

                        buff[buffIndex] = Convert.ToByte(data);
                        buffIndex++;
                    }
                    sb.Append(Encoding.UTF8.GetString(buff, 0, buffIndex));
                    Console.WriteLine("{0} {1} Received Data:{2}", DateTime.Now, connectClient.Client.GetHashCode(), sb.ToString());


                    // リクエストデータを本来のサービスへ送る

                    string dummyData;
                    try
                    {
                        proxyClient proClient = new proxyClient(remoteEP);
                        proClient.Send(sb.ToString() + "\n");
                        dummyData = "{\"status\": \"OK\", \"data\":" + sb.ToString() + "}";
                    }
                    catch (Exception e)
                    {
                        dummyData = "{\"status\": \"NG\", \"error\":" + e.Message + "}";
                    }

                    // Node-REDへダミーのレスポンスを返す

                    byte[] sendData = System.Text.Encoding.UTF8.GetBytes(dummyData + "\n");
                    stream.Write(sendData, 0, sendData.Length);
                    Console.WriteLine("{0} {1} Return Dummy Response:{2}", DateTime.Now, connectClient.Client.GetHashCode(), dummyData);
                }
            }
        }

    }
}