using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Text.RegularExpressions;
using System.Security;
using System.Security.Cryptography;

namespace WebSock
{
    class Program
    {
        static void server_thread()
        {
            EndPoint server_end_point = new IPEndPoint(IPAddress.Any, 8080);
            IPAddress ipAd = IPAddress.Any; //use local m/c IP address, and use the same in the client
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            socket.Bind(new IPEndPoint(ipAd, 8080));

            bool connected = false;

            while (true)
            {
                socket.Listen(1);


                Socket s = socket.Accept();
                Console.WriteLine("Connection accepted from " + s.RemoteEndPoint);
                connected = true;

                while (connected)
                {
                    byte[] b = new byte[512];
                    if (s.Receive(b) > 0)
                    {
                        string input = Encoding.ASCII.GetString(b);
                        Console.WriteLine("Recived: " + input);

                        string get_regexp = @"GET\s([^\s]+)\sHTTP([^\r\n]+)\r\n";
                        string host_regexp = @"HOST:\s([^\r\n]+)\r\n";
                        string key1_regexp = @"Sec-WebSocket-Key1:\s(.*?)\r\n";
                        string key2_regexp = @"Sec-WebSocket-Key2:\s(.*?)\r\n";
                        string protocol_regexp = @"Sec-WebSocket-Protocol: (.*?)\r\n";
                        string origin_regexp = @"Origin: (.*?)\r\n";
                        string code_regexp = @"^(.+)\r\n(.+)$";

                        string resource, httpver, host, key1, key2, protocol = "", origin, code;

                        Match match;

                        match = Regex.Match(input, get_regexp, RegexOptions.IgnoreCase | RegexOptions.Multiline);
                        resource = match.Groups[1].Value;
                        httpver = match.Groups[2].Value;

                        match = Regex.Match(input, host_regexp, RegexOptions.IgnoreCase | RegexOptions.Multiline);
                        host = match.Groups[1].Value;

                        match = Regex.Match(input, key1_regexp, RegexOptions.Multiline | RegexOptions.IgnoreCase);
                        key1 = match.Groups[1].Value;

                        match = Regex.Match(input, key2_regexp, RegexOptions.Multiline | RegexOptions.IgnoreCase);
                        key2 = match.Groups[1].Value;

                        match = Regex.Match(input, protocol_regexp, RegexOptions.Multiline | RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace);
                        if (match.Success)
                            protocol = match.Groups[1].Value;

                        match = Regex.Match(input, code_regexp, RegexOptions.Singleline | RegexOptions.IgnoreCase);
                        code = match.Groups[2].Value;

                        match = Regex.Match(input, origin_regexp, RegexOptions.Multiline | RegexOptions.IgnoreCase);
                        origin = match.Groups[1].Value;

                        string output = "HTTP" + httpver + " 101 WebSocket Protocol Handshake\r\n" +
                            "Upgrade: WebSocket\r\n" +
                            "Connection: Upgrade\r\n" +
                            "Sec-WebSocket-Origin: " + origin + "\r\n" +
                            "Sec-WebSocket-Location: ws://" + host + resource + "\r\n" +
                            (protocol != "" ? "Sec-WebSocket-Protocol: " + protocol + "\r\n" : "") +
                            "\r\n" +
                            create_handshake_code(key1, key2, code);
                        Console.WriteLine("Key11: {0}, Key2: {1}, Code: {2}\r\n", key1, key2, code);

                        Console.WriteLine("Output: " + output);

                        if (resource == "/test")
                        {
                            s.Send(Encoding.ASCII.GetBytes(output));
                            s.Receive(Encoding.ASCII.GetBytes(output));
                        }

                        // s.Send(Encoding.ASCII.GetBytes("Oh snap!"));

                    }
                }
                s.Close();
            }

            socket.Close();
            Console.WriteLine("Stopping server");
        }


        static int _doStuffToObtainAnInt32(string key)
        {
            MatchCollection number = Regex.Matches(key, "[0-9]");
            MatchCollection space = Regex.Matches(key, @"\s");

            if (number.Count > 0 && space.Count > 0)
            {
                string num = "";
                for (int i = 0; i < number.Count; ++i)
                {
                    num += number[i].Value;
                }
                return int.Parse(num) / space.Count;
            }
            else
            {
                return 0;
            }
        }

        static string md5(string str)
        {
            MD5CryptoServiceProvider x = new MD5CryptoServiceProvider();

            byte[] data = Encoding.ASCII.GetBytes(str);

            data = x.ComputeHash(data);

            return System.Text.Encoding.ASCII.GetString(data);
        }

        static string create_handshake_code(string key1, string key2, string code)
        {

            return md5(string.Format("N", _doStuffToObtainAnInt32(key1)) +
                string.Format("N", _doStuffToObtainAnInt32(key2)) +
                code);
        }

        static void Main(string[] args)
        {
            Thread serverThread = new Thread(new ThreadStart(server_thread));
            serverThread.Start();
        }
    }
}