ln.http/websocket/WebSocket.cs

using System;
using System.IO;
using System.Threading;
using ln.logging;
using ln.http.exceptions;
using System.Security.Cryptography;
using System.Text;
using ln.types;
using ln.http.connections;

namespace ln.http.websocket
{
    public enum WebSocketOpcode : int
    {
        CONTINUATION = 0x00,
        TEXT = 0x01,
        BINARY = 0x02,
        CLOSE = 0x08,
        PING = 0x09,
        PONG = 0x0A,

        INVALIDOPCODE = -1
    }

    public enum WebSocketState
    {
        HANDSHAKE,
        OPEN,
        CLOSING,
        CLOSED,
        ERROR
    }

    public delegate void WebSocketEventDelegate(WebSocket sender,WebSocketEventArgs e);


    public abstract class WebSocket
    {
        public HTTPServer HTTPServer => HttpRequest.HTTPServer;
        public HttpRequest HttpRequest { get; }
        public Stream Stream { get; }

        public WebSocketState State { get; private set; } = WebSocketState.HANDSHAKE;

        public WebSocket(HttpRequest httpRequest)
        {
            HttpRequest = httpRequest;
            Stream = httpRequest.GetConnectionStream();

            if ((!httpRequest.GetRequestHeader("upgrade", "").Contains("websocket")) && (!httpRequest.GetRequestHeader("connection", "").Contains("Upgrade")))
                throw new HttpException(400, "This resource is a websocket endpoint only");

            if (!httpRequest.GetRequestHeader("Sec-WebSocket-Version", "").Equals("13"))
                throw new HttpException(400, "Unsupported Protocol Version (WebSocket)");

            String wsKey = httpRequest.GetRequestHeader("Sec-WebSocket-Key");

            HttpResponse httpResponse = new HttpResponse(httpRequest);
            httpResponse.StatusCode = 101;
            httpResponse.StatusMessage = "Switching Protocols";
            httpResponse.AddHeader("upgrade", "websocket");
            httpResponse.AddHeader("connection", "Upgrade");
            httpResponse.AddHeader("Sec-WebSocket-Version", "13");

            string acceptKey = String.Format("{0}258EAFA5-E914-47DA-95CA-C5AB0DC85B11", httpRequest.GetRequestHeader("Sec-WebSocket-Key"));

            httpResponse.AddHeader(
                "Sec-Websocket-Accept",
                Convert.ToBase64String(SHA1.Create().ComputeHash(Encoding.ASCII.GetBytes(acceptKey)))
                );

            Connection.SendResponse(Stream, httpResponse);
            //HTTPServerConnection.Current.Value.AbortRequested += (connection) => Close();
            State = WebSocketState.OPEN;
        }

        public bool IsAlive => false;

        public void Close()
        {
            switch (State)
            {
                case WebSocketState.HANDSHAKE:
                case WebSocketState.ERROR:
                case WebSocketState.CLOSING:
                    State = WebSocketState.CLOSED;
                    Stream.Close();
                    break;
                case WebSocketState.CLOSED:
                    break;
                case WebSocketState.OPEN:
                    WebSocketFrame closeFrame = new WebSocketFrame(WebSocketOpcode.CLOSE);
                    lock (Stream)
                    {
                        Send(closeFrame);
                        State = WebSocketState.CLOSING;
                    }
                    break;
            }
        }

        public void Run()
        {
            try
            {
                while (State != WebSocketState.CLOSED)
                {
                    WebSocketFrame webSocketFrame = new WebSocketFrame(Stream);
                    switch (webSocketFrame.Opcode)
                    {
                        case WebSocketOpcode.TEXT:
                            Received(Encoding.UTF8.GetString(webSocketFrame.ApplicationData));
                            break;
                        case WebSocketOpcode.BINARY:
                            Received(webSocketFrame.ApplicationData);
                            break;
                        case WebSocketOpcode.CLOSE:
                            if (State == WebSocketState.OPEN)
                            {
                                WebSocketFrame closeFrame = new WebSocketFrame(WebSocketOpcode.CLOSE);
                                closeFrame.FIN = true;
                                lock (Stream)
                                {
                                    Send(closeFrame);
                                    State = WebSocketState.CLOSING;
                                }
                            }

                            State = WebSocketState.CLOSED;
                            Stream.Close();
                            break;
                        case WebSocketOpcode.PING:
                            WebSocketFrame pong = new WebSocketFrame(WebSocketOpcode.PONG);
                            pong.ApplicationData = webSocketFrame.ApplicationData;
                            Send(pong);
                            break;
                    }
                }
            } catch (IOException)
            {
                State = WebSocketState.ERROR;
                Logging.Log(LogLevel.DEBUG, "WebSocket connection was dropped unexpected");
                Close();
            } catch (Exception e)
            {
                Logging.Log(LogLevel.ERROR, "WebSocket caught Exception: {0}", e.ToString());
                Logging.Log(e);
            } finally
			{
			}
        }

        public virtual bool Received(string textMessage)
        {
            Logging.Log(LogLevel.WARNING, "WebSocket received unexpected text message:\n{0}", textMessage);
            return false;
        }
        public virtual bool Received(byte[] binaryMessage)
        {
            Logging.Log(LogLevel.WARNING, "WebSocket received unexpected binary message:\n{0}",binaryMessage.ToHexString());
            return false;
        }

        public void Send(WebSocketFrame frame)
        {
            lock (Stream)
            {
                if (State == WebSocketState.OPEN)
                {
                    try
                    {
                        frame.WriteTo(Stream);
                    } catch (IOException)
                    {
                        if (State != WebSocketState.ERROR)
                        {
                            Logging.Log(LogLevel.ERROR, "WebSocket.Send(): Websocket connection was dropped unexpected");
                            State = WebSocketState.ERROR;
                            Close();
                        }
                    }
                }
                else
                    throw new IOException("WebSocket is not open");
            }
        }

        public void Send(string textMessage)
        {
            WebSocketFrame webSocketFrame = new WebSocketFrame(textMessage);
            Send(webSocketFrame);
        }
        public void Send(byte[] binaryMessage)
        {
            WebSocketFrame webSocketFrame = new WebSocketFrame(binaryMessage);
            Send(webSocketFrame);
        }



    }
}