using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web;
using System.Web.Http;

// Namespace for Web Sockets classes.
using Microsoft.Web.WebSockets;

namespace Chat.Controllers
{
    public class ChatController : ApiController
    {
        // This function handles HTTP "GET" requests to the URL pattern "api/Chat".
        //   - The client will ping this URL, to indicate it wants to start having a Web Sockets conversation with the server.
        //   - The client will also pass a username parameter, indicating the name of the user (the client web page will get this info from the user).
        public HttpResponseMessage Get(string username)
        {
            // This is how a server in ASP.NET MVC4 says, "Yes, I support Web Sockets". 
            //   - It also creates a "handler" object to handle all subsequent Web Sockets messages from the client.
            HttpContext.Current.AcceptWebSocketRequest(new ChatWebSocketHandler(username));

            // Return an HTTP response to the client to say, "OK then, let's switch our conversation from HTTP to the Web Sockets protocol.
            return Request.CreateResponse(HttpStatusCode.SwitchingProtocols);
        }


        // This is how you implement a Web Sockets handler class in MVC 4.
        //   - Inherit from WebSocketHandler, and handle different types of message from the client.
        //   - Note, there will be a separate instance of this class for every client.
        class ChatWebSocketHandler : WebSocketHandler
        {
            // Keep a collection of all clients that have connected over Web Sockets.
            private static WebSocketCollection _chatClients = new WebSocketCollection();

            // Remember the name of the current user (i.e. the particular client connected to this specific Web Sockets socket).
            private string _username;

            // Constructor, invoked during the initial connection request from the client.
            public ChatWebSocketHandler(string username)
            {
                _username = username;
            }

            // Handle the "Open" event (occurs when the Web Sockets connection has been opened successfully).
            public override void OnOpen()
            {
                // Keep track of all the clients.
                _chatClients.Add(this);
            }

            // Handle the "Message" event (occurs whenever a client sends data to its Web Sockets server socket).
            public override void OnMessage(string message)
            {
                // Broadcast the message to all the clients.
                _chatClients.Broadcast(_username + ": " + message);
            }

            // Handle the "Close" event (occurs when the Web Sockets connection is closed).
            public override void OnClose()
            {
                // Forget this connection.
                _chatClients.Remove(this);

                // Tell all clients that this particular client has left the chat room!
                _chatClients.Broadcast("[" + _username + " has left the chat room]");
            }
        }
    }
}