package flowersinthesand.example;



import java.io.IOException;

import java.io.PrintWriter;

import java.util.LinkedHashMap;

import java.util.Map;

import java.util.UUID;

import java.util.concurrent.BlockingQueue;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.LinkedBlockingQueue;



import javax.servlet.AsyncContext;

import javax.servlet.AsyncEvent;

import javax.servlet.AsyncListener;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;



import com.google.gson.Gson;



public class HttpChatServlet extends HttpServlet {



	private static final long serialVersionUID = -8823775068689773674L;



	/* Common */

	private BlockingQueue<String> messages = new LinkedBlockingQueue<String>();

	private Thread notifier = new Thread(new Runnable() {

		public void run() {

			boolean done = false;

			while (!done) {

				try {

					String message = messages.take();

					for (AsyncContext asyncContext : asyncContexts.values()) {

						try {

							// Message

							PrintWriter writer = asyncContext.getResponse().getWriter();

							writer.print(message.length());

							writer.print(";");

							writer.print(message);

							writer.print(";");

							writer.flush();

						} catch (Exception e) {

							asyncContexts.values().remove(asyncContext);

						}

					}

				} catch (InterruptedException e) {

					done = true;

				}

			}

		}

	});



	@Override

	public void init(ServletConfig config) throws ServletException {

		super.init(config);

		notifier.start();

	}



	@Override

	public void destroy() {

		messages.clear();

		asyncContexts.clear();

		notifier.interrupt();

	}



	/* HTTP Streaming powered by Servlet 3.0 */

	private Map<String, AsyncContext> asyncContexts = new ConcurrentHashMap<String, AsyncContext>();



	// GET method is used to open stream

	@Override

	protected void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		// Wrong access

		if ("websocket".equalsIgnoreCase(request.getHeader("Upgrade"))) {

			response.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED);

			return;

		}



		response.setCharacterEncoding("utf-8");



		// Content-Type header

		response.setContentType("text/plain");



		// Access-Control-Allow-Origin header

		response.setHeader("Access-Control-Allow-Origin", "*");



		PrintWriter writer = response.getWriter();



		// Id

		final String id = UUID.randomUUID().toString();

		writer.print(id);

		writer.print(';');



		// Padding

		for (int i = 0; i < 1024; i++) {

			writer.print(' ');

		}

		writer.print(';');

		writer.flush();



		final AsyncContext ac = request.startAsync();

		ac.setTimeout(5 * 60 * 1000);

		ac.addListener(new AsyncListener() {

			public void onComplete(AsyncEvent event) throws IOException {

				asyncContexts.remove(id);

			}



			public void onTimeout(AsyncEvent event) throws IOException {

				asyncContexts.remove(id);

			}



			public void onError(AsyncEvent event) throws IOException {

				asyncContexts.remove(id);

			}



			public void onStartAsync(AsyncEvent event) throws IOException {



			}

		});

		asyncContexts.put(id, ac);

	}



	// POST method is used to handle data sent by user through the stream

	@Override

	protected void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		request.setCharacterEncoding("utf-8");



		if ("close".equals(request.getParameter("metadata.type"))) {

			AsyncContext ac = asyncContexts.get(request.getParameter("metadata.id"));

			if (ac != null) {

				ac.complete();

			}



			return;

		}



		// Handles data sent from a client

		Map<String, String> data = new LinkedHashMap<String, String>();

		data.put("username", request.getParameter("username"));

		data.put("message", request.getParameter("message"));



		try {

			messages.put(new Gson().toJson(data));

		} catch (InterruptedException e) {

			throw new IOException(e);

		}

	}



}