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/*
 * Copyright (c) 2015 EXILANT Technologies Private Limited (www.exilant.com)
 * Copyright (c) 2016 simplity.org
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package org.simplity.http;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.simplity.kernel.FormattedMessage;
import org.simplity.kernel.MessageType;
import org.simplity.kernel.Tracer;

/**
 * this is an example servlet to demonstrate how a project can use HttpAgent to
 * deliver services in the App layer to http clients
 *
 * @author simplity.org
 *
 */
public class Serve extends HttpServlet {

	/*
	 * we may have to co-exist with other application. It is possible that our
	 * start-up never started. One check may not be too expensive. Our start-up
	 * calls keep this as marker..
	 */
	private static boolean startedUp = false;
	private static boolean startUpFailed = false;
	/*
	 * of course we will have several other issues like logging....
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * notify that the start-up is successful, and we can go ahead and serve
	 *
	 * @param succeeded
	 *            Success flag
	 */
	public static void updateStartupStatus(boolean succeeded) {
		if (succeeded) {
			startedUp = true;
			Tracer.trace("Web Agent is given a green signal by Startup to start serving.");
		} else {
			startUpFailed = true;
			Tracer.trace("Web agent Serve will not be available on this server as Startup reported a failure on boot-strap.");
		}
	}

	/**
	 * post is to be used by client in AJAX call.
	 */
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		if (startedUp == false) {
			if (startUpFailed == false) {
				Startup.bootStrap(this.getServletContext());
			}
			if (startUpFailed) {
				/*
				 * application had error during bootstrap.
				 */
				this.reportError(
						resp,
						"Application start-up had an error. Please refer to the logs. No service is possible.");
				return;
			}
		}
		try {
			HttpAgent.serve(req, resp);
		} catch (Exception e) {
			String msg = "We have an internal error. ";
			String trace = Tracer.stopAccumulation();
			Tracer.trace(trace);
			Tracer.trace(e, msg);
			this.reportError(resp, msg + e.getMessage());
		}
	}

	/**
	 * Get is to be used ONLY IF POST is not possible for some reason. From
	 * security angle POST is preferred
	 */
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		this.doPost(req, resp);
	}

	private void reportError(HttpServletResponse resp, String msg)
			throws IOException {
		Tracer.trace(msg);
		FormattedMessage message = new FormattedMessage("internalerror",
				MessageType.ERROR, msg);
		FormattedMessage[] messages = { message };
		String response = HttpAgent.getResponseForError(messages);
		resp.getWriter().write(response);
	}
}