/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.    
 */

package org.apache.tuscany.sca.binding.comet.runtime;

import org.apache.tuscany.sca.host.http.ServletHost;
import org.atmosphere.cpr.AtmosphereServlet;

/**
 * This class adds two servlets to the runtime: one exposing all the comet
 * services, the other one exposing the javascript toolkit.
 * 
 * Exposing all comet services through a single servlet is needed as browsers
 * are undergone by the two http connection limit per domain so all comet
 * services should send their responses via the same http connection to a single
 * client.
 * 
 * Dispatching to the corresponding endpoint and operation is done internally
 * using Jersey RESTful Web Services integration with the AtmosphereServlet.
 * 
 * The Javascript toolkit is not tied to any of the services so it is exposed by
 * a separate servlet.
 */
public final class ServletFactory {

    /**
     * Init-param key for the AtmosphereServlet defining where to look for
     * Jersey classes.
     */
    private static final String PACKAGE_KEY = "com.sun.jersey.config.property.packages";

    /**
     * Package of the class handling dispatching to endpoints.
     */
    private static final String HANDLER_PACKAGE = "org.apache.tuscany.sca.binding.comet.runtime.handler";

    /**
     * Package of the class handling Javascript toolkit retrieval.
     */
    private static final String JS_PACKAGE = "org.apache.tuscany.sca.binding.comet.runtime.javascript";

    /**
     * Init-param key for Atmosphere filters.
     */
    private static final String FILTERS_KEY = "org.atmosphere.cpr.broadcastFilterClasses";

    /**
     * Defined filters.
     */
    private static final String FILTERS = "org.atmosphere.client.JavascriptClientFilter";

    /**
     * Path where services will be exposed.
     */
    public static final String PATH = "/tuscany-comet/*";

    /**
     * Path where Javascript toolkit will be exposed.
     */
    public static final String JS_PATH = "/tuscany-comet-js/*";

    /**
     * The servlet that is exposing the comet services.
     */
    private static AtmosphereServlet cometServlet = null;

    /**
     * The servlet that is exposing the Javascript toolkit.
     */
    private static AtmosphereServlet javascriptServlet = null;

    /**
     * Prevent instantiation of singleton class.
     */
    private ServletFactory() {
    }

    /**
     * Adds servlets to the underlying servlet host. No need for thread safety
     * as calls to this method are sequentially done for each comet endpoint
     * found by the runtime.
     * 
     * @param servletHost
     *            underlying servlet host
     * @return uri where servlet has been mapped
     */
    public static String registerServlet(final ServletHost servletHost) {
        String uri = registerCometServlet(servletHost);
        registerJavascriptServlet(servletHost);
        return uri;
    }

    private static String registerCometServlet(ServletHost servletHost) {
        if (ServletFactory.cometServlet == null) {
            ServletFactory.cometServlet = new AtmosphereServlet();
            ServletFactory.cometServlet.addInitParameter(PACKAGE_KEY, HANDLER_PACKAGE);
//            ServletFactory.cometServlet.addInitParameter(FILTERS_KEY, FILTERS);
            String uri = servletHost.addServletMapping(PATH, cometServlet);
            return uri;
        }
        return null;
    }

    private static void registerJavascriptServlet(ServletHost servletHost) {
        if (ServletFactory.javascriptServlet == null) {
            ServletFactory.javascriptServlet = new AtmosphereServlet();
            ServletFactory.javascriptServlet.addInitParameter(PACKAGE_KEY, JS_PACKAGE);
            servletHost.addServletMapping(JS_PATH, javascriptServlet);
        }
    }

    /**
     * Removes servlets from the servlet host.
     * 
     * @param servletHost
     *            the underlying servlet host.
     */
    public static void unregisterServlet(final ServletHost servletHost) {
        servletHost.removeServletMapping(PATH);
        servletHost.removeServletMapping(JS_PATH);
    }

}