/*
 * Copyright (C) 2012 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed 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.jboss.errai.bus.server.servlet;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * A servlet filter that inclues the HTTP headers to allow <a
 * href="http://www.html5rocks.com/en/tutorials/cors/">cross-origin resource
 * sharing</a> from browsers that support CORS.
 * <p>
 * This code was adapted from the sample code found at <a href=
 * "http://padcom13.blogspot.com/2011/09/cors-filter-for-java-applications.html"
 * >Matthias Hryniszak's blog</a>. Thanks, Matthias!
 * <p>
 * To use this filter to make a "remote" ErraiBus accessible from a webapp, add
 * this to your web.xml:
 * <p>
 * 
 * <pre>
 *   <filter>
 *     <filter-name>CorsFilter</filter-name>
 *     <filter-class>org.jboss.errai.bus.server.servlet.CorsFilter</filter-class>
 *   </filter>
 *   <filter-mapping>
 *     <filter-name>CorsFilter</filter-name>
 *     <url-pattern>*.erraiBus</url-pattern>
 *   </filter-mapping>
 * </pre>
 * 
 * @author Matthias Hryniszak - original version
 * @author Jonathan Fuerth - updates for Errai
 */
public class CorsFilter implements Filter {

  public CorsFilter() {
  }

  public void init(FilterConfig fc) throws ServletException {
  }

  public void destroy() {
  }

  public void doFilter(ServletRequest request, ServletResponse response,
          FilterChain chain) throws IOException, ServletException {

    HttpServletResponse r = (HttpServletResponse) response;
    String origin = ((HttpServletRequest) request).getHeader("origin");
    r.addHeader("Access-Control-Allow-Origin", origin);
    r.addHeader("Access-Control-Allow-Headers",
            "Accept,Accept-Encoding,Accept-Language,Cache-Control,Connection,Content-Length,Content-Type," +
            "Cookie,Host,Pragma,Referer,RemoteQueueID,User-Agent");
    r.addHeader("Access-Control-Allow-Credentials", "true");
    chain.doFilter(request, response);
  }
}