/**
    * This file Copyright (c) 2011 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.cms.filters;
  
  import info.magnolia.channel.ChannelConfiguration;
  import info.magnolia.channel.ChannelManager;
  import info.magnolia.channel.ChannelResolver;
  import info.magnolia.cms.core.AggregationState;
  import info.magnolia.cms.core.Channel;
  import info.magnolia.context.MgnlContext;
  
  import java.io.IOException;
  import java.util.Iterator;
  
  import javax.inject.Inject;
  import javax.servlet.FilterChain;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Filter that resolves the site to use by considering variation of the set channel. Resulting site gets set in
   * {@link info.magnolia.cms.core.AggregationState}.
   *
   * @version $Id$
   */
  public class MultiChannelFilter extends OncePerRequestAbstractMgnlFilter {
      private static final Logger log = LoggerFactory.getLogger(MultiChannelFilter.class);
  
      public static String ENFORCE_CHANNEL_PARAMETER = "mgnlChannel";
  
      private ChannelManager channelManager;
  
      @Inject
      public MultiChannelFilter(ChannelManager channelManager) {
          this.channelManager = channelManager;
      }
  
      @Override
      public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
  
          AggregationState aggregationState = MgnlContext.getAggregationState();
  
          final Channel channel = new Channel();
          channel.setName(resolveChannel(request));
  
          aggregationState.setChannel(channel);
  
          chain.doFilter(request, response);
      }
  
      protected String resolveChannel(HttpServletRequest request) {
          String channelName;
          final String channelParameterValue = MgnlContext.getAttribute(ENFORCE_CHANNEL_PARAMETER);
          if (channelParameterValue != null) {
              channelName = channelParameterValue;
          } else {
              channelName = ChannelResolver.UNRESOLVED;
              final Iterator<ChannelConfiguration> channelConfigIterator =
                      channelManager.getChannels().values().iterator();
  
              ChannelConfiguration currentChannelConfig;
              ChannelResolver resolver;
              // proceed as long as it could not be resolved - first match wins
              while (channelConfigIterator.hasNext() && channelName == ChannelResolver.UNRESOLVED) {
                 currentChannelConfig = channelConfigIterator.next();
                 resolver = currentChannelConfig.getResolver();
 
                 if (resolver != null) {
                     channelName = resolver.resolveChannel(request);
                     log.debug("Type {} resolved channel to '{}'", resolver.getClass().getName(), channelName);
                 }
             }
         }
 
         return channelName == ChannelResolver.UNRESOLVED ? ChannelResolver.ALL : channelName;
     }
 }