/**
    * This file Copyright (c) 2008-2015 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.module.cache.executor;
  
  import info.magnolia.cms.cache.CacheConstants;
  import info.magnolia.module.cache.BrowserCachePolicy;
  import info.magnolia.module.cache.BrowserCachePolicyResult;
  import info.magnolia.module.cache.Cache;
  import info.magnolia.module.cache.CachePolicyResult;
  import info.magnolia.module.cache.filter.CachedEntry;
  
  import java.io.IOException;
  
  import javax.servlet.FilterChain;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  /**
   * Executor for setting expiration headers to response.
   */
  public class SetExpirationHeaders extends AbstractExecutor {
  
      @Override
      public void processCacheRequest(HttpServletRequest request,
              HttpServletResponse response, FilterChain chain, Cache cache,
              CachePolicyResult cachePolicyResult) throws IOException, ServletException {
  
          BrowserCachePolicy browserCachePolicy = this.getContentCachingConfiguration().getBrowserCachePolicy();
          BrowserCachePolicyResult clientCacheResult = browserCachePolicy.canCacheOnClient(cachePolicyResult);
  
          if (clientCacheResult != null) {
              if (clientCacheResult.getExpirationDate() == BrowserCachePolicyResult.NO_CACHE.getExpirationDate()) {
                  response.setHeader(CacheConstants.HEADER_PRAGMA, CacheConstants.HEADER_VALUE_NO_CACHE);
                  response.setHeader(CacheConstants.HEADER_CACHE_CONTROL, CacheConstants.HEADER_CACHE_CONTROL_VALUE_DISABLE_CACHE);
                  response.setDateHeader(CacheConstants.HEADER_EXPIRES, 0L);
              } else {
                  long maxAgeSeconds = (clientCacheResult.getExpirationDate() - System.currentTimeMillis()) / 1000L;
  
                  // browser cache policy cannot set expires longer than what we cached the response for
                  Object cachedEntry = cachePolicyResult != null ? cachePolicyResult.getCachedEntry() : null;
                  if (cachedEntry != null && (cachedEntry instanceof CachedEntry)) {
                      CachedEntry e = (CachedEntry) cachedEntry;
                      int maxAgeFromCachedContent = e.getTimeToLiveInSeconds();
                      if (maxAgeFromCachedContent != -1 && maxAgeFromCachedContent < maxAgeSeconds)
                          maxAgeSeconds = maxAgeFromCachedContent;
                  }
  
                  response.setHeader(CacheConstants.HEADER_CACHE_CONTROL, CacheConstants.HEADER_VALUE_MAX_AGE + "=" + maxAgeSeconds + ", " + CacheConstants.HEADER_VALUE_PUBLIC);
                  response.setDateHeader(CacheConstants.HEADER_EXPIRES, System.currentTimeMillis() + maxAgeSeconds * 1000);
              }
          }
      }
  }