/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.http.impl.client.cache;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.http.Header;
  import org.apache.http.HeaderElement;
  import org.apache.http.HttpRequest;
  import org.apache.http.HttpVersion;
  import org.apache.http.ProtocolVersion;
  import org.apache.http.annotation.Contract;
  import org.apache.http.annotation.ThreadingBehavior;
  import org.apache.http.client.cache.HeaderConstants;
  
  /**
   * Determines if an HttpRequest is allowed to be served from the cache.
   *
   * @since 4.1
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  class CacheableRequestPolicy {
  
      private final Log log = LogFactory.getLog(getClass());
  
      /**
       * Determines if an HttpRequest can be served from the cache.
       *
       * @param request
       *            an HttpRequest
       * @return boolean Is it possible to serve this request from cache
       */
      public boolean isServableFromCache(final HttpRequest request) {
          final String method = request.getRequestLine().getMethod();
  
          final ProtocolVersion pv = request.getRequestLine().getProtocolVersion();
          if (HttpVersion.HTTP_1_1.compareToVersion(pv) != 0) {
              log.trace("non-HTTP/1.1 request was not serveable from cache");
              return false;
          }
  
          if (!(method.equals(HeaderConstants.GET_METHOD) || method
                  .equals(HeaderConstants.HEAD_METHOD))) {
              log.trace("non-GET or non-HEAD request was not serveable from cache");
              return false;
          }
  
          if (request.getHeaders(HeaderConstants.PRAGMA).length > 0) {
              log.trace("request with Pragma header was not serveable from cache");
              return false;
          }
  
          final Header[] cacheControlHeaders = request.getHeaders(HeaderConstants.CACHE_CONTROL);
          for (final Header cacheControl : cacheControlHeaders) {
              for (final HeaderElement cacheControlElement : cacheControl.getElements()) {
                  if (HeaderConstants.CACHE_CONTROL_NO_STORE.equalsIgnoreCase(cacheControlElement
                          .getName())) {
                      log.trace("Request with no-store was not serveable from cache");
                      return false;
                  }
  
                  if (HeaderConstants.CACHE_CONTROL_NO_CACHE.equalsIgnoreCase(cacheControlElement
                          .getName())) {
                      log.trace("Request with no-cache was not serveable from cache");
                      return false;
                  }
              }
          }
  
          log.trace("Request was serveable from cache");
          return true;
      }
  
  }