/*
    * ====================================================================
    * 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.hc.client5.http.impl.cache;
  
  import java.util.Iterator;
  
  import org.apache.hc.client5.http.cache.HeaderConstants;
  import org.apache.hc.core5.http.HeaderElement;
  import org.apache.hc.core5.http.HttpRequest;
  import org.apache.hc.core5.http.HttpVersion;
  import org.apache.hc.core5.http.ProtocolVersion;
  import org.apache.hc.core5.http.message.MessageSupport;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Determines if an HttpRequest is allowed to be served from the cache.
   */
  class CacheableRequestPolicy {
  
      private static final Logger LOG = LoggerFactory.getLogger(CacheableRequestPolicy.class);
  
      /**
       * 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.getMethod();
  
          final ProtocolVersion pv = request.getVersion() != null ? request.getVersion() : HttpVersion.DEFAULT;
          if (HttpVersion.HTTP_1_1.compareToVersion(pv) != 0) {
              LOG.debug("non-HTTP/1.1 request is not serveable from cache");
              return false;
          }
  
          if (!method.equals(HeaderConstants.GET_METHOD) && !method.equals(HeaderConstants.HEAD_METHOD)) {
              if (LOG.isDebugEnabled()) {
                  LOG.debug("{} request is not serveable from cache", method);
              }
              return false;
          }
  
          if (request.countHeaders(HeaderConstants.PRAGMA) > 0) {
              LOG.debug("request with Pragma header is not serveable from cache");
              return false;
          }
  
          final Iterator<HeaderElement> it = MessageSupport.iterate(request, HeaderConstants.CACHE_CONTROL);
          while (it.hasNext()) {
              final HeaderElement cacheControlElement = it.next();
              if (HeaderConstants.CACHE_CONTROL_NO_STORE.equalsIgnoreCase(cacheControlElement.getName())) {
                  LOG.debug("Request with no-store is not serveable from cache");
                  return false;
              }
              if (HeaderConstants.CACHE_CONTROL_NO_CACHE.equalsIgnoreCase(cacheControlElement.getName())) {
                  LOG.debug("Request with no-cache is not serveable from cache");
                  return false;
              }
          }
  
          LOG.debug("Request is serveable from cache");
          return true;
      }
  
  }