/*
    * ====================================================================
    * 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.ArrayList;
  import java.util.List;
  
  import org.apache.hc.client5.http.cache.RequestCacheControl;
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.Internal;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.http.Header;
  import org.apache.hc.core5.http.HttpHeaders;
  import org.apache.hc.core5.http.HttpMessage;
  import org.apache.hc.core5.http.NameValuePair;
  import org.apache.hc.core5.http.message.BasicHeader;
  import org.apache.hc.core5.http.message.BasicHeaderValueFormatter;
  import org.apache.hc.core5.http.message.BufferedHeader;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.CharArrayBuffer;
  
  @Internal
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  class CacheControlHeaderGenerator {
  
      /**
       * Default instance of {@link CacheControlHeaderGenerator}.
       */
      public static final CacheControlHeaderGenerator INSTANCE = new CacheControlHeaderGenerator();
  
      public List<NameValuePair> convert(final RequestCacheControl cacheControl) {
          Args.notNull(cacheControl, "Cache control");
          final List<NameValuePair> params = new ArrayList<>(10);
          if (cacheControl.getMaxAge() >= 0) {
              params.add(new BasicHeader("max-age", cacheControl.getMaxAge()));
          }
          if (cacheControl.getMaxStale() >= 0) {
              params.add(new BasicHeader("max-stale", cacheControl.getMaxStale()));
          }
          if (cacheControl.getMinFresh() >= 0) {
              params.add(new BasicHeader("min-fresh", cacheControl.getMinFresh()));
          }
          if (cacheControl.isNoCache()) {
              params.add(new BasicHeader("no-cache", null));
          }
          if (cacheControl.isNoStore()) {
              params.add(new BasicHeader("no-store", null));
          }
          if (cacheControl.isOnlyIfCached()) {
              params.add(new BasicHeader("only-if-cached", null));
          }
          if (cacheControl.getStaleIfError() >= 0) {
              params.add(new BasicHeader("stale-if-error", cacheControl.getStaleIfError()));
          }
          return params;
      }
  
      public Header generate(final RequestCacheControl cacheControl) {
          final List<NameValuePair> params = convert(cacheControl);
          if (!params.isEmpty()) {
              final CharArrayBuffer buf = new CharArrayBuffer(1024);
              buf.append(HttpHeaders.CACHE_CONTROL);
              buf.append(": ");
              for (int i = 0; i < params.size(); i++) {
                  if (i > 0) {
                      buf.append(", ");
                  }
                  BasicHeaderValueFormatter.INSTANCE.formatNameValuePair(buf, params.get(i), false);
              }
              return BufferedHeader.create(buf);
          }
          return null;
      }
  
      public void generate(final RequestCacheControl cacheControl, final HttpMessage message) {
         final Header h = generate(cacheControl);
         if (h != null) {
             message.addHeader(h);
         }
     }
 
 }