/*
    * ====================================================================
    * 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.protocol;
  
  import java.io.IOException;
  
  import org.apache.hc.client5.http.RouteInfo;
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.http.EntityDetails;
  import org.apache.hc.core5.http.HeaderElements;
  import org.apache.hc.core5.http.HttpException;
  import org.apache.hc.core5.http.HttpHeaders;
  import org.apache.hc.core5.http.HttpRequest;
  import org.apache.hc.core5.http.HttpRequestInterceptor;
  import org.apache.hc.core5.http.Method;
  import org.apache.hc.core5.http.protocol.HttpContext;
  import org.apache.hc.core5.util.Args;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * This protocol interceptor is responsible for adding the {@code Connection}
   * header to the outgoing requests, which is essential for managing persistence
   * of {@code HTTP/1.0} connections.
   *
   * @since 4.0
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  public class RequestClientConnControl implements HttpRequestInterceptor {
  
      private static final Logger LOG = LoggerFactory.getLogger(RequestClientConnControl.class);
  
      public RequestClientConnControl() {
          super();
      }
  
      @Override
      public void process(final HttpRequest request, final EntityDetails entity, final HttpContext context)
              throws HttpException, IOException {
          Args.notNull(request, "HTTP request");
  
          final String method = request.getMethod();
          if (Method.CONNECT.isSame(method)) {
              return;
          }
  
          final HttpClientContext clientContext = HttpClientContext.adapt(context);
          final String exchangeId = clientContext.getExchangeId();
  
          // Obtain the client connection (required)
          final RouteInfo route = clientContext.getHttpRoute();
          if (route == null) {
              if (LOG.isDebugEnabled()) {
                  LOG.debug("{} Connection route not set in the context", exchangeId);
              }
              return;
          }
  
          if (route.getHopCount() == 1 || route.isTunnelled()) {
              if (!request.containsHeader(HttpHeaders.CONNECTION)) {
                  request.addHeader(HttpHeaders.CONNECTION, HeaderElements.KEEP_ALIVE);
              }
          }
      }
  
  }