/*
    * ====================================================================
    * 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.core5.http.protocol;
  
  import java.io.IOException;
  import java.util.Iterator;
  
  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.HeaderElement;
  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.HttpResponse;
  import org.apache.hc.core5.http.HttpResponseInterceptor;
  import org.apache.hc.core5.http.HttpStatus;
  import org.apache.hc.core5.http.HttpVersion;
  import org.apache.hc.core5.http.ProtocolVersion;
  import org.apache.hc.core5.http.message.MessageSupport;
  import org.apache.hc.core5.util.Args;
  
  /**
   * This response interceptor is responsible for adding {@code Connection} header
   * to outgoing responses, which is essential for managing persistence of
   * {@code HTTP/1.0} connections.
   * <p>
   * This interceptor is recommended for the HTTP protocol conformance and
   * the correct operation of the server-side message processing pipeline.
   * </p>
   *
   * @since 4.0
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  public class ResponseConnControl implements HttpResponseInterceptor {
  
      public static final ResponseConnControl INSTANCE = new ResponseConnControl();
  
      public ResponseConnControl() {
          super();
      }
  
      @Override
      public void process(final HttpResponse response, final EntityDetails entity, final HttpContext context)
              throws HttpException, IOException {
          Args.notNull(response, "HTTP response");
          Args.notNull(context, "HTTP context");
  
          // Always drop connection after certain type of responses
          final int status = response.getCode();
          if (status == HttpStatus.SC_BAD_REQUEST ||
                  status == HttpStatus.SC_REQUEST_TIMEOUT ||
                  status == HttpStatus.SC_LENGTH_REQUIRED ||
                  status == HttpStatus.SC_REQUEST_TOO_LONG ||
                  status == HttpStatus.SC_REQUEST_URI_TOO_LONG ||
                  status == HttpStatus.SC_SERVICE_UNAVAILABLE ||
                  status == HttpStatus.SC_NOT_IMPLEMENTED) {
              response.setHeader(HttpHeaders.CONNECTION, HeaderElements.CLOSE);
              return;
          }
          if (!response.containsHeader(HttpHeaders.CONNECTION)) {
              // Always drop connection for HTTP/1.0 responses and below
              // if the content body cannot be correctly delimited
              final ProtocolVersion ver = context.getProtocolVersion();
              if (entity != null && entity.getContentLength() < 0 && ver.lessEquals(HttpVersion.HTTP_1_0)) {
                  response.setHeader(HttpHeaders.CONNECTION, HeaderElements.CLOSE);
              } else {
                  final HttpCoreContext coreContext = HttpCoreContext.adapt(context);
                  final HttpRequest request = coreContext.getRequest();
                  boolean closeRequested = false;
                  boolean keepAliveRequested = false;
                  if (request != null) {
                      final Iterator<HeaderElement> it = MessageSupport.iterate(request, HttpHeaders.CONNECTION);
                     while (it.hasNext()) {
                         final HeaderElement he = it.next();
                         if (he.getName().equalsIgnoreCase(HeaderElements.CLOSE)) {
                             closeRequested = true;
                             break;
                         } else if (he.getName().equalsIgnoreCase(HeaderElements.KEEP_ALIVE)) {
                             keepAliveRequested = true;
                         }
                     }
                 }
                 if (closeRequested) {
                     response.addHeader(HttpHeaders.CONNECTION, HeaderElements.CLOSE);
                 } else {
                     if (response.containsHeader(HttpHeaders.UPGRADE)) {
                         response.addHeader(HttpHeaders.CONNECTION, HeaderElements.UPGRADE);
                     } else {
                         if (keepAliveRequested) {
                             response.addHeader(HttpHeaders.CONNECTION, HeaderElements.KEEP_ALIVE);
                         } else {
                             if (ver.lessEquals(HttpVersion.HTTP_1_0)) {
                                 response.addHeader(HttpHeaders.CONNECTION, HeaderElements.CLOSE);
                             }
                         }
                     }
                 }
             }
         }
     }
 
 }