/*
    * ====================================================================
    * 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.nio.support;
  
  import java.io.IOException;
  
  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.Header;
  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.HttpStatus;
  import org.apache.hc.core5.http.message.BasicHttpResponse;
  import org.apache.hc.core5.http.nio.AsyncDataConsumer;
  import org.apache.hc.core5.http.nio.AsyncEntityProducer;
  import org.apache.hc.core5.http.nio.AsyncFilterChain;
  import org.apache.hc.core5.http.nio.AsyncFilterHandler;
  import org.apache.hc.core5.http.protocol.HttpContext;
  
  /**
   * @since 5.0
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  public class AsyncServerExpectationFilter implements AsyncFilterHandler {
  
      protected boolean verify(final HttpRequest request, final HttpContext context) throws HttpException {
          return true;
      }
  
      protected AsyncEntityProducer generateResponseContent(final HttpResponse expectationFailed) throws HttpException {
          return null;
      }
  
      @Override
      public final AsyncDataConsumer handle(
              final HttpRequest request,
              final EntityDetails entityDetails,
              final HttpContext context,
              final AsyncFilterChain.ResponseTrigger responseTrigger,
              final AsyncFilterChain chain) throws HttpException, IOException {
          if (entityDetails != null) {
              final Header h = request.getFirstHeader(HttpHeaders.EXPECT);
              if (h != null && HeaderElements.CONTINUE.equalsIgnoreCase(h.getValue())) {
                  final boolean verified = verify(request, context);
                  if (verified) {
                      responseTrigger.sendInformation(new BasicHttpResponse(HttpStatus.SC_CONTINUE));
                  } else {
                      final HttpResponse expectationFailed = new BasicHttpResponse(HttpStatus.SC_EXPECTATION_FAILED);
                      final AsyncEntityProducer responseContentProducer = generateResponseContent(expectationFailed);
                      responseTrigger.submitResponse(expectationFailed, responseContentProducer);
                      return null;
                  }
              }
          }
          return chain.proceed(request, entityDetails, context, responseTrigger);
      }
  
  }