/*
    * ====================================================================
    * 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.testing.async;
  
  import org.apache.hc.core5.function.Resolver;
  import org.apache.hc.core5.http.EntityDetails;
  import org.apache.hc.core5.http.Header;
  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.HttpVersion;
  import org.apache.hc.core5.http.ProtocolVersion;
  import org.apache.hc.core5.http.message.BasicHttpResponse;
  import org.apache.hc.core5.http.nio.AsyncServerExchangeHandler;
  import org.apache.hc.core5.http.nio.CapacityChannel;
  import org.apache.hc.core5.http.nio.DataStreamChannel;
  import org.apache.hc.core5.http.nio.ResponseChannel;
  import org.apache.hc.core5.http.protocol.HttpContext;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.TimeValue;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  public class ServiceUnavailableAsyncDecorator implements AsyncServerExchangeHandler {
  
      private final AsyncServerExchangeHandler exchangeHandler;
      private final Resolver<HttpRequest, TimeValue> serviceAvailabilityResolver;
      private final AtomicBoolean serviceUnavailable;
  
      public ServiceUnavailableAsyncDecorator(final AsyncServerExchangeHandler exchangeHandler,
                                              final Resolver<HttpRequest, TimeValue> serviceAvailabilityResolver) {
          this.exchangeHandler = Args.notNull(exchangeHandler, "Exchange handler");
          this.serviceAvailabilityResolver = Args.notNull(serviceAvailabilityResolver, "Service availability resolver");
          this.serviceUnavailable = new AtomicBoolean();
      }
  
      @Override
      public void handleRequest(final HttpRequest request,
                                final EntityDetails entityDetails,
                                final ResponseChannel responseChannel,
                                final HttpContext context) throws HttpException, IOException {
          final TimeValue retryAfter = serviceAvailabilityResolver.resolve(request);
          serviceUnavailable.set(TimeValue.isPositive(retryAfter));
          if (serviceUnavailable.get()) {
              final HttpResponse response = new BasicHttpResponse(HttpStatus.SC_SERVICE_UNAVAILABLE);
              response.addHeader(HttpHeaders.RETRY_AFTER, Long.toString(retryAfter.toSeconds()));
              final ProtocolVersion version = request.getVersion();
              if (version != null && version.compareToVersion(HttpVersion.HTTP_2) < 0) {
                  response.addHeader(HttpHeaders.CONNECTION, "Close");
              }
              responseChannel.sendResponse(response, null, context);
          } else {
              exchangeHandler.handleRequest(request, entityDetails, responseChannel, context);
          }
      }
  
      @Override
      public final void updateCapacity(final CapacityChannel capacityChannel) throws IOException {
          if (!serviceUnavailable.get()) {
              exchangeHandler.updateCapacity(capacityChannel);
          } else {
              capacityChannel.update(Integer.MAX_VALUE);
          }
      }
  
      @Override
      public final void consume(final ByteBuffer src) throws IOException {
          if (!serviceUnavailable.get()) {
              exchangeHandler.consume(src);
         }
     }
 
     @Override
     public final void streamEnd(final List<? extends Header> trailers) throws HttpException, IOException {
         if (!serviceUnavailable.get()) {
             exchangeHandler.streamEnd(trailers);
         }
     }
 
     @Override
     public int available() {
         if (!serviceUnavailable.get()) {
             return exchangeHandler.available();
         } else {
             return 0;
         }
     }
 
     @Override
     public void produce(final DataStreamChannel channel) throws IOException {
         if (!serviceUnavailable.get()) {
             exchangeHandler.produce(channel);
         }
     }
 
     @Override
     public void failed(final Exception cause) {
         if (!serviceUnavailable.get()) {
             exchangeHandler.failed(cause);
         }
     }
 
     @Override
     public void releaseResources() {
         exchangeHandler.releaseResources();
     }
 
 }