/*
    * ====================================================================
    * 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 java.nio.ByteBuffer;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.hc.core5.concurrent.CallbackContribution;
  import org.apache.hc.core5.concurrent.FutureCallback;
  import org.apache.hc.core5.function.Supplier;
  import org.apache.hc.core5.http.ContentType;
  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.HttpRequest;
  import org.apache.hc.core5.http.nio.AsyncEntityConsumer;
  import org.apache.hc.core5.http.nio.AsyncRequestConsumer;
  import org.apache.hc.core5.http.nio.CapacityChannel;
  import org.apache.hc.core5.http.protocol.HttpContext;
  import org.apache.hc.core5.util.Args;
  
  /**
   * Abstract asynchronous request consumer that makes use of {@link AsyncEntityConsumer}
   * to process request message content.
   *
   * @param <T> request processing result representation.
   * @param <E> request entity representation.
   *
   * @since 5.0
   */
  public abstract class AbstractAsyncRequesterConsumer<T, E> implements AsyncRequestConsumer<T> {
  
      private final Supplier<AsyncEntityConsumer<E>> dataConsumerSupplier;
      private final AtomicReference<AsyncEntityConsumer<E>> dataConsumerRef;
  
      public AbstractAsyncRequesterConsumer(final Supplier<AsyncEntityConsumer<E>> dataConsumerSupplier) {
          this.dataConsumerSupplier = Args.notNull(dataConsumerSupplier, "Data consumer supplier");
          this.dataConsumerRef = new AtomicReference<>(null);
      }
  
      public AbstractAsyncRequesterConsumer(final AsyncEntityConsumer<E> dataConsumer) {
          this(new Supplier<AsyncEntityConsumer<E>>() {
  
              @Override
              public AsyncEntityConsumer<E> get() {
                  return dataConsumer;
              }
  
          });
      }
  
      /**
       * Triggered to generate object that represents a result of request message processing.
       * @param request the request message.
       * @param entity the request entity.
       * @param contentType the request content type.
       * @return the result of request processing.
       */
      protected abstract T buildResult(HttpRequest request, E entity, ContentType contentType);
  
      @Override
      public final void consumeRequest(
              final HttpRequest request,
              final EntityDetails entityDetails,
              final HttpContext httpContext, final FutureCallback<T> resultCallback) throws HttpException, IOException {
          if (entityDetails != null) {
              final AsyncEntityConsumer<E> dataConsumer = dataConsumerSupplier.get();
              if (dataConsumer == null) {
                  throw new HttpException("Supplied data consumer is null");
              }
              dataConsumerRef.set(dataConsumer);
              dataConsumer.streamStart(entityDetails, new CallbackContribution<E>(resultCallback) {
 
                 @Override
                 public void completed(final E entity) {
                     final ContentType contentType;
                     try {
                         contentType = ContentType.parse(entityDetails.getContentType());
                         final T result = buildResult(request, entity, contentType);
                         resultCallback.completed(result);
                     } catch (final UnsupportedCharsetException ex) {
                         resultCallback.failed(ex);
                     }
                 }
 
             });
         } else {
             resultCallback.completed(buildResult(request, null, null));
         }
 
     }
 
     @Override
     public final void updateCapacity(final CapacityChannel capacityChannel) throws IOException {
         final AsyncEntityConsumer<E> dataConsumer = dataConsumerRef.get();
         dataConsumer.updateCapacity(capacityChannel);
     }
 
     @Override
     public final void consume(final ByteBuffer src) throws IOException {
         final AsyncEntityConsumer<E> dataConsumer = dataConsumerRef.get();
         dataConsumer.consume(src);
     }
 
     @Override
     public final void streamEnd(final List<? extends Header> trailers) throws HttpException, IOException {
         final AsyncEntityConsumer<E> dataConsumer = dataConsumerRef.get();
         dataConsumer.streamEnd(trailers);
     }
 
     @Override
     public final void failed(final Exception cause) {
         releaseResources();
     }
 
     @Override
     public final void releaseResources() {
         final AsyncEntityConsumer<E> dataConsumer = dataConsumerRef.getAndSet(null);
         if (dataConsumer != null) {
             dataConsumer.releaseResources();
         }
     }
 
 }