/*
    * ====================================================================
    * 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.classic;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.UnsupportedEncodingException;
  import java.nio.ByteBuffer;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.List;
  import java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.hc.core5.concurrent.FutureCallback;
  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.nio.AsyncEntityConsumer;
  import org.apache.hc.core5.http.nio.CapacityChannel;
  import org.apache.hc.core5.util.Args;
  
  /**
   * {@link AsyncEntityConsumer} implementation that acts as a compatibility
   * layer for classic {@link InputStream} based interfaces. Blocking input
   * processing is executed through an {@link Executor}.
   *
   * @param <T> entity representation.
   *
   * @since 5.0
   */
  public abstract class AbstractClassicEntityConsumer<T> implements AsyncEntityConsumer<T> {
  
      private enum State { IDLE, ACTIVE, COMPLETED }
  
      private final Executor executor;
      private final SharedInputBuffer buffer;
      private final AtomicReference<State> state;
      private final AtomicReference<T> resultRef;
      private final AtomicReference<Exception> exceptionRef;
  
      public AbstractClassicEntityConsumer(final int initialBufferSize, final Executor executor) {
          this.executor = Args.notNull(executor, "Executor");
          this.buffer = new SharedInputBuffer(initialBufferSize);
          this.state = new AtomicReference<>(State.IDLE);
          this.resultRef = new AtomicReference<>();
          this.exceptionRef = new AtomicReference<>();
      }
  
      /**
       * Processes entity data from the given stream.
       *
       * @param contentType the entity content type
       * @param inputStream the input stream
       * @return the result of entity processing.
       */
      protected abstract T consumeData(ContentType contentType, InputStream inputStream) throws IOException;
  
      @Override
      public final void updateCapacity(final CapacityChannel capacityChannel) throws IOException {
          buffer.updateCapacity(capacityChannel);
      }
  
      @Override
      public final void streamStart(final EntityDetails entityDetails, final FutureCallback<T> resultCallback) throws HttpException, IOException {
          final ContentType contentType;
          try {
              contentType = ContentType.parse(entityDetails.getContentType());
          } catch (final UnsupportedCharsetException ex) {
              throw new UnsupportedEncodingException(ex.getMessage());
          }
          if (state.compareAndSet(State.IDLE, State.ACTIVE)) {
              executor.execute(() -> {
                  try {
                      final T result = consumeData(contentType, new ContentInputStream(buffer));
                     resultRef.set(result);
                     resultCallback.completed(result);
                 } catch (final Exception ex) {
                     buffer.abort();
                     resultCallback.failed(ex);
                 } finally {
                     state.set(State.COMPLETED);
                 }
             });
         }
     }
 
     @Override
     public final void consume(final ByteBuffer src) throws IOException {
         buffer.fill(src);
     }
 
     @Override
     public final void streamEnd(final List<? extends Header> trailers) throws HttpException, IOException {
         buffer.markEndStream();
     }
 
     @Override
     public final void failed(final Exception cause) {
         if (exceptionRef.compareAndSet(null, cause)) {
             releaseResources();
         }
     }
 
     public final Exception getException() {
         return exceptionRef.get();
     }
 
     @Override
     public final T getContent() {
         return resultRef.get();
     }
 
     @Override
     public void releaseResources() {
     }
 
 }