/*
    * ====================================================================
    * 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.OutputStream;
  import java.util.Objects;
  import java.util.Set;
  import java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.hc.core5.http.ContentType;
  import org.apache.hc.core5.http.nio.AsyncEntityProducer;
  import org.apache.hc.core5.http.nio.DataStreamChannel;
  import org.apache.hc.core5.util.Args;
  
  /**
   * {@link AsyncEntityProducer} implementation that acts as a compatibility
   * layer for classic {@link OutputStream} based interfaces. Blocking output
   * processing is executed through an {@link Executor}.
   *
   * @since 5.0
   */
  public abstract class AbstractClassicEntityProducer implements AsyncEntityProducer {
  
      private enum State { IDLE, ACTIVE, COMPLETED }
  
      private final SharedOutputBuffer buffer;
      private final ContentType contentType;
      private final Executor executor;
      private final AtomicReference<State> state;
      private final AtomicReference<Exception> exception;
  
      public AbstractClassicEntityProducer(final int initialBufferSize, final ContentType contentType, final Executor executor) {
          this.buffer = new SharedOutputBuffer(initialBufferSize);
          this.contentType = contentType;
          this.executor = Args.notNull(executor, "Executor");
          this.state = new AtomicReference<>(State.IDLE);
          this.exception = new AtomicReference<>();
      }
  
      /**
       * Writes out entity data into the given stream.
       *
       * @param contentType the entity content type
       * @param outputStream the output stream
       */
      protected abstract void produceData(ContentType contentType, OutputStream outputStream) throws IOException;
  
      @Override
      public final boolean isRepeatable() {
          return false;
      }
  
      @Override
      public final int available() {
          return buffer.length();
      }
  
      @Override
      public final void produce(final DataStreamChannel channel) throws IOException {
          if (state.compareAndSet(State.IDLE, State.ACTIVE)) {
              executor.execute(() -> {
                  try {
                      produceData(contentType, new ContentOutputStream(buffer));
                      buffer.writeCompleted();
                  } catch (final Exception ex) {
                      buffer.abort();
                  } finally {
                      state.set(State.COMPLETED);
                  }
              });
          }
          buffer.flush(channel);
      }
 
     @Override
     public final long getContentLength() {
         return -1;
     }
 
     @Override
     public final String getContentType() {
         return Objects.toString(contentType, null);
     }
 
     @Override
     public String getContentEncoding() {
         return null;
     }
 
     @Override
     public final boolean isChunked() {
         return false;
     }
 
     @Override
     public final Set<String> getTrailerNames() {
         return null;
     }
 
     @Override
     public final void failed(final Exception cause) {
         if (exception.compareAndSet(null, cause)) {
             releaseResources();
         }
     }
 
     public final Exception getException() {
         return exception.get();
     }
 
     @Override
     public void releaseResources() {
     }
 
 }