/*
    * ====================================================================
    * 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.http.nio.protocol;
  
  import java.io.IOException;
  import java.util.concurrent.Future;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.http.ConnectionClosedException;
  import org.apache.http.ConnectionReuseStrategy;
  import org.apache.http.HttpException;
  import org.apache.http.HttpRequest;
  import org.apache.http.HttpResponse;
  import org.apache.http.concurrent.BasicFuture;
  import org.apache.http.concurrent.FutureCallback;
  import org.apache.http.impl.DefaultConnectionReuseStrategy;
  import org.apache.http.nio.ContentDecoder;
  import org.apache.http.nio.ContentEncoder;
  import org.apache.http.nio.IOControl;
  import org.apache.http.nio.NHttpClientConnection;
  import org.apache.http.protocol.HttpContext;
  import org.apache.http.protocol.HttpCoreContext;
  import org.apache.http.protocol.HttpProcessor;
  import org.apache.http.util.Args;
  
  /**
   * Basic implementation of {@link HttpAsyncClientExchangeHandler} that executes
   * a single HTTP request / response exchange.
   *
   * @param <T> the result type of request execution.
   * @since 4.3
   */
  public class BasicAsyncClientExchangeHandler<T> implements HttpAsyncClientExchangeHandler {
  
      private final HttpAsyncRequestProducer requestProducer;
      private final HttpAsyncResponseConsumer<T> responseConsumer;
      private final BasicFuture<T> future;
      private final HttpContext localContext;
      private final NHttpClientConnection conn;
      private final HttpProcessor httpPocessor;
      private final ConnectionReuseStrategy connReuseStrategy;
      private final AtomicBoolean requestSent;
      private final AtomicBoolean keepAlive;
      private final AtomicBoolean closed;
  
      /**
       * Creates new instance of BasicAsyncRequestExecutionHandler.
       *
       * @param requestProducer the request producer.
       * @param responseConsumer the response consumer.
       * @param callback the future callback invoked when the operation is completed.
       * @param localContext the local execution context.
       * @param conn the actual connection.
       * @param httpPocessor the HTTP protocol processor.
       * @param connReuseStrategy the connection re-use strategy.
       */
      public BasicAsyncClientExchangeHandler(
              final HttpAsyncRequestProducer requestProducer,
              final HttpAsyncResponseConsumer<T> responseConsumer,
              final FutureCallback<T> callback,
              final HttpContext localContext,
              final NHttpClientConnection conn,
              final HttpProcessor httpPocessor,
              final ConnectionReuseStrategy connReuseStrategy) {
          super();
          this.requestProducer = Args.notNull(requestProducer, "Request producer");
          this.responseConsumer = Args.notNull(responseConsumer, "Response consumer");
          this.future = new BasicFuture<T>(callback);
          this.localContext = Args.notNull(localContext, "HTTP context");
          this.conn = Args.notNull(conn, "HTTP connection");
          this.httpPocessor = Args.notNull(httpPocessor, "HTTP processor");
          this.connReuseStrategy = connReuseStrategy != null ? connReuseStrategy :
              DefaultConnectionReuseStrategy.INSTANCE;
          this.requestSent = new AtomicBoolean(false);
         this.keepAlive = new AtomicBoolean(false);
         this.closed = new AtomicBoolean(false);
     }
 
     /**
      * Creates new instance of BasicAsyncRequestExecutionHandler.
      *
      * @param requestProducer the request producer.
      * @param responseConsumer the response consumer.
      * @param localContext the local execution context.
      * @param conn the actual connection.
      * @param httpPocessor the HTTP protocol processor.
      */
     public BasicAsyncClientExchangeHandler(
             final HttpAsyncRequestProducer requestProducer,
             final HttpAsyncResponseConsumer<T> responseConsumer,
             final HttpContext localContext,
             final NHttpClientConnection conn,
             final HttpProcessor httpPocessor) {
         this(requestProducer, responseConsumer, null, localContext, conn, httpPocessor, null);
     }
 
     public Future<T> getFuture() {
         return this.future;
     }
 
     private void releaseResources() {
         try {
             this.responseConsumer.close();
         } catch (final IOException ex) {
         }
         try {
             this.requestProducer.close();
         } catch (final IOException ex) {
         }
     }
 
     @Override
     public void close() throws IOException {
         if (this.closed.compareAndSet(false, true)) {
             releaseResources();
             if (!this.future.isDone()) {
                 this.future.cancel();
             }
         }
     }
 
     @Override
     public HttpRequest generateRequest() throws IOException, HttpException {
         if (isDone()) {
             return null;
         }
         final HttpRequest request = this.requestProducer.generateRequest();
         this.localContext.setAttribute(HttpCoreContext.HTTP_REQUEST, request);
         this.localContext.setAttribute(HttpCoreContext.HTTP_CONNECTION, this.conn);
         this.httpPocessor.process(request, this.localContext);
         return request;
     }
 
     @Override
     public void produceContent(
             final ContentEncoder encoder, final IOControl ioControl) throws IOException {
         this.requestProducer.produceContent(encoder, ioControl);
     }
 
     @Override
     public void requestCompleted() {
         this.requestProducer.requestCompleted(this.localContext);
         this.requestSent.set(true);
     }
 
     @Override
     public void responseReceived(final HttpResponse response) throws IOException, HttpException {
         this.localContext.setAttribute(HttpCoreContext.HTTP_RESPONSE, response);
         this.httpPocessor.process(response, this.localContext);
         this.responseConsumer.responseReceived(response);
         this.keepAlive.set(this.connReuseStrategy.keepAlive(response, this.localContext));
     }
 
     @Override
     public void consumeContent(
             final ContentDecoder decoder, final IOControl ioControl) throws IOException {
         this.responseConsumer.consumeContent(decoder, ioControl);
     }
 
     @Override
     public void responseCompleted() throws IOException {
         try {
             if (!this.keepAlive.get()) {
                 this.conn.close();
             }
             this.responseConsumer.responseCompleted(this.localContext);
             final T result = this.responseConsumer.getResult();
             final Exception ex = this.responseConsumer.getException();
             if (result != null) {
                 this.future.completed(result);
             } else {
                 this.future.failed(ex);
             }
             if (this.closed.compareAndSet(false, true)) {
                 releaseResources();
             }
         } catch (final RuntimeException ex) {
             failed(ex);
             throw ex;
         }
     }
 
     @Override
     public void inputTerminated() {
         failed(new ConnectionClosedException());
     }
 
     @Override
     public void failed(final Exception ex) {
         if (this.closed.compareAndSet(false, true)) {
             try {
                 if (!this.requestSent.get()) {
                     this.requestProducer.failed(ex);
                 }
                 this.responseConsumer.failed(ex);
             } finally {
                 try {
                     this.future.failed(ex);
                 } finally {
                     releaseResources();
                 }
             }
         }
     }
 
     @Override
     public boolean cancel() {
         if (this.closed.compareAndSet(false, true)) {
             try {
                 try {
                     return this.responseConsumer.cancel();
                 } finally {
                     this.future.cancel();
                 }
             } finally {
                 releaseResources();
             }
         }
         return false;
     }
 
     @Override
     public boolean isDone() {
         return this.responseConsumer.isDone();
     }
 
 }