/*
    * ====================================================================
    * 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.impl.nio.client;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.commons.logging.Log;
  import org.apache.http.ConnectionClosedException;
  import org.apache.http.ConnectionReuseStrategy;
  import org.apache.http.HttpException;
  import org.apache.http.HttpHost;
  import org.apache.http.HttpRequest;
  import org.apache.http.HttpResponse;
  import org.apache.http.client.config.RequestConfig;
  import org.apache.http.client.methods.HttpRequestWrapper;
  import org.apache.http.client.protocol.HttpClientContext;
  import org.apache.http.concurrent.BasicFuture;
  import org.apache.http.conn.ConnectionKeepAliveStrategy;
  import org.apache.http.conn.routing.HttpRoute;
  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.nio.conn.NHttpClientConnectionManager;
  import org.apache.http.nio.protocol.HttpAsyncRequestProducer;
  import org.apache.http.nio.protocol.HttpAsyncResponseConsumer;
  import org.apache.http.nio.protocol.Pipelined;
  import org.apache.http.protocol.HttpCoreContext;
  import org.apache.http.protocol.HttpProcessor;
  import org.apache.http.util.Args;
  import org.apache.http.util.Asserts;
  
  /**
   * {@link org.apache.http.nio.protocol.HttpAsyncClientExchangeHandler} implementation
   * that supports HTTP message pipelining.
   * <p>
   * Instances of this class are expected to be accessed by one thread at a time only.
   * The {@link #cancel()} method can be called concurrently by multiple threads.
   */
  @Pipelined
  class PipeliningClientExchangeHandlerImpl<T> extends AbstractClientExchangeHandler {
  
      private final HttpHost target;
      private final Queue<HttpAsyncRequestProducer> requestProducerQueue;
      private final Queue<HttpAsyncResponseConsumer<T>> responseConsumerQueue;
      private final Queue<HttpRequest> requestQueue;
      private final Queue<T> resultQueue;
      private final HttpClientContext localContext;
      private final BasicFuture<List<T>> resultFuture;
      private final HttpProcessor httpProcessor;
      private final AtomicReference<HttpAsyncRequestProducer> requestProducerRef;
      private final AtomicReference<HttpAsyncResponseConsumer<T>> responseConsumerRef;
  
      public PipeliningClientExchangeHandlerImpl(
              final Log log,
              final HttpHost target,
              final List<? extends HttpAsyncRequestProducer> requestProducers,
              final List<? extends HttpAsyncResponseConsumer<T>> responseConsumers,
              final HttpClientContext localContext,
              final BasicFuture<List<T>> resultFuture,
              final NHttpClientConnectionManager connmgr,
              final HttpProcessor httpProcessor,
              final ConnectionReuseStrategy connReuseStrategy,
              final ConnectionKeepAliveStrategy keepaliveStrategy) {
          super(log, localContext, connmgr, connReuseStrategy, keepaliveStrategy);
          Args.notNull(target, "HTTP target");
          Args.notEmpty(requestProducers, "Request producer list");
          Args.notEmpty(responseConsumers, "Response consumer list");
          Args.check(requestProducers.size() == responseConsumers.size(),
                  "Number of request producers does not match that of response consumers");
         this.target = target;
         this.requestProducerQueue = new ConcurrentLinkedQueue<HttpAsyncRequestProducer>(requestProducers);
         this.responseConsumerQueue = new ConcurrentLinkedQueue<HttpAsyncResponseConsumer<T>>(responseConsumers);
         this.requestQueue = new ConcurrentLinkedQueue<HttpRequest>();
         this.resultQueue = new ConcurrentLinkedQueue<T>();
         this.localContext = localContext;
         this.resultFuture = resultFuture;
         this.httpProcessor = httpProcessor;
         this.requestProducerRef = new AtomicReference<HttpAsyncRequestProducer>(null);
         this.responseConsumerRef = new AtomicReference<HttpAsyncResponseConsumer<T>>(null);
     }
 
     private void closeProducer(final HttpAsyncRequestProducer requestProducer) {
         if (requestProducer != null) {
             try {
                 requestProducer.close();
             } catch (final IOException ex) {
                 this.log.debug("I/O error closing request producer", ex);
             }
         }
     }
 
     private void closeConsumer(final HttpAsyncResponseConsumer<?> responseConsumer) {
         if (responseConsumer != null) {
             try {
                 responseConsumer.close();
             } catch (final IOException ex) {
                 this.log.debug("I/O error closing response consumer", ex);
             }
         }
     }
 
     @Override
     void releaseResources() {
         closeProducer(this.requestProducerRef.getAndSet(null));
         closeConsumer(this.responseConsumerRef.getAndSet(null));
         while (!this.requestProducerQueue.isEmpty()) {
             closeProducer(this.requestProducerQueue.remove());
         }
         while (!this.responseConsumerQueue.isEmpty()) {
             closeConsumer(this.responseConsumerQueue.remove());
         }
         this.requestQueue.clear();
         this.resultQueue.clear();
     }
 
     @Override
     void executionFailed(final Exception ex) {
         final HttpAsyncRequestProducer requestProducer = this.requestProducerRef.get();
         if (requestProducer != null) {
             requestProducer.failed(ex);
         }
         final HttpAsyncResponseConsumer<T> responseConsumer = this.responseConsumerRef.get();
         if (responseConsumer != null) {
             responseConsumer.failed(ex);
         }
         for (final HttpAsyncResponseConsumer<T> cancellable: this.responseConsumerQueue) {
             cancellable.cancel();
         }
     }
 
     @Override
     boolean executionCancelled() {
         final HttpAsyncResponseConsumer<T> responseConsumer = this.responseConsumerRef.get();
         final boolean cancelled = responseConsumer != null && responseConsumer.cancel();
         this.resultFuture.cancel();
         return cancelled;
     }
 
     public void start() throws HttpException, IOException {
         if (this.log.isDebugEnabled()) {
             this.log.debug("[exchange: " + getId() + "] start execution");
         }
 
         final HttpRoute route = new HttpRoute(this.target);
         setRoute(route);
 
         this.localContext.setAttribute(HttpClientContext.HTTP_TARGET_HOST, this.target);
         this.localContext.setAttribute(HttpClientContext.HTTP_ROUTE, route);
 
         requestConnection();
     }
 
     @Override
     public HttpRequest generateRequest() throws IOException, HttpException {
         verifytRoute();
         if (!isRouteEstablished()) {
             onRouteToTarget();
             onRouteComplete();
         }
         final NHttpClientConnection localConn = getConnection();
         this.localContext.setAttribute(HttpCoreContext.HTTP_CONNECTION, localConn);
 
         Asserts.check(this.requestProducerRef.get() == null, "Inconsistent state: currentRequest producer is not null");
         final HttpAsyncRequestProducer requestProducer = this.requestProducerQueue.poll();
         if (requestProducer == null) {
             return null;
         }
         this.requestProducerRef.set(requestProducer);
 
         final HttpRequest original = requestProducer.generateRequest();
         final HttpRequestWrapper currentRequest = HttpRequestWrapper.wrap(original);
         final RequestConfig config = this.localContext.getRequestConfig();
         if (config.getSocketTimeout() > 0) {
             localConn.setSocketTimeout(config.getSocketTimeout());
         }
 
         this.httpProcessor.process(currentRequest, this.localContext);
 
         this.requestQueue.add(currentRequest);
         setCurrentRequest(currentRequest);
 
         return currentRequest;
     }
 
     @Override
     public void produceContent(
             final ContentEncoder encoder, final IOControl ioctrl) throws IOException {
         if (this.log.isDebugEnabled()) {
             this.log.debug("[exchange: " + getId() + "] produce content");
         }
         final HttpAsyncRequestProducer requestProducer = this.requestProducerRef.get();
         Asserts.check(requestProducer != null, "Inconsistent state: request producer is null");
         requestProducer.produceContent(encoder, ioctrl);
         if (encoder.isCompleted()) {
             requestProducer.resetRequest();
         }
     }
 
     @Override
     public void requestCompleted() {
         if (this.log.isDebugEnabled()) {
             this.log.debug("[exchange: " + getId() + "] Request completed");
         }
         final HttpAsyncRequestProducer requestProducer = this.requestProducerRef.getAndSet(null);
         Asserts.check(requestProducer != null, "Inconsistent state: request producer is null");
         requestProducer.requestCompleted(this.localContext);
         try {
             requestProducer.close();
         } catch (final IOException ioex) {
             this.log.debug(ioex.getMessage(), ioex);
         }
     }
 
     @Override
     public void responseReceived(
             final HttpResponse response) throws IOException, HttpException {
         if (this.log.isDebugEnabled()) {
             this.log.debug("[exchange: " + getId() + "] Response received " + response.getStatusLine());
         }
 
         Asserts.check(this.responseConsumerRef.get() == null, "Inconsistent state: response consumer is not null");
 
         final HttpAsyncResponseConsumer<T> responseConsumer = this.responseConsumerQueue.poll();
         Asserts.check(responseConsumer != null, "Inconsistent state: response consumer queue is empty");
         this.responseConsumerRef.set(responseConsumer);
 
         final HttpRequest request = this.requestQueue.poll();
         Asserts.check(request != null, "Inconsistent state: request queue is empty");
 
         this.localContext.setAttribute(HttpCoreContext.HTTP_REQUEST, request);
         this.localContext.setAttribute(HttpCoreContext.HTTP_RESPONSE, response);
         this.httpProcessor.process(response, this.localContext);
 
         responseConsumer.responseReceived(response);
 
         setCurrentResponse(response);
     }
 
     @Override
     public void consumeContent(
             final ContentDecoder decoder, final IOControl ioctrl) throws IOException {
         if (this.log.isDebugEnabled()) {
             this.log.debug("[exchange: " + getId() + "] Consume content");
         }
         final HttpAsyncResponseConsumer<T> responseConsumer = this.responseConsumerRef.get();
         Asserts.check(responseConsumer != null, "Inconsistent state: response consumer is null");
         responseConsumer.consumeContent(decoder, ioctrl);
     }
 
     @Override
     public void responseCompleted() throws IOException, HttpException {
         if (this.log.isDebugEnabled()) {
             this.log.debug("[exchange: " + getId() + "] Response processed");
         }
 
         final boolean keepAlive = manageConnectionPersistence();
 
         final HttpAsyncResponseConsumer<T> responseConsumer = this.responseConsumerRef.getAndSet(null);
         Asserts.check(responseConsumer != null, "Inconsistent state: response consumer is null");
         try {
             responseConsumer.responseCompleted(this.localContext);
             final T result = responseConsumer.getResult();
             final Exception ex = responseConsumer.getException();
             try {
                 responseConsumer.close();
             } catch (final IOException ioex) {
                 this.log.debug(ioex.getMessage(), ioex);
             }
             if (result != null) {
                 this.resultQueue.add(result);
             } else {
                 failed(ex);
             }
             if (!this.resultFuture.isDone() && this.responseConsumerQueue.isEmpty()) {
                 this.resultFuture.completed(new ArrayList<T>(this.resultQueue));
                 this.resultQueue.clear();
             }
 
             if (this.resultFuture.isDone()) {
                 close();
             } else {
                 if (!keepAlive) {
                     failed(new ConnectionClosedException("Connection closed"));
                 } else {
                     final NHttpClientConnection localConn = getConnection();
                     if (localConn != null) {
                         localConn.requestOutput();
                     } else {
                         requestConnection();
                     }
                 }
             }
         } catch (final RuntimeException ex) {
             failed(ex);
             throw ex;
         }
     }
 
     @Override
     public void inputTerminated() {
         failed(new ConnectionClosedException("Connection closed"));
     }
 
     public void abortConnection() {
         discardConnection();
     }
 
 }