//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.client.util;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InterruptedIOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.AsynchronousCloseException;
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.LinkedBlockingQueue;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.concurrent.atomic.AtomicLong;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.eclipse.jetty.client.HttpClient;
  import org.eclipse.jetty.client.api.Response;
  import org.eclipse.jetty.client.api.Response.Listener;
  import org.eclipse.jetty.client.api.Result;
  import org.eclipse.jetty.util.IO;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /**
   * Implementation of {@link Listener} that produces an {@link InputStream}
   * that allows applications to read the response content.
   * <p>
   * Typical usage is:
   * <pre>
   * InputStreamResponseListener listener = new InputStreamResponseListener();
   * client.newRequest(...).send(listener);
   *
   * // Wait for the response headers to arrive
   * Response response = listener.get(5, TimeUnit.SECONDS);
   * if (response.getStatus() == 200)
   * {
   *     // Obtain the input stream on the response content
   *     try (InputStream input = listener.getInputStream())
   *     {
   *         // Read the response content
   *     }
   * }
   * </pre>
   * <p>
   * The {@link HttpClient} implementation (the producer) will feed the input stream
   * asynchronously while the application (the consumer) is reading from it.
   * Chunks of content are maintained in a queue, and it is possible to specify a
   * maximum buffer size for the bytes held in the queue, by default 16384 bytes.
   * <p>
   * If the consumer is faster than the producer, then the consumer will block
   * with the typical {@link InputStream#read()} semantic.
   * If the consumer is slower than the producer, then the producer will block
   * until the client consumes.
   */
  public class InputStreamResponseListener extends Listener.Adapter
  {
      private static final Logger LOG = Log.getLogger(InputStreamResponseListener.class);
      private static final byte[] EOF = new byte[0];
      private static final byte[] CLOSED = new byte[0];
      private static final byte[] FAILURE = new byte[0];
      private final BlockingQueue<byte[]> queue = new LinkedBlockingQueue<>();
      private final AtomicLong length = new AtomicLong();
      private final CountDownLatch responseLatch = new CountDownLatch(1);
      private final CountDownLatch resultLatch = new CountDownLatch(1);
      private final AtomicReference<InputStream> stream = new AtomicReference<>();
      private final long maxBufferSize;
      private Response response;
      private Result result;
      private volatile Throwable failure;
      private volatile boolean closed;
  
      public InputStreamResponseListener()
      {
          this(16 * 1024L);
      }
  
      public InputStreamResponseListener(long maxBufferSize)
      {
          this.maxBufferSize = maxBufferSize;
      }
 
     @Override
     public void onHeaders(Response response)
     {
         this.response = response;
         responseLatch.countDown();
     }
 
     @Override
     public void onContent(Response response, ByteBuffer content)
     {
         if (!closed)
         {
             int remaining = content.remaining();
             if (remaining > 0)
             {
 
                 byte[] bytes = new byte[remaining];
                 content.get(bytes);
                 if (LOG.isDebugEnabled())
                     LOG.debug("Queuing {}/{} bytes", bytes, remaining);
                 queue.offer(bytes);
 
                 long newLength = length.addAndGet(remaining);
                 while (newLength >= maxBufferSize)
                 {
                     if (LOG.isDebugEnabled())
                         LOG.debug("Queued bytes limit {}/{} exceeded, waiting", newLength, maxBufferSize);
                     // Block to avoid infinite buffering
                     if (!await())
                         break;
                     newLength = length.get();
                     if (LOG.isDebugEnabled())
                         LOG.debug("Queued bytes limit {}/{} exceeded, woken up", newLength, maxBufferSize);
                 }
             }
             else
             {
                 if (LOG.isDebugEnabled())
                     LOG.debug("Queuing skipped, empty content {}", content);
             }
         }
         else
         {
             LOG.debug("Queuing skipped, stream already closed");
         }
     }
 
     @Override
     public void onSuccess(Response response)
     {
         if (LOG.isDebugEnabled())
             LOG.debug("Queuing end of content {}{}", EOF, "");
         queue.offer(EOF);
         signal();
     }
 
     @Override
     public void onFailure(Response response, Throwable failure)
     {
         fail(failure);
         signal();
     }
 
     @Override
     public void onComplete(Result result)
     {
         if (result.isFailed() && failure == null)
             fail(result.getFailure());
         this.result = result;
         resultLatch.countDown();
         signal();
     }
 
     private void fail(Throwable failure)
     {
         if (LOG.isDebugEnabled())
             LOG.debug("Queuing failure {} {}", FAILURE, failure);
         queue.offer(FAILURE);
         this.failure = failure;
         responseLatch.countDown();
     }
 
     protected boolean await()
     {
         try
         {
             synchronized (this)
             {
                 while (length.get() >= maxBufferSize && failure == null && !closed)
                     wait();
                 // Re-read the values as they may have changed while waiting.
                 return failure == null && !closed;
             }
         }
         catch (InterruptedException x)
         {
             Thread.currentThread().interrupt();
             return false;
         }
     }
 
     protected void signal()
     {
         synchronized (this)
         {
             notifyAll();
         }
     }
 
     /**
      * Waits for the given timeout for the response to be available, then returns it.
      * <p>
      * The wait ends as soon as all the HTTP headers have been received, without waiting for the content.
      * To wait for the whole content, see {@link #await(long, TimeUnit)}.
      *
      * @param timeout the time to wait
      * @param unit the timeout unit
      * @return the response
      * @throws InterruptedException if the thread is interrupted
      * @throws TimeoutException if the timeout expires
      * @throws ExecutionException if a failure happened
      */
     public Response get(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException, ExecutionException
     {
         boolean expired = !responseLatch.await(timeout, unit);
         if (expired)
             throw new TimeoutException();
         if (failure != null)
             throw new ExecutionException(failure);
         return response;
     }
 
     /**
      * Waits for the given timeout for the whole request/response cycle to be finished,
      * then returns the corresponding result.
      * <p>
      *
      * @param timeout the time to wait
      * @param unit the timeout unit
      * @return the result
      * @throws InterruptedException if the thread is interrupted
      * @throws TimeoutException if the timeout expires
      * @see #get(long, TimeUnit)
      */
     public Result await(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException
     {
         boolean expired = !resultLatch.await(timeout, unit);
         if (expired)
             throw new TimeoutException();
         return result;
     }
 
     /**
      * Returns an {@link InputStream} providing the response content bytes.
      * <p>
      * The method may be invoked only once; subsequent invocations will return a closed {@link InputStream}.
      *
      * @return an input stream providing the response content
      */
     public InputStream getInputStream()
     {
         InputStream result = new Input();
         if (stream.compareAndSet(null, result))
             return result;
         return IO.getClosedStream();
     }
 
     private class Input extends InputStream
     {
         private byte[] bytes;
         private int index;
 
         @Override
         public int read() throws IOException
         {
             while (true)
             {
                 if (bytes == EOF)
                 {
                     // Mark the fact that we saw -1,
                     // so that in the close case we don't throw
                     index = -1;
                     return -1;
                 }
                 else if (bytes == FAILURE)
                 {
                     throw failure();
                 }
                 else if (bytes == CLOSED)
                 {
                     if (index < 0)
                         return -1;
                     throw new AsynchronousCloseException();
                 }
                 else if (bytes != null)
                 {
                     int result = bytes[index] & 0xFF;
                     if (++index == bytes.length)
                     {
                         length.addAndGet(-index);
                         bytes = null;
                         index = 0;
                         signal();
                     }
                     return result;
                 }
                 else
                 {
                     bytes = take();
                     if (LOG.isDebugEnabled())
                         LOG.debug("Dequeued {}/{} bytes", bytes, bytes.length);
                 }
             }
         }
 
         private IOException failure()
         {
             if (failure instanceof IOException)
                 return (IOException)failure;
             else
                 return new IOException(failure);
         }
 
         private byte[] take() throws IOException
         {
             try
             {
                 return queue.take();
             }
             catch (InterruptedException x)
             {
                 throw new InterruptedIOException();
             }
         }
 
         @Override
         public void close() throws IOException
         {
             if (!closed)
             {
                 super.close();
                 if (LOG.isDebugEnabled())
                     LOG.debug("Queuing close {}{}", CLOSED, "");
                 queue.offer(CLOSED);
                 closed = true;
                 signal();
             }
         }
     }
 }