//
   //  ========================================================================
   //  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;
  
  import java.io.IOException;
  import java.net.URI;
  import java.nio.ByteBuffer;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.eclipse.jetty.client.api.Response;
  import org.eclipse.jetty.client.api.Result;
  import org.eclipse.jetty.http.HttpField;
  import org.eclipse.jetty.http.HttpHeader;
  import org.eclipse.jetty.http.HttpStatus;
  import org.eclipse.jetty.util.BufferUtil;
  import org.eclipse.jetty.util.Callback;
  import org.eclipse.jetty.util.CountingCallback;
  import org.eclipse.jetty.util.component.Destroyable;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /**
   * {@link HttpReceiver} provides the abstract code to implement the various steps of the receive of HTTP responses.
   * <p>
   * {@link HttpReceiver} maintains a state machine that is updated when the steps of receiving a response are executed.
   * <p>
   * Subclasses must handle the transport-specific details, for example how to read from the raw socket and how to parse
   * the bytes read from the socket. Then they have to call the methods defined in this class in the following order:
   * <ol>
   * <li>{@link #responseBegin(HttpExchange)}, when the HTTP response data containing the HTTP status code
   * is available</li>
   * <li>{@link #responseHeader(HttpExchange, HttpField)}, when a HTTP field is available</li>
   * <li>{@link #responseHeaders(HttpExchange)}, when all HTTP headers are available</li>
   * <li>{@link #responseContent(HttpExchange, ByteBuffer, Callback)}, when HTTP content is available</li>
   * <li>{@link #responseSuccess(HttpExchange)}, when the response is successful</li>
   * </ol>
   * At any time, subclasses may invoke {@link #responseFailure(Throwable)} to indicate that the response has failed
   * (for example, because of I/O exceptions).
   * At any time, user threads may abort the response which will cause {@link #responseFailure(Throwable)} to be
   * invoked.
   * <p>
   * The state machine maintained by this class ensures that the response steps are not executed by an I/O thread
   * if the response has already been failed.
   *
   * @see HttpSender
   */
  public abstract class HttpReceiver
  {
      protected static final Logger LOG = Log.getLogger(HttpReceiver.class);
  
      private final AtomicReference<ResponseState> responseState = new AtomicReference<>(ResponseState.IDLE);
      private final HttpChannel channel;
      private ContentDecoder decoder;
      private Throwable failure;
  
      protected HttpReceiver(HttpChannel channel)
      {
          this.channel = channel;
      }
  
      protected HttpChannel getHttpChannel()
      {
          return channel;
      }
  
      protected HttpExchange getHttpExchange()
      {
          return channel.getHttpExchange();
      }
  
      protected HttpDestination getHttpDestination()
      {
          return channel.getHttpDestination();
      }
  
      /**
       * Method to be invoked when the response status code is available.
      * <p>
      * Subclasses must have set the response status code on the {@link Response} object of the {@link HttpExchange}
      * prior invoking this method.
      * <p>
      * This method takes case of notifying {@link org.eclipse.jetty.client.api.Response.BeginListener}s.
      *
      * @param exchange the HTTP exchange
      * @return whether the processing should continue
      */
     protected boolean responseBegin(HttpExchange exchange)
     {
         if (!updateResponseState(ResponseState.IDLE, ResponseState.TRANSIENT))
             return false;
 
         HttpConversation conversation = exchange.getConversation();
         HttpResponse response = exchange.getResponse();
         // Probe the protocol handlers
         HttpDestination destination = getHttpDestination();
         HttpClient client = destination.getHttpClient();
         ProtocolHandler protocolHandler = client.findProtocolHandler(exchange.getRequest(), response);
         Response.Listener handlerListener = null;
         if (protocolHandler != null)
         {
             handlerListener = protocolHandler.getResponseListener();
             if (LOG.isDebugEnabled())
                 LOG.debug("Found protocol handler {}", protocolHandler);
         }
         exchange.getConversation().updateResponseListeners(handlerListener);
 
         if (LOG.isDebugEnabled())
             LOG.debug("Response begin {}", response);
         ResponseNotifier notifier = destination.getResponseNotifier();
         notifier.notifyBegin(conversation.getResponseListeners(), response);
 
         if (updateResponseState(ResponseState.TRANSIENT, ResponseState.BEGIN))
             return true;
 
         terminateResponse(exchange);
         return false;
     }
 
     /**
      * Method to be invoked when a response HTTP header is available.
      * <p>
      * Subclasses must not have added the header to the {@link Response} object of the {@link HttpExchange}
      * prior invoking this method.
      * <p>
      * This method takes case of notifying {@link org.eclipse.jetty.client.api.Response.HeaderListener}s and storing cookies.
      *
      * @param exchange the HTTP exchange
      * @param field the response HTTP field
      * @return whether the processing should continue
      */
     protected boolean responseHeader(HttpExchange exchange, HttpField field)
     {
         out: while (true)
         {
             ResponseState current = responseState.get();
             switch (current)
             {
                 case BEGIN:
                 case HEADER:
                 {
                     if (updateResponseState(current, ResponseState.TRANSIENT))
                         break out;
                     break;
                 }
                 default:
                 {
                     return false;
                 }
             }
         }
 
         HttpResponse response = exchange.getResponse();
         ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
         boolean process = notifier.notifyHeader(exchange.getConversation().getResponseListeners(), response, field);
         if (process)
         {
             response.getHeaders().add(field);
             HttpHeader fieldHeader = field.getHeader();
             if (fieldHeader != null)
             {
                 switch (fieldHeader)
                 {
                     case SET_COOKIE:
                     case SET_COOKIE2:
                     {
                         URI uri = exchange.getRequest().getURI();
                         if (uri != null)
                             storeCookie(uri, field);
                         break;
                     }
                     default:
                     {
                         break;
                     }
                 }
             }
         }
 
         if (updateResponseState(ResponseState.TRANSIENT, ResponseState.HEADER))
             return true;
 
         terminateResponse(exchange);
         return false;
     }
 
     protected void storeCookie(URI uri, HttpField field)
     {
         try
         {
             String value = field.getValue();
             if (value != null)
             {
                 Map<String, List<String>> header = new HashMap<>(1);
                 header.put(field.getHeader().asString(), Collections.singletonList(value));
                 getHttpDestination().getHttpClient().getCookieManager().put(uri, header);
             }
         }
         catch (IOException x)
         {
             if (LOG.isDebugEnabled())
                 LOG.debug(x);
         }
     }
 
     /**
      * Method to be invoked after all response HTTP headers are available.
      * <p>
      * This method takes case of notifying {@link org.eclipse.jetty.client.api.Response.HeadersListener}s.
      *
      * @param exchange the HTTP exchange
      * @return whether the processing should continue
      */
     protected boolean responseHeaders(HttpExchange exchange)
     {
         out: while (true)
         {
             ResponseState current = responseState.get();
             switch (current)
             {
                 case BEGIN:
                 case HEADER:
                 {
                     if (updateResponseState(current, ResponseState.TRANSIENT))
                         break out;
                     break;
                 }
                 default:
                 {
                     return false;
                 }
             }
         }
 
         HttpResponse response = exchange.getResponse();
         if (LOG.isDebugEnabled())
             LOG.debug("Response headers {}{}{}", response, System.lineSeparator(), response.getHeaders().toString().trim());
         ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
         notifier.notifyHeaders(exchange.getConversation().getResponseListeners(), response);
 
         Enumeration<String> contentEncodings = response.getHeaders().getValues(HttpHeader.CONTENT_ENCODING.asString(), ",");
         if (contentEncodings != null)
         {
             for (ContentDecoder.Factory factory : getHttpDestination().getHttpClient().getContentDecoderFactories())
             {
                 while (contentEncodings.hasMoreElements())
                 {
                     if (factory.getEncoding().equalsIgnoreCase(contentEncodings.nextElement()))
                     {
                         this.decoder = factory.newContentDecoder();
                         break;
                     }
                 }
             }
         }
 
         if (updateResponseState(ResponseState.TRANSIENT, ResponseState.HEADERS))
             return true;
 
         terminateResponse(exchange);
         return false;
     }
 
     /**
      * Method to be invoked when response HTTP content is available.
      * <p>
      * This method takes case of decoding the content, if necessary, and notifying {@link org.eclipse.jetty.client.api.Response.ContentListener}s.
      *
      * @param exchange the HTTP exchange
      * @param buffer the response HTTP content buffer
      * @param callback the callback
      * @return whether the processing should continue
      */
     protected boolean responseContent(HttpExchange exchange, ByteBuffer buffer, final Callback callback)
     {
         out: while (true)
         {
             ResponseState current = responseState.get();
             switch (current)
             {
                 case HEADERS:
                 case CONTENT:
                 {
                     if (updateResponseState(current, ResponseState.TRANSIENT))
                         break out;
                     break;
                 }
                 default:
                 {
                     callback.failed(new IllegalStateException("Invalid response state " + current));
                     return false;
                 }
             }
         }
 
         HttpResponse response = exchange.getResponse();
         if (LOG.isDebugEnabled())
             LOG.debug("Response content {}{}{}", response, System.lineSeparator(), BufferUtil.toDetailString(buffer));
 
         ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
         List<Response.ResponseListener> listeners = exchange.getConversation().getResponseListeners();
 
         ContentDecoder decoder = this.decoder;
         if (decoder == null)
         {
             notifier.notifyContent(listeners, response, buffer, callback);
         }
         else
         {
             try
             {
                 List<ByteBuffer> decodeds = new ArrayList<>(2);
                 while (buffer.hasRemaining())
                 {
                     ByteBuffer decoded = decoder.decode(buffer);
                     if (!decoded.hasRemaining())
                         continue;
                     decodeds.add(decoded);
                     if (LOG.isDebugEnabled())
                         LOG.debug("Response content decoded ({}) {}{}{}", decoder, response, System.lineSeparator(), BufferUtil.toDetailString(decoded));
                 }
 
                 if (decodeds.isEmpty())
                 {
                     callback.succeeded();
                 }
                 else
                 {
                     int size = decodeds.size();
                     CountingCallback counter = new CountingCallback(callback, size);
                     for (int i = 0; i < size; ++i)
                         notifier.notifyContent(listeners, response, decodeds.get(i), counter);
                 }
             }
             catch (Throwable x)
             {
                 callback.failed(x);
             }
         }
 
         if (updateResponseState(ResponseState.TRANSIENT, ResponseState.CONTENT))
             return true;
 
         terminateResponse(exchange);
         return false;
     }
 
     /**
      * Method to be invoked when the response is successful.
      * <p>
      * This method takes case of notifying {@link org.eclipse.jetty.client.api.Response.SuccessListener}s and possibly
      * {@link org.eclipse.jetty.client.api.Response.CompleteListener}s (if the exchange is completed).
      *
      * @param exchange the HTTP exchange
      * @return whether the response was processed as successful
      */
     protected boolean responseSuccess(HttpExchange exchange)
     {
         // Mark atomically the response as completed, with respect
         // to concurrency between response success and response failure.
         if (!exchange.responseComplete(null))
             return false;
 
         responseState.set(ResponseState.IDLE);
 
         // Reset to be ready for another response.
         reset();
 
         HttpResponse response = exchange.getResponse();
         if (LOG.isDebugEnabled())
             LOG.debug("Response success {}", response);
         List<Response.ResponseListener> listeners = exchange.getConversation().getResponseListeners();
         ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
         notifier.notifySuccess(listeners, response);
 
         // Special case for 100 Continue that cannot
         // be handled by the ContinueProtocolHandler.
         if (exchange.getResponse().getStatus() == HttpStatus.CONTINUE_100)
             return true;
 
         // Mark atomically the response as terminated, with
         // respect to concurrency between request and response.
         Result result = exchange.terminateResponse();
         terminateResponse(exchange, result);
 
         return true;
     }
 
     /**
      * Method to be invoked when the response is failed.
      * <p>
      * This method takes care of notifying {@link org.eclipse.jetty.client.api.Response.FailureListener}s.
      *
      * @param failure the response failure
      * @return whether the response was processed as failed
      */
     protected boolean responseFailure(Throwable failure)
     {
         HttpExchange exchange = getHttpExchange();
         // In case of a response error, the failure has already been notified
         // and it is possible that a further attempt to read in the receive
         // loop throws an exception that reenters here but without exchange;
         // or, the server could just have timed out the connection.
         if (exchange == null)
             return false;
 
         // Mark atomically the response as completed, with respect
         // to concurrency between response success and response failure.
         if (exchange.responseComplete(failure))
             return abort(exchange, failure);
 
         return false;
     }
 
     private void terminateResponse(HttpExchange exchange)
     {
         Result result = exchange.terminateResponse();
         terminateResponse(exchange, result);
     }
 
     private void terminateResponse(HttpExchange exchange, Result result)
     {
         HttpResponse response = exchange.getResponse();
 
         if (LOG.isDebugEnabled())
             LOG.debug("Response complete {}", response);
 
         if (result != null)
         {
             result = channel.exchangeTerminating(exchange, result);
             boolean ordered = getHttpDestination().getHttpClient().isStrictEventOrdering();
             if (!ordered)
                 channel.exchangeTerminated(exchange, result);
             if (LOG.isDebugEnabled())
                 LOG.debug("Request/Response {}: {}", failure == null ? "succeeded" : "failed", result);
             List<Response.ResponseListener> listeners = exchange.getConversation().getResponseListeners();
             ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
             notifier.notifyComplete(listeners, result);
             if (ordered)
                 channel.exchangeTerminated(exchange, result);
         }
     }
 
     /**
      * Resets this {@link HttpReceiver} state.
      * <p>
      * Subclasses should override (but remember to call {@code super}) to reset their own state.
      * <p>
      * Either this method or {@link #dispose()} is called.
      */
     protected void reset()
     {
         destroyDecoder(decoder);
         decoder = null;
     }
 
     /**
      * Disposes this {@link HttpReceiver} state.
      * <p>
      * Subclasses should override (but remember to call {@code super}) to dispose their own state.
      * <p>
      * Either this method or {@link #reset()} is called.
      */
     protected void dispose()
     {
         destroyDecoder(decoder);
         decoder = null;
     }
 
     private static void destroyDecoder(ContentDecoder decoder)
     {
         if (decoder instanceof Destroyable)
         {
             ((Destroyable)decoder).destroy();
         }
     }
 
     public boolean abort(HttpExchange exchange, Throwable failure)
     {
         // Update the state to avoid more response processing.
         boolean terminate;
         out: while (true)
         {
             ResponseState current = responseState.get();
             switch (current)
             {
                 case FAILURE:
                 {
                     return false;
                 }
                 default:
                 {
                     if (updateResponseState(current, ResponseState.FAILURE))
                     {
                         terminate = current != ResponseState.TRANSIENT;
                         break out;
                     }
                     break;
                 }
             }
         }
 
         this.failure = failure;
 
         dispose();
 
         HttpResponse response = exchange.getResponse();
         if (LOG.isDebugEnabled())
             LOG.debug("Response failure {} {} on {}: {}", response, exchange, getHttpChannel(), failure);
         List<Response.ResponseListener> listeners = exchange.getConversation().getResponseListeners();
         ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
         notifier.notifyFailure(listeners, response, failure);
 
         if (terminate)
         {
             // Mark atomically the response as terminated, with
             // respect to concurrency between request and response.
             Result result = exchange.terminateResponse();
             terminateResponse(exchange, result);
         }
         else
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("Concurrent failure: response termination skipped, performed by helpers");
         }
 
         return true;
     }
 
     private boolean updateResponseState(ResponseState from, ResponseState to)
     {
         boolean updated = responseState.compareAndSet(from, to);
         if (!updated)
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("State update failed: {} -> {}: {}", from, to, responseState.get());
         }
         return updated;
     }
 
     @Override
     public String toString()
     {
         return String.format("%s@%x(rsp=%s,failure=%s)",
                 getClass().getSimpleName(),
                 hashCode(),
                 responseState,
                 failure);
     }
 
     /**
      * The request states {@link HttpReceiver} goes through when receiving a response.
      */
     private enum ResponseState
     {
         /**
          * One of the response*() methods is being executed.
          */
         TRANSIENT,
         /**
          * The response is not yet received, the initial state
          */
         IDLE,
         /**
          * The response status code has been received
          */
         BEGIN,
         /**
          * The response headers are being received
          */
         HEADER,
         /**
          * All the response headers have been received
          */
         HEADERS,
         /**
          * The response content is being received
          */
         CONTENT,
         /**
          * The response is failed
          */
         FAILURE
     }
 }