//
   //  ========================================================================
   //  Copyright (c) 1995-2014 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.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.eclipse.jetty.client.api.Request;
  import org.eclipse.jetty.client.api.Response;
  import org.eclipse.jetty.client.api.Result;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  public class HttpExchange
  {
      private static final Logger LOG = Log.getLogger(HttpExchange.class);
  
      private final AtomicBoolean requestComplete = new AtomicBoolean();
      private final AtomicBoolean responseComplete = new AtomicBoolean();
      private final AtomicInteger complete = new AtomicInteger();
      private final AtomicReference<HttpChannel> channel = new AtomicReference<>();
      private final HttpDestination destination;
      private final HttpRequest request;
      private final List<Response.ResponseListener> listeners;
      private final HttpResponse response;
      private volatile Throwable requestFailure;
      private volatile Throwable responseFailure;
  
      public HttpExchange(HttpDestination destination, HttpRequest request, List<Response.ResponseListener> listeners)
      {
          this.destination = destination;
          this.request = request;
          this.listeners = listeners;
          this.response = new HttpResponse(request, listeners);
          HttpConversation conversation = request.getConversation();
          conversation.getExchanges().offer(this);
          conversation.updateResponseListeners(null);
      }
  
      public HttpConversation getConversation()
      {
          return request.getConversation();
      }
  
      public Request getRequest()
      {
          return request;
      }
  
      public Throwable getRequestFailure()
      {
          return requestFailure;
      }
  
      public List<Response.ResponseListener> getResponseListeners()
      {
          return listeners;
      }
  
      public HttpResponse getResponse()
      {
          return response;
      }
  
      public Throwable getResponseFailure()
      {
          return responseFailure;
      }
  
      public void associate(HttpChannel channel)
      {
          if (!this.channel.compareAndSet(null, channel))
              throw new IllegalStateException();
      }
  
      public void disassociate(HttpChannel channel)
      {
          if (!this.channel.compareAndSet(channel, null))
              throw new IllegalStateException();
      }
  
     public boolean requestComplete()
     {
         return requestComplete.compareAndSet(false, true);
     }
 
     public boolean responseComplete()
     {
         return responseComplete.compareAndSet(false, true);
     }
 
     public Result terminateRequest(Throwable failure)
     {
         int requestSuccess = 0b0011;
         int requestFailure = 0b0001;
         return terminate(failure == null ? requestSuccess : requestFailure, failure);
     }
 
     public Result terminateResponse(Throwable failure)
     {
         if (failure == null)
         {
             int responseSuccess = 0b1100;
             return terminate(responseSuccess, null);
         }
         else
         {
             proceed(failure);
             int responseFailure = 0b0100;
             return terminate(responseFailure, failure);
         }
     }
 
     /**
      * This method needs to atomically compute whether this exchange is completed,
      * that is both request and responses are completed (either with a success or
      * a failure).
      *
      * Furthermore, this method needs to atomically compute whether the exchange
      * has completed successfully (both request and response are successful) or not.
      *
      * To do this, we use 2 bits for the request (one to indicate completion, one
      * to indicate success), and similarly for the response.
      * By using {@link AtomicInteger} to atomically sum these codes we can know
      * whether the exchange is completed and whether is successful.
      *
      * @return the {@link Result} - if any - associated with the status
      */
     private Result terminate(int code, Throwable failure)
     {
         int current = update(code, failure);
         int terminated = 0b0101;
         if ((current & terminated) == terminated)
         {
             // Request and response terminated
             LOG.debug("{} terminated", this);
             return new Result(getRequest(), getRequestFailure(), getResponse(), getResponseFailure());
         }
         return null;
     }
 
     private int update(int code, Throwable failure)
     {
         int current;
         while (true)
         {
             current = complete.get();
             boolean updateable = (current & code) == 0;
             if (updateable)
             {
                 int candidate = current | code;
                 if (!complete.compareAndSet(current, candidate))
                     continue;
                 current = candidate;
                 if ((code & 0b01) == 0b01)
                     requestFailure = failure;
                 if ((code & 0b0100) == 0b0100)
                     responseFailure = failure;
                 LOG.debug("{} updated", this);
             }
             break;
         }
         return current;
     }
 
     public boolean abort(Throwable cause)
     {
         if (destination.remove(this))
         {
             LOG.debug("Aborting while queued {}: {}", this, cause);
             return fail(cause);
         }
         else
         {
             HttpChannel channel = this.channel.get();
             if (channel == null)
                 return fail(cause);
 
             boolean aborted = channel.abort(cause);
             LOG.debug("Aborted while active ({}) {}: {}", aborted, this, cause);
             return aborted;
         }
     }
 
     private boolean fail(Throwable cause)
     {
         if (update(0b0101, cause) == 0b0101)
         {
             LOG.debug("Failing {}: {}", this, cause);
             destination.getRequestNotifier().notifyFailure(request, cause);
             List<Response.ResponseListener> listeners = getConversation().getResponseListeners();
             ResponseNotifier responseNotifier = destination.getResponseNotifier();
             responseNotifier.notifyFailure(listeners, response, cause);
             responseNotifier.notifyComplete(listeners, new Result(request, cause, response, cause));
             return true;
         }
         else
         {
             return false;
         }
     }
 
     public void resetResponse(boolean success)
     {
         responseComplete.set(false);
         int responseSuccess = 0b1100;
         int responseFailure = 0b0100;
         int code = success ? responseSuccess : responseFailure;
         complete.addAndGet(-code);
     }
 
     public void proceed(Throwable failure)
     {
         HttpChannel channel = this.channel.get();
         if (channel != null)
             channel.proceed(this, failure);
     }
 
     private String toString(int code)
     {
         String padding = "0000";
         String status = Integer.toBinaryString(code);
         return String.format("%s@%x status=%s%s",
                 HttpExchange.class.getSimpleName(),
                 hashCode(),
                 padding.substring(status.length()),
                 status);
     }
 
     @Override
     public String toString()
     {
         return toString(complete.get());
     }
 }