//
   //  ========================================================================
   //  Copyright (c) 1995-2013 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.websocket.common.extensions.compress;
  
  
  import java.nio.ByteBuffer;
  
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  import org.eclipse.jetty.websocket.api.WriteCallback;
  import org.eclipse.jetty.websocket.api.extensions.ExtensionConfig;
  import org.eclipse.jetty.websocket.api.extensions.Frame;
  import org.eclipse.jetty.websocket.common.WebSocketFrame;
  import org.eclipse.jetty.websocket.common.extensions.AbstractExtension;
  
  /**
   * Per Message Compression extension for WebSocket.
   * <p>
   * Attempts to follow <a href="https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression-01">draft-ietf-hybi-permessage-compression-01</a>
   */
  public class MessageCompressionExtension extends AbstractExtension
  {
      private static final Logger LOG = Log.getLogger(MessageCompressionExtension.class);
  
      private CompressionMethod method;
  
      @Override
      public void incomingFrame(Frame frame)
      {
          if (frame.getType().isControl() || !frame.isRsv1())
          {
              // Cannot modify incoming control frames or ones with RSV1 set.
              nextIncomingFrame(frame);
              return;
          }
  
          ByteBuffer data = frame.getPayload();
          method.decompress().input(data);
          while (!method.decompress().isDone())
          {
              ByteBuffer uncompressed = method.decompress().process();
              if (uncompressed == null)
              {
                  continue;
              }
              WebSocketFrame out = new WebSocketFrame(frame).setPayload(uncompressed);
              if (!method.decompress().isDone())
              {
                  out.setFin(false);
              }
              out.setRsv1(false); // Unset RSV1 on decompressed frame
              nextIncomingFrame(out);
          }
  
          // reset only at the end of a message.
          if (frame.isFin())
          {
              method.decompress().end();
          }
      }
  
      /**
       * Indicates use of RSV1 flag for indicating deflation is in use.
       */
      @Override
      public boolean isRsv1User()
      {
          return true;
      }
  
      @Override
      public boolean isTextDataDecoder()
      {
          // this extension is responsible for text data frames
          return true;
      }
  
      @Override
      public void outgoingFrame(Frame frame, WriteCallback callback)
      {
          if (frame.getType().isControl())
          {
              // skip, cannot compress control frames.
             nextOutgoingFrame(frame,callback);
             return;
         }
 
         ByteBuffer data = frame.getPayload();
         // deflate data
         method.compress().input(data);
         while (!method.compress().isDone())
         {
             ByteBuffer buf = method.compress().process();
             WebSocketFrame out = new WebSocketFrame(frame).setPayload(buf);
             out.setRsv1(true);
             if (!method.compress().isDone())
             {
                 out.setFin(false);
                 // no callback for start/middle frames
                 nextOutgoingFrame(out,null);
             }
             else
             {
                 // pass through callback to last frame
                 nextOutgoingFrame(out,callback);
             }
         }
 
         // reset only at end of message
         if (frame.isFin())
         {
             method.compress().end();
         }
     }
 
     @Override
     public void setConfig(ExtensionConfig config)
     {
         super.setConfig(config);
 
         String methodOptions = config.getParameter("method","deflate");
         LOG.debug("Method requested: {}",methodOptions);
 
         method = new DeflateCompressionMethod();
     }
 
     @Override
     public String toString()
     {
         return String.format("%s[method=%s]",this.getClass().getSimpleName(),method);
     }
 }