//========================================================================
   //Copyright 2011-2012 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.spdy.generator;
  
  import java.nio.ByteBuffer;
  
  import org.eclipse.jetty.spdy.ByteBufferPool;
  import org.eclipse.jetty.spdy.api.SPDY;
  import org.eclipse.jetty.spdy.api.Settings;
  import org.eclipse.jetty.spdy.frames.ControlFrame;
  import org.eclipse.jetty.spdy.frames.SettingsFrame;
  
  public class SettingsGenerator extends ControlFrameGenerator
  {
      public SettingsGenerator(ByteBufferPool bufferPool)
      {
          super(bufferPool);
      }
  
      @Override
      public ByteBuffer generate(ControlFrame frame)
      {
          SettingsFrame settingsFrame = (SettingsFrame)frame;
  
          Settings settings = settingsFrame.getSettings();
          int size = settings.size();
          int frameBodyLength = 4 + 8 * size;
          int totalLength = ControlFrame.HEADER_LENGTH + frameBodyLength;
          ByteBuffer buffer = getByteBufferPool().acquire(totalLength, true);
          generateControlFrameHeader(settingsFrame, frameBodyLength, buffer);
  
          buffer.putInt(size);
  
          for (Settings.Setting setting : settings)
          {
              int id = setting.id().code();
              byte flags = setting.flag().code();
              int idAndFlags = convertIdAndFlags(frame.getVersion(), id, flags);
              buffer.putInt(idAndFlags);
              buffer.putInt(setting.value());
          }
  
          buffer.flip();
          return buffer;
      }
  
      private int convertIdAndFlags(short version, int id, byte flags)
      {
          switch (version)
          {
              case SPDY.V2:
              {
                  // In v2 the format is 24 bits of ID + 8 bits of flag
                  int idAndFlags = (id << 8) + (flags & 0xFF);
                  // A bug in the Chromium implementation forces v2 to have
                  // the 3 ID bytes little endian, so we swap first and third
                  int result = idAndFlags & 0x00_FF_00_FF;
                  result += (idAndFlags & 0xFF_00_00_00) >>> 16;
                  result += (idAndFlags & 0x00_00_FF_00) << 16;
                  return result;
              }
              case SPDY.V3:
              {
                  // In v3 the format is 8 bits of flags + 24 bits of ID
                  return (flags << 24) + (id & 0xFF_FF_FF);
              }
              default:
              {
                  throw new IllegalStateException();
              }
          }
      }
  }