/*
    * Copyright (c) 2012 the original author or authors.
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.eclipse.jetty.spdy.generator;
  
  import java.nio.ByteBuffer;
  
  import org.eclipse.jetty.spdy.ByteBufferPool;
  import org.eclipse.jetty.spdy.SessionException;
  import org.eclipse.jetty.spdy.api.SPDY;
  import org.eclipse.jetty.spdy.api.SessionStatus;
  import org.eclipse.jetty.spdy.frames.ControlFrame;
  import org.eclipse.jetty.spdy.frames.SynReplyFrame;
  
  public class SynReplyGenerator extends ControlFrameGenerator
  {
      private final HeadersBlockGenerator headersBlockGenerator;
  
      public SynReplyGenerator(ByteBufferPool bufferPool, HeadersBlockGenerator headersBlockGenerator)
      {
          super(bufferPool);
          this.headersBlockGenerator = headersBlockGenerator;
      }
  
      @Override
      public ByteBuffer generate(ControlFrame frame)
      {
          SynReplyFrame synReply = (SynReplyFrame)frame;
          short version = synReply.getVersion();
  
          ByteBuffer headersBuffer = headersBlockGenerator.generate(version, synReply.getHeaders());
  
          int frameBodyLength = getFrameDataLength(version);
  
          int frameLength = frameBodyLength + headersBuffer.remaining();
          if (frameLength > 0xFF_FF_FF)
          {
              // Too many headers, but unfortunately we have already modified the compression
              // context, so we have no other choice than tear down the connection.
              throw new SessionException(SessionStatus.PROTOCOL_ERROR, "Too many headers");
          }
  
          int totalLength = ControlFrame.HEADER_LENGTH + frameLength;
  
          ByteBuffer buffer = getByteBufferPool().acquire(totalLength, true);
          generateControlFrameHeader(synReply, frameLength, buffer);
  
          buffer.putInt(synReply.getStreamId() & 0x7F_FF_FF_FF);
          writeAdditional(version, buffer);
  
          buffer.put(headersBuffer);
  
          buffer.flip();
          return buffer;
      }
  
      private int getFrameDataLength(short version)
      {
          switch (version)
          {
              case SPDY.V2:
                  return 6;
              case SPDY.V3:
                  return 4;
              default:
                  // Here the version is trusted to be correct; if it's not
                  // then it's a bug rather than an application error
                  throw new IllegalStateException();
          }
      }
  
      private void writeAdditional(short version, ByteBuffer buffer)
      {
          switch (version)
          {
              case SPDY.V2:
                  buffer.putShort((short)0);
                  break;
              case SPDY.V3:
                  break;
              default:
                  // Here the version is trusted to be correct; if it's not
                  // then it's a bug rather than an application error
                  throw new IllegalStateException();
          }
      }
 }