//
   //  ========================================================================
   //  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.mux;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  import org.eclipse.jetty.io.ArrayByteBufferPool;
  import org.eclipse.jetty.io.ByteBufferPool;
  import org.eclipse.jetty.util.BufferUtil;
  import org.eclipse.jetty.websocket.api.WriteCallback;
  import org.eclipse.jetty.websocket.api.extensions.Frame;
  import org.eclipse.jetty.websocket.api.extensions.OutgoingFrames;
  import org.eclipse.jetty.websocket.common.WebSocketFrame;
  import org.eclipse.jetty.websocket.common.extensions.mux.op.MuxAddChannelRequest;
  import org.eclipse.jetty.websocket.common.extensions.mux.op.MuxAddChannelResponse;
  import org.eclipse.jetty.websocket.common.extensions.mux.op.MuxDropChannel;
  import org.eclipse.jetty.websocket.common.extensions.mux.op.MuxFlowControl;
  import org.eclipse.jetty.websocket.common.extensions.mux.op.MuxNewChannelSlot;
  
  /**
   * Generate Mux frames destined for the physical connection.
   */
  public class MuxGenerator
  {
      private static final int CONTROL_BUFFER_SIZE = 2 * 1024;
      /** 4 bytes for channel ID + 1 for fin/rsv/opcode */
      private static final int DATA_FRAME_OVERHEAD = 5;
      private ByteBufferPool bufferPool;
      private OutgoingFrames outgoing;
  
      public MuxGenerator()
      {
          this(new ArrayByteBufferPool());
      }
  
      public MuxGenerator(ByteBufferPool bufferPool)
      {
          this.bufferPool = bufferPool;
      }
  
      public void generate(long channelId, Frame frame, WriteCallback callback)
      {
          ByteBuffer muxPayload = bufferPool.acquire(frame.getPayloadLength() + DATA_FRAME_OVERHEAD,false);
          BufferUtil.flipToFill(muxPayload);
  
          // start building mux payload
          writeChannelId(muxPayload,channelId);
          byte b = (byte)(frame.isFin()?0x80:0x00); // fin
          b |= (byte)(frame.isRsv1()?0x40:0x00); // rsv1
          b |= (byte)(frame.isRsv2()?0x20:0x00); // rsv2
          b |= (byte)(frame.isRsv3()?0x10:0x00); // rsv3
          b |= (byte)(frame.getType().getOpCode() & 0x0F); // opcode
          muxPayload.put(b);
          BufferUtil.put(frame.getPayload(),muxPayload);
  
          // build muxed frame
          WebSocketFrame muxFrame = WebSocketFrame.binary();
          BufferUtil.flipToFlush(muxPayload,0);
          muxFrame.setPayload(muxPayload);
          // NOTE: the physical connection will handle masking rules for this frame.
  
          // release original buffer (no longer needed)
          bufferPool.release(frame.getPayload());
  
          // send muxed frame down to the physical connection.
          outgoing.outgoingFrame(muxFrame,callback);
      }
  
      public void generate(WriteCallback callback,MuxControlBlock... blocks) throws IOException
      {
          if ((blocks == null) || (blocks.length <= 0))
          {
              return; // nothing to do
          }
  
          ByteBuffer payload = bufferPool.acquire(CONTROL_BUFFER_SIZE,false);
          BufferUtil.flipToFill(payload);
  
          writeChannelId(payload,0); // control channel
  
          for (MuxControlBlock block : blocks)
          {
             switch (block.getOpCode())
             {
                 case MuxOp.ADD_CHANNEL_REQUEST:
                 {
                     MuxAddChannelRequest op = (MuxAddChannelRequest)block;
                     byte b = (byte)((op.getOpCode() & 0x07) << 5); // opcode
                     b |= (byte)((op.getRsv() & 0x07) << 2); // rsv
                     b |= (op.getEncoding() & 0x03); // enc
                     payload.put(b); // opcode + rsv + enc
                     writeChannelId(payload,op.getChannelId());
                     write139Buffer(payload,op.getHandshake());
                     break;
                 }
                 case MuxOp.ADD_CHANNEL_RESPONSE:
                 {
                     MuxAddChannelResponse op = (MuxAddChannelResponse)block;
                     byte b = (byte)((op.getOpCode() & 0x07) << 5); // opcode
                     b |= (op.isFailed()?0x10:0x00); // failure bit
                     b |= (byte)((op.getRsv() & 0x03) << 2); // rsv
                     b |= (op.getEncoding() & 0x03); // enc
                     payload.put(b); // opcode + f + rsv + enc
                     writeChannelId(payload,op.getChannelId());
                     if (op.getHandshake() != null)
                     {
                         write139Buffer(payload,op.getHandshake());
                     }
                     else
                     {
                         // no handshake details
                         write139Size(payload,0);
                     }
                     break;
                 }
                 case MuxOp.DROP_CHANNEL:
                 {
                     MuxDropChannel op = (MuxDropChannel)block;
                     byte b = (byte)((op.getOpCode() & 0x07) << 5); // opcode
                     b |= (byte)(op.getRsv() & 0x1F); // rsv
                     payload.put(b); // opcode + rsv
                     writeChannelId(payload,op.getChannelId());
                     write139Buffer(payload,op.asReasonBuffer());
                     break;
                 }
                 case MuxOp.FLOW_CONTROL:
                 {
                     MuxFlowControl op = (MuxFlowControl)block;
                     byte b = (byte)((op.getOpCode() & 0x07) << 5); // opcode
                     b |= (byte)(op.getRsv() & 0x1F); // rsv
                     payload.put(b); // opcode + rsv
                     writeChannelId(payload,op.getChannelId());
                     write139Size(payload,op.getSendQuotaSize());
                     break;
                 }
                 case MuxOp.NEW_CHANNEL_SLOT:
                 {
                     MuxNewChannelSlot op = (MuxNewChannelSlot)block;
                     byte b = (byte)((op.getOpCode() & 0x07) << 5); // opcode
                     b |= (byte)(op.getRsv() & 0x0F) << 1; // rsv
                     b |= (byte)(op.isFallback()?0x01:0x00); // fallback bit
                     payload.put(b); // opcode + rsv + fallback bit
                     write139Size(payload,op.getNumberOfSlots());
                     write139Size(payload,op.getInitialSendQuota());
                     break;
                 }
             }
         }
         BufferUtil.flipToFlush(payload,0);
         WebSocketFrame frame = WebSocketFrame.binary();
         frame.setPayload(payload);
         outgoing.outgoingFrame(frame,callback);
     }
 
     public OutgoingFrames getOutgoing()
     {
         return outgoing;
     }
 
     public void setOutgoing(OutgoingFrames outgoing)
     {
         this.outgoing = outgoing;
     }
 
     /**
      * Write a 1/3/9 encoded size, then a byte buffer of that size.
      * 
      * @param payload
      * @param buffer
      */
     public void write139Buffer(ByteBuffer payload, ByteBuffer buffer)
     {
         write139Size(payload,buffer.remaining());
         writeBuffer(payload,buffer);
     }
 
     /**
      * Write a 1/3/9 encoded size.
      * 
      * @param payload
      * @param size
      */
     public void write139Size(ByteBuffer payload, long size)
     {
         if (size > 0xFF_FF)
         {
             // 9 byte encoded
             payload.put((byte)0x7F);
             payload.putLong(size);
             return;
         }
 
         if (size >= 0x7E)
         {
             // 3 byte encoded
             payload.put((byte)0x7E);
             payload.put((byte)(size >> 8));
             payload.put((byte)(size & 0xFF));
             return;
         }
 
         // 1 byte (7 bit) encoded
         payload.put((byte)(size & 0x7F));
     }
 
     public void writeBuffer(ByteBuffer payload, ByteBuffer buffer)
     {
         BufferUtil.put(buffer,payload);
     }
 
     /**
      * Write multiplexing channel id, using logical channel id encoding (of 1,2,3, or 4 octets)
      * 
      * @param payload
      * @param channelId
      */
     public void writeChannelId(ByteBuffer payload, long channelId)
     {
         if (channelId > 0x1F_FF_FF_FF)
         {
             throw new MuxException("Illegal Channel ID: too big");
         }
 
         if (channelId > 0x1F_FF_FF)
         {
             // 29 bit channel id (4 bytes)
             payload.put((byte)(0xE0 | ((channelId >> 24) & 0x1F)));
             payload.put((byte)((channelId >> 16) & 0xFF));
             payload.put((byte)((channelId >> 8) & 0xFF));
             payload.put((byte)(channelId & 0xFF));
             return;
         }
 
         if (channelId > 0x3F_FF)
         {
             // 21 bit channel id (3 bytes)
             payload.put((byte)(0xC0 | ((channelId >> 16) & 0x1F)));
             payload.put((byte)((channelId >> 8) & 0xFF));
             payload.put((byte)(channelId & 0xFF));
             return;
         }
 
         if (channelId > 0x7F)
         {
             // 14 bit channel id (2 bytes)
             payload.put((byte)(0x80 | ((channelId >> 8) & 0x3F)));
             payload.put((byte)(channelId & 0xFF));
             return;
         }
 
         // 7 bit channel id
         payload.put((byte)(channelId & 0x7F));
     }
 }