/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.handler.codec.http.websocketx;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelHandler.Sharable;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.MessageToMessageEncoder;
  
  import java.util.List;
  
  /**
   * Encodes a {@link WebSocketFrame} into a {@link ByteBuf}.
   * <p>
   * For the detailed instruction on adding add Web Socket support to your HTTP server, take a look into the
   * <tt>WebSocketServer</tt> example located in the {@code io.netty.example.http.websocket} package.
   */
  @Sharable
  public class WebSocket00FrameEncoder extends MessageToMessageEncoder<WebSocketFrame> implements WebSocketFrameEncoder {
      private static final ByteBuf _0X00 = Unpooled.unreleasableBuffer(
              Unpooled.directBuffer(1, 1).writeByte(0x00)).asReadOnly();
      private static final ByteBuf _0XFF = Unpooled.unreleasableBuffer(
              Unpooled.directBuffer(1, 1).writeByte((byte) 0xFF)).asReadOnly();
      private static final ByteBuf _0XFF_0X00 = Unpooled.unreleasableBuffer(
              Unpooled.directBuffer(2, 2).writeByte((byte) 0xFF).writeByte(0x00)).asReadOnly();
  
      @Override
      protected void encode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
          if (msg instanceof TextWebSocketFrame) {
              // Text frame
              ByteBuf data = msg.content();
  
              out.add(_0X00.duplicate());
              out.add(data.retain());
              out.add(_0XFF.duplicate());
          } else if (msg instanceof CloseWebSocketFrame) {
              // Close frame, needs to call duplicate to allow multiple writes.
              // See https://github.com/netty/netty/issues/2768
              out.add(_0XFF_0X00.duplicate());
          } else {
              // Binary frame
              ByteBuf data = msg.content();
              int dataLen = data.readableBytes();
  
              ByteBuf buf = ctx.alloc().buffer(5);
              boolean release = true;
              try {
                  // Encode type.
                  buf.writeByte((byte) 0x80);
  
                  // Encode length.
                  int b1 = dataLen >>> 28 & 0x7F;
                  int b2 = dataLen >>> 14 & 0x7F;
                  int b3 = dataLen >>> 7 & 0x7F;
                  int b4 = dataLen & 0x7F;
                  if (b1 == 0) {
                      if (b2 == 0) {
                          if (b3 != 0) {
                              buf.writeByte(b3 | 0x80);
                          }
                          buf.writeByte(b4);
                      } else {
                          buf.writeByte(b2 | 0x80);
                          buf.writeByte(b3 | 0x80);
                          buf.writeByte(b4);
                      }
                  } else {
                      buf.writeByte(b1 | 0x80);
                      buf.writeByte(b2 | 0x80);
                      buf.writeByte(b3 | 0x80);
                      buf.writeByte(b4);
                  }
  
                  // Encode binary data.
                  out.add(buf);
                  out.add(data.retain());
                  release = false;
              } finally {
                  if (release) {
                      buf.release();
                  }
              }
          }
      }
  }