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   /*
    * Copyright 2014 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.example.spdy.client;
  
  import io.netty.channel.ChannelDuplexHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPromise;
  import io.netty.handler.codec.spdy.SpdyFrame;
  import io.netty.util.internal.ObjectUtil;
  import io.netty.util.internal.logging.InternalLogLevel;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  /**
   * Logs SPDY frames for debugging purposes.
   */
  public class SpdyFrameLogger extends ChannelDuplexHandler {
  
      private enum Direction {
          INBOUND, OUTBOUND
      }
  
      protected final InternalLogger logger;
      private final InternalLogLevel level;
  
      public SpdyFrameLogger(InternalLogLevel level) {
          this.level = ObjectUtil.checkNotNull(level, "level");
          this.logger = InternalLoggerFactory.getInstance(getClass());
      }
  
      @Override
      public void channelRead(ChannelHandlerContext ctx, Object msg) {
          if (acceptMessage(msg)) {
              log((SpdyFrame) msg, Direction.INBOUND);
          }
          ctx.fireChannelRead(msg);
      }
  
      @Override
      public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
          if (acceptMessage(msg)) {
              log((SpdyFrame) msg, Direction.OUTBOUND);
          }
          ctx.write(msg, promise);
      }
  
      private static boolean acceptMessage(Object msg) {
          return msg instanceof SpdyFrame;
      }
  
      private void log(SpdyFrame msg, Direction d) {
          if (logger.isEnabled(level)) {
              StringBuilder b = new StringBuilder(200)
                  .append("\n----------------")
                  .append(d.name())
                  .append("--------------------\n")
                  .append(msg)
                  .append("\n------------------------------------");
  
              logger.log(level, b.toString());
          }
      }
  }