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   /*
    * Copyright 2015 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.http2.tiles;
  
  import static io.netty.buffer.Unpooled.EMPTY_BUFFER;
  import static io.netty.example.http2.Http2ExampleUtil.firstValue;
  import static io.netty.example.http2.Http2ExampleUtil.toInt;
  import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
  import static io.netty.handler.codec.http.HttpUtil.setContentLength;
  import static io.netty.handler.codec.http.HttpResponseStatus.BAD_REQUEST;
  import static io.netty.handler.codec.http.HttpResponseStatus.OK;
  import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
  import static java.lang.Integer.parseInt;
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.codec.http.DefaultFullHttpResponse;
  import io.netty.handler.codec.http.FullHttpRequest;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.QueryStringDecoder;
  import io.netty.handler.codec.http2.HttpConversionUtil;
  import io.netty.handler.codec.http2.InboundHttp2ToHttpAdapter;
  
  import java.util.concurrent.TimeUnit;
  
  /**
   * Handles all the requests for data. It receives a {@link FullHttpRequest},
   * which has been converted by a {@link InboundHttp2ToHttpAdapter} before it
   * arrived here. For further details, check {@link Http2OrHttpHandler} where the
   * pipeline is setup.
   */
  public class Http2RequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
  
      private static final String LATENCY_FIELD_NAME = "latency";
      private static final int MIN_LATENCY = 0;
      private static final int MAX_LATENCY = 1000;
      private static final String IMAGE_COORDINATE_Y = "y";
      private static final String IMAGE_COORDINATE_X = "x";
  
      @Override
      protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
          QueryStringDecoder queryString = new QueryStringDecoder(request.uri());
          String streamId = streamId(request);
          int latency = toInt(firstValue(queryString, LATENCY_FIELD_NAME), 0);
          if (latency < MIN_LATENCY || latency > MAX_LATENCY) {
              sendBadRequest(ctx, streamId);
              return;
          }
          String x = firstValue(queryString, IMAGE_COORDINATE_X);
          String y = firstValue(queryString, IMAGE_COORDINATE_Y);
          if (x == null || y == null) {
              handlePage(ctx, streamId, latency, request);
          } else {
              handleImage(x, y, ctx, streamId, latency, request);
          }
      }
  
      private static void sendBadRequest(ChannelHandlerContext ctx, String streamId) {
          FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, BAD_REQUEST, EMPTY_BUFFER);
          streamId(response, streamId);
          ctx.writeAndFlush(response);
      }
  
      private void handleImage(String x, String y, ChannelHandlerContext ctx, String streamId, int latency,
              FullHttpRequest request) {
          ByteBuf image = ImageCache.INSTANCE.image(parseInt(x), parseInt(y));
          FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, image.duplicate());
          response.headers().set(CONTENT_TYPE, "image/jpeg");
          sendResponse(ctx, streamId, latency, response, request);
      }
  
      private void handlePage(ChannelHandlerContext ctx, String streamId, int latency, FullHttpRequest request) {
          byte[] body = Html.body(latency);
          ByteBuf content = ctx.alloc().buffer(Html.HEADER.length + body.length + Html.FOOTER.length);
          content.writeBytes(Html.HEADER);
          content.writeBytes(body);
          content.writeBytes(Html.FOOTER);
          FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, content);
          response.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");
          sendResponse(ctx, streamId, latency, response, request);
      }
  
      protected void sendResponse(final ChannelHandlerContext ctx, String streamId, int latency,
              final FullHttpResponse response, final FullHttpRequest request) {
          setContentLength(response, response.content().readableBytes());
         streamId(response, streamId);
         ctx.executor().schedule(new Runnable() {
             @Override
             public void run() {
                 ctx.writeAndFlush(response);
             }
         }, latency, TimeUnit.MILLISECONDS);
     }
 
     private static String streamId(FullHttpRequest request) {
         return request.headers().get(HttpConversionUtil.ExtensionHeaderNames.STREAM_ID.text());
     }
 
     private static void streamId(FullHttpResponse response, String streamId) {
         response.headers().set(HttpConversionUtil.ExtensionHeaderNames.STREAM_ID.text(), streamId);
     }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
         cause.printStackTrace();
         ctx.close();
     }
 }