/*
    * 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.http2.helloworld.server;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufUtil;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.http.FullHttpRequest;
  import io.netty.handler.codec.http.HttpHeaderNames;
  import io.netty.handler.codec.http.HttpMethod;
  import io.netty.handler.codec.http.HttpScheme;
  import io.netty.handler.codec.http.HttpServerUpgradeHandler;
  import io.netty.handler.codec.http2.DefaultHttp2Headers;
  import io.netty.handler.codec.http2.Http2ConnectionDecoder;
  import io.netty.handler.codec.http2.Http2ConnectionEncoder;
  import io.netty.handler.codec.http2.Http2ConnectionHandler;
  import io.netty.handler.codec.http2.Http2Flags;
  import io.netty.handler.codec.http2.Http2FrameListener;
  import io.netty.handler.codec.http2.Http2Headers;
  import io.netty.handler.codec.http2.Http2Settings;
  import io.netty.util.CharsetUtil;
  
  import static io.netty.buffer.Unpooled.copiedBuffer;
  import static io.netty.buffer.Unpooled.unreleasableBuffer;
  import static io.netty.handler.codec.http.HttpResponseStatus.OK;
  
  /**
   * A simple handler that responds with the message "Hello World!".
   */
  public final class HelloWorldHttp2Handler extends Http2ConnectionHandler implements Http2FrameListener {
  
      static final ByteBuf RESPONSE_BYTES = unreleasableBuffer(
              copiedBuffer("Hello World", CharsetUtil.UTF_8)).asReadOnly();
  
      HelloWorldHttp2Handler(Http2ConnectionDecoder decoder, Http2ConnectionEncoder encoder,
                             Http2Settings initialSettings) {
          super(decoder, encoder, initialSettings);
      }
  
      private static Http2Headers http1HeadersToHttp2Headers(FullHttpRequest request) {
          CharSequence host = request.headers().get(HttpHeaderNames.HOST);
          Http2Headers http2Headers = new DefaultHttp2Headers()
                  .method(HttpMethod.GET.asciiName())
                  .path(request.uri())
                  .scheme(HttpScheme.HTTP.name());
          if (host != null) {
              http2Headers.authority(host);
          }
          return http2Headers;
      }
  
      /**
       * Handles the cleartext HTTP upgrade event. If an upgrade occurred, sends a simple response via HTTP/2
       * on stream 1 (the stream specifically reserved for cleartext HTTP upgrade).
       */
      @Override
      public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
          if (evt instanceof HttpServerUpgradeHandler.UpgradeEvent) {
              HttpServerUpgradeHandler.UpgradeEvent upgradeEvent =
                      (HttpServerUpgradeHandler.UpgradeEvent) evt;
              onHeadersRead(ctx, 1, http1HeadersToHttp2Headers(upgradeEvent.upgradeRequest()), 0 , true);
          }
          super.userEventTriggered(ctx, evt);
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
          super.exceptionCaught(ctx, cause);
          cause.printStackTrace();
          ctx.close();
      }
  
      /**
       * Sends a "Hello World" DATA frame to the client.
       */
      private void sendResponse(ChannelHandlerContext ctx, int streamId, ByteBuf payload) {
          // Send a frame for the response status
          Http2Headers headers = new DefaultHttp2Headers().status(OK.codeAsText());
          encoder().writeHeaders(ctx, streamId, headers, 0, false, ctx.newPromise());
          encoder().writeData(ctx, streamId, payload, 0, true, ctx.newPromise());
  
          // no need to call flush as channelReadComplete(...) will take care of it.
      }
  
      @Override
      public int onDataRead(ChannelHandlerContext ctx, int streamId, ByteBuf data, int padding, boolean endOfStream) {
         int processed = data.readableBytes() + padding;
         if (endOfStream) {
             sendResponse(ctx, streamId, data.retain());
         }
         return processed;
     }
 
     @Override
     public void onHeadersRead(ChannelHandlerContext ctx, int streamId,
                               Http2Headers headers, int padding, boolean endOfStream) {
         if (endOfStream) {
             ByteBuf content = ctx.alloc().buffer();
             content.writeBytes(RESPONSE_BYTES.duplicate());
             ByteBufUtil.writeAscii(content, " - via HTTP/2");
             sendResponse(ctx, streamId, content);
         }
     }
 
     @Override
     public void onHeadersRead(ChannelHandlerContext ctx, int streamId, Http2Headers headers, int streamDependency,
                               short weight, boolean exclusive, int padding, boolean endOfStream) {
         onHeadersRead(ctx, streamId, headers, padding, endOfStream);
     }
 
     @Override
     public void onPriorityRead(ChannelHandlerContext ctx, int streamId, int streamDependency,
                                short weight, boolean exclusive) {
     }
 
     @Override
     public void onRstStreamRead(ChannelHandlerContext ctx, int streamId, long errorCode) {
     }
 
     @Override
     public void onSettingsAckRead(ChannelHandlerContext ctx) {
     }
 
     @Override
     public void onSettingsRead(ChannelHandlerContext ctx, Http2Settings settings) {
     }
 
     @Override
     public void onPingRead(ChannelHandlerContext ctx, long data) {
     }
 
     @Override
     public void onPingAckRead(ChannelHandlerContext ctx, long data) {
     }
 
     @Override
     public void onPushPromiseRead(ChannelHandlerContext ctx, int streamId, int promisedStreamId,
                                   Http2Headers headers, int padding) {
     }
 
     @Override
     public void onGoAwayRead(ChannelHandlerContext ctx, int lastStreamId, long errorCode, ByteBuf debugData) {
     }
 
     @Override
     public void onWindowUpdateRead(ChannelHandlerContext ctx, int streamId, int windowSizeIncrement) {
     }
 
     @Override
     public void onUnknownFrame(ChannelHandlerContext ctx, byte frameType, int streamId,
                                Http2Flags flags, ByteBuf payload) {
     }
 }