/*
    * 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.example.http.websocketx.server;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufUtil;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPipeline;
  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.HttpHeaderNames;
  import io.netty.handler.codec.http.HttpHeaderValues;
  import io.netty.handler.codec.http.HttpRequest;
  import io.netty.handler.codec.http.HttpResponseStatus;
  import io.netty.handler.codec.http.HttpUtil;
  import io.netty.handler.ssl.SslHandler;
  
  import static io.netty.handler.codec.http.HttpHeaderNames.*;
  import static io.netty.handler.codec.http.HttpMethod.*;
  import static io.netty.handler.codec.http.HttpResponseStatus.*;
  
  /**
   * Outputs index page content.
   */
  public class WebSocketIndexPageHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
  
      private final String websocketPath;
  
      public WebSocketIndexPageHandler(String websocketPath) {
          this.websocketPath = websocketPath;
      }
  
      @Override
      protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest req) throws Exception {
          // Handle a bad request.
          if (!req.decoderResult().isSuccess()) {
              sendHttpResponse(ctx, req, new DefaultFullHttpResponse(req.protocolVersion(), BAD_REQUEST,
                                                                     ctx.alloc().buffer(0)));
              return;
          }
  
          // Handle websocket upgrade request.
          if (req.headers().contains(HttpHeaderNames.UPGRADE, HttpHeaderValues.WEBSOCKET, true)) {
              ctx.fireChannelRead(req.retain());
              return;
          }
  
          // Allow only GET methods.
          if (!GET.equals(req.method())) {
              sendHttpResponse(ctx, req, new DefaultFullHttpResponse(req.protocolVersion(), FORBIDDEN,
                                                                     ctx.alloc().buffer(0)));
              return;
          }
  
          // Send the index page
          if ("/".equals(req.uri()) || "/index.html".equals(req.uri())) {
              String webSocketLocation = getWebSocketLocation(ctx.pipeline(), req, websocketPath);
              ByteBuf content = WebSocketServerIndexPage.getContent(webSocketLocation);
              FullHttpResponse res = new DefaultFullHttpResponse(req.protocolVersion(), OK, content);
  
              res.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");
              HttpUtil.setContentLength(res, content.readableBytes());
  
              sendHttpResponse(ctx, req, res);
          } else {
              sendHttpResponse(ctx, req, new DefaultFullHttpResponse(req.protocolVersion(), NOT_FOUND,
                                                                     ctx.alloc().buffer(0)));
          }
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
          cause.printStackTrace();
          ctx.close();
      }
  
      private static void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req, FullHttpResponse res) {
          // Generate an error page if response getStatus code is not OK (200).
          HttpResponseStatus responseStatus = res.status();
          if (responseStatus.code() != 200) {
              ByteBufUtil.writeUtf8(res.content(), responseStatus.toString());
              HttpUtil.setContentLength(res, res.content().readableBytes());
         }
         // Send the response and close the connection if necessary.
         boolean keepAlive = HttpUtil.isKeepAlive(req) && responseStatus.code() == 200;
         HttpUtil.setKeepAlive(res, keepAlive);
         ChannelFuture future = ctx.writeAndFlush(res);
         if (!keepAlive) {
             future.addListener(ChannelFutureListener.CLOSE);
         }
     }
 
     private static String getWebSocketLocation(ChannelPipeline cp, HttpRequest req, String path) {
         String protocol = "ws";
         if (cp.get(SslHandler.class) != null) {
             // SSL in use so use Secure WebSockets
             protocol = "wss";
         }
         return protocol + "://" + req.headers().get(HttpHeaderNames.HOST) + path;
     }
 }