/*
    * 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.stomp;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.codec.stomp.DefaultStompFrame;
  import io.netty.handler.codec.stomp.StompCommand;
  import io.netty.handler.codec.stomp.StompFrame;
  import io.netty.handler.codec.stomp.StompHeaders;
  
  /**
   * STOMP client inbound handler implementation, which just passes received messages to listener
   */
  public class StompClientHandler extends SimpleChannelInboundHandler<StompFrame> {
  
      private enum ClientState {
          AUTHENTICATING,
          AUTHENTICATED,
          SUBSCRIBED,
          DISCONNECTING
      }
  
      private ClientState state;
  
      @Override
      public void channelActive(ChannelHandlerContext ctx) throws Exception {
          state = ClientState.AUTHENTICATING;
          StompFrame connFrame = new DefaultStompFrame(StompCommand.CONNECT);
          connFrame.headers().set(StompHeaders.ACCEPT_VERSION, "1.2");
          connFrame.headers().set(StompHeaders.HOST, StompClient.HOST);
          connFrame.headers().set(StompHeaders.LOGIN, StompClient.LOGIN);
          connFrame.headers().set(StompHeaders.PASSCODE, StompClient.PASSCODE);
          ctx.writeAndFlush(connFrame);
      }
  
      @Override
      protected void channelRead0(ChannelHandlerContext ctx, StompFrame frame) throws Exception {
          String subscrReceiptId = "001";
          String disconReceiptId = "002";
          switch (frame.command()) {
              case CONNECTED:
                  StompFrame subscribeFrame = new DefaultStompFrame(StompCommand.SUBSCRIBE);
                  subscribeFrame.headers().set(StompHeaders.DESTINATION, StompClient.TOPIC);
                  subscribeFrame.headers().set(StompHeaders.RECEIPT, subscrReceiptId);
                  subscribeFrame.headers().set(StompHeaders.ID, "1");
                  System.out.println("connected, sending subscribe frame: " + subscribeFrame);
                  state = ClientState.AUTHENTICATED;
                  ctx.writeAndFlush(subscribeFrame);
                  break;
              case RECEIPT:
                  String receiptHeader = frame.headers().getAsString(StompHeaders.RECEIPT_ID);
                  if (state == ClientState.AUTHENTICATED && receiptHeader.equals(subscrReceiptId)) {
                      StompFrame msgFrame = new DefaultStompFrame(StompCommand.SEND);
                      msgFrame.headers().set(StompHeaders.DESTINATION, StompClient.TOPIC);
                      msgFrame.content().writeBytes("some payload".getBytes());
                      System.out.println("subscribed, sending message frame: " + msgFrame);
                      state = ClientState.SUBSCRIBED;
                      ctx.writeAndFlush(msgFrame);
                  } else if (state == ClientState.DISCONNECTING && receiptHeader.equals(disconReceiptId)) {
                      System.out.println("disconnected");
                      ctx.close();
                  } else {
                      throw new IllegalStateException("received: " + frame + ", while internal state is " + state);
                  }
                  break;
              case MESSAGE:
                  if (state == ClientState.SUBSCRIBED) {
                      System.out.println("received frame: " + frame);
                      StompFrame disconnFrame = new DefaultStompFrame(StompCommand.DISCONNECT);
                      disconnFrame.headers().set(StompHeaders.RECEIPT, disconReceiptId);
                      System.out.println("sending disconnect frame: " + disconnFrame);
                      state = ClientState.DISCONNECTING;
                      ctx.writeAndFlush(disconnFrame);
                  }
                  break;
              default:
                  break;
          }
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
          cause.printStackTrace();
          ctx.close();
      }
 }