path: root/websocket.h

#pragma once

#include "error.h"

#include <boost/asio/buffer.hpp>
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/beast/websocket/ssl.hpp>
#include <boost/beast/ssl/ssl_stream.hpp>
#include <boost/asio/buffers_iterator.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/dispatch.hpp>
#include <boost/asio/ssl/context.hpp>
#include <boost/beast/ssl.hpp>
#include <boost/asio/strand.hpp>
#include <boost/config.hpp>

#include <algorithm>
#include <cstddef>
#include <cstdlib>
#include <filesystem>
#include <functional>
#include <iostream>
#include <memory>
#include <optional>
#include <string>
#include <thread>
#include <vector>

namespace beast = boost::beast;         // from <boost/beast.hpp>
namespace http = beast::http;           // from <boost/beast/http.hpp>
namespace net = boost::asio;            // from <boost/asio.hpp>
namespace ssl = boost::asio::ssl;       // from <boost/asio/ssl.hpp>
namespace websocket = beast::websocket;
using tcp = boost::asio::ip::tcp;       // from <boost/asio/ip/tcp.hpp>
using namespace std::placeholders;

// Server session, asynchronous, proxying
class websocket_session: public std::enable_shared_from_this<websocket_session>
{
 boost::asio::io_context& ioc_;
 boost::asio::ip::tcp::resolver resolver_;
 boost::beast::websocket::stream<beast::ssl_stream<beast::tcp_stream>> ws_in_;
 boost::beast::flat_buffer buffer_in_;
 boost::beast::websocket::stream<beast::tcp_stream> ws_app_;
 boost::beast::flat_buffer buffer_out_;
 std::string host_;
 std::string port_;

public:
 explicit websocket_session(boost::asio::io_context& ioc, beast::ssl_stream<beast::tcp_stream>&& stream):
  ioc_(ioc),
  resolver_(boost::asio::make_strand(ioc_)),
  ws_in_(std::move(stream)),
  ws_app_(boost::asio::make_strand(ioc_)),
  host_{"::1"},
  port_{"9876"}
 {
 }

 //
 // The initial setup path
 //
 
 // Start the asynchronous accept operation
 template<class Body, class Allocator>
 void do_accept_in(http::request<Body, http::basic_fields<Allocator>> req)
 {
  // Set suggested timeout settings for the websocket
  ws_in_.set_option(
      websocket::stream_base::timeout::suggested(
          beast::role_type::server));

  // Set a decorator to change the Server of the handshake
  ws_in_.set_option(websocket::stream_base::decorator(
      [](websocket::response_type& res)
      {
          res.set(http::field::server,
              std::string{"Reichwein.IT Webserver"});
      }));

  // Accept the websocket handshake
  ws_in_.async_accept(
      req,
      beast::bind_front_handler(
          &websocket_session::on_accept_in,
          shared_from_this()));
 }

private:
 void on_accept_in(beast::error_code ec)
 {
  if (ec)
   return fail(ec, "accept in");

  resolver_.async_resolve(host_, port_,
                          beast::bind_front_handler(&websocket_session::on_resolve_app, shared_from_this()));
 }
 
 void on_resolve_app(beast::error_code ec, tcp::resolver::results_type results)
 {
  if (ec)
   return fail(ec, "resolve app");

  beast::get_lowest_layer(ws_app_).async_connect(results,
                          beast::bind_front_handler(&websocket_session::on_connect_app, shared_from_this()));
 }

 void on_connect_app(beast::error_code ec, tcp::resolver::results_type::endpoint_type endpoint)
 {
  if (ec)
   return fail(ec, "connect app");

  beast::get_lowest_layer(ws_app_).expires_never();

  host_ += ':' + std::to_string(endpoint.port());

  // Set suggested timeout settings for the websocket
  ws_app_.set_option(
      websocket::stream_base::timeout::suggested(
	  beast::role_type::client));

  ws_app_.set_option(boost::beast::websocket::stream_base::decorator(
   [](boost::beast::websocket::request_type& req)
   {
    req.set(boost::beast::http::field::user_agent, "Reichwein.IT Webserver Websocket client");
   }));

  ws_app_.async_handshake(host_, "/",
                          beast::bind_front_handler(&websocket_session::on_handshake_app, shared_from_this()));
 }

 void on_handshake_app(beast::error_code ec)
 {
  if (ec)
   return fail(ec, "handshake app");

  // Start reading messages from both sides, asynchronously
  do_read_in();
  do_read_app();
 }

 //
 // The input path (client,ws_in_ -> app,ws_app_) via
 //
 
 void
 do_read_in()
 {
  // Read a message into our buffer
  ws_in_.async_read(
      buffer_in_,
      beast::bind_front_handler(
          &websocket_session::on_read_in,
          shared_from_this()));
 }

 void
 on_read_in(
     beast::error_code ec,
     std::size_t bytes_transferred)
 {
  boost::ignore_unused(bytes_transferred);

  // This indicates that the websocket_session was closed
  if (ec == websocket::error::closed)
   return;

  if (ec)
   fail(ec, "read in");

  ws_app_.text(ws_in_.got_text());
  
  do_write_app();
 }
 
 void do_write_app()
 {
  ws_app_.async_write(buffer_in_.data(),
      beast::bind_front_handler(
          &websocket_session::on_write_app,
          shared_from_this()));
 }

 void on_write_app(beast::error_code ec, std::size_t bytes_transferred)
 {
  boost::ignore_unused(bytes_transferred);

  if (ec)
   fail(ec, "write app");

  buffer_in_.consume(buffer_in_.size());

  // Do another read
  do_read_in();
 }

 //
 // The output path (app,ws_app_ -> client,ws_in_)
 //
 
 void do_read_app()
 {
  // Read a message into our buffer
  ws_app_.async_read(
      buffer_out_,
      beast::bind_front_handler(
          &websocket_session::on_read_app,
          shared_from_this()));
 }

 void on_read_app(beast::error_code ec, std::size_t bytes_transferred)
 {
  boost::ignore_unused(bytes_transferred);

  if (ec == websocket::error::closed)
   return;

  if (ec)
   fail(ec, "read app");

  do_write_out();
 }

 void do_write_out()
 {
  ws_in_.async_write(buffer_out_.data(),
      beast::bind_front_handler(
          &websocket_session::on_write_out,
          shared_from_this()));
 }

 void on_write_out(
     beast::error_code ec,
     std::size_t bytes_transferred)
 {
  boost::ignore_unused(bytes_transferred);

  if(ec)
   return fail(ec, "write out");

  // Clear the buffer
  buffer_out_.consume(buffer_out_.size());

  // Do another read
  do_read_app();
 }

}; // class