//
// async_tcp_echo_server.cpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#include <cstdlib>
#include <iostream>
#include <boost/bind/bind.hpp>
#include "asio.hpp"

using asio::ip::tcp;

class session
{
public:
  session(asio::io_context& io_context)
    : socket_(io_context)
  {
  }

  tcp::socket& socket()
  {
    return socket_;
  }

  void start()
  {
    socket_.async_read_some(asio::buffer(data_, max_length),
        boost::bind(&session::handle_read, this,
          asio::placeholders::error,
          asio::placeholders::bytes_transferred));
  }

private:
  void handle_read(const asio::error_code& error,
      size_t bytes_transferred)
  {
    if (!error)
    {
      asio::async_write(socket_,
          asio::buffer(data_, bytes_transferred),
          boost::bind(&session::handle_write, this,
            asio::placeholders::error));
    }
    else
    {
      delete this;
    }
  }

  void handle_write(const asio::error_code& error)
  {
    if (!error)
    {
      socket_.async_read_some(asio::buffer(data_, max_length),
          boost::bind(&session::handle_read, this,
            asio::placeholders::error,
            asio::placeholders::bytes_transferred));
    }
    else
    {
      delete this;
    }
  }

  tcp::socket socket_;
  enum { max_length = 1024 };
  char data_[max_length];
};

class server
{
public:
  server(asio::io_context& io_context, short port)
    : io_context_(io_context),
      acceptor_(io_context, tcp::endpoint(tcp::v4(), port))
  {
    start_accept();
  }

private:
  void start_accept()
  {
    session* new_session = new session(io_context_);
    acceptor_.async_accept(new_session->socket(),
        boost::bind(&server::handle_accept, this, new_session,
          asio::placeholders::error));
  }

  void handle_accept(session* new_session,
      const asio::error_code& error)
  {
    if (!error)
    {
      new_session->start();
    }
    else
    {
      delete new_session;
    }

    start_accept();
  }

  asio::io_context& io_context_;
  tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 2)
    {
      std::cerr << "Usage: async_tcp_echo_server <port>\n";
      return 1;
    }

    asio::io_context io_context;

    using namespace std; // For atoi.
    server s(io_context, atoi(argv[1]));

    io_context.run();
  }
  catch (std::exception& e)
  {
    std::cerr << "Exception: " << e.what() << "\n";
  }

  return 0;
}
