//
// transmit_file.cpp
// ~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2024 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 <ctime>
#include <functional>
#include <iostream>
#include <memory>
#include <string>
#include <boost/asio.hpp>

#if defined(BOOST_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)

using boost::asio::ip::tcp;
using boost::asio::windows::overlapped_ptr;
using boost::asio::windows::random_access_handle;

typedef boost::asio::basic_stream_socket<tcp,
    boost::asio::io_context::executor_type> tcp_socket;

typedef boost::asio::basic_socket_acceptor<tcp,
    boost::asio::io_context::executor_type> tcp_acceptor;

// A wrapper for the TransmitFile overlapped I/O operation.
template <typename Handler>
void transmit_file(tcp_socket& socket,
    random_access_handle& file, Handler handler)
{
  // Construct an OVERLAPPED-derived object to contain the handler.
  overlapped_ptr overlapped(socket.get_executor().context(), handler);

  // Initiate the TransmitFile operation.
  BOOL ok = ::TransmitFile(socket.native_handle(),
      file.native_handle(), 0, 0, overlapped.get(), 0, 0);
  DWORD last_error = ::GetLastError();

  // Check if the operation completed immediately.
  if (!ok && last_error != ERROR_IO_PENDING)
  {
    // The operation completed immediately, so a completion notification needs
    // to be posted. When complete() is called, ownership of the OVERLAPPED-
    // derived object passes to the io_context.
    boost::system::error_code ec(last_error,
        boost::asio::error::get_system_category());
    overlapped.complete(ec, 0);
  }
  else
  {
    // The operation was successfully initiated, so ownership of the
    // OVERLAPPED-derived object has passed to the io_context.
    overlapped.release();
  }
}

class connection
  : public std::enable_shared_from_this<connection>
{
public:
  typedef std::shared_ptr<connection> pointer;

  static pointer create(boost::asio::io_context& io_context,
      const std::string& filename)
  {
    return pointer(new connection(io_context, filename));
  }

  tcp_socket& socket()
  {
    return socket_;
  }

  void start()
  {
    boost::system::error_code ec;
    file_.assign(::CreateFile(filename_.c_str(), GENERIC_READ, 0, 0,
          OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, 0), ec);
    if (file_.is_open())
    {
      transmit_file(socket_, file_,
          std::bind(&connection::handle_write, shared_from_this(),
            boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred));
    }
  }

private:
  connection(boost::asio::io_context& io_context, const std::string& filename)
    : socket_(io_context),
      filename_(filename),
      file_(io_context)
  {
  }

  void handle_write(const boost::system::error_code& /*error*/,
      size_t /*bytes_transferred*/)
  {
    boost::system::error_code ignored_ec;
    socket_.shutdown(tcp_socket::shutdown_both, ignored_ec);
  }

  tcp_socket socket_;
  std::string filename_;
  random_access_handle file_;
};

class server
{
public:
  server(boost::asio::io_context& io_context,
      unsigned short port, const std::string& filename)
    : acceptor_(io_context, tcp::endpoint(tcp::v4(), port)),
      filename_(filename)
  {
    start_accept();
  }

private:
  void start_accept()
  {
    connection::pointer new_connection =
      connection::create(acceptor_.get_executor().context(), filename_);

    acceptor_.async_accept(new_connection->socket(),
        std::bind(&server::handle_accept, this, new_connection,
          boost::asio::placeholders::error));
  }

  void handle_accept(connection::pointer new_connection,
      const boost::system::error_code& error)
  {
    if (!error)
    {
      new_connection->start();
    }

    start_accept();
  }

  tcp_acceptor acceptor_;
  std::string filename_;
};

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 3)
    {
      std::cerr << "Usage: transmit_file <port> <filename>\n";
      return 1;
    }

    boost::asio::io_context io_context;

    using namespace std; // For atoi.
    server s(io_context, atoi(argv[1]), argv[2]);

    io_context.run();
  }
  catch (std::exception& e)
  {
    std::cerr << e.what() << std::endl;
  }

  return 0;
}

#else // defined(BOOST_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)
# error Overlapped I/O not available on this platform
#endif // defined(BOOST_ASIO_HAS_WINDOWS_OVERLAPPED_PTR)
