cpp-cli/include/cli/message.h

//
//  message.h
//  cli
//
//  Created by Sam Jaffe on 10/10/20.
//  Copyright © 2020 Sam Jaffe. All rights reserved.
//
#pragma once

#include <iostream>
#include <memory>
#include <tuple>

namespace cli { namespace detail {

template <typename T, size_t ...Is>
void print(std::ostream &os, T const & tup, std::index_sequence<Is...>) {
  os << std::boolalpha;
  using swallow = int[];
  (void)swallow{0, ((void)(os << std::get<Is>(tup)), 0)...};
  os << std::noboolalpha;
}

template <typename T> struct up_string { using type = std::remove_reference_t<T>; };
template <size_t N> struct up_string<char const(&)[N]> {
  using type = std::string;
};

template <typename T> using up_string_t = typename up_string<T>::type;

}}

namespace cli {

struct message {
  virtual ~message() = default;
  virtual void print(std::ostream &) const = 0;
};


template <typename ...T>
struct message_impl : public message {
  std::tuple<T...> tuple;
  message_impl(std::tuple<T...> &&tuple) : tuple(std::move(tuple)) {}
  void print(std::ostream &os) const override {
    detail::print(os, tuple, std::make_index_sequence<sizeof...(T)>{});
  }
};

template <typename ...Args>
auto make_message(Args &&...args) {
  using detail::up_string_t;
  using message_t = message_impl<up_string_t<Args>...>;
  auto tuple = std::make_tuple(std::forward<up_string_t<Args>>(args)...);
  return std::make_shared<message_t>(std::move(tuple));
}

}