// Copyright 2025, Luís Murta
// SPDX-License-Identifier: MIT

#pragma once

#include <any>
#include <boost/asio.hpp>
#include <concepts>
// #include <expected>
#include <functional>
#include <optional>
#include <ostream>
#include <tuple>
#include <utility>

namespace freepipe {

template <typename... Args> struct Task {
  explicit constexpr Task(std::shared_ptr<boost::asio::io_context> ioc, Args &&...args)
    requires(sizeof...(Args) > 0)
      : ioc_(std::move(ioc)), args_(std::forward<Args>(args)...) {}

  explicit constexpr Task(std::shared_ptr<boost::asio::io_context> ioc)
    requires(sizeof...(Args) == 0)
      : ioc_(std::move(ioc)) {}

  constexpr auto const &operator*() const & { return args_; }
  constexpr auto &operator*() & { return args_; }
  constexpr auto &&operator*() && { return std::move(args_); }
  constexpr auto const &&operator*() const && { return std::move(args_); }

  std::shared_ptr<boost::asio::io_context> ioc_;

private:
  std::tuple<Args...> args_;
};

template <typename... Args, std::regular_invocable<Args...> F>
constexpr auto operator|(Task<Args...> const &task, F &&func) {
  using R = std::invoke_result_t<F, Args...>;

  if constexpr (std::is_void_v<R>) {
    std::apply(std::forward<F>(func), *task);
    return boost::asio::post(task.ioc_, Task<>{task.ioc_});
  } else {
    return Task<R>{task.ioc_, std::apply(std::forward<F>(func), *task)};
  }
}

template <typename... Args, std::regular_invocable<Args...> F>
constexpr auto operator|(Task<Args...> &&task, F &&func) {
  using R = std::invoke_result_t<F, Args...>;

  if constexpr (std::is_void_v<R>) {
    boost::asio::post(*task.ioc_, [&] { std::apply(std::forward<F>(func), std::move(*task)); });
    return Task<>{task.ioc_};
  } else {
    return Task<R>{task.ioc_, std::apply(std::forward<F>(func), std::move(*task))};
  }
}

template <typename... Args, std::regular_invocable<Args...>... F>
constexpr auto operator|(Task<Args...> const &task, std::tuple<F...> &&func) {
  std::tuple<std::invoke_result_t<F, Args...>...> ret;

  auto l = [&](auto &&f) {
    using R = std::invoke_result_t<decltype(f), Args...>;

    if constexpr (std::is_void_v<R>) {
      std::apply(std::forward<decltype(f)>(f), *task);
      return;
    } else {
      return std::apply(std::forward<decltype(f)>(f), *task);
    }
  };

  std::apply(l, func);

  return std::make_from_tuple<Task>(std::apply(
      [&]<std::size_t... Is>(F &&...f) {
        return Task<std::invoke_result_t<F, Args...>...>(
            l(std::forward<F>(f), std::index_sequence<Is...>{})...);
      },
      std::move(func)));

  // (
  //     [&] {
  //       using R = std::invoke_result_t<F, Args...>;

  //       if constexpr (std::is_void_v<R>) {
  //         std::apply(std::forward<F>(func), *task);
  //       } else {
  //         std::get<R>(ret) = std::apply(std::forward<F>(func), *task);
  //       }
  //     }(),
  //     ...);

  // auto ans = std::apply(
  //     [](auto &&f) {
  //       return Task(
  //           if constexpr (std::is_void_v<decltype(f)>) { return Task<>{}; } else {
  //             return Task<decltype(f)>{f};
  //           },
  //           f...);
  //     },
  //     std::move(func));

  // return std::make_from_tuple<Task>(std::move(ret));
}

template <typename... Args, std::regular_invocable<Args...>... F>
constexpr auto operator|(Task<Args...> &&task, std::tuple<F...> &&func) {
  std::tuple<std::invoke_result_t<F, Args...>...> ret;

  (
      [&] {
        using R = std::invoke_result_t<F, Args...>;

        if constexpr (std::is_void_v<R>) {
          std::apply(std::forward<F>(func), *std::move(task));
        } else {
          std::get<R>(ret) = std::apply(std::forward<F>(func), *std::move(task));
        }
      }(),
      ...);

  return std::make_from_tuple<Task>(std::move(ret));
}

template <typename... Args, typename CharT, typename Traits = std::char_traits<CharT>>
constexpr auto operator|(Task<Args...> const &task, std::basic_ostream<CharT, Traits> &os) {
  std::apply([&os](auto &&...args) { ((os << args << '\n'), ...); }, *task);
  return Task<>{task.ioc_};
}

template <typename... Args, typename CharT, typename Traits = std::char_traits<CharT>>
constexpr auto operator|(Task<Args...> &&task, std::basic_ostream<CharT, Traits> &os) {
  std::apply([&os](auto &&...args) { ((os << args << '\n'), ...); }, std::move(*task));
  return Task<>{task.ioc_};
}

class Pipe : public Task<> {
  // std::shared_ptr<boost::asio::io_context> io_context_;

public:
  Pipe() : Task<>(std::make_shared<boost::asio::io_context>()) {}

  explicit Pipe(std::shared_ptr<boost::asio::io_context> io_context) : Task<>{io_context} {}
};

} // namespace freepipe