/*
	This file is part of Fennix Kernel.

	Fennix Kernel is free software: you can redistribute it and/or
	modify it under the terms of the GNU General Public License as
	published by the Free Software Foundation, either version 3 of
	the License, or (at your option) any later version.

	Fennix Kernel is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
*/

#pragma once

#include <atomic>
#include <chrono>
#include <exception>
#include <mutex>
#include <thread>
#include <type_traits>
#include <system_error>
#include <utility>
#include <cstdint>
#include <memory>

namespace std
{
	enum class future_errc
	{
		broken_promise = 0,
		future_already_retrieved = 1,
		promise_already_satisfied = 2,
		no_state = 3
	};

	enum class launch : std::uint_least8_t
	{
		async = 0,
		deferred = 1,
	};

	enum class future_status
	{
		ready,
		timeout,
		deferred
	};

	template <>
	struct is_error_code_enum<future_errc> : public true_type
	{
	};
	error_condition make_error_condition(future_errc e) noexcept;

	const error_category &future_category() noexcept
	{
		static const error_category cat;
		return cat;
	}

	inline std::error_code make_error_code(future_errc e) noexcept
	{
		return std::error_code(static_cast<int>(e), future_category());
	}

	class future_error;

	template <class R>
	class promise;
	template <class R>
	class promise<R &>;
	template <>
	class promise<void>;

	template <class R>
	void swap(promise<R> &x, promise<R> &y) noexcept;

	template <class R, class Alloc>
	struct uses_allocator<promise<R>, Alloc>;

	template <class R>
	class future;
	template <class R>
	class future<R &>;
	template <>
	class future<void>;

	template <class R>
	class shared_future;
	template <class R>
	class shared_future<R &>;
	template <>
	class shared_future<void>;

	template <class>
	class packaged_task; // not defined

	template <class R, class... ArgTypes>
	class packaged_task<R(ArgTypes...)>;

	template <class R, class... ArgTypes>
	void swap(packaged_task<R(ArgTypes...)> &, packaged_task<R(ArgTypes...)> &) noexcept;

	template <class Fn, class... Args>
	future<typename result_of<Fn(Args...)>::type> async(launch policy, Fn &&fn, Args &&...args)
	{
		using ReturnType = std::invoke_result_t<std::decay_t<Fn>, std::decay_t<Args>...>;

		if (policy == std::launch::async)
		{
			auto task = std::make_shared<std::packaged_task<ReturnType()>>(
				std::bind(std::forward<Fn>(fn), std::forward<Args>(args)...));

			std::future<ReturnType> future = task->get_future();
			std::thread([task]()
						{ (*task)(); })
				.detach();

			return future;
		}
		else if (policy == std::launch::deferred)
		{
			return std::async(std::launch::deferred, std::forward<Fn>(fn), std::forward<Args>(args)...);
		}
		else
		{
			throw std::invalid_argument("Invalid launch policy");
		}
	}

	template <class Fn, class... Args>
	future<typename result_of<Fn(Args...)>::type> async(Fn &&fn, Args &&...args)
	{
		return async(std::launch::async /* | std::launch::deferred*/, std::forward<Fn>(fn), std::forward<Args>(args)...);
	}

	class future_error : public logic_error
	{
	private:
		error_code ec_;

	public:
		future_error(const future_error &other) noexcept;
		explicit future_error(std::future_errc ec);
		future_error &operator=(const future_error &other) noexcept;
		const std::error_code &code() const noexcept;
		virtual const char *what() const noexcept;
	};

	template <class R>
	class promise
	{
	public:
		promise();
		template <class Allocator>
		promise(allocator_arg_t, const Allocator &a);
		promise(promise &&rhs) noexcept;
		promise(const promise &) = delete;
		~promise();

		promise &operator=(promise &&rhs) noexcept;
		promise &operator=(const promise &) = delete;
		void swap(promise &other) noexcept;

		future<R> get_future();

		void set_value(const R &value);
		void set_value(R &&value);
		void set_value(R &value);
		void set_value();

		void set_exception(exception_ptr p);

		void set_value_at_thread_exit(/* see description */);
		void set_exception_at_thread_exit(exception_ptr p);
	};

	template <class R>
	void swap(promise<R> &x, promise<R> &y) noexcept;

	template <class R, class Alloc>
	struct uses_allocator<promise<R>, Alloc>;

	template <class R>
	class future
	{
	public:
		future() noexcept;
		future(future &&) noexcept;
		future(const future &) = delete;
		~future();
		future &operator=(const future &) = delete;
		future &operator=(future &&) noexcept;
		shared_future<R> share() noexcept;

		R get();
		// R &get();
		// void get();

		bool valid() const noexcept;

		void wait() const;
		template <class Rep, class Period>
		future_status wait_for(const chrono::duration<Rep, Period> &rel_time) const;
		template <class Clock, class Duration>
		future_status wait_until(const chrono::time_point<Clock, Duration> &abs_time) const;
	};

	template <class R>
	class shared_future
	{
	public:
		shared_future() noexcept;
		shared_future(const shared_future &rhs) noexcept;
		shared_future(future<R> &&) noexcept;
		shared_future(shared_future &&rhs) noexcept;
		~shared_future();
		shared_future &operator=(const shared_future &rhs) noexcept;
		shared_future &operator=(shared_future &&rhs) noexcept;

		const R &get() const;
		// R &get() const;
		// void get() const;

		bool valid() const noexcept;

		void wait() const;
		template <class Rep, class Period>
		future_status wait_for(const chrono::duration<Rep, Period> &rel_time) const;
		template <class Clock, class Duration>
		future_status wait_until(const chrono::time_point<Clock, Duration> &abs_time) const;
	};

	template <class>
	class packaged_task;

	template <class R, class... ArgTypes>
	class packaged_task<R(ArgTypes...)>
	{
	public:
		packaged_task() noexcept;
		template <class F>
		explicit packaged_task(F &&f);
		~packaged_task();

		packaged_task(const packaged_task &) = delete;
		packaged_task &operator=(const packaged_task &) = delete;

		packaged_task(packaged_task &&rhs) noexcept;
		packaged_task &operator=(packaged_task &&rhs) noexcept;
		void swap(packaged_task &other) noexcept;

		bool valid() const noexcept;

		future<R> get_future();

		void operator()(ArgTypes...);
		void make_ready_at_thread_exit(ArgTypes...);

		void reset();
	};

	template <class R, class... ArgTypes>
	packaged_task(R (*)(ArgTypes...)) -> packaged_task<R(ArgTypes...)>;

	// template <class F>
	// packaged_task(F) -> packaged_task<???>;

	template <class R, class... ArgTypes>
	void swap(packaged_task<R(ArgTypes...)> &x, packaged_task<R(ArgTypes...)> &y) noexcept;
}