// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.

#pragma once
#define HAVE_IRCD_CTX_CONDITION_VARIABLE_H

namespace ircd::ctx
{
	struct condition_variable;
}

class ircd::ctx::condition_variable
{
	list q;

  public:
	bool empty() const;
	size_t size() const;
	bool waiting(const ctx &) const noexcept;

	template<class lock, class time_point, class predicate> bool wait_until(lock &, time_point&&, predicate&&);
	template<class lock, class time_point> std::cv_status wait_until(lock &, time_point&&);

	template<class lock, class duration, class predicate> bool wait_for(lock &, const duration &, predicate&&);
	template<class lock, class duration> std::cv_status wait_for(lock &, const duration &);

	template<class lock, class predicate> void wait(lock &, predicate&&);
	template<class lock> void wait(lock &);

	void terminate_all() noexcept;
	void interrupt_all() noexcept;
	void notify_all() noexcept;
	void notify_one() noexcept;
	void notify() noexcept;
};

template<class lock>
void
ircd::ctx::condition_variable::wait(lock &l)
{
	assert(current);
	const unwind_exceptional renotify{[this]
	{
		notify_one();
	}};

	const unwind remove{[this]
	{
		q.remove(current);
	}};

	q.push_back(current);
	const unlock_guard<lock> ul{l};
	ircd::ctx::wait();
}

template<class lock,
         class predicate>
void
ircd::ctx::condition_variable::wait(lock &l,
                                    predicate&& pred)
{
	if(pred())
		return;

	assert(current);
	const unwind_exceptional renotify{[this]
	{
		notify_one();
	}};

	const unwind remove{[this]
	{
		q.remove(current);
	}};

	q.push_back(current); do
	{
		const unlock_guard<lock> ul{l};
		ircd::ctx::wait();
	}
	while(!pred());
}

/// Returns true if notified; false if timed out
template<class lock,
         class duration>
std::cv_status
ircd::ctx::condition_variable::wait_for(lock &l,
                                        const duration &dur)
{
	static const duration zero(0);

	assert(current);
	const unwind_exceptional renotify{[this]
	{
		notify_one();
	}};

	const unwind remove{[this]
	{
		q.remove(current);
	}};

	q.push_back(current);
	const unlock_guard<lock> ul{l};
	return ircd::ctx::wait<std::nothrow_t>(dur) > zero?
		std::cv_status::no_timeout:
		std::cv_status::timeout;
}

/// Returns true if predicate passed; false if timed out
template<class lock,
         class duration,
         class predicate>
bool
ircd::ctx::condition_variable::wait_for(lock &l,
                                        const duration &dur,
                                        predicate&& pred)
{
	static const duration zero(0);

	if(pred())
		return true;

	assert(current);
	const unwind_exceptional renotify{[this]
	{
		notify_one();
	}};

	const unwind remove{[this]
	{
		q.remove(current);
	}};

	q.push_back(current); do
	{
		bool expired;
		{
			const unlock_guard<lock> ul{l};
			expired = ircd::ctx::wait<std::nothrow_t>(dur) <= zero;
		}

		if(pred())
			return true;

		if(expired)
			return false;
	}
	while(1);
}

/// Returns true if notified; false if timed out
template<class lock,
         class time_point>
std::cv_status
ircd::ctx::condition_variable::wait_until(lock &l,
                                          time_point&& tp)
{
	assert(current);
	const unwind_exceptional renotify{[this]
	{
		notify_one();
	}};

	const unwind remove{[this]
	{
		q.remove(current);
	}};

	q.push_back(current);
	const unlock_guard<lock> ul{l};
	return ircd::ctx::wait_until<std::nothrow_t>(tp)?
		std::cv_status::timeout:
		std::cv_status::no_timeout;
}

/// Returns true if predicate passed; false if timed out
template<class lock,
         class time_point,
         class predicate>
bool
ircd::ctx::condition_variable::wait_until(lock &l,
                                          time_point&& tp,
                                          predicate&& pred)
{
	if(pred())
		return true;

	assert(current);
	const unwind_exceptional renotify{[this]
	{
		notify_one();
	}};

	const unwind remove{[this]
	{
		q.remove(current);
	}};

	q.push_back(current); do
	{
		bool expired;
		{
			const unlock_guard<lock> ul{l};
			expired = ircd::ctx::wait_until<std::nothrow_t>(tp);
		}

		if(pred())
			return true;

		if(expired)
			return false;
	}
	while(1);
}

/// The number of contexts waiting in the queue.
inline size_t
ircd::ctx::condition_variable::size()
const
{
	return q.size();
}

/// The number of contexts waiting in the queue.
inline bool
ircd::ctx::condition_variable::empty()
const
{
	return q.empty();
}