// This file is originally from Trantor - KQueue.cc

// Copyright (c) 2016-2021, Tao An.  All rights reserved.

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//   * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//   * Neither the name of Tao An nor the names of other contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


#include "kqueue.h"

#include "core/loops/channel.h"
#ifdef USE_KQUEUE
#include "core/log/logger.h"
#include <poll.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#endif

namespace trantor {
#ifdef USE_KQUEUE
namespace {
const int kNew = -1;
const int kAdded = 1;
const int kDeleted = 2;
} // namespace

KQueue::KQueue(EventLoop *loop) :
		Poller(loop), kqfd_(kqueue()), events_(kInitEventListSize) {
	assert(kqfd_ >= 0);
}

KQueue::~KQueue() {
	close(kqfd_);
}

void KQueue::resetAfterFork() {
	close(kqfd_);
	kqfd_ = kqueue();
	for (auto &ch : channels_) {
		ch.second.first = 0;
		if (ch.second.second->isReading() || ch.second.second->isWriting()) {
			update(ch.second.second);
		}
	}
}

void KQueue::poll(int timeoutMs, ChannelList *activeChannels) {
	struct timespec timeout;
	timeout.tv_sec = timeoutMs / 1000;
	timeout.tv_nsec = (timeoutMs % 1000) * 1000000;

	int numEvents = kevent(kqfd_,
			NULL,
			0,
			events_.data(),
			static_cast<int>(events_.size()),
			&timeout);
	int savedErrno = errno;
	// Timestamp now(Timestamp::now());
	if (numEvents > 0) {
		// LOG_TRACE << numEvents << " events happended";
		fillActiveChannels(numEvents, activeChannels);
		if (static_cast<size_t>(numEvents) == events_.size()) {
			events_.resize(events_.size() * 2);
		}
	} else if (numEvents == 0) {
		// std::cout << "nothing happended" << std::endl;
	} else {
		// error happens, log uncommon ones
		if (savedErrno != EINTR) {
			errno = savedErrno;
			LOG_SYSERR << "KQueue::poll()";
		}
	}
	return;
}

void KQueue::fillActiveChannels(int numEvents,
		ChannelList *activeChannels) const {
	assert(static_cast<size_t>(numEvents) <= events_.size());
	for (int i = 0; i < numEvents; ++i) {
		Channel *channel = static_cast<Channel *>(events_[i].udata);
		assert(channels_.find(channel->fd()) != channels_.end());
		int events = events_[i].filter;
		if (events == EVFILT_READ) {
			channel->setRevents(POLLIN);
		} else if (events == EVFILT_WRITE) {
			channel->setRevents(POLLOUT);
		} else {
			LOG_ERROR << "events=" << events;
			continue;
		}
		activeChannels->push_back(channel);
	}
}

void KQueue::updateChannel(Channel *channel) {
	assertInLoopThread();
	const int index = channel->index();
	// LOG_TRACE << "fd = " << channel->fd()
	//           << " events = " << channel->events() << " index = " << index;
	if (index == kNew || index == kDeleted) {
		if (index == kNew) {
			assert(channels_.find(channel->fd()) == channels_.end());
		} else { // index == kDeleted
			assert(channels_.find(channel->fd()) != channels_.end());
			assert(channels_[channel->fd()].second == channel);
		}
		update(channel);
		channel->setIndex(kAdded);
	} else {
		// update existing one
		int fd = channel->fd();
		(void)fd;
		assert(channels_.find(fd) != channels_.end());
		assert(index == kAdded);
		if (channel->isNoneEvent()) {
			update(channel);
			channel->setIndex(kDeleted);
		} else {
			update(channel);
		}
	}
}
void KQueue::removeChannel(Channel *channel) {
	assertInLoopThread();
	int fd = channel->fd();
	assert(channels_.find(fd) != channels_.end());
	assert(channel->isNoneEvent());
	int index = channel->index();
	assert(index == kAdded || index == kDeleted);

	if (index == kAdded) {
		update(channel);
	}

	size_t n = channels_.erase(fd);
	(void)n;
	assert(n == 1);
	channel->setIndex(kNew);
}

void KQueue::update(Channel *channel) {
	struct kevent ev[2];
	int n = 0;
	auto events = channel->events();
	int oldEvents = 0;
	if (channels_.find(channel->fd()) != channels_.end()) {
		oldEvents = channels_[channel->fd()].first;
	}

	auto fd = channel->fd();
	channels_[fd] = { events, channel };

	if ((events & Channel::kReadEvent) && (!(oldEvents & Channel::kReadEvent))) {
		EV_SET(&ev[n++],
				fd,
				EVFILT_READ,
				EV_ADD | EV_ENABLE,
				0,
				0,
				(void *)(intptr_t)channel);
	} else if ((!(events & Channel::kReadEvent)) &&
			   (oldEvents & Channel::kReadEvent)) {
		EV_SET(&ev[n++],
				fd,
				EVFILT_READ,
				EV_DELETE,
				0,
				0,
				(void *)(intptr_t)channel);
	}
	if ((events & Channel::kWriteEvent) &&
			(!(oldEvents & Channel::kWriteEvent))) {
		EV_SET(&ev[n++],
				fd,
				EVFILT_WRITE,
				EV_ADD | EV_ENABLE,
				0,
				0,
				(void *)(intptr_t)channel);
	} else if ((!(events & Channel::kWriteEvent)) &&
			   (oldEvents & Channel::kWriteEvent)) {
		EV_SET(&ev[n++],
				fd,
				EVFILT_WRITE,
				EV_DELETE,
				0,
				0,
				(void *)(intptr_t)channel);
	}
	kevent(kqfd_, ev, n, NULL, 0, NULL);
}
#else
KQueue::KQueue(EventLoop *loop) :
		Poller(loop) {
	assert(false);
}
KQueue::~KQueue() {
}
void KQueue::poll(int, ChannelList *) {
}
void KQueue::updateChannel(Channel *) {
}
void KQueue::removeChannel(Channel *) {
}
void KQueue::resetAfterFork() {
}
#endif
} // namespace trantor