/**

 * ShaderShark

 * Copyright © 2023 František Kučera (Frantovo.cz, GlobalCode.info)

 *

 * This program 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, version 3 of the License.

 *

 * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.

 */

#pragma once

#include <stdexcept>

#include <string>

#include <signal.h>

#include <sys/signalfd.h>

#include <sys/epoll.h>

#include <unistd.h>

#include <sys/fcntl.h>

#include <sys/socket.h>

#include <sys/un.h>

#include <stdexcept>

#include <string>

class EPoll {

private:

	int epollEventCount;

	epoll_event* epollEvents;

	int epollFD;

	void static log(const std::string& message) {

		std::cout << message << std::endl;

	}

public:

	class Exception : public std::logic_error {

	public:

		Exception(const std::string& msg) : logic_error(msg) {

		}

		Exception(const std::string& msg, int errNo) :

				logic_error(msg + strerror(errNo)) {

		}

	};

	EPoll(int eventCount = 5) : epollEventCount(eventCount) {

		epollEvents = (epoll_event*) malloc(sizeof (*epollEvents) * eventCount);

		epollFD = epoll_create1(0);

		log("EPoll(): epoll_create() = " + std::to_string(epollFD));

	}

	virtual ~EPoll() {

		::close(epollFD);

		free(epollEvents);

	}

	EPoll(const EPoll&) = delete;

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

	static void processSignal(int signal) {

		log("got signal: " + std::to_string(signal));

	}

	int addSignals() {

		::signal(SIGTERM, EPoll::processSignal);

		::signal(SIGINT, EPoll::processSignal);

		sigset_t mask;

		::sigemptyset(&mask);

		::sigaddset(&mask, SIGTERM);

		::sigaddset(&mask, SIGINT);

		int signalFD = ::signalfd(-1, &mask, 0);

		add(signalFD, EPOLLIN | EPOLLET | EPOLLHUP);

		log("signalFD=" + std::to_string(signalFD));

		return signalFD;

	}

	void add(int fd, uint32_t events = EPOLL_EVENTS::EPOLLIN) {

		struct epoll_event ev;

		ev.data.fd = fd;

		ev.events = events;

		int err = epoll_ctl(epollFD, EPOLL_CTL_ADD, ev.data.fd, &ev);

		if (err) throw Exception("EPoll::add() failed (a file?):", errno);

		// Regular files can not be monitored this way, thus:

		//   cat Makefile | opengl-pdf      # works

		//   opengl-pdf < Makefile          # does not work

	}

	void del(int fd) {

		int err = epoll_ctl(epollFD, EPOLL_CTL_DEL, fd, nullptr);

		if (err) throw Exception("EPoll::del() failed: ", errno);

	}

	int wait(int timeout = 1000) {

		int count = epoll_wait(epollFD, epollEvents, epollEventCount, timeout);

		if (count >= 0) return count;

		else throw Exception("EPoll::wait() failed: ", errno);

	}

	const epoll_event& operator[](std::size_t index) const {

		if (index < epollEventCount) return epollEvents[index];

		else throw std::out_of_range("invalid index of epollEvents");

	}

};