/**

 * 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/>.

 */

#include <string>

#include <stdexcept>

#include <map>

#include <sys/inotify.h>

#include <string.h>

#include <unistd.h>

#include "FileMonitor.h"

void checkError(bool hasError, const std::string& message) {

	if (hasError) throw std::logic_error(message + strerror(errno));

}

class WatchedFile::Impl {

public:

	int fd;

	int wd;

	std::string fileName;

	uint32_t mask;

	std::shared_ptr<FileMonitor::Impl> fileMonitorImpl;

	virtual ~Impl();

};

WatchedFile::WatchedFile() {

	impl = std::make_shared<Impl>();

}

WatchedFile::~WatchedFile() {

}

class FileMonitor::Impl {

public:

	int fd;

	std::map<int, std::string> fileNames;

	void unwatch(int wd) {

		fileNames.erase(wd);

		int result = inotify_rm_watch(fd, wd);

		checkError(result < 0, "unable to stop monitoring a file: ");

	}

	virtual ~Impl() {

		close(fd);

	}

};

FileMonitor::FileMonitor() : FileMonitor(std::make_shared<Impl>()) {

}

FileMonitor::FileMonitor(std::shared_ptr<Impl> impl) {

	this->impl = impl;

	impl->fd = inotify_init1(IN_NONBLOCK);

	checkError(impl->fd < 0, "unable to initialize FileMonitor: ");

}

FileMonitor::~FileMonitor() {

}

int FileMonitor::getFD() const {

	return impl->fd;

}

WatchedFile FileMonitor::watch(const std::string& fileName) {

	return watch(fileName, IN_CLOSE_WRITE);

}

WatchedFile FileMonitor::watch(const std::string& fileName, uint32_t mask) {

	int wd = inotify_add_watch(impl->fd, fileName.c_str(), mask);

	checkError(wd < 0, "unable to monitor a file: ");

	impl->fileNames[wd] = fileName;

	WatchedFile wf;

	wf.impl->fd = impl->fd;

	wf.impl->wd = wd;

	wf.impl->fileMonitorImpl = impl;

	wf.impl->fileName = fileName;

	wf.impl->mask = mask;

	return wf;

}

bool FileMonitor::readEvent(FileEvent& event) {

	struct inotify_event rawEvent;

	int result = ::read(impl->fd, &rawEvent, sizeof (rawEvent));

	if (result == sizeof (rawEvent)) {

		event.fileName = impl->fileNames[rawEvent.wd];

		event.mask = rawEvent.mask;

		return true;

	} else {

		return false;

	}

}

WatchedFile::Impl::~Impl() {

	try {

		fileMonitorImpl->unwatch(wd);

	} catch (const std::exception& e) {

		// ignored, fails after file deletion

		// std::cerr << "unwatch failed: " << e.what() << std::endl;

	}

}

FileMonitor WatchedFile::getFileMonitor() const {

	return FileMonitor(impl->fileMonitorImpl);

}

std::string WatchedFile::getFileName() const {

	return impl->fileName;

}

uint32_t WatchedFile::getMask() const {

	return impl->mask;

}