/**
 * 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;
}