// =====================================================================================================================
//	glw, an open-source library that wraps OpenGL structures into classes.
//	Copyright (C) 2024  Medusa Slockbower
//
//	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, either version 3 of the License, or
//	(at your option) any later version.
//
//	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 <https://www.gnu.org/licenses/>.
// =====================================================================================================================

#ifndef GLW_TIMER_H
#define GLW_TIMER_H

#include <cassert>
#include "common.h"

namespace glw
{

class timer
{
private:
	enum
	{
		begin = 0
	,	end   = 1
	};
	
public:
	timer() : handles_{ 0 }, running_(false) { glCreateQueries(GL_TIMESTAMP, 2, handles_); }
	timer(const timer&) = delete;
	timer(timer&&) = default;
	~timer() { glDeleteQueries(2, handles_); }

	void    start() { assert(not running_); glQueryCounter(handles_[begin], GL_TIMESTAMP); running_ = true;  }
	void    stop()  { assert(running_);     glQueryCounter(handles_[end],   GL_TIMESTAMP); running_ = false; }
	int64_t poll()
	{
		assert(not running_);
		int32_t available = false;
		while(not available) glGetQueryObjectiv(handles_[end], GL_QUERY_RESULT_AVAILABLE, &available);
		int64_t start; glGetQueryObjecti64v(handles_[begin], GL_QUERY_RESULT, &start);
		int64_t stop;  glGetQueryObjecti64v(handles_[end],   GL_QUERY_RESULT, &stop);
		return stop - start;
	}

private:
	handle_t handles_[2];
	bool	 running_;
};
	
}

#endif //TIMER_H