Volume.h

/***************************************************************************
 *   Copyright (C) 2019-2021 by Stefan Kebekus                             *
 *   stefan.kebekus@gmail.com                                              *
 *                                                                         *
 *   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, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
 
#pragma once
 
#include <QObject>
#include <QQmlEngine>
#include <QtMath>
 
 
namespace Units {

    class Volume {
        Q_GADGET
        QML_VALUE_TYPE(volume)
 
    public:
        static constexpr auto fromL(double volumeInL) -> Volume
        {
            Volume result;
            result.m_volumeInL = volumeInL;
            return result;
        }

        static constexpr auto fromGAL(double volumeInGAL) -> Volume
        {
            Volume result;
            result.m_volumeInL = LitersPerGallon*volumeInGAL;
            return result;
        }

        [[nodiscard]] Q_INVOKABLE bool isFinite() const
        {
            return std::isfinite(m_volumeInL);
        }

        Q_INVOKABLE Units::Volume& operator+=(Units::Volume other)
        {
            m_volumeInL += other.m_volumeInL;
            return *this;
        }

        [[nodiscard]] Q_INVOKABLE std::partial_ordering operator<=>(const Units::Volume& rhs) const = default;

        [[nodiscard]] Q_INVOKABLE double toL() const
        {
            return m_volumeInL;
        }

        [[nodiscard]] Q_INVOKABLE double toGAL() const
        {
            return m_volumeInL/LitersPerGallon;
        }
 
    private:
        static constexpr double LitersPerGallon = 4.54609;
 
        // Speed in meters per second
        double m_volumeInL{ NAN };
    };
} // namespace Units
 
 
// Declare meta types
Q_DECLARE_METATYPE(Units::Volume)