Celestia

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// units.cpp
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//
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// Copyright (C) 2001-2023, the Celestia Development Team
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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#include "units.h"
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#include <celcompat/numbers.h>
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#include "astro.h"
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#include "date.h"
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namespace celestia::astro
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{
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// Get scale of given length unit in kilometers
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std::optional<double>
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getLengthScale(LengthUnit unit)
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{
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    switch (unit)
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    {
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    case LengthUnit::Kilometer: return 1.0;
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    case LengthUnit::Meter: return 1e-3;
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    case LengthUnit::EarthRadius: return EARTH_RADIUS<double>;
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    case LengthUnit::JupiterRadius: return JUPITER_RADIUS<double>;
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    case LengthUnit::SolarRadius: return SOLAR_RADIUS<double>;
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    case LengthUnit::AstronomicalUnit: return KM_PER_AU<double>;
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    case LengthUnit::LightYear: return KM_PER_LY<double>;
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    case LengthUnit::Parsec: return KM_PER_PARSEC<double>;
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    case LengthUnit::Kiloparsec: return 1e3 * KM_PER_PARSEC<double>;
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    case LengthUnit::Megaparsec: return 1e6 * KM_PER_PARSEC<double>;
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    default: return std::nullopt;
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    }
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}
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// Get scale of given time unit in days
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std::optional<double>
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getTimeScale(TimeUnit unit)
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{
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    switch (unit)
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    {
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    case TimeUnit::Second: return 1.0 / SECONDS_PER_DAY;
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    case TimeUnit::Minute: return 1.0 / MINUTES_PER_DAY;
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    case TimeUnit::Hour: return 1.0 / HOURS_PER_DAY;
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    case TimeUnit::Day: return 1.0;
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    case TimeUnit::JulianYear: return DAYS_PER_YEAR;
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    default: return std::nullopt;
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    }
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}
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// Get scale of given angle unit in degrees
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std::optional<double>
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getAngleScale(AngleUnit unit)
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{
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    switch (unit)
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    {
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    case AngleUnit::Milliarcsecond: return 1e-3 / SECONDS_PER_DEG;
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    case AngleUnit::Arcsecond: return 1.0 / SECONDS_PER_DEG;
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    case AngleUnit::Arcminute: return 1.0 / MINUTES_PER_DEG;
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    case AngleUnit::Degree: return 1.0;
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    case AngleUnit::Hour: return DEG_PER_HRA;
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    case AngleUnit::Radian: return 180.0 / celestia::numbers::pi;
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    default: return std::nullopt;
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    }
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}
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std::optional<double>
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getMassScale(MassUnit unit)
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{
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    switch (unit)
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    {
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    case MassUnit::Kilogram: return 1.0 / EarthMass;
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    case MassUnit::EarthMass: return 1.0;
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    case MassUnit::JupiterMass: return JupiterMass / EarthMass;
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    default: return std::nullopt;
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    }
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}
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} // end namespace celestia::astro
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