File indexing completed on 2024-12-08 09:38:10

 /*
     This file is part of the kholidays library.
 
     SPDX-FileCopyrightText: 2004, 2007, 2009 Allen Winter <winter@kde.org>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
 #include "lunarphase.h"
 
 #include <QCoreApplication>
 #include <QDateTime>
 
 using namespace KHolidays;
 
 QString LunarPhase::phaseNameAtDate(const QDate &date)
 {
     return phaseName(phaseAtDate(date));
 }
 
 QString LunarPhase::phaseName(LunarPhase::Phase phase)
 {
     switch (phase) {
     case NewMoon:
         return (QCoreApplication::translate("LunarPhase", "New Moon"));
     case FullMoon:
         return (QCoreApplication::translate("LunarPhase", "Full Moon"));
     case FirstQuarter:
         return (QCoreApplication::translate("LunarPhase", "First Quarter Moon"));
     case LastQuarter:
         return (QCoreApplication::translate("LunarPhase", "Last Quarter Moon"));
     case None:
         return QString();
     case WaxingCrescent:
         return (QCoreApplication::translate("LunarPhase", "Waxing Crescent"));
     case WaxingGibbous:
         return (QCoreApplication::translate("LunarPhase", "Waxing Gibbous"));
     case WaningGibbous:
         return (QCoreApplication::translate("LunarPhase", "Waning Gibbous"));
     case WaningCrescent:
         return (QCoreApplication::translate("LunarPhase", "Waning Crescent"));
     }
     return QString();
 }
 
 static double phaseAngle(int64_t unixmsec);
 
 LunarPhase::Phase LunarPhase::phaseAtDate(const QDate &date)
 {
     Phase retPhase = None;
 
     const QTime midnight(0, 0, 0);
     const QDateTime todayStart(date, midnight, Qt::UTC);
     const double startAngle = phaseAngle(todayStart.toMSecsSinceEpoch());
     const QDateTime todayEnd(date.addDays(1), midnight, Qt::UTC);
     const double endAngle = phaseAngle(todayEnd.toMSecsSinceEpoch());
 
     if (startAngle > endAngle) {
         retPhase = NewMoon;
     } else if (startAngle < 90.0 && endAngle > 90.0) {
         retPhase = FirstQuarter;
     } else if (startAngle < 180.0 && endAngle > 180.0) {
         retPhase = FullMoon;
     } else if (startAngle < 270.0 && endAngle > 270.0) {
         retPhase = LastQuarter;
     } else if (endAngle < 90.0) {
         retPhase = WaxingCrescent;
     } else if (endAngle < 180.0) {
         retPhase = WaxingGibbous;
     } else if (endAngle < 270.0) {
         retPhase = WaningGibbous;
     } else if (endAngle < 360.0) {
         retPhase = WaningCrescent;
     }
 
     return retPhase;
 }
 
 /*
     Algorithm adapted from Moontool by John Walker.
     Moontool is in the public domain: "Do what thou wilt shall be the whole of the law".
     Unnecessary calculations have been removed.
     See https://fourmilab.ch/moontool .
 */
 
 #include <cmath>
 
 constexpr int64_t epoch = 315446400000; // "1980 January 0.0", a.k.a. midnight on 1979-12-31, in ms Unix time
 constexpr double elonge = 278.833540; // ecliptic longitude of sun at epoch
 constexpr double elongp = 282.596403; // ecliptic longitude of sun at perigee
 constexpr double earthEcc = 0.016718; // eccentricity of earth orbit
 static const double ecPrefactor = sqrt((1 + earthEcc) / (1 - earthEcc));
 
 constexpr double mmlong = 64.975464; // mean longitude of moon at epoch
 constexpr double mmlongp = 349.383063; // mean longitude of moon at perigee
 
 constexpr double PI = 3.14159265358979323846;
 
 static double fixAngle(double degrees)
 {
     return degrees - floor(degrees / 360.0) * 360.0;
 }
 
 static constexpr double radToDeg(double rad)
 {
     return rad / PI * 180.0;
 }
 
 static constexpr double degToRad(double deg)
 {
     return deg / 180.0 * PI;
 }
 
 constexpr double epsilon = 1e-6;
 
 static double kepler(double m, double ecc)
 {
     double mrad = degToRad(m);
     double e = mrad;
     double delta;
     do {
         delta = e - ecc * sin(e) - mrad;
         e -= delta / (1 - ecc * cos(e));
     } while (abs(delta) > epsilon);
     return e;
 }
 
 static double phaseAngle(int64_t unixmsec)
 {
     int64_t msec = unixmsec - epoch;
 
     double sunMeanAnomaly = fixAngle(msec * (360.0 / 365.2422 / 86400000.0) + elonge - elongp);
     double trueAnomaly = 2 * radToDeg(atan(ecPrefactor * tan(kepler(sunMeanAnomaly, earthEcc) / 2)));
     double geocentricEclipticLong = fixAngle(trueAnomaly + elongp);
 
     double moonMeanLong = fixAngle(msec * (13.1763966 / 86400000.0) + mmlong);
     double moonMeanAnomaly = fixAngle(moonMeanLong - msec * (0.1114041 / 86400000.0) - mmlongp);
     double evection = 1.2739 * sin(degToRad(2 * (moonMeanLong - geocentricEclipticLong) - moonMeanAnomaly));
     double annualEquation = 0.1858 * sin(degToRad(sunMeanAnomaly));
     double a3 = 0.37 * sin(degToRad(sunMeanAnomaly));
     double correctedAnomaly = moonMeanAnomaly + evection - annualEquation - a3;
     double centreCorrection = 6.2886 * sin(degToRad(correctedAnomaly));
     double a4 = 0.214 * sin(degToRad(2 * correctedAnomaly));
     double correctedLong = moonMeanLong + evection + centreCorrection - annualEquation + a4;
     double variation = 0.6583 * sin(degToRad(2 * (correctedLong - geocentricEclipticLong)));
     double trueLong = correctedLong + variation;
 
     return fixAngle(trueLong - geocentricEclipticLong);
 }
 
 #include "moc_lunarphase.cpp"