/// <summary>
/// Calculate time for midnight.
/// </summary>
private static double ComputeMidnightTime(Midnight method, double fajr, double sunrise, double sunset)
{
var duration = method == Midnight.Jafari ? DateTimeMath.ComputeDuration(fajr, sunset) : DateTimeMath.ComputeDuration(sunrise, sunset);
var midnightTime = sunset + (duration / 2.0);
return(midnightTime);
}
/// <summary>
/// Adjust calculated imsak, fajr, maghrib and isha prayer times to high latitude adjustment.
/// </summary>
private static PrayersInDouble AdjustAllForHighLatitude(PrayersInDouble raw, PrayerCalculationSettings settings)
{
//
// Do not apply adjustment if none option is specified.
if (settings.HighLatitudeAdjustment == HighLatitudeAdjustment.None)
{
return(raw);
}
// Copy reference.
var method = settings.HighLatitudeAdjustment;
var imsak = raw.Imsak;
var fajr = raw.Fajr;
var sunrise = raw.Sunrise;
var sunset = raw.Sunset;
var maghrib = raw.Maghrib;
var isha = raw.Isha;
var imsakParameterValue = settings.ImsakParameter.Value;
var fajrParameterValue = settings.CalculationMethod.FajrParameter.Value;
var maghribParameterValue = settings.CalculationMethod.MaghribParameter.Value;
var ishaParameterValue = settings.CalculationMethod.IshaParameter.Value;
// Compute sunrise to sunset difference.
var diff = DateTimeMath.ComputeDuration(raw.Sunrise, raw.Sunset);
// Adjust.
raw.Imsak = AdjustForHighLatitude(method, imsak, sunrise, imsakParameterValue, diff, Direction.CounterClockwise);
raw.Fajr = AdjustForHighLatitude(method, fajr, sunrise, fajrParameterValue, diff, Direction.CounterClockwise);
raw.Maghrib = AdjustForHighLatitude(method, maghrib, sunset, maghribParameterValue, diff, Direction.Clockwise);
raw.Isha = AdjustForHighLatitude(method, isha, sunset, ishaParameterValue, diff, Direction.Clockwise);
return(raw);
}
/// <summary>
/// Adjust calculated prayer time to high latitude adjustment.
/// </summary>
private static double AdjustForHighLatitude(HighLatitudeAdjustment method, double time, double baseTime, double angle, double diff, Direction direction)
{
// Compute night fraction and duration.
var nightFraction = AstronomyMath.GetNightFraction(method, angle, diff);
var duration = direction == Direction.Clockwise
? DateTimeMath.ComputeDuration(time, baseTime)
: DateTimeMath.ComputeDuration(baseTime, time);
// Copy reference;
var newTime = time;
if (duration > nightFraction)
{
var adjustment = direction == Direction.Clockwise ? nightFraction : -nightFraction;
newTime = baseTime + adjustment;
}
return(newTime);
}
public void TestComputeDurationFrom10To23()
{
Assert.Equal(13.0, DateTimeMath.ComputeDuration(23.0, 10.0), 5);
}