private static double Interpolate(
SolarTimes solarTimes,
double dayValue,
double nightValue,
TimeSpan transitionDuration,
double transitionOffset,
DateTimeOffset instant)
{
var sunriseStart = GetSunriseStart(solarTimes.Sunrise, transitionDuration, transitionOffset);
var sunriseEnd = GetSunriseEnd(solarTimes.Sunrise, transitionDuration, transitionOffset);
var sunsetStart = GetSunsetStart(solarTimes.Sunset, transitionDuration, transitionOffset);
var sunsetEnd = GetSunsetEnd(solarTimes.Sunset, transitionDuration, transitionOffset);
// Sunrise transition
var prevSunriseStart = sunriseStart.PreviousBefore(instant);
var nextSunriseEnd = sunriseEnd.NextAfter(instant);
var isDuringSunrise = (nextSunriseEnd - prevSunriseStart).Duration() <= transitionDuration;
if (isDuringSunrise)
{
var progress = (instant - prevSunriseStart) / transitionDuration;
return(dayValue + (nightValue - dayValue) * Math.Cos(progress * Math.PI / 2));
}
// Sunset transition
var prevSunsetStart = sunsetStart.PreviousBefore(instant);
var nextSunsetEnd = sunsetEnd.NextAfter(instant);
var isDuringSunset = (nextSunsetEnd - prevSunsetStart).Duration() <= transitionDuration;
if (isDuringSunset)
{
var progress = (instant - prevSunsetStart) / transitionDuration;
return(dayValue + (nightValue - dayValue) * Math.Sin(progress * Math.PI / 2));
}
// Day time
if (nextSunsetEnd < nextSunriseEnd)
{
return(dayValue);
}
// Night time
return(nightValue);
}