namespace Nonemm.Core.Tests;

public class SunTimesTests
{
    private static readonly TimeSpan CloseEnough = TimeSpan.FromMinutes(3);

    private static void Near(string expected, DateTime actual) =>
        Assert.True(
            (DateTime.Parse(expected, System.Globalization.CultureInfo.InvariantCulture,
                System.Globalization.DateTimeStyles.AdjustToUniversal
                | System.Globalization.DateTimeStyles.AssumeUniversal) - actual).Duration() < CloseEnough,
            $"expected about {expected}, got {actual:yyyy-MM-dd HH:mm}Z");

    [Fact]
    public void MidsummerInLondon()
    {
        (DateTime rise, DateTime set) = Assert.IsType<(DateTime, DateTime)>(
            SunTimes.For(51.48, -0.13, new DateTime(2026, 6, 21, 0, 0, 0, DateTimeKind.Utc)));

        Near("2026-06-21T03:43Z", rise);
        Near("2026-06-21T20:21Z", set);
    }

    [Fact]
    public void MidwinterInLondon()
    {
        (DateTime rise, DateTime set) = Assert.IsType<(DateTime, DateTime)>(
            SunTimes.For(51.48, -0.13, new DateTime(2026, 12, 21, 0, 0, 0, DateTimeKind.Utc)));

        Near("2026-12-21T08:04Z", rise);
        Near("2026-12-21T15:53Z", set);
    }

    [Fact]
    public void TheEquinoxIsAboutSixToSixEverywhereOnTheEquator()
    {
        (DateTime rise, DateTime set) = Assert.IsType<(DateTime, DateTime)>(
            SunTimes.For(0, 0, new DateTime(2026, 3, 20, 0, 0, 0, DateTimeKind.Utc)));

        Near("2026-03-20T06:04Z", rise);
        Near("2026-03-20T18:10Z", set);
    }

    [Fact]
    public void SouthOfTheEquatorTheSeasonsAreTheOtherWayRound()
    {
        (DateTime rise, DateTime set) = Assert.IsType<(DateTime, DateTime)>(
            SunTimes.For(-33.87, 151.21, new DateTime(2026, 6, 21, 0, 0, 0, DateTimeKind.Utc)));

        Near("2026-06-20T21:00Z", rise);
        Near("2026-06-21T06:54Z", set);
    }

    [Fact]
    public void InsideTheArcticCircleTheSunDoesNotSetInJune() =>
        Assert.Null(SunTimes.For(78.22, 15.65, new DateTime(2026, 6, 21, 0, 0, 0, DateTimeKind.Utc)));
}