using AcDream.Core.World;
using Xunit;

namespace AcDream.Core.Tests.World;

public sealed class DerethDateTimeTests
{
    [Fact]
    public void DayFraction_AtMidnight_IsZero()
    {
        Assert.Equal(0.0, DerethDateTime.DayFraction(0));
    }

    [Fact]
    public void DayFraction_AtHalfDay_IsHalf()
    {
        Assert.Equal(0.5, DerethDateTime.DayFraction(DerethDateTime.DayTicks / 2), 4);
    }

    [Fact]
    public void DayFraction_WrapsAfterOneDay()
    {
        Assert.Equal(0.0, DerethDateTime.DayFraction(DerethDateTime.DayTicks), 6);
        Assert.Equal(0.25, DerethDateTime.DayFraction(DerethDateTime.DayTicks * 1.25), 4);
    }

    [Fact]
    public void CurrentHour_AtMidnight_IsDarktide()
    {
        Assert.Equal(DerethDateTime.HourName.Darktide, DerethDateTime.CurrentHour(0));
    }

    [Fact]
    public void CurrentHour_AtDawn_IsDawnsong()
    {
        // Dawnsong is the 5th slot (0-indexed slot 4) — day-fraction 4/16 = 0.25.
        double ticks = DerethDateTime.DayTicks * (4.0 / 16.0);
        Assert.Equal(DerethDateTime.HourName.Dawnsong, DerethDateTime.CurrentHour(ticks));
    }

    [Fact]
    public void CurrentHour_AtNoon_IsMidsong()
    {
        // Midsong is 0-indexed slot 8 → day-fraction 0.5.
        double ticks = DerethDateTime.DayTicks * 0.5;
        Assert.Equal(DerethDateTime.HourName.Midsong, DerethDateTime.CurrentHour(ticks));
    }

    [Fact]
    public void IsDaytime_Dawn_True()
    {
        double ticks = DerethDateTime.DayTicks * (4.0 / 16.0);  // Dawnsong start
        Assert.True(DerethDateTime.IsDaytime(ticks));
    }

    [Fact]
    public void IsDaytime_Night_False()
    {
        double ticks = DerethDateTime.DayTicks * (1.0 / 16.0);   // Darktide-and-Half
        Assert.False(DerethDateTime.IsDaytime(ticks));
    }

    [Fact]
    public void ToCalendar_PY0Day1_Snowreap()
    {
        var cal = DerethDateTime.ToCalendar(0);
        Assert.Equal(0, cal.Year);
        Assert.Equal(DerethDateTime.MonthName.Snowreap, cal.Month);
        Assert.Equal(1, cal.Day);
    }

    [Fact]
    public void ToCalendar_AdvancesCorrectly()
    {
        // One year from start → PY 1, Snowreap 1.
        var cal = DerethDateTime.ToCalendar(DerethDateTime.YearTicks);
        Assert.Equal(1, cal.Year);
        Assert.Equal(DerethDateTime.MonthName.Snowreap, cal.Month);
        Assert.Equal(1, cal.Day);

        // One month into year 1.
        var cal2 = DerethDateTime.ToCalendar(DerethDateTime.YearTicks + DerethDateTime.MonthTicks);
        Assert.Equal(1, cal2.Year);
        Assert.Equal(DerethDateTime.MonthName.ColdMeet, cal2.Month);
    }
}