using System.Numerics;
using AcDream.Core.World;
using Xunit;

namespace AcDream.Core.Tests.World;

public sealed class SkyStateTests
{
    [Fact]
    public void Default_Has4Keyframes()
    {
        var sky = SkyStateProvider.Default();
        Assert.Equal(4, sky.KeyframeCount);
    }

    [Fact]
    public void Interpolate_AtExactKeyframe_ReturnsThatFrameData()
    {
        var sky = SkyStateProvider.Default();
        var noon = sky.Interpolate(0.5f);   // noon keyframe

        // Noon sky color should be near white (1.0 ish).
        Assert.InRange(noon.SunColor.X, 0.9f, 1.1f);
        Assert.InRange(noon.SunColor.Y, 0.9f, 1.1f);
    }

    [Fact]
    public void Interpolate_BetweenKeyframes_LerpsColors()
    {
        var sky = SkyStateProvider.Default();
        var dawn  = sky.Interpolate(0.25f);
        var noon  = sky.Interpolate(0.5f);
        var midPt = sky.Interpolate(0.375f);

        // Midpoint should fall between dawn & noon for sun color Y (green channel).
        float low  = System.Math.Min(dawn.SunColor.Y, noon.SunColor.Y);
        float high = System.Math.Max(dawn.SunColor.Y, noon.SunColor.Y);
        Assert.InRange(midPt.SunColor.Y, low, high);
    }

    [Fact]
    public void Interpolate_Wraps_AcrossMidnight()
    {
        var sky = SkyStateProvider.Default();
        var justAfterMidnight = sky.Interpolate(0.01f);

        // Should return finite valid state (not NaN).
        Assert.False(float.IsNaN(justAfterMidnight.SunColor.X));
        Assert.False(float.IsNaN(justAfterMidnight.AmbientColor.X));
    }

    [Fact]
    public void SunDirectionFromKeyframe_ReturnsUnitVector()
    {
        var kf = new SkyKeyframe(
            Begin: 0.5f,
            SunHeadingDeg: 180f,  // south
            SunPitchDeg:   70f,
            SunColor:      Vector3.One,
            AmbientColor:  Vector3.One,
            FogColor:      Vector3.One,
            FogDensity:    0.001f);

        var dir = SkyStateProvider.SunDirectionFromKeyframe(kf);
        Assert.InRange(dir.Length(), 0.99f, 1.01f);
    }

    [Fact]
    public void WorldTimeService_SyncFromServer_SetsTicks()
    {
        var service = new WorldTimeService(SkyStateProvider.Default());
        service.SyncFromServer(12345.0);

        // NowTicks advances by real elapsed time; but immediately after
        // sync it should be at or very close to the synced value.
        Assert.InRange(service.NowTicks, 12345.0, 12346.0);
    }

    [Fact]
    public void WorldTimeService_DayFraction_RespectsSync()
    {
        var service = new WorldTimeService(SkyStateProvider.Default());
        // Need to aim for dayFraction 0.5 (Gloaming-and-Half, slot 15 since tick 0 = slot 7).
        // Sync to (0.5 - 7/16) * DayTicks = (1/16) * DayTicks — 1 slot past Morntide-and-Half = Midsong.
        // Actually simpler: target fraction 7/16 (slot 7 = Morntide-and-Half) by syncing to tick 0.
        service.SyncFromServer(0);

        Assert.InRange(service.DayFraction, 0.43, 0.44);   // 7/16 = 0.4375
        Assert.True(service.IsDaytime);
    }
}