using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.World;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using DatReaderWriter.Types;
using Xunit;

namespace AcDream.Core.Tests.World;

public sealed class SkyDescLoaderTests
{
    /// <summary>
    /// Hand-build a Region with a minimal sky descriptor to feed the
    /// loader without needing real dat bytes. The LoadFromRegion
    /// separator exists precisely for this — keeps the parsing logic
    /// testable independent of DatCollection.
    /// </summary>
    private static Region MakeRegion(float dirBright, byte rBgrOrder)
    {
        var region = new Region();
        region.PartsMask = PartsMask.HasSkyInfo;

        var sky = new SkyDesc
        {
            TickSize = 1.0,
            LightTickSize = 2.0,
        };

        var dg = new DayGroup
        {
            ChanceOfOccur = 1.0f,
        };

        var time = new SkyTimeOfDay
        {
            Begin         = 0.5f,
            DirBright     = dirBright,
            DirHeading    = 180f,
            DirPitch      = 70f,
            DirColor      = new ColorARGB { Blue = 0, Green = 0, Red = rBgrOrder, Alpha = 255 },
            AmbBright     = 0.4f,
            AmbColor      = new ColorARGB { Blue = 100, Green = 100, Red = 100, Alpha = 255 },
            MinWorldFog   = 120f,
            MaxWorldFog   = 400f,
            WorldFogColor = new ColorARGB { Blue = 50, Green = 50, Red = 50, Alpha = 255 },
            WorldFog      = 1,  // Linear
        };

        dg.SkyTime.Add(time);
        sky.DayGroups.Add(dg);
        region.SkyInfo = sky;

        return region;
    }

    [Fact]
    public void LoadFromRegion_ConvertsFogFields()
    {
        var region = MakeRegion(dirBright: 1.5f, rBgrOrder: 200);
        var loaded = SkyDescLoader.LoadFromRegion(region);

        Assert.NotNull(loaded);
        Assert.Equal(1.0, loaded!.TickSize);
        Assert.Single(loaded.DayGroups);
        var grp = loaded.DayGroups[0];
        Assert.Single(grp.SkyTimes);

        var kf = grp.SkyTimes[0].Keyframe;
        Assert.Equal(120f, kf.FogStart);
        Assert.Equal(400f, kf.FogEnd);
        Assert.Equal(FogMode.Linear, kf.FogMode);
    }

    [Fact]
    public void LoadFromRegion_CapturesSkyObjectPesId()
    {
        var region = MakeRegion(dirBright: 1.0f, rBgrOrder: 255);
        var dg = region.SkyInfo!.DayGroups[0];
        dg.SkyObjects.Add(new SkyObject
        {
            BeginTime = 0f,
            EndTime = 1f,
            DefaultGfxObjectId = 0x01004C44u,
            DefaultPesObjectId = 0x3300042Cu,
            Properties = 0x05,
        });

        var loaded = SkyDescLoader.LoadFromRegion(region);

        Assert.NotNull(loaded);
        var obj = Assert.Single(loaded!.DayGroups[0].SkyObjects);
        Assert.Equal(0x01004C44u, obj.GfxObjId);
        Assert.Equal(0x3300042Cu, obj.PesObjectId);
        Assert.True(obj.IsPostScene);
    }

    [Fact]
    public void LoadFromRegion_SunColor_UsesRetailSunVectorMagnitude()
    {
        // The loader stores DirColor and DirBright RAW. The SunColor property
        // composes them via |sunVec| per retail's UpdateLightsInternal at
        // 0x59b57c (decomp 424118) — the diffuse magnitude is sqrt(x²+y²+z²)
        // where the sun vector is built from heading/pitch/brightness with
        // Y unscaled by brightness (decomp 261352).
        //
        // For this region:  H=180°, P=70°, B=1.5
        //   sunVec = (sin(180)*1.5*cos(70), cos(70), 1.5*sin(70))
        //          = (0, 0.342, 1.410)
        //   |sunVec| = sqrt(0 + 0.117 + 1.988) = 1.4509
        // DirColor.X = 200/255 = 0.7843
        // SunColor.X = 0.7843 × 1.4509 = 1.138
        var region = MakeRegion(dirBright: 1.5f, rBgrOrder: 200);
        var loaded = SkyDescLoader.LoadFromRegion(region);
        Assert.NotNull(loaded);

        var kf = loaded!.DayGroups[0].SkyTimes[0].Keyframe;
        Assert.InRange(kf.SunColor.X, 1.13f, 1.15f);
    }

    [Fact]
    public void LoadFromRegion_NoSkyInfo_ReturnsNull()
    {
        var region = new Region { PartsMask = 0 };
        Assert.Null(SkyDescLoader.LoadFromRegion(region));
    }

    [Fact]
    public void BuildDefaultProvider_FromDatKeyframes_SupportsInterpolation()
    {
        var region = MakeRegion(dirBright: 1.0f, rBgrOrder: 255);
        var loaded = SkyDescLoader.LoadFromRegion(region)!;
        var provider = loaded.BuildDefaultProvider();

        // Exactly one keyframe: interpolation at any t returns it.
        var s = provider.Interpolate(0.1f);
        Assert.InRange(s.SunColor.X, 0.99f, 1.01f);
    }

    [Fact]
    public void SkyObjectData_IsVisible_HandlesWrap()
    {
        var obj = new SkyObjectData
        {
            BeginTime = 0.9f,  // wraps across midnight
            EndTime   = 0.1f,
        };

        Assert.True(obj.IsVisible(0.95f));   // near end of day
        Assert.True(obj.IsVisible(0.05f));   // just after midnight
        Assert.False(obj.IsVisible(0.5f));   // mid-day (not visible)
    }

    [Fact]
    public void SkyObjectData_CurrentAngle_LerpsAcrossWindow()
    {
        var obj = new SkyObjectData
        {
            BeginTime  = 0.25f,
            EndTime    = 0.75f,
            BeginAngle = 0f,
            EndAngle   = 180f,
        };

        // Middle of the window → 90°.
        Assert.Equal(90f, obj.CurrentAngle(0.5f), precision: 2);
        // At begin → begin angle.
        Assert.Equal(0f,  obj.CurrentAngle(0.25f), precision: 2);
    }
}