CultMath/tests/CultMath.Tests/MathTests.cs

using CultMath;
using Xunit;

namespace CultMath.Tests;

public sealed class MathTests
{
    [Fact]
    public void FracMatchesShaderStylePositiveAndNegativeValues()
    {
        Assert.Equal(0.25f, math.frac(1.25f));
        Assert.Equal(0.75f, math.frac(-1.25f));
    }

    [Fact]
    public void VectorOperationsAreComponentWise()
    {
        var value = new float3(1.0f, 2.0f, 3.0f) * new float3(4.0f, 5.0f, 6.0f);

        Assert.Equal(new float3(4.0f, 10.0f, 18.0f), value);
    }

    [Fact]
    public void VectorConstructorsAcceptLowerDimensionVectors()
    {
        Assert.Equal(new int2(1, 2), math.int2(1, 2));
        Assert.Equal(new float2(1.0f, 2.0f), math.float2(1.0f, 2.0f));
        Assert.Equal(new float3(1.0f, 1.0f, 1.0f), math.float3(1.0f));
        Assert.Equal(new float4(1.0f, 2.0f, 3.0f, 4.0f), math.float4(new float3(1.0f, 2.0f, 3.0f), 4.0f));
        Assert.Equal(new float3(1.0f, 2.0f, 3.0f), new float3(new float2(1.0f, 2.0f), 3.0f));
        Assert.Equal(new float4(1.0f, 2.0f, 3.0f, 4.0f), new float4(new float2(1.0f, 2.0f), 3.0f, 4.0f));
        Assert.Equal(new float4(1.0f, 2.0f, 3.0f, 4.0f), new float4(new float3(1.0f, 2.0f, 3.0f), 4.0f));
    }

    [Fact]
    public void RectNormalizesBoundsAndContainsPoints()
    {
        var viewport = math.rect(10.0f, 20.0f, -5.0f, -2.0f);

        Assert.Equal(new float2(-5.0f, -2.0f), viewport.min);
        Assert.Equal(new float2(10.0f, 20.0f), viewport.max);
        Assert.Equal(new float2(15.0f, 22.0f), viewport.size);
        Assert.Equal(new float2(2.5f, 9.0f), viewport.center);
        Assert.True(viewport.Contains(new float2(0.0f, 0.0f)));
        Assert.False(viewport.Contains(new float2(11.0f, 0.0f)));
    }

    [Fact]
    public void VectorsExposeCommonReadOnlySwizzles()
    {
        Assert.Equal(new float3(2.0f, 3.0f, 1.0f), new float3(1.0f, 2.0f, 3.0f).yzx);
        Assert.Equal(new float3(3.0f, 2.0f, 1.0f), new float3(1.0f, 2.0f, 3.0f).zyx);
        Assert.Equal(new float2(3.0f, 2.0f), new float3(1.0f, 2.0f, 3.0f).zy);
        Assert.Equal(new float3(1.0f, 2.0f, 4.0f), new float4(1.0f, 2.0f, 3.0f, 4.0f).xyw);
        Assert.Equal(new float3(2.0f, 3.0f, 1.0f), new float4(1.0f, 2.0f, 3.0f, 4.0f).yzx);
        Assert.Equal(new float4(1.0f, 2.0f, 3.0f, 4.0f), new float4(1.0f, new float3(2.0f, 3.0f, 4.0f)));
        Assert.Equal(new float4(1.0f, 2.0f, 3.0f, 4.0f), math.float4(1.0f, new float3(2.0f, 3.0f, 4.0f)));
    }

    [Fact]
    public void VectorsSupportUnityStyleFieldAndSwizzleMutation()
    {
        var position = new float3(1.0f, 2.0f, 3.0f);
        position.y = 5.0f;
        position.xz = new float2(8.0f, 13.0f);

        Assert.Equal(new float3(8.0f, 5.0f, 13.0f), position);

        var bounds = new float4(1.0f, 2.0f, 3.0f, 4.0f);
        bounds.xy = new float2(-1.0f, -2.0f);

        Assert.Equal(new float4(-1.0f, -2.0f, 3.0f, 4.0f), bounds);
    }

    [Fact]
    public void DoubleVectorsSupportDampedMath()
    {
        var value = new double3(1.0, 2.0, 3.0);
        value.xy = new double2(5.0, 8.0);

        Assert.Equal(new double3(5.0, 8.0, 3.0), value);
        Assert.Equal(new double2(Math.Exp(-2.0), Math.Exp(-4.0)), math.exp(new double2(-2.0, -4.0)));
        Assert.Equal(new double3(2.0, 4.0, 6.0), math.lerp(new double3(0.0, 0.0, 0.0), new double3(4.0, 8.0, 12.0), new double3(0.5, 0.5, 0.5)));
    }

    [Fact]
    public void Int2SupportsGridArithmeticAndFloatPromotion()
    {
        var cell = new int2(2, 3);

        Assert.Equal(new int2(3, 5), cell + new int2(1, 2));
        Assert.Equal(new int2(4, 6), cell * new int2(2, 2));
        Assert.Equal(3, cell[1]);

        float2 promoted = cell;
        Assert.Equal(new float2(2.0f, 3.0f), promoted);
    }

    [Fact]
    public void Bool2SupportsHullGridStyleStorage()
    {
        bool2 conductivity = true;

        conductivity.y = false;

        Assert.True(conductivity.x);
        Assert.False(conductivity[1]);
        Assert.Equal(new bool2(false, true), math.bool2(false, true));
    }

    [Fact]
    public void QuaternionLookRotationProducesUnitOrientation()
    {
        var rotation = quaternion.LookRotation(new float3(0.0f, 0.0f, 1.0f), new float3(0.0f, 1.0f, 0.0f));

        Assert.Equal(quaternion.identity, rotation);
        Assert.Equal(1.0f, math.length((float4)quaternion.LookRotation(new float3(1.0f, 0.0f, 0.0f), new float3(0.0f, 1.0f, 0.0f))), precision: 5);
    }

    [Fact]
    public void RandomIsDeterministicAndUnityShaped()
    {
        var a = new Random(1234);
        var b = new Random(1234);

        Assert.Equal(a.NextUInt(), b.NextUInt());
        Assert.Equal(a.NextFloat(), b.NextFloat());

        var bounded = a.NextFloat(-2.0f, 4.0f);
        Assert.True(bounded >= -2.0f && bounded < 4.0f);

        var direction = a.NextFloat2Direction();
        Assert.Equal(1.0f, math.length(direction), precision: 5);

        var point = a.NextFloat3(new float3(-1.0f, -2.0f, -3.0f), new float3(1.0f, 2.0f, 3.0f));
        Assert.True(point.x >= -1.0f && point.x < 1.0f);
        Assert.True(point.y >= -2.0f && point.y < 2.0f);
        Assert.True(point.z >= -3.0f && point.z < 3.0f);
    }

    [Fact]
    public void NormalizeProducesUnitLength()
    {
        var value = math.normalize(new float3(3.0f, 4.0f, 0.0f));

        Assert.Equal(1.0f, math.length(value), precision: 5);
    }

    [Fact]
    public void SmoothstepUsesHermiteRamp()
    {
        Assert.Equal(0.0f, math.smoothstep(0.0f, 1.0f, -1.0f));
        Assert.Equal(0.5f, math.smoothstep(0.0f, 1.0f, 0.5f), precision: 5);
        Assert.Equal(1.0f, math.smoothstep(0.0f, 1.0f, 2.0f));
        Assert.Equal(0.5f, math.smootherstep(0.5f), precision: 5);
    }

    [Fact]
    public void TrigIntrinsicsUseRadians()
    {
        Assert.Equal(1.0f, math.sin(math.HALF_PI), precision: 5);
        Assert.Equal(-1.0f, math.cos(math.PI), precision: 5);
        Assert.Equal(1.0f, math.tan(math.PI * 0.25f), precision: 5);
        Assert.Equal(math.HALF_PI, math.atan2(1.0f, 0.0f), precision: 5);
        Assert.Equal(2, math.min(2, 5));
        Assert.Equal(5, math.max(2, 5));
        Assert.True(math.isinf(float.PositiveInfinity));
    }

    [Fact]
    public void SignIsComponentWiseForSimulationVectors()
    {
        Assert.Equal(-1.0f, math.sign(-12.0f));
        Assert.Equal(0.0f, math.sign(0.0f));
        Assert.Equal(1.0f, math.sign(12.0f));
        Assert.Equal(new float3(-1.0f, 0.0f, 1.0f), math.sign(new float3(-2.0f, 0.0f, 4.0f)));
    }

    [Fact]
    public void RotateTurnsFloat2CounterClockwiseInRadians()
    {
        var rotated = math.rotate(new float2(1.0f, 0.0f), math.HALF_PI);

        Assert.Equal(0.0f, rotated.x, precision: 5);
        Assert.Equal(1.0f, rotated.y, precision: 5);

        var rotatedDegrees = math.rotate_degrees(new float2(0.0f, 1.0f), 90.0f);
        Assert.Equal(-1.0f, rotatedDegrees.x, precision: 5);
        Assert.Equal(0.0f, rotatedDegrees.y, precision: 5);
    }

    [Fact]
    public void AetheriaPrimitivesRemainSmallAndDeterministic()
    {
        Assert.Equal(6.0f, math.csum(new float3(1.0f, 2.0f, 3.0f)));
        Assert.Equal(0.25f, math.unlerp(10.0f, 30.0f, 15.0f));
        Assert.Equal(new float2(0.25f, 0.75f), math.unlerp(new float2(10.0f, 10.0f), new float2(30.0f, 30.0f), new float2(15.0f, 25.0f)));
        Assert.Equal(MathF.Exp(-2.0f), math.decay(1.0f, 2.0f, 1.0f), precision: 5);
        Assert.Equal(1.0f - MathF.Exp(-2.0f), math.damp(0.0f, 1.0f, 2.0f, 1.0f), precision: 5);

        Assert.Equal(15.0f, math.catmullrom(0.0f, 10.0f, 20.0f, 30.0f, 0.5f), precision: 5);
        Assert.Equal(0.25f, math.quadratic_bezier(0.0f, 0.0f, 1.0f, 0.5f), precision: 5);
        Assert.Equal(0.5f, math.cubic_bezier(0.0f, 0.0f, 1.0f, 1.0f, 0.5f), precision: 5);
    }

    [Fact]
    public void SegmentDistanceReportsClosestPoint()
    {
        var distance = math.distance_to_segment(new float2(2.0f, 3.0f), new float2(0.0f, 0.0f), new float2(4.0f, 0.0f), out var closest);

        Assert.Equal(3.0f, distance, precision: 5);
        Assert.Equal(new float2(2.0f, 0.0f), closest);
    }

    [Fact]
    public void FirstOrderInterceptSolvesSimpleClosingTarget()
    {
        var time = math.first_order_intercept_time(
            2.0f,
            new float3(10.0f, 0.0f, 0.0f),
            new float3(-1.0f, 0.0f, 0.0f));

        Assert.Equal(10.0f / 3.0f, time, precision: 5);
    }

    [Fact]
    public void ValueNoiseIsDeterministicAndSmoothAtCellCorners()
    {
        var position = new float2(12.25f, -4.5f);

        Assert.Equal(math.value_noise(position), math.value_noise(position));
        Assert.Equal(math.hash(new float2(3.0f, 5.0f)), math.value_noise(new float2(3.0f, 5.0f)), precision: 5);

        var bicubic = math.value_noise_bicubic(position);
        Assert.True(bicubic > -0.25f && bicubic < 1.25f);
    }

    [Theory]
    [InlineData(0.0f, 0.0f, 0.0f)]
    [InlineData(0.25f, -0.5f, -0.425866783f)]
    [InlineData(12.25f, -4.5f, 0.258312f)]
    [InlineData(536.5106f, 536.5106f, -0.6901103f)]
    public void SimplexNoiseMatchesUnityMathematics(float x, float y, float expected)
    {
        Assert.Equal(expected, math.simplex_noise(new float2(x, y)), precision: 6);
    }

    [Fact]
    public void VoronoiBatchProducesToneMappedColors()
    {
        var xs = new[] { 0.0f, 24.0f, 96.0f };
        var ys = new[] { 0.0f, 36.0f, 144.0f };
        var tones = new[] { CultMathTone.Background, CultMathTone.Header, CultMathTone.Body };
        var spans = new[] { 1920.0f, 8.0f, 8.0f };
        var colors = new Color32[xs.Length];

        Voronoi.SampleTones(xs, ys, tones, spans, 1080.0f, 12, colors);

        Assert.NotEqual(new Color32(), colors[0]);
        Assert.True(colors[1].r > colors[1].g);
        Assert.True(colors[2].r > 120 && colors[2].g > 120 && colors[2].b > 120);
    }

    [Fact]
    public void BatchRadialFalloffAccelerationMatchesScalarContract()
    {
        var xs = new[] { 0.0f, 5.0f, 10.0f };
        var ys = new[] { 0.0f, 0.0f, 0.0f };
        var ax = new float[xs.Length];
        var ay = new float[xs.Length];

        BatchMath.AddRadialFalloffAcceleration2D(xs, ys, 10.0f, 0.0f, 10.0f, 20.0f, ax, ay);

        Assert.True(BatchMath.LaneCount >= 4);
        Assert.Equal(5.0f, ax[0], precision: 5);
        Assert.Equal(7.5f, ax[1], precision: 5);
        Assert.Equal(0.0f, ax[2], precision: 5);
        Assert.Equal(0.0f, ay[0], precision: 5);
    }

    [Fact]
    public void BatchEulerIntegrationHonorsDynamicMask()
    {
        var dynamicMask = new[] { 1.0f, 0.0f };
        var px = new[] { 0.0f, 0.0f };
        var py = new[] { 0.0f, 0.0f };
        var vx = new[] { 1.0f, 1.0f };
        var vy = new[] { 0.0f, 0.0f };
        var ax = new[] { 2.0f, 2.0f };
        var ay = new[] { 0.0f, 4.0f };

        BatchMath.IntegrateSemiImplicitEuler2D(0.5f, dynamicMask, px, py, vx, vy, ax, ay);

        Assert.Equal(2.0f, vx[0], precision: 5);
        Assert.Equal(1.0f, px[0], precision: 5);
        Assert.Equal(1.0f, vx[1], precision: 5);
        Assert.Equal(0.0f, px[1], precision: 5);
        Assert.Equal(0.0f, py[1], precision: 5);
    }
}