using VoxelEngine.World.WorldGen;
using Xunit;

namespace VoxelEngine.Tests.WorldGen;

public class VoronoiCellsTests
{
    [Fact]
    public void Nearest_IsDeterministic()
    {
        var a = new VoronoiCells(42, 96f);
        var b = new VoronoiCells(42, 96f);
        Assert.Equal(a.Nearest(123.4f, 56.7f), b.Nearest(123.4f, 56.7f));
    }

    [Fact]
    public void Nearest_IsLocallyConstant()
    {
        var cells = new VoronoiCells(42, 96f);
        // Two points a tiny step apart almost always share a cell.
        var c1 = cells.Nearest(500f, 500f);
        var c2 = cells.Nearest(500.01f, 500.01f);
        Assert.Equal(c1.Id, c2.Id);
    }

    [Fact]
    public void DifferentSeeds_DifferAtSomePoint()
    {
        var a = new VoronoiCells(1, 96f);
        var b = new VoronoiCells(2, 96f);
        bool anyDiff = false;
        for (int i = 0; i < 50 && !anyDiff; i++)
            anyDiff = a.Nearest(i * 31f, i * 17f).Id != b.Nearest(i * 31f, i * 17f).Id;
        Assert.True(anyDiff);
    }
}