AssetRipper_AssetRipper/Source/AssetRipper.Numerics.Tests/RelativeDistanceTests.cs

namespace AssetRipper.Numerics.Tests;

public class RelativeDistanceTests
{
	private static readonly Random random = new Random(12345);
	private static readonly float[] randomFloats = MakeFloats(60);

	private static float[] MakeFloats(int count)
	{
		float[] result = new float[count];
		for (int i = 0; i < count; i++)
		{
			result[i] = 4 * random.NextSingle() - 2;//-2 to 2
		}
		return result;
	}

	[Test]
	public void ValuesOfOppositeSignsHaveDistanceOne()
	{
		Assert.That(RelativeDistanceMethods.RelativeDistance(5f, -3f), Is.EqualTo(1f));
	}

	[Test]
	public void EqualValuesHaveDistanceZero()
	{
		using (Assert.EnterMultipleScope())
		{
			foreach (float value in randomFloats)
			{
				AssertEqualZero(value);
			}
		}

		static void AssertEqualZero(float value)
		{
			float distance = RelativeDistanceMethods.RelativeDistance(value, value);
			Assert.That(distance, Is.Zero, () => $"Value {value} did not have zero distance with itself.");
		}
	}

	[Test]
	public void DistanceIsNonnegativeAndSymmetric()
	{
		using (Assert.EnterMultipleScope())
		{
			for (int i = 0; i < randomFloats.Length - 1; i++)
			{
				float value1 = randomFloats[i];
				float value2 = randomFloats[i + 1];
				AssertSymmetry(value1, value2);
			}
		}

		static void AssertSymmetry(float value1, float value2)
		{
			float distanceA = RelativeDistanceMethods.RelativeDistance(value1, value2);
			Assert.That(distanceA, Is.GreaterThanOrEqualTo(0f), () => $"Values {value1} and {value2} had negative distance.");
			float distanceB = RelativeDistanceMethods.RelativeDistance(value2, value1);
			Assert.That(distanceA, Is.EqualTo(distanceB), () => $"Values {value1} and {value2} did not exhibit symmetry.");
		}
	}

	[Test]
	public void TriangleInequalityHolds()
	{
		using (Assert.EnterMultipleScope())
		{
			for (int i = 0; i < randomFloats.Length - 2; i++)
			{
				float value1 = randomFloats[i];
				float value2 = randomFloats[i + 1];
				float value3 = randomFloats[i + 2];
				AssertTriangleInequality(value1, value2, value3);
			}
		}

		static void AssertTriangleInequality(float value1, float value2, float value3)
		{
			float distanceA = RelativeDistanceMethods.RelativeDistance(value1, value2);
			float distanceB = RelativeDistanceMethods.RelativeDistance(value2, value3);
			float distanceC = RelativeDistanceMethods.RelativeDistance(value1, value3);
			Assert.That(distanceA + distanceB, Is.GreaterThanOrEqualTo(distanceC), () => $"Values {value1}, {value2}, and {value3} did not adhere to the triangle inequality.");
		}
	}

	[Test]
	public void DistanceIsTheSameInMultipleDimensions()
	{
		using (Assert.EnterMultipleScope())
		{
			for (int i = 0; i < randomFloats.Length - 1; i++)
			{
				float value1 = randomFloats[i];
				float value2 = randomFloats[i + 1];
				AssertMultipleDimensionEquality(value1, value2);
			}
		}

		static void AssertMultipleDimensionEquality(float value1, float value2)
		{
			float distance1D = RelativeDistanceMethods.RelativeDistance(value1, value2);
			float distance2D = RelativeDistanceMethods.RelativeDistance(new Vector2(value1, 0), new Vector2(value2, 0));
			float distance3D = RelativeDistanceMethods.RelativeDistance(new Vector3(value1, 0, 0), new Vector3(value2, 0, 0));
			float distance4D = RelativeDistanceMethods.RelativeDistance(new Vector4(value1, 0, 0, 0), new Vector4(value2, 0, 0, 0));
			using (Assert.EnterMultipleScope())
			{
				Assert.That(distance2D, Is.EqualTo(distance1D), () => $"Values {value1} and {value2} did not have the same distance in 2 dimensions.");
				Assert.That(distance3D, Is.EqualTo(distance1D), () => $"Values {value1} and {value2} did not have the same distance in 3 dimensions.");
				Assert.That(distance4D, Is.EqualTo(distance1D), () => $"Values {value1} and {value2} did not have the same distance in 4 dimensions.");
			}
		}
	}

	[Test]
	public void ComparingZeroWithItselfIsZero()
	{
		using (Assert.EnterMultipleScope())
		{
			Assert.That(RelativeDistanceMethods.RelativeDistance(0f, 0f), Is.Zero, () => $"1D distance between zero was not zero.");
			Assert.That(RelativeDistanceMethods.RelativeDistance(Vector2.Zero, Vector2.Zero), Is.Zero, () => $"2D distance between zero was not zero.");
			Assert.That(RelativeDistanceMethods.RelativeDistance(Vector3.Zero, Vector3.Zero), Is.Zero, () => $"3D distance between zero was not zero.");
			Assert.That(RelativeDistanceMethods.RelativeDistance(Vector4.Zero, Vector4.Zero), Is.Zero, () => $"4D distance between zero was not zero.");
		}
	}
}