SlimeDream/terrain/Tile.cs

using Dictionary = Godot.Collections.Dictionary;

public readonly record struct TilePos(int X, int Y)
{
	public TilePos GetNeighbor(Side side)
		=> side switch {
			Side.Left   => new(X - 1, Y),
			Side.Top    => new(X, Y - 1),
			Side.Right  => new(X + 1, Y),
			Side.Bottom => new(X, Y + 1),
			_ => throw new ArgumentException($"Invalid Side value '{side}'", nameof(side)),
		};

	public TilePos GetNeighbor(Corner corner)
		=> corner switch {
			Corner.TopLeft     => new(X - 1, Y - 1),
			Corner.TopRight    => new(X + 1, Y - 1),
			Corner.BottomRight => new(X + 1, Y + 1),
			Corner.BottomLeft  => new(X - 1, Y + 1),
			_ => throw new ArgumentException($"Invalid Corner value '{corner}'", nameof(corner)),
		};

	public static TilePos From(Vector2I value) => new(value.X, value.Y);
	public Vector2I ToVector2I() => new(X, Y);
}

public struct Tile
{
	public Corners<float> Height;

	// TODO: Replace with enum or something more permanent?
	public int TexturePrimary;
	public int TextureSecondary;
	public int TextureBlend;


	public static Tile FromDictionary(Dictionary dict)
	{
		if (dict == null) return default;

		float topLeft, topRight, bottomRight, bottomLeft;
		switch (dict["heights"]) {
			case { VariantType: Variant.Type.Float } variant:
				var height = (float)variant;
				(topLeft, topRight, bottomRight, bottomLeft) = (height, height, height, height);
				break;
			case { VariantType: Variant.Type.PackedFloat32Array } variant:
				var heights = (float[])variant;
				(topLeft, topRight, bottomRight, bottomLeft) = (heights[0], heights[1], heights[2], heights[3]);
				break;
			default: throw new Exception("Invalid variant type");
		};

		int texturePrimary, textureSecondary, textureBlend;
		switch (dict["texture"]) {
			case { VariantType: Variant.Type.Int } variant:
				var texture = (int)variant;
				(texturePrimary, textureSecondary, textureBlend) = (texture, 0, 0);
				break;
			case { VariantType: Variant.Type.PackedInt32Array } variant:
				var textures = (int[])variant;
				(texturePrimary, textureSecondary, textureBlend) = (textures[0], textures[1], textures[2]);
				break;
			default: throw new Exception("Invalid variant type");
		};

		return new(){
			Height = new(topLeft, topRight, bottomRight, bottomLeft),
			TexturePrimary   = texturePrimary,
			TextureSecondary = textureSecondary,
			TextureBlend     = textureBlend,
		};
	}

	public readonly Dictionary ToDictionary()
	{
		if (Height.IsZeroApprox() && (TexturePrimary == 0) && (TextureBlend == 0))
			return null;
		return new(){
			["heights"] = Height.IsEqualApprox() ? Height.TopLeft : new[]{ Height.TopLeft, Height.TopRight, Height.BottomRight, Height.BottomLeft },
			["texture"] = (TextureBlend == 0) ? TexturePrimary : new[]{ TexturePrimary, TextureSecondary, TextureBlend },
		};
	}
}

public struct Corners<T>(T topLeft, T topRight, T bottomRight, T bottomLeft)
{
	public T TopLeft     = topLeft;
	public T TopRight    = topRight;
	public T BottomRight = bottomRight;
	public T BottomLeft  = bottomLeft;

	public T this[Corner corner] {
		readonly get => corner switch {
			Corner.TopLeft     => TopLeft,
			Corner.TopRight    => TopRight,
			Corner.BottomRight => BottomRight,
			Corner.BottomLeft  => BottomLeft,
			_ => throw new ArgumentException($"Invalid Corner value '{corner}'", nameof(corner)),
		};
		set { switch (corner) {
			case Corner.TopLeft     : TopLeft     = value; break;
			case Corner.TopRight    : TopRight    = value; break;
			case Corner.BottomRight : BottomRight = value; break;
			case Corner.BottomLeft  : BottomLeft  = value; break;
			default: throw new ArgumentException($"Invalid Corner value '{corner}'", nameof(corner));
		} }
	}
}

public static class CornersExtensions
{
	public static void Adjust(this ref Corners<float> self, float amount)
	{
		self.TopLeft     += amount;
		self.TopRight    += amount;
		self.BottomRight += amount;
		self.BottomLeft  += amount;
	}

	public static bool IsZeroApprox(this Corners<float> self)
		=> Mathf.IsZeroApprox(self.TopLeft    ) && Mathf.IsZeroApprox(self.TopRight  )
		&& Mathf.IsZeroApprox(self.BottomRight) && Mathf.IsZeroApprox(self.BottomLeft);

	public static bool IsEqualApprox(this Corners<float> self)
		=> Mathf.IsEqualApprox(self.TopLeft, self.TopRight   )
		&& Mathf.IsEqualApprox(self.TopLeft, self.BottomRight)
		&& Mathf.IsEqualApprox(self.TopLeft, self.BottomLeft );
}