minecraft-src/com/mojang/blaze3d/vertex/VertexMultiConsumer.java

package com.mojang.blaze3d.vertex;

import java.util.function.Consumer;
import net.fabricmc.api.EnvType;
import net.fabricmc.api.Environment;

@Environment(EnvType.CLIENT)
public class VertexMultiConsumer {
	public static VertexConsumer create() {
		throw new IllegalArgumentException();
	}

	public static VertexConsumer create(VertexConsumer consumer) {
		return consumer;
	}

	public static VertexConsumer create(VertexConsumer first, VertexConsumer second) {
		return new VertexMultiConsumer.Double(first, second);
	}

	public static VertexConsumer create(VertexConsumer... delegates) {
		return new VertexMultiConsumer.Multiple(delegates);
	}

	@Environment(EnvType.CLIENT)
	static class Double implements VertexConsumer {
		private final VertexConsumer first;
		private final VertexConsumer second;

		public Double(VertexConsumer first, VertexConsumer second) {
			if (first == second) {
				throw new IllegalArgumentException("Duplicate delegates");
			} else {
				this.first = first;
				this.second = second;
			}
		}

		@Override
		public VertexConsumer addVertex(float x, float y, float z) {
			this.first.addVertex(x, y, z);
			this.second.addVertex(x, y, z);
			return this;
		}

		@Override
		public VertexConsumer setColor(int red, int green, int blue, int alpha) {
			this.first.setColor(red, green, blue, alpha);
			this.second.setColor(red, green, blue, alpha);
			return this;
		}

		@Override
		public VertexConsumer setUv(float u, float v) {
			this.first.setUv(u, v);
			this.second.setUv(u, v);
			return this;
		}

		@Override
		public VertexConsumer setUv1(int u, int v) {
			this.first.setUv1(u, v);
			this.second.setUv1(u, v);
			return this;
		}

		@Override
		public VertexConsumer setUv2(int u, int v) {
			this.first.setUv2(u, v);
			this.second.setUv2(u, v);
			return this;
		}

		@Override
		public VertexConsumer setNormal(float normalX, float normalY, float normalZ) {
			this.first.setNormal(normalX, normalY, normalZ);
			this.second.setNormal(normalX, normalY, normalZ);
			return this;
		}

		@Override
		public void addVertex(float x, float y, float z, int color, float u, float v, int packedOverlay, int packedLight, float normalX, float normalY, float normalZ) {
			this.first.addVertex(x, y, z, color, u, v, packedOverlay, packedLight, normalX, normalY, normalZ);
			this.second.addVertex(x, y, z, color, u, v, packedOverlay, packedLight, normalX, normalY, normalZ);
		}
	}

	@Environment(EnvType.CLIENT)
	record Multiple(VertexConsumer[] delegates) implements VertexConsumer {
		Multiple(VertexConsumer[] delegates) {
			for (int i = 0; i < delegates.length; i++) {
				for (int j = i + 1; j < delegates.length; j++) {
					if (delegates[i] == delegates[j]) {
						throw new IllegalArgumentException("Duplicate delegates");
					}
				}
			}

			this.delegates = delegates;
		}

		private void forEach(Consumer<VertexConsumer> action) {
			for (VertexConsumer vertexConsumer : this.delegates) {
				action.accept(vertexConsumer);
			}
		}

		@Override
		public VertexConsumer addVertex(float x, float y, float z) {
			this.forEach(vertexConsumer -> vertexConsumer.addVertex(x, y, z));
			return this;
		}

		@Override
		public VertexConsumer setColor(int red, int green, int blue, int alpha) {
			this.forEach(vertexConsumer -> vertexConsumer.setColor(red, green, blue, alpha));
			return this;
		}

		@Override
		public VertexConsumer setUv(float u, float v) {
			this.forEach(vertexConsumer -> vertexConsumer.setUv(u, v));
			return this;
		}

		@Override
		public VertexConsumer setUv1(int u, int v) {
			this.forEach(vertexConsumer -> vertexConsumer.setUv1(u, v));
			return this;
		}

		@Override
		public VertexConsumer setUv2(int u, int v) {
			this.forEach(vertexConsumer -> vertexConsumer.setUv2(u, v));
			return this;
		}

		@Override
		public VertexConsumer setNormal(float normalX, float normalY, float normalZ) {
			this.forEach(vertexConsumer -> vertexConsumer.setNormal(normalX, normalY, normalZ));
			return this;
		}

		@Override
		public void addVertex(float x, float y, float z, int color, float u, float v, int packedOverlay, int packedLight, float normalX, float normalY, float normalZ) {
			this.forEach(vertexConsumer -> vertexConsumer.addVertex(x, y, z, color, u, v, packedOverlay, packedLight, normalX, normalY, normalZ));
		}
	}
}