package net.minecraft.world.level.levelgen;

import com.mojang.datafixers.util.Either;
import com.mojang.serialization.Codec;
import java.util.function.Function;
import net.minecraft.world.level.dimension.DimensionType;

/**
 * Represents a resolvable height value, or y coordinate, based on the world minimum and maximum height.
 * Can take one of the following three forms:
 * <ul>
 * <li>An absolute y value ({@link Absolute}).</li>
 * <li>A height above the lowest valid y value in the level ({@link AboveBottom}).</li>
 * <li>A height below the highest valid y value in the level ({@link BelowTop}).</li>
 * </ul>
 */
public interface VerticalAnchor {
	Codec<VerticalAnchor> CODEC = Codec.xor(VerticalAnchor.Absolute.CODEC, Codec.xor(VerticalAnchor.AboveBottom.CODEC, VerticalAnchor.BelowTop.CODEC))
		.xmap(VerticalAnchor::merge, VerticalAnchor::split);
	VerticalAnchor BOTTOM = aboveBottom(0);
	VerticalAnchor TOP = belowTop(0);

	static VerticalAnchor absolute(int value) {
		return new VerticalAnchor.Absolute(value);
	}

	static VerticalAnchor aboveBottom(int value) {
		return new VerticalAnchor.AboveBottom(value);
	}

	static VerticalAnchor belowTop(int value) {
		return new VerticalAnchor.BelowTop(value);
	}

	static VerticalAnchor bottom() {
		return BOTTOM;
	}

	static VerticalAnchor top() {
		return TOP;
	}

	private static VerticalAnchor merge(Either<VerticalAnchor.Absolute, Either<VerticalAnchor.AboveBottom, VerticalAnchor.BelowTop>> anchor) {
		return anchor.map(Function.identity(), Either::unwrap);
	}

	private static Either<VerticalAnchor.Absolute, Either<VerticalAnchor.AboveBottom, VerticalAnchor.BelowTop>> split(VerticalAnchor anchor) {
		return anchor instanceof VerticalAnchor.Absolute
			? Either.left((VerticalAnchor.Absolute)anchor)
			: Either.right(
				anchor instanceof VerticalAnchor.AboveBottom ? Either.left((VerticalAnchor.AboveBottom)anchor) : Either.right((VerticalAnchor.BelowTop)anchor)
			);
	}

	int resolveY(WorldGenerationContext context);

	public record AboveBottom(int offset) implements VerticalAnchor {
		public static final Codec<VerticalAnchor.AboveBottom> CODEC = Codec.intRange(DimensionType.MIN_Y, DimensionType.MAX_Y)
			.fieldOf("above_bottom")
			.<VerticalAnchor.AboveBottom>xmap(VerticalAnchor.AboveBottom::new, VerticalAnchor.AboveBottom::offset)
			.codec();

		@Override
		public int resolveY(WorldGenerationContext context) {
			return context.getMinGenY() + this.offset;
		}

		public String toString() {
			return this.offset + " above bottom";
		}
	}

	public record Absolute(int y) implements VerticalAnchor {
		public static final Codec<VerticalAnchor.Absolute> CODEC = Codec.intRange(DimensionType.MIN_Y, DimensionType.MAX_Y)
			.fieldOf("absolute")
			.<VerticalAnchor.Absolute>xmap(VerticalAnchor.Absolute::new, VerticalAnchor.Absolute::y)
			.codec();

		@Override
		public int resolveY(WorldGenerationContext context) {
			return this.y;
		}

		public String toString() {
			return this.y + " absolute";
		}
	}

	public record BelowTop(int offset) implements VerticalAnchor {
		public static final Codec<VerticalAnchor.BelowTop> CODEC = Codec.intRange(DimensionType.MIN_Y, DimensionType.MAX_Y)
			.fieldOf("below_top")
			.<VerticalAnchor.BelowTop>xmap(VerticalAnchor.BelowTop::new, VerticalAnchor.BelowTop::offset)
			.codec();

		@Override
		public int resolveY(WorldGenerationContext context) {
			return context.getGenDepth() - 1 + context.getMinGenY() - this.offset;
		}

		public String toString() {
			return this.offset + " below top";
		}
	}
}