package net.minecraft.server.advancements;

import it.unimi.dsi.fastutil.Stack;
import it.unimi.dsi.fastutil.objects.ObjectArrayList;
import java.util.Optional;
import java.util.function.Predicate;
import net.minecraft.advancements.Advancement;
import net.minecraft.advancements.AdvancementNode;
import net.minecraft.advancements.DisplayInfo;

public class AdvancementVisibilityEvaluator {
	private static final int VISIBILITY_DEPTH = 2;

	private static AdvancementVisibilityEvaluator.VisibilityRule evaluateVisibilityRule(final Advancement advancement, final boolean isDone) {
		Optional<DisplayInfo> display = advancement.display();
		if (display.isEmpty()) {
			return AdvancementVisibilityEvaluator.VisibilityRule.HIDE;
		} else if (isDone) {
			return AdvancementVisibilityEvaluator.VisibilityRule.SHOW;
		} else {
			return ((DisplayInfo)display.get()).isHidden()
				? AdvancementVisibilityEvaluator.VisibilityRule.HIDE
				: AdvancementVisibilityEvaluator.VisibilityRule.NO_CHANGE;
		}
	}

	private static boolean evaluateVisiblityForUnfinishedNode(final Stack<AdvancementVisibilityEvaluator.VisibilityRule> ascendants) {
		for (int i = 0; i <= 2; i++) {
			AdvancementVisibilityEvaluator.VisibilityRule visibility = ascendants.peek(i);
			if (visibility == AdvancementVisibilityEvaluator.VisibilityRule.SHOW) {
				return true;
			}

			if (visibility == AdvancementVisibilityEvaluator.VisibilityRule.HIDE) {
				return false;
			}
		}

		return false;
	}

	private static boolean evaluateVisibility(
		final AdvancementNode node,
		final Stack<AdvancementVisibilityEvaluator.VisibilityRule> ascendants,
		final Predicate<AdvancementNode> isDoneTest,
		final AdvancementVisibilityEvaluator.Output output
	) {
		boolean isSelfDone = isDoneTest.test(node);
		AdvancementVisibilityEvaluator.VisibilityRule descendantVisibility = evaluateVisibilityRule(node.advancement(), isSelfDone);
		boolean isSelfOrDescendantDone = isSelfDone;
		ascendants.push(descendantVisibility);

		for (AdvancementNode child : node.children()) {
			isSelfOrDescendantDone |= evaluateVisibility(child, ascendants, isDoneTest, output);
		}

		boolean visiblity = isSelfOrDescendantDone || evaluateVisiblityForUnfinishedNode(ascendants);
		ascendants.pop();
		output.accept(node, visiblity);
		return isSelfOrDescendantDone;
	}

	public static void evaluateVisibility(final AdvancementNode node, final Predicate<AdvancementNode> isDone, final AdvancementVisibilityEvaluator.Output output) {
		AdvancementNode root = node.root();
		Stack<AdvancementVisibilityEvaluator.VisibilityRule> visibilityStack = new ObjectArrayList<>();

		for (int i = 0; i <= 2; i++) {
			visibilityStack.push(AdvancementVisibilityEvaluator.VisibilityRule.NO_CHANGE);
		}

		evaluateVisibility(root, visibilityStack, isDone, output);
	}

	@FunctionalInterface
	public interface Output {
		void accept(AdvancementNode advancement, boolean visible);
	}

	private static enum VisibilityRule {
		SHOW,
		HIDE,
		NO_CHANGE;
	}
}