package net.minecraft.world.level.lighting;

import it.unimi.dsi.fastutil.longs.LongLinkedOpenHashSet;
import java.util.Objects;

public class LeveledPriorityQueue {
	private final int levelCount;
	private final LongLinkedOpenHashSet[] queues;
	private int firstQueuedLevel;

	public LeveledPriorityQueue(final int levelCount, final int minSize) {
		this.levelCount = levelCount;
		this.queues = new LongLinkedOpenHashSet[levelCount];

		for (int i = 0; i < levelCount; i++) {
			this.queues[i] = new LongLinkedOpenHashSet(minSize, 0.5F) {
				{
					Objects.requireNonNull(LeveledPriorityQueue.this);
				}

				@Override
				protected void rehash(final int newN) {
					if (newN > minSize) {
						super.rehash(newN);
					}
				}
			};
		}

		this.firstQueuedLevel = levelCount;
	}

	public long removeFirstLong() {
		LongLinkedOpenHashSet queue = this.queues[this.firstQueuedLevel];
		long result = queue.removeFirstLong();
		if (queue.isEmpty()) {
			this.checkFirstQueuedLevel(this.levelCount);
		}

		return result;
	}

	public boolean isEmpty() {
		return this.firstQueuedLevel >= this.levelCount;
	}

	public void dequeue(final long node, final int key, final int upperBound) {
		LongLinkedOpenHashSet queue = this.queues[key];
		queue.remove(node);
		if (queue.isEmpty() && this.firstQueuedLevel == key) {
			this.checkFirstQueuedLevel(upperBound);
		}
	}

	public void enqueue(final long node, final int key) {
		this.queues[key].add(node);
		if (this.firstQueuedLevel > key) {
			this.firstQueuedLevel = key;
		}
	}

	private void checkFirstQueuedLevel(final int upperBound) {
		int oldLevel = this.firstQueuedLevel;
		this.firstQueuedLevel = upperBound;

		for (int i = oldLevel + 1; i < upperBound; i++) {
			if (!this.queues[i].isEmpty()) {
				this.firstQueuedLevel = i;
				break;
			}
		}
	}
}