package org.warp.commonutils.type;

import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
import org.warp.commonutils.error.IndexOutOfBoundsException;

public class FastUtilStackSetWrapper<T> implements StackSet<T> {

	private final AddStrategy addStrategy;
	private final ObjectLinkedOpenHashSet<T> linkedHashSet;

	public FastUtilStackSetWrapper(ObjectLinkedOpenHashSet<T> linkedHashSet) {
		this(linkedHashSet, AddStrategy.getDefault());
	}

	public FastUtilStackSetWrapper(ObjectLinkedOpenHashSet<T> linkedHashSet, AddStrategy addStrategy) {
		this.addStrategy = addStrategy;
		this.linkedHashSet = linkedHashSet;
	}

	@Override
	public boolean push(T o) {
		switch (addStrategy) {
			case KEEP_POSITION:
				return linkedHashSet.add(o);
			case OVERWRITE_POSITION:
				return linkedHashSet.addAndMoveToLast(o);
			default:
				throw new UnsupportedOperationException("Unsupported strategy type: " + addStrategy);
		}
	}

	@Override
	public T pop() {
		return linkedHashSet.removeLast();
	}

	@Override
	public boolean isEmpty() {
		return linkedHashSet.isEmpty();
	}

	@Override
	public T top() {
		return linkedHashSet.last();
	}

	@Override
	public T peek(int i) {
		var size = linkedHashSet.size();
		int positionFromBottom = size - 1 - i;

		if (positionFromBottom < 0 || positionFromBottom >= size) {
			throw new IndexOutOfBoundsException(positionFromBottom, 0, size);
		}

		var it = linkedHashSet.iterator();
		// Skip middle elements
		if (positionFromBottom > 0) {
			it.skip(positionFromBottom);
		}
		return it.next();
	}
}