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package net.jqwik.engine.support.combinatorics;

import org.jspecify.annotations.*;

import java.util.*;

public class SetIterator implements Iterator> {

	private final Iterator> combinedListIterator;
	private final Set> generatedSets = new LinkedHashSet<>();
	private final int setSize;
	private Set next;

	public SetIterator(Iterable elementIterable, int setSize) {
		this.setSize = setSize;
		List> iterables = new ArrayList<>();
		for (int i = 0; i < setSize; i++) {
			iterables.add(elementIterable);
		}
		combinedListIterator = new CombinedIterator<>(iterables);
		next = findNext();
	}

	private Set findNext() {
		while (combinedListIterator.hasNext()) {
			HashSet candidate = new LinkedHashSet<>(combinedListIterator.next());
			if (candidate.size() != setSize || generatedSets.contains(candidate)) {
				continue;
			}
			generatedSets.add(candidate);
			return candidate;
		}
		return null;
	}

	@Override
	public boolean hasNext() {
		return next != null;
	}

	@Override
	public Set next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		Set current = next;
		next = findNext();
		return current;
	}
}