implements PeekingIterator<T> {
    private final Queue<T> queue;

    BreadthFirstIterator(T root) {
      this.queue = new ArrayDeque<>();
      queue.add(root);
    }

    @Override
    public boolean hasNext() {
      return !queue.isEmpty();
    }

    @Override
    public T peek() {
      return queue.element();
    }

    @Override
    public T next() {

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.SampleElements.Strings;
import java.util.List;
import java.util.Queue;
import org.jspecify.annotations.NullMarked;

/**
 * Create queue of strings for tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@NullMarked
public abstract class TestStringQueueGenerator implements TestQueueGenerator<String> {
  @Override

 *   <li>{@code PRE_PROCESSING} - Represents the pre-processing state.</li>
 *   <li>{@code POST_PROCESSING} - Represents the post-processing state.</li>
 *   <li>{@code NO_URL_IN_QUEUE} - Indicates that there are no URLs in the queue.</li>
 *   <li>{@code WAIT_NEW_URL} - Indicates that the crawler is waiting for new URLs.</li>
 * </ul>
 */
public interface IntervalController {
    /** Constant representing the pre-processing state. */

 * and when waiting for new URLs.
 * The delays are configurable via constructor parameters.
 *
 */
public class DefaultIntervalController extends AbstractIntervalController {

    /** Delay in milliseconds after processing a URL */
    protected long delayMillisAfterProcessing = 0L;

    /** Delay in milliseconds when no URL is in the queue */

    private final Queue<T> queue;

    UnIterableQueue(Queue<T> queue) {
      this.queue = queue;
    }

    @Override
    public Iterator<T> iterator() {
      throw new UnsupportedOperationException();
    }

    @Override
    protected Queue<T> delegate() {
      return queue;
    }
  }

  public void testIndexOf_empty() {

            errorsField.setAccessible(true);
            Queue<String> errors = (Queue<String>) errorsField.get(null);
            errors.clear();
        } catch (Exception e) {
            // Ignore if field doesn't exist
        }

        // Add some errors to the queue
        Crawler.addError("Error 1");
        Crawler.addError("Error 2");

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayList;
import java.util.List;

/**
 * Creates, based on your criteria, a JUnit test suite that exhaustively tests a queue
 * implementation.
 *
 * @author Jared Levy
 */
@GwtIncompatible
public final class QueueTestSuiteBuilder<E>
    extends AbstractCollectionTestSuiteBuilder<QueueTestSuiteBuilder<E>, E> {

 *   <li>Before processing a URL ({@link #delayBeforeProcessing()})</li>
 *   <li>After processing a URL ({@link #delayAfterProcessing()})</li>
 *   <li>When there are no URLs in the queue ({@link #delayAtNoUrlInQueue()})</li>
 *   <li>While waiting for new URLs to be added to the queue ({@link #delayForWaitingNewUrl()})</li>
 * </ul>
 *
 * <p>
 * Subclasses are responsible for implementing the abstract methods to define the actual delay

import org.opensearch.index.query.functionscore.RandomScoreFunctionBuilder;
import org.opensearch.search.sort.SortBuilders;
import org.opensearch.search.sort.SortOrder;

/**
 * Fess-specific URL queue service that extends OpenSearch URL queue functionality.
 * This service provides customized URL fetching strategies including sequential and random ordering
 * based on crawling configuration parameters.
 */

    private final Queue<T> queue;

    UnIterableQueue(Queue<T> queue) {
      this.queue = queue;
    }

    @Override
    public Iterator<T> iterator() {
      throw new UnsupportedOperationException();
    }

    @Override
    protected Queue<T> delegate() {
      return queue;
    }
  }

  public void testIndexOf_empty() {