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/*
 * Copyright (c) 2002 - 2006 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 */
package com.ibm.wala.util.graph.traverse;

import com.ibm.wala.util.collections.HashMapFactory;
import com.ibm.wala.util.collections.NonNullSingletonIterator;
import com.ibm.wala.util.graph.Graph;
import java.util.Iterator;
import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
 * This class implements depth-first search over a Graph, return an enumeration of the nodes of the
 * graph in order of increasing discover time. This class follows the outNodes of the graph nodes to
 * define the graph, but this behavior can be changed by overriding the getConnected method.
 */
public class SlowDFSDiscoverTimeIterator extends GraphDFSDiscoverTimeIterator {
  public static final long serialVersionUID = 9439217987188L;

  /** An iterator of child nodes for each node being searched A Map: Node -> Iterator */
  private final Map> pendingChildren = HashMapFactory.make(25);

  /** For use with extreme care by subclasses that know what they're doing. */
  protected SlowDFSDiscoverTimeIterator() {}

  /**
   * Construct a depth-first enumerator starting with a particular node in a directed graph.
   *
   * @param G the graph whose nodes to enumerate
   */
  public SlowDFSDiscoverTimeIterator(Graph G, T N) {
    init(G, new NonNullSingletonIterator<>(N));
  }

  /**
   * Construct a depth-first enumerator across the (possibly improper) subset of nodes reachable
   * from the nodes in the given enumeration.
   *
   * @param G the graph whose nodes to enumerate
   * @param nodes the set of nodes from which to start searching
   */
  public SlowDFSDiscoverTimeIterator(Graph G, Iterator nodes) {
    if (nodes == null) {
      throw new IllegalArgumentException("null nodes");
    }
    init(G, nodes);
  }

  /**
   * Constructor SlowDFSDiscoverTimeIterator.
   *
   * @throws NullPointerException if G is null
   */
  public SlowDFSDiscoverTimeIterator(Graph G) throws NullPointerException {
    if (G == null) {
      throw new IllegalArgumentException("G is null");
    }
    init(G, G.iterator());
  }

  @Override
  protected @Nullable Iterator getPendingChildren(Object n) {
    return pendingChildren.get(n);
  }

  /** Method setPendingChildren. */
  @Override
  protected void setPendingChildren(T v, Iterator iterator) {
    pendingChildren.put(v, iterator);
  }
}