package org.apache.commons.graph;

/* ====================================================================
 * The Apache Software License, Version 1.1
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 * reserved.
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 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
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import org.apache.commons.graph.visitor.Visitor;

/**
 * Class takes a visitor "piggy-backed" and applies it to all nodes
 * and edges.  The traversal order implemented by children of this
 * class may be Depth-first or Breadth-first search, e.g..
 *
 * This relates to the "Strategy" design pattern.
 *
 * @version $Id: TraversalOrder.java,v 1.4 2002/01/16 20:38:28 jvanzyl Exp $
 * @author  <A HREF="http://www.inf.fu-berlin.de/~dahm">M. Dahm</A>
 * @see DFS
 * @see BFS
 * @see Sequential 
*/
public abstract class TraversalOrder 
{
  protected Visitor visitor;
  protected Graph   graph;
  protected boolean stopped;
  protected boolean traverse_complete_graph;

  /**
   * Depth first search algorithm.
   *
   * @param v visitor object to apply when discovering and finishing a vertex or edge
   * @param traverse_all traverse the complete graph or stop after finishing all nodes reachable
   * from the start
   */
  public TraversalOrder(Visitor v, boolean traverse_all) {
    visitor = v;
    traverse_complete_graph = traverse_all;
  }

  public TraversalOrder(Visitor v) {
    this(v, true);
  }

  /**
   * Start traversal.
   *
   * @param g graph to traverse
   * @param start vertex to start at (or null, starts at some vertex then)
   * @param all_vertices visit all vertices or just those reache from start
   */
  public abstract void start(Graph g, Vertex start);

  /** May be called to stop traversal, e.g. if a searched node has been found.
   */
  public void stop() {
    stopped = true;
  }

  /**
   * Depth first search algorithm starting at some vertex.
   *
   * @param g graph to traverse
   */
  public void start(Graph g) {
    start(g, null);
  }
}