package edu.neu.ccs.demeter.dj;

import java.util.*;

/**
 * Thrown when creating an object graph slice from a traversal T and
 * an object graph whose root is not an instance of a class in the
 * start set of T.
 */
public class TraversalSourceException extends RuntimeException {
  TraversalSourceException(Object root, Traversal t) {
    super("Object graph root is " + root.getClass()
	  + ", traversal sources are " + getStartNodes(t));
  }
  static List getStartNodes(Traversal t) {
    // I sure wish this were Scheme:
    // (map get-node (get-start-node-sets this))
    List nodes = new ArrayList();
    for (Iterator it = t.getStartSet().iterator(); it.hasNext();)
      nodes.add(((Traversal.NodeSet) it.next()).getNode());
    return nodes;
  }
}