// BSD License (http://www.galagosearch.org/license)

 package org.galagosearch.core.retrieval.traversal;

 import java.util.ArrayList;

 import org.galagosearch.core.retrieval.query.Node;

 import org.galagosearch.core.retrieval.query.Traversal;

 /**

  * Adds a #combine at the top level of the query.

  * @author trevor

  */

 public class AddCombineTraversal implements Traversal {

     int levels = 0;

     public void beforeNode(Node object) throws Exception {

         levels++;

     }

     public Node afterNode(Node original) throws Exception {

         levels--;

         if (levels > 0) {

             return original;

         } else if (!original.getOperator().equals("combine")) {

             // Only add a combine if the top level operator is not already a combine

             ArrayList<Node> originalChild = new ArrayList<Node>();

             originalChild.add(original);

             return new Node("combine", originalChild);

         } else {

             return original;

         }

     }

 }