// 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;

 /**

  * Looks at the current node and attempts to rewrite Indri-style

  * operators in the Galago format.  It can rewrite three types of expressions:

  * <ul>

  *  <li>#<i>n</i> changes to #od:</i>n</i></li>

  *  <li>#od<i>n</i> changes to #od:<i>n</i></li>

  *  <li>#uw<i>n</i> changes to #uw:<i>n</i></li>

  * </ul>

  * @author trevor

  */

 public class IndriWindowCompatibilityTraversal implements Traversal {

     public Node afterNode(Node original) {

         String operator = original.getOperator();

         ArrayList<Node> children = original.getInternalNodes();

         if (operator.length() == 0) {

             return original;

         }

         if (Character.isDigit(operator.codePointAt(0))) {

             // this is a #n node, which is an ordered window node

             return new Node("od", operator, children, original.getPosition());

         } else if (operator.startsWith("od") &&

                 operator.length() > 2 &&

                 Character.isDigit(operator.codePointAt(2))) {

             // this is a #od3() node

             return new Node("od", operator.substring(2),

                     children, original.getPosition());

         } else if (operator.startsWith("uw") &&

                 operator.length() > 2 &&

                 Character.isDigit(operator.codePointAt(2))) {

             // this is a #uw3 node

             return new Node("uw", operator.substring(2),

                     children, original.getPosition());

         }

         return original;

     }

     public void beforeNode(Node object) throws Exception {

         // does nothing

     }

 }