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

 package org.galagosearch.core.retrieval.traversal;

 import java.io.IOException;

 import java.util.ArrayList;

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

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

 /**

  *

  * @author trevor

  */

 public class WeightConversionTraversal implements Traversal {

     public void beforeNode(Node object) throws Exception {

         // do nothing

     }

     public String getWeight(Node weightNode) {

         if (weightNode.getOperator().equals("inside")) {

             if (weightNode.getInternalNodes().size() != 2) {

                 return "1";

             } else {

                 Node inner = weightNode.getInternalNodes().get(0);

                 Node outer = weightNode.getInternalNodes().get(1);

                 return inner.getDefaultParameter() + "." + outer.getDefaultParameter();

             }

         } else {

             return weightNode.getDefaultParameter();

         }

     }

     public Node afterNode(Node node) throws Exception {

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

         if (node.getOperator().equals("weight")) {

             // first, verify that the appropriate children are weights

             if (children.size() % 2 == 1) {

                 throw new IOException("A weighted node cannot have an odd number of internal nodes: " +

                         node.getInternalNodes().size());

             }

             // now, reassemble everything:

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

             for (int i = 0; i < children.size(); i += 2) {

                 Node weightNode = children.get(i);

                 Node childNode = children.get(i+1);

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

                 newChild.add(childNode);

                 Node scaledNode = new Node("scale", getWeight(weightNode), newChild);

                 newChildren.add(scaledNode);

             }

             return new Node("combine", newChildren);

         } else {

             return node;

         }

     }

 }