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

 package org.galagosearch.core.retrieval.structured;

 import java.io.IOException;

 import java.util.ArrayList;

 import java.util.PriorityQueue;

 import org.galagosearch.core.util.ExtentArray;

 /**

  * This class is meant to be a base class for many kinds of

  * iterators that require at least one of their children to be

  * present in the document for a match to happen.  This class

  * will call loadExtents once for each document that has a

  * match on any child iterator.

  * 

  * @author trevor

  */

 public abstract class ExtentDisjunctionIterator extends ExtentIterator {

     protected ExtentIterator[] original;

     protected PriorityQueue<ExtentIterator> iterators;

     protected int document;

     protected ExtentArray extents;

     public ExtentDisjunctionIterator(ExtentIterator[] iterators) {

         this.original = iterators;

         this.iterators = new PriorityQueue<ExtentIterator>(iterators.length);

         this.extents = new ExtentArray();

         this.document = 0;

         for (ExtentIterator iterator : original) {

             if (!iterator.isDone()) {

                 this.iterators.add(iterator);

             }

         }

     }

     public abstract void loadExtents();

     public void nextDocument() throws IOException {

         // find all iterators on the current document and move them forward

         while (iterators.size() > 0 && iterators.peek().document() == document) {

             ExtentIterator iter = iterators.poll();

             iter.nextDocument();

             if (!iter.isDone()) {

                 iterators.offer(iter);

             }

         }

         if (!isDone()) {

             extents.reset();

             loadExtents();

         }

     }

     public boolean isDone() {

         return iterators.size() == 0;

     }

     public ExtentArray extents() {

         return extents;

     }

     public int document() {

         return document;

     }

     public int count() {

         return extents.getPosition();

     }

     public void reset() throws IOException {

         iterators.clear();

         for (ExtentIterator iterator : original) {

             iterator.reset();

             if (!iterator.isDone()) {

                 iterators.add(iterator);

             }

         }

         loadExtents();

     }

 }