/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.exoplatform.services.jcr.impl.core.query.lucene;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Searcher;
import org.apache.lucene.search.Weight;

import java.io.IOException;

/**
 * <code>AbstractWeight</code> implements base functionality for custom lucene
 * weights in jackrabbit.
 */
abstract class AbstractWeight extends Weight
{

   /**
    * The serial UID
    */
   private static final long serialVersionUID = 4670072762617933491L;

   /**
    * The searcher for this weight.
    */
   protected final Searcher searcher;

   /**
    * Creates a new <code>AbstractWeight</code> for the given
    * <code>searcher</code>.
    *
    * @param searcher the searcher instance for this weight.
    */
   public AbstractWeight(Searcher searcher)
   {
      this.searcher = searcher;
   }

   /**
    * Abstract factory method for crating a scorer instance for the
    * specified reader.
    *
    * @param reader the index reader the created scorer instance should use
    * @return the scorer instance
    * @throws IOException if an error occurs while reading from the index
    */
   protected abstract Scorer createScorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer)
      throws IOException;

   /**
    * {@inheritDoc}
    * <br>
    * Returns a {@link MultiScorer} if the passed <code>reader</code> is of
    * type {@link MultiIndexReader}.
    */
   @Override
   public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException
   {
      if (reader instanceof MultiIndexReader)
      {
         MultiIndexReader mir = (MultiIndexReader)reader;
         IndexReader[] readers = mir.getIndexReaders();
         int[] starts = new int[readers.length + 1];
         int maxDoc = 0;
         for (int i = 0; i < readers.length; i++)
         {
            starts[i] = maxDoc;
            maxDoc += readers[i].maxDoc();
         }

         starts[readers.length] = maxDoc;
         Scorer[] scorers = new Scorer[readers.length];
         for (int i = 0; i < readers.length; i++)
         {
            scorers[i] = scorer(readers[i], scoreDocsInOrder, topScorer);
         }

         return new MultiScorer(searcher.getSimilarity(), scorers, starts);
      }
      else
      {
         return createScorer(reader, scoreDocsInOrder, topScorer);
      }
   }

}