/*
 * 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.apache.jackrabbit.core.query.lucene;

import java.io.IOException;

import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.index.IndexReader;
import org.apache.jackrabbit.core.id.NodeId;

/**
 * Wraps a lucene query result and adds a close method that allows to release
 * resources after a query has been executed and the results have been read
 * completely.
 */
public class LuceneQueryHits implements QueryHits {

    /**
     * The IndexReader in use by the lucene hits.
     */
    private final IndexReader reader;

    /**
     * The scorer for the query.
     */
    private final Scorer scorer;

    public LuceneQueryHits(IndexReader reader,
                           IndexSearcher searcher,
                           Query query)
            throws IOException {
        this.reader = reader;
        // We rely on Scorer#nextDoc() and Scorer#advance(int) so enable
        // scoreDocsInOrder
        this.scorer = query.createWeight(searcher).scorer(reader, true, false);
    }

    /**
     * {@inheritDoc}
     */
    public ScoreNode nextScoreNode() throws IOException {
        if (scorer == null) {
            return null;
        }
        int doc = scorer.nextDoc();
        if (doc == DocIdSetIterator.NO_MORE_DOCS) {
            return null;
        }
        NodeId id = new NodeId(reader.document(
                doc, FieldSelectors.UUID).get(FieldNames.UUID));
        return new ScoreNode(id, scorer.score(), doc);
    }

    /**
     * {@inheritDoc}
     */
    public void close() throws IOException {
        if (scorer != null) {
            // make sure scorer frees resources
            scorer.advance(Integer.MAX_VALUE);
        }
    }

    /**
     * @return always -1.
     */
    public int getSize() {
        return -1;
    }

    /**
     * {@inheritDoc}
     */
    public void skip(int n) throws IOException {
        while (n-- > 0) {
            if (nextScoreNode() == null) {
                return;
            }
        }
    }
}