/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.elasticsearch.common.lucene.search;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Collector;
import org.apache.lucene.search.FilterLeafCollector;
import org.apache.lucene.search.LeafCollector;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Weight;
import org.apache.lucene.util.Bits;
import org.elasticsearch.common.lucene.Lucene;

import java.io.IOException;

public class FilteredCollector implements Collector {

    private final Collector collector;
    private final Weight filter;

    public FilteredCollector(Collector collector, Weight filter) {
        this.collector = collector;
        this.filter = filter;
    }

    @Override
    public LeafCollector getLeafCollector(LeafReaderContext context) throws IOException {
        final Scorer filterScorer = filter.scorer(context);
        final LeafCollector in = collector.getLeafCollector(context);
        final Bits bits = Lucene.asSequentialAccessBits(context.reader().maxDoc(), filterScorer);

        return new FilterLeafCollector(in) {
            @Override
            public void collect(int doc) throws IOException {
                if (bits.get(doc)) {
                    in.collect(doc);
                }
            }
        };
    }

    @Override
    public boolean needsScores() {
        return collector.needsScores();
    }
}