/*
 * 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.AtomicReaderContext;
import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.Filter;
import org.apache.lucene.util.Bits;

import java.io.IOException;

/**
 * A filter that matches no docs.
 */
public class MatchNoDocsFilter extends Filter {

    @Override
    public DocIdSet getDocIdSet(AtomicReaderContext context, Bits acceptDocs) throws IOException {
        return null;
    }

    @Override
    public int hashCode() {
        return this.getClass().hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;

        if (obj == null) {
            return false;
        }

        if (obj.getClass() == this.getClass()) {
            return true;
        }

        return false;
    }

    @Override
    public String toString() {
        return "MatchNoDocsFilter";
    }
}
