/*
 * 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.lucene.queries.function.valuesource;

import java.io.IOException;
import java.util.Map;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.ReaderUtil;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.queries.function.ValueSource;

/**
 * Returns the value of {@link IndexReader#numDocs()} for every document. This is the number of
 * documents excluding deletions.
 */
public class NumDocsValueSource extends ValueSource {
  public String name() {
    return "numdocs";
  }

  @Override
  public String description() {
    return name() + "()";
  }

  @Override
  public FunctionValues getValues(Map<Object, Object> context, LeafReaderContext readerContext)
      throws IOException {
    // Searcher has no numdocs so we must use the reader instead
    return new DocFreqValueSource.ConstIntDocValues(
        ReaderUtil.getTopLevelContext(readerContext).reader().numDocs(), this);
  }

  @Override
  public boolean equals(Object o) {
    return this.getClass() == o.getClass();
  }

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