﻿/*
 * 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.
 */
using System.Collections;
using Lucene.Net.Index;

namespace Lucene.Net.Queries.Function.ValueSources
{
    /// <summary>
    /// Returns the value of <seealso cref="IndexReader#numDocs()"/>
    /// for every document. This is the number of documents
    /// excluding deletions.
    /// </summary>
    public class NumDocsValueSource : ValueSource
    {
        public virtual string Name
        {
            get { return "numdocs"; }
        }

        public override string Description
        {
            get { return Name + "()"; }
        }

        public override FunctionValues GetValues(IDictionary context, AtomicReaderContext readerContext)
        {
            // Searcher has no numdocs so we must use the reader instead
            return new ConstIntDocValues(ReaderUtil.GetTopLevelContext(readerContext).Reader.NumDocs, this);
        }

        public override bool Equals(object o)
        {
            return this.GetType() == o.GetType();
        }

        public override int GetHashCode()
        {
            return this.GetType().GetHashCode();
        }
    }
}