ReqOptSumScorer.cs

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/* 
 * 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;

namespace Lucene.Net.Search
{
    
    /// <summary>A Scorer for queries with a required part and an optional part.
    /// Delays skipTo() on the optional part until a score() is needed.
    /// <br/>
    /// This <c>Scorer</c> implements <see cref="DocIdSetIterator.Advance(int)" />.
    /// </summary>
    class ReqOptSumScorer:Scorer
    {
        /// <summary>The scorers passed from the constructor.
        /// These are set to null as soon as their next() or skipTo() returns false.
        /// </summary>
        private Scorer reqScorer;
        private Scorer optScorer;
        
        /// <summary>Construct a <c>ReqOptScorer</c>.</summary>
        /// <param name="reqScorer">The required scorer. This must match.
        /// </param>
        /// <param name="optScorer">The optional scorer. This is used for scoring only.
        /// </param>
        public ReqOptSumScorer(Scorer reqScorer, Scorer optScorer):base(null)
        { // No similarity used.
            this.reqScorer = reqScorer;
            this.optScorer = optScorer;
        }
        
        public override int NextDoc()
        {
            return reqScorer.NextDoc();
        }
        
        public override int Advance(int target)
        {
            return reqScorer.Advance(target);
        }
        
        public override int DocID()
        {
            return reqScorer.DocID();
        }
        
        /// <summary>Returns the score of the current document matching the query.
        /// Initially invalid, until <see cref="NextDoc()" /> is called the first time.
        /// </summary>
        /// <returns> The score of the required scorer, eventually increased by the score
        /// of the optional scorer when it also matches the current document.
        /// </returns>
        public override float Score()
        {
            int curDoc = reqScorer.DocID();
            float reqScore = reqScorer.Score();
            if (optScorer == null)
            {
                return reqScore;
            }
            
            int optScorerDoc = optScorer.DocID();
            if (optScorerDoc < curDoc && (optScorerDoc = optScorer.Advance(curDoc)) == NO_MORE_DOCS)
            {
                optScorer = null;
                return reqScore;
            }
            
            return optScorerDoc == curDoc?reqScore + optScorer.Score():reqScore;
        }
    }
}