ReqExclScorer.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 subscorer
    /// and an excluding (prohibited) sub DocIdSetIterator.
    /// <br/>
    /// This <c>Scorer</c> implements <see cref="DocIdSetIterator.Advance(int)" />,
    /// and it uses the skipTo() on the given scorers.
    /// </summary>
    class ReqExclScorer:Scorer
    {
        private Scorer reqScorer;
        private DocIdSetIterator exclDisi;
        private int doc = - 1;
        
        /// <summary>Construct a <c>ReqExclScorer</c>.</summary>
        /// <param name="reqScorer">The scorer that must match, except where
        /// </param>
        /// <param name="exclDisi">indicates exclusion.
        /// </param>
        public ReqExclScorer(Scorer reqScorer, DocIdSetIterator exclDisi):base(null)
        { // No similarity used.
            this.reqScorer = reqScorer;
            this.exclDisi = exclDisi;
        }
        
        public override int NextDoc()
        {
            if (reqScorer == null)
            {
                return doc;
            }
            doc = reqScorer.NextDoc();
            if (doc == NO_MORE_DOCS)
            {
                reqScorer = null; // exhausted, nothing left
                return doc;
            }
            if (exclDisi == null)
            {
                return doc;
            }
            return doc = ToNonExcluded();
        }
        
        /// <summary>Advance to non excluded doc.
        /// <br/>On entry:
        /// <list type="bullet">
        /// <item>reqScorer != null, </item>
        /// <item>exclScorer != null, </item>
        /// <item>reqScorer was advanced once via next() or skipTo() 
        /// and reqScorer.doc() may still be excluded.</item>
        /// </list>
        /// Advances reqScorer a non excluded required doc, if any.
        /// </summary>
        /// <returns> true iff there is a non excluded required doc.
        /// </returns>
        private int ToNonExcluded()
        {
            int exclDoc = exclDisi.DocID();
            int reqDoc = reqScorer.DocID(); // may be excluded
            do 
            {
                if (reqDoc < exclDoc)
                {
                    return reqDoc; // reqScorer advanced to before exclScorer, ie. not excluded
                }
                else if (reqDoc > exclDoc)
                {
                    exclDoc = exclDisi.Advance(reqDoc);
                    if (exclDoc == NO_MORE_DOCS)
                    {
                        exclDisi = null; // exhausted, no more exclusions
                        return reqDoc;
                    }
                    if (exclDoc > reqDoc)
                    {
                        return reqDoc; // not excluded
                    }
                }
            }
            while ((reqDoc = reqScorer.NextDoc()) != NO_MORE_DOCS);
            reqScorer = null; // exhausted, nothing left
            return NO_MORE_DOCS;
        }
        
        public override int DocID()
        {
            return doc;
        }
        
        /// <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.
        /// </returns>
        public override float Score()
        {
            return reqScorer.Score(); // reqScorer may be null when next() or skipTo() already return false
        }
        
        public override int Advance(int target)
        {
            if (reqScorer == null)
            {
                return doc = NO_MORE_DOCS;
            }
            if (exclDisi == null)
            {
                return doc = reqScorer.Advance(target);
            }
            if (reqScorer.Advance(target) == NO_MORE_DOCS)
            {
                reqScorer = null;
                return doc = NO_MORE_DOCS;
            }
            return doc = ToNonExcluded();
        }
    }
}