SpanScorer.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;

using Explanation = Lucene.Net.Search.Explanation;
using Scorer = Lucene.Net.Search.Scorer;
using Similarity = Lucene.Net.Search.Similarity;
using Weight = Lucene.Net.Search.Weight;

namespace Lucene.Net.Search.Spans
{
    /// <summary> Public for extension only.</summary>
    public class SpanScorer:Scorer
    {
        protected internal Spans spans;
        protected internal Weight weight;
        protected internal byte[] norms;
        protected internal float value_Renamed;
        
        protected internal bool more = true;
        
        protected internal int doc;
        protected internal float freq;
        
        protected internal SpanScorer(Spans spans, Weight weight, Similarity similarity, byte[] norms):base(similarity)
        {
            this.spans = spans;
            this.norms = norms;
            this.weight = weight;
            this.value_Renamed = weight.Value;
            if (this.spans.Next())
            {
                doc = - 1;
            }
            else
            {
                doc = NO_MORE_DOCS;
                more = false;
            }
        }
        
        public override int NextDoc()
        {
            if (!SetFreqCurrentDoc())
            {
                doc = NO_MORE_DOCS;
            }
            return doc;
        }
        
        public override int Advance(int target)
        {
            if (!more)
            {
                return doc = NO_MORE_DOCS;
            }
            if (spans.Doc() < target)
            {
                // setFreqCurrentDoc() leaves spans.doc() ahead
                more = spans.SkipTo(target);
            }
            if (!SetFreqCurrentDoc())
            {
                doc = NO_MORE_DOCS;
            }
            return doc;
        }
        
        public /*protected internal*/ virtual bool SetFreqCurrentDoc()
        {
            if (!more)
            {
                return false;
            }
            doc = spans.Doc();
            freq = 0.0f;
            do 
            {
                int matchLength = spans.End() - spans.Start();
                freq += Similarity.SloppyFreq(matchLength);
                more = spans.Next();
            }
            while (more && (doc == spans.Doc()));
            return true;
        }
        
        public override int DocID()
        {
            return doc;
        }
        
        public override float Score()
        {
            float raw = Similarity.Tf(freq) * value_Renamed; // raw score
            return norms == null?raw:raw * Similarity.DecodeNorm(norms[doc]); // normalize
        }
        
        /// <summary>
        /// This method is no longer an official member of <see cref="Scorer"/>
        /// but it is needed by SpanWeight to build an explanation.
        /// </summary>
        protected internal virtual Explanation Explain(int doc)
        {
            Explanation tfExplanation = new Explanation();
            
            int expDoc = Advance(doc);
            
            float phraseFreq = (expDoc == doc)?freq:0.0f;
            tfExplanation.Value = Similarity.Tf(phraseFreq);
            tfExplanation.Description = "tf(phraseFreq=" + phraseFreq + ")";
            
            return tfExplanation;
        }
    }
}