SpanWeight.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 System.Collections.Generic;
using Lucene.Net.Index;
using IndexReader = Lucene.Net.Index.IndexReader;
using Lucene.Net.Search;
using IDFExplanation = Lucene.Net.Search.Explanation.IDFExplanation;

namespace Lucene.Net.Search.Spans
{
    
    /// <summary> Expert-only.  Public for use by other weight implementations</summary>
    [Serializable]
    public class SpanWeight:Weight
    {
        protected internal Similarity similarity;
        protected internal float value_Renamed;
        protected internal float idf;
        protected internal float queryNorm;
        protected internal float queryWeight;

        protected internal ISet<Term> terms;
        protected internal SpanQuery internalQuery;
        private IDFExplanation idfExp;
        
        public SpanWeight(SpanQuery query, Searcher searcher)
        {
            this.similarity = query.GetSimilarity(searcher);
            this.internalQuery = query;

            terms = Lucene.Net.Support.Compatibility.SetFactory.CreateHashSet<Term>();
            query.ExtractTerms(terms);

            idfExp = similarity.IdfExplain(terms, searcher);
            idf = idfExp.Idf;
        }

        public override Query Query
        {
            get { return internalQuery; }
        }

        public override float Value
        {
            get { return value_Renamed; }
        }

        public override float GetSumOfSquaredWeights()
        {
            queryWeight = idf*internalQuery.Boost; // compute query weight
            return queryWeight*queryWeight; // square it
        }

        public override void  Normalize(float queryNorm)
        {
            this.queryNorm = queryNorm;
            queryWeight *= queryNorm; // normalize query weight
            value_Renamed = queryWeight * idf; // idf for document
        }
        
        public override Scorer Scorer(IndexReader reader, bool scoreDocsInOrder, bool topScorer)
        {
            return new SpanScorer(internalQuery.GetSpans(reader), this, similarity, reader.Norms(internalQuery.Field));
        }
        
        public override Explanation Explain(IndexReader reader, int doc)
        {
            
            ComplexExplanation result = new ComplexExplanation();
            result.Description = "weight(" + Query + " in " + doc + "), product of:";
            System.String field = ((SpanQuery) Query).Field;
            
            Explanation idfExpl = new Explanation(idf, "idf(" + field + ": " + idfExp.Explain() + ")");
            
            // explain query weight
            Explanation queryExpl = new Explanation();
            queryExpl.Description = "queryWeight(" + Query + "), product of:";
            
            Explanation boostExpl = new Explanation(Query.Boost, "boost");
            if (Query.Boost != 1.0f)
                queryExpl.AddDetail(boostExpl);
            queryExpl.AddDetail(idfExpl);
            
            Explanation queryNormExpl = new Explanation(queryNorm, "queryNorm");
            queryExpl.AddDetail(queryNormExpl);
            
            queryExpl.Value = boostExpl.Value * idfExpl.Value * queryNormExpl.Value;
            
            result.AddDetail(queryExpl);
            
            // explain field weight
            ComplexExplanation fieldExpl = new ComplexExplanation();
            fieldExpl.Description = "fieldWeight(" + field + ":" + internalQuery.ToString(field) + " in " + doc + "), product of:";
            
            Explanation tfExpl = ((SpanScorer)Scorer(reader, true, false)).Explain(doc);
            fieldExpl.AddDetail(tfExpl);
            fieldExpl.AddDetail(idfExpl);
            
            Explanation fieldNormExpl = new Explanation();
            byte[] fieldNorms = reader.Norms(field);
            float fieldNorm = fieldNorms != null?Similarity.DecodeNorm(fieldNorms[doc]):1.0f;
            fieldNormExpl.Value = fieldNorm;
            fieldNormExpl.Description = "fieldNorm(field=" + field + ", doc=" + doc + ")";
            fieldExpl.AddDetail(fieldNormExpl);
            
            fieldExpl.Match = tfExpl.IsMatch;
            fieldExpl.Value = tfExpl.Value * idfExpl.Value * fieldNormExpl.Value;
            
            result.AddDetail(fieldExpl);
            System.Boolean? tempAux = fieldExpl.Match;
            result.Match = tempAux;
            
            // combine them
            result.Value = queryExpl.Value * fieldExpl.Value;
            
            if (queryExpl.Value == 1.0f)
                return fieldExpl;
            
            return result;
        }
    }
}