SpanScorer.cs :  » Search-Engines » dotLucene » Lucene » Net » Search » Spans » C# / CSharp Open Source

/*
 * Copyright 2004 The Apache Software Foundation
 * 
 * Licensed 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 ExplanationLucene.Net.Search.Explanation;
using ScorerLucene.Net.Search.Scorer;
using SimilarityLucene.Net.Search.Similarity;
using WeightLucene.Net.Search.Weight;

namespace Lucene.Net.Search.Spans{
  
  
  class SpanScorer : Scorer
  {
    private Spans spans;
    private Weight weight;
    private byte[] norms;
    private float value_Renamed;
    
    private bool firstTime = true;
    private bool more = true;
    
    private int doc;
    private float freq;
    
    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.GetValue();
    }
    
    public override bool Next()
    {
      if (firstTime)
      {
        more = spans.Next();
        firstTime = false;
      }
      
      if (!more)
        return false;
      
      freq = 0.0f;
      doc = spans.Doc();
      
      while (more && doc == spans.Doc())
      {
        int matchLength = spans.End() - spans.Start();
        freq += GetSimilarity().SloppyFreq(matchLength);
        more = spans.Next();
      }
      
      return more || freq != 0.0f;
    }
    
    public override int Doc()
    {
      return doc;
    }
    
    public override float Score()
    {
      float raw = GetSimilarity().Tf(freq) * value_Renamed; // raw score
      return raw * Similarity.DecodeNorm(norms[doc]); // normalize
    }
    
    public override bool SkipTo(int target)
    {
      more = spans.SkipTo(target);
      
      if (!more)
        return false;
      
      freq = 0.0f;
      doc = spans.Doc();
      
      while (more && spans.Doc() == target)
      {
        freq += GetSimilarity().SloppyFreq(spans.End() - spans.Start());
        more = spans.Next();
      }
      
      return more || freq != 0.0f;
    }
    
    public override Explanation Explain(int doc)
    {
      Explanation tfExplanation = new Explanation();
      
      SkipTo(doc);
      
      float phraseFreq = (Doc() == doc)?freq:0.0f;
      tfExplanation.SetValue(GetSimilarity().Tf(phraseFreq));
      tfExplanation.SetDescription("tf(phraseFreq=" + phraseFreq + ")");
      
      return tfExplanation;
    }
  }
}