/*
* 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 Token = Lucene.Net.Analysis.Token;
using IndexReader = Lucene.Net.Index.IndexReader;
using Query = Lucene.Net.Search.Query;
namespace Lucene.Net.Highlight
{
/// {@link Scorer} implementation which scores text fragments by the number of unique query terms found.
/// This class uses the {@link QueryTermExtractor} class to process determine the query terms and
/// their boosts to be used.
///
/// mark@searcharea.co.uk
///
//TODO: provide option to boost score of fragments near beginning of document
// based on fragment.getFragNum()
public class QueryScorer : Scorer
{
internal TextFragment currentTextFragment = null;
internal System.Collections.Hashtable uniqueTermsInFragment;
internal float totalScore = 0;
internal float maxTermWeight = 0;
private System.Collections.Hashtable termsToFind;
///
/// a Lucene query (ideally rewritten using query.rewrite
/// before being passed to this class and the searcher)
///
public QueryScorer(Query query):this(QueryTermExtractor.GetTerms(query))
{
}
///
/// a Lucene query (ideally rewritten using query.rewrite
/// before being passed to this class and the searcher)
///
/// the Field name which is used to match Query terms
///
public QueryScorer(Query query, System.String fieldName):this(QueryTermExtractor.GetTerms(query, false, fieldName))
{
}
///
/// a Lucene query (ideally rewritten using query.rewrite
/// before being passed to this class and the searcher)
///
/// used to compute IDF which can be used to a) score selected fragments better
/// b) use graded highlights eg set font color intensity
///
/// the field on which Inverse Document Frequency (IDF) calculations are based
///
public QueryScorer(Query query, IndexReader reader, System.String fieldName):this(QueryTermExtractor.GetIdfWeightedTerms(query, reader, fieldName))
{
}
public QueryScorer(WeightedTerm[] weightedTerms)
{
termsToFind = new System.Collections.Hashtable();
for (int i = 0; i < weightedTerms.Length; i++)
{
WeightedTerm existingTerm = (WeightedTerm) termsToFind[weightedTerms[i].term];
if ((existingTerm == null) || (existingTerm.weight < weightedTerms[i].weight))
{
//if a term is defined more than once, always use the highest scoring weight
termsToFind[weightedTerms[i].term] = weightedTerms[i];
maxTermWeight = System.Math.Max(maxTermWeight, weightedTerms[i].GetWeight());
}
}
}
/* (non-Javadoc)
* @see Lucene.Net.Highlight.FragmentScorer#startFragment(Lucene.Net.Highlight.TextFragment)
*/
public virtual void StartFragment(TextFragment newFragment)
{
uniqueTermsInFragment = new System.Collections.Hashtable();
currentTextFragment = newFragment;
totalScore = 0;
}
/* (non-Javadoc)
* @see Lucene.Net.Highlight.FragmentScorer#scoreToken(org.apache.lucene.analysis.Token)
*/
public virtual float GetTokenScore(Token token)
{
System.String termText = token.TermText();
WeightedTerm queryTerm = (WeightedTerm) termsToFind[termText];
if (queryTerm == null)
{
//not a query term - return
return 0;
}
//found a query term - is it unique in this doc?
if (!uniqueTermsInFragment.Contains(termText))
{
totalScore += queryTerm.GetWeight();
uniqueTermsInFragment.Add(termText, termText);
}
return queryTerm.GetWeight();
}
/* (non-Javadoc)
* @see Lucene.Net.Highlight.FragmentScorer#endFragment(Lucene.Net.Highlight.TextFragment)
*/
public virtual float GetFragmentScore()
{
return totalScore;
}
/* (non-Javadoc)
* @see Lucene.Net.Highlight.FragmentScorer#allFragmentsProcessed()
*/
public virtual void AllFragmentsProcessed()
{
//this class has no special operations to perform at end of processing
}
///
/// The highest weighted term (useful for passing to GradientFormatter to set
/// top end of coloring scale.
///
public virtual float GetMaxTermWeight()
{
return maxTermWeight;
}
}
}