/*
 * 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.
 */
package org.apache.lucene.search.highlight;

import java.util.HashMap;
import java.util.HashSet;

import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;

Scorer implementation which scores text fragments by the number of unique query terms found. This class uses the QueryTermExtractor class to process determine the query terms and their boosts to be used. /**
 * {@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.
 */
// TODO: provide option to boost score of fragments near beginning of document
// based on fragment.getFragNum()
public class QueryTermScorer implements Scorer {
  
  TextFragment currentTextFragment = null;
  HashSet<String> uniqueTermsInFragment;

  float totalScore = 0;
  float maxTermWeight = 0;
  private HashMap<String,WeightedTerm> termsToFind;

  private CharTermAttribute termAtt;

  
Params:
query – a Lucene query (ideally rewritten using query.rewrite before
       being passed to this class and the searcher)/**
   * 
   * @param query a Lucene query (ideally rewritten using query.rewrite before
   *        being passed to this class and the searcher)
   */
  public QueryTermScorer(Query query) {
    this(QueryTermExtractor.getTerms(query));
  }

  
Params:
query – a Lucene query (ideally rewritten using query.rewrite before
       being passed to this class and the searcher)
fieldName – the Field name which is used to match Query terms/**
   * 
   * @param query a Lucene query (ideally rewritten using query.rewrite before
   *        being passed to this class and the searcher)
   * @param fieldName the Field name which is used to match Query terms
   */
  public QueryTermScorer(Query query, String fieldName) {
    this(QueryTermExtractor.getTerms(query, false, fieldName));
  }

  
Params:
query – a Lucene query (ideally rewritten using query.rewrite before
       being passed to this class and the searcher)
reader – used to compute IDF which can be used to a) score selected
       fragments better b) use graded highlights eg set font color
       intensity
fieldName – the field on which Inverse Document Frequency (IDF)
       calculations are based/**
   * 
   * @param query a Lucene query (ideally rewritten using query.rewrite before
   *        being passed to this class and the searcher)
   * @param reader used to compute IDF which can be used to a) score selected
   *        fragments better b) use graded highlights eg set font color
   *        intensity
   * @param fieldName the field on which Inverse Document Frequency (IDF)
   *        calculations are based
   */
  public QueryTermScorer(Query query, IndexReader reader, String fieldName) {
    this(QueryTermExtractor.getIdfWeightedTerms(query, reader, fieldName));
  }

  public QueryTermScorer(WeightedTerm[] weightedTerms) {
    termsToFind = new HashMap<>();
    for (int i = 0; i < weightedTerms.length; i++) {
      WeightedTerm existingTerm = termsToFind
          .get(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.put(weightedTerms[i].term, weightedTerms[i]);
        maxTermWeight = Math.max(maxTermWeight, weightedTerms[i].getWeight());
      }
    }
  }

  /* (non-Javadoc)
   * @see org.apache.lucene.search.highlight.Scorer#init(org.apache.lucene.analysis.TokenStream)
   */
  @Override
  public TokenStream init(TokenStream tokenStream) {
    termAtt = tokenStream.addAttribute(CharTermAttribute.class);
    return null;
  }

  /*
   * (non-Javadoc)
   * 
   * @see
   * org.apache.lucene.search.highlight.FragmentScorer#startFragment(org.apache
   * .lucene.search.highlight.TextFragment)
   */
  @Override
  public void startFragment(TextFragment newFragment) {
    uniqueTermsInFragment = new HashSet<>();
    currentTextFragment = newFragment;
    totalScore = 0;

  }


  /* (non-Javadoc)
   * @see org.apache.lucene.search.highlight.Scorer#getTokenScore()
   */
  @Override
  public float getTokenScore() {
    String termText = termAtt.toString();

    WeightedTerm queryTerm = termsToFind.get(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);
    }
    return queryTerm.getWeight();
  }


  /* (non-Javadoc)
   * @see org.apache.lucene.search.highlight.Scorer#getFragmentScore()
   */
  @Override
  public float getFragmentScore() {
    return totalScore;
  }

  /*
   * (non-Javadoc)
   * 
   * @see
   * org.apache.lucene.search.highlight.FragmentScorer#allFragmentsProcessed()
   */
  public void allFragmentsProcessed() {
    // this class has no special operations to perform at end of processing
  }

  
Returns:
The highest weighted term (useful for passing to GradientFormatter
        to set top end of coloring scale./**
   * 
   * @return The highest weighted term (useful for passing to GradientFormatter
   *         to set top end of coloring scale.
   */
  public float getMaxTermWeight() {
    return maxTermWeight;
  }
}