Implementation of solr custom function class which extends ValueSource

AvailabilityValueSource.java

package com.solrExample.solr4;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Logger;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.util.TokenFilterFactory;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.AtomicReaderContext;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.queries.function.docvalues.IntDocValues;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopScoreDocCollector;
import org.apache.lucene.util.Version;
import org.apache.solr.common.SolrException;


/**
 * 
 * Created May 10, 2016 11:18:12 AM
 * 
 * @author chaitanya
 */
public class AvailabilityValueSource extends ValueSource {

  protected String startDateTime;
  protected String endDateTime;
  protected String fieldName;

  public AvailabilityValueSource(String startDateTime, String endDateTime,
      String fieldName) {
    if (startDateTime == null || endDateTime == null || fieldName == null) {
      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
          "One or more inputs missing for petAvail function");
    }
    this.startDateTime = startDateTime;
    this.endDateTime = endDateTime;
    this.fieldName = fieldName;
    
  }

  @Override
  public String description() {
    return "";
  }

  @Override
  public boolean equals(Object otherObj) {
    if (otherObj == null || !(otherObj instanceof AvailabilityValueSource))
      return false;
    AvailabilityValueSource other = (AvailabilityValueSource) otherObj;
    return this.startDateTime.equals(other.startDateTime)
        && this.endDateTime.equals(other.endDateTime)
        && this.fieldName.equals(other.fieldName);
  }

  protected String name() {
    return "AvailabilityValueSource";
  }

  @Override
  public FunctionValues getValues(Map context, AtomicReaderContext reader)
      throws IOException {
    final Map<String, String> availableUsers =
        (Map<String, String>) context.get("availableUsers");
    return new IntDocValues(this) {

      @Override
      public int intVal(int doc) {
        if (availableUsers != null) {
          String isAvailable = availableUsers.get(String.valueOf(doc));
          // if current doc is found in availableUsers map then his availability
          // matches return 1 which can be used for sort
          if (isAvailable != null) {
            return 1;
          }
        }
        return 0;
      }
    };
  }

  @Override
  public int hashCode() {
    return (int) startDateTime.hashCode() + endDateTime.hashCode() + fieldName.hashCode();
  }

  @Override
  public void createWeight(Map context, IndexSearcher searcher) {
    Map<String, String> availableUsers = new HashMap<String, String>();
    try {
      TokenFilterFactory[] factory = new TokenFilterFactory[0];
      Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_41);
      // build availability query string using startDateTime, endDateTime and availabilityType
      
      //Here we are taking the start date and end date and building the query based
      //on how it is in the solr, eg: +availble:0506 +available:0507
      //Here available is the solr filed name
      String parsedDateTokens =
          SplitDateIntoTokensParser.getAvailabilitySlots(startDateTime, endDateTime,
              availabilityType);    
      Query q =
          new QueryParser(Version.LUCENE_41, fieldName, analyzer).parse(parsedDateTokens);
      TopScoreDocCollector collector =
          TopScoreDocCollector.create(searcher.getIndexReader().numDocs(), true);
      searcher.search(q, collector);
      ScoreDoc[] hits = collector.topDocs().scoreDocs;
      // If availaiblity matches add those docs to map with value 1
      for (int i = 0; i < hits.length; ++i) {
        int docId = hits[i].doc;
        Document doc = searcher.doc(docId);
        availableProviders.put(String.valueOf(docId), String.valueOf(1));
      }
    } catch (Exception e) {
      logger.severe("EXception while creating availability map" + e);
    }
    context.put("availableUsers", availableUsers);
  }
}