content: /**
   * 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.solr.highlight;
  
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
  import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
  import org.apache.lucene.search.highlight.Fragmenter;
  import org.apache.lucene.search.highlight.NullFragmenter;
  import org.apache.lucene.search.highlight.SimpleFragmenter;
  import org.apache.solr.common.params.DefaultSolrParams;
  import org.apache.solr.common.params.HighlightParams;
  import org.apache.solr.common.params.SolrParams;
  
  public class GapFragmenter extends HighlightingPluginBase implements SolrFragmenter
  {
    public Fragmenter getFragmenter(String fieldName, SolrParams params )
    {
      numRequests++;
      if( defaults != null ) {
        params = new DefaultSolrParams( params, defaults );
      }
      
      int fragsize = params.getFieldInt( fieldName, HighlightParams.FRAGSIZE, 100 );
      return (fragsize <= 0) ? new NullFragmenter() : new LuceneGapFragmenter(fragsize);
    }
    
  
    ///////////////////////////////////////////////////////////////////////
    //////////////////////// SolrInfoMBeans methods ///////////////////////
    ///////////////////////////////////////////////////////////////////////
  
    @Override
    public String getDescription() {
      return "GapFragmenter";
    }
  
    @Override
    public String getVersion() {
        return "$Revision: 1065312 $";
    }
  
    @Override
    public String getSourceId() {
      return "$Id: GapFragmenter.java 1065312 2011-01-30 16:08:25Z rmuir $";
    }
  
    @Override
    public String getSource() {
      return "$URL: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_3_5/solr/core/src/java/org/apache/solr/highlight/GapFragmenter.java $";
    }
  }
  
  
  /**
   * A simple modification of SimpleFragmenter which additionally creates new
   * fragments when an unusually-large position increment is encountered
   * (this behaves much better in the presence of multi-valued fields).
   */
  class LuceneGapFragmenter extends SimpleFragmenter {
    /** 
     * When a gap in term positions is observed that is at least this big, treat
     * the gap as a fragment delimiter.
     */
    public static final int INCREMENT_THRESHOLD = 50;
    protected int fragOffset = 0;
    
    private OffsetAttribute offsetAtt;
    private PositionIncrementAttribute posIncAtt;
    
    public LuceneGapFragmenter() {
    }
    
    public LuceneGapFragmenter(int fragsize) {
       super(fragsize);
    }
    
    /* (non-Javadoc)
     * @see org.apache.lucene.search.highlight.TextFragmenter#start(java.lang.String)
     */
    @Override
    public void start(String originalText, TokenStream tokenStream) {
      offsetAtt = tokenStream.getAttribute(OffsetAttribute.class);
      posIncAtt = tokenStream.getAttribute(PositionIncrementAttribute.class);
      fragOffset = 0;
    }
  
    /* (non-Javadoc)
     * @see org.apache.lucene.search.highlight.TextFragmenter#isNewFragment(org.apache.lucene.analysis.Token)
     */
    @Override
    public boolean isNewFragment() {
      int endOffset = offsetAtt.endOffset();
      boolean isNewFrag = 
        endOffset >= fragOffset + getFragmentSize() ||
        posIncAtt.getPositionIncrement() > INCREMENT_THRESHOLD;
      if(isNewFrag) {
          fragOffset = endOffset;
      }
      return isNewFrag;
    }
  }
  