content: package org.apache.lucene.search.vectorhighlight;
  
  /**
   * 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.
   */
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.lucene.search.vectorhighlight.FieldPhraseList.WeightedPhraseInfo;
  
  /**
   * A simple implementation of {@link FragListBuilder}.
   */
  public class SimpleFragListBuilder implements FragListBuilder {
    
    public static final int MARGIN_DEFAULT = 6;
    public static final int MIN_FRAG_CHAR_SIZE_FACTOR = 3;
  
    final int margin;
    final int minFragCharSize;
  
    public SimpleFragListBuilder( int margin ){
      if( margin < 0 )
        throw new IllegalArgumentException( "margin(" + margin + ") is too small. It must be 0 or higher." );
  
      this.margin = margin;
      this.minFragCharSize = Math.max( 1, margin * MIN_FRAG_CHAR_SIZE_FACTOR );
    }
  
    public SimpleFragListBuilder(){
      this( MARGIN_DEFAULT );
    }
  
    public FieldFragList createFieldFragList(FieldPhraseList fieldPhraseList, int fragCharSize) {
      if( fragCharSize < minFragCharSize )
        throw new IllegalArgumentException( "fragCharSize(" + fragCharSize + ") is too small. It must be " +
            minFragCharSize + " or higher." );
  
      FieldFragList ffl = new FieldFragList( fragCharSize );
  
      List<WeightedPhraseInfo> wpil = new ArrayList<WeightedPhraseInfo>();
      Iterator<WeightedPhraseInfo> ite = fieldPhraseList.phraseList.iterator();
      WeightedPhraseInfo phraseInfo = null;
      int startOffset = 0;
      boolean taken = false;
      while( true ){
        if( !taken ){
          if( !ite.hasNext() ) break;
          phraseInfo = ite.next();
        }
        taken = false;
        if( phraseInfo == null ) break;
  
        // if the phrase violates the border of previous fragment, discard it and try next phrase
        if( phraseInfo.getStartOffset() < startOffset ) continue;
  
        wpil.clear();
        wpil.add( phraseInfo );
        int st = phraseInfo.getStartOffset() - margin < startOffset ?
            startOffset : phraseInfo.getStartOffset() - margin;
        int en = st + fragCharSize;
        if( phraseInfo.getEndOffset() > en )
          en = phraseInfo.getEndOffset();
        startOffset = en;
  
        while( true ){
          if( ite.hasNext() ){
            phraseInfo = ite.next();
            taken = true;
            if( phraseInfo == null ) break;
          }
          else
            break;
          if( phraseInfo.getEndOffset() <= en )
            wpil.add( phraseInfo );
          else
            break;
        }
        ffl.add( st, en, wpil );
      }
      return ffl;
    }
  
  }
  