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 abstract implementation of {@link FragListBuilder}.
*/
public abstract class BaseFragListBuilder 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 BaseFragListBuilder( 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 BaseFragListBuilder(){
this( MARGIN_DEFAULT );
}
protected FieldFragList createFieldFragList( FieldPhraseList fieldPhraseList, FieldFragList fieldFragList, int fragCharSize ){
if( fragCharSize < minFragCharSize )
throw new IllegalArgumentException( "fragCharSize(" + fragCharSize + ") is too small. It must be " + minFragCharSize + " or higher." );
List<WeightedPhraseInfo> wpil = new ArrayList<WeightedPhraseInfo>();
Iterator<WeightedPhraseInfo> ite = fieldPhraseList.getPhraseList().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 firstOffset = phraseInfo.getStartOffset();
int st = phraseInfo.getStartOffset() - margin < startOffset ?
startOffset : phraseInfo.getStartOffset() - margin;
int en = st + fragCharSize;
if( phraseInfo.getEndOffset() > en )
en = phraseInfo.getEndOffset();
int lastEndOffset = phraseInfo.getEndOffset();
while( true ){
if( ite.hasNext() ){
phraseInfo = ite.next();
taken = true;
if( phraseInfo == null ) break;
}
else
break;
if( phraseInfo.getEndOffset() <= en ){
wpil.add( phraseInfo );
lastEndOffset = phraseInfo.getEndOffset();
}
else
break;
}
int matchLen = lastEndOffset - firstOffset;
//now recalculate the start and end position to "center" the result
int newMargin = (fragCharSize-matchLen)/2;
st = firstOffset - newMargin;
if(st<startOffset){
st = startOffset;
}
en = st+fragCharSize;
startOffset = en;
fieldFragList.add( st, en, wpil );
}
return fieldFragList;
}
}