package org.apache.lucene.analysis.hunspell;
/**
* 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.io.IOException;
import java.util.List;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.hunspell.HunspellStemmer.Stem;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
/**
* TokenFilter that uses hunspell affix rules and words to stem tokens. Since hunspell supports a word having multiple
* stems, this filter can emit multiple tokens for each consumed token
*/
public final class HunspellStemFilter extends TokenFilter {
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final PositionIncrementAttribute posIncAtt = addAttribute(PositionIncrementAttribute.class);
private final HunspellStemmer stemmer;
private List<Stem> buffer;
private State savedState;
private final boolean dedup;
/**
* Creates a new HunspellStemFilter that will stem tokens from the given TokenStream using affix rules in the provided
* HunspellDictionary
*
* @param input TokenStream whose tokens will be stemmed
* @param dictionary HunspellDictionary containing the affix rules and words that will be used to stem the tokens
*/
public HunspellStemFilter(TokenStream input, HunspellDictionary dictionary) {
this(input, dictionary, true);
}
/**
* Creates a new HunspellStemFilter that will stem tokens from the given TokenStream using affix rules in the provided
* HunspellDictionary
*
* @param input TokenStream whose tokens will be stemmed
* @param dictionary HunspellDictionary containing the affix rules and words that will be used to stem the tokens
* @param dedup true if only unique terms should be output.
*/
public HunspellStemFilter(TokenStream input, HunspellDictionary dictionary, boolean dedup) {
super(input);
this.dedup = dedup;
this.stemmer = new HunspellStemmer(dictionary);
}
/**
* {@inheritDoc}
*/
@Override
public boolean incrementToken() throws IOException {
if (buffer != null && !buffer.isEmpty()) {
Stem nextStem = buffer.remove(0);
restoreState(savedState);
posIncAtt.setPositionIncrement(0);
termAtt.copyBuffer(nextStem.getStem(), 0, nextStem.getStemLength());
termAtt.setLength(nextStem.getStemLength());
return true;
}
if (!input.incrementToken()) {
return false;
}
buffer = dedup ? stemmer.uniqueStems(termAtt.buffer(), termAtt.length()) : stemmer.stem(termAtt.buffer(), termAtt.length());
if (buffer.isEmpty()) { // we do not know this word, return it unchanged
return true;
}
Stem stem = buffer.remove(0);
termAtt.copyBuffer(stem.getStem(), 0, stem.getStemLength());
termAtt.setLength(stem.getStemLength());
if (!buffer.isEmpty()) {
savedState = captureState();
}
return true;
}
/**
* {@inheritDoc}
*/
@Override
public void reset() throws IOException {
super.reset();
buffer = null;
}
}