/*
 * 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.lucene.analysis.el;


import java.io.IOException;

import org.apache.lucene.analysis.miscellaneous.SetKeywordMarkerFilter; // for javadoc
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;

A TokenFilter that applies GreekStemmer to stem Greek words. 
 To prevent terms from being stemmed use an instance of SetKeywordMarkerFilter or a custom TokenFilter that sets the KeywordAttribute before this TokenStream. 
 NOTE: Input is expected to be casefolded for Greek (including folding of final sigma to sigma), and with diacritics removed. This can be achieved by using either GreekLowerCaseFilter or ICUFoldingFilter before GreekStemFilter. 
@lucene.experimental
/**
 * A {@link TokenFilter} that applies {@link GreekStemmer} to stem Greek
 * words.
 * <p>
 * To prevent terms from being stemmed use an instance of
 * {@link SetKeywordMarkerFilter} or a custom {@link TokenFilter} that sets
 * the {@link KeywordAttribute} before this {@link TokenStream}.
 * </p>
 * <p>
 * NOTE: Input is expected to be casefolded for Greek (including folding of final
 * sigma to sigma), and with diacritics removed. This can be achieved by using 
 * either {@link GreekLowerCaseFilter} or ICUFoldingFilter before GreekStemFilter.
 * @lucene.experimental
 */
public final class GreekStemFilter extends TokenFilter {
  private final GreekStemmer stemmer = new GreekStemmer();
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private final KeywordAttribute keywordAttr = addAttribute(KeywordAttribute.class);
  
  public GreekStemFilter(TokenStream input) {
    super(input);
  }
  
  @Override
  public boolean incrementToken() throws IOException {
    if (input.incrementToken()) {
      if(!keywordAttr.isKeyword()) {
        final int newlen = stemmer.stem(termAtt.buffer(), termAtt.length());
        termAtt.setLength(newlen);
      }
      return true;
    } else {
      return false;
    }
  }
}