content: package org.apache.lucene.analysis.ru;
  
  /**
   * 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.
   */
  
  /* 
   * This algorithm is updated based on code located at:
   * http://members.unine.ch/jacques.savoy/clef/
   * 
   * Full copyright for that code follows:
   */
  
  /*
   * Copyright (c) 2005, Jacques Savoy
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without 
   * modification, are permitted provided that the following conditions are met:
   *
   * Redistributions of source code must retain the above copyright notice, this 
   * list of conditions and the following disclaimer. Redistributions in binary 
   * form must reproduce the above copyright notice, this list of conditions and
   * the following disclaimer in the documentation and/or other materials 
   * provided with the distribution. Neither the name of the author nor the names 
   * of its contributors may be used to endorse or promote products derived from 
   * this software without specific prior written permission.
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  import static org.apache.lucene.analysis.util.StemmerUtil.*;
  
  /**
   * Light Stemmer for Russian.
   * <p>
   * This stemmer implements the following algorithm:
   * <i>Indexing and Searching Strategies for the Russian Language.</i>
   * Ljiljana Dolamic and Jacques Savoy.
   */
  public class RussianLightStemmer {
  
    public int stem(char s[], int len) {
      len = removeCase(s, len);
      return normalize(s, len);
    }
    
    private int normalize(char s[], int len) {
      if (len > 3)
        switch(s[len-1]) { 
          case 'ь':
          case 'и': return len - 1;
          case 'н': if (s[len-2] == 'н') return len - 1;
        }
      return len;
    }
  
    private int removeCase(char s[], int len) {
      if (len > 6 && 
          (endsWith(s, len, "иями") ||
           endsWith(s, len, "оями")))
        return len - 4;
      
      if (len > 5 && 
          (endsWith(s, len, "иям") ||
           endsWith(s, len, "иях") ||
           endsWith(s, len, "оях") ||
           endsWith(s, len, "ями") ||
           endsWith(s, len, "оям") ||
           endsWith(s, len, "оьв") ||
           endsWith(s, len, "ами") ||
           endsWith(s, len, "его") ||
           endsWith(s, len, "ему") ||
           endsWith(s, len, "ери") ||
           endsWith(s, len, "ими") ||
           endsWith(s, len, "ого") ||
           endsWith(s, len, "ому") ||
           endsWith(s, len, "ыми") ||
           endsWith(s, len, "оев")))
        return len - 3;
      
      if (len > 4 &&
          (endsWith(s, len, "ая") ||
           endsWith(s, len, "яя") ||
           endsWith(s, len, "ях") ||
           endsWith(s, len, "юю") ||
           endsWith(s, len, "ах") ||
           endsWith(s, len, "ею") ||
           endsWith(s, len, "их") ||
           endsWith(s, len, "ия") ||
           endsWith(s, len, "ию") ||
           endsWith(s, len, "ьв") ||
           endsWith(s, len, "ою") ||
           endsWith(s, len, "ую") ||
           endsWith(s, len, "ям") ||
           endsWith(s, len, "ых") ||
           endsWith(s, len, "ея") ||
           endsWith(s, len, "ам") ||
           endsWith(s, len, "ем") ||
           endsWith(s, len, "ей") ||
           endsWith(s, len, "ём") ||
           endsWith(s, len, "ев") ||
           endsWith(s, len, "ий") ||
           endsWith(s, len, "им") ||
           endsWith(s, len, "ое") ||
           endsWith(s, len, "ой") ||
           endsWith(s, len, "ом") ||
           endsWith(s, len, "ов") ||
           endsWith(s, len, "ые") ||
           endsWith(s, len, "ый") ||
           endsWith(s, len, "ым") ||
           endsWith(s, len, "ми")))
        return len - 2;
      
      if (len > 3)
        switch(s[len-1]) {
          case 'а':
          case 'е':
          case 'и':
          case 'о':
          case 'у':
          case 'й':
          case 'ы':
          case 'я':
          case 'ь': return len - 1;
        }
      
      return len;
    }
  }
  