content: package org.apache.lucene.analysis.bg;
  
  /**
   * 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 static org.apache.lucene.analysis.util.StemmerUtil.*;
  
  /**
   * Light Stemmer for Bulgarian.
   * <p>
   * Implements the algorithm described in:  
   * <i>
   * Searching Strategies for the Bulgarian Language
   * </i>
   * http://members.unine.ch/jacques.savoy/Papers/BUIR.pdf
   */
  public class BulgarianStemmer {
    
    /**
     * Stem an input buffer of Bulgarian text.
     * 
     * @param s input buffer
     * @param len length of input buffer
     * @return length of input buffer after normalization
     */
    public int stem(final char s[], int len) {
      if (len < 4) // do not stem
        return len;
      
      if (len > 5 && endsWith(s, len, "ища"))
        return len - 3;
      
      len = removeArticle(s, len);
      len = removePlural(s, len);
      
      if (len > 3) {
        if (endsWith(s, len, "я"))
          len--;
        if (endsWith(s, len, "а") ||
            endsWith(s, len, "о") ||
            endsWith(s, len, "е"))
          len--;
      }
      
      // the rule to rewrite ен -> н is duplicated in the paper.
      // in the perl implementation referenced by the paper, this is fixed.
      // (it is fixed here as well)
      if (len > 4 && endsWith(s, len, "ен")) {
        s[len - 2] = 'н'; // replace with н
        len--;
      }
      
      if (len > 5 && s[len - 2] == 'ъ') {
        s[len - 2] = s[len - 1]; // replace ъN with N
        len--;
      }
  
      return len;
    }
    
    /**
     * Mainly remove the definite article
     * @param s input buffer
     * @param len length of input buffer
     * @return new stemmed length
     */
    private int removeArticle(final char s[], final int len) {
      if (len > 6 && endsWith(s, len, "ият"))
        return len - 3;
      
      if (len > 5) {
        if (endsWith(s, len, "ът") ||
            endsWith(s, len, "то") ||
            endsWith(s, len, "те") ||
            endsWith(s, len, "та") ||
            endsWith(s, len, "ия"))
          return len - 2;
      }
      
      if (len > 4 && endsWith(s, len, "ят"))
        return len - 2;
  
      return len;
    }
    
    private int removePlural(final char s[], final int len) {
      if (len > 6) {
        if (endsWith(s, len, "овци"))
          return len - 3; // replace with о
        if (endsWith(s, len, "ове"))
          return len - 3;
        if (endsWith(s, len, "еве")) {
          s[len - 3] = 'й'; // replace with й
          return len - 2;
        }
      }
      
      if (len > 5) {
        if (endsWith(s, len, "ища"))
          return len - 3;
        if (endsWith(s, len, "та"))
          return len - 2;
        if (endsWith(s, len, "ци")) {
          s[len - 2] = 'к'; // replace with к
          return len - 1;
        }
        if (endsWith(s, len, "зи")) {
          s[len - 2] = 'г'; // replace with г
          return len - 1;
        }
        
        if (s[len - 3] == 'е' && s[len - 1] == 'и') {
          s[len - 3] = 'я'; // replace е with я, remove и
          return len - 1;
        }
      }
      
      if (len > 4) {
        if (endsWith(s, len, "си")) {
          s[len - 2] = 'х'; // replace with х
          return len - 1;
        }
        if (endsWith(s, len, "и"))
          return len - 1;
      }
      
      return len;
    }
  }
  