content: package org.apache.lucene.analysis.id;
  
  /**
   * 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.*;
  
  /**
   * Stemmer for Indonesian.
   * <p>
   * Stems Indonesian words with the algorithm presented in:
   * <i>A Study of Stemming Effects on Information Retrieval in 
   * Bahasa Indonesia</i>, Fadillah Z Tala.
   * http://www.illc.uva.nl/Publications/ResearchReports/MoL-2003-02.text.pdf
   */
  public class IndonesianStemmer {
    private int numSyllables;
    private int flags;
    private static final int REMOVED_KE = 1;
    private static final int REMOVED_PENG = 2;
    private static final int REMOVED_DI = 4;
    private static final int REMOVED_MENG = 8;
    private static final int REMOVED_TER = 16;
    private static final int REMOVED_BER = 32;
    private static final int REMOVED_PE = 64;
    
    /**
     * Stem a term (returning its new length).
     * <p>
     * Use <code>stemDerivational</code> to control whether full stemming
     * or only light inflectional stemming is done.
     */
    public int stem(char text[], int length, boolean stemDerivational) {
      flags = 0;
      numSyllables = 0;
      for (int i = 0; i < length; i++)
        if (isVowel(text[i]))
            numSyllables++;
      
      if (numSyllables > 2) length = removeParticle(text, length);
      if (numSyllables > 2) length = removePossessivePronoun(text, length);
      
      if (stemDerivational)
        length = stemDerivational(text, length);
      return length;
    }
    
    private int stemDerivational(char text[], int length) {
      int oldLength = length;
      if (numSyllables > 2) length = removeFirstOrderPrefix(text, length);
      if (oldLength != length) { // a rule is fired
        oldLength = length;
        if (numSyllables > 2) length = removeSuffix(text, length);
        if (oldLength != length) // a rule is fired
          if (numSyllables > 2) length = removeSecondOrderPrefix(text, length);
      } else { // fail
        if (numSyllables > 2) length = removeSecondOrderPrefix(text, length);
        if (numSyllables > 2) length = removeSuffix(text, length);
      }
      return length;
    }
    
    private boolean isVowel(char ch) {
      switch(ch) {
        case 'a':
        case 'e':
        case 'i':
        case 'o':
        case 'u':
          return true;
        default:
          return false;
      }
    }
    
    private int removeParticle(char text[], int length) {
      if (endsWith(text, length, "kah") || 
          endsWith(text, length, "lah") || 
          endsWith(text, length, "pun")) {
          numSyllables--;
          return length - 3;
      }
      
      return length;
    }
    
    private int removePossessivePronoun(char text[], int length) {
      if (endsWith(text, length, "ku") || endsWith(text, length, "mu")) {
        numSyllables--;
        return length - 2;
      }
      
      if (endsWith(text, length, "nya")) {
        numSyllables--;
        return length - 3;
      }
      
      return length;
    }
    
    private int removeFirstOrderPrefix(char text[], int length) {
      if (startsWith(text, length, "meng")) {
        flags |= REMOVED_MENG;
        numSyllables--;
        return deleteN(text, 0, length, 4);
      }
      
      if (startsWith(text, length, "meny") && length > 4 && isVowel(text[4])) {
        flags |= REMOVED_MENG;
        text[3] = 's';
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "men")) {
        flags |= REMOVED_MENG;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
   
      if (startsWith(text, length, "mem")) {
        flags |= REMOVED_MENG;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "me")) {
        flags |= REMOVED_MENG;
        numSyllables--;
        return deleteN(text, 0, length, 2);
      }
      
      if (startsWith(text, length, "peng")) {
        flags |= REMOVED_PENG;
        numSyllables--;
        return deleteN(text, 0, length, 4);
      }
      
      if (startsWith(text, length, "peny") && length > 4 && isVowel(text[4])) {
        flags |= REMOVED_PENG;
        text[3] = 's';
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "peny")) {
        flags |= REMOVED_PENG;
        numSyllables--;
        return deleteN(text, 0, length, 4);
      }
      
      if (startsWith(text, length, "pen") && length > 3 && isVowel(text[3])) {
        flags |= REMOVED_PENG;
        text[2] = 't';
        numSyllables--;
        return deleteN(text, 0, length, 2);
      }
  
      if (startsWith(text, length, "pen")) {
        flags |= REMOVED_PENG;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "pem")) {
        flags |= REMOVED_PENG;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "di")) {
        flags |= REMOVED_DI;
        numSyllables--;
        return deleteN(text, 0, length, 2);
      }
      
      if (startsWith(text, length, "ter")) {
        flags |= REMOVED_TER;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "ke")) {
        flags |= REMOVED_KE;
        numSyllables--;
        return deleteN(text, 0, length, 2);
      }
      
      return length;
    }
    
    private int removeSecondOrderPrefix(char text[], int length) {
      if (startsWith(text, length, "ber")) {
        flags |= REMOVED_BER;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (length == 7 && startsWith(text, length, "belajar")) {
        flags |= REMOVED_BER;
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "be") && length > 4 
          && !isVowel(text[2]) && text[3] == 'e' && text[4] == 'r') {
        flags |= REMOVED_BER;
        numSyllables--;
        return deleteN(text, 0, length, 2);
      }
      
      if (startsWith(text, length, "per")) {
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (length == 7 && startsWith(text, length, "pelajar")) {
        numSyllables--;
        return deleteN(text, 0, length, 3);
      }
      
      if (startsWith(text, length, "pe")) {
        flags |= REMOVED_PE;
        numSyllables--;
        return deleteN(text, 0, length, 2);
      }
  
      return length;
    }
    
    private int removeSuffix(char text[], int length) {
      if (endsWith(text, length, "kan") 
          && (flags & REMOVED_KE) == 0 
          && (flags & REMOVED_PENG) == 0 
          && (flags & REMOVED_PE) == 0) {
        numSyllables--;
        return length - 3;
      }
      
      if (endsWith(text, length, "an") 
          && (flags & REMOVED_DI) == 0 
          && (flags & REMOVED_MENG) == 0 
          && (flags & REMOVED_TER) == 0) {
        numSyllables--;
        return length - 2;
      }
      
      if (endsWith(text, length, "i") 
          && !endsWith(text, length, "si") 
          && (flags & REMOVED_BER) == 0 
          && (flags & REMOVED_KE) == 0 
          && (flags & REMOVED_PENG) == 0) {
        numSyllables--;
        return length - 1;
      }
      return length;
    }  
  }
  