content: package org.apache.lucene.analysis.el;
  
  /**
   * Copyright 2005 The Apache Software Foundation
   *
   * Licensed 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 org.apache.lucene.analysis.TokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  import org.apache.lucene.util.CharacterUtils;
  import org.apache.lucene.util.Version;
  
  /**
   * Normalizes token text to lower case, removes some Greek diacritics,
   * and standardizes final sigma to sigma. 
   * <a name="version"/>
   * <p>You must specify the required {@link Version}
   * compatibility when creating GreekLowerCaseFilter:
   * <ul>
   *   <li> As of 3.1, supplementary characters are properly lowercased.
   * </ul>
   */
  public final class GreekLowerCaseFilter extends TokenFilter {
    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    private final CharacterUtils charUtils;
  
    /** @deprecated Use {@link #GreekLowerCaseFilter(Version, TokenStream)} instead. */
    @Deprecated
    public GreekLowerCaseFilter(TokenStream in) {
      this(Version.LUCENE_30, in);
    }
    
    /**
     * Create a GreekLowerCaseFilter that normalizes Greek token text.
     * 
     * @param matchVersion Lucene compatibility version, 
     *   See <a href="#version">above</a>
     * @param in TokenStream to filter
     */
    public GreekLowerCaseFilter(Version matchVersion, TokenStream in) {
      super(in);
      this.charUtils = CharacterUtils.getInstance(matchVersion);
    }
    
    @Override
    public boolean incrementToken() throws IOException {
      if (input.incrementToken()) {
        char[] chArray = termAtt.buffer();
        int chLen = termAtt.length();
        for (int i = 0; i < chLen;) {
          i += Character.toChars(
              lowerCase(charUtils.codePointAt(chArray, i)), chArray, i);
         }
        return true;
      } else {
        return false;
      }
    }
    
    private int lowerCase(int codepoint) {
      switch(codepoint) {
        /* There are two lowercase forms of sigma:
         *   U+03C2: small final sigma (end of word)
         *   U+03C3: small sigma (otherwise)
         *   
         * Standardize both to U+03C3
         */
        case '\u03C2': /* small final sigma */
          return '\u03C3'; /* small sigma */
          
        /* Some greek characters contain diacritics.
         * This filter removes these, converting to the lowercase base form.
         */
          
        case '\u0386': /* capital alpha with tonos */
        case '\u03AC': /* small alpha with tonos */
          return '\u03B1'; /* small alpha */
          
        case '\u0388': /* capital epsilon with tonos */
        case '\u03AD': /* small epsilon with tonos */
          return '\u03B5'; /* small epsilon */
          
        case '\u0389': /* capital eta with tonos */
        case '\u03AE': /* small eta with tonos */
          return '\u03B7'; /* small eta */
          
        case '\u038A': /* capital iota with tonos */
        case '\u03AA': /* capital iota with dialytika */
        case '\u03AF': /* small iota with tonos */
        case '\u03CA': /* small iota with dialytika */
        case '\u0390': /* small iota with dialytika and tonos */
          return '\u03B9'; /* small iota */
          
        case '\u038E': /* capital upsilon with tonos */
        case '\u03AB': /* capital upsilon with dialytika */
        case '\u03CD': /* small upsilon with tonos */
        case '\u03CB': /* small upsilon with dialytika */
        case '\u03B0': /* small upsilon with dialytika and tonos */
          return '\u03C5'; /* small upsilon */
          
        case '\u038C': /* capital omicron with tonos */
        case '\u03CC': /* small omicron with tonos */
          return '\u03BF'; /* small omicron */
          
        case '\u038F': /* capital omega with tonos */
        case '\u03CE': /* small omega with tonos */
          return '\u03C9'; /* small omega */
          
        /* The previous implementation did the conversion below.
         * Only implemented for backwards compatibility with old indexes.
         */
          
        case '\u03A2': /* reserved */
          return '\u03C2'; /* small final sigma */
          
        default:
          return Character.toLowerCase(codepoint);
      }
    }
  }
  