content: package org.apache.lucene.analysis.tr;
  
  /**
   * 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 java.io.IOException;
  
  import org.apache.lucene.analysis.TokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  
  /**
   * Normalizes Turkish token text to lower case.
   * <p>
   * Turkish and Azeri have unique casing behavior for some characters. This
   * filter applies Turkish lowercase rules. For more information, see <a
   * href="http://en.wikipedia.org/wiki/Turkish_dotted_and_dotless_I"
   * >http://en.wikipedia.org/wiki/Turkish_dotted_and_dotless_I</a>
   * </p>
   */
  public final class TurkishLowerCaseFilter extends TokenFilter {
    private static final int LATIN_CAPITAL_LETTER_I = '\u0049';
    private static final int LATIN_SMALL_LETTER_I = '\u0069';
    private static final int LATIN_SMALL_LETTER_DOTLESS_I = '\u0131';
    private static final int COMBINING_DOT_ABOVE = '\u0307';
    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    
    /**
     * Create a new TurkishLowerCaseFilter, that normalizes Turkish token text 
     * to lower case.
     * 
     * @param in TokenStream to filter
     */
    public TurkishLowerCaseFilter(TokenStream in) {
      super(in);
    }
    
    @Override
    public final boolean incrementToken() throws IOException {
      boolean iOrAfter = false;
      
      if (input.incrementToken()) {
        final char[] buffer = termAtt.buffer();
        int length = termAtt.length();
        for (int i = 0; i < length;) {
          final int ch = Character.codePointAt(buffer, i);
      
          iOrAfter = (ch == LATIN_CAPITAL_LETTER_I || 
              (iOrAfter && Character.getType(ch) == Character.NON_SPACING_MARK));
          
          if (iOrAfter) { // all the special I turkish handling happens here.
            switch(ch) {
              // remove COMBINING_DOT_ABOVE to mimic composed lowercase
              case COMBINING_DOT_ABOVE:
                length = delete(buffer, i, length);
                continue;
              // i itself, it depends if it is followed by COMBINING_DOT_ABOVE
              // if it is, we will make it small i and later remove the dot
              case LATIN_CAPITAL_LETTER_I:
                if (isBeforeDot(buffer, i + 1, length)) {
                  buffer[i] = LATIN_SMALL_LETTER_I;
                } else {
                  buffer[i] = LATIN_SMALL_LETTER_DOTLESS_I;
                  // below is an optimization. no COMBINING_DOT_ABOVE follows,
                  // so don't waste time calculating Character.getType(), etc
                  iOrAfter = false;
                }
                i++;
                continue;
            }
          }
          
          i += Character.toChars(Character.toLowerCase(ch), buffer, i);
        }
        
        termAtt.setLength(length);
        return true;
      } else
        return false;
    }
    
    
    /**
     * lookahead for a combining dot above.
     * other NSMs may be in between.
     */
    private boolean isBeforeDot(char s[], int pos, int len) {
      for (int i = pos; i < len;) {
        final int ch = Character.codePointAt(s, i);
        if (Character.getType(ch) != Character.NON_SPACING_MARK)
          return false;
        if (ch == COMBINING_DOT_ABOVE)
          return true;
        i += Character.charCount(ch);
      }
      
      return false;
    }
    
    /**
     * delete a character in-place.
     * rarely happens, only if COMBINING_DOT_ABOVE is found after an i
     */
    private int delete(char s[], int pos, int len) {
      if (pos < len) 
        System.arraycopy(s, pos + 1, s, pos, len - pos - 1);
      
      return len - 1;
    }
  }
  