/*
 * 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
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package org.apache.lucene.analysis.icu;


import org.apache.lucene.analysis.TokenStream;

import com.ibm.icu.text.Normalizer2;

A TokenFilter that applies search term folding to Unicode text,
applying foldings from UTR#30 Character Foldings.

This filter applies the following foldings from the report to unicode text:

Accent removal
Case folding
Canonical duplicates folding
Dashes folding
Diacritic removal (including stroke, hook, descender)
Greek letterforms folding
Han Radical folding
Hebrew Alternates folding
Jamo folding
Letterforms folding
Math symbol folding
Multigraph Expansions: All
Native digit folding
No-break folding
Overline folding
Positional forms folding
Small forms folding
Space folding
Spacing Accents folding
Subscript folding
Superscript folding
Suzhou Numeral folding
Symbol folding
Underline folding
Vertical forms folding
Width folding


Additionally, Default Ignorables are removed, and text is normalized to NFKC.
All foldings, case folding, and normalization mappings are applied recursively
to ensure a fully folded and normalized result.


A normalizer with additional settings such as a filter that lists characters not
to be normalized can be passed in the constructor.

/**
 * A TokenFilter that applies search term folding to Unicode text,
 * applying foldings from UTR#30 Character Foldings.
 * <p>
 * This filter applies the following foldings from the report to unicode text:
 * <ul>
 * <li>Accent removal
 * <li>Case folding
 * <li>Canonical duplicates folding
 * <li>Dashes folding
 * <li>Diacritic removal (including stroke, hook, descender)
 * <li>Greek letterforms folding
 * <li>Han Radical folding
 * <li>Hebrew Alternates folding
 * <li>Jamo folding
 * <li>Letterforms folding
 * <li>Math symbol folding
 * <li>Multigraph Expansions: All
 * <li>Native digit folding
 * <li>No-break folding
 * <li>Overline folding
 * <li>Positional forms folding
 * <li>Small forms folding
 * <li>Space folding
 * <li>Spacing Accents folding
 * <li>Subscript folding
 * <li>Superscript folding
 * <li>Suzhou Numeral folding
 * <li>Symbol folding
 * <li>Underline folding
 * <li>Vertical forms folding
 * <li>Width folding
 * </ul>
 * <p>
 * Additionally, Default Ignorables are removed, and text is normalized to NFKC.
 * All foldings, case folding, and normalization mappings are applied recursively
 * to ensure a fully folded and normalized result.
 * </p>
 * <p>
 * A normalizer with additional settings such as a filter that lists characters not
 * to be normalized can be passed in the constructor.
 * </p>
 */
public final class ICUFoldingFilter extends ICUNormalizer2Filter {
  
A normalizer for search term folding to Unicode text,
applying foldings from UTR#30 Character Foldings.
/**
   * A normalizer for search term folding to Unicode text,
   * applying foldings from UTR#30 Character Foldings.
   */
  public static final Normalizer2 NORMALIZER = Normalizer2.getInstance(
    // TODO: if the wrong version of the ICU jar is used, loading these data files may give a strange error.
    // maybe add an explicit check? http://icu-project.org/apiref/icu4j/com/ibm/icu/util/VersionInfo.html
    ICUFoldingFilter.class.getResourceAsStream("utr30.nrm"),
    "utr30", Normalizer2.Mode.COMPOSE);

  
Create a new ICUFoldingFilter on the specified input
/**
   * Create a new ICUFoldingFilter on the specified input
   */
  public ICUFoldingFilter(TokenStream input) {
    super(input, NORMALIZER);
  }

  
Create a new ICUFoldingFilter on the specified input with the specified
normalizer
/**
   * Create a new ICUFoldingFilter on the specified input with the specified
   * normalizer
   */
  public ICUFoldingFilter(TokenStream input, Normalizer2 normalizer) {
    super(input, normalizer);
  }
}