/*
 * 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.
 */
package org.apache.lucene.collation;



import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.core.KeywordTokenizer;
import org.apache.lucene.util.AttributeFactory;

import java.text.Collator;

 Configures KeywordTokenizer with CollationAttributeFactory. 
 Converts the token into its CollationKey, and then encodes the CollationKey directly to allow it to be stored as an index term. 

  WARNING: Make sure you use exactly the same Collator at index and query time -- CollationKeys are only comparable when produced by the same Collator. Since RuleBasedCollators are not independently versioned, it is unsafe to search against stored CollationKeys unless the following are exactly the same (best practice is to store this information with the index and check that they remain the same at query time): 

  
JVM vendor
  
JVM version, including patch version
  
 The language (and country and variant, if specified) of the Locale used when constructing the collator via Collator.getInstance(Locale). 
  
 The collation strength used - see Collator.setStrength(int) 
 

  The ICUCollationKeyAnalyzer in the analysis-icu package 
  uses ICU4J's Collator, which makes
  its version available, thus allowing collation to be versioned
  independently from the JVM.  ICUCollationKeyAnalyzer is also significantly
  faster and generates significantly shorter keys than CollationKeyAnalyzer.
  See http://site.icu-project.org/charts/collation-icu4j-sun for key
  generation timing and key length comparisons between ICU4J and
  java.text.Collator over several languages.


  CollationKeys generated by java.text.Collators are not compatible
  with those those generated by ICU Collators.  Specifically, if you use 
  CollationKeyAnalyzer to generate index terms, do not use
  ICUCollationKeyAnalyzer on the query side, or vice versa.

Since:
3.1/**
 * <p>
 *   Configures {@link KeywordTokenizer} with {@link CollationAttributeFactory}.
 * </p>
 * <p>
 *   Converts the token into its {@link java.text.CollationKey}, and then
 *   encodes the CollationKey directly to allow 
 *   it to be stored as an index term.
 * </p>
 * <p>
 *   <strong>WARNING:</strong> Make sure you use exactly the same Collator at
 *   index and query time -- CollationKeys are only comparable when produced by
 *   the same Collator.  Since {@link java.text.RuleBasedCollator}s are not
 *   independently versioned, it is unsafe to search against stored
 *   CollationKeys unless the following are exactly the same (best practice is
 *   to store this information with the index and check that they remain the
 *   same at query time):
 * </p>
 * <ol>
 *   <li>JVM vendor</li>
 *   <li>JVM version, including patch version</li>
 *   <li>
 *     The language (and country and variant, if specified) of the Locale
 *     used when constructing the collator via
 *     {@link Collator#getInstance(java.util.Locale)}.
 *   </li>
 *   <li>
 *     The collation strength used - see {@link Collator#setStrength(int)}
 *   </li>
 * </ol> 
 * <p>
 *   The <code>ICUCollationKeyAnalyzer</code> in the analysis-icu package 
 *   uses ICU4J's Collator, which makes
 *   its version available, thus allowing collation to be versioned
 *   independently from the JVM.  ICUCollationKeyAnalyzer is also significantly
 *   faster and generates significantly shorter keys than CollationKeyAnalyzer.
 *   See <a href="http://site.icu-project.org/charts/collation-icu4j-sun"
 *   >http://site.icu-project.org/charts/collation-icu4j-sun</a> for key
 *   generation timing and key length comparisons between ICU4J and
 *   java.text.Collator over several languages.
 * </p>
 * <p>
 *   CollationKeys generated by java.text.Collators are not compatible
 *   with those those generated by ICU Collators.  Specifically, if you use 
 *   CollationKeyAnalyzer to generate index terms, do not use
 *   ICUCollationKeyAnalyzer on the query side, or vice versa.
 * </p>
 *
 * @since 3.1
 */
public final class CollationKeyAnalyzer extends Analyzer {
  private final CollationAttributeFactory factory;
  
  
Create a new CollationKeyAnalyzer, using the specified collator.
Params:
collator – CollationKey generator/**
   * Create a new CollationKeyAnalyzer, using the specified collator.
   *
   * @param collator CollationKey generator
   */
  public CollationKeyAnalyzer(Collator collator) {
    this.factory = new CollationAttributeFactory(collator);
  }

  @Override
  protected AttributeFactory attributeFactory(String fieldName) {
    return factory;
  }

  @Override
  protected TokenStreamComponents createComponents(String fieldName) {
    KeywordTokenizer tokenizer = new KeywordTokenizer(factory, KeywordTokenizer.DEFAULT_BUFFER_SIZE);
    return new TokenStreamComponents(tokenizer, tokenizer);
  }
}