/*
 * 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.TokenStream;
import org.apache.lucene.collation.tokenattributes.ICUCollatedTermAttributeImpl;
import org.apache.lucene.util.AttributeFactory;

import com.ibm.icu.text.Collator;

 Converts each token into its CollationKey, and then encodes bytes 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. RuleBasedCollators are independently versioned, so it is safe to search against stored CollationKeys if 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): 

  
 Collator version - see Collator.getVersion() 
  
 The collation strength used - see Collator.setStrength(int) 
 
 CollationKeys generated by ICU Collators are not compatible with those generated by java.text.Collators. Specifically, if you use ICUCollationAttributeFactory to generate index terms, do not use CollationAttributeFactory on the query side, or vice versa. 

  ICUCollationAttributeFactory is significantly faster and generates significantly
  shorter keys than CollationAttributeFactory.  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.

/**
 * <p>
 *   Converts each token into its {@link com.ibm.icu.text.CollationKey}, and
 *   then encodes bytes 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.  {@link com.ibm.icu.text.RuleBasedCollator}s are 
 *   independently versioned, so it is safe to search against stored
 *   CollationKeys if 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>
 *     Collator version - see {@link Collator#getVersion()}
 *   </li>
 *   <li>
 *     The collation strength used - see {@link Collator#setStrength(int)}
 *   </li>
 * </ol> 
 * <p>
 *   CollationKeys generated by ICU Collators are not compatible with those
 *   generated by java.text.Collators.  Specifically, if you use 
 *   ICUCollationAttributeFactory to generate index terms, do not use 
 *   {@link CollationAttributeFactory} on the query side, or vice versa.
 * </p>
 * <p>
 *   ICUCollationAttributeFactory is significantly faster and generates significantly
 *   shorter keys than CollationAttributeFactory.  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>
 */
public class ICUCollationAttributeFactory extends AttributeFactory.StaticImplementationAttributeFactory<ICUCollatedTermAttributeImpl> {
  private final Collator collator;
  
  
Create an ICUCollationAttributeFactory, using TokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY as the factory for all other attributes. 
Params:
collator – CollationKey generator/**
   * Create an ICUCollationAttributeFactory, using 
   * {@link TokenStream#DEFAULT_TOKEN_ATTRIBUTE_FACTORY} as the
   * factory for all other attributes.
   * @param collator CollationKey generator
   */
  public ICUCollationAttributeFactory(Collator collator) {
    this(TokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY, collator);
  }
  
  
Create an ICUCollationAttributeFactory, using the supplied Attribute 
Factory as the factory for all other attributes.
Params:
delegate – Attribute Factory
collator – CollationKey generator/**
   * Create an ICUCollationAttributeFactory, using the supplied Attribute 
   * Factory as the factory for all other attributes.
   * @param delegate Attribute Factory
   * @param collator CollationKey generator
   */
  public ICUCollationAttributeFactory(AttributeFactory delegate, Collator collator) {
    super(delegate, ICUCollatedTermAttributeImpl.class);
    this.collator = collator;
  }
  
  @Override
  public ICUCollatedTermAttributeImpl createInstance() {
    return new ICUCollatedTermAttributeImpl(collator);
  }
}