content: package org.apache.lucene.collation;
  
  /**
   * 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 org.apache.lucene.analysis.Analyzer;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.KeywordTokenizer;
  import org.apache.lucene.analysis.Tokenizer;
  
  import java.text.Collator;
  import java.io.Reader;
  import java.io.IOException;
  
  /**
   * <p>
   *   Filters {@link KeywordTokenizer} with {@link CollationKeyFilter}.
   * </p>
   * <p>
   *   Converts the token into its {@link java.text.CollationKey}, and then
   *   encodes the CollationKey with 
   *   {@link org.apache.lucene.util.IndexableBinaryStringTools}, 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 icu package of Lucene's
   *   contrib area uses ICU4J's Collator, which makes its
   *   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>
   */
  public final class CollationKeyAnalyzer extends Analyzer {
    private Collator collator;
  
    public CollationKeyAnalyzer(Collator collator) {
      this.collator = collator;
    }
  
    @Override
    public TokenStream tokenStream(String fieldName, Reader reader) {
      TokenStream result = new KeywordTokenizer(reader);
      result = new CollationKeyFilter(result, collator);
      return result;
    }
    
    private class SavedStreams {
      Tokenizer source;
      TokenStream result;
    }
    
    @Override
    public TokenStream reusableTokenStream(String fieldName, Reader reader) 
      throws IOException {
      
      SavedStreams streams = (SavedStreams)getPreviousTokenStream();
      if (streams == null) {
        streams = new SavedStreams();
        streams.source = new KeywordTokenizer(reader);
        streams.result = new CollationKeyFilter(streams.source, collator);
        setPreviousTokenStream(streams);
      } else {
        streams.source.reset(reader);
      }
      return streams.result;
    }
  }
  