content: package org.apache.lucene.analysis.eu;
  
  /**
   * 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 java.io.Reader;
  import java.util.Set;
  
  import org.apache.lucene.analysis.Analyzer;
  import org.apache.lucene.analysis.LowerCaseFilter;
  import org.apache.lucene.analysis.StopFilter;
  import org.apache.lucene.analysis.KeywordMarkerFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.Tokenizer;
  import org.apache.lucene.analysis.snowball.SnowballFilter;
  import org.apache.lucene.analysis.standard.StandardFilter;
  import org.apache.lucene.analysis.standard.StandardTokenizer;
  import org.apache.lucene.analysis.CharArraySet;
  import org.apache.lucene.analysis.StopwordAnalyzerBase;
  import org.apache.lucene.util.Version;
  import org.tartarus.snowball.ext.BasqueStemmer;
  
  /**
   * {@link Analyzer} for Basque.
   */
  public final class BasqueAnalyzer extends StopwordAnalyzerBase {
    private final Set<?> stemExclusionSet;
    
    /** File containing default Basque stopwords. */
    public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
    
    /**
     * Returns an unmodifiable instance of the default stop words set.
     * @return default stop words set.
     */
    public static Set<?> getDefaultStopSet(){
      return DefaultSetHolder.DEFAULT_STOP_SET;
    }
    
    /**
     * Atomically loads the DEFAULT_STOP_SET in a lazy fashion once the outer class 
     * accesses the static final set the first time.;
     */
    private static class DefaultSetHolder {
      static final Set<?> DEFAULT_STOP_SET;
  
      static {
        try {
          DEFAULT_STOP_SET = loadStopwordSet(false, 
              BasqueAnalyzer.class, DEFAULT_STOPWORD_FILE, "#");
        } catch (IOException ex) {
          // default set should always be present as it is part of the
          // distribution (JAR)
          throw new RuntimeException("Unable to load default stopword set");
        }
      }
    }
  
    /**
     * Builds an analyzer with the default stop words: {@link #DEFAULT_STOPWORD_FILE}.
     */
    public BasqueAnalyzer(Version matchVersion) {
      this(matchVersion, DefaultSetHolder.DEFAULT_STOP_SET);
    }
    
    /**
     * Builds an analyzer with the given stop words.
     * 
     * @param matchVersion lucene compatibility version
     * @param stopwords a stopword set
     */
    public BasqueAnalyzer(Version matchVersion, Set<?> stopwords) {
      this(matchVersion, stopwords, CharArraySet.EMPTY_SET);
    }
  
    /**
     * Builds an analyzer with the given stop words. If a non-empty stem exclusion set is
     * provided this analyzer will add a {@link KeywordMarkerFilter} before
     * stemming.
     * 
     * @param matchVersion lucene compatibility version
     * @param stopwords a stopword set
     * @param stemExclusionSet a set of terms not to be stemmed
     */
    public BasqueAnalyzer(Version matchVersion, Set<?> stopwords, Set<?> stemExclusionSet) {
      super(matchVersion, stopwords);
      this.stemExclusionSet = CharArraySet.unmodifiableSet(CharArraySet.copy(
          matchVersion, stemExclusionSet));
    }
  
    /**
     * Creates a
     * {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
     * which tokenizes all the text in the provided {@link Reader}.
     * 
     * @return A
     *         {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
     *         built from an {@link StandardTokenizer} filtered with
     *         {@link StandardFilter}, {@link LowerCaseFilter}, {@link StopFilter}
     *         , {@link KeywordMarkerFilter} if a stem exclusion set is
     *         provided and {@link SnowballFilter}.
     */
    @Override
    protected TokenStreamComponents createComponents(String fieldName,
        Reader reader) {
      final Tokenizer source = new StandardTokenizer(matchVersion, reader);
      TokenStream result = new StandardFilter(matchVersion, source);
      result = new LowerCaseFilter(matchVersion, result);
      result = new StopFilter(matchVersion, result, stopwords);
      if(!stemExclusionSet.isEmpty())
        result = new KeywordMarkerFilter(result, stemExclusionSet);
      result = new SnowballFilter(result, new BasqueStemmer());
      return new TokenStreamComponents(source, result);
    }
  }
  