package org.wikimedia.search.extra.analysis.ukrainian;
   
   import java.io.IOException;
   import java.io.Reader;
   import java.io.UncheckedIOException;
   import java.nio.charset.StandardCharsets;
   
   import org.apache.lucene.analysis.CharArraySet;
   import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.WordlistLoader;
  import org.apache.lucene.util.IOUtils;
  import org.elasticsearch.common.settings.Settings;
  import org.elasticsearch.env.Environment;
  import org.elasticsearch.index.IndexSettings;
  import org.elasticsearch.index.analysis.AbstractTokenFilterFactory;
  
  public class UkrainianStopFilterFactory extends AbstractTokenFilterFactory {
  
      protected static final CharArraySet UK_STOP = getStopwords();
  
      public UkrainianStopFilterFactory(IndexSettings indexSettings, Environment env, String name, Settings settings) {
          super(indexSettings, name, settings);
      }
  
      @Override public TokenStream create(TokenStream tokenStream) {
          return new UkrainianStopFilter(tokenStream, UK_STOP);
      }
  
      private static CharArraySet getStopwords() {
          try (
              Reader reader = IOUtils.getDecodingReader(UkrainianStopFilterFactory.class, "stopwords.txt", StandardCharsets.UTF_8)
          ) {
              return CharArraySet.unmodifiableSet(WordlistLoader.getWordSet(reader, "#"));
          } catch (IOException e) {
              throw new UncheckedIOException("Could not load the Ukrainian stopword list.", e);
          }
      }
  
  }