lucene/analysis/icu/src/java/org/apache/lucene/analysis/icu/ICUFoldingFilterFactory.java

/*
 * 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.analysis.icu;


import java.util.Map;

import com.ibm.icu.text.FilteredNormalizer2;
import com.ibm.icu.text.Normalizer2;
import com.ibm.icu.text.UnicodeSet;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.util.TokenFilterFactory;

/**
 * Factory for {@link ICUFoldingFilter}.
 * <pre class="prettyprint">
 * &lt;fieldType name="text_folded" class="solr.TextField" positionIncrementGap="100"&gt;
 *   &lt;analyzer&gt;
 *     &lt;tokenizer class="solr.WhitespaceTokenizerFactory"/&gt;
 *     &lt;filter class="solr.ICUFoldingFilterFactory"/&gt;
 *   &lt;/analyzer&gt;
 * &lt;/fieldType&gt;</pre>
 * @since 3.1.0
 * @lucene.spi {@value #NAME}
 */
public class ICUFoldingFilterFactory extends TokenFilterFactory {

  /** SPI name */
  public static final String NAME = "icuFolding";

  private final Normalizer2 normalizer;

  /** Creates a new ICUFoldingFilterFactory */
  public ICUFoldingFilterFactory(Map<String,String> args) {
    super(args);

    Normalizer2 normalizer = ICUFoldingFilter.NORMALIZER;
    String filter = get(args, "filter");
    if (filter != null) {
      UnicodeSet set = new UnicodeSet(filter);
      if (!set.isEmpty()) {
        set.freeze();
        normalizer = new FilteredNormalizer2(normalizer, set);
      }
    }
    if (!args.isEmpty()) {
      throw new IllegalArgumentException("Unknown parameters: " + args);
    }
    this.normalizer = normalizer;
  }

  @Override
  public TokenStream create(TokenStream input) {
    return new ICUFoldingFilter(input, normalizer);
  }

  @Override
  public TokenStream normalize(TokenStream input) {
    return create(input);
  }
}