content: /**
   * 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.solr.analysis;
  
  import org.apache.lucene.analysis.TokenFilter;
  import org.apache.lucene.analysis.TokenStream;
  import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
  
  import java.util.regex.Pattern;
  import java.util.regex.Matcher;
  import java.io.IOException;
  
  /**
   * A TokenFilter which applies a Pattern to each token in the stream,
   * replacing match occurances with the specified replacement string.
   *
   * <p>
   * <b>Note:</b> Depending on the input and the pattern used and the input
   * TokenStream, this TokenFilter may produce Tokens whose text is the empty
   * string.
   * </p>
   * 
   * @version $Id:$
   * @see Pattern
   */
  public final class PatternReplaceFilter extends TokenFilter {
    private final Pattern p;
    private final String replacement;
    private final boolean all;
    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    private final Matcher m;
  
    /**
     * Constructs an instance to replace either the first, or all occurances
     *
     * @param in the TokenStream to process
     * @param p the patterm to apply to each Token
     * @param replacement the "replacement string" to substitute, if null a
     *        blank string will be used. Note that this is not the literal
     *        string that will be used, '$' and '\' have special meaning.
     * @param all if true, all matches will be replaced otherwise just the first match.
     * @see Matcher#quoteReplacement
     */
    public PatternReplaceFilter(TokenStream in,
                                Pattern p,
                                String replacement,
                                boolean all) {
      super(in);
      this.p=p;
      this.replacement = (null == replacement) ? "" : replacement;
      this.all=all;
      this.m = p.matcher(termAtt);
    }
  
    @Override
    public boolean incrementToken() throws IOException {
      if (!input.incrementToken()) return false;
      
      m.reset();
      if (m.find()) {
        // replaceAll/replaceFirst will reset() this previous find.
        String transformed = all ? m.replaceAll(replacement) : m.replaceFirst(replacement);
        termAtt.setEmpty().append(transformed);
      }
  
      return true;
    }
  
  }
  