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/**
 * 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.Token;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.tokenattributes.TermAttribute;

import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.Set;
import java.io.IOException;
import java.nio.CharBuffer;

/**
 * A TokenFilter which applies a Pattern to each token in the stream,
 * replacing match occurances with the specified replacement string.
 *
 * 
 * Note: Depending on the input and the pattern used and the input
 * TokenStream, this TokenFilter may produce Tokens whose text is the empty
 * string.
 * 
 * 
 * @version $Id:$
 * @see Pattern
 */
public final class PatternReplaceFilter extends TokenFilter {
  private final Pattern p;
  private final String replacement;
  private final boolean all;
  private final TermAttribute termAtt;
  /**
   * 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.termAtt = (TermAttribute)addAttribute(TermAttribute.class);
  }

  @Override
  public boolean incrementToken() throws IOException {
    if (!input.incrementToken()) return false;
    
    CharSequence text = CharBuffer.wrap(termAtt.termBuffer(), 0, termAtt.termLength());
    Matcher m = p.matcher(text);

    if (all) {
      termAtt.setTermBuffer(m.replaceAll(replacement));
    } else {
      termAtt.setTermBuffer(m.replaceFirst(replacement));
    }

    return true;
  }

}