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Apache Solr (module: core)
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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.update.processor;

import static org.apache.solr.update.processor.FieldValueMutatingUpdateProcessor.valueMutator;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrException.ErrorCode;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.core.SolrCore;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;

/**
 * An updated processor that applies a configured regex to any CharSequence values found in the
 * selected fields, and replaces any matches with the configured replacement string.
 *
 * By default this processor applies itself to no fields.
 *
 * 
By default, literalReplacement is set to true, in which case, the 
 * replacement string will be treated literally by quoting via {@link
 * Matcher#quoteReplacement(String)}. And hence, '\' and '$' signs will not be processed. When
 * literalReplacement is set to false, one can perform backreference operations and
 * capture group substitutions.
 *
 * 
For example, with the configuration listed below, any sequence of multiple whitespace
 * characters found in values for field named title or content will be
 * replaced by a single space character.
 *
 * 
 * <processor class="solr.RegexReplaceProcessorFactory">
 *   <str name="fieldName">content</str>
 *   <str name="fieldName">title</str>
 *   <str name="pattern">\s+</str>
 *   <str name="replacement"> </str>
 *   <bool name="literalReplacement">true</bool>
 * </processor>
 *
 * @see java.util.regex.Pattern
 * @since 4.0.0
 */
public final class RegexReplaceProcessorFactory extends FieldMutatingUpdateProcessorFactory {

  private static final String REPLACEMENT_PARAM = "replacement";
  private static final String PATTERN_PARAM = "pattern";
  private static final String LITERAL_REPLACEMENT_PARAM = "literalReplacement";

  private Pattern pattern;
  private String replacement;
  // by default, literalReplacementEnabled is set to true to allow backward compatibility
  private boolean literalReplacementEnabled = true;

  @Override
  public void init(NamedList args) {

    Object patternParam = args.remove(PATTERN_PARAM);

    if (patternParam == null) {
      throw new SolrException(
          ErrorCode.SERVER_ERROR, "Missing required init parameter: " + PATTERN_PARAM);
    }

    try {
      pattern = Pattern.compile(patternParam.toString());
    } catch (PatternSyntaxException e) {
      throw new SolrException(ErrorCode.SERVER_ERROR, "Invalid regex: " + patternParam, e);
    }

    Object replacementParam = args.remove(REPLACEMENT_PARAM);
    if (replacementParam == null) {
      throw new SolrException(
          ErrorCode.SERVER_ERROR, "Missing required init parameter: " + REPLACEMENT_PARAM);
    }

    Boolean literalReplacement = args.removeBooleanArg(LITERAL_REPLACEMENT_PARAM);

    if (literalReplacement != null) {
      literalReplacementEnabled = literalReplacement;
    }

    if (literalReplacementEnabled) {
      replacement = Matcher.quoteReplacement(replacementParam.toString());
    } else {
      replacement = replacementParam.toString();
    }

    super.init(args);
  }

  /**
   * @see FieldMutatingUpdateProcessor#SELECT_NO_FIELDS
   */
  @Override
  protected FieldMutatingUpdateProcessor.FieldNameSelector getDefaultSelector(final SolrCore core) {

    return FieldMutatingUpdateProcessor.SELECT_NO_FIELDS;
  }

  @Override
  public UpdateRequestProcessor getInstance(
      SolrQueryRequest request, SolrQueryResponse response, UpdateRequestProcessor next) {
    return valueMutator(
        getSelector(),
        next,
        src -> {
          if (src instanceof CharSequence) {
            CharSequence txt = (CharSequence) src;
            return pattern.matcher(txt).replaceAll(replacement);
          }
          return src;
        });
  }
}