/*
 * 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 org.apache.solr.common.util.NamedList;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;

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

/**
 * Removes any values found which are CharSequence with a length of 0. 
 * (ie: empty strings) 
 * <p>
 * By default this processor applies itself to all fields.
 * </p>
 *
 * <p>
 * For example, with the configuration listed below, blank strings will be 
 * removed from all fields except those whose name ends with 
 * "<code>_literal</code>".
 * </p>
 *
 * <pre class="prettyprint">
 * <processor class="solr.RemoveBlankFieldUpdateProcessorFactory">
 *   <lst name="exclude">
 *     <str name="fieldRegex">.*_literal</str>
 *   </lst>
 * </processor></pre>
 *
 */
public final class RemoveBlankFieldUpdateProcessorFactory extends FieldMutatingUpdateProcessorFactory {

  @SuppressWarnings("unchecked")
  @Override
  public void init(NamedList args) {
    // no trim specific init args
    super.init(args);
  }
  
  @Override
  public UpdateRequestProcessor getInstance(SolrQueryRequest req,
                                            SolrQueryResponse rsp,
                                            UpdateRequestProcessor next) {
    return valueMutator(getSelector(), next, src -> {
      if (src instanceof CharSequence
          && 0 == ((CharSequence) src).length()) {
        return DELETE_VALUE_SINGLETON;
      }
      return src;
    });
  }
}