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/*
 * Copyright © 2016 Cask Data, Inc.
 *
 * Licensed 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 co.cask.hydrator.common.batch;

import com.google.common.collect.MapDifference;
import com.google.common.collect.Maps;
import org.apache.hadoop.conf.Configuration;

import java.util.HashMap;
import java.util.Map;

/**
 * Utility class for providing operations on the {@link Configuration}.
 */
public final class ConfigurationUtils {
  private ConfigurationUtils() {
    // no-op
  }

  /**
   * Get the {@link Map} of properties which are newly added or have updated in the configuration instance passed
   * to this method as a parameter. The modified configurations are compared with the default configurations
   * created using {@code new Configuation()}.
   * @param modifiedConf the updated configurations
   * @return the {@link Map} of properties which are newly added or have updated in the modifiedConf.
   */
  public static Map getNonDefaultConfigurations(Configuration modifiedConf) {
    MapDifference mapDifference = Maps.difference(getConfigurationAsMap(new Configuration()),
                                                                  getConfigurationAsMap(modifiedConf));
    // new keys in the modified configurations
    Map newEntries = mapDifference.entriesOnlyOnRight();
    // keys whose values got changed in the modified config
    Map> stringValueDifferenceMap = mapDifference.entriesDiffering();
    Map result = new HashMap<>();
    for (Map.Entry> stringValueDifferenceEntry :
      stringValueDifferenceMap.entrySet()) {
      result.put(stringValueDifferenceEntry.getKey(), stringValueDifferenceEntry.getValue().rightValue());
    }
    result.putAll(newEntries);
    return result;
  }

  private static Map getConfigurationAsMap(Configuration conf) {
    Map map = new HashMap<>();
    for (Map.Entry entry : conf) {
      map.put(entry.getKey(), entry.getValue());
    }
    return map;
  }
}