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.kafka.common.utils;
  
  import org.apache.kafka.common.TopicPartition;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.function.BiConsumer;
  import java.util.function.Function;
  import java.util.stream.Collectors;
  
  public final class CollectionUtils {
  
      private CollectionUtils() {}
  
      /**
       * Given two maps (A, B), returns all the key-value pairs in A whose keys are not contained in B
       */
      public static <K, V> Map<K, V> subtractMap(Map<? extends K, ? extends V> minuend, Map<? extends K, ? extends V> subtrahend) {
          return minuend.entrySet().stream()
                  .filter(entry -> !subtrahend.containsKey(entry.getKey()))
                  .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
      }
  
      /**
       * group data by topic
       *
       * @param data Data to be partitioned
       * @param <T> Partition data type
       * @return partitioned data
       */
      public static <T> Map<String, Map<Integer, T>> groupPartitionDataByTopic(Map<TopicPartition, ? extends T> data) {
          Map<String, Map<Integer, T>> dataByTopic = new HashMap<>();
          for (Map.Entry<TopicPartition, ? extends T> entry : data.entrySet()) {
              String topic = entry.getKey().topic();
              int partition = entry.getKey().partition();
              Map<Integer, T> topicData = dataByTopic.computeIfAbsent(topic, t -> new HashMap<>());
              topicData.put(partition, entry.getValue());
          }
          return dataByTopic;
      }
  
      /**
       * Group a list of partitions by the topic name.
       *
       * @param partitions The partitions to collect
       * @return partitions per topic
       */
      public static Map<String, List<Integer>> groupPartitionsByTopic(Collection<TopicPartition> partitions) {
          return groupPartitionsByTopic(
              partitions,
              topic -> new ArrayList<>(),
              List::add
          );
      }
  
      /**
       * Group a collection of partitions by topic
       *
       * @return The map used to group the partitions
       */
      public static <T> Map<String, T> groupPartitionsByTopic(
          Collection<TopicPartition> partitions,
          Function<String, T> buildGroup,
          BiConsumer<T, Integer> addToGroup
      ) {
          Map<String, T> dataByTopic = new HashMap<>();
          for (TopicPartition tp : partitions) {
              String topic = tp.topic();
              T topicData = dataByTopic.computeIfAbsent(topic, buildGroup);
              addToGroup.accept(topicData, tp.partition());
          }
          return dataByTopic;
      }
  }
  