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.ambari.server.topology.addservice;
  
  import static com.google.common.collect.Lists.newArrayList;
  import static java.util.Comparator.comparing;
  import static java.util.stream.Collectors.groupingBy;
  import static java.util.stream.Collectors.mapping;
  import static java.util.stream.Collectors.toCollection;
  import static java.util.stream.Collectors.toMap;
  
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  import java.util.stream.IntStream;
  
  
  public class GroupByComponentsStrategy implements HostGroupStrategy {
    @Override
    public Map<String, Set<String>> calculateHostGroups(Map<String, Set<String>> hostComponentMap) {
      // create components -> hosts map, the values will be the host groups
      List<Set<String>> hostGroups = newArrayList(
        hostComponentMap.entrySet().stream().collect(
          groupingBy(Map.Entry::getValue, mapping(Map.Entry::getKey, toCollection(TreeSet::new))) ).values()); // hosts names are sorted in the host group
      hostGroups.sort(comparing(hosts -> hosts.iterator().next())); // alphabetical order by the first hostname in the group to have consistent outcome
  
      // give a name to each host group and add to a map
      Map<String, Set<String>> hostgroupMap = IntStream.range(0, hostGroups.size()).boxed()
        .collect(toMap(i -> "host_group_" + (i + 1), i -> hostGroups.get(i)));
  
      return hostgroupMap;
    }
  }
  