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.streams.kstream.internals.graph;
  
  import java.util.HashSet;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  public class NodesWithRelaxedNullKeyJoinDownstream {
  
      private final HashSet<GraphNode> visited;
      private final HashSet<GraphNode> nonOptimizable;
      private final GraphNode start;
  
      public NodesWithRelaxedNullKeyJoinDownstream(final GraphNode root) {
          this.start = root;
          this.visited = new HashSet<>();
          this.nonOptimizable = new HashSet<>();
      }
  
      public Set<BaseRepartitionNode<?, ?>> find() {
          traverseGraph(this.start);
          return visited.stream()
              .filter(node -> node instanceof BaseRepartitionNode && !nonOptimizable.contains(node))
              .map(node -> (BaseRepartitionNode<?, ?>) node)
              .collect(Collectors.toSet());
      }
  
      private void traverseGraph(final GraphNode node) {
          if (!visited.contains(node)) {
              for (final GraphNode child : node.children()) {
                  traverseGraph(child);
                  if (child.labels().contains(GraphNode.Label.NULL_KEY_RELAXED_JOIN) || nonOptimizable.contains(child)) {
                      nonOptimizable.add(node);
                  }
              }
              visited.add(node);
          }
      }
  }
  