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 com.datastax.oss.driver.internal.core.metadata.token;
  
  import com.datastax.oss.driver.api.core.metadata.Node;
  import com.datastax.oss.driver.shaded.guava.common.collect.ImmutableSet;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import net.jcip.annotations.NotThreadSafe;
  
  /**
   * A reusable set builder that guarantees that identical sets (same elements in the same order) will
   * be represented by the same instance.
   */
  @NotThreadSafe
  class CanonicalNodeSetBuilder {
  
    private final Map<List<Node>, Set<Node>> canonicalSets = new HashMap<>();
    private final List<Node> elements = new ArrayList<>();
  
    void add(Node node) {
      // This is O(n), but the cardinality is low (max possible size is the replication factor).
      if (!elements.contains(node)) {
        elements.add(node);
      }
    }
  
    int size() {
      return elements.size();
    }
  
    Set<Node> build() {
      return canonicalSets.computeIfAbsent(elements, ImmutableSet::copyOf);
    }
  
    void clear() {
      elements.clear();
    }
  }
  