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.beam.runners.core.metrics;
  
  import java.io.Serializable;
  import java.util.Map;
  import java.util.Objects;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.function.BiConsumer;
  import java.util.function.Consumer;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.MoreObjects;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A map from {@code K} to {@code T} that supports getting or creating values associated with a key
   * in a thread-safe manner.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class MetricsMap<K, T> implements Serializable {
  
    /** Interface for creating instances to populate the {@link MetricsMap}. */
    public interface Factory<K, T> extends Serializable {
      /**
       * Create an instance of {@code T} to use with the given {@code key}.
       *
       * <p>It must be safe to call this from multiple threads.
       */
      T createInstance(K key);
    }
  
    private final Factory<K, T> factory;
    private final ConcurrentMap<K, T> metrics = new ConcurrentHashMap<>();
  
    public MetricsMap(Factory<K, T> factory) {
      this.factory = factory;
    }
  
    /** Get or create the value associated with the given key. */
    public T get(K key) {
      T metric = metrics.get(key);
      if (metric == null) {
        metric = factory.createInstance(key);
        metric = MoreObjects.firstNonNull(metrics.putIfAbsent(key, metric), metric);
      }
      return metric;
    }
  
    /** Get the value associated with the given key, if it exists. */
    public @Nullable T tryGet(K key) {
      return metrics.get(key);
    }
  
    /** Return an iterable over the entries in the current {@link MetricsMap}. */
    public Iterable<Map.Entry<K, T>> entries() {
      return Iterables.unmodifiableIterable(metrics.entrySet());
    }
  
    /** Return an iterable over the values in the current {@link MetricsMap}. */
    public Iterable<T> values() {
      return Iterables.unmodifiableIterable(metrics.values());
    }
  
    /** Operates on each value in the metric map. * */
    public void forEachValue(Consumer<T> c) {
      metrics.forEach(
          (k, v) -> {
            c.accept(v);
          });
    }
  
    /** Operates on each entry in the metric map. * */
    public void forEach(BiConsumer<K, T> c) {
      metrics.forEach(c);
    }
  
    @Override
    public boolean equals(@Nullable Object object) {
      if (object instanceof MetricsMap) {
        MetricsMap<?, ?> metricsMap = (MetricsMap<?, ?>) object;
        return Objects.equals(metrics, metricsMap.metrics);
      }
  
      return false;
    }
  
    @Override
    public int hashCode() {
      return metrics.hashCode();
    }
  }
  