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.internals.KafkaFutureImpl;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import java.util.TreeMap;
  import java.util.concurrent.Callable;
  import java.util.concurrent.Future;
  import java.util.concurrent.ScheduledExecutorService;
  
  public final class MockScheduler implements Scheduler, MockTime.Listener {
      private static final Logger log = LoggerFactory.getLogger(MockScheduler.class);
  
      /**
       * The MockTime object.
       */
      private final MockTime time;
  
      /**
       * Futures which are waiting for a specified wall-clock time to arrive.
       */
      private final TreeMap<Long, List<KafkaFutureImpl<Long>>> waiters = new TreeMap<>();
  
      public MockScheduler(MockTime time) {
          this.time = time;
          time.addListener(this);
      }
  
      @Override
      public Time time() {
          return time;
      }
  
      @Override
      public synchronized void onTimeUpdated() {
          long timeMs = time.milliseconds();
          while (true) {
              Map.Entry<Long, List<KafkaFutureImpl<Long>>> entry = waiters.firstEntry();
              if ((entry == null) || (entry.getKey() > timeMs)) {
                  break;
              }
              for (KafkaFutureImpl<Long> future : entry.getValue()) {
                  future.complete(timeMs);
              }
              waiters.remove(entry.getKey());
          }
      }
  
      public synchronized void addWaiter(long delayMs, KafkaFutureImpl<Long> waiter) {
          long timeMs = time.milliseconds();
          if (delayMs <= 0) {
              waiter.complete(timeMs);
          } else {
              long triggerTimeMs = timeMs + delayMs;
              List<KafkaFutureImpl<Long>> futures = waiters.computeIfAbsent(triggerTimeMs, k -> new ArrayList<>());
              futures.add(waiter);
          }
      }
  
      @Override
      public <T> Future<T> schedule(final ScheduledExecutorService executor,
                                    final Callable<T> callable, long delayMs) {
          final KafkaFutureImpl<T> future = new KafkaFutureImpl<>();
          KafkaFutureImpl<Long> waiter = new KafkaFutureImpl<>();
          waiter.thenApply(now -> {
              executor.submit((Callable<Void>) () -> {
                  // Note: it is possible that we'll execute Callable#call right after
                  // the future is cancelled.  This is a valid sequence of events
                  // that the author of the Callable needs to be able to handle.
                  //
                  // Note 2: If the future is cancelled, we will not remove the waiter
                  // from this MockTime object.  This small bit of inefficiency is acceptable
                  // in testing code (at least we aren't polling!)
                  if (!future.isCancelled()) {
                      try {
                          log.trace("Invoking {} at {}", callable, now);
                          future.complete(callable.call());
                      } catch (Throwable throwable) {
                          future.completeExceptionally(throwable);
                      }
                  }
                  return null;
              });
              return null;
          });
          log.trace("Scheduling {} for {} ms from now.", callable, delayMs);
          addWaiter(delayMs, waiter);
          return future;
      }
  }
  