code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed 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 io.reactivex.rxjava3.schedulers;
  
  import java.util.Queue;
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.annotations.*;
  import io.reactivex.rxjava3.core.Scheduler;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.EmptyDisposable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * A special, non thread-safe scheduler for testing operators that require
   * a scheduler without introducing real concurrency and allows manually advancing
   * a virtual time.
   * <p>
   * By default, the tasks submitted via the various {@code schedule} methods are not
   * wrapped by the {@link RxJavaPlugins#onSchedule(Runnable)} hook. To enable this behavior,
   * create a {@code TestScheduler} via {@link #TestScheduler(boolean)} or {@link #TestScheduler(long, TimeUnit, boolean)}.
   */
  public final class TestScheduler extends Scheduler {
      /** The ordered queue for the runnable tasks. */
      final Queue<TimedRunnable> queue = new PriorityBlockingQueue<>(11);
      /** Use the {@link RxJavaPlugins#onSchedule(Runnable)} hook when scheduling tasks. */
      final boolean useOnScheduleHook;
      /** The per-scheduler global order counter. */
      long counter;
      // Storing time in nanoseconds internally.
      volatile long time;
  
      /**
       * Creates a new TestScheduler with initial virtual time of zero.
       */
      public TestScheduler() {
          this(false);
      }
  
      /**
       * Creates a new TestScheduler with the option to use the
       * {@link RxJavaPlugins#onSchedule(Runnable)} hook when scheduling tasks.
       * <p>History: 3.0.10 - experimental
       * @param useOnScheduleHook if {@code true}, the tasks submitted to this
       *                          TestScheduler is wrapped via the
       *                          {@link RxJavaPlugins#onSchedule(Runnable)} hook
       * @since 3.1.0
       */
      public TestScheduler(boolean useOnScheduleHook) {
          this.useOnScheduleHook = useOnScheduleHook;
      }
  
      /**
       * Creates a new TestScheduler with the specified initial virtual time.
       *
       * @param delayTime
       *          the point in time to move the Scheduler's clock to
       * @param unit
       *          the units of time that {@code delayTime} is expressed in
       */
      public TestScheduler(long delayTime, TimeUnit unit) {
          this(delayTime, unit, false);
      }
  
      /**
       * Creates a new TestScheduler with the specified initial virtual time
       * and with the option to use the
       * {@link RxJavaPlugins#onSchedule(Runnable)} hook when scheduling tasks.
       * <p>History: 3.0.10 - experimental
       * @param delayTime
       *          the point in time to move the Scheduler's clock to
       * @param unit
       *          the units of time that {@code delayTime} is expressed in
       * @param useOnScheduleHook if {@code true}, the tasks submitted to this
       *                          TestScheduler is wrapped via the
       *                          {@link RxJavaPlugins#onSchedule(Runnable)} hook
       * @since 3.1.0
       */
      public TestScheduler(long delayTime, TimeUnit unit, boolean useOnScheduleHook) {
          time = unit.toNanos(delayTime);
          this.useOnScheduleHook = useOnScheduleHook;
      }
  
      static final class TimedRunnable implements Comparable<TimedRunnable> {
  
          final long time;
          final Runnable run;
          final TestWorker scheduler;
          final long count; // for differentiating tasks at same time
  
          TimedRunnable(TestWorker scheduler, long time, Runnable run, long count) {
              this.time = time;
              this.run = run;
              this.scheduler = scheduler;
              this.count = count;
          }
  
          @Override
          public String toString() {
              return String.format("TimedRunnable(time = %d, run = %s)", time, run.toString());
          }
  
          @Override
          public int compareTo(TimedRunnable o) {
              if (time == o.time) {
                  return Long.compare(count, o.count);
              }
              return Long.compare(time, o.time);
          }
      }
  
      @Override
      public long now(@NonNull TimeUnit unit) {
          return unit.convert(time, TimeUnit.NANOSECONDS);
      }
  
      /**
       * Moves the Scheduler's clock forward by a specified amount of time.
       *
       * @param delayTime
       *          the amount of time to move the Scheduler's clock forward
       * @param unit
       *          the units of time that {@code delayTime} is expressed in
       */
      public void advanceTimeBy(long delayTime, TimeUnit unit) {
          advanceTimeTo(time + unit.toNanos(delayTime), TimeUnit.NANOSECONDS);
      }
  
      /**
       * Moves the Scheduler's clock to a particular moment in time.
       *
       * @param delayTime
       *          the point in time to move the Scheduler's clock to
       * @param unit
       *          the units of time that {@code delayTime} is expressed in
       */
      public void advanceTimeTo(long delayTime, TimeUnit unit) {
          long targetTime = unit.toNanos(delayTime);
          triggerActions(targetTime);
      }
  
      /**
       * Triggers any actions that have not yet been triggered and that are scheduled to be triggered at or
       * before this Scheduler's present time.
       */
      public void triggerActions() {
          triggerActions(time);
      }
  
      private void triggerActions(long targetTimeInNanoseconds) {
          for (;;) {
              TimedRunnable current = queue.peek();
              if (current == null || current.time > targetTimeInNanoseconds) {
                  break;
              }
              // if scheduled time is 0 (immediate) use current virtual time
              time = current.time == 0 ? time : current.time;
              queue.remove(current);
  
              // Only execute if not unsubscribed
              if (!current.scheduler.disposed) {
                  current.run.run();
              }
          }
          time = targetTimeInNanoseconds;
      }
  
      @NonNull
      @Override
      public Worker createWorker() {
          return new TestWorker();
      }
  
      final class TestWorker extends Worker {
  
          volatile boolean disposed;
  
          @Override
          public void dispose() {
              disposed = true;
          }
  
          @Override
          public boolean isDisposed() {
              return disposed;
          }
  
          @NonNull
          @Override
          public Disposable schedule(@NonNull Runnable run, long delayTime, @NonNull TimeUnit unit) {
              if (disposed) {
                  return EmptyDisposable.INSTANCE;
              }
              if (useOnScheduleHook) {
                  run = RxJavaPlugins.onSchedule(run);
              }
              final TimedRunnable timedAction = new TimedRunnable(this, time + unit.toNanos(delayTime), run, counter++);
              queue.add(timedAction);
  
              return new QueueRemove(timedAction);
          }
  
          @NonNull
          @Override
          public Disposable schedule(@NonNull Runnable run) {
              if (disposed) {
                  return EmptyDisposable.INSTANCE;
              }
              if (useOnScheduleHook) {
                  run = RxJavaPlugins.onSchedule(run);
              }
              final TimedRunnable timedAction = new TimedRunnable(this, 0, run, counter++);
              queue.add(timedAction);
              return new QueueRemove(timedAction);
          }
  
          @Override
          public long now(@NonNull TimeUnit unit) {
              return TestScheduler.this.now(unit);
          }
  
          final class QueueRemove extends AtomicReference<TimedRunnable> implements Disposable {
  
              private static final long serialVersionUID = -7874968252110604360L;
  
              QueueRemove(TimedRunnable timedAction) {
                  this.lazySet(timedAction);
              }
  
              @Override
              public void dispose() {
                  TimedRunnable tr = getAndSet(null);
                  if (tr != null) {
                      queue.remove(tr);
                  }
              }
  
              @Override
              public boolean isDisposed() {
                  return get() == null;
              }
          }
      }
  }
  