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.internal.operators.flowable;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.*;
  import io.reactivex.rxjava3.functions.Consumer;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.internal.util.BackpressureHelper;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Emits the next or latest item when the given time elapses.
   * <p>
   * The operator emits the next item, then starts a timer. When the timer fires,
   * it tries to emit the latest item from upstream. If there was no upstream item,
   * in the meantime, the next upstream item is emitted immediately and the
   * timed process repeats.
   * <p>History: 2.1.14 - experimental
   * @param <T> the upstream and downstream value type
   * @since 2.2
   */
  public final class FlowableThrottleLatest<T> extends AbstractFlowableWithUpstream<T, T> {
  
      final long timeout;
  
      final TimeUnit unit;
  
      final Scheduler scheduler;
  
      final boolean emitLast;
  
      final Consumer<? super T> onDropped;
  
      public FlowableThrottleLatest(Flowable<T> source,
              long timeout, TimeUnit unit,
              Scheduler scheduler,
              boolean emitLast,
              Consumer<? super T> onDropped) {
          super(source);
          this.timeout = timeout;
          this.unit = unit;
          this.scheduler = scheduler;
          this.emitLast = emitLast;
          this.onDropped = onDropped;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> s) {
          source.subscribe(new ThrottleLatestSubscriber<>(s, timeout, unit, scheduler.createWorker(), emitLast, onDropped));
      }
  
      static final class ThrottleLatestSubscriber<T>
      extends AtomicInteger
      implements FlowableSubscriber<T>, Subscription, Runnable {
  
          private static final long serialVersionUID = -8296689127439125014L;
  
          final Subscriber<? super T> downstream;
  
          final long timeout;
  
          final TimeUnit unit;
  
          final Scheduler.Worker worker;
  
          final boolean emitLast;
  
          final AtomicReference<T> latest;
  
          final AtomicLong requested;
  
          final Consumer<? super T> onDropped;
  
          Subscription upstream;
  
          volatile boolean done;
          Throwable error;
  
          volatile boolean cancelled;
  
          volatile boolean timerFired;
  
          long emitted;
  
          boolean timerRunning;
  
          ThrottleLatestSubscriber(Subscriber<? super T> downstream,
                  long timeout, TimeUnit unit,
                  Scheduler.Worker worker,
                  boolean emitLast,
                  Consumer<? super T> onDropped) {
              this.downstream = downstream;
              this.timeout = timeout;
              this.unit = unit;
              this.worker = worker;
              this.emitLast = emitLast;
              this.latest = new AtomicReference<>();
              this.requested = new AtomicLong();
              this.onDropped = onDropped;
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(upstream, s)) {
                  upstream = s;
                  downstream.onSubscribe(this);
                  s.request(Long.MAX_VALUE);
              }
          }
  
          @Override
          public void onNext(T t) {
              T old = latest.getAndSet(t);
              if (onDropped != null && old != null) {
                  try {
                      onDropped.accept(old);
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      upstream.cancel();
                      error = ex;
                      done = true;
                  }
              }
              drain();
          }
  
          @Override
          public void onError(Throwable t) {
              error = t;
              done = true;
              drain();
          }
  
          @Override
          public void onComplete() {
              done = true;
              drain();
          }
  
          @Override
          public void request(long n) {
              if (SubscriptionHelper.validate(n)) {
                  BackpressureHelper.add(requested, n);
              }
          }
  
          @Override
          public void cancel() {
              cancelled = true;
              upstream.cancel();
              worker.dispose();
              if (getAndIncrement() == 0) {
                  clear();
              }
          }
  
          void clear() {
              if (onDropped != null) {
                  T v = latest.getAndSet(null);
                  if (v != null) {
                      try {
                          onDropped.accept(v);
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          RxJavaPlugins.onError(ex);
                      }
                  }
              } else {
                  latest.lazySet(null);
              }
          }
  
          @Override
          public void run() {
              timerFired = true;
              drain();
          }
  
          void drain() {
              if (getAndIncrement() != 0) {
                  return;
              }
  
              int missed = 1;
  
              AtomicReference<T> latest = this.latest;
              AtomicLong requested = this.requested;
              Subscriber<? super T> downstream = this.downstream;
  
              for (;;) {
  
                  for (;;) {
                      if (cancelled) {
                          clear();
                          return;
                      }
  
                      boolean d = done;
                      Throwable error = this.error;
  
                      if (d && error != null) {
                          if (onDropped != null) {
                              T v = latest.getAndSet(null);
                              if (v != null) {
                                  try {
                                      onDropped.accept(v);
                                  } catch (Throwable ex) {
                                      Exceptions.throwIfFatal(ex);
                                      error = new CompositeException(error, ex);
                                  }
                              }
                          } else {
                              latest.lazySet(null);
                          }
                          downstream.onError(error);
                          worker.dispose();
                          return;
                      }
  
                      T v = latest.get();
                      boolean empty = v == null;
  
                      if (d) {
                          if (!empty) {
                              v = latest.getAndSet(null);
                              if (emitLast) {
                                  long e = emitted;
                                  if (e != requested.get()) {
                                      emitted = e + 1;
                                      downstream.onNext(v);
                                      downstream.onComplete();
                                  } else {
                                      tryDropAndSignalMBE(v);
                                  }
                              } else {
                                  if (onDropped != null) {
                                      try {
                                          onDropped.accept(v);
                                      } catch (Throwable ex) {
                                          Exceptions.throwIfFatal(ex);
                                          downstream.onError(ex);
                                          worker.dispose();
                                          return;
                                      }
                                  }
                                  downstream.onComplete();
                              }
                          } else {
                              downstream.onComplete();
                          }
                          worker.dispose();
                          return;
                      }
  
                      if (empty) {
                          if (timerFired) {
                              timerRunning = false;
                              timerFired = false;
                          }
                          break;
                      }
  
                      if (!timerRunning || timerFired) {
                          v = latest.getAndSet(null);
                          long e = emitted;
                          if (e != requested.get()) {
                              downstream.onNext(v);
                              emitted = e + 1;
                          } else {
                              upstream.cancel();
                              tryDropAndSignalMBE(v);
                              worker.dispose();
                              return;
                          }
  
                          timerFired = false;
                          timerRunning = true;
                          worker.schedule(this, timeout, unit);
                      } else {
                          break;
                      }
                  }
  
                  missed = addAndGet(-missed);
                  if (missed == 0) {
                      break;
                  }
              }
          }
  
          void tryDropAndSignalMBE(T valueToDrop) {
              Throwable errorToSignal = MissingBackpressureException.createDefault();
              if (onDropped != null) {
                  try {
                      onDropped.accept(valueToDrop);
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      errorToSignal = new CompositeException(errorToSignal, ex);
                  }
              }
              downstream.onError(errorToSignal);
          }
      }
  }
  