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.atomic.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.MissingBackpressureException;
  import io.reactivex.rxjava3.internal.queue.MpscLinkedQueue;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.internal.util.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  import io.reactivex.rxjava3.processors.UnicastProcessor;
  import io.reactivex.rxjava3.subscribers.DisposableSubscriber;
  
  public final class FlowableWindowBoundary<T, B> extends AbstractFlowableWithUpstream<T, Flowable<T>> {
      final Publisher<B> other;
      final int capacityHint;
  
      public FlowableWindowBoundary(Flowable<T> source, Publisher<B> other, int capacityHint) {
          super(source);
          this.other = other;
          this.capacityHint = capacityHint;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super Flowable<T>> subscriber) {
          WindowBoundaryMainSubscriber<T, B> parent = new WindowBoundaryMainSubscriber<>(subscriber, capacityHint);
  
          subscriber.onSubscribe(parent);
  
          parent.innerNext();
  
          other.subscribe(parent.boundarySubscriber);
  
          source.subscribe(parent);
      }
  
      static final class WindowBoundaryMainSubscriber<T, B>
      extends AtomicInteger
      implements FlowableSubscriber<T>, Subscription, Runnable {
  
          private static final long serialVersionUID = 2233020065421370272L;
  
          final Subscriber<? super Flowable<T>> downstream;
  
          final int capacityHint;
  
          final WindowBoundaryInnerSubscriber<T, B> boundarySubscriber;
  
          final AtomicReference<Subscription> upstream;
  
          final AtomicInteger windows;
  
          final MpscLinkedQueue<Object> queue;
  
          final AtomicThrowable errors;
  
          final AtomicBoolean stopWindows;
  
          final AtomicLong requested;
  
          static final Object NEXT_WINDOW = new Object();
  
          volatile boolean done;
  
          UnicastProcessor<T> window;
  
          long emitted;
  
          WindowBoundaryMainSubscriber(Subscriber<? super Flowable<T>> downstream, int capacityHint) {
              this.downstream = downstream;
              this.capacityHint = capacityHint;
              this.boundarySubscriber = new WindowBoundaryInnerSubscriber<>(this);
              this.upstream = new AtomicReference<>();
              this.windows = new AtomicInteger(1);
              this.queue = new MpscLinkedQueue<>();
              this.errors = new AtomicThrowable();
              this.stopWindows = new AtomicBoolean();
              this.requested = new AtomicLong();
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              SubscriptionHelper.setOnce(upstream, s, Long.MAX_VALUE);
          }
  
          @Override
          public void onNext(T t) {
              queue.offer(t);
              drain();
          }
  
          @Override
          public void onError(Throwable e) {
              boundarySubscriber.dispose();
              if (errors.tryAddThrowableOrReport(e)) {
                  done = true;
                  drain();
              }
          }
  
          @Override
          public void onComplete() {
              boundarySubscriber.dispose();
              done = true;
              drain();
          }
  
          @Override
          public void cancel() {
              if (stopWindows.compareAndSet(false, true)) {
                  boundarySubscriber.dispose();
                  if (windows.decrementAndGet() == 0) {
                      SubscriptionHelper.cancel(upstream);
                  }
              }
          }
  
          @Override
          public void request(long n) {
              BackpressureHelper.add(requested, n);
          }
  
          @Override
          public void run() {
              if (windows.decrementAndGet() == 0) {
                  SubscriptionHelper.cancel(upstream);
              }
          }
  
          void innerNext() {
              queue.offer(NEXT_WINDOW);
              drain();
          }
  
          void innerError(Throwable e) {
              SubscriptionHelper.cancel(upstream);
              if (errors.tryAddThrowableOrReport(e)) {
                  done = true;
                  drain();
              }
          }
  
          void innerComplete() {
              SubscriptionHelper.cancel(upstream);
              done = true;
              drain();
          }
  
          @SuppressWarnings("unchecked")
          void drain() {
              if (getAndIncrement() != 0) {
                  return;
              }
  
              int missed = 1;
              Subscriber<? super Flowable<T>> downstream = this.downstream;
              MpscLinkedQueue<Object> queue = this.queue;
              AtomicThrowable errors = this.errors;
              long emitted = this.emitted;
  
              for (;;) {
  
                  for (;;) {
                      if (windows.get() == 0) {
                          queue.clear();
                          window = null;
                          return;
                      }
  
                      UnicastProcessor<T> w = window;
  
                      boolean d = done;
  
                      if (d && errors.get() != null) {
                          queue.clear();
                          Throwable ex = errors.terminate();
                          if (w != null) {
                              window = null;
                              w.onError(ex);
                          }
                          downstream.onError(ex);
                          return;
                      }
  
                      Object v = queue.poll();
  
                      boolean empty = v == null;
  
                      if (d && empty) {
                          Throwable ex = errors.terminate();
                          if (ex == null) {
                              if (w != null) {
                                  window = null;
                                  w.onComplete();
                              }
                              downstream.onComplete();
                          } else {
                              if (w != null) {
                                  window = null;
                                  w.onError(ex);
                              }
                              downstream.onError(ex);
                          }
                          return;
                      }
  
                      if (empty) {
                          break;
                      }
  
                      if (v != NEXT_WINDOW) {
                          w.onNext((T)v);
                          continue;
                      }
  
                      if (w != null) {
                          window = null;
                          w.onComplete();
                      }
  
                      if (!stopWindows.get()) {
                          w = UnicastProcessor.create(capacityHint, this);
                          window = w;
                          windows.getAndIncrement();
  
                          if (emitted != requested.get()) {
                              emitted++;
                              FlowableWindowSubscribeIntercept<T> intercept = new FlowableWindowSubscribeIntercept<>(w);
                              downstream.onNext(intercept);
                              if (intercept.tryAbandon()) {
                                  w.onComplete();
                              }
                          } else {
                              SubscriptionHelper.cancel(upstream);
                              boundarySubscriber.dispose();
                              errors.tryAddThrowableOrReport(MissingBackpressureException.createDefault());
                              done = true;
                          }
                      }
                  }
  
                  this.emitted = emitted;
                  missed = addAndGet(-missed);
                  if (missed == 0) {
                      break;
                  }
              }
          }
      }
  
      static final class WindowBoundaryInnerSubscriber<T, B> extends DisposableSubscriber<B> {
  
          final WindowBoundaryMainSubscriber<T, B> parent;
  
          boolean done;
  
          WindowBoundaryInnerSubscriber(WindowBoundaryMainSubscriber<T, B> parent) {
              this.parent = parent;
          }
  
          @Override
          public void onNext(B t) {
              if (done) {
                  return;
              }
              parent.innerNext();
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaPlugins.onError(t);
                  return;
              }
              done = true;
              parent.innerError(t);
          }
  
          @Override
          public void onComplete() {
              if (done) {
                  return;
              }
              done = true;
              parent.innerComplete();
          }
      }
  }
  