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.observable;
  
  import java.util.ArrayDeque;
  import java.util.concurrent.atomic.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.subjects.UnicastSubject;
  
  public final class ObservableWindow<T> extends AbstractObservableWithUpstream<T, Observable<T>> {
      final long count;
      final long skip;
      final int capacityHint;
  
      public ObservableWindow(ObservableSource<T> source, long count, long skip, int capacityHint) {
          super(source);
          this.count = count;
          this.skip = skip;
          this.capacityHint = capacityHint;
      }
  
      @Override
      public void subscribeActual(Observer<? super Observable<T>> t) {
          if (count == skip) {
              source.subscribe(new WindowExactObserver<>(t, count, capacityHint));
          } else {
              source.subscribe(new WindowSkipObserver<>(t, count, skip, capacityHint));
          }
      }
  
      static final class WindowExactObserver<T>
      extends AtomicInteger
      implements Observer<T>, Disposable, Runnable {
  
          private static final long serialVersionUID = -7481782523886138128L;
          final Observer<? super Observable<T>> downstream;
          final long count;
          final int capacityHint;
  
          final AtomicBoolean cancelled;
  
          long size;
  
          Disposable upstream;
  
          UnicastSubject<T> window;
  
          WindowExactObserver(Observer<? super Observable<T>> actual, long count, int capacityHint) {
              this.downstream = actual;
              this.count = count;
              this.capacityHint = capacityHint;
              this.cancelled = new AtomicBoolean();
              this.lazySet(1);
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T t) {
              UnicastSubject<T> w = window;
              ObservableWindowSubscribeIntercept<T> intercept = null;
              if (w == null && !cancelled.get()) {
                  getAndIncrement();
  
                  w = UnicastSubject.create(capacityHint, this);
                  window = w;
                  intercept = new ObservableWindowSubscribeIntercept<>(w);
                  downstream.onNext(intercept);
              }
  
              if (w != null) {
                  w.onNext(t);
  
                  if (++size >= count) {
                      size = 0;
                      window = null;
                      w.onComplete();
                  }
  
                  if (intercept != null && intercept.tryAbandon()) {
                      window = null;
                      w.onComplete();
                      w = null;
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              UnicastSubject<T> w = window;
              if (w != null) {
                  window = null;
                  w.onError(t);
              }
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              UnicastSubject<T> w = window;
              if (w != null) {
                  window = null;
                  w.onComplete();
              }
              downstream.onComplete();
          }
  
          @Override
          public void dispose() {
              if (cancelled.compareAndSet(false, true)) {
                  run();
              }
          }
  
          @Override
          public boolean isDisposed() {
              return cancelled.get();
          }
  
          @Override
          public void run() {
              if (decrementAndGet() == 0) {
                  upstream.dispose();
              }
          }
      }
  
      static final class WindowSkipObserver<T> extends AtomicInteger
      implements Observer<T>, Disposable, Runnable {
  
          private static final long serialVersionUID = 3366976432059579510L;
          final Observer<? super Observable<T>> downstream;
          final long count;
          final long skip;
          final int capacityHint;
          final ArrayDeque<UnicastSubject<T>> windows;
  
          final AtomicBoolean cancelled;
  
          long index;
  
          /** Counts how many elements were emitted to the very first window in windows. */
          long firstEmission;
  
          Disposable upstream;
  
          WindowSkipObserver(Observer<? super Observable<T>> actual, long count, long skip, int capacityHint) {
              this.downstream = actual;
              this.count = count;
              this.skip = skip;
              this.capacityHint = capacityHint;
              this.windows = new ArrayDeque<>();
              this.cancelled = new AtomicBoolean();
              this.lazySet(1);
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T t) {
              final ArrayDeque<UnicastSubject<T>> ws = windows;
  
              long i = index;
  
              long s = skip;
  
              ObservableWindowSubscribeIntercept<T> intercept = null;
  
              if (i % s == 0 && !cancelled.get()) {
                  getAndIncrement();
                  UnicastSubject<T> w = UnicastSubject.create(capacityHint, this);
                  intercept = new ObservableWindowSubscribeIntercept<>(w);
                  ws.offer(w);
                  downstream.onNext(intercept);
              }
  
              long c = firstEmission + 1;
  
              for (UnicastSubject<T> w : ws) {
                  w.onNext(t);
              }
  
              if (c >= count) {
                  ws.poll().onComplete();
                  if (ws.isEmpty() && cancelled.get()) {
                      return;
                  }
                  firstEmission = c - s;
              } else {
                  firstEmission = c;
              }
  
              index = i + 1;
  
              if (intercept != null && intercept.tryAbandon()) {
                  intercept.window.onComplete();
              }
          }
  
          @Override
          public void onError(Throwable t) {
              final ArrayDeque<UnicastSubject<T>> ws = windows;
              while (!ws.isEmpty()) {
                  ws.poll().onError(t);
              }
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              final ArrayDeque<UnicastSubject<T>> ws = windows;
              while (!ws.isEmpty()) {
                  ws.poll().onComplete();
              }
              downstream.onComplete();
          }
  
          @Override
          public void dispose() {
              if (cancelled.compareAndSet(false, true)) {
                  run();
              }
          }
  
          @Override
          public boolean isDisposed() {
              return cancelled.get();
          }
  
          @Override
          public void run() {
              if (decrementAndGet() == 0) {
                  upstream.dispose();
              }
          }
      }
  }
  