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.jdk8;
  
  import java.util.Objects;
  import java.util.function.*;
  import java.util.stream.Collector;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.internal.observers.DeferredScalarDisposable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Collect items into a container defined by a Stream {@link Collector} callback set.
   *
   * @param <T> the upstream value type
   * @param <A> the intermediate accumulator type
   * @param <R> the result type
   * @since 3.0.0
   */
  public final class ObservableCollectWithCollector<T, A, R> extends Observable<R> {
  
      final Observable<T> source;
  
      final Collector<? super T, A, R> collector;
  
      public ObservableCollectWithCollector(Observable<T> source, Collector<? super T, A, R> collector) {
          this.source = source;
          this.collector = collector;
      }
  
      @Override
      protected void subscribeActual(@NonNull Observer<? super R> observer) {
          A container;
          BiConsumer<A, ? super T> accumulator;
          Function<A, R> finisher;
  
          try {
              container = collector.supplier().get();
              accumulator = collector.accumulator();
              finisher = collector.finisher();
          } catch (Throwable ex) {
              Exceptions.throwIfFatal(ex);
              EmptyDisposable.error(ex, observer);
              return;
          }
  
          source.subscribe(new CollectorObserver<>(observer, container, accumulator, finisher));
      }
  
      static final class CollectorObserver<T, A, R>
      extends DeferredScalarDisposable<R>
      implements Observer<T> {
  
          private static final long serialVersionUID = -229544830565448758L;
  
          final BiConsumer<A, T> accumulator;
  
          final Function<A, R> finisher;
  
          Disposable upstream;
  
          boolean done;
  
          A container;
  
          CollectorObserver(Observer<? super R> downstream, A container, BiConsumer<A, T> accumulator, Function<A, R> finisher) {
              super(downstream);
              this.container = container;
              this.accumulator = accumulator;
              this.finisher = finisher;
          }
  
          @Override
          public void onSubscribe(@NonNull Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T t) {
              if (done) {
                  return;
              }
              try {
                  accumulator.accept(container, t);
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  upstream.dispose();
                  onError(ex);
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaPlugins.onError(t);
              } else {
                  done = true;
                  upstream = DisposableHelper.DISPOSED;
                  this.container = null;
                  downstream.onError(t);
              }
          }
  
          @Override
          public void onComplete() {
              if (done) {
                  return;
              }
  
              done = true;
              upstream = DisposableHelper.DISPOSED;
              A container = this.container;
              this.container = null;
              R result;
              try {
                  result = Objects.requireNonNull(finisher.apply(container), "The finisher returned a null value");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  downstream.onError(ex);
                  return;
              }
  
              complete(result);
          }
  
          @Override
          public void dispose() {
              super.dispose();
              upstream.dispose();
          }
      }
  }
  