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.Collection;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Supplier;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.internal.functions.Functions;
  import io.reactivex.rxjava3.internal.fuseable.FuseToObservable;
  import io.reactivex.rxjava3.internal.util.ExceptionHelper;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  public final class ObservableToListSingle<T, U extends Collection<? super T>>
  extends Single<U> implements FuseToObservable<U> {
  
      final ObservableSource<T> source;
  
      final Supplier<U> collectionSupplier;
  
      @SuppressWarnings({ "unchecked", "rawtypes" })
      public ObservableToListSingle(ObservableSource<T> source, final int defaultCapacityHint) {
          this.source = source;
          this.collectionSupplier = (Supplier)Functions.createArrayList(defaultCapacityHint);
      }
  
      public ObservableToListSingle(ObservableSource<T> source, Supplier<U> collectionSupplier) {
          this.source = source;
          this.collectionSupplier = collectionSupplier;
      }
  
      @Override
      public void subscribeActual(SingleObserver<? super U> t) {
          U coll;
          try {
              coll = ExceptionHelper.nullCheck(collectionSupplier.get(), "The collectionSupplier returned a null Collection.");
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              EmptyDisposable.error(e, t);
              return;
          }
          source.subscribe(new ToListObserver<>(t, coll));
      }
  
      @Override
      public Observable<U> fuseToObservable() {
          return RxJavaPlugins.onAssembly(new ObservableToList<>(source, collectionSupplier));
      }
  
      static final class ToListObserver<T, U extends Collection<? super T>> implements Observer<T>, Disposable {
          final SingleObserver<? super U> downstream;
  
          U collection;
  
          Disposable upstream;
  
          ToListObserver(SingleObserver<? super U> actual, U collection) {
              this.downstream = actual;
              this.collection = collection;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void dispose() {
              upstream.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
  
          @Override
          public void onNext(T t) {
              collection.add(t);
          }
  
          @Override
          public void onError(Throwable t) {
              collection = null;
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              U c = collection;
              collection = null;
              downstream.onSuccess(c);
          }
      }
  }
  