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.maybe;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Predicate;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  
  /**
   * Filters the upstream SingleSource via a predicate, returning the success item or completing if
   * the predicate returns false.
   *
   * @param <T> the upstream value type
   */
  public final class MaybeFilterSingle<T> extends Maybe<T> {
      final SingleSource<T> source;
  
      final Predicate<? super T> predicate;
  
      public MaybeFilterSingle(SingleSource<T> source, Predicate<? super T> predicate) {
          this.source = source;
          this.predicate = predicate;
      }
  
      @Override
      protected void subscribeActual(MaybeObserver<? super T> observer) {
          source.subscribe(new FilterMaybeObserver<>(observer, predicate));
      }
  
      static final class FilterMaybeObserver<T> implements SingleObserver<T>, Disposable {
  
          final MaybeObserver<? super T> downstream;
  
          final Predicate<? super T> predicate;
  
          Disposable upstream;
  
          FilterMaybeObserver(MaybeObserver<? super T> actual, Predicate<? super T> predicate) {
              this.downstream = actual;
              this.predicate = predicate;
          }
  
          @Override
          public void dispose() {
              Disposable d = this.upstream;
              this.upstream = DisposableHelper.DISPOSED;
              d.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(T value) {
              boolean b;
  
              try {
                  b = predicate.test(value);
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  downstream.onError(ex);
                  return;
              }
  
              if (b) {
                  downstream.onSuccess(value);
              } else {
                  downstream.onComplete();
              }
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
      }
  
  }
  