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.observers;
  
  import io.reactivex.rxjava3.core.Observer;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  public final class DisposableLambdaObserver<T> implements Observer<T>, Disposable {
      final Observer<? super T> downstream;
      final Consumer<? super Disposable> onSubscribe;
      final Action onDispose;
  
      Disposable upstream;
  
      public DisposableLambdaObserver(Observer<? super T> actual,
              Consumer<? super Disposable> onSubscribe,
              Action onDispose) {
          this.downstream = actual;
          this.onSubscribe = onSubscribe;
          this.onDispose = onDispose;
      }
  
      @Override
      public void onSubscribe(Disposable d) {
          // this way, multiple calls to onSubscribe can show up in tests that use doOnSubscribe to validate behavior
          try {
              onSubscribe.accept(d);
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              d.dispose();
              this.upstream = DisposableHelper.DISPOSED;
              EmptyDisposable.error(e, downstream);
              return;
          }
          if (DisposableHelper.validate(this.upstream, d)) {
              this.upstream = d;
              downstream.onSubscribe(this);
          }
      }
  
      @Override
      public void onNext(T t) {
          downstream.onNext(t);
      }
  
      @Override
      public void onError(Throwable t) {
          if (upstream != DisposableHelper.DISPOSED) {
              upstream = DisposableHelper.DISPOSED;
              downstream.onError(t);
          } else {
              RxJavaPlugins.onError(t);
          }
      }
  
      @Override
      public void onComplete() {
          if (upstream != DisposableHelper.DISPOSED) {
              upstream = DisposableHelper.DISPOSED;
              downstream.onComplete();
          }
      }
  
      @Override
      public void dispose() {
          Disposable d = upstream;
          if (d != DisposableHelper.DISPOSED) {
              upstream = DisposableHelper.DISPOSED;
              try {
                  onDispose.run();
              } catch (Throwable e) {
                  Exceptions.throwIfFatal(e);
                  RxJavaPlugins.onError(e);
              }
              d.dispose();
          }
      }
  
      @Override
      public boolean isDisposed() {
          return upstream.isDisposed();
      }
  }
  