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.Function;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  
  import java.util.Objects;
  
  /**
   * Maps the upstream success value into some other value.
   *
   * @param <T> the upstream value type
   * @param <R> the downstream value type
   */
  public final class MaybeMap<T, R> extends AbstractMaybeWithUpstream<T, R> {
  
      final Function<? super T, ? extends R> mapper;
  
      public MaybeMap(MaybeSource<T> source, Function<? super T, ? extends R> mapper) {
          super(source);
          this.mapper = mapper;
      }
  
      @Override
      protected void subscribeActual(MaybeObserver<? super R> observer) {
          source.subscribe(new MapMaybeObserver<T, R>(observer, mapper));
      }
  
      static final class MapMaybeObserver<T, R> implements MaybeObserver<T>, Disposable {
  
          final MaybeObserver<? super R> downstream;
  
          final Function<? super T, ? extends R> mapper;
  
          Disposable upstream;
  
          MapMaybeObserver(MaybeObserver<? super R> actual, Function<? super T, ? extends R> mapper) {
              this.downstream = actual;
              this.mapper = mapper;
          }
  
          @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) {
              R v;
  
              try {
                  v = Objects.requireNonNull(mapper.apply(value), "The mapper returned a null item");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  downstream.onError(ex);
                  return;
              }
  
              downstream.onSuccess(v);
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
  
          @Override
          public void onComplete() {
              downstream.onComplete();
          }
      }
  }
  