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.mixed;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.internal.disposables.EmptyDisposable;
  import io.reactivex.rxjava3.internal.operators.maybe.MaybeToObservable;
  import io.reactivex.rxjava3.internal.operators.single.SingleToObservable;
  
  import java.util.Objects;
  
  /**
   * Utility class to extract a value from a scalar source reactive type,
   * map it to a 0-1 type then subscribe the output type's consumer to it,
   * saving on the overhead of the regular subscription channel.
   * <p>History: 2.1.11 - experimental
   * @since 2.2
   */
  final class ScalarXMapZHelper {
  
      private ScalarXMapZHelper() {
          throw new IllegalStateException("No instances!");
      }
  
      /**
       * Try subscribing to a {@link CompletableSource} mapped from
       * a scalar source (which implements {@link Supplier}).
       * @param <T> the upstream value type
       * @param source the source reactive type ({@code Flowable} or {@code Observable})
       *               possibly implementing {@link Supplier}.
       * @param mapper the function that turns the scalar upstream value into a
       *              {@link CompletableSource}
       * @param observer the consumer to subscribe to the mapped {@link CompletableSource}
       * @return true if a subscription did happen and the regular path should be skipped
       */
      static <T> boolean tryAsCompletable(Object source,
              Function<? super T, ? extends CompletableSource> mapper,
              CompletableObserver observer) {
          if (source instanceof Supplier) {
              @SuppressWarnings("unchecked")
              Supplier<T> supplier = (Supplier<T>) source;
              CompletableSource cs = null;
              try {
                  T item = supplier.get();
                  if (item != null) {
                      cs = Objects.requireNonNull(mapper.apply(item), "The mapper returned a null CompletableSource");
                  }
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  EmptyDisposable.error(ex, observer);
                  return true;
              }
  
              if (cs == null) {
                  EmptyDisposable.complete(observer);
              } else {
                  cs.subscribe(observer);
              }
              return true;
          }
          return false;
      }
  
      /**
       * Try subscribing to a {@link MaybeSource} mapped from
       * a scalar source (which implements {@link Supplier}).
       * @param <T> the upstream value type
       * @param <R> the downstream value type
       * @param source the source reactive type ({@code Flowable} or {@code Observable})
       *               possibly implementing {@link Supplier}.
       * @param mapper the function that turns the scalar upstream value into a
       *              {@link MaybeSource}
       * @param observer the consumer to subscribe to the mapped {@link MaybeSource}
       * @return true if a subscription did happen and the regular path should be skipped
       */
      static <T, R> boolean tryAsMaybe(Object source,
              Function<? super T, ? extends MaybeSource<? extends R>> mapper,
              Observer<? super R> observer) {
          if (source instanceof Supplier) {
              @SuppressWarnings("unchecked")
              Supplier<T> supplier = (Supplier<T>) source;
              MaybeSource<? extends R> cs = null;
              try {
                  T item = supplier.get();
                  if (item != null) {
                      cs = Objects.requireNonNull(mapper.apply(item), "The mapper returned a null MaybeSource");
                  }
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  EmptyDisposable.error(ex, observer);
                  return true;
              }
  
              if (cs == null) {
                  EmptyDisposable.complete(observer);
              } else {
                  cs.subscribe(MaybeToObservable.create(observer));
              }
              return true;
          }
          return false;
      }
  
      /**
       * Try subscribing to a {@link SingleSource} mapped from
       * a scalar source (which implements {@link Supplier}).
       * @param <T> the upstream value type
       * @param <R> the downstream value type
       * @param source the source reactive type ({@code Flowable} or {@code Observable})
       *               possibly implementing {@link Supplier}.
       * @param mapper the function that turns the scalar upstream value into a
       *              {@link SingleSource}
       * @param observer the consumer to subscribe to the mapped {@link SingleSource}
       * @return true if a subscription did happen and the regular path should be skipped
       */
      static <T, R> boolean tryAsSingle(Object source,
              Function<? super T, ? extends SingleSource<? extends R>> mapper,
              Observer<? super R> observer) {
          if (source instanceof Supplier) {
              @SuppressWarnings("unchecked")
              Supplier<T> supplier = (Supplier<T>) source;
              SingleSource<? extends R> cs = null;
              try {
                  T item = supplier.get();
                  if (item != null) {
                      cs = Objects.requireNonNull(mapper.apply(item), "The mapper returned a null SingleSource");
                  }
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  EmptyDisposable.error(ex, observer);
                  return true;
              }
  
              if (cs == null) {
                  EmptyDisposable.complete(observer);
              } else {
                  cs.subscribe(SingleToObservable.create(observer));
              }
              return true;
          }
          return false;
      }
  }
  