/**
* 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.internal.operators.single;
import java.util.concurrent.atomic.
AtomicLong;
import java.util.concurrent.atomic.
AtomicReference;
import org.reactivestreams.
Publisher;
import org.reactivestreams.
Subscriber;
import org.reactivestreams.
Subscription;
import io.reactivex.
Flowable;
import io.reactivex.
FlowableSubscriber;
import io.reactivex.
Scheduler;
import io.reactivex.
SingleObserver;
import io.reactivex.
SingleSource;
import io.reactivex.disposables.
Disposable;
import io.reactivex.exceptions.
Exceptions;
import io.reactivex.functions.
Function;
import io.reactivex.internal.functions.
ObjectHelper;
import io.reactivex.internal.subscriptions.
SubscriptionHelper;
/**
* A Flowable that emits items based on applying a specified function to the item emitted by the
* source Single, where that function returns a Publisher.
* <p>
* <img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.flatMapPublisher.png" alt="">
* <dl>
* <dt><b>Backpressure:</b></dt>
* <dd>The returned {@code Flowable} honors the backpressure of the downstream consumer
* and the {@code Publisher} returned by the mapper function is expected to honor it as well.</dd>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code flatMapPublisher} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param <T> the source value type
* @param <R> the result value type
*
* @see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
* @since 2.1.15
*/
public final class
SingleFlatMapPublisher<T, R> extends
Flowable<R> {
final
SingleSource<T>
source;
final
Function<? super T, ? extends
Publisher<? extends R>>
mapper;
public
SingleFlatMapPublisher(
SingleSource<T>
source,
Function<? super T, ? extends
Publisher<? extends R>>
mapper) {
this.
source =
source;
this.
mapper =
mapper;
}
@
Override
protected void
subscribeActual(
Subscriber<? super R>
downstream) {
source.
subscribe(new
SingleFlatMapPublisherObserver<T, R>(
downstream,
mapper));
}
static final class
SingleFlatMapPublisherObserver<S, T> extends
AtomicLong
implements
SingleObserver<S>,
FlowableSubscriber<T>,
Subscription {
private static final long
serialVersionUID = 7759721921468635667L;
final
Subscriber<? super T>
downstream;
final
Function<? super S, ? extends
Publisher<? extends T>>
mapper;
final
AtomicReference<
Subscription>
parent;
Disposable disposable;
SingleFlatMapPublisherObserver(
Subscriber<? super T>
actual,
Function<? super S, ? extends
Publisher<? extends T>>
mapper) {
this.
downstream =
actual;
this.
mapper =
mapper;
this.
parent = new
AtomicReference<
Subscription>();
}
@
Override
public void
onSubscribe(
Disposable d) {
this.
disposable =
d;
downstream.
onSubscribe(this);
}
@
Override
public void
onSuccess(S
value) {
Publisher<? extends T>
f;
try {
f =
ObjectHelper.
requireNonNull(
mapper.
apply(
value), "the mapper returned a null Publisher");
} catch (
Throwable e) {
Exceptions.
throwIfFatal(
e);
downstream.
onError(
e);
return;
}
f.
subscribe(this);
}
@
Override
public void
onSubscribe(
Subscription s) {
SubscriptionHelper.
deferredSetOnce(
parent, this,
s);
}
@
Override
public void
onNext(T
t) {
downstream.
onNext(
t);
}
@
Override
public void
onComplete() {
downstream.
onComplete();
}
@
Override
public void
onError(
Throwable e) {
downstream.
onError(
e);
}
@
Override
public void
request(long
n) {
SubscriptionHelper.
deferredRequest(
parent, this,
n);
}
@
Override
public void
cancel() {
disposable.
dispose();
SubscriptionHelper.
cancel(
parent);
}
}
}