/*
* Copyright (c) 2011-2017 Pivotal Software Inc, All Rights Reserved.
*
* 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 reactor.core.publisher;
import java.util.
Objects;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.core.
Fuseable;
import reactor.util.annotation.
Nullable;
/**
* Emits a scalar value if the source sequence turns out to be empty.
*
* @param <T> the value type
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
FluxDefaultIfEmpty<T> extends
FluxOperator<T, T> {
final T
value;
FluxDefaultIfEmpty(
Flux<? extends T>
source, T
value) {
super(
source);
this.
value =
Objects.
requireNonNull(
value, "value");
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
source.
subscribe(new
DefaultIfEmptySubscriber<>(
actual,
value));
}
static final class
DefaultIfEmptySubscriber<T>
extends
Operators.
MonoSubscriber<T, T> {
Subscription s;
boolean
hasValue;
DefaultIfEmptySubscriber(
CoreSubscriber<? super T>
actual, T
value) {
super(
actual);
this.
value =
value;
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
s;
return super.scanUnsafe(
key);
}
@
Override
public void
request(long
n) {
super.request(
n);
s.
request(
n);
}
@
Override
public void
cancel() {
super.cancel();
s.
cancel();
}
@
Override
public void
onSubscribe(
Subscription s) {
if (
Operators.
validate(this.
s,
s)) {
this.
s =
s;
actual.
onSubscribe(this);
}
}
@
Override
public void
onNext(T
t) {
if (!
hasValue) {
hasValue = true;
}
actual.
onNext(
t);
}
@
Override
public void
onComplete() {
if (
hasValue) {
actual.
onComplete();
} else {
complete(
value);
}
}
@
Override
public void
setValue(T
value) {
// value is constant
}
@
Override
public int
requestFusion(int
requestedMode) {
return
Fuseable.
NONE; // prevent fusion because of the upstream
}
}
}