/*
* 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 java.util.function.
BiFunction;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.core.
Fuseable;
import reactor.util.annotation.
Nullable;
/**
* Aggregates the source items with an aggregator function and returns the last result.
*
* @param <T> the input and output value type
*
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
MonoReduce<T> extends
MonoFromFluxOperator<T, T>
implements
Fuseable {
final
BiFunction<T, T, T>
aggregator;
MonoReduce(
Flux<? extends T>
source,
BiFunction<T, T, T>
aggregator) {
super(
source);
this.
aggregator =
Objects.
requireNonNull(
aggregator, "aggregator");
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
source.
subscribe(new
ReduceSubscriber<>(
actual,
aggregator));
}
static final class
ReduceSubscriber<T> extends
Operators.
MonoSubscriber<T, T> {
final
BiFunction<T, T, T>
aggregator;
Subscription s;
T
result;
boolean
done;
ReduceSubscriber(
CoreSubscriber<? super T>
actual,
BiFunction<T, T, T>
aggregator) {
super(
actual);
this.
aggregator =
aggregator;
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
TERMINATED) return
done;
if (
key ==
Attr.
PARENT) return
s;
return super.scanUnsafe(
key);
}
@
Override
public void
onSubscribe(
Subscription s) {
if (
Operators.
validate(this.
s,
s)) {
this.
s =
s;
actual.
onSubscribe(this);
s.
request(
Long.
MAX_VALUE);
}
}
@
Override
public void
onNext(T
t) {
if (
done) {
Operators.
onNextDropped(
t,
actual.
currentContext());
return;
}
T
r =
result;
if (
r == null) {
result =
t;
}
else {
try {
r =
Objects.
requireNonNull(
aggregator.
apply(
r,
t),
"The aggregator returned a null value");
}
catch (
Throwable ex) {
result = null;
done = true;
actual.
onError(
Operators.
onOperatorError(
s,
ex,
t,
actual.
currentContext()));
return;
}
result =
r;
}
}
@
Override
public void
onError(
Throwable t) {
if (
done) {
Operators.
onErrorDropped(
t,
actual.
currentContext());
return;
}
done = true;
result = null;
actual.
onError(
t);
}
@
Override
public void
onComplete() {
if (
done) {
return;
}
done = true;
T
r =
result;
if (
r != null) {
complete(
r);
}
else {
actual.
onComplete();
}
}
@
Override
public void
cancel() {
super.cancel();
s.
cancel();
}
}
}