/*
* 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 java.util.function.Supplier;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.Fuseable;
/**
* Aggregates the source values with the help of an accumulator
* function and emits the the final accumulated value.
*
* @param <T> the source value type
* @param <R> the accumulated result type
*
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class MonoReduceSeed<T, R> extends MonoSource<T, R> implements Fuseable {
final Supplier<R> initialSupplier;
final BiFunction<R, ? super T, R> accumulator;
MonoReduceSeed(Flux<? extends T> source,
Supplier<R> initialSupplier,
BiFunction<R, ? super T, R> accumulator) {
super(source);
this.initialSupplier = Objects.requireNonNull(initialSupplier, "initialSupplier");
this.accumulator = Objects.requireNonNull(accumulator, "accumulator");
}
@Override
public void subscribe(Subscriber<? super R> s) {
R initialValue;
try {
initialValue = Objects.requireNonNull(initialSupplier.get(),
"The initial value supplied is null");
}
catch (Throwable e) {
Operators.error(s, Operators.onOperatorError(e));
return;
}
source.subscribe(new ReduceSeedSubscriber<>(s, accumulator, initialValue));
}
static final class ReduceSeedSubscriber<T, R> extends Operators.MonoSubscriber<T, R> {
final BiFunction<R, ? super T, R> accumulator;
Subscription s;
boolean done;
ReduceSeedSubscriber(Subscriber<? super R> actual,
BiFunction<R, ? super T, R> accumulator,
R value) {
super(actual);
this.accumulator = accumulator;
this.value = value;
}
@Override
public Object scan(Attr key) {
switch (key){
case TERMINATED:
return done;
case PARENT:
return s;
}
return super.scan(key);
}
@Override
public void cancel() {
super.cancel();
s.cancel();
}
@Override
public void setValue(R value) {
// value already saved
}
@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) {
R v;
try {
v = Objects.requireNonNull(accumulator.apply(value, t),
"The accumulator returned a null value");
}
catch (Throwable e) {
onError(Operators.onOperatorError(this, e, t));
return;
}
value = v;
}
@Override
public void onError(Throwable t) {
if (done) {
Operators.onErrorDropped(t);
return;
}
done = true;
actual.onError(t);
}
@Override
public void onComplete() {
if (done) {
return;
}
done = true;
complete(value);
}
}
}