/**
* 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.observable;
import io.reactivex.*;
import io.reactivex.disposables.
Disposable;
import io.reactivex.exceptions.
Exceptions;
import io.reactivex.functions.
BiFunction;
import io.reactivex.internal.disposables.
DisposableHelper;
import io.reactivex.internal.functions.
ObjectHelper;
import io.reactivex.plugins.
RxJavaPlugins;
/**
* Reduce a sequence of values into a single value via an aggregator function and emit the final value or complete
* if the source is empty.
*
* @param <T> the source and result value type
*/
public final class
ObservableReduceMaybe<T> extends
Maybe<T> {
final
ObservableSource<T>
source;
final
BiFunction<T, T, T>
reducer;
public
ObservableReduceMaybe(
ObservableSource<T>
source,
BiFunction<T, T, T>
reducer) {
this.
source =
source;
this.
reducer =
reducer;
}
@
Override
protected void
subscribeActual(
MaybeObserver<? super T>
observer) {
source.
subscribe(new
ReduceObserver<T>(
observer,
reducer));
}
static final class
ReduceObserver<T> implements
Observer<T>,
Disposable {
final
MaybeObserver<? super T>
downstream;
final
BiFunction<T, T, T>
reducer;
boolean
done;
T
value;
Disposable upstream;
ReduceObserver(
MaybeObserver<? super T>
observer,
BiFunction<T, T, T>
reducer) {
this.
downstream =
observer;
this.
reducer =
reducer;
}
@
Override
public void
onSubscribe(
Disposable d) {
if (
DisposableHelper.
validate(this.
upstream,
d)) {
this.
upstream =
d;
downstream.
onSubscribe(this);
}
}
@
Override
public void
onNext(T
value) {
if (!
done) {
T
v = this.
value;
if (
v == null) {
this.
value =
value;
} else {
try {
this.
value =
ObjectHelper.
requireNonNull(
reducer.
apply(
v,
value), "The reducer returned a null value");
} catch (
Throwable ex) {
Exceptions.
throwIfFatal(
ex);
upstream.
dispose();
onError(
ex);
}
}
}
}
@
Override
public void
onError(
Throwable e) {
if (
done) {
RxJavaPlugins.
onError(
e);
return;
}
done = true;
value = null;
downstream.
onError(
e);
}
@
Override
public void
onComplete() {
if (
done) {
return;
}
done = true;
T
v =
value;
value = null;
if (
v != null) {
downstream.
onSuccess(
v);
} else {
downstream.
onComplete();
}
}
@
Override
public void
dispose() {
upstream.
dispose();
}
@
Override
public boolean
isDisposed() {
return
upstream.
isDisposed();
}
}
}