/*
* 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.
NoSuchElementException;
import java.util.
Objects;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.core.
Fuseable;
import reactor.util.annotation.
Nullable;
/**
* Expects and emits a single item from the source or signals
* NoSuchElementException(or a default generated value) for empty source,
* IndexOutOfBoundsException for a multi-item source.
*
* @param <T> the value type
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
MonoSingle<T> extends
MonoFromFluxOperator<T, T>
implements
Fuseable {
final T
defaultValue;
final boolean
completeOnEmpty;
MonoSingle(
Flux<? extends T>
source) {
super(
source);
this.
defaultValue = null;
this.
completeOnEmpty = false;
}
MonoSingle(
Flux<? extends T>
source,
@
Nullable T
defaultValue,
boolean
completeOnEmpty) {
super(
source);
this.
defaultValue =
completeOnEmpty ?
defaultValue :
Objects.
requireNonNull(
defaultValue, "defaultValue");
this.
completeOnEmpty =
completeOnEmpty;
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
source.
subscribe(new
SingleSubscriber<>(
actual,
defaultValue,
completeOnEmpty));
}
static final class
SingleSubscriber<T> extends
Operators.
MonoSubscriber<T, T> {
@
Nullable
final T
defaultValue;
final boolean
completeOnEmpty;
Subscription s;
int
count;
boolean
done;
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
TERMINATED) return
done;
if (
key ==
Attr.
PARENT) return
s;
return super.scanUnsafe(
key);
}
SingleSubscriber(
CoreSubscriber<? super T>
actual,
@
Nullable T
defaultValue,
boolean
completeOnEmpty) {
super(
actual);
this.
defaultValue =
defaultValue;
this.
completeOnEmpty =
completeOnEmpty;
}
@
Override
public void
request(long
n) {
super.request(
n);
if (
n > 0L) {
s.
request(
Long.
MAX_VALUE);
}
}
@
Override
public void
cancel() {
super.cancel();
s.
cancel();
}
@
Override
public void
setValue(T
value) {
this.
value =
value;
}
@
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 (
done) {
Operators.
onNextDropped(
t,
actual.
currentContext());
return;
}
value =
t;
if (++
count > 1) {
cancel();
onError(new
IndexOutOfBoundsException("Source emitted more than one item"));
}
}
@
Override
public void
onError(
Throwable t) {
if (
done) {
Operators.
onErrorDropped(
t,
actual.
currentContext());
return;
}
done = true;
actual.
onError(
t);
}
@
Override
public void
onComplete() {
if (
done) {
return;
}
done = true;
int
c =
count;
if (
c == 0) {
if (
completeOnEmpty) {
actual.
onComplete();
return;
}
T
t =
defaultValue;
if (
t != null) {
complete(
t);
}
else {
actual.
onError(
Operators.
onOperatorError(this,
new
NoSuchElementException("Source was empty"),
actual.
currentContext()));
}
}
else if (
c == 1) {
complete(
value);
}
}
}
}