hu.akarnokd.asyncenum.AsyncRepeatWhen Maven / Gradle / Ivy
/*
* Copyright 2017 David Karnok
*
* 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 hu.akarnokd.asyncenum;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.function.*;
public class AsyncRepeatWhen implements AsyncEnumerable {
final AsyncEnumerable source;
final Supplier stateSupplier;
final Function> completer;
public AsyncRepeatWhen(AsyncEnumerable source, Supplier stateSupplier, Function> completer) {
this.source = source;
this.stateSupplier = stateSupplier;
this.completer = completer;
}
@Override
public AsyncEnumerator enumerator() {
return new RepeatWhenEnumerator<>(source, stateSupplier.get(), completer);
}
static final class RepeatWhenEnumerator
extends AtomicInteger
implements AsyncEnumerator, BiConsumer {
final AsyncEnumerable source;
final S state;
final Function> completer;
final AtomicReference> current;
T result;
CompletableFuture completable;
RepeatWhenEnumerator(AsyncEnumerable source, S state, Function> completer) {
this.source = source;
this.state = state;
this.completer = completer;
this.current = new AtomicReference<>(source.enumerator());
}
@Override
public CompletionStage moveNext() {
CompletableFuture cf = new CompletableFuture<>();
completable = cf;
nextItem();
return cf;
}
@Override
public T current() {
return result;
}
void nextItem() {
if (getAndIncrement() == 0) {
do {
current.get().moveNext().whenComplete(this);
} while (decrementAndGet() != 0);
}
}
@Override
public void cancel() {
AsyncEnumeratorHelper.cancel(current);
}
@Override
public void accept(Boolean aBoolean, Throwable throwable) {
if (throwable != null) {
result = null;
completable.completeExceptionally(throwable);
return;
}
if (aBoolean) {
result = current.getPlain().current();
completable.complete(true);
} else {
result = null;
completer.apply(state).whenComplete(this::acceptCompleter);
}
}
void acceptCompleter(Boolean shouldRepeat, Throwable throwable) {
if (throwable != null) {
result = null;
completable.completeExceptionally(throwable);
return;
}
if (shouldRepeat) {
if (AsyncEnumeratorHelper.replace(current, source.enumerator())) {
nextItem();
}
} else {
completable.complete(false);
}
}
}
}