/**

* 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.rxjava3.flowable;

import java.util.*;

import java.util.concurrent.ConcurrentLinkedQueue;

import java.util.concurrent.atomic.AtomicLong;

import org.reactivestreams.*;

import io.reactivex.rxjava3.core.Flowable;

import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;

import io.reactivex.rxjava3.internal.util.BackpressureHelper;

/**

* Creates {@link Flowable} of a number of items followed by either an error or

* completion. Cancellation has no effect on preventing emissions until the

* currently outstanding requests have been met.

* @param <T> the value type

*/

public final class Burst<T> extends Flowable<T> {

final List<T> items;

final Throwable error;

Burst(Throwable error, List<T> items) {

if (items.isEmpty()) {

throw new IllegalArgumentException("items cannot be empty");

}

for (T item : items) {

if (item == null) {

throw new IllegalArgumentException("items cannot include null");

}

}

this.error = error;

this.items = items;

}

@Override

protected void subscribeActual(final Subscriber<? super T> subscriber) {

subscriber.onSubscribe(new BurstSubscription(subscriber));

}

public static <T> Builder<T> item(T item) {

return items(item);

}

@SafeVarargs

public static <T> Builder<T> items(T... items) {

return new Builder<>(Arrays.asList(items));

}

final class BurstSubscription implements Subscription {

private final Subscriber<? super T> subscriber;

final Queue<T> q = new ConcurrentLinkedQueue<>(items);

final AtomicLong requested = new AtomicLong();

volatile boolean cancelled;

BurstSubscription(Subscriber<? super T> subscriber) {

this.subscriber = subscriber;

}

@Override

public void request(long n) {

if (cancelled) {

// required by reactive-streams-jvm 3.6

return;

}

if (SubscriptionHelper.validate(n)) {

// just for testing, don't care about perf

// so no attempt made to reduce volatile reads

if (BackpressureHelper.add(requested, n) == 0) {

if (q.isEmpty()) {

return;

}

while (!q.isEmpty() && requested.get() > 0) {

T item = q.poll();

requested.decrementAndGet();

subscriber.onNext(item);

}

if (q.isEmpty()) {

if (error != null) {

subscriber.onError(error);

} else {

subscriber.onComplete();

}

}

}

}

}

@Override

public void cancel() {

cancelled = true;

}

}

public static final class Builder<T> {

private final List<T> items;

private Throwable error;

Builder(List<T> items) {

this.items = items;

}

public Flowable<T> error(Throwable e) {

this.error = e;

return create();

}

public Flowable<T> create() {

return new Burst<>(error, items);

}

}

}