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/*
 * Copyright (c) 2016-2021 VMware Inc. or its affiliates, 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
 *
 *   https://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.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.stream.Stream;

import org.reactivestreams.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Scannable;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;

/**
 * Relays values from the main Publisher until another Publisher signals an event.
 *
 * @param  the value type of the main Publisher
 * @param  the value type of the other Publisher
 * @see Reactive-Streams-Commons
 */
final class FluxTakeUntilOther extends InternalFluxOperator {

	final Publisher other;

	FluxTakeUntilOther(Flux source, Publisher other) {
		super(source);
		this.other = Objects.requireNonNull(other, "other");
	}

	@Override
	public int getPrefetch() {
		return Integer.MAX_VALUE;
	}

	@Override
	public CoreSubscriber subscribeOrReturn(CoreSubscriber actual) {
		TakeUntilMainSubscriber mainSubscriber = new TakeUntilMainSubscriber<>(actual);

		TakeUntilOtherSubscriber otherSubscriber = new TakeUntilOtherSubscriber<>(mainSubscriber);

		other.subscribe(otherSubscriber);

		return mainSubscriber;
	}

	@Override
	public Object scanUnsafe(Attr key) {
		if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
		return super.scanUnsafe(key);
	}

	static final class TakeUntilOtherSubscriber implements InnerConsumer {
		final TakeUntilMainSubscriber main;

		boolean once;

		TakeUntilOtherSubscriber(TakeUntilMainSubscriber main) {
			this.main = main;
		}

		@Override
		public Context currentContext() {
			return main.currentContext();
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.CANCELLED) return main.other == Operators.cancelledSubscription();
			if (key == Attr.PARENT) return main.other;
			if (key == Attr.ACTUAL) return main;
			if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;

			return null;
		}

		@Override
		public void onSubscribe(Subscription s) {
			main.setOther(s);

			s.request(Long.MAX_VALUE);
		}

		@Override
		public void onNext(U t) {
			onComplete();
		}

		@Override
		public void onError(Throwable t) {
			if (once) {
				return;
			}
			once = true;
			main.onError(t);
		}

		@Override
		public void onComplete() {
			if (once) {
				return;
			}
			once = true;
			main.onComplete();
		}
	}

	static final class TakeUntilMainSubscriber implements InnerOperator {

		final CoreSubscriber actual;

		volatile Subscription       main;

		@SuppressWarnings("rawtypes")
		static final AtomicReferenceFieldUpdater MAIN =
		  AtomicReferenceFieldUpdater.newUpdater(TakeUntilMainSubscriber.class, Subscription.class, "main");

		volatile Subscription other;
		@SuppressWarnings("rawtypes")
		static final AtomicReferenceFieldUpdater OTHER =
		  AtomicReferenceFieldUpdater.newUpdater(TakeUntilMainSubscriber.class, Subscription.class, "other");

		TakeUntilMainSubscriber(CoreSubscriber actual) {
			this.actual = Operators.serialize(actual);
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.PARENT) return main;
			if (key == Attr.CANCELLED) return main == Operators.cancelledSubscription();
			if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;

			return InnerOperator.super.scanUnsafe(key);
		}

		@Override
		public final CoreSubscriber actual() {
			return actual;
		}

		@Override
		public Stream inners() {
			return Stream.of(Scannable.from(other));
		}

		void setOther(Subscription s) {
			if (!OTHER.compareAndSet(this, null, s)) {
				s.cancel();
				if (other != Operators.cancelledSubscription()) {
					Operators.reportSubscriptionSet();
				}
			}
		}

		@Override
		public void request(long n) {
			main.request(n);
		}

		void cancelMain() {
			Subscription s = main;
			if (s != Operators.cancelledSubscription()) {
				s = MAIN.getAndSet(this, Operators.cancelledSubscription());
				if (s != null && s != Operators.cancelledSubscription()) {
					s.cancel();
				}
			}
		}

		void cancelOther() {
			Subscription s = other;
			if (s != Operators.cancelledSubscription()) {
				s = OTHER.getAndSet(this, Operators.cancelledSubscription());
				if (s != null && s != Operators.cancelledSubscription()) {
					s.cancel();
				}
			}
		}

		@Override
		public void cancel() {
			cancelMain();
			cancelOther();
		}

		@Override
		public void onSubscribe(Subscription s) {
			if (!MAIN.compareAndSet(this, null, s)) {
				s.cancel();
				if (main != Operators.cancelledSubscription()) {
					Operators.reportSubscriptionSet();
				}
			} else {
				actual.onSubscribe(this);
			}
		}

		@Override
		public void onNext(T t) {
			actual.onNext(t);
		}

		@Override
		public void onError(Throwable t) {

			if (main == null) {
				if (MAIN.compareAndSet(this, null, Operators.cancelledSubscription())) {
					Operators.error(actual, t);
					return;
				}
			}
			cancel();

			actual.onError(t);
		}

		@Override
		public void onComplete() {
			if (main == null) {
				if (MAIN.compareAndSet(this, null, Operators.cancelledSubscription())) {
					cancelOther();
					Operators.complete(actual);
					return;
				}
			}
			cancel();

			actual.onComplete();
		}
	}
}