/*
 * Copyright (c) 2011-2019 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
 *
 *        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 org.reactivestreams.Subscriber;

import reactor.core.CoreSubscriber;
import reactor.core.Fuseable;

Hook into the Publisher.subscribe(Subscriber) of a Mono and execute a provided callback before calling Publisher.subscribe(Subscriber) directly with the CoreSubscriber. 
 Note that any exception thrown by the hook short circuit the subscription process and are forwarded to the Subscriber's Subscriber.onError(Throwable) method. 
Author:
Simon Baslé
Type parameters:
<T> – the value type/**
 * Hook into the {@link org.reactivestreams.Publisher#subscribe(Subscriber)} of a
 * {@link Mono} and execute a provided callback before calling
 * {@link org.reactivestreams.Publisher#subscribe(Subscriber)} directly with the
 * {@link CoreSubscriber}.
 *
 * <p>
 * Note that any exception thrown by the hook short circuit the subscription process and
 * are forwarded to the {@link Subscriber}'s {@link Subscriber#onError(Throwable)} method.
 *
 * @param <T> the value type
 * @author Simon Baslé
 */
final class MonoDoFirstFuseable<T> extends InternalMonoOperator<T, T> implements Fuseable {

	final Runnable onFirst;

	MonoDoFirstFuseable(Mono<? extends T> source, Runnable onFirst) {
		super(source);
		this.onFirst = onFirst;
	}

	@Override
	public CoreSubscriber<? super T> subscribeOrReturn(CoreSubscriber<? super T> actual) {
		onFirst.run();

		return actual;
	}

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