/*
 * Copyright 2013-2021 the original author or authors.
 *
 * 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 org.springframework.cloud.sleuth.instrument.reactor;

import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Fuseable;

/**
 * A {@link SpanSubscription} is a {@link Subscription} that fakes being {@link Fuseable}
 * (implementing {@link reactor.core.Fuseable.QueueSubscription} with default no-op
 * methods and always negotiating fusion to be {@link Fuseable#NONE}).
 *
 * @param <T> - type of the subscription
 * @author Marcin Grzejszczak
 */
interface SpanSubscription<T> extends Subscription, CoreSubscriber<T>, Fuseable.QueueSubscription<T> {

	@Override
	default T poll() {
		return null;
	}

	@Override
	default int requestFusion(int i) {
		return Fuseable.NONE; // always negotiate to no fusion
	}

	@Override
	default int size() {
		return 0;
	}

	@Override
	default boolean isEmpty() {
		return true;
	}

	@Override
	default void clear() {
		// NO-OP
	}

}
