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Easy Redis Java client and Real-Time Data Platform. Valkey compatible. Sync/Async/RxJava3/Reactive API. Client side caching. Over 50 Redis based Java objects and services: JCache API, Apache Tomcat, Hibernate, Spring, Set, Multimap, SortedSet, Map, List, Queue, Deque, Semaphore, Lock, AtomicLong, Map Reduce, Bloom filter, Scheduler, RPC

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/*
 * Copyright (c) 2016-2023 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.Comparator;

import reactor.core.CoreSubscriber;
import reactor.core.Scannable;
import reactor.util.annotation.Nullable;

/**
 * Merges the individual 'rails' of the source {@link ParallelFlux} assuming a total order
 * of the values, by picking the smallest available value from each rail, resulting in
 * a single regular Publisher sequence (exposed as a {@link Flux}).
 *
 * @param  the value type
 * @author Simon Baslé
 */
final class ParallelMergeOrdered extends Flux implements Scannable {

	final ParallelFlux source;
	final int                       prefetch;
	final Comparator     valueComparator;

	ParallelMergeOrdered(ParallelFlux source, int prefetch,
			Comparator valueComparator) {
		if (prefetch <= 0) {
			throw new IllegalArgumentException("prefetch > 0 required but it was " + prefetch);
		}
		this.source = ParallelFlux.from(source);
		this.prefetch = prefetch;
		this.valueComparator = valueComparator;
	}

	@Override
	public int getPrefetch() {
		return prefetch;
	}

	@Override
	@Nullable
	public Object scanUnsafe(Attr key) {
		if (key == Attr.PARENT) return source;
		if (key == Attr.PREFETCH) return prefetch;
		if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
		if (key == InternalProducerAttr.INSTANCE) return true;

		return null;
	}

	@Override
	public void subscribe(CoreSubscriber actual) {
		FluxMergeComparing.MergeOrderedMainProducer
				main = new FluxMergeComparing.MergeOrderedMainProducer<>(actual, valueComparator, prefetch, source.parallelism(), true, true);
		actual.onSubscribe(main);
		source.subscribe(main.subscribers);
	}
}