/*
 * Copyright (c) 2011-2017 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
 *
 *       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 reactor.core.publisher;

import java.util.Iterator;
import java.util.Objects;
import java.util.Queue;
import java.util.concurrent.Callable;
import java.util.function.Function;
import java.util.function.Supplier;

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

Concatenates values from Iterable sequences generated via a mapper function.
Type parameters:
<T> – the input value type
<R> – the value type of the iterables and the result type
See Also:
Reactive-Streams-Commons/**
 * Concatenates values from Iterable sequences generated via a mapper function.
 *
 * @param <T> the input value type
 * @param <R> the value type of the iterables and the result type
 *
 * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
 */
final class MonoFlattenIterable<T, R> extends FluxFromMonoOperator<T, R>
		implements Fuseable {

	final Function<? super T, ? extends Iterable<? extends R>> mapper;

	final int prefetch;

	final Supplier<Queue<T>> queueSupplier;

	MonoFlattenIterable(Mono<? extends T> source,
			Function<? super T, ? extends Iterable<? extends R>> mapper,
			int prefetch,
			Supplier<Queue<T>> queueSupplier) {
		super(source);
		if (prefetch <= 0) {
			throw new IllegalArgumentException("prefetch > 0 required but it was " + prefetch);
		}
		this.mapper = Objects.requireNonNull(mapper, "mapper");
		this.prefetch = prefetch;
		this.queueSupplier = Objects.requireNonNull(queueSupplier, "queueSupplier");
	}

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

	@SuppressWarnings("unchecked")
	@Override
	public void subscribe(CoreSubscriber<? super R> actual) {
		if (source instanceof Callable) {
			T v;

			try {
				v = ((Callable<T>) source).call();
			}
			catch (Throwable ex) {
				Operators.error(actual, Operators.onOperatorError(ex,
						actual.currentContext()));
				return;
			}

			if (v == null) {
				Operators.complete(actual);
				return;
			}

			Iterator<? extends R> it;

			try {
				Iterable<? extends R> iter = mapper.apply(v);

				it = iter.iterator();
			}
			catch (Throwable ex) {
				Operators.error(actual, Operators.onOperatorError(ex,
						actual.currentContext()));
				return;
			}

			FluxIterable.subscribe(actual, it);

			return;
		}
		source.subscribe(new FluxFlattenIterable.FlattenIterableSubscriber<>(actual,
				mapper,
				prefetch,
				queueSupplier));
	}

}