Copyright (c) 2016-present, RxJava Contributors.
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.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * 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 io.reactivex.internal.operators.mixed;

import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.subscriptions.SubscriptionHelper;

Maps the success value of a Maybe onto a Publisher and
relays its signals to the downstream subscriber.
Type parameters:
<T> – the success value type of the Maybe source
<R> – the result type of the Publisher and this operator
Since:
2.1.15/**
 * Maps the success value of a Maybe onto a Publisher and
 * relays its signals to the downstream subscriber.
 * 
 * @param <T> the success value type of the Maybe source
 * @param <R> the result type of the Publisher and this operator
 * @since 2.1.15
 */
public final class MaybeFlatMapPublisher<T, R> extends Flowable<R> {

    final MaybeSource<T> source;

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

    public MaybeFlatMapPublisher(MaybeSource<T> source,
            Function<? super T, ? extends Publisher<? extends R>> mapper) {
        this.source = source;
        this.mapper = mapper;
    }

    @Override
    protected void subscribeActual(Subscriber<? super R> s) {
        source.subscribe(new FlatMapPublisherSubscriber<T, R>(s, mapper));
    }

    static final class FlatMapPublisherSubscriber<T, R>
    extends AtomicReference<Subscription>
    implements FlowableSubscriber<R>, MaybeObserver<T>, Subscription {

        private static final long serialVersionUID = -8948264376121066672L;

        final Subscriber<? super R> downstream;

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

        Disposable upstream;

        final AtomicLong requested;

        FlatMapPublisherSubscriber(Subscriber<? super R> downstream, Function<? super T, ? extends Publisher<? extends R>> mapper) {
            this.downstream = downstream;
            this.mapper = mapper;
            this.requested = new AtomicLong();
        }

        @Override
        public void onNext(R t) {
            downstream.onNext(t);
        }

        @Override
        public void onError(Throwable t) {
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            downstream.onComplete();
        }

        @Override
        public void request(long n) {
            SubscriptionHelper.deferredRequest(this, requested, n);
        }

        @Override
        public void cancel() {
            upstream.dispose();
            SubscriptionHelper.cancel(this);
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(upstream, d)) {
                this.upstream = d;
                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T t) {
            Publisher<? extends R> p;

            try {
                p = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null Publisher");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                downstream.onError(ex);
                return;
            }

            p.subscribe(this);
        }

        @Override
        public void onSubscribe(Subscription s) {
            SubscriptionHelper.deferredSetOnce(this, requested, s);
        }
    }
}