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.maybe;

import java.util.concurrent.atomic.AtomicReference;

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.CompositeException;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.subscriptions.SubscriptionHelper;

Delay the emission of the main signal until the other signals an item or completes.
Type parameters:
<T> – the main value type
<U> – the other value type/**
 * Delay the emission of the main signal until the other signals an item or completes.
 * 
 * @param <T> the main value type
 * @param <U> the other value type
 */
public final class MaybeDelayOtherPublisher<T, U> extends AbstractMaybeWithUpstream<T, T> {

    final Publisher<U> other;

    public MaybeDelayOtherPublisher(MaybeSource<T> source, Publisher<U> other) {
        super(source);
        this.other = other;
    }

    @Override
    protected void subscribeActual(MaybeObserver<? super T> observer) {
        source.subscribe(new DelayMaybeObserver<T, U>(observer, other));
    }

    static final class DelayMaybeObserver<T, U>
    implements MaybeObserver<T>, Disposable {
        final OtherSubscriber<T> other;

        final Publisher<U> otherSource;

        Disposable upstream;

        DelayMaybeObserver(MaybeObserver<? super T> actual, Publisher<U> otherSource) {
            this.other = new OtherSubscriber<T>(actual);
            this.otherSource = otherSource;
        }

        @Override
        public void dispose() {
            upstream.dispose();
            upstream = DisposableHelper.DISPOSED;
            SubscriptionHelper.cancel(other);
        }

        @Override
        public boolean isDisposed() {
            return other.get() == SubscriptionHelper.CANCELLED;
        }

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

                other.downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            upstream = DisposableHelper.DISPOSED;
            other.value = value;
            subscribeNext();
        }

        @Override
        public void onError(Throwable e) {
            upstream = DisposableHelper.DISPOSED;
            other.error = e;
            subscribeNext();
        }

        @Override
        public void onComplete() {
            upstream = DisposableHelper.DISPOSED;
            subscribeNext();
        }

        void subscribeNext() {
            otherSource.subscribe(other);
        }
    }

    static final class OtherSubscriber<T> extends
    AtomicReference<Subscription>
    implements FlowableSubscriber<Object> {

        private static final long serialVersionUID = -1215060610805418006L;

        final MaybeObserver<? super T> downstream;

        T value;

        Throwable error;

        OtherSubscriber(MaybeObserver<? super T> downstream) {
            this.downstream = downstream;
        }

        @Override
        public void onSubscribe(Subscription s) {
            SubscriptionHelper.setOnce(this, s, Long.MAX_VALUE);
        }

        @Override
        public void onNext(Object t) {
            Subscription s = get();
            if (s != SubscriptionHelper.CANCELLED) {
                lazySet(SubscriptionHelper.CANCELLED);
                s.cancel();
                onComplete();
            }
        }

        @Override
        public void onError(Throwable t) {
            Throwable e = error;
            if (e == null) {
                downstream.onError(t);
            } else {
                downstream.onError(new CompositeException(e, t));
            }
        }

        @Override
        public void onComplete() {
            Throwable e = error;
            if (e != null) {
                downstream.onError(e);
            } else {
                T v = value;
                if (v != null) {
                    downstream.onSuccess(v);
                } else {
                    downstream.onComplete();
                }
            }
        }
    }
}