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 io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;

Signals the onSuccess, onError or onComplete events on a the specific scheduler.
Type parameters:
<T> – the value type delivered/**
 * Signals the onSuccess, onError or onComplete events on a the specific scheduler.
 *
 * @param <T> the value type delivered
 */
public final class MaybeObserveOn<T> extends AbstractMaybeWithUpstream<T, T> {

    final Scheduler scheduler;

    public MaybeObserveOn(MaybeSource<T> source, Scheduler scheduler) {
        super(source);
        this.scheduler = scheduler;
    }

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

    static final class ObserveOnMaybeObserver<T>
    extends AtomicReference<Disposable>
    implements MaybeObserver<T>, Disposable, Runnable {

        private static final long serialVersionUID = 8571289934935992137L;

        final MaybeObserver<? super T> downstream;

        final Scheduler scheduler;

        T value;
        Throwable error;

        ObserveOnMaybeObserver(MaybeObserver<? super T> actual, Scheduler scheduler) {
            this.downstream = actual;
            this.scheduler = scheduler;
        }

        @Override
        public void dispose() {
            DisposableHelper.dispose(this);
        }

        @Override
        public boolean isDisposed() {
            return DisposableHelper.isDisposed(get());
        }

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

        @Override
        public void onSuccess(T value) {
            this.value = value;
            DisposableHelper.replace(this, scheduler.scheduleDirect(this));
        }

        @Override
        public void onError(Throwable e) {
            this.error = e;
            DisposableHelper.replace(this, scheduler.scheduleDirect(this));
        }

        @Override
        public void onComplete() {
            DisposableHelper.replace(this, scheduler.scheduleDirect(this));
        }

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