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.single;

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

Wraps a Single and exposes it as an Observable.
Type parameters:
<T> – the value type/**
 * Wraps a Single and exposes it as an Observable.
 *
 * @param <T> the value type
 */
public final class SingleToObservable<T> extends Observable<T> {

    final SingleSource<? extends T> source;

    public SingleToObservable(SingleSource<? extends T> source) {
        this.source = source;
    }

    @Override
    public void subscribeActual(final Observer<? super T> observer) {
        source.subscribe(create(observer));
    }

    
Creates a SingleObserver wrapper around a Observer. 
History: 2.0.1 - experimental
Params:
downstream – the downstream Observer to talk to
Type parameters:
<T> – the value type
Returns:
the new SingleObserver instance
Since:
2.2/**
     * Creates a {@link SingleObserver} wrapper around a {@link Observer}.
     * <p>History: 2.0.1 - experimental
     * @param <T> the value type
     * @param downstream the downstream {@code Observer} to talk to
     * @return the new SingleObserver instance
     * @since 2.2
     */
    public static <T> SingleObserver<T> create(Observer<? super T> downstream) {
        return new SingleToObservableObserver<T>(downstream);
    }

    static final class SingleToObservableObserver<T>
    extends DeferredScalarDisposable<T>
    implements SingleObserver<T> {

        private static final long serialVersionUID = 3786543492451018833L;
        Disposable upstream;

        SingleToObservableObserver(Observer<? super T> downstream) {
            super(downstream);
        }

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            complete(value);
        }

        @Override
        public void onError(Throwable e) {
            error(e);
        }

        @Override
        public void dispose() {
            super.dispose();
            upstream.dispose();
        }

    }
}