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.completable;

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

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

    final CompletableSource source;

    public CompletableToObservable(CompletableSource source) {
        this.source = source;
    }

    @Override
    protected void subscribeActual(Observer<? super T> observer) {
        source.subscribe(new ObserverCompletableObserver(observer));
    }

    static final class ObserverCompletableObserver extends BasicQueueDisposable<Void>
    implements CompletableObserver {

        final Observer<?> observer;

        Disposable upstream;

        ObserverCompletableObserver(Observer<?> observer) {
            this.observer = observer;
        }

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

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

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

        @Override
        public int requestFusion(int mode) {
            return mode & ASYNC;
        }

        @Override
        public Void poll() throws Exception {
            return null; // always empty
        }

        @Override
        public boolean isEmpty() {
            return true;
        }

        @Override
        public void clear() {
            // always empty
        }

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

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