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.subscriptions;

import java.util.concurrent.atomic.*;

import org.reactivestreams.Subscription;

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

A subscription implementation that arbitrates exactly one other Subscription and can
hold a single disposable resource.
All methods are thread-safe.
/**
 * A subscription implementation that arbitrates exactly one other Subscription and can
 * hold a single disposable resource.
 *
 * <p>All methods are thread-safe.
 */
public final class AsyncSubscription extends AtomicLong implements Subscription, Disposable {

    private static final long serialVersionUID = 7028635084060361255L;

    final AtomicReference<Subscription> actual;

    final AtomicReference<Disposable> resource;

    public AsyncSubscription() {
        resource = new AtomicReference<Disposable>();
        actual = new AtomicReference<Subscription>();
    }

    public AsyncSubscription(Disposable resource) {
        this();
        this.resource.lazySet(resource);
    }

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

    @Override
    public void cancel() {
        dispose();
    }

    @Override
    public void dispose() {
        SubscriptionHelper.cancel(actual);
        DisposableHelper.dispose(resource);
    }

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

    
Sets a new resource and disposes the currently held resource.
Params:
r – the new resource to set
See Also:
replaceResource(Disposable)
Returns:
false if this AsyncSubscription has been cancelled/disposed/**
     * Sets a new resource and disposes the currently held resource.
     * @param r the new resource to set
     * @return false if this AsyncSubscription has been cancelled/disposed
     * @see #replaceResource(Disposable)
     */
    public boolean setResource(Disposable r) {
        return DisposableHelper.set(resource, r);
    }

    
Replaces the currently held resource with the given new one without disposing the old.
Params:
r – the new resource to set
Returns:
false if this AsyncSubscription has been cancelled/disposed/**
     * Replaces the currently held resource with the given new one without disposing the old.
     * @param r the new resource to set
     * @return false if this AsyncSubscription has been cancelled/disposed
     */
    public boolean replaceResource(Disposable r) {
        return DisposableHelper.replace(resource, r);
    }

    
Sets the given subscription if there isn't any subscription held.
Params:
s – the first and only subscription to set/**
     * Sets the given subscription if there isn't any subscription held.
     * @param s the first and only subscription to set
     */
    public void setSubscription(Subscription s) {
        SubscriptionHelper.deferredSetOnce(actual, this, s);
    }
}