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.observers;

import java.util.concurrent.atomic.AtomicReference;

import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.util.QueueDrainHelper;

Subscriber that can fuse with the upstream and calls a support interface
whenever an event is available.
Type parameters:
<T> – the value type/**
 * Subscriber that can fuse with the upstream and calls a support interface
 * whenever an event is available.
 *
 * @param <T> the value type
 */
public final class InnerQueuedObserver<T>
extends AtomicReference<Disposable>
implements Observer<T>, Disposable {

    private static final long serialVersionUID = -5417183359794346637L;

    final InnerQueuedObserverSupport<T> parent;

    final int prefetch;

    SimpleQueue<T> queue;

    volatile boolean done;

    int fusionMode;

    public InnerQueuedObserver(InnerQueuedObserverSupport<T> parent, int prefetch) {
        this.parent = parent;
        this.prefetch = prefetch;
    }

    @Override
    public void onSubscribe(Disposable d) {
        if (DisposableHelper.setOnce(this, d)) {
            if (d instanceof QueueDisposable) {
                @SuppressWarnings("unchecked")
                QueueDisposable<T> qd = (QueueDisposable<T>) d;

                int m = qd.requestFusion(QueueDisposable.ANY);
                if (m == QueueSubscription.SYNC) {
                    fusionMode = m;
                    queue = qd;
                    done = true;
                    parent.innerComplete(this);
                    return;
                }
                if (m == QueueDisposable.ASYNC) {
                    fusionMode = m;
                    queue = qd;
                    return;
                }
            }

            queue = QueueDrainHelper.createQueue(-prefetch);
        }
    }

    @Override
    public void onNext(T t) {
        if (fusionMode == QueueDisposable.NONE) {
            parent.innerNext(this, t);
        } else {
            parent.drain();
        }
    }

    @Override
    public void onError(Throwable t) {
        parent.innerError(this, t);
    }

    @Override
    public void onComplete() {
        parent.innerComplete(this);
    }

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

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

    public boolean isDone() {
        return done;
    }

    public void setDone() {
        this.done = true;
    }

    public SimpleQueue<T> queue() {
        return queue;
    }

    public int fusionMode() {
        return fusionMode;
    }
}