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.observable;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

import io.reactivex.*;
import io.reactivex.Scheduler.Worker;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.*;
import io.reactivex.internal.schedulers.TrampolineScheduler;

public final class ObservableInterval extends Observable<Long> {
    final Scheduler scheduler;
    final long initialDelay;
    final long period;
    final TimeUnit unit;

    public ObservableInterval(long initialDelay, long period, TimeUnit unit, Scheduler scheduler) {
        this.initialDelay = initialDelay;
        this.period = period;
        this.unit = unit;
        this.scheduler = scheduler;
    }

    @Override
    public void subscribeActual(Observer<? super Long> observer) {
        IntervalObserver is = new IntervalObserver(observer);
        observer.onSubscribe(is);

        Scheduler sch = scheduler;

        if (sch instanceof TrampolineScheduler) {
            Worker worker = sch.createWorker();
            is.setResource(worker);
            worker.schedulePeriodically(is, initialDelay, period, unit);
        } else {
            Disposable d = sch.schedulePeriodicallyDirect(is, initialDelay, period, unit);
            is.setResource(d);
        }
    }

    static final class IntervalObserver
    extends AtomicReference<Disposable>
    implements Disposable, Runnable {

        private static final long serialVersionUID = 346773832286157679L;

        final Observer<? super Long> downstream;

        long count;

        IntervalObserver(Observer<? super Long> downstream) {
            this.downstream = downstream;
        }

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

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

        @Override
        public void run() {
            if (get() != DisposableHelper.DISPOSED) {
                downstream.onNext(count++);
            }
        }

        public void setResource(Disposable d) {
            DisposableHelper.setOnce(this, d);
        }
    }
}