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.flowable;

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

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.Scheduler.Worker;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.MissingBackpressureException;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.schedulers.TrampolineScheduler;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.BackpressureHelper;

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

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

    @Override
    public void subscribeActual(Subscriber<? super Long> s) {
        IntervalSubscriber is = new IntervalSubscriber(s);
        s.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 IntervalSubscriber extends AtomicLong
    implements Subscription, Runnable {

        private static final long serialVersionUID = -2809475196591179431L;

        final Subscriber<? super Long> downstream;

        long count;

        final AtomicReference<Disposable> resource = new AtomicReference<Disposable>();

        IntervalSubscriber(Subscriber<? super Long> downstream) {
            this.downstream = downstream;
        }

        @Override
        public void request(long n) {
            if (SubscriptionHelper.validate(n)) {
                BackpressureHelper.add(this, n);
            }
        }

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

        @Override
        public void run() {
            if (resource.get() != DisposableHelper.DISPOSED) {
                long r = get();

                if (r != 0L) {
                    downstream.onNext(count++);
                    BackpressureHelper.produced(this, 1);
                } else {
                    downstream.onError(new MissingBackpressureException("Can't deliver value " + count + " due to lack of requests"));
                    DisposableHelper.dispose(resource);
                }
            }
        }

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