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.exceptions.MissingBackpressureException;
import io.reactivex.internal.disposables.*;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.BackpressureHelper;
import io.reactivex.subscribers.SerializedSubscriber;

public final class FlowableSampleTimed<T> extends AbstractFlowableWithUpstream<T, T> {
    final long period;
    final TimeUnit unit;
    final Scheduler scheduler;

    final boolean emitLast;

    public FlowableSampleTimed(Flowable<T> source, long period, TimeUnit unit, Scheduler scheduler, boolean emitLast) {
        super(source);
        this.period = period;
        this.unit = unit;
        this.scheduler = scheduler;
        this.emitLast = emitLast;
    }

    @Override
    protected void subscribeActual(Subscriber<? super T> s) {
        SerializedSubscriber<T> serial = new SerializedSubscriber<T>(s);
        if (emitLast) {
            source.subscribe(new SampleTimedEmitLast<T>(serial, period, unit, scheduler));
        } else {
            source.subscribe(new SampleTimedNoLast<T>(serial, period, unit, scheduler));
        }
    }

    abstract static class SampleTimedSubscriber<T> extends AtomicReference<T> implements FlowableSubscriber<T>, Subscription, Runnable {

        private static final long serialVersionUID = -3517602651313910099L;

        final Subscriber<? super T> downstream;
        final long period;
        final TimeUnit unit;
        final Scheduler scheduler;

        final AtomicLong requested = new AtomicLong();

        final SequentialDisposable timer = new SequentialDisposable();

        Subscription upstream;

        SampleTimedSubscriber(Subscriber<? super T> actual, long period, TimeUnit unit, Scheduler scheduler) {
            this.downstream = actual;
            this.period = period;
            this.unit = unit;
            this.scheduler = scheduler;
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(this.upstream, s)) {
                this.upstream = s;
                downstream.onSubscribe(this);
                timer.replace(scheduler.schedulePeriodicallyDirect(this, period, period, unit));
                s.request(Long.MAX_VALUE);
            }
        }

        @Override
        public void onNext(T t) {
            lazySet(t);
        }

        @Override
        public void onError(Throwable t) {
            cancelTimer();
            downstream.onError(t);
        }

        @Override
        public void onComplete() {
            cancelTimer();
            complete();
        }

        void cancelTimer() {
            DisposableHelper.dispose(timer);
        }

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

        @Override
        public void cancel() {
            cancelTimer();
            upstream.cancel();
        }

        void emit() {
            T value = getAndSet(null);
            if (value != null) {
                long r = requested.get();
                if (r != 0L) {
                    downstream.onNext(value);
                    BackpressureHelper.produced(requested, 1);
                } else {
                    cancel();
                    downstream.onError(new MissingBackpressureException("Couldn't emit value due to lack of requests!"));
                }
            }
        }

        abstract void complete();
    }

    static final class SampleTimedNoLast<T> extends SampleTimedSubscriber<T> {

        private static final long serialVersionUID = -7139995637533111443L;

        SampleTimedNoLast(Subscriber<? super T> actual, long period, TimeUnit unit, Scheduler scheduler) {
            super(actual, period, unit, scheduler);
        }

        @Override
        void complete() {
            downstream.onComplete();
        }

        @Override
        public void run() {
            emit();
        }
    }

    static final class SampleTimedEmitLast<T> extends SampleTimedSubscriber<T> {

        private static final long serialVersionUID = -7139995637533111443L;

        final AtomicInteger wip;

        SampleTimedEmitLast(Subscriber<? super T> actual, long period, TimeUnit unit, Scheduler scheduler) {
            super(actual, period, unit, scheduler);
            this.wip = new AtomicInteger(1);
        }

        @Override
        void complete() {
            emit();
            if (wip.decrementAndGet() == 0) {
                downstream.onComplete();
            }
        }

        @Override
        public void run() {
            if (wip.incrementAndGet() == 2) {
                emit();
                if (wip.decrementAndGet() == 0) {
                    downstream.onComplete();
                }
            }
        }
    }
}