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.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.observers.SerializedObserver;

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

    final boolean emitLast;

    public ObservableSampleTimed(ObservableSource<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
    public void subscribeActual(Observer<? super T> t) {
        SerializedObserver<T> serial = new SerializedObserver<T>(t);
        if (emitLast) {
            source.subscribe(new SampleTimedEmitLast<T>(serial, period, unit, scheduler));
        } else {
            source.subscribe(new SampleTimedNoLast<T>(serial, period, unit, scheduler));
        }
    }

    abstract static class SampleTimedObserver<T> extends AtomicReference<T> implements Observer<T>, Disposable, Runnable {

        private static final long serialVersionUID = -3517602651313910099L;

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

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

        Disposable upstream;

        SampleTimedObserver(Observer<? 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(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;
                downstream.onSubscribe(this);

                Disposable task = scheduler.schedulePeriodicallyDirect(this, period, period, unit);
                DisposableHelper.replace(timer, task);
            }
        }

        @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 dispose() {
            cancelTimer();
            upstream.dispose();
        }

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

        void emit() {
            T value = getAndSet(null);
            if (value != null) {
                downstream.onNext(value);
            }
        }

        abstract void complete();
    }

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

        private static final long serialVersionUID = -7139995637533111443L;

        SampleTimedNoLast(Observer<? 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 SampleTimedObserver<T> {

        private static final long serialVersionUID = -7139995637533111443L;

        final AtomicInteger wip;

        SampleTimedEmitLast(Observer<? 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();
                }
            }
        }
    }
}