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.*;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.BackpressureHelper;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.subscribers.SerializedSubscriber;

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

    public FlowableDebounceTimed(Flowable<T> source, long timeout, TimeUnit unit, Scheduler scheduler) {
        super(source);
        this.timeout = timeout;
        this.unit = unit;
        this.scheduler = scheduler;
    }

    @Override
    protected void subscribeActual(Subscriber<? super T> s) {
        source.subscribe(new DebounceTimedSubscriber<T>(
                new SerializedSubscriber<T>(s),
                timeout, unit, scheduler.createWorker()));
    }

    static final class DebounceTimedSubscriber<T> extends AtomicLong
    implements FlowableSubscriber<T>, Subscription {

        private static final long serialVersionUID = -9102637559663639004L;
        final Subscriber<? super T> downstream;
        final long timeout;
        final TimeUnit unit;
        final Scheduler.Worker worker;

        Subscription upstream;

        Disposable timer;

        volatile long index;

        boolean done;

        DebounceTimedSubscriber(Subscriber<? super T> actual, long timeout, TimeUnit unit, Worker worker) {
            this.downstream = actual;
            this.timeout = timeout;
            this.unit = unit;
            this.worker = worker;
        }

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

        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }
            long idx = index + 1;
            index = idx;

            Disposable d = timer;
            if (d != null) {
                d.dispose();
            }

            DebounceEmitter<T> de = new DebounceEmitter<T>(t, idx, this);
            timer = de;
            d = worker.schedule(de, timeout, unit);
            de.setResource(d);
        }

        @Override
        public void onError(Throwable t) {
            if (done) {
                RxJavaPlugins.onError(t);
                return;
            }
            done = true;
            Disposable d = timer;
            if (d != null) {
                d.dispose();
            }
            downstream.onError(t);
            worker.dispose();
        }

        @Override
        public void onComplete() {
            if (done) {
                return;
            }
            done = true;

            Disposable d = timer;
            if (d != null) {
                d.dispose();
            }

            @SuppressWarnings("unchecked")
            DebounceEmitter<T> de = (DebounceEmitter<T>)d;
            if (de != null) {
                de.emit();
            }

            downstream.onComplete();
            worker.dispose();
        }

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

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

        void emit(long idx, T t, DebounceEmitter<T> emitter) {
            if (idx == index) {
                long r = get();
                if (r != 0L) {
                    downstream.onNext(t);
                    BackpressureHelper.produced(this, 1);

                    emitter.dispose();
                } else {
                    cancel();
                    downstream.onError(new MissingBackpressureException("Could not deliver value due to lack of requests"));
                }
            }
        }
    }

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

        private static final long serialVersionUID = 6812032969491025141L;

        final T value;
        final long idx;
        final DebounceTimedSubscriber<T> parent;

        final AtomicBoolean once = new AtomicBoolean();

        DebounceEmitter(T value, long idx, DebounceTimedSubscriber<T> parent) {
            this.value = value;
            this.idx = idx;
            this.parent = parent;
        }

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

        void emit() {
            if (once.compareAndSet(false, true)) {
                parent.emit(idx, value, this);
            }
        }

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

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

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