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.Scheduler.Worker;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.*;
import io.reactivex.observers.SerializedObserver;
import io.reactivex.plugins.RxJavaPlugins;

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

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

    @Override
    public void subscribeActual(Observer<? super T> t) {
        source.subscribe(new DebounceTimedObserver<T>(
                new SerializedObserver<T>(t),
                timeout, unit, scheduler.createWorker()));
    }

    static final class DebounceTimedObserver<T>
    implements Observer<T>, Disposable {
        final Observer<? super T> downstream;
        final long timeout;
        final TimeUnit unit;
        final Scheduler.Worker worker;

        Disposable upstream;

        Disposable timer;

        volatile long index;

        boolean done;

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

        @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;
            }
            Disposable d = timer;
            if (d != null) {
                d.dispose();
            }
            done = true;
            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.run();
            }
            downstream.onComplete();
            worker.dispose();
        }

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

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

        void emit(long idx, T t, DebounceEmitter<T> emitter) {
            if (idx == index) {
                downstream.onNext(t);
                emitter.dispose();
            }
        }
    }

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

        private static final long serialVersionUID = 6812032969491025141L;

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

        final AtomicBoolean once = new AtomicBoolean();

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

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