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.AtomicBoolean;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;

public final class ObservableTakeLastTimed<T> extends AbstractObservableWithUpstream<T, T> {
    final long count;
    final long time;
    final TimeUnit unit;
    final Scheduler scheduler;
    final int bufferSize;
    final boolean delayError;

    public ObservableTakeLastTimed(ObservableSource<T> source,
            long count, long time, TimeUnit unit, Scheduler scheduler, int bufferSize, boolean delayError) {
        super(source);
        this.count = count;
        this.time = time;
        this.unit = unit;
        this.scheduler = scheduler;
        this.bufferSize = bufferSize;
        this.delayError = delayError;
    }

    @Override
    public void subscribeActual(Observer<? super T> t) {
        source.subscribe(new TakeLastTimedObserver<T>(t, count, time, unit, scheduler, bufferSize, delayError));
    }

    static final class TakeLastTimedObserver<T>
    extends AtomicBoolean implements Observer<T>, Disposable {

        private static final long serialVersionUID = -5677354903406201275L;
        final Observer<? super T> downstream;
        final long count;
        final long time;
        final TimeUnit unit;
        final Scheduler scheduler;
        final SpscLinkedArrayQueue<Object> queue;
        final boolean delayError;

        Disposable upstream;

        volatile boolean cancelled;

        Throwable error;

        TakeLastTimedObserver(Observer<? super T> actual, long count, long time, TimeUnit unit, Scheduler scheduler, int bufferSize, boolean delayError) {
            this.downstream = actual;
            this.count = count;
            this.time = time;
            this.unit = unit;
            this.scheduler = scheduler;
            this.queue = new SpscLinkedArrayQueue<Object>(bufferSize);
            this.delayError = delayError;
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;
                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T t) {
            final SpscLinkedArrayQueue<Object> q = queue;

            long now = scheduler.now(unit);
            long time = this.time;
            long c = count;
            boolean unbounded = c == Long.MAX_VALUE;

            q.offer(now, t);

            while (!q.isEmpty()) {
                long ts = (Long)q.peek();
                if (ts <= now - time || (!unbounded && (q.size() >> 1) > c)) {
                    q.poll();
                    q.poll();
                } else {
                    break;
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            error = t;
            drain();
        }

        @Override
        public void onComplete() {
            drain();
        }

        @Override
        public void dispose() {
            if (!cancelled) {
                cancelled = true;
                upstream.dispose();

                if (compareAndSet(false, true)) {
                    queue.clear();
                }
            }
        }

        @Override
        public boolean isDisposed() {
            return cancelled;
        }

        void drain() {
            if (!compareAndSet(false, true)) {
                return;
            }

            final Observer<? super T> a = downstream;
            final SpscLinkedArrayQueue<Object> q = queue;
            final boolean delayError = this.delayError;

            for (;;) {
                if (cancelled) {
                    q.clear();
                    return;
                }

                if (!delayError) {
                    Throwable ex = error;
                    if (ex != null) {
                        q.clear();
                        a.onError(ex);
                        return;
                    }
                }

                Object ts = q.poll(); // the timestamp long
                boolean empty = ts == null;

                if (empty) {
                    Throwable ex = error;
                    if (ex != null) {
                        a.onError(ex);
                    } else {
                        a.onComplete();
                    }
                    return;
                }

                @SuppressWarnings("unchecked")
                T o = (T)q.poll();

                if ((Long)ts < scheduler.now(unit) - time) {
                    continue;
                }

                a.onNext(o);
            }
        }
    }
}