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.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.BackpressureHelper;

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

    public FlowableTakeLastTimed(Flowable<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
    protected void subscribeActual(Subscriber<? super T> s) {
        source.subscribe(new TakeLastTimedSubscriber<T>(s, count, time, unit, scheduler, bufferSize, delayError));
    }

    static final class TakeLastTimedSubscriber<T> extends AtomicInteger implements FlowableSubscriber<T>, Subscription {

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

        Subscription upstream;

        final AtomicLong requested = new AtomicLong();

        volatile boolean cancelled;

        volatile boolean done;
        Throwable error;

        TakeLastTimedSubscriber(Subscriber<? 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(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) {
            final SpscLinkedArrayQueue<Object> q = queue;

            long now = scheduler.now(unit);

            q.offer(now, t);

            trim(now, q);
        }

        @Override
        public void onError(Throwable t) {
            if (delayError) {
                trim(scheduler.now(unit), queue);
            }
            error = t;
            done = true;
            drain();
        }

        @Override
        public void onComplete() {
            trim(scheduler.now(unit), queue);
            done = true;
            drain();
        }

        void trim(long now, SpscLinkedArrayQueue<Object> q) {
            long time = this.time;
            long c = count;
            boolean unbounded = c == Long.MAX_VALUE;

            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 request(long n) {
            if (SubscriptionHelper.validate(n)) {
                BackpressureHelper.add(requested, n);
                drain();
            }
        }

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

                if (getAndIncrement() == 0) {
                    queue.clear();
                }
            }
        }

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            int missed = 1;

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

            for (;;) {

                if (done) {
                    boolean empty = q.isEmpty();

                    if (checkTerminated(empty, a, delayError)) {
                        return;
                    }

                    long r = requested.get();
                    long e = 0L;

                    for (;;) {
                        Object ts = q.peek(); // the timestamp long
                        empty = ts == null;

                        if (checkTerminated(empty, a, delayError)) {
                            return;
                        }

                        if (r == e) {
                            break;
                        }

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

                        a.onNext(o);

                        e++;
                    }

                    if (e != 0L) {
                        BackpressureHelper.produced(requested, e);
                    }
                }

                missed = addAndGet(-missed);
                if (missed == 0) {
                    break;
                }
            }
        }

        boolean checkTerminated(boolean empty, Subscriber<? super T> a, boolean delayError) {
            if (cancelled) {
                queue.clear();
                return true;
            }
            if (delayError) {
                if (empty) {
                    Throwable e = error;
                    if (e != null) {
                        a.onError(e);
                    } else {
                        a.onComplete();
                    }
                    return true;
                }
            } else {
                Throwable e = error;
                if (e != null) {
                    queue.clear();
                    a.onError(e);
                    return true;
                } else
                if (empty) {
                    a.onComplete();
                    return true;
                }
            }
            return false;
        }
    }
}