/*
 * 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.rxjava3.internal.operators.flowable;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.*;

import org.reactivestreams.*;

import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
import io.reactivex.rxjava3.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<>(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<>(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;
        }
    }
}
