/*
 * Copyright (c) 2011-2017 Pivotal Software Inc, All Rights Reserved.
 *
 * 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
 *
 *       https://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 reactor.core.publisher;

import java.util.Objects;
import java.util.Queue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.stream.Stream;

import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;

import reactor.core.CoreSubscriber;
import reactor.core.Disposable;
import reactor.core.Disposables;
import reactor.core.Exceptions;
import reactor.core.Scannable;
import reactor.core.scheduler.Scheduler;
import reactor.util.concurrent.Queues;

Author:
David Karnok/**
 * @author David Karnok
 */
final class FluxWindowTimeout<T> extends InternalFluxOperator<T, Flux<T>> {

	final int            maxSize;
	final long           timespan;
	final TimeUnit       unit;
	final Scheduler      timer;

	FluxWindowTimeout(Flux<T> source, int maxSize, long timespan, TimeUnit unit, Scheduler timer) {
		super(source);
		if (timespan <= 0) {
			throw new IllegalArgumentException("Timeout period must be strictly positive");
		}
		if (maxSize <= 0) {
			throw new IllegalArgumentException("maxSize must be strictly positive");
		}
		this.timer = Objects.requireNonNull(timer, "Timer");
		this.timespan = timespan;
		this.unit = Objects.requireNonNull(unit, "unit");
		this.maxSize = maxSize;
	}

	@Override
	public CoreSubscriber<? super T> subscribeOrReturn(CoreSubscriber<? super Flux<T>> actual) {
		return new WindowTimeoutSubscriber<>(actual, maxSize,
				timespan, unit,
				timer);
	}

	@Override
	public Object scanUnsafe(Attr key) {
		if (key == Attr.RUN_ON) return timer;
		if (key == Attr.RUN_STYLE) return Attr.RunStyle.ASYNC;

		return super.scanUnsafe(key);
	}

	static final class WindowTimeoutSubscriber<T> implements InnerOperator<T, Flux<T>> {

		final CoreSubscriber<? super Flux<T>> actual;
		final long                            timespan;
		final TimeUnit                        unit;
		final Scheduler                       scheduler;
		final int                             maxSize;
		final Scheduler.Worker                worker;
		final Queue<Object>                   queue;

		Throwable error;
		volatile boolean done;
		volatile boolean cancelled;

		volatile long requested;
		@SuppressWarnings("rawtypes")
		static final AtomicLongFieldUpdater<WindowTimeoutSubscriber> REQUESTED =
				AtomicLongFieldUpdater.newUpdater(WindowTimeoutSubscriber.class,
						"requested");

		volatile int wip;
		@SuppressWarnings("rawtypes")
		static final AtomicIntegerFieldUpdater<WindowTimeoutSubscriber> WIP =
				AtomicIntegerFieldUpdater.newUpdater(WindowTimeoutSubscriber.class,
						"wip");

		int  count;
		long producerIndex;

		Subscription s;

		Sinks.Many<T> window;

		volatile boolean terminated;

		volatile     Disposable                                           timer;
		@SuppressWarnings("rawtypes")
		static final AtomicReferenceFieldUpdater<WindowTimeoutSubscriber, Disposable> TIMER =
				AtomicReferenceFieldUpdater.newUpdater(WindowTimeoutSubscriber.class, Disposable.class, "timer");

		WindowTimeoutSubscriber(CoreSubscriber<? super Flux<T>> actual,
				int maxSize,
				long timespan,
				TimeUnit unit,
				Scheduler scheduler) {
			this.actual = actual;
			this.queue = Queues.unboundedMultiproducer().get();
			this.timespan = timespan;
			this.unit = unit;
			this.scheduler = scheduler;
			this.maxSize = maxSize;
			this.worker = scheduler.createWorker();
		}

		@Override
		public CoreSubscriber<? super Flux<T>> actual() {
			return actual;
		}

		@Override
		public Stream<? extends Scannable> inners() {
			Sinks.Many<T> w = window;
			return w == null ? Stream.empty() : Stream.of(Scannable.from(w));
		}

		@Override
		public Object scanUnsafe(Attr key) {
			if (key == Attr.PARENT) return s;
			if (key == Attr.CANCELLED) return cancelled;
			if (key == Attr.TERMINATED) return done;
			if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return requested;
			if (key == Attr.CAPACITY) return maxSize;
			if (key == Attr.BUFFERED) return queue.size();
			if (key == Attr.RUN_ON) return worker;
			if (key == Attr.RUN_STYLE) return Attr.RunStyle.ASYNC;
			return InnerOperator.super.scanUnsafe(key);
		}

		@Override
		public void onSubscribe(Subscription s) {
			if (Operators.validate(this.s, s)) {
				this.s = s;

				Subscriber<? super Flux<T>> a = actual;

				a.onSubscribe(this);

				if (cancelled) {
					return;
				}

				Sinks.Many<T> w = Sinks.unsafe().many().unicast().onBackpressureBuffer();
				window = w;

				long r = requested;
				if (r != 0L) {
					a.onNext(w.asFlux());
					if (r != Long.MAX_VALUE) {
						REQUESTED.decrementAndGet(this);
					}
				}
				else {
					a.onError(Operators.onOperatorError(s,
							Exceptions.failWithOverflow(), actual.currentContext()));
					return;
				}

				if (OperatorDisposables.replace(TIMER, this, newPeriod())) {
					s.request(Long.MAX_VALUE);
				}
			}
		}

		Disposable newPeriod() {
			try {
				return worker.schedulePeriodically(new ConsumerIndexHolder(producerIndex,
						this), timespan, timespan, unit);
			}
			catch (Exception e) {
				actual.onError(Operators.onRejectedExecution(e, s, null, null, actual.currentContext()));
				return Disposables.disposed();
			}
		}

		@Override
		public void onNext(T t) {
			if (terminated) {
				return;
			}

			if (WIP.get(this) == 0 && WIP.compareAndSet(this, 0, 1)) {
				Sinks.Many<T> w = window;
				w.emitNext(t, Sinks.EmitFailureHandler.FAIL_FAST);

				int c = count + 1;

				if (c >= maxSize) {
					producerIndex++;
					count = 0;

					w.emitComplete(Sinks.EmitFailureHandler.FAIL_FAST);

					long r = requested;

					if (r != 0L) {
						w = Sinks.unsafe().many().unicast().onBackpressureBuffer();
						window = w;
						actual.onNext(w.asFlux());
						if (r != Long.MAX_VALUE) {
							REQUESTED.decrementAndGet(this);
						}

						Disposable tm = timer;
						tm.dispose();

						Disposable task = newPeriod();

						if (!TIMER.compareAndSet(this, tm, task)) {
							task.dispose();
						}
					}
					else {
						window = null;
						actual.onError(Operators.onOperatorError(s,
								Exceptions.failWithOverflow(), t, actual
										.currentContext()));
						timer.dispose();
						worker.dispose();
						return;
					}
				}
				else {
					count = c;
				}

				if (WIP.decrementAndGet(this) == 0) {
					return;
				}
			}
			else {
				queue.offer(t);
				if (!enter()) {
					return;
				}
			}
			drainLoop();
		}

		@Override
		public void onError(Throwable t) {
			error = t;
			done = true;
			if (enter()) {
				drainLoop();
			}

			actual.onError(t);
			timer.dispose();
			worker.dispose();
		}

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

			actual.onComplete();
			timer.dispose();
			worker.dispose();
		}

		@Override
		public void request(long n) {
			if(Operators.validate(n)) {
				Operators.addCap(REQUESTED, this, n);
			}
		}

		@Override
		public void cancel() {
			cancelled = true;
		}

		@SuppressWarnings("unchecked")
		void drainLoop() {
			final Queue<Object> q = queue;
			final Subscriber<? super Flux<T>> a = actual;
			Sinks.Many<T> w = window;

			int missed = 1;
			for (; ; ) {

				for (; ; ) {
					if (terminated) {
						s.cancel();
						q.clear();
						timer.dispose();
						worker.dispose();
						return;
					}

					boolean d = done;

					Object o = q.poll();

					boolean empty = o == null;
					boolean isHolder = o instanceof ConsumerIndexHolder;

					if (d && (empty || isHolder)) {
						window = null;
						q.clear();
						Throwable err = error;
						if (err != null) {
							w.emitError(err, Sinks.EmitFailureHandler.FAIL_FAST);
						}
						else {
							w.emitComplete(Sinks.EmitFailureHandler.FAIL_FAST);
						}
						timer.dispose();
						worker.dispose();
						return;
					}

					if (empty) {
						break;
					}

					if (isHolder) {
						w.emitComplete(Sinks.EmitFailureHandler.FAIL_FAST);
						count = 0;
						w = Sinks.unsafe().many().unicast().onBackpressureBuffer();
						window = w;

						long r = requested;
						if (r != 0L) {
							a.onNext(w.asFlux());
							if (r != Long.MAX_VALUE) {
								REQUESTED.decrementAndGet(this);
							}
						}
						else {
							window = null;
							queue.clear();
							a.onError(Operators.onOperatorError(s,
									Exceptions.failWithOverflow(), actual.currentContext()));
							timer.dispose();
							worker.dispose();
							return;
						}
						continue;
					}

					w.emitNext((T) o, Sinks.EmitFailureHandler.FAIL_FAST);
					int c = count + 1;

					if (c >= maxSize) {
						producerIndex++;
						count = 0;

						w.emitComplete(Sinks.EmitFailureHandler.FAIL_FAST);

						long r = requested;

						if (r != 0L) {
							w = Sinks.unsafe().many().unicast().onBackpressureBuffer();
							window = w;
							actual.onNext(w.asFlux());
							if (r != Long.MAX_VALUE) {
								REQUESTED.decrementAndGet(this);
							}

							Disposable tm = timer;
							tm.dispose();

							Disposable task = newPeriod();

							if (!TIMER.compareAndSet(this, tm, task)) {
								task.dispose();
							}
						}
						else {
							window = null;
							a.onError(Operators.onOperatorError(s,
									Exceptions.failWithOverflow(), o, actual
											.currentContext()));
							timer.dispose();
							worker.dispose();
							return;
						}
					}
					else {
						count = c;
					}
				}

				missed = WIP.addAndGet(this, -missed);
				if (missed == 0) {
					break;
				}
			}
		}

		boolean enter() {
			return WIP.getAndIncrement(this) == 0;
		}

		static final class ConsumerIndexHolder implements Runnable {

			final long                       index;
			final WindowTimeoutSubscriber<?> parent;

			ConsumerIndexHolder(long index, WindowTimeoutSubscriber<?> parent) {
				this.index = index;
				this.parent = parent;
			}

			@Override
			public void run() {
				WindowTimeoutSubscriber<?> p = parent;

				if (!p.cancelled) {
					p.queue.offer(this);
				}
				else {
					p.terminated = true;
					p.timer.dispose();
					p.worker.dispose();
				}
				if (p.enter()) {
					p.drainLoop();
				}
			}
		}
	}

}