/*
 * 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
 *
 *       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 reactor.core.publisher;

import java.util.Objects;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.function.Consumer;
import java.util.function.Function;

import org.reactivestreams.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;

Uses a resource, generated by a supplier for each individual Subscriber,
while streaming the values from a
Publisher derived from the same resource and makes sure the resource is released
if the sequence terminates or the Subscriber cancels.


Eager resource cleanup happens just before the source termination and exceptions
raised by the cleanup Consumer may override the terminal even. Non-eager
cleanup will drop any exception.
Type parameters:
<T> – the value type streamed
<S> – the resource type
See Also:
Reactive-Streams-Commons/**
 * Uses a resource, generated by a supplier for each individual Subscriber,
 * while streaming the values from a
 * Publisher derived from the same resource and makes sure the resource is released
 * if the sequence terminates or the Subscriber cancels.
 * <p>
 * <p>
 * Eager resource cleanup happens just before the source termination and exceptions
 * raised by the cleanup Consumer may override the terminal even. Non-eager
 * cleanup will drop any exception.
 *
 * @param <T> the value type streamed
 * @param <S> the resource type
 *
 * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
 */
final class FluxUsing<T, S> extends Flux<T> implements Fuseable, SourceProducer<T> {

	final Callable<S> resourceSupplier;

	final Function<? super S, ? extends Publisher<? extends T>> sourceFactory;

	final Consumer<? super S> resourceCleanup;

	final boolean eager;

	FluxUsing(Callable<S> resourceSupplier,
			Function<? super S, ? extends Publisher<? extends T>> sourceFactory,
			Consumer<? super S> resourceCleanup,
			boolean eager) {
		this.resourceSupplier =
				Objects.requireNonNull(resourceSupplier, "resourceSupplier");
		this.sourceFactory = Objects.requireNonNull(sourceFactory, "sourceFactory");
		this.resourceCleanup = Objects.requireNonNull(resourceCleanup, "resourceCleanup");
		this.eager = eager;
	}

	@Override
	@SuppressWarnings("unchecked")
	public void subscribe(CoreSubscriber<? super T> actual) {
		S resource;

		try {
			resource = resourceSupplier.call();
		}
		catch (Throwable e) {
			Operators.error(actual, Operators.onOperatorError(e, actual.currentContext()));
			return;
		}

		Publisher<? extends T> p;

		try {
			p = Objects.requireNonNull(sourceFactory.apply(resource),
					"The sourceFactory returned a null value");
		}
		catch (Throwable e) {
			Throwable _e = Operators.onOperatorError(e, actual.currentContext());
			try {
				resourceCleanup.accept(resource);
			}
			catch (Throwable ex) {
				_e = Exceptions.addSuppressed(ex, _e);
			}

			Operators.error(actual, _e);
			return;
		}

		if (p instanceof Fuseable) {
			from(p).subscribe(new UsingFuseableSubscriber<>(actual,
					resourceCleanup,
					resource,
					eager));
		}
		else if (actual instanceof ConditionalSubscriber) {
			from(p).subscribe(new UsingConditionalSubscriber<>((ConditionalSubscriber<? super T>) actual,
					resourceCleanup,
					resource,
					eager));
		}
		else {
			from(p).subscribe(new UsingSubscriber<>(actual, resourceCleanup,
					resource, eager));
		}
	}

	@Override
	public Object scanUnsafe(Attr key) {
		return null; //no particular key to be represented, still useful in hooks
	}

	static final class UsingSubscriber<T, S>
			implements InnerOperator<T, T>, QueueSubscription<T> {

		final CoreSubscriber<? super T> actual;

		final Consumer<? super S> resourceCleanup;

		final S resource;

		final boolean eager;

		Subscription s;

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

		UsingSubscriber(CoreSubscriber<? super T> actual,
				Consumer<? super S> resourceCleanup,
				S resource,
				boolean eager) {
			this.actual = actual;
			this.resourceCleanup = resourceCleanup;
			this.resource = resource;
			this.eager = eager;
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.TERMINATED || key == Attr.CANCELLED) return wip == 1;
			if (key == Attr.PARENT) return s;

			return InnerOperator.super.scanUnsafe(key);
		}

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

		@Override
		public void request(long n) {
			s.request(n);
		}

		@Override
		public void cancel() {
			if (WIP.compareAndSet(this, 0, 1)) {
				s.cancel();

				cleanup();
			}
		}

		void cleanup() {
			try {
				resourceCleanup.accept(resource);
			}
			catch (Throwable e) {
				Operators.onErrorDropped(e, actual.currentContext());
			}
		}

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

				actual.onSubscribe(this);
			}
		}

		@Override
		public void onNext(T t) {
			actual.onNext(t);
		}

		@Override
		public void onError(Throwable t) {
			if (eager && WIP.compareAndSet(this, 0, 1)) {
				try {
					resourceCleanup.accept(resource);
				}
				catch (Throwable e) {
					Throwable _e = Operators.onOperatorError(e, actual.currentContext());
					t = Exceptions.addSuppressed(_e, t);
				}
			}

			actual.onError(t);

			if (!eager && WIP.compareAndSet(this, 0, 1)) {
				cleanup();
			}
		}

		@Override
		public void onComplete() {
			if (eager && WIP.compareAndSet(this, 0, 1)) {
				try {
					resourceCleanup.accept(resource);
				}
				catch (Throwable e) {
					actual.onError(Operators.onOperatorError(e, actual.currentContext()));
					return;
				}
			}

			actual.onComplete();

			if (!eager && WIP.compareAndSet(this, 0, 1)) {
				cleanup();
			}
		}

		@Override
		public int requestFusion(int requestedMode) {
			return NONE; // always reject, upstream turned out to be non-fuseable after all
		}

		@Override
		public void clear() {
			// ignoring fusion methods
		}

		@Override
		public boolean isEmpty() {
			// ignoring fusion methods
			return true;
		}

		@Override
		@Nullable
		public T poll() {
			return null;
		}

		@Override
		public int size() {
			return 0;
		}
	}

	static final class UsingFuseableSubscriber<T, S>
			implements InnerOperator<T, T>, QueueSubscription<T> {

		final CoreSubscriber<? super T> actual;

		final Consumer<? super S> resourceCleanup;

		final S resource;

		final boolean eager;

		QueueSubscription<T> s;

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

		int mode;

		UsingFuseableSubscriber(CoreSubscriber<? super T> actual,
				Consumer<? super S> resourceCleanup,
				S resource,
				boolean eager) {
			this.actual = actual;
			this.resourceCleanup = resourceCleanup;
			this.resource = resource;
			this.eager = eager;
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.TERMINATED || key == Attr.CANCELLED)
				return wip == 1;
			if (key == Attr.PARENT) return s;

			return InnerOperator.super.scanUnsafe(key);
		}

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

		@Override
		public void request(long n) {
			s.request(n);
		}

		@Override
		public void cancel() {
			if (WIP.compareAndSet(this, 0, 1)) {
				s.cancel();

				cleanup();
			}
		}

		void cleanup() {
			try {
				resourceCleanup.accept(resource);
			}
			catch (Throwable e) {
				Operators.onErrorDropped(e, actual.currentContext());
			}
		}

		@SuppressWarnings("unchecked")
		@Override
		public void onSubscribe(Subscription s) {
			if (Operators.validate(this.s, s)) {
				this.s = (QueueSubscription<T>) s;

				actual.onSubscribe(this);
			}
		}

		@Override
		public void onNext(T t) {
			actual.onNext(t);
		}

		@Override
		public void onError(Throwable t) {
			if (eager && WIP.compareAndSet(this, 0, 1)) {
				try {
					resourceCleanup.accept(resource);
				}
				catch (Throwable e) {
					Throwable _e = Operators.onOperatorError(e, actual.currentContext());
					t = Exceptions.addSuppressed(_e, t);
				}
			}

			actual.onError(t);

			if (!eager && WIP.compareAndSet(this, 0, 1)) {
				cleanup();
			}
		}

		@Override
		public void onComplete() {
			if (eager && WIP.compareAndSet(this, 0, 1)) {
				try {
					resourceCleanup.accept(resource);
				}
				catch (Throwable e) {
					actual.onError(Operators.onOperatorError(e, actual.currentContext()));
					return;
				}
			}

			actual.onComplete();

			if (!eager && WIP.compareAndSet(this, 0, 1)) {
				cleanup();
			}
		}

		@Override
		public void clear() {
			s.clear();
		}

		@Override
		public boolean isEmpty() {
			return s.isEmpty();
		}

		@Override
		@Nullable
		public T poll() {
			T v = s.poll();

			if (v == null && mode == SYNC) {
				if (WIP.compareAndSet(this, 0, 1)) {
					resourceCleanup.accept(resource);
				}
			}
			return v;
		}

		@Override
		public int requestFusion(int requestedMode) {
			int m = s.requestFusion(requestedMode);
			mode = m;
			return m;
		}

		@Override
		public int size() {
			return s.size();
		}
	}

	static final class UsingConditionalSubscriber<T, S>
			implements ConditionalSubscriber<T>, InnerOperator<T, T>,
			           QueueSubscription<T> {

		final ConditionalSubscriber<? super T> actual;

		final Consumer<? super S> resourceCleanup;

		final S resource;

		final boolean eager;

		Subscription s;

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

		UsingConditionalSubscriber(ConditionalSubscriber<? super T> actual,
				Consumer<? super S> resourceCleanup,
				S resource,
				boolean eager) {
			this.actual = actual;
			this.resourceCleanup = resourceCleanup;
			this.resource = resource;
			this.eager = eager;
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.TERMINATED || key == Attr.CANCELLED)
				return wip == 1;
			if (key == Attr.PARENT) return s;

			return InnerOperator.super.scanUnsafe(key);
		}

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

		@Override
		public void request(long n) {
			s.request(n);
		}

		@Override
		public void cancel() {
			if (WIP.compareAndSet(this, 0, 1)) {
				s.cancel();

				cleanup();
			}
		}

		void cleanup() {
			try {
				resourceCleanup.accept(resource);
			}
			catch (Throwable e) {
				Operators.onErrorDropped(e, actual.currentContext());
			}
		}

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

				actual.onSubscribe(this);
			}
		}

		@Override
		public void onNext(T t) {
			actual.onNext(t);
		}

		@Override
		public boolean tryOnNext(T t) {
			return actual.tryOnNext(t);
		}

		@Override
		public void onError(Throwable t) {
			if (eager && WIP.compareAndSet(this, 0, 1)) {
				try {
					resourceCleanup.accept(resource);
				}
				catch (Throwable e) {
					Throwable _e = Operators.onOperatorError(e, actual.currentContext());
					t = Exceptions.addSuppressed(_e, t);
				}
			}

			actual.onError(t);

			if (!eager && WIP.compareAndSet(this, 0, 1)) {
				cleanup();
			}
		}

		@Override
		public void onComplete() {
			if (eager && WIP.compareAndSet(this, 0, 1)) {
				try {
					resourceCleanup.accept(resource);
				}
				catch (Throwable e) {
					actual.onError(Operators.onOperatorError(e, actual.currentContext()));
					return;
				}
			}

			actual.onComplete();

			if (!eager && WIP.compareAndSet(this, 0, 1)) {
				cleanup();
			}
		}

		@Override
		public int requestFusion(int requestedMode) {
			return NONE; // always reject, upstream turned out to be non-fuseable after all
		}

		@Override
		public void clear() {
			// ignoring fusion methods
		}

		@Override
		public boolean isEmpty() {
			// ignoring fusion methods
			return true;
		}

		@Override
		@Nullable
		public T poll() {
			return null;
		}

		@Override
		public int size() {
			return 0;
		}
	}
}