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

import org.reactivestreams.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.processors.UnicastProcessor;
import io.reactivex.subscribers.DisposableSubscriber;

public final class FlowableWindowBoundarySupplier<T, B> extends AbstractFlowableWithUpstream<T, Flowable<T>> {
    final Callable<? extends Publisher<B>> other;
    final int capacityHint;

    public FlowableWindowBoundarySupplier(Flowable<T> source,
            Callable<? extends Publisher<B>> other, int capacityHint) {
        super(source);
        this.other = other;
        this.capacityHint = capacityHint;
    }

    @Override
    protected void subscribeActual(Subscriber<? super Flowable<T>> subscriber) {
        WindowBoundaryMainSubscriber<T, B> parent = new WindowBoundaryMainSubscriber<T, B>(subscriber, capacityHint, other);

        source.subscribe(parent);
    }

    static final class WindowBoundaryMainSubscriber<T, B>
    extends AtomicInteger
    implements FlowableSubscriber<T>, Subscription, Runnable {

        private static final long serialVersionUID = 2233020065421370272L;

        final Subscriber<? super Flowable<T>> downstream;

        final int capacityHint;

        final AtomicReference<WindowBoundaryInnerSubscriber<T, B>> boundarySubscriber;

        static final WindowBoundaryInnerSubscriber<Object, Object> BOUNDARY_DISPOSED = new WindowBoundaryInnerSubscriber<Object, Object>(null);

        final AtomicInteger windows;

        final MpscLinkedQueue<Object> queue;

        final AtomicThrowable errors;

        final AtomicBoolean stopWindows;

        final Callable<? extends Publisher<B>> other;

        static final Object NEXT_WINDOW = new Object();

        final AtomicLong requested;

        Subscription upstream;

        volatile boolean done;

        UnicastProcessor<T> window;

        long emitted;

        WindowBoundaryMainSubscriber(Subscriber<? super Flowable<T>> downstream, int capacityHint, Callable<? extends Publisher<B>> other) {
            this.downstream = downstream;
            this.capacityHint = capacityHint;
            this.boundarySubscriber = new AtomicReference<WindowBoundaryInnerSubscriber<T, B>>();
            this.windows = new AtomicInteger(1);
            this.queue = new MpscLinkedQueue<Object>();
            this.errors = new AtomicThrowable();
            this.stopWindows = new AtomicBoolean();
            this.other = other;
            this.requested = new AtomicLong();
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(upstream, s)) {
                upstream = s;
                downstream.onSubscribe(this);
                queue.offer(NEXT_WINDOW);
                drain();
                s.request(Long.MAX_VALUE);
            }
        }

        @Override
        public void onNext(T t) {
            queue.offer(t);
            drain();
        }

        @Override
        public void onError(Throwable e) {
            disposeBoundary();
            if (errors.addThrowable(e)) {
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void onComplete() {
            disposeBoundary();
            done = true;
            drain();
        }

        @Override
        public void cancel() {
            if (stopWindows.compareAndSet(false, true)) {
                disposeBoundary();
                if (windows.decrementAndGet() == 0) {
                    upstream.cancel();
                }
            }
        }

        @Override
        public void request(long n) {
            BackpressureHelper.add(requested, n);
        }

        @SuppressWarnings({ "rawtypes", "unchecked" })
        void disposeBoundary() {
            Disposable d = boundarySubscriber.getAndSet((WindowBoundaryInnerSubscriber)BOUNDARY_DISPOSED);
            if (d != null && d != BOUNDARY_DISPOSED) {
                d.dispose();
            }
        }

        @Override
        public void run() {
            if (windows.decrementAndGet() == 0) {
                upstream.cancel();
            }
        }

        void innerNext(WindowBoundaryInnerSubscriber<T, B> sender) {
            boundarySubscriber.compareAndSet(sender, null);
            queue.offer(NEXT_WINDOW);
            drain();
        }

        void innerError(Throwable e) {
            upstream.cancel();
            if (errors.addThrowable(e)) {
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        void innerComplete() {
            upstream.cancel();
            done = true;
            drain();
        }

        @SuppressWarnings("unchecked")
        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            int missed = 1;
            Subscriber<? super Flowable<T>> downstream = this.downstream;
            MpscLinkedQueue<Object> queue = this.queue;
            AtomicThrowable errors = this.errors;
            long emitted = this.emitted;

            for (;;) {

                for (;;) {
                    if (windows.get() == 0) {
                        queue.clear();
                        window = null;
                        return;
                    }

                    UnicastProcessor<T> w = window;

                    boolean d = done;

                    if (d && errors.get() != null) {
                        queue.clear();
                        Throwable ex = errors.terminate();
                        if (w != null) {
                            window = null;
                            w.onError(ex);
                        }
                        downstream.onError(ex);
                        return;
                    }

                    Object v = queue.poll();

                    boolean empty = v == null;

                    if (d && empty) {
                        Throwable ex = errors.terminate();
                        if (ex == null) {
                            if (w != null) {
                                window = null;
                                w.onComplete();
                            }
                            downstream.onComplete();
                        } else {
                            if (w != null) {
                                window = null;
                                w.onError(ex);
                            }
                            downstream.onError(ex);
                        }
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    if (v != NEXT_WINDOW) {
                        w.onNext((T)v);
                        continue;
                    }

                    if (w != null) {
                        window = null;
                        w.onComplete();
                    }

                    if (!stopWindows.get()) {
                        if (emitted != requested.get()) {
                            w = UnicastProcessor.create(capacityHint, this);
                            window = w;
                            windows.getAndIncrement();

                            Publisher<B> otherSource;

                            try {
                                otherSource = ObjectHelper.requireNonNull(other.call(), "The other Callable returned a null Publisher");
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);
                                errors.addThrowable(ex);
                                done = true;
                                continue;
                            }

                            WindowBoundaryInnerSubscriber<T, B> bo = new WindowBoundaryInnerSubscriber<T, B>(this);

                            if (boundarySubscriber.compareAndSet(null, bo)) {
                                otherSource.subscribe(bo);

                                emitted++;
                                downstream.onNext(w);
                            }
                        } else {
                            upstream.cancel();
                            disposeBoundary();
                            errors.addThrowable(new MissingBackpressureException("Could not deliver a window due to lack of requests"));
                            done = true;
                        }
                    }
                }

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

    static final class WindowBoundaryInnerSubscriber<T, B> extends DisposableSubscriber<B> {
        final WindowBoundaryMainSubscriber<T, B> parent;

        boolean done;

        WindowBoundaryInnerSubscriber(WindowBoundaryMainSubscriber<T, B> parent) {
            this.parent = parent;
        }

        @Override
        public void onNext(B t) {
            if (done) {
                return;
            }
            done = true;
            dispose();
            parent.innerNext(this);
        }

        @Override
        public void onError(Throwable t) {
            if (done) {
                RxJavaPlugins.onError(t);
                return;
            }
            done = true;
            parent.innerError(t);
        }

        @Override
        public void onComplete() {
            if (done) {
                return;
            }
            done = true;
            parent.innerComplete();
        }
    }
}