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

import org.reactivestreams.*;

import io.reactivex.Flowable;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.MissingBackpressureException;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.SimplePlainQueue;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.subscribers.QueueDrainSubscriber;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.NotificationLite;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.processors.UnicastProcessor;
import io.reactivex.subscribers.*;

public final class FlowableWindowBoundarySelector<T, B, V> extends AbstractFlowableWithUpstream<T, Flowable<T>> {
    final Publisher<B> open;
    final Function<? super B, ? extends Publisher<V>> close;
    final int bufferSize;

    public FlowableWindowBoundarySelector(
            Flowable<T> source,
            Publisher<B> open, Function<? super B, ? extends Publisher<V>> close,
            int bufferSize) {
        super(source);
        this.open = open;
        this.close = close;
        this.bufferSize = bufferSize;
    }

    @Override
    protected void subscribeActual(Subscriber<? super Flowable<T>> s) {
        source.subscribe(new WindowBoundaryMainSubscriber<T, B, V>(
                new SerializedSubscriber<Flowable<T>>(s),
                open, close, bufferSize));
    }

    static final class WindowBoundaryMainSubscriber<T, B, V>
    extends QueueDrainSubscriber<T, Object, Flowable<T>>
    implements Subscription {
        final Publisher<B> open;
        final Function<? super B, ? extends Publisher<V>> close;
        final int bufferSize;
        final CompositeDisposable resources;

        Subscription upstream;

        final AtomicReference<Disposable> boundary = new AtomicReference<Disposable>();

        final List<UnicastProcessor<T>> ws;

        final AtomicLong windows = new AtomicLong();

        final AtomicBoolean stopWindows = new AtomicBoolean();

        WindowBoundaryMainSubscriber(Subscriber<? super Flowable<T>> actual,
                Publisher<B> open, Function<? super B, ? extends Publisher<V>> close, int bufferSize) {
            super(actual, new MpscLinkedQueue<Object>());
            this.open = open;
            this.close = close;
            this.bufferSize = bufferSize;
            this.resources = new CompositeDisposable();
            this.ws = new ArrayList<UnicastProcessor<T>>();
            windows.lazySet(1);
        }

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

                downstream.onSubscribe(this);

                if (stopWindows.get()) {
                    return;
                }

                OperatorWindowBoundaryOpenSubscriber<T, B> os = new OperatorWindowBoundaryOpenSubscriber<T, B>(this);

                if (boundary.compareAndSet(null, os)) {
                    s.request(Long.MAX_VALUE);
                    open.subscribe(os);
                }
            }
        }

        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }
            if (fastEnter()) {
                for (UnicastProcessor<T> w : ws) {
                    w.onNext(t);
                }
                if (leave(-1) == 0) {
                    return;
                }
            } else {
                queue.offer(NotificationLite.next(t));
                if (!enter()) {
                    return;
                }
            }
            drainLoop();
        }

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

            if (enter()) {
                drainLoop();
            }

            if (windows.decrementAndGet() == 0) {
                resources.dispose();
            }

            downstream.onError(t);
        }

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

            if (enter()) {
                drainLoop();
            }

            if (windows.decrementAndGet() == 0) {
                resources.dispose();
            }

            downstream.onComplete();
        }

        void error(Throwable t) {
            upstream.cancel();
            resources.dispose();
            DisposableHelper.dispose(boundary);

            downstream.onError(t);
        }

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

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

        void dispose() {
            resources.dispose();
            DisposableHelper.dispose(boundary);
        }

        void drainLoop() {
            final SimplePlainQueue<Object> q = queue;
            final Subscriber<? super Flowable<T>> a = downstream;
            final List<UnicastProcessor<T>> ws = this.ws;
            int missed = 1;

            for (;;) {

                for (;;) {
                    boolean d = done;
                    Object o = q.poll();

                    boolean empty = o == null;

                    if (d && empty) {
                        dispose();
                        Throwable e = error;
                        if (e != null) {
                            for (UnicastProcessor<T> w : ws) {
                                w.onError(e);
                            }
                        } else {
                            for (UnicastProcessor<T> w : ws) {
                                w.onComplete();
                            }
                        }
                        ws.clear();
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    if (o instanceof WindowOperation) {
                        @SuppressWarnings("unchecked")
                        WindowOperation<T, B> wo = (WindowOperation<T, B>) o;

                        UnicastProcessor<T> w = wo.w;
                        if (w != null) {
                            if (ws.remove(wo.w)) {
                                wo.w.onComplete();

                                if (windows.decrementAndGet() == 0) {
                                    dispose();
                                    return;
                                }
                            }
                            continue;
                        }

                        if (stopWindows.get()) {
                            continue;
                        }

                        w = UnicastProcessor.<T>create(bufferSize);

                        long r = requested();
                        if (r != 0L) {
                            ws.add(w);
                            a.onNext(w);
                            if (r != Long.MAX_VALUE) {
                                produced(1);
                            }
                        } else {
                            cancel();
                            a.onError(new MissingBackpressureException("Could not deliver new window due to lack of requests"));
                            continue;
                        }

                        Publisher<V> p;

                        try {
                            p = ObjectHelper.requireNonNull(close.apply(wo.open), "The publisher supplied is null");
                        } catch (Throwable e) {
                            cancel();
                            a.onError(e);
                            continue;
                        }

                        OperatorWindowBoundaryCloseSubscriber<T, V> cl = new OperatorWindowBoundaryCloseSubscriber<T, V>(this, w);

                        if (resources.add(cl)) {
                            windows.getAndIncrement();

                            p.subscribe(cl);
                        }

                        continue;
                    }

                    for (UnicastProcessor<T> w : ws) {
                        w.onNext(NotificationLite.<T>getValue(o));
                    }
                }

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

        @Override
        public boolean accept(Subscriber<? super Flowable<T>> a, Object v) {
            // not used by this operator
            return false;
        }

        void open(B b) {
            queue.offer(new WindowOperation<T, B>(null, b));
            if (enter()) {
                drainLoop();
            }
        }

        void close(OperatorWindowBoundaryCloseSubscriber<T, V> w) {
            resources.delete(w);
            queue.offer(new WindowOperation<T, B>(w.w, null));
            if (enter()) {
                drainLoop();
            }
        }
    }

    static final class WindowOperation<T, B> {
        final UnicastProcessor<T> w;
        final B open;
        WindowOperation(UnicastProcessor<T> w, B open) {
            this.w = w;
            this.open = open;
        }
    }

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

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

        @Override
        public void onNext(B t) {
            parent.open(t);
        }

        @Override
        public void onError(Throwable t) {
            parent.error(t);
        }

        @Override
        public void onComplete() {
            parent.onComplete();
        }
    }

    static final class OperatorWindowBoundaryCloseSubscriber<T, V> extends DisposableSubscriber<V> {
        final WindowBoundaryMainSubscriber<T, ?, V> parent;
        final UnicastProcessor<T> w;

        boolean done;

        OperatorWindowBoundaryCloseSubscriber(WindowBoundaryMainSubscriber<T, ?, V> parent, UnicastProcessor<T> w) {
            this.parent = parent;
            this.w = w;
        }

        @Override
        public void onNext(V t) {
            cancel();
            onComplete();
        }

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

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