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.observable;

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

import io.reactivex.Observable;
import io.reactivex.ObservableSource;
import io.reactivex.Observer;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.observers.QueueDrainObserver;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.util.NotificationLite;
import io.reactivex.observers.*;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.subjects.UnicastSubject;

public final class ObservableWindowBoundarySelector<T, B, V> extends AbstractObservableWithUpstream<T, Observable<T>> {
    final ObservableSource<B> open;
    final Function<? super B, ? extends ObservableSource<V>> close;
    final int bufferSize;

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

    @Override
    public void subscribeActual(Observer<? super Observable<T>> t) {
        source.subscribe(new WindowBoundaryMainObserver<T, B, V>(
                new SerializedObserver<Observable<T>>(t),
                open, close, bufferSize));
    }

    static final class WindowBoundaryMainObserver<T, B, V>
    extends QueueDrainObserver<T, Object, Observable<T>>
    implements Disposable {
        final ObservableSource<B> open;
        final Function<? super B, ? extends ObservableSource<V>> close;
        final int bufferSize;
        final CompositeDisposable resources;

        Disposable upstream;

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

        final List<UnicastSubject<T>> ws;

        final AtomicLong windows = new AtomicLong();

        final AtomicBoolean stopWindows = new AtomicBoolean();

        WindowBoundaryMainObserver(Observer<? super Observable<T>> actual,
                                            ObservableSource<B> open, Function<? super B, ? extends ObservableSource<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<UnicastSubject<T>>();
            windows.lazySet(1);
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;

                downstream.onSubscribe(this);

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

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

                if (boundary.compareAndSet(null, os)) {
                    open.subscribe(os);
                }
            }
        }

        @Override
        public void onNext(T t) {
            if (fastEnter()) {
                for (UnicastSubject<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.dispose();
            resources.dispose();
            onError(t);
        }

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

        @Override
        public boolean isDisposed() {
            return stopWindows.get();
        }

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

        void drainLoop() {
            final MpscLinkedQueue<Object> q = (MpscLinkedQueue<Object>)queue;
            final Observer<? super Observable<T>> a = downstream;
            final List<UnicastSubject<T>> ws = this.ws;
            int missed = 1;

            for (;;) {

                for (;;) {
                    boolean d = done;

                    Object o = q.poll();

                    boolean empty = o == null;

                    if (d && empty) {
                        disposeBoundary();
                        Throwable e = error;
                        if (e != null) {
                            for (UnicastSubject<T> w : ws) {
                                w.onError(e);
                            }
                        } else {
                            for (UnicastSubject<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;

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

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

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

                        w = UnicastSubject.create(bufferSize);

                        ws.add(w);
                        a.onNext(w);

                        ObservableSource<V> p;

                        try {
                            p = ObjectHelper.requireNonNull(close.apply(wo.open), "The ObservableSource supplied is null");
                        } catch (Throwable e) {
                            Exceptions.throwIfFatal(e);
                            stopWindows.set(true);
                            a.onError(e);
                            continue;
                        }

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

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

                            p.subscribe(cl);
                        }

                        continue;
                    }

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

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

        @Override
        public void accept(Observer<? super Observable<T>> a, Object v) {
        }

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

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

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

    static final class OperatorWindowBoundaryOpenObserver<T, B> extends DisposableObserver<B> {
        final WindowBoundaryMainObserver<T, B, ?> parent;

        OperatorWindowBoundaryOpenObserver(WindowBoundaryMainObserver<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 OperatorWindowBoundaryCloseObserver<T, V> extends DisposableObserver<V> {
        final WindowBoundaryMainObserver<T, ?, V> parent;
        final UnicastSubject<T> w;

        boolean done;

        OperatorWindowBoundaryCloseObserver(WindowBoundaryMainObserver<T, ?, V> parent, UnicastSubject<T> w) {
            this.parent = parent;
            this.w = w;
        }

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