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

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.queue.MpscLinkedQueue;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.observers.DisposableObserver;
import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.subjects.UnicastSubject;

public final class ObservableWindowBoundarySupplier<T, B> extends AbstractObservableWithUpstream<T, Observable<T>> {
    final Callable<? extends ObservableSource<B>> other;
    final int capacityHint;

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

    @Override
    public void subscribeActual(Observer<? super Observable<T>> observer) {
        WindowBoundaryMainObserver<T, B> parent = new WindowBoundaryMainObserver<T, B>(observer, capacityHint, other);

        source.subscribe(parent);
    }

    static final class WindowBoundaryMainObserver<T, B>
    extends AtomicInteger
    implements Observer<T>, Disposable, Runnable {

        private static final long serialVersionUID = 2233020065421370272L;

        final Observer<? super Observable<T>> downstream;

        final int capacityHint;

        final AtomicReference<WindowBoundaryInnerObserver<T, B>> boundaryObserver;

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

        final AtomicInteger windows;

        final MpscLinkedQueue<Object> queue;

        final AtomicThrowable errors;

        final AtomicBoolean stopWindows;

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

        static final Object NEXT_WINDOW = new Object();

        Disposable upstream;

        volatile boolean done;

        UnicastSubject<T> window;

        WindowBoundaryMainObserver(Observer<? super Observable<T>> downstream, int capacityHint, Callable<? extends ObservableSource<B>> other) {
            this.downstream = downstream;
            this.capacityHint = capacityHint;
            this.boundaryObserver = new AtomicReference<WindowBoundaryInnerObserver<T, B>>();
            this.windows = new AtomicInteger(1);
            this.queue = new MpscLinkedQueue<Object>();
            this.errors = new AtomicThrowable();
            this.stopWindows = new AtomicBoolean();
            this.other = other;
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(upstream, d)) {
                upstream = d;
                downstream.onSubscribe(this);
                queue.offer(NEXT_WINDOW);
                drain();
            }
        }

        @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 dispose() {
            if (stopWindows.compareAndSet(false, true)) {
                disposeBoundary();
                if (windows.decrementAndGet() == 0) {
                    upstream.dispose();
                }
            }
        }

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

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

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

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

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

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

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

            int missed = 1;
            Observer<? super Observable<T>> downstream = this.downstream;
            MpscLinkedQueue<Object> queue = this.queue;
            AtomicThrowable errors = this.errors;

            for (;;) {

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

                    UnicastSubject<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()) {
                        w = UnicastSubject.create(capacityHint, this);
                        window = w;
                        windows.getAndIncrement();

                        ObservableSource<B> otherSource;

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

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

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

                            downstream.onNext(w);
                        }
                    }
                }

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

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

        boolean done;

        WindowBoundaryInnerObserver(WindowBoundaryMainObserver<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();
        }
    }
}