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.atomic.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.util.*;
import io.reactivex.subjects.*;

Repeatedly subscribe to a source if a handler ObservableSource signals an item.
Type parameters:
<T> – the value type/**
 * Repeatedly subscribe to a source if a handler ObservableSource signals an item.
 *
 * @param <T> the value type
 */
public final class ObservableRepeatWhen<T> extends AbstractObservableWithUpstream<T, T> {

    final Function<? super Observable<Object>, ? extends ObservableSource<?>> handler;

    public ObservableRepeatWhen(ObservableSource<T> source, Function<? super Observable<Object>, ? extends ObservableSource<?>> handler) {
        super(source);
        this.handler = handler;
    }

    @Override
    protected void subscribeActual(Observer<? super T> observer) {
        Subject<Object> signaller = PublishSubject.create().toSerialized();

        ObservableSource<?> other;

        try {
            other = ObjectHelper.requireNonNull(handler.apply(signaller), "The handler returned a null ObservableSource");
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            EmptyDisposable.error(ex, observer);
            return;
        }

        RepeatWhenObserver<T> parent = new RepeatWhenObserver<T>(observer, signaller, source);
        observer.onSubscribe(parent);

        other.subscribe(parent.inner);

        parent.subscribeNext();
    }

    static final class RepeatWhenObserver<T> extends AtomicInteger implements Observer<T>, Disposable {

        private static final long serialVersionUID = 802743776666017014L;

        final Observer<? super T> downstream;

        final AtomicInteger wip;

        final AtomicThrowable error;

        final Subject<Object> signaller;

        final InnerRepeatObserver inner;

        final AtomicReference<Disposable> upstream;

        final ObservableSource<T> source;

        volatile boolean active;

        RepeatWhenObserver(Observer<? super T> actual, Subject<Object> signaller, ObservableSource<T> source) {
            this.downstream = actual;
            this.signaller = signaller;
            this.source = source;
            this.wip = new AtomicInteger();
            this.error = new AtomicThrowable();
            this.inner = new InnerRepeatObserver();
            this.upstream = new AtomicReference<Disposable>();
        }

        @Override
        public void onSubscribe(Disposable d) {
            DisposableHelper.setOnce(this.upstream, d);
        }

        @Override
        public void onNext(T t) {
            HalfSerializer.onNext(downstream, t, this, error);
        }

        @Override
        public void onError(Throwable e) {
            DisposableHelper.dispose(inner);
            HalfSerializer.onError(downstream, e, this, error);
        }

        @Override
        public void onComplete() {
            DisposableHelper.replace(upstream, null);
            active = false;
            signaller.onNext(0);
        }

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

        @Override
        public void dispose() {
            DisposableHelper.dispose(upstream);
            DisposableHelper.dispose(inner);
        }

        void innerNext() {
            subscribeNext();
        }

        void innerError(Throwable ex) {
            DisposableHelper.dispose(upstream);
            HalfSerializer.onError(downstream, ex, this, error);
        }

        void innerComplete() {
            DisposableHelper.dispose(upstream);
            HalfSerializer.onComplete(downstream, this, error);
        }

        void subscribeNext() {
            if (wip.getAndIncrement() == 0) {

                do {
                    if (isDisposed()) {
                        return;
                    }

                    if (!active) {
                        active = true;
                        source.subscribe(this);
                    }
                } while (wip.decrementAndGet() != 0);
            }
        }

        final class InnerRepeatObserver extends AtomicReference<Disposable> implements Observer<Object> {

            private static final long serialVersionUID = 3254781284376480842L;

            @Override
            public void onSubscribe(Disposable d) {
                DisposableHelper.setOnce(this, d);
            }

            @Override
            public void onNext(Object t) {
                innerNext();
            }

            @Override
            public void onError(Throwable e) {
                innerError(e);
            }

            @Override
            public void onComplete() {
                innerComplete();
            }
        }
    }
}