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.AtomicReference;

import io.reactivex.*;
import io.reactivex.annotations.Nullable;
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.BasicIntQueueDisposable;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.plugins.RxJavaPlugins;

Maps a sequence of values into CompletableSources and awaits their termination.
Type parameters:
<T> – the value type/**
 * Maps a sequence of values into CompletableSources and awaits their termination.
 * @param <T> the value type
 */
public final class ObservableFlatMapCompletable<T> extends AbstractObservableWithUpstream<T, T> {

    final Function<? super T, ? extends CompletableSource> mapper;

    final boolean delayErrors;

    public ObservableFlatMapCompletable(ObservableSource<T> source,
            Function<? super T, ? extends CompletableSource> mapper, boolean delayErrors) {
        super(source);
        this.mapper = mapper;
        this.delayErrors = delayErrors;
    }

    @Override
    protected void subscribeActual(Observer<? super T> observer) {
        source.subscribe(new FlatMapCompletableMainObserver<T>(observer, mapper, delayErrors));
    }

    static final class FlatMapCompletableMainObserver<T> extends BasicIntQueueDisposable<T>
    implements Observer<T> {
        private static final long serialVersionUID = 8443155186132538303L;

        final Observer<? super T> downstream;

        final AtomicThrowable errors;

        final Function<? super T, ? extends CompletableSource> mapper;

        final boolean delayErrors;

        final CompositeDisposable set;

        Disposable upstream;

        volatile boolean disposed;

        FlatMapCompletableMainObserver(Observer<? super T> observer, Function<? super T, ? extends CompletableSource> mapper, boolean delayErrors) {
            this.downstream = observer;
            this.mapper = mapper;
            this.delayErrors = delayErrors;
            this.errors = new AtomicThrowable();
            this.set = new CompositeDisposable();
            this.lazySet(1);
        }

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

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T value) {
            CompletableSource cs;

            try {
                cs = ObjectHelper.requireNonNull(mapper.apply(value), "The mapper returned a null CompletableSource");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                upstream.dispose();
                onError(ex);
                return;
            }

            getAndIncrement();

            InnerObserver inner = new InnerObserver();

            if (!disposed && set.add(inner)) {
                cs.subscribe(inner);
            }
        }

        @Override
        public void onError(Throwable e) {
            if (errors.addThrowable(e)) {
                if (delayErrors) {
                    if (decrementAndGet() == 0) {
                        Throwable ex = errors.terminate();
                        downstream.onError(ex);
                    }
                } else {
                    dispose();
                    if (getAndSet(0) > 0) {
                        Throwable ex = errors.terminate();
                        downstream.onError(ex);
                    }
                }
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void onComplete() {
            if (decrementAndGet() == 0) {
                Throwable ex = errors.terminate();
                if (ex != null) {
                    downstream.onError(ex);
                } else {
                    downstream.onComplete();
                }
            }
        }

        @Override
        public void dispose() {
            disposed = true;
            upstream.dispose();
            set.dispose();
        }

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

        @Nullable
        @Override
        public T poll() throws Exception {
            return null; // always empty
        }

        @Override
        public boolean isEmpty() {
            return true; // always empty
        }

        @Override
        public void clear() {
            // nothing to clear
        }

        @Override
        public int requestFusion(int mode) {
            return mode & ASYNC;
        }

        void innerComplete(InnerObserver inner) {
            set.delete(inner);
            onComplete();
        }

        void innerError(InnerObserver inner, Throwable e) {
            set.delete(inner);
            onError(e);
        }

        final class InnerObserver extends AtomicReference<Disposable> implements CompletableObserver, Disposable {
            private static final long serialVersionUID = 8606673141535671828L;

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

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

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

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

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