https://github.com/ReactiveX/RxJava: Reactive Extensions for Java
  • David Karnok 
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.functions.Function;
import io.reactivex.internal.disposables.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.*;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.util.*;
import io.reactivex.observers.SerializedObserver;
import io.reactivex.plugins.RxJavaPlugins;

public final class ObservableConcatMap<T, U> extends AbstractObservableWithUpstream<T, U> {
    final Function<? super T, ? extends ObservableSource<? extends U>> mapper;
    final int bufferSize;

    final ErrorMode delayErrors;

    public ObservableConcatMap(ObservableSource<T> source, Function<? super T, ? extends ObservableSource<? extends U>> mapper,
            int bufferSize, ErrorMode delayErrors) {
        super(source);
        this.mapper = mapper;
        this.delayErrors = delayErrors;
        this.bufferSize = Math.max(8, bufferSize);
    }

    @Override
    public void subscribeActual(Observer<? super U> observer) {

        if (ObservableScalarXMap.tryScalarXMapSubscribe(source, observer, mapper)) {
            return;
        }

        if (delayErrors == ErrorMode.IMMEDIATE) {
            SerializedObserver<U> serial = new SerializedObserver<U>(observer);
            source.subscribe(new SourceObserver<T, U>(serial, mapper, bufferSize));
        } else {
            source.subscribe(new ConcatMapDelayErrorObserver<T, U>(observer, mapper, bufferSize, delayErrors == ErrorMode.END));
        }
    }

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

        private static final long serialVersionUID = 8828587559905699186L;
        final Observer<? super U> downstream;
        final Function<? super T, ? extends ObservableSource<? extends U>> mapper;
        final InnerObserver<U> inner;
        final int bufferSize;

        SimpleQueue<T> queue;

        Disposable upstream;

        volatile boolean active;

        volatile boolean disposed;

        volatile boolean done;

        int fusionMode;

        SourceObserver(Observer<? super U> actual,
                                Function<? super T, ? extends ObservableSource<? extends U>> mapper, int bufferSize) {
            this.downstream = actual;
            this.mapper = mapper;
            this.bufferSize = bufferSize;
            this.inner = new InnerObserver<U>(actual, this);
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;
                if (d instanceof QueueDisposable) {
                    @SuppressWarnings("unchecked")
                    QueueDisposable<T> qd = (QueueDisposable<T>) d;

                    int m = qd.requestFusion(QueueDisposable.ANY);
                    if (m == QueueDisposable.SYNC) {
                        fusionMode = m;
                        queue = qd;
                        done = true;

                        downstream.onSubscribe(this);

                        drain();
                        return;
                    }

                    if (m == QueueDisposable.ASYNC) {
                        fusionMode = m;
                        queue = qd;

                        downstream.onSubscribe(this);

                        return;
                    }
                }

                queue = new SpscLinkedArrayQueue<T>(bufferSize);

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }
            if (fusionMode == QueueDisposable.NONE) {
                queue.offer(t);
            }
            drain();
        }

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

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

        void innerComplete() {
            active = false;
            drain();
        }

        @Override
        public boolean isDisposed() {
            return disposed;
        }

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

            if (getAndIncrement() == 0) {
                queue.clear();
            }
        }

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            for (;;) {
                if (disposed) {
                    queue.clear();
                    return;
                }
                if (!active) {

                    boolean d = done;

                    T t;

                    try {
                        t = queue.poll();
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        dispose();
                        queue.clear();
                        downstream.onError(ex);
                        return;
                    }

                    boolean empty = t == null;

                    if (d && empty) {
                        disposed = true;
                        downstream.onComplete();
                        return;
                    }

                    if (!empty) {
                        ObservableSource<? extends U> o;

                        try {
                            o = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null ObservableSource");
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            dispose();
                            queue.clear();
                            downstream.onError(ex);
                            return;
                        }

                        active = true;
                        o.subscribe(inner);
                    }
                }

                if (decrementAndGet() == 0) {
                    break;
                }
            }
        }

        static final class InnerObserver<U> extends AtomicReference<Disposable> implements Observer<U> {

            private static final long serialVersionUID = -7449079488798789337L;

            final Observer<? super U> downstream;
            final SourceObserver<?, ?> parent;

            InnerObserver(Observer<? super U> actual, SourceObserver<?, ?> parent) {
                this.downstream = actual;
                this.parent = parent;
            }

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

            @Override
            public void onNext(U t) {
                downstream.onNext(t);
            }

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

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

            void dispose() {
                DisposableHelper.dispose(this);
            }
        }
    }

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

        private static final long serialVersionUID = -6951100001833242599L;

        final Observer<? super R> downstream;

        final Function<? super T, ? extends ObservableSource<? extends R>> mapper;

        final int bufferSize;

        final AtomicThrowable error;

        final DelayErrorInnerObserver<R> observer;

        final boolean tillTheEnd;

        SimpleQueue<T> queue;

        Disposable upstream;

        volatile boolean active;

        volatile boolean done;

        volatile boolean cancelled;

        int sourceMode;

        ConcatMapDelayErrorObserver(Observer<? super R> actual,
                Function<? super T, ? extends ObservableSource<? extends R>> mapper, int bufferSize,
                        boolean tillTheEnd) {
            this.downstream = actual;
            this.mapper = mapper;
            this.bufferSize = bufferSize;
            this.tillTheEnd = tillTheEnd;
            this.error = new AtomicThrowable();
            this.observer = new DelayErrorInnerObserver<R>(actual, this);
        }

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

                if (d instanceof QueueDisposable) {
                    @SuppressWarnings("unchecked")
                    QueueDisposable<T> qd = (QueueDisposable<T>) d;

                    int m = qd.requestFusion(QueueDisposable.ANY);
                    if (m == QueueDisposable.SYNC) {
                        sourceMode = m;
                        queue = qd;
                        done = true;

                        downstream.onSubscribe(this);

                        drain();
                        return;
                    }
                    if (m == QueueDisposable.ASYNC) {
                        sourceMode = m;
                        queue = qd;

                        downstream.onSubscribe(this);

                        return;
                    }
                }

                queue = new SpscLinkedArrayQueue<T>(bufferSize);

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T value) {
            if (sourceMode == QueueDisposable.NONE) {
                queue.offer(value);
            }
            drain();
        }

        @Override
        public void onError(Throwable e) {
            if (error.addThrowable(e)) {
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

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

        @Override
        public boolean isDisposed() {
            return cancelled;
        }

        @Override
        public void dispose() {
            cancelled = true;
            upstream.dispose();
            observer.dispose();
        }

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

            Observer<? super R> actual = this.downstream;
            SimpleQueue<T> queue = this.queue;
            AtomicThrowable error = this.error;

            for (;;) {

                if (!active) {

                    if (cancelled) {
                        queue.clear();
                        return;
                    }

                    if (!tillTheEnd) {
                        Throwable ex = error.get();
                        if (ex != null) {
                            queue.clear();
                            cancelled = true;
                            actual.onError(error.terminate());
                            return;
                        }
                    }

                    boolean d = done;

                    T v;

                    try {
                        v = queue.poll();
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        cancelled = true;
                        this.upstream.dispose();
                        error.addThrowable(ex);
                        actual.onError(error.terminate());
                        return;
                    }

                    boolean empty = v == null;

                    if (d && empty) {
                        cancelled = true;
                        Throwable ex = error.terminate();
                        if (ex != null) {
                            actual.onError(ex);
                        } else {
                            actual.onComplete();
                        }
                        return;
                    }

                    if (!empty) {

                        ObservableSource<? extends R> o;

                        try {
                            o = ObjectHelper.requireNonNull(mapper.apply(v), "The mapper returned a null ObservableSource");
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            cancelled = true;
                            this.upstream.dispose();
                            queue.clear();
                            error.addThrowable(ex);
                            actual.onError(error.terminate());
                            return;
                        }

                        if (o instanceof Callable) {
                            R w;

                            try {
                                w = ((Callable<R>)o).call();
                            } catch (Throwable ex) {
                                Exceptions.throwIfFatal(ex);
                                error.addThrowable(ex);
                                continue;
                            }

                            if (w != null && !cancelled) {
                                actual.onNext(w);
                            }
                            continue;
                        } else {
                            active = true;
                            o.subscribe(observer);
                        }
                    }
                }

                if (decrementAndGet() == 0) {
                    break;
                }
            }
        }

        static final class DelayErrorInnerObserver<R> extends AtomicReference<Disposable> implements Observer<R> {

            private static final long serialVersionUID = 2620149119579502636L;

            final Observer<? super R> downstream;

            final ConcatMapDelayErrorObserver<?, R> parent;

            DelayErrorInnerObserver(Observer<? super R> actual, ConcatMapDelayErrorObserver<?, R> parent) {
                this.downstream = actual;
                this.parent = parent;
            }

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

            @Override
            public void onNext(R value) {
                downstream.onNext(value);
            }

            @Override
            public void onError(Throwable e) {
                ConcatMapDelayErrorObserver<?, R> p = parent;
                if (p.error.addThrowable(e)) {
                    if (!p.tillTheEnd) {
                        p.upstream.dispose();
                    }
                    p.active = false;
                    p.drain();
                } else {
                    RxJavaPlugins.onError(e);
                }
            }

            @Override
            public void onComplete() {
                ConcatMapDelayErrorObserver<?, R> p = parent;
                p.active = false;
                p.drain();
            }

            void dispose() {
                DisposableHelper.dispose(this);
            }
        }
    }
}