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.ArrayDeque;
import java.util.concurrent.atomic.AtomicInteger;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
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.fuseable.*;
import io.reactivex.internal.observers.*;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.util.*;
import io.reactivex.plugins.RxJavaPlugins;

public final class ObservableConcatMapEager<T, R> extends AbstractObservableWithUpstream<T, R> {

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

    final ErrorMode errorMode;

    final int maxConcurrency;

    final int prefetch;

    public ObservableConcatMapEager(ObservableSource<T> source,
            Function<? super T, ? extends ObservableSource<? extends R>> mapper,
            ErrorMode errorMode,
            int maxConcurrency, int prefetch) {
        super(source);
        this.mapper = mapper;
        this.errorMode = errorMode;
        this.maxConcurrency = maxConcurrency;
        this.prefetch = prefetch;
    }

    @Override
    protected void subscribeActual(Observer<? super R> observer) {
        source.subscribe(new ConcatMapEagerMainObserver<T, R>(observer, mapper, maxConcurrency, prefetch, errorMode));
    }

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

        private static final long serialVersionUID = 8080567949447303262L;

        final Observer<? super R> downstream;

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

        final int maxConcurrency;

        final int prefetch;

        final ErrorMode errorMode;

        final AtomicThrowable error;

        final ArrayDeque<InnerQueuedObserver<R>> observers;

        SimpleQueue<T> queue;

        Disposable upstream;

        volatile boolean done;

        int sourceMode;

        volatile boolean cancelled;

        InnerQueuedObserver<R> current;

        int activeCount;

        ConcatMapEagerMainObserver(Observer<? super R> actual,
                Function<? super T, ? extends ObservableSource<? extends R>> mapper,
                int maxConcurrency, int prefetch, ErrorMode errorMode) {
            this.downstream = actual;
            this.mapper = mapper;
            this.maxConcurrency = maxConcurrency;
            this.prefetch = prefetch;
            this.errorMode = errorMode;
            this.error = new AtomicThrowable();
            this.observers = new ArrayDeque<InnerQueuedObserver<R>>();
        }

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

                if (d instanceof QueueDisposable) {
                    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>(prefetch);

                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 void dispose() {
            if (cancelled) {
                return;
            }
            cancelled = true;
            upstream.dispose();

            drainAndDispose();
        }

        void drainAndDispose() {
            if (getAndIncrement() == 0) {
                do {
                    queue.clear();
                    disposeAll();
                } while (decrementAndGet() != 0);
            }
        }

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

        void disposeAll() {
            InnerQueuedObserver<R> inner = current;

            if (inner != null) {
                inner.dispose();
            }

            for (;;) {

                inner = observers.poll();

                if (inner == null) {
                    return;
                }

                inner.dispose();
            }
        }

        @Override
        public void innerNext(InnerQueuedObserver<R> inner, R value) {
            inner.queue().offer(value);
            drain();
        }

        @Override
        public void innerError(InnerQueuedObserver<R> inner, Throwable e) {
            if (error.addThrowable(e)) {
                if (errorMode == ErrorMode.IMMEDIATE) {
                    upstream.dispose();
                }
                inner.setDone();
                drain();
            } else {
                RxJavaPlugins.onError(e);
            }
        }

        @Override
        public void innerComplete(InnerQueuedObserver<R> inner) {
            inner.setDone();
            drain();
        }

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

            int missed = 1;

            SimpleQueue<T> q = queue;
            ArrayDeque<InnerQueuedObserver<R>> observers = this.observers;
            Observer<? super R> a = this.downstream;
            ErrorMode errorMode = this.errorMode;

            outer:
            for (;;) {

                int ac = activeCount;

                while (ac != maxConcurrency) {
                    if (cancelled) {
                        q.clear();
                        disposeAll();
                        return;
                    }

                    if (errorMode == ErrorMode.IMMEDIATE) {
                        Throwable ex = error.get();
                        if (ex != null) {
                            q.clear();
                            disposeAll();

                            a.onError(error.terminate());
                            return;
                        }
                    }

                    T v;
                    ObservableSource<? extends R> source;

                    try {
                        v = q.poll();

                        if (v == null) {
                            break;
                        }

                        source = ObjectHelper.requireNonNull(mapper.apply(v), "The mapper returned a null ObservableSource");
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        upstream.dispose();
                        q.clear();
                        disposeAll();
                        error.addThrowable(ex);
                        a.onError(error.terminate());
                        return;
                    }

                    InnerQueuedObserver<R> inner = new InnerQueuedObserver<R>(this, prefetch);

                    observers.offer(inner);

                    source.subscribe(inner);

                    ac++;
                }

                activeCount = ac;

                if (cancelled) {
                    q.clear();
                    disposeAll();
                    return;
                }

                if (errorMode == ErrorMode.IMMEDIATE) {
                    Throwable ex = error.get();
                    if (ex != null) {
                        q.clear();
                        disposeAll();

                        a.onError(error.terminate());
                        return;
                    }
                }

                InnerQueuedObserver<R> active = current;

                if (active == null) {
                    if (errorMode == ErrorMode.BOUNDARY) {
                        Throwable ex = error.get();
                        if (ex != null) {
                            q.clear();
                            disposeAll();

                            a.onError(error.terminate());
                            return;
                        }
                    }
                    boolean d = done;

                    active = observers.poll();

                    boolean empty = active == null;

                    if (d && empty) {
                        Throwable ex = error.get();
                        if (ex != null) {
                            q.clear();
                            disposeAll();

                            a.onError(error.terminate());
                        } else {
                            a.onComplete();
                        }
                        return;
                    }

                    if (!empty) {
                        current = active;
                    }

                }

                if (active != null) {
                    SimpleQueue<R> aq = active.queue();

                    for (;;) {
                        if (cancelled) {
                            q.clear();
                            disposeAll();
                            return;
                        }

                        boolean d = active.isDone();

                        if (errorMode == ErrorMode.IMMEDIATE) {
                            Throwable ex = error.get();
                            if (ex != null) {
                                q.clear();
                                disposeAll();

                                a.onError(error.terminate());
                                return;
                            }
                        }

                        R w;

                        try {
                            w = aq.poll();
                        } catch (Throwable ex) {
                            Exceptions.throwIfFatal(ex);
                            error.addThrowable(ex);

                            current = null;
                            activeCount--;
                            continue outer;
                        }

                        boolean empty = w == null;

                        if (d && empty) {
                            current = null;
                            activeCount--;
                            continue outer;
                        }

                        if (empty) {
                            break;
                        }

                        a.onNext(w);
                    }
                }

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

}