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 io.reactivex.internal.functions.ObjectHelper;
import java.util.Arrays;
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.queue.SpscLinkedArrayQueue;

public final class ObservableZip<T, R> extends Observable<R> {

    final ObservableSource<? extends T>[] sources;
    final Iterable<? extends ObservableSource<? extends T>> sourcesIterable;
    final Function<? super Object[], ? extends R> zipper;
    final int bufferSize;
    final boolean delayError;

    public ObservableZip(ObservableSource<? extends T>[] sources,
            Iterable<? extends ObservableSource<? extends T>> sourcesIterable,
            Function<? super Object[], ? extends R> zipper,
            int bufferSize,
            boolean delayError) {
        this.sources = sources;
        this.sourcesIterable = sourcesIterable;
        this.zipper = zipper;
        this.bufferSize = bufferSize;
        this.delayError = delayError;
    }

    @Override
    @SuppressWarnings("unchecked")
    public void subscribeActual(Observer<? super R> observer) {
        ObservableSource<? extends T>[] sources = this.sources;
        int count = 0;
        if (sources == null) {
            sources = new Observable[8];
            for (ObservableSource<? extends T> p : sourcesIterable) {
                if (count == sources.length) {
                    ObservableSource<? extends T>[] b = new ObservableSource[count + (count >> 2)];
                    System.arraycopy(sources, 0, b, 0, count);
                    sources = b;
                }
                sources[count++] = p;
            }
        } else {
            count = sources.length;
        }

        if (count == 0) {
            EmptyDisposable.complete(observer);
            return;
        }

        ZipCoordinator<T, R> zc = new ZipCoordinator<T, R>(observer, zipper, count, delayError);
        zc.subscribe(sources, bufferSize);
    }

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

        private static final long serialVersionUID = 2983708048395377667L;
        final Observer<? super R> downstream;
        final Function<? super Object[], ? extends R> zipper;
        final ZipObserver<T, R>[] observers;
        final T[] row;
        final boolean delayError;

        volatile boolean cancelled;

        @SuppressWarnings("unchecked")
        ZipCoordinator(Observer<? super R> actual,
                Function<? super Object[], ? extends R> zipper,
                int count, boolean delayError) {
            this.downstream = actual;
            this.zipper = zipper;
            this.observers = new ZipObserver[count];
            this.row = (T[])new Object[count];
            this.delayError = delayError;
        }

        public void subscribe(ObservableSource<? extends T>[] sources, int bufferSize) {
            ZipObserver<T, R>[] s = observers;
            int len = s.length;
            for (int i = 0; i < len; i++) {
                s[i] = new ZipObserver<T, R>(this, bufferSize);
            }
            // this makes sure the contents of the observers array is visible
            this.lazySet(0);
            downstream.onSubscribe(this);
            for (int i = 0; i < len; i++) {
                if (cancelled) {
                    return;
                }
                sources[i].subscribe(s[i]);
            }
        }

        @Override
        public void dispose() {
            if (!cancelled) {
                cancelled = true;
                cancelSources();
                if (getAndIncrement() == 0) {
                    clear();
                }
            }
        }

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

        void cancel() {
            clear();
            cancelSources();
        }

        void cancelSources() {
            for (ZipObserver<?, ?> zs : observers) {
                zs.dispose();
            }
        }

        void clear() {
            for (ZipObserver<?, ?> zs : observers) {
                zs.queue.clear();
            }
        }

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

            int missing = 1;

            final ZipObserver<T, R>[] zs = observers;
            final Observer<? super R> a = downstream;
            final T[] os = row;
            final boolean delayError = this.delayError;

            for (;;) {

                for (;;) {
                    int i = 0;
                    int emptyCount = 0;
                    for (ZipObserver<T, R> z : zs) {
                        if (os[i] == null) {
                            boolean d = z.done;
                            T v = z.queue.poll();
                            boolean empty = v == null;

                            if (checkTerminated(d, empty, a, delayError, z)) {
                                return;
                            }
                            if (!empty) {
                                os[i] = v;
                            } else {
                                emptyCount++;
                            }
                        } else {
                            if (z.done && !delayError) {
                                Throwable ex = z.error;
                                if (ex != null) {
                                    cancelled = true;
                                    cancel();
                                    a.onError(ex);
                                    return;
                                }
                            }
                        }
                        i++;
                    }

                    if (emptyCount != 0) {
                        break;
                    }

                    R v;
                    try {
                        v = ObjectHelper.requireNonNull(zipper.apply(os.clone()), "The zipper returned a null value");
                    } catch (Throwable ex) {
                        Exceptions.throwIfFatal(ex);
                        cancel();
                        a.onError(ex);
                        return;
                    }

                    a.onNext(v);

                    Arrays.fill(os, null);
                }

                missing = addAndGet(-missing);
                if (missing == 0) {
                    return;
                }
            }
        }

        boolean checkTerminated(boolean d, boolean empty, Observer<? super R> a, boolean delayError, ZipObserver<?, ?> source) {
            if (cancelled) {
                cancel();
                return true;
            }

            if (d) {
                if (delayError) {
                    if (empty) {
                        Throwable e = source.error;
                        cancelled = true;
                        cancel();
                        if (e != null) {
                            a.onError(e);
                        } else {
                            a.onComplete();
                        }
                        return true;
                    }
                } else {
                    Throwable e = source.error;
                    if (e != null) {
                        cancelled = true;
                        cancel();
                        a.onError(e);
                        return true;
                    } else
                    if (empty) {
                        cancelled = true;
                        cancel();
                        a.onComplete();
                        return true;
                    }
                }
            }

            return false;
        }
    }

    static final class ZipObserver<T, R> implements Observer<T> {

        final ZipCoordinator<T, R> parent;
        final SpscLinkedArrayQueue<T> queue;

        volatile boolean done;
        Throwable error;

        final AtomicReference<Disposable> upstream = new AtomicReference<Disposable>();

        ZipObserver(ZipCoordinator<T, R> parent, int bufferSize) {
            this.parent = parent;
            this.queue = new SpscLinkedArrayQueue<T>(bufferSize);
        }

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

        @Override
        public void onNext(T t) {
            queue.offer(t);
            parent.drain();
        }

        @Override
        public void onError(Throwable t) {
            error = t;
            done = true;
            parent.drain();
        }

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

        public void dispose() {
            DisposableHelper.dispose(upstream);
        }
    }
}