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.single;

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.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.plugins.RxJavaPlugins;

public final class SingleZipArray<T, R> extends Single<R> {

    final SingleSource<? extends T>[] sources;

    final Function<? super Object[], ? extends R> zipper;

    public SingleZipArray(SingleSource<? extends T>[] sources, Function<? super Object[], ? extends R> zipper) {
        this.sources = sources;
        this.zipper = zipper;
    }

    @Override
    protected void subscribeActual(SingleObserver<? super R> observer) {
        SingleSource<? extends T>[] sources = this.sources;
        int n = sources.length;

        if (n == 1) {
            sources[0].subscribe(new SingleMap.MapSingleObserver<T, R>(observer, new SingletonArrayFunc()));
            return;
        }

        ZipCoordinator<T, R> parent = new ZipCoordinator<T, R>(observer, n, zipper);

        observer.onSubscribe(parent);

        for (int i = 0; i < n; i++) {
            if (parent.isDisposed()) {
                return;
            }

            SingleSource<? extends T> source = sources[i];

            if (source == null) {
                parent.innerError(new NullPointerException("One of the sources is null"), i);
                return;
            }

            source.subscribe(parent.observers[i]);
        }
    }

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

        private static final long serialVersionUID = -5556924161382950569L;

        final SingleObserver<? super R> downstream;

        final Function<? super Object[], ? extends R> zipper;

        final ZipSingleObserver<T>[] observers;

        final Object[] values;

        @SuppressWarnings("unchecked")
        ZipCoordinator(SingleObserver<? super R> observer, int n, Function<? super Object[], ? extends R> zipper) {
            super(n);
            this.downstream = observer;
            this.zipper = zipper;
            ZipSingleObserver<T>[] o = new ZipSingleObserver[n];
            for (int i = 0; i < n; i++) {
                o[i] = new ZipSingleObserver<T>(this, i);
            }
            this.observers = o;
            this.values = new Object[n];
        }

        @Override
        public boolean isDisposed() {
            return get() <= 0;
        }

        @Override
        public void dispose() {
            if (getAndSet(0) > 0) {
                for (ZipSingleObserver<?> d : observers) {
                    d.dispose();
                }
            }
        }

        void innerSuccess(T value, int index) {
            values[index] = value;
            if (decrementAndGet() == 0) {
                R v;

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

                downstream.onSuccess(v);
            }
        }

        void disposeExcept(int index) {
            ZipSingleObserver<T>[] observers = this.observers;
            int n = observers.length;
            for (int i = 0; i < index; i++) {
                observers[i].dispose();
            }
            for (int i = index + 1; i < n; i++) {
                observers[i].dispose();
            }
        }

        void innerError(Throwable ex, int index) {
            if (getAndSet(0) > 0) {
                disposeExcept(index);
                downstream.onError(ex);
            } else {
                RxJavaPlugins.onError(ex);
            }
        }
    }

    static final class ZipSingleObserver<T>
    extends AtomicReference<Disposable>
    implements SingleObserver<T> {

        private static final long serialVersionUID = 3323743579927613702L;

        final ZipCoordinator<T, ?> parent;

        final int index;

        ZipSingleObserver(ZipCoordinator<T, ?> parent, int index) {
            this.parent = parent;
            this.index = index;
        }

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

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

        @Override
        public void onSuccess(T value) {
            parent.innerSuccess(value, index);
        }

        @Override
        public void onError(Throwable e) {
            parent.innerError(e, index);
        }
    }

    final class SingletonArrayFunc implements Function<T, R> {
        @Override
        public R apply(T t) throws Exception {
            return ObjectHelper.requireNonNull(zipper.apply(new Object[] { t }), "The zipper returned a null value");
        }
    }
}