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.*;

import io.reactivex.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.operators.single.SingleZipArray.ZipCoordinator;

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

    final Iterable<? extends SingleSource<? extends T>> sources;

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

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

    @Override
    protected void subscribeActual(SingleObserver<? super R> observer) {
        @SuppressWarnings("unchecked")
        SingleSource<? extends T>[] a = new SingleSource[8];
        int n = 0;

        try {
            for (SingleSource<? extends T> source : sources) {
                if (source == null) {
                    EmptyDisposable.error(new NullPointerException("One of the sources is null"), observer);
                    return;
                }
                if (n == a.length) {
                    a = Arrays.copyOf(a, n + (n >> 2));
                }
                a[n++] = source;
            }
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            EmptyDisposable.error(ex, observer);
            return;
        }

        if (n == 0) {
            EmptyDisposable.error(new NoSuchElementException(), observer);
            return;
        }

        if (n == 1) {
            a[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;
            }

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

    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");
        }
    }
}