ix/asynciterable/forkjoin.mjs

The Interactive Extensions for JavaScript

import { __awaiter } from "tslib";
import { identity } from '../util/identity.mjs';
import { wrapWithAbort } from './operators/withabort.mjs';
import { safeRace } from '../util/safeRace.mjs';
// eslint-disable-next-line @typescript-eslint/no-empty-function
const NEVER_PROMISE = new Promise(() => { });
function wrapPromiseWithIndex(promise, index) {
    return promise.then((value) => ({ value, index }));
}
/**
 * Runs all specified async-iterable sequences in parallel and collects their last elements.
 *
 * @template T The type of the elements in the source sequences.
 * @param {...any[]} sources Async-iterable sequence to collect the last elements for.
 * @returns {(Promise<T[] | undefined>)} An async-iterable sequence with an array of all the last elements of all sequences.
 */
export function forkJoin(...sources) {
    return __awaiter(this, void 0, void 0, function* () {
        let signal = sources.shift();
        if (!(signal instanceof AbortSignal)) {
            sources.unshift(signal);
            signal = undefined;
        }
        const length = sources.length;
        const iterators = new Array(length);
        const nexts = new Array(length);
        let active = length;
        const values = new Array(length);
        const hasValues = new Array(length);
        hasValues.fill(false);
        for (let i = 0; i < length; i++) {
            const iterator = wrapWithAbort(sources[i], signal)[Symbol.asyncIterator]();
            iterators[i] = iterator;
            nexts[i] = wrapPromiseWithIndex(iterator.next(), i);
        }
        while (active > 0) {
            const next = safeRace(nexts);
            const { value: next$, index } = yield next;
            if (next$.done) {
                nexts[index] = NEVER_PROMISE;
                active--;
            }
            else {
                const iterator$ = iterators[index];
                nexts[index] = wrapPromiseWithIndex(iterator$.next(), index);
                hasValues[index] = true;
                values[index] = next$.value;
            }
        }
        if (hasValues.length > 0 && hasValues.every(identity)) {
            return values;
        }
        return undefined;
    });
}

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