maximize-iterator/dist/esm/createProcessor.js

Maximize the parallel calls of an iterator supporting asyncIterator interface

import compat from 'async-compat';
const isError = (err)=>err && err.stack !== undefined && err.message !== undefined;
function processDone(err, options, callback) {
    options.err = options.err || err;
    options.done = true;
    if (!options.done || options.counter > 0) return false;
    callback(options.err, options.done);
    return true;
}
function processResult(err, keep, options, callback) {
    options.counter--;
    if (err && compat.defaultValue(options.error(err), false) || !err && !compat.defaultValue(keep, true)) {
        options.err = options.err || err;
        options.done = true;
    }
    if (!options.done || options.counter > 0) return false;
    callback(options.err, options.done);
    return true;
}
export default function createProcessor(next, options, callback) {
    let flushing = false;
    function callDefer(err, keep) {
        const shouldContinue = !processResult(err, keep, options, callback);
        if (flushing) return;
        if (shouldContinue) flush();
    }
    function flush() {
        flushing = true;
        while(options.counter < options.concurrency){
            if (options.done || !options.canProcess()) break;
            if (options.total >= options.limit) {
                processDone(null, options, callback);
                flushing = false;
                return;
            }
            options.total++;
            options.counter++;
            next((err, result)=>{
                if (err || result.done) {
                    return callDefer(err, false);
                }
                compat.asyncFunction(options.each, options.callbacks, result.value, (err, keep)=>callDefer(err, keep));
            });
        }
        flushing = false;
    }
    return function processor(doneOrError) {
        const error = doneOrError;
        if (doneOrError && processDone(isError(error) ? error : null, options, callback)) return;
        flush();
    };
}