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| 'use strict';
| const pTry = require('p-try');
|
| module.exports = concurrency => {
| if (concurrency < 1) {
| throw new TypeError('Expected `concurrency` to be a number from 1 and up');
| }
|
| const queue = [];
| let activeCount = 0;
|
| const next = () => {
| activeCount--;
|
| if (queue.length > 0) {
| queue.shift()();
| }
| };
|
| return fn => new Promise((resolve, reject) => {
| const run = () => {
| activeCount++;
|
| pTry(fn).then(
| val => {
| resolve(val);
| next();
| },
| err => {
| reject(err);
| next();
| }
| );
| };
|
| if (activeCount < concurrency) {
| run();
| } else {
| queue.push(run);
| }
| });
| };
|
|
