node-mirai-fgo-gacha/src/parallel.js

node-mirai-sdk fgo gacha plugin

/**
 * @function parallel
 * @description run parallel jobs
 * @template T
 * @template R
 * @param { T[] } list list
 * @param { (arg: T) => Promise<R> } fn operating function
 * @param { number } limit max job num
 * @returns { Promise<R[]> }
 */
const parallel = (list, fn, limit = 5) => {
  const total = list.length;
  if (total < limit) return Promise.all(list.map(i => fn(i)));
  return new Promise((resolve, reject) => {
    const results = []
    let current = 0;
    let completed = 0;
    const runJob = index => fn(list[index]).then(res => {
      results[index] = res;
      completed += 1;
      if (current >= total) {
        if (completed >= total) return resolve(results)
      } else {
        runJob(current++)
      }
    }).catch(reject);
    for (; current < limit; current++) {
      runJob(current)
    }
  });
};

module.exports = parallel;