const { promisesAllLimit } = require('promises-all-limit')

const functionIterator = (index) => {
  // Your code goes here.
  // If there is job to run, return the next job item as a promise.
  // Otherwise, return null to indicate that all promises have been created.

  // for example
  // return (new Promise((fullfil, reject) => setTimeout(() => reject({ error: 'this is an error' }), delay)));
  // or
  // return (new Promise((fullfil, reject) => setTimeout(() => fullfil({ success: 'this is success' }), delay)));
};

const generatePromises = function * () {
  // Your code goes here.
  // If there is job to run, yield the next job item as a promise.
  // Otherwise, return to indicate that all promises have been created.

  // for example
  // for (let index = 0; index < ??? ; index++) {
  //   yield return (new Promise((fullfil, reject) => setTimeout(() => reject({ error: 'this is an error' }), delay)));
  // or
  //   yield return (new Promise((fullfil, reject) => setTimeout(() => fullfil({ success: 'this is success' }), delay)));
  // }
}

// The number of promises to process simultaneously.
const nbConcurrentJob = 5;

const run = async () => {
  try {
    const results = await promisesAllLimit(
      nbConcurrentJob, // How many to run concurrently? -1 = all / 1 = run in serie / 2..n = run in parallel with a limit
      iterator, // function or generator to create promises
      true, // continue if any promise is rejected
      (error, result, index) => { /* ... */ } // progress function
    );
    console.log('done.')
    // Will return Rejected and Fullfilled promises processed (all are processed if the 3rd parameter is true,
    // otherwise will only return results for Rejected and Fullfilled promises which were processed before the 1st Rejected promise).
    console.log(results);  
  } catch (error) {
    console.error(error);
  }
};

console.log('Starting...');
run();