'use strict'

// https://github.com/jprichardson/node-fs-extra/issues/1056
// Performing parallel operations on each item of an async iterator is
// surprisingly hard; you need to have handlers in place to avoid getting an
// UnhandledPromiseRejectionWarning.
// NOTE: This function does not presently handle return values, only errors
async function asyncIteratorConcurrentProcess (iterator, fn) {
  const promises = []
  for await (const item of iterator) {
    promises.push(
      fn(item).then(
        () => null,
        (err) => err ?? new Error('unknown error')
      )
    )
  }
  await Promise.all(
    promises.map((promise) =>
      promise.then((possibleErr) => {
        if (possibleErr !== null) throw possibleErr
      })
    )
  )
}

module.exports = {
  asyncIteratorConcurrentProcess
}