rubico/_internal/asyncGeneratorFunctionForEach.js

[a]synchronous functional programming

const isPromise = require('./isPromise')
const promiseAll = require('./promiseAll')
const always = require('./always')

/**
 * @name asyncGeneratorFunctionForEach
 *
 * @synopsis
 * ```coffeescript [specscript]
 * var T any,
 *   asyncGeneratorFunction ...args=>AsyncGenerator<T>,
 *   callback T=>()
 *
 * asyncGeneratorFunctionForEach(asyncGeneratorFunction, callback) -> ...args=>Promise<AsyncGenerator<>>
 * ```
 *
 * @description
 * Create an async generator executor that executes a callback for each item of an async generator generated by an async generator function.
 */
const asyncGeneratorFunctionForEach = (
  asyncGeneratorFunction, callback,
) => async function* executingCallbackForEach(...args) {
  const promises = [],
    asyncIterator = asyncGeneratorFunction(...args)
  for await (const item of asyncIterator) {
    const operation = callback(item)
    if (isPromise(operation)) {
      promises.push(operation)
    }
  }
  return promises.length == 0 ? asyncIterator
    : promiseAll(promises).then(always(asyncIterator))
}

module.exports = asyncGeneratorFunctionForEach