generatorFunctionForEach.js

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

/**
 * @name generatorFunctionForEach
 *
 * @synopsis
 * ```coffeescript [specscript]
 * var T any,
 *   generatorFunction ...args=>Generator<T>,
 *   callback T=>()
 *
 * generatorFunctionForEach(generatorFunction, callback) -> ...args=>Promise|Generator<>
 * ```
 *
 * @description
 * Create a generator executor that executes a callback for each item of a generator generated by a generator function. The executor may return a promise if any execution is asynchronous.
 */
const generatorFunctionForEach = (
  generatorFunction, callback,
) => function* executingCallbackForEach(...args) {
  const promises = [],
    generator = generatorFunction(...args)
  for (const item of generator) {
    const operation = callback(item)
    if (isPromise(operation)) {
      promises.push(operation)
    }
  }
  return promises.length == 0 ? generator
    : promiseAll(promises).then(always(generator))
}

module.exports = generatorFunctionForEach