"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = ensureAsync;
var _setImmediate = _interopRequireDefault(require("./internal/setImmediate.js"));
var _wrapAsync = require("./internal/wrapAsync.js");
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
/**
 * Wrap an async function and ensure it calls its callback on a later tick of
 * the event loop.  If the function already calls its callback on a next tick,
 * no extra deferral is added. This is useful for preventing stack overflows
 * (`RangeError: Maximum call stack size exceeded`) and generally keeping
 * [Zalgo](http://blog.izs.me/post/59142742143/designing-apis-for-asynchrony)
 * contained. ES2017 `async` functions are returned as-is -- they are immune
 * to Zalgo's corrupting influences, as they always resolve on a later tick.
 *
 * @name ensureAsync
 * @static
 * @memberOf module:Utils
 * @method
 * @category Util
 * @param {AsyncFunction} fn - an async function, one that expects a node-style
 * callback as its last argument.
 * @returns {AsyncFunction} Returns a wrapped function with the exact same call
 * signature as the function passed in.
 * @example
 *
 * function sometimesAsync(arg, callback) {
 *     if (cache[arg]) {
 *         return callback(null, cache[arg]); // this would be synchronous!!
 *     } else {
 *         doSomeIO(arg, callback); // this IO would be asynchronous
 *     }
 * }
 *
 * // this has a risk of stack overflows if many results are cached in a row
 * async.mapSeries(args, sometimesAsync, done);
 *
 * // this will defer sometimesAsync's callback if necessary,
 * // preventing stack overflows
 * async.mapSeries(args, async.ensureAsync(sometimesAsync), done);
 */
function ensureAsync(fn) {
  if ((0, _wrapAsync.isAsync)(fn)) return fn;
  return function (...args /*, callback*/) {
    var callback = args.pop();
    var sync = true;
    args.push((...innerArgs) => {
      if (sync) {
        (0, _setImmediate.default)(() => callback(...innerArgs));
      } else {
        callback(...innerArgs);
      }
    });
    fn.apply(this, args);
    sync = false;
  };
}
module.exports = exports.default;