promisify-event/index.js

"use strict";

const { validateArguments } = require("@validatem/core");
const required = require("@validatem/required");
const isNonEmptyString = require("@validatem/is-non-empty-string");
const ValiationError = require("@validatem/error");

function isEventEmitter(value) {
	if (typeof value !== "object" || value.on == null || value.removeListener == null) { 
		throw new ValiationError(`Must be an EventEmitter`);
	}
}

module.exports = function promisifyEvent(_emitter, _event) {
	let [ emitter, event ] = validateArguments(arguments, {
		emitter: [ required, isEventEmitter ],
		event: [ required, isNonEmptyString ]
	});

	return new Promise((resolve, reject) => {
		function cleanup() {
			emitter.removeListener(event, eventCallback);
			emitter.removeListener("error", eventCallback);
		}

		function eventCallback(... args) {
			resolve(... args);
			cleanup();
		}

		function errorCallback(error) {
			reject(error);
			cleanup();
		}

		emitter.on(event, eventCallback);
		emitter.on("error", errorCallback);
	});
};