PromisifyII

const customPromisifySymbol = Symbol.for('nodejs.util.promisify.custom');
const legacyCustomPromisifySymbol = Symbol.for('util.promisify.custom');

/**
 * Improves callback-style APIs by returning Promise-based versions,
 * so they can be consumed with async/await and Promise chaining.
 *
 * For non-standard callback signatures, callers can define
 * `func[promisify.custom]` to fully override how promisification works.
 *
 * @param {Function} func - Function to promisify
 * @returns {Function} A promisified version of `func`
 */
function promisify(func) {
	if (typeof func !== 'function') {
		throw new TypeError('The "func" argument must be of type function.');
	}

	const custom =
		func[customPromisifySymbol] !== undefined
			? func[customPromisifySymbol]
			: func[legacyCustomPromisifySymbol];
	if (custom !== undefined) {
		if (typeof custom !== 'function') {
			throw new TypeError('The "util.promisify.custom" argument must be of type function.');
		}
		// Respect explicit custom promisification logic for legacy/non-standard APIs.
		return custom;
	}

	// Default path: wraps Node-style callback-last `(err, value)` functions.
	return function (...args) {
		return new Promise((resolve, reject) => {
			func.call(this, ...args, (err, value) => {
				if (err) {
					reject(err);
				} else {
					resolve(value);
				}
			});
		});
	};
}

promisify.custom = customPromisifySymbol;

export default promisify;