LukasMeine / vigilance

const pFinally = require('p-finally');

class TimeoutError extends Error {

	constructor(message) {

		super(message);

		this.name = 'TimeoutError';

	}

}

module.exports = (promise, ms, fallback) => new Promise((resolve, reject) => {

	if (typeof ms !== 'number' || ms < 0) {

		throw new TypeError('Expected `ms` to be a positive number');

	}

	const timer = setTimeout(() => {

		if (typeof fallback === 'function') {

			resolve(fallback());

			return;

		}

		const message = typeof fallback === 'string' ? fallback : `Promise timed out after ${ms} milliseconds`;

		const err = fallback instanceof Error ? fallback : new TimeoutError(message);

		reject(err);

	}, ms);

	pFinally(

		promise.then(resolve, reject),

		() => {

			clearTimeout(timer);

		}

	);

});

module.exports.TimeoutError = TimeoutError;