is-url/index.js

"use strict";

const url = require("url");
const ValidationError = require("@validatem/error");
const isString = require("@validatem/is-string");

module.exports = function (protocols) {
	if (protocols != null && !Array.isArray(protocols)) {
		throw new Error(`Permitted protocol list must be an array`);
	}

	let protocolSet = (protocols != null)
		? new Set(protocols.map((protocol) => protocol.toLowerCase()))
		: null;

	return [
		isString,
		function isURL(value) {
			let parsed = url.parse(value);

			let slashes = (parsed.slashes === true)
				? "//"
				: "";

			let parsedProtocol = (parsed.protocol != null)
				? parsed.protocol + slashes
				: null;

			if (parsedProtocol == null) {
				return new ValidationError("Must be a valid URL");
			} else if (protocolSet != null && !protocolSet.has(parsedProtocol.toLowerCase())) {
				let validProtocolList = protocols
					.map((protocol) => protocol.toUpperCase())
					.join(", ");

				return new ValidationError(`Must be a URL with one of the following protocols: ${validProtocolList} - but got ${parsedProtocol.toUpperCase()} instead`);
			} else {
				return parsed;
			}
		}
	];
};