encodeProtocol.js

const valid_chars =
	"!#$%&'*+-.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ^_`abcdefghijklmnopqrstuvwxyz|~";
const reserved_chars = '%';

export function validProtocol(protocol) {
	protocol = protocol.toString();

	for (let i = 0; i < protocol.length; i++) {
		const char = protocol[i];

		if (!valid_chars.includes(char)) {
			return false;
		}
	}

	return true;
}

export function encodeProtocol(protocol) {
	protocol = protocol.toString();

	let result = '';

	for (let i = 0; i < protocol.length; i++) {
		const char = protocol[i];

		if (valid_chars.includes(char) && !reserved_chars.includes(char)) {
			result += char;
		} else {
			const code = char.charCodeAt();
			result += '%' + code.toString(16).padStart(2, 0);
		}
	}

	return result;
}

export function decodeProtocol(protocol) {
	if (typeof protocol != 'string')
		throw new TypeError('protocol must be a string');

	let result = '';

	for (let i = 0; i < protocol.length; i++) {
		const char = protocol[i];

		if (char == '%') {
			const code = parseInt(protocol.slice(i + 1, i + 3), 16);
			const decoded = String.fromCharCode(code);

			result += decoded;
			i += 2;
		} else {
			result += char;
		}
	}

	return result;
}