function enqueue(referrer, decoded, encoded, generated_from_id) {
		if (seen.has(decoded)) return;
		seen.add(decoded);

		const file = decoded.slice(config.paths.base.length + 1);
		if (files.has(file)) return;

		return q.add(() => visit(decoded, encoded || encodeURI(decoded), referrer, generated_from_id));
	}
@param {string | null} referrer
@param {string} decoded
@param {string} [encoded]
@param {string} [generated_from_id]