/**
 * Build a hint index for a ruleset. Each rule pair gets the best
 * keyword hint from its regexes. Rules with no extractable hint
 * are marked null (always run).
 *
 * @param {Array} ruleset
 * @returns {Array<string|null>}
 */
export function buildHintIndex(ruleset: any[]): Array<string | null>;
/**
 * Like applyRules but skips rule pairs whose hint keyword
 * is not found in the (lowercased) UA string.
 *
 * @param {string} ua
 * @param {string} uaLower - pre-lowercased UA
 * @param {Array} ruleset
 * @param {Array<string|null>} hints
 * @returns {Record<string, string|undefined>}
 */
export function applyRulesFiltered(ua: string, uaLower: string, ruleset: any[], hints: Array<string | null>): Record<string, string | undefined>;