/**
 * @purpose Compute the Damerau-Levenshtein distance between two strings.
 * @invariant Supports insertion, deletion, substitution, transposition; distance 0 for identical strings.
 * @param a First string.
 * @param b Second string.
 * @returns Edit distance (non-negative integer).
 */
export declare function damerauLevenshtein(a: string, b: string): number;
/**
 * @purpose Determine if two strings match within the fuzzy threshold.
 * @invariant Threshold <=2 for strings of length <=5; <=3 for length >5.
 * @param query Requested term.
 * @param candidate Indexed term to compare against.
 * @returns True when DL distance is within the applicable threshold.
 */
export declare function isFuzzyMatch(query: string, candidate: string): boolean;
/**
 * @purpose Compute DL distance and return it with the match verdict.
 * @param query Requested term.
 * @param candidate Indexed term to compare against.
 * @returns Distance value and whether it is within the threshold.
 */
export declare function fuzzyDistance(query: string, candidate: string): {
    distance: number;
    match: boolean;
};