/**
 * Masks a value by keeping the first and last characters and replacing the
 * middle with a repeated character.
 *
 * Behavior:
 * - Falsy values (undefined/null/'') return ''.
 * - Values with a length of 2 or less are returned unchanged.
 * - When `compactLength` is greater than 0, the middle is replaced with
 *   `character` repeated `compactLength` times, regardless of the value's
 *   length — long values stay compact and don't reveal their true length.
 * - When `compactLength` is 0, the middle is masked at the value's true length
 *   (length - 2 characters).
 */
export declare function maskValue(value: string | undefined, compactLength: number, character: string): string;