import type { CustomOptions, CustomValidate } from "../custom/types.ts";
/**
 * Determines if the input is a string.
 *
 * @param input - The value to check.
 * @param validate - Additional validation to run against the input if it is a string. Default is `undefined`.
 * @returns `true` if the input is a string, `false` otherwise.
 */
export declare function isString(input: unknown, validate?: CustomValidate<string>): input is string;
export type StringOptions = Omit<CustomOptions<string>, "typecheck">;
/**
 * Verifies that the input is a string, and returns it.
 * If the input is not a string, the fallback value is returned.
 *
 * @param input The value to check.
 * @param fallback The value to return if the input is not a string. Default is `null`.
 * @returns The string value of the input, or the fallback if the input is not a string.
 */
export declare function string(input: unknown, fallback: string, options?: StringOptions): string;
export declare function string(input: unknown, fallback?: string | null | undefined, options?: StringOptions): string | null;
export interface ToStringOptions {
    boolean?: boolean;
    date?: boolean;
    number?: boolean;
}
/**
 * Converts the input to a string.
 *
 * @param input The value to convert.
 * @param options The options to use when converting the input to a string.
 * @returns The string representation of the input, or `null` if the input is not a string, number, boolean, or date.
 */
export declare function toString(input: unknown, options?: ToStringOptions): string | null;