import { Ctor, JsonObj, Nil } from "./types";
/**
 * isNullish
 * Typeguard - check a value is undefined or null
 */
export declare const isNil: (value: unknown) => value is Nil;
/**
 * notNil
 * Typeguard - check a value is neither undefined or null
 * @see isNil
 */
export declare const notNil: <T>(value: T | Nil) => value is T;
/**
 * isEmpty
 * Logic - check a given value is considered empty
 * empty depends on typeof value:
 * - null
 * - undefined
 * - array: length = 0
 * - string: length = 0
 * @see isNil
 * @see isString
 * @see isArray
 */
export declare const isEmpty: (value: unknown) => value is Nil;
/**
 * isObject
 * Typeguard - check a value is an object in the conceptual sense not the JS sense
 * excluding JS overlap with:
 *   null
 *   Arrays
 *   Functions
 */
export declare const isObject: <T>(value: T) => value is Exclude<T & Record<string, any>, Nil | any[] | ((...args: any) => any)>;
/**
 * isString
 * TypeGuard to check a value is a string
 */
export declare const isString: (value: unknown) => value is string;
/**
 * notEmptyString
 * Typeguard + Logic - check a value is a string with contents
 */
export declare const notEmptyString: (value: unknown) => value is string;
/**
 * isArray
 * Typeguard - check a value is an Array
 */
export declare const isArray: (value: unknown) => value is unknown[];
/**
 * notEmptyArray
 * Typeguard + Logic - check a value is an Array with contents
 */
/**
 * asArray
 * convert a value to an array
 * @param items - the value to be converted
 *   - nullish returns empty array
 *   - single item returns array with item
 *   - array returns array
 * @param guard? - optional Typeguard to filter items ensuring item types
 */
export declare function asArray<T>(items: T | T[] | Nil): T[];
export declare function asArray<T, U extends T>(items: T | T[] | Nil, guard: (item: unknown) => item is U): U[];
export declare const asJsonObj: (value: unknown) => JsonObj;
/**
 * expect
 * assert a value is notNil and return the value typed as such
 * panic otherwise
 *
 * @param value - the value to check
 * @param error? - custom error
 */
export declare function expect<T>(value: T, error?: string | Ctor<Error> | Error): Exclude<T, Nil>;