import { AlwaysArray, Getter } from '../types';
/**
 * Idea of this function is from Java Optional This function checks value to be non null or undefined.
 * @see https://pavel-surinin.github.io/declarativejs/#/?id=optional
 */
export interface OptionalInterface<T> {
    /**
     * Transforms object
     * @param mapper
     * @returns optional with mapped object
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=map
     */
    map<R>(mapper: Getter<T, R>): OptionalInterface<NonNullable<R>>;
    /**
     * Checks optional value against condition in predicate,
     * if condition resolve to false, empty optional will be returned
     * @param predicate
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=filter
     */
    filter(predicate: (value: T) => boolean): OptionalInterface<T>;
    /**
     * If value already known or computed use this method to return if
     * optional is empty
     * @param value
     * @returns value if optional is empty
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=orelse
     */
    orElse(value: T): T;
    /**
     * If value needs to be computed better to use lazy getter return if
     * optional is empty
     * @param value
     * @returns value if optional is empty
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=orelseget
     */
    orElseGet(supplier: () => T): T;
    /**
     * Throws an error if optional is empty.
     * @param errorMessage
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=orelsethrow
     */
    orElseThrow(errorMessage?: string): T | never;
    /**
     * @returns true is value is present
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=ispresent
     */
    isPresent(): boolean;
    /**
     * @returns true is value is absent
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=isabsent
     */
    isAbsent(): boolean;
    ifPresent(consumer: () => void): void;
    /**
     * Evaluate callback function if optional is empty
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=ifabsent
     */
    ifAbsent(consumer: () => void): void;
    /**
     * @returns value from optional
     * @throws if value is not present
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=get
     */
    get(): NonNullable<T>;
    /**
     * If value is not present, empty array will be returned,
     * if value is single cardinality returns and array from one element,
     * if value is an array returns an array.
     * @returns value converted to an array
     * @throws if value is not present
     * @see https://pavel-surinin.github.io/declarativejs/#/?id=toarray
     */
    toArray(): AlwaysArray<T>;
}
export declare const Optional: new <T>(value?: T) => OptionalInterface<T>;
export declare const optional: <T>(value?: T | undefined) => OptionalInterface<T>;