/**
 * Convert array to single item if only one in the array
 */
export declare const convertSingleElementArray: <T>(v: T) => T extends ArrayLike<any> ? T[number] : T;
/**
 * @returns iterable or undefined if it is empty
 */
export declare const undefinedIfEmptyArray: <T extends Iterable<any> | ArrayLike<any>>(arr: T | undefined) => T | undefined;
/**
 * Predicates to be used with filter
 */
export declare namespace predicates {
    const unique: (element: any, i: number, arr: any[]) => boolean;
    const notNullish: (element: any) => boolean;
    const notNullishUnique: (element: any, i: number, arr: any[]) => boolean;
    /**
     * Identifies items which occur more than N times
     */
    const occursMoreThan: (times: number) => (element: any) => boolean;
    /**
     * Identifies items which occur fewer than N times
     */
    const occursFewerThan: (times: number) => (element: any, i: number, arr: any[]) => boolean;
}
export declare type NestedObject<T, TChildrenKey extends string> = T & {
    [K in TChildrenKey]: NestedObject<T, TChildrenKey>[];
} & {
    flatten(): NestedObject<T, TChildrenKey>[];
};
/**
 * Takes Array of Objects and returns a flattenable array of root objects with nested children (recursively) on the objects
 * (Use res.flatten() to get a flattened array)
 * @param objects - Array of objects
 * @param primaryKey - Primary identifier key
 * @param parentKey - Key which refers to parent primary key
 * @param childrenKey - Child array will be assigned to this key
 */
export declare function nestObjects<T extends {
    [p: string]: any;
}, TChildrenKey extends string>(objects: T[], primaryKey: keyof T, parentKey: keyof T, childrenKey: TChildrenKey): NestedObject<T, TChildrenKey>[];
/**
 * Takes Array of Objects and returns a flattenable array of root objects with nested children (recursively) on the objects
 * (Use res.flatten() to get a flattened array)
 * @param objects - Array of objects
 * @param primaryKey - Primary identifier key
 * @param parentKey - Key which refers to parent primary key
 * @param childrenKey - Child array will be assigned to this key
 * @param preFormatter - Run objects through formatter before nesting
 */
export declare function nestObjects<T extends {
    [p: string]: any;
}, TChildrenKey extends string, TFormatter extends (o: T) => unknown>(objects: T[], primaryKey: keyof T, parentKey: keyof T, childrenKey: TChildrenKey, preFormatter: TFormatter): TFormatter extends () => infer U ? NestedObject<U, TChildrenKey>[] : never;