export declare const ADD_NEW: unique symbol;
/**
 * Default function to convert an item to a string representation
 * @template Item - The type of the item
 * @param item - The item to convert to string
 * @returns String representation of the item or empty string if null/undefined
 */
export declare const defaultItemToString: <Item>(item: Item | null) => string;
/**
 * Default function to generate a unique key for an item
 * @template Item - The type of the item
 * @param item - The item to generate a key for
 * @returns The item itself as the key
 */
export declare const defaultItemToKey: <Item>(item: Item | null) => Item | null;
/**
 * Hook to handle downshift environment configuration for shadow DOM support
 *
 * Features:
 * - Fixes shadow DOM compatibility issues with downshift
 * - Provides proper document and event listener references
 * - Returns ref for wrapper element and environment configuration
 *
 * @returns Object containing ref and environment configuration
 *
 * @example
 * const { ref, environment } = useDownshiftEnvironment();
 *
 * return (
 *   <div ref={ref}>
 *     <Combobox environment={environment}>
 *       combobox content
 *     </Combobox>
 *   </div>
 * );
 */
export declare const useDownshiftEnvironment: () => {
    ref: import('react').MutableRefObject<HTMLDivElement | null>;
    environment: {
        document: Document;
        addEventListener: {
            <K extends keyof DocumentEventMap>(type: K, listener: (this: Document, ev: DocumentEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
            (type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
        };
        removeEventListener: {
            <K extends keyof DocumentEventMap>(type: K, listener: (this: Document, ev: DocumentEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
            (type: string, listener: EventListenerOrEventListenerObject, options?: boolean | EventListenerOptions): void;
        };
        Node: {
            new (): Node;
            prototype: Node;
            readonly ELEMENT_NODE: 1;
            readonly ATTRIBUTE_NODE: 2;
            readonly TEXT_NODE: 3;
            readonly CDATA_SECTION_NODE: 4;
            readonly ENTITY_REFERENCE_NODE: 5;
            readonly ENTITY_NODE: 6;
            readonly PROCESSING_INSTRUCTION_NODE: 7;
            readonly COMMENT_NODE: 8;
            readonly DOCUMENT_NODE: 9;
            readonly DOCUMENT_TYPE_NODE: 10;
            readonly DOCUMENT_FRAGMENT_NODE: 11;
            readonly NOTATION_NODE: 12;
            readonly DOCUMENT_POSITION_DISCONNECTED: 1;
            readonly DOCUMENT_POSITION_PRECEDING: 2;
            readonly DOCUMENT_POSITION_FOLLOWING: 4;
            readonly DOCUMENT_POSITION_CONTAINS: 8;
            readonly DOCUMENT_POSITION_CONTAINED_BY: 16;
            readonly DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC: 32;
        };
    } | undefined;
};