import { Observable } from 'rxjs';
import { StateKey } from './state-key';
/**
 * The StateHolder class follows the Singleton pattern and serves as the central repository
 * for managing application state. It stores state values in a Map and provides mechanisms
 * for putting values, observing changes, and retrieving the latest state values.
 */
export declare class StateHolder {
    private static instance;
    private stateMap;
    private constructor();
    static getInstance(): StateHolder;
    /**
     * Puts a value into the state associated with the given key. If the key does not already exist
     * in the stateMap, a new BehaviorSubject is created for it.
     * If the key exists, the value is set as the next value in the BehaviourSubject.
     *
     * @template T The type of the value to store.
     * @param key The StateKey associated with the state value.
     * @param value The value to store in the state.
     */
    put<T>(key: StateKey<T>, value: T): void;
    /**
     * Return an Observable for the provided key. If the state for the key doesn't exist,
     * a new BehaviorSubject with an initial value of undefined is created.
     * Subscribers will be notified when the state value is updated.
     *
     * @template T The type of the state value to observe.
     * @param key The StateKey associated with the state.
     * @returns An Observable that emits state updates.
     */
    observe<T>(key: StateKey<T>): Observable<T>;
    /**
     * Retrieves the latest value of the state for the provided key.
     *
     * @template T The type of the state value.
     * @param key The StateKey associated with the state.
     * @returns The latest value from the state or undefined if the state doesn't exist.
     */
    getLatest<T>(key: StateKey<T>): T | undefined;
}