import type { Agile } from '../agile';
import { StorageKey } from './storage';
export declare class Persistent {
    agileInstance: () => Agile;
    static placeHolderKey: string;
    config: PersistentConfigInterface;
    _key: PersistentKey;
    ready: boolean;
    isPersisted: boolean;
    onLoad: ((success: boolean) => void) | undefined;
    storageKeys: StorageKey[];
    /**
     * A Persistent manages the permanent persistence
     * of an Agile Class such as the `State Class` in external Storages.
     *
     * Note that the Persistent itself is no standalone class
     * and should be adapted to the Agile Class needs it belongs to.
     *
     * @internal
     * @param agileInstance - Instance of Agile the Persistent belongs to.
     * @param config - Configuration object
     */
    constructor(agileInstance: Agile, config?: CreatePersistentConfigInterface);
    /**
     * Updates the key/name identifier of the Persistent.
     *
     * @public
     * @param value - New key/name identifier.
     */
    set key(value: StorageKey);
    /**
     * Returns the key/name identifier of the Persistent.
     *
     * @public
     */
    get key(): StorageKey;
    /**
     * Updates the key/name identifier of the Persistent.
     *
     * @public
     * @param value - New key/name identifier.
     */
    setKey(value?: StorageKey): Promise<void>;
    /**
     * Instantiates the Persistent by assigning the specified Storage keys to it
     * and validating it to make sure everything was setup correctly.
     *
     * This was moved out of the `constructor()`
     * because some classes (that extend the Persistent) need to configure some
     * things before they can properly instantiate the parent Persistent.
     *
     * @internal
     * @param config - Configuration object
     */
    instantiatePersistent(config?: InstantiatePersistentConfigInterface): void;
    /**
     * Returns a boolean indicating whether the Persistent was setup correctly
     * and is able to persist a value permanently in an external Storage.
     *
     * Based on the tapped boolean value,
     * the Persistent's `ready` property is updated.
     *
     * @internal
     */
    validatePersistent(): boolean;
    /**
     * Assigns the specified Storage identifiers to the Persistent
     * and extracts the default Storage if necessary.
     *
     * When no Storage key was provided the default Storage
     * of the Agile Instance is applied to the Persistent.
     *
     * @internal
     * @param storageKeys - Key/Name identifier of the Storages to be assigned.
     * @param defaultStorageKey - Key/Name identifier of the default Storage.
     */
    assignStorageKeys(storageKeys?: StorageKey[], defaultStorageKey?: StorageKey): void;
    /**
     * Stores or loads the Persistent value
     * from the external Storages for the first time.
     *
     * @internal
     */
    initialLoading(): Promise<void>;
    /**
     * Loads the Persistent value from the corresponding Storage.
     *
     * Note that this method should be overwritten
     * to correctly apply the changes to the Agile Class
     * the Persistent belongs to.
     *
     * @internal
     * @param storageItemKey - Storage key of the to load value.
     * | default = Persistent.key |
     * @return Whether the loading of the persisted value was successful.
     */
    loadPersistedValue(storageItemKey?: PersistentKey): Promise<boolean>;
    /**
     * Persists the Persistent value in the corresponding Storage.
     *
     * Note that this method should be overwritten
     * to correctly apply the changes to the Agile Class
     * the Persistent belongs to.
     *
     * @internal
     * @param storageItemKey - Storage key of the to persist value
     * | default = Persistent.key |
     * @return Whether the persisting of the value was successful.
     */
    persistValue(storageItemKey?: PersistentKey): Promise<boolean>;
    /**
     * Removes the Persistent value from the corresponding Storage.
     * -> Persistent value is no longer persisted
     *
     * Note that this method should be overwritten
     * to correctly apply the changes to the Agile Class
     * the Persistent belongs to.
     *
     * @internal
     * @param storageItemKey - Storage key of the to remove value.
     * | default = Persistent.key |
     * @return Whether the removal of the persisted value was successful.
     */
    removePersistedValue(storageItemKey?: PersistentKey): Promise<boolean>;
    /**
     * Formats the specified key so that it can be used as a valid Storage key
     * and returns the formatted variant of it.
     *
     * Note that this method should be overwritten
     * to correctly apply the changes to the Agile Class
     * the Persistent belongs to.
     *
     * @internal
     * @param key - Storage key to be formatted.
     */
    formatKey(key?: PersistentKey): PersistentKey | undefined;
}
export declare type PersistentKey = string | number;
export interface CreatePersistentConfigInterface {
    /**
     * Key/Name identifier of the Persistent.
     */
    key?: PersistentKey;
    /**
     * Key/Name identifier of Storages
     * in which the Persistent value is to be persisted
     * or is already persisted.
     * @default [`defaultStorageKey`]
     */
    storageKeys?: StorageKey[];
    /**
     * Key/Name identifier of the default Storage of the specified Storage keys.
     *
     * The persisted value is loaded from the default Storage by default,
     * since only one persisted value can be applied.
     * If the loading of the value from the default Storage failed,
     * an attempt is made to load the value from the remaining Storages.
     *
     * @default first index of the specified Storage keys or the Agile Instance's default Storage key
     */
    defaultStorageKey?: StorageKey;
    /**
     * Whether the Persistent should load/persist the value immediately
     * or whether this should be done manually.
     * @default true
     */
    loadValue?: boolean;
}
export interface PersistentConfigInterface {
    /**
     * Key/Name identifier of the default Storage of the specified Storage keys.
     *
     * The persisted value is loaded from the default Storage by default,
     * since only one persisted value can be applied.
     * If the loading of the value from the default Storage failed,
     * an attempt is made to load the value from the remaining Storages.
     *
     * @default first index of the specified Storage keys or the Agile Instance's default Storage key
     */
    defaultStorageKey: StorageKey | null;
}
export interface InstantiatePersistentConfigInterface {
    /**
     * Key/Name identifier of the Persistent.
     */
    key?: PersistentKey;
    /**
     * Key/Name identifier of Storages
     * in which the Persistent value is to be persisted
     * or is already persisted.
     * @default [`defaultStorageKey`]
     */
    storageKeys?: StorageKey[];
    /**
     * Key/Name identifier of the default Storage of the specified Storage keys.
     *
     * The persisted value is loaded from the default Storage by default,
     * since only one persisted value can be applied.
     * If the loading of the value from the default Storage failed,
     * an attempt is made to load the value from the remaining Storages.
     *
     * @default first index of the specified Storage keys or the Agile Instance's default Storage key
     */
    defaultStorageKey?: StorageKey;
}