import { IStorageSettings } from './interfaces/storage-settings';
import { StorageReturnTypes } from './enums/storage-return-types';
import { StorageItem } from './models/storage-item';
import { Observable } from 'rxjs';
import { StorageTypes } from './enums/storage-types';
import { IStorageNotifier } from './interfaces/storage-typings';
/**
 * Provides Core functionality for StorageUtilities,
 * including getItem(), addItem(), removeItem(), removeItems(),
 * as well as additional functionality.
 */
export declare class StorageUtilities<T> {
    private static _settings;
    /**
     * An Observable type property that allows subscribers to be notified of any storage state changes.
     * @returns: { storage: StorageTypes, oldValue: T, newValue: T }
     */
    storageStateChanged: Observable<IStorageNotifier<T>>;
    constructor(settings?: IStorageSettings);
    /**
     * Get default settings applied to StorageUtilities.
     * @returns default settings
     */
    static get defaultSettings(): IStorageSettings;
    /**
     * Get current settings applied to StorageUtilities.
     * These can be either the default, custom settings, or both.
     * @returns currently applied settings
     */
    static get currentSettings(): IStorageSettings;
    /**
     * Set custom settings to be applied to StorageUtilities,
     * they always overwrite default settings.
     * @param settings the custom settings to be applied to StorageUtilities
     */
    static set customSettings(settings: IStorageSettings);
    /**
     * Reset to default settings applied to StorageUtilities.
     */
    static resetSettings(): void;
    /**
     * Returns the item stored in Storage by its key.
     * If item is not found, or it has an expiry time which has elapsed, null will be returned.
     * The item can be returned as a Promise or Observable if @param returnType is specified.
     * The item is returned from localStorage by default, or sessionStorage as specified by @param storageType.
     * @param key the item's key
     * @param storageType (optional) localStorage (default) / sessionStorage
     * @param returnType (optional) Promise / Observable
     * @returns the stored item, or null if item is not found or has expired
     */
    protected getItem(key: string, storageType?: StorageTypes, returnType?: StorageReturnTypes): T;
    /**
     * Adds the item to Storage with its key.
     * The item is added to localStorage by default, or sessionStorage if specified by @param storageType.
     * The item can be added with an expiry time (in milliseconds).
     * This is to add a TTL (Time to live) to invalidate item after the expiry time elapses.
     * @param key the item's key
     * @param item the item to be added to Storage
     * @param expiry (optional) the expiry time (in milliseconds)
     * @param storageType (optional) localStorage (default) / sessionStorage
     */
    protected addItem(key: string, item: T, expiry?: number, storageType?: StorageTypes): void;
    /**
     * Updates the value of a specific property for the stored item.
     * The property can be of any type. If the property doesn't exist, a new property will be created.
     * If the item is not found by key, or has expired, null will be returned, or updated item otherwise.
     * @param key the item's key
     * @param propName the item's property to be updated
     * @param newValue the item's property's new value
     * @param storageType (optional) localStorage (default) / sessionStorage
     * @returns the updated item, or null if item is not found or has expired
     */
    protected updateItemProperty(key: string, propName: string, newValue: any, storageType?: StorageTypes): T;
    /**
     * Removes the item's specified property.
     * If the item is not found by key, or has expired, null will be returned, or updated item otherwise.
     * @param key the item's key
     * @param propName the item's property to be removed
     * @param storageType (optional) localStorage (default) / sessionStorage
     * @returns the updated item, or null if item is not found or has expired
     */
    protected removeItemProperty(key: string, propName: string, storageType?: StorageTypes): T;
    /**
     * Removes item from Storage by its key.
     * The item is removed from localStorage by default, or sessionStorage if specified by @param storageType.
     * @param key the item's key
     * @param storageType (optional) localStorage (default) / sessionStorage
     */
    protected removeItem(key: string, storageType?: StorageTypes): void;
    /**
     * Removes items from Storage by their keys.
     * The items are removed from localStorage by default, or sessionStorage if specified by @param storageType.
     * @param keys the items' keys
     * @param storageType (optional) localStorage (default) / sessionStorage
     */
    protected removeItems(keys: string[], storageType?: StorageTypes): void;
    /**
     * Returns storage state as an Observable of type IStorageNotifier.
     * All subscribers will be notified when state changes.
     * @returns storage state of Observable type
     */
    protected getStorageState(): Observable<IStorageNotifier<T>>;
    /**
     * Returns an Array of all storage items.
     * The items are returned from localStorage by default, or sessionStorage if specified by @param storageType.
     * The items can be returned as a Promise or Observable if @param returnType is specified.
     * @param storageType (optional) localStorage (default) / sessionStorage
     * @param returnType (optional) Promise or Observable
     * @returns an Array of all storage items
     */
    protected getStorageItems(storageType?: StorageTypes, returnType?: StorageReturnTypes): StorageItem<T>[];
    /**
     * Returns an Array of all storage values.
     * The values are returned from localStorage by default, or sessionStorage if specified by @param storageType.
     * The values can be returned as a Promise or Observable if @param returnType is specified.
     * @param storageType (optional) localStorage (default) / sessionStorage
     * @param returnType (optional) Promise or Observable
     * @returns an Array of all storage values
     */
    protected getStorageValues(storageType?: StorageTypes, returnType?: StorageReturnTypes): T[];
    /**
     * Returns an Array of all storage keys.
     * The keys are returned from localStorage by default, or sessionStorage if specified by @param storageType.
     * The keys can be returned as a Promise or Observable if @param returnType is specified.
     * @param storageType (optional) localStorage (default) / sessionStorage
     * @param returnType (optional) Promise or Observable
     * @returns an Array of all storage keys
     */
    protected getStorageKeys(storageType?: StorageTypes, returnType?: StorageReturnTypes): string[];
    /**
     * Removes all items from storage.
     * The items are removed from localStorage by default, or sessionStorage if specified by @param storageType.
     * @param storageType (optional) localStorage (default) / sessionStorage
     */
    protected clearStorage(storageType?: StorageTypes): void;
    private _getDataBasedOnReturnType;
}