/**
 * Storage utilities for theme persistence
 */
export { DEFAULT_THEME } from './constants.js';
/**
 * Validates a theme ID against a set of valid IDs.
 * Returns the theme ID if valid, otherwise returns the default theme.
 */
export declare function validateThemeId(themeId: string | null, validIds: Set<string>): string;
/**
 * Migrates legacy storage keys to the current format.
 * Safely handles unavailable localStorage (e.g., private browsing).
 */
export declare function migrateLegacyStorage(windowObj: Window): void;
/**
 * Gets the saved theme from localStorage, or returns default.
 * Optionally validates against a set of valid theme IDs.
 * Safely handles unavailable localStorage (e.g., private browsing).
 */
export declare function getSavedTheme(windowObj: Window, validIds?: Set<string>): string;
/**
 * Saves a theme to localStorage.
 * Optionally validates the theme ID against a set of valid IDs before saving.
 * Safely handles unavailable localStorage (e.g., private browsing).
 *
 * @param windowObj - Window object with localStorage
 * @param themeId - Theme ID to save
 * @param validIds - Optional set of valid theme IDs for validation
 * @returns true if saved successfully, false otherwise
 */
export declare function saveTheme(windowObj: Window, themeId: string, validIds?: Set<string>): boolean;
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