/**
 * Theme persistence utilities for FOUC prevention.
 *
 * Provides testable implementations of the critical-path logic
 * used in the blocking inline script (BaseLayout.astro lines 85-118)
 * and the theme-switching UI script (lines 140-230).
 */
export { DEFAULT_THEME } from './constants.js';
/**
 * Resolves the initial theme for FOUC prevention.
 *
 * Performs legacy storage migration, reads the stored theme, and validates
 * it against the provided list of valid theme IDs. Returns the default
 * theme if the stored value is missing or invalid.
 *
 * Mirrors the blocking inline script logic in BaseLayout.astro.
 */
export declare function resolveInitialTheme(windowObj: Window, validThemes: string[]): string;
/**
 * Sanitizes a base URL to prevent XSS via protocol injection.
 * Strips leading whitespace and control characters, then rejects
 * protocol-relative and absolute URLs. Only allows relative paths.
 */
export declare function sanitizeBaseUrl(raw: string): string;
/**
 * Builds the full CSS href path for a theme.
 */
export declare function buildThemeCssHref(baseUrl: string, themeId: string): string;
/**
 * Determines if the theme CSS link element needs updating.
 *
 * The default theme CSS is pre-loaded in the HTML, so we skip the
 * update to avoid an unnecessary network request and style flash.
 */
export declare function needsCssUpdate(themeId: string, defaultTheme?: string): boolean;
/** Default fallback icon filename used when no theme-specific icon is found. */
export declare const FALLBACK_ICON_FILE = "catppuccin-logo-macchiato.png";
/**
 * Builds the theme icon image src path.
 */
export declare function buildThemeIconSrc(baseUrl: string, themeIcons: Record<string, string>, themeId: string, fallbackIcon?: string): string;
/**
 * Applies the initial theme to prevent FOUC (Flash of Unstyled Content).
 *
 * This is the testable equivalent of the blocking inline script in
 * BaseLayout.astro. It:
 * 1. Migrates legacy storage keys
 * 2. Reads and validates the stored theme
 * 3. Sets the `data-theme` and `data-appearance` attributes on `<html>`
 * 4. Sets `window.__INITIAL_THEME__` for downstream scripts
 * 5. Updates the CSS link href if the theme differs from the default
 */
export declare function applyInitialTheme(doc: Document, windowObj: Window, validThemes: string[]): string;
/**
 * Updates active theme state on theme option elements.
 *
 * Toggles the `active` class on each element based on whether its
 * `data-theme-id` or `data-theme` attribute matches the given active theme ID.
 */
export declare function updateActiveTheme(options: ArrayLike<Element>, activeTheme: string): void;
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