src/app/theme.ts

export type ThemeMode = 'system' | 'light' | 'dark';
export type ResolvedTheme = Exclude<ThemeMode, 'system'>;

export const THEME_STORAGE_KEY = 'bonsai-theme';

export function normalizeThemeMode(value: string | null | undefined): ThemeMode {
  return value === 'light' || value === 'dark' || value === 'system' ? value : 'system';
}

export function resolveThemeMode(mode: ThemeMode, systemDark: boolean): ResolvedTheme {
  return mode === 'system' ? (systemDark ? 'dark' : 'light') : mode;
}