/**
 * Theme values (BR-3: only 'red' and 'purple' are valid).
 * Actual token colors live in src/index.css (.theme-red / .theme-purple);
 * this module only owns the *selectable* theme identifiers and the
 * localStorage key used for persistence (BR-2).
 */

export type ThemeName = 'red' | 'purple';

export const THEMES: ThemeName[] = ['red', 'purple'];

export const DEFAULT_THEME: ThemeName = 'red';

export const THEME_STORAGE_KEY = 'slp-software-theme';

/** BR-3: fall back to the default theme for anything that isn't a valid ThemeName. */
export function isValidTheme(value: unknown): value is ThemeName {
  return value === 'red' || value === 'purple';
}

export function resolveInitialTheme(storedValue: string | null): ThemeName {
  if (isValidTheme(storedValue)) {
    return storedValue;
  }
  return DEFAULT_THEME;
}

export function themeClassName(theme: ThemeName): string {
  return `theme-${theme}`;
}