// Theme application. The design tokens are CSS custom properties (app.css); here we
// only flip how they resolve: 'auto' follows the OS, 'light'/'dark' force a value via
// [data-theme]. A Telegram Mini App can additionally override the token values from
// WebApp.themeParams — the mapping lives here so the token system is Telegram-ready,
// while the SDK is wired in the Telegram stage.

export type ThemePref = 'auto' | 'light' | 'dark';

export function applyTheme(pref: ThemePref): void {
  if (typeof document === 'undefined') return;
  const root = document.documentElement;
  if (pref === 'auto') root.removeAttribute('data-theme');
  else root.setAttribute('data-theme', pref);
}

export function applyReduceMotion(on: boolean): void {
  if (typeof document === 'undefined') return;
  document.body.classList.toggle('reduce-motion', on);
}

/** Subset of Telegram WebApp.themeParams we map onto our tokens. */
export interface TelegramThemeParams {
  bg_color?: string;
  text_color?: string;
  hint_color?: string;
  link_color?: string;
  button_color?: string;
  button_text_color?: string;
  secondary_bg_color?: string;
  header_bg_color?: string;
}

/** applyTelegramTheme overrides token values at runtime from Telegram themeParams. */
export function applyTelegramTheme(p: TelegramThemeParams): void {
  if (typeof document === 'undefined') return;
  const root = document.documentElement;
  const set = (value: string | undefined, name: string) => {
    if (value) root.style.setProperty(name, value);
  };
  set(p.bg_color, '--bg');
  set(p.bg_color, '--surface');
  set(p.secondary_bg_color, '--surface-2');
  set(p.text_color, '--text');
  set(p.hint_color, '--text-muted');
  set(p.button_color, '--accent');
  set(p.button_text_color, '--accent-text');
  set(p.link_color, '--accent');
  // The nav bar tracks Telegram's chrome so it doesn't fall out of the design; the
  // announcement banner takes the secondary surface so it reads as a subtle accent.
  set(p.header_bg_color ?? p.bg_color, '--bg-elev');
  set(p.secondary_bg_color, '--ad-bg');
}