/**
 * Telegram and system theme detection and application.
 */

/**
 * Resolve current color scheme (dark/light).
 * @returns {"dark"|"light"}
 */
export function getTheme() {
  if (typeof window === "undefined") return "dark";
  const twa = window.Telegram?.WebApp;
  if (twa?.colorScheme) return twa.colorScheme;
  let cssScheme = "";
  try {
    cssScheme = getComputedStyle(document.documentElement)
      .getPropertyValue("--tg-color-scheme")
      .trim();
  } catch (e) {
    /* ignore */
  }
  if (cssScheme === "light" || cssScheme === "dark") return cssScheme;
  if (window.matchMedia("(prefers-color-scheme: dark)").matches) return "dark";
  return "light";
}

/**
 * Map Telegram themeParams (snake_case) to CSS variables (--tg-theme-*).
 * Only set when Telegram WebApp and themeParams are available.
 */
export function applyThemeParamsToCss() {
  const twa = window.Telegram?.WebApp;
  const params = twa?.themeParams;
  if (!params) return;
  const root = document.documentElement;
  const map = [
    ["bg_color", "bg-color"],
    ["secondary_bg_color", "secondary-bg-color"],
    ["text_color", "text-color"],
    ["hint_color", "hint-color"],
    ["link_color", "link-color"],
    ["button_color", "button-color"],
    ["header_bg_color", "header-bg-color"],
    ["accent_text_color", "accent-text-color"]
  ];
  map.forEach(([key, cssKey]) => {
    const value = params[key];
    if (value) root.style.setProperty("--tg-theme-" + cssKey, value);
  });
}

/**
 * Apply current theme: set data-theme and Telegram background/header when in TWA.
 */
export function applyTheme() {
  const scheme = getTheme();
  document.documentElement.dataset.theme = scheme;
  const twa = window.Telegram?.WebApp;
  if (twa) {
    if (twa.setBackgroundColor) twa.setBackgroundColor("bg_color");
    if (twa.setHeaderColor) twa.setHeaderColor("bg_color");
    applyThemeParamsToCss();
  }
}

/**
 * Run initial theme apply and subscribe to theme changes (TWA or prefers-color-scheme).
 * Call once at load.
 */
export function initTheme() {
  applyTheme();
  if (typeof window !== "undefined" && window.Telegram?.WebApp) {
    setTimeout(applyTheme, 0);
    setTimeout(applyTheme, 100);
  } else if (window.matchMedia) {
    window.matchMedia("(prefers-color-scheme: dark)").addEventListener("change", applyTheme);
  }
}