/**
 * browser.ts — feature-detected browser identifier shared by background,
 * popup, and content scripts.
 *
 * The discriminator is feature presence + extension URL scheme, not user
 * agent string. `chrome.webAuthenticationProxy` is Chrome-only; the
 * `moz-extension://` URL scheme tells us we are running under Firefox.
 */

export type Browser = "chrome" | "firefox" | "unknown";

export function detectBrowser(): Browser {
  if (typeof chrome === "undefined") return "unknown";
  // chrome.webAuthenticationProxy exists on Chrome 122+ regardless of
  // whether it has been attached. Treat its mere presence as the discriminator.
  if ((chrome as unknown as { webAuthenticationProxy?: unknown }).webAuthenticationProxy) {
    return "chrome";
  }
  try {
    const url = chrome.runtime?.getURL?.("") ?? "";
    if (url.startsWith("moz-extension://")) return "firefox";
  } catch { /* extension context unavailable */ }
  return "unknown";
}

/**
 * Best-effort Firefox version detection. Used to gate the Firefox passkey
 * path on Firefox 150+. Returns NaN for non-Firefox or when we can't parse.
 */
export function firefoxVersion(): number {
  if (detectBrowser() !== "firefox") return NaN;
  const match = navigator.userAgent.match(/Firefox\/(\d+)/);
  return match ? Number(match[1]) : NaN;
}