// Tells the app which account is signed in inside this tab's profile, so the account switcher
// lists real logins (avatar, name, handle) instead of hand-named slots. Read from the site's own
// UI, which the site renders anyway; nothing is requested. Only a change is reported (`tab_report`),
// and native code accepts it only from a webview that is on the site, for that webview's own profile.

import { watchDom } from './domHub.ts';

export type SeenAccount = { handle: string; name: string; avatar: string | null };
export type AccountReport = { account: SeenAccount } | { signedOut: true };

export type AccountSite = {
  /** The account the site's UI shows, or null when there is none (yet). Pure over the DOM. */
  read(root: ParentNode): SeenAccount | null;
  /** The site shows its signed-out page. */
  signedOut(root: ParentNode): boolean;
};

export type Invoke = (command: string, args: Record<string, unknown>) => Promise<unknown>;

export function installAccountReport(win: Window, site: AccountSite, invoke?: Invoke) {
  if (!invoke) return { dispose() {} };
  let last = '';
  const send = (report: AccountReport) => {
    const key = JSON.stringify(report);
    if (key === last) return;
    last = key;
    invoke('tab_report', { report }).catch(() => { last = ''; });
  };
  const check = () => {
    const account = site.read(win.document);
    if (account) send({ account });
    else if (site.signedOut(win.document)) send({ signedOut: true });
  };
  return watchDom(win as unknown as Parameters<typeof watchDom>[0], check);
}