import { APP_VERSION, DEBUG } from '../config';
import { getGlobal } from '../lib/teact/teactn';
import { hasStoredSession } from './sessions';

const WEBSYNC_URLS = [
  't.me',
  'telegram.me',
].map((domain) => `//${domain}/_websync_?`);
const WEBSYNC_VERSION = `${APP_VERSION} Z`;
const WEBSYNC_KEY = 'tgme_sync';
const WEBSYNC_TIMEOUT = 86400;

const getTs = () => {
  return Math.floor(Number(new Date()) / 1000);
};

const saveSync = (authed: boolean) => {
  const ts = getTs();
  localStorage.setItem(WEBSYNC_KEY, JSON.stringify({
    canRedirect: authed,
    ts,
  }));
};

let lastTimeout: NodeJS.Timeout | undefined;

export const forceWebsync = (authed: boolean) => {
  const currentTs = getTs();

  const { canRedirect, ts } = JSON.parse(localStorage.getItem(WEBSYNC_KEY) || '{}');

  if (canRedirect !== authed || ts + WEBSYNC_TIMEOUT <= currentTs) {
    return Promise.all(WEBSYNC_URLS.map((url) => {
      return new Promise<void>((resolve, reject) => {
        const script = document.createElement('script');

        const removeElement = () => Boolean(document.body.removeChild(script));

        script.src = url + new URLSearchParams({
          authed: Number(authed).toString(),
          version: WEBSYNC_VERSION,
        });

        document.body.appendChild(script);

        script.onload = () => {
          saveSync(authed);
          removeElement();
          if (lastTimeout) {
            clearTimeout(lastTimeout);
            lastTimeout = undefined;
          }
          startWebsync();
          resolve();
        };

        script.onerror = () => {
          removeElement();
          reject();
        };
      });
    }));
  } else {
    return Promise.resolve();
  }
};

export function startWebsync() {
  if (DEBUG) {
    return;
  }

  if (lastTimeout !== undefined) return;
  const currentTs = getTs();

  const { ts } = JSON.parse(localStorage.getItem(WEBSYNC_KEY) || '{}');

  const timeout = WEBSYNC_TIMEOUT - (currentTs - ts);

  lastTimeout = setTimeout(() => {
    const { authState } = getGlobal();

    const authed = authState === 'authorizationStateReady' || hasStoredSession(true);
    forceWebsync(authed);
  }, Math.max(0, timeout * 1000));
}

export function clearWebsync() {
  localStorage.removeItem(WEBSYNC_KEY);
}