// Central app state + actions. Holds the session/profile, client preferences, a
// transient toast, and the latest live event (screens react to it via $effect). All
// gateway calls funnel through here so errors map to one user-facing toast and an
// expired session logs out.

import type { LinkResult, Profile, PushEvent, Session } from './model';
import { gateway } from './gateway';
import { GatewayError } from './client';
import { navigate, router } from './router.svelte';
import { errorKey, localeFrom, setLocale, t, type Locale } from './i18n/index.svelte';
import { applyReduceMotion, applyTelegramTheme, applyTheme, type ThemePref } from './theme';
import {
  insideTelegram,
  onTelegramPath,
  telegramColorScheme,
  telegramDisableVerticalSwipes,
  telegramHaptic,
  telegramLaunch,
  telegramOnEvent,
  telegramSetChrome,
} from './telegram';
import { parseStartParam } from './deeplink';
import { clearSession, loadPrefs, loadSession, saveSession, savePrefs } from './session';
import { clearGameCache } from './gamecache';
import { clearLobby } from './lobbycache';
import type { BoardLabelMode } from './boardlabels';

export interface Toast {
  kind: 'error' | 'info';
  text: string;
}

export const app = $state<{
  ready: boolean;
  session: Session | null;
  profile: Profile | null;
  toast: Toast | null;
  lastEvent: PushEvent | null;
  theme: ThemePref;
  locale: Locale;
  reduceMotion: boolean;
  boardLabels: BoardLabelMode;
  localeLocked: boolean;
  /** Pending incoming friend requests + invitations, for the lobby badge. */
  notifications: number;
}>({
  ready: false,
  session: null,
  profile: null,
  toast: null,
  lastEvent: null,
  theme: 'auto',
  locale: 'en',
  reduceMotion: false,
  boardLabels: 'beginner',
  localeLocked: false,
  notifications: 0,
});

let unsubscribeStream: (() => void) | null = null;
let streamAlive = false;
let reconnectTimer: ReturnType<typeof setTimeout> | null = null;
let toastTimer: ReturnType<typeof setTimeout> | null = null;

// Background/foreground tracking, to silence the reconnect banner during a normal app
// suspend (iOS lock / home, Telegram tab switch) and reconnect quietly on return.
let backgrounded = false;
let foregroundedAt = 0;
const reconnectGraceMs = 4000;

/** documentHidden reports whether the page is currently hidden. */
function documentHidden(): boolean {
  return typeof document !== 'undefined' && document.visibilityState === 'hidden';
}

/**
 * bannerSuppressed reports whether the connection banner should stay hidden: while
 * backgrounded, and for a short grace after returning to the foreground — a connection
 * dropped while suspended surfaces its error on resume, before the silent reconnect lands.
 */
function bannerSuppressed(): boolean {
  return backgrounded || documentHidden() || Date.now() - foregroundedAt < reconnectGraceMs;
}

function goBackground(): void {
  backgrounded = true;
}

function goForeground(): void {
  backgrounded = false;
  foregroundedAt = Date.now();
  if (!app.session) return;
  if (!streamAlive) openStream(); // silently re-establish a stream dropped while away
  void refreshNotifications();
}

export function showToast(text: string, kind: Toast['kind'] = 'info'): void {
  app.toast = { kind, text };
  if (toastTimer) clearTimeout(toastTimer);
  toastTimer = setTimeout(() => (app.toast = null), 4000);
}

/** handleError maps a GatewayError to a toast; an invalid session logs out. */
export function handleError(err: unknown): void {
  telegramHaptic('error');
  if (err instanceof GatewayError) {
    if (err.code === 'session_invalid' || err.code === 'unauthenticated') {
      void logout();
      return;
    }
    showToast(t(errorKey(err.code)), 'error');
    return;
  }
  showToast(t('error.generic'), 'error');
}

function openStream(): void {
  closeStream();
  streamAlive = true;
  unsubscribeStream = gateway.subscribe(
    (e) => {
      app.lastEvent = e;
      if (e.kind === 'chat_message' && e.message.senderId !== app.session?.userId) {
        showToast(e.message.kind === 'nudge' ? t('chat.nudge') : e.message.body, 'info');
      } else if (e.kind === 'nudge') {
        showToast(t('chat.nudge'), 'info');
      } else if (e.kind === 'your_turn') {
        showToast(t('game.yourTurn'), 'info');
      } else if (e.kind === 'match_found') {
        navigate(`/game/${e.gameId}`);
      } else if (e.kind === 'notify') {
        void refreshNotifications();
      }
    },
    () => {
      streamAlive = false;
      // A background suspend drops the single-shot stream. Keep the banner hidden while
      // backgrounded or just-resumed (bannerSuppressed); always schedule a retry.
      if (!bannerSuppressed()) showToast(t('error.unavailable'), 'error');
      scheduleReconnect();
    },
  );
}

/** scheduleReconnect reopens a dropped stream once, after a short delay, while the
 * app is in the foreground (a single pending attempt at a time). */
function scheduleReconnect(): void {
  if (reconnectTimer || !app.session) return;
  reconnectTimer = setTimeout(() => {
    reconnectTimer = null;
    if (app.session && !streamAlive && !backgrounded && !documentHidden()) openStream();
  }, 4000);
}

/**
 * refreshNotifications recomputes the lobby badge count (incoming friend requests
 * plus open invitations). Authoritative poll, complementing the live 'notify' push.
 * Guests have no social surfaces, so it is a no-op for them.
 */
export async function refreshNotifications(): Promise<void> {
  if (!app.session || app.profile?.isGuest) {
    app.notifications = 0;
    return;
  }
  try {
    const [incoming, invitations] = await Promise.all([
      gateway.friendsIncoming(),
      gateway.invitationsList(),
    ]);
    app.notifications = incoming.length + invitations.length;
  } catch {
    // Best-effort; leave the previous count on a transient failure.
  }
}

function closeStream(): void {
  if (reconnectTimer) {
    clearTimeout(reconnectTimer);
    reconnectTimer = null;
  }
  unsubscribeStream?.();
  unsubscribeStream = null;
  streamAlive = false;
}

async function adoptSession(s: Session): Promise<void> {
  gateway.setToken(s.token);
  app.session = s;
  await saveSession(s);
  try {
    app.profile = await gateway.profileGet();
    if (!app.localeLocked) setLocale(localeFrom(app.profile.preferredLanguage, app.locale));
  } catch (err) {
    handleError(err);
  }
  openStream();
  void refreshNotifications();
}

/**
 * applyLinkResult applies a completed account link or merge (Stage 11): it adopts a
 * switched session (a guest initiator whose durable counterpart won, so the active
 * account changed) or, otherwise, refreshes the current profile in place.
 */
export async function applyLinkResult(r: LinkResult): Promise<void> {
  if (r.session && r.session.token) {
    await adoptSession(r.session);
    return;
  }
  app.profile = await gateway.profileGet();
}

/**
 * syncTelegramChrome paints Telegram's header/background/bottom bar from the app's live
 * theme tokens, so the surrounding chrome matches the UI. Called after the theme is applied.
 */
function syncTelegramChrome(): void {
  if (typeof document === 'undefined') return;
  const cs = getComputedStyle(document.documentElement);
  telegramSetChrome(
    cs.getPropertyValue('--bg-elev').trim(),
    cs.getPropertyValue('--bg').trim(),
    cs.getPropertyValue('--bg-elev').trim(),
  );
}

export async function bootstrap(): Promise<void> {
  const prefs = await loadPrefs();
  app.theme = prefs.theme ?? 'auto';
  app.reduceMotion = prefs.reduceMotion ?? false;
  app.boardLabels = prefs.boardLabels ?? 'beginner';
  applyTheme(app.theme);
  applyReduceMotion(app.reduceMotion);
  if (prefs.locale) {
    app.locale = prefs.locale;
    app.localeLocked = true;
    setLocale(prefs.locale);
  } else {
    const guess = localeFrom(typeof navigator !== 'undefined' ? navigator.language : 'en');
    app.locale = guess;
    setLocale(guess);
  }

  // Telegram Mini App launch: apply the platform theme, authenticate via initData,
  // and route any deep-link start parameter. On the dedicated /telegram/ entry path
  // outside Telegram (no initData), refuse to render and send the visitor to the
  // site root.
  if (onTelegramPath() && !insideTelegram()) {
    if (typeof location !== 'undefined') location.replace('/');
    return;
  }
  if (insideTelegram()) {
    const launch = telegramLaunch();
    if (launch.theme) applyTelegramTheme(launch.theme);
    // Inside Telegram the colour scheme is Telegram's to decide; force it explicitly
    // so the OS prefers-color-scheme (which leaks into the Telegram Desktop webview)
    // cannot fight it. Falls back to the stored preference when the SDK omits it.
    applyTheme(telegramColorScheme() ?? app.theme);
    // Match Telegram's chrome to the app and stop its swipe-down-to-minimise from
    // fighting tile drag / board scroll.
    syncTelegramChrome();
    telegramDisableVerticalSwipes();
    try {
      await adoptSession(await gateway.authTelegram(launch.initData));
      await routeStartParam(launch.startParam);
    } catch (err) {
      handleError(err);
      navigate('/login');
    }
    app.ready = true;
    return;
  }

  const saved = await loadSession();
  if (saved) {
    await adoptSession(saved);
    if (router.route.name === 'login') navigate('/');
  } else if (router.route.name !== 'login') {
    navigate('/login');
  }
  app.ready = true;
}

/**
 * routeStartParam navigates a Telegram deep-link start parameter to its target: a
 * specific game, the friends screen with a friend-code redemption, or the lobby
 * (where invitations surface as a badge).
 */
async function routeStartParam(param: string): Promise<void> {
  const link = parseStartParam(param);
  switch (link.kind) {
    case 'game':
      navigate(`/game/${link.id}`);
      return;
    case 'friendCode':
      navigate('/friends');
      try {
        const friend = await gateway.friendCodeRedeem(link.code);
        showToast(t('friends.added', { name: friend.displayName }));
        void refreshNotifications();
      } catch (err) {
        handleError(err);
      }
      return;
    default:
      navigate('/');
  }
}

export async function loginGuest(): Promise<void> {
  try {
    const s = await gateway.authGuest(app.locale);
    await adoptSession(s);
    navigate('/');
  } catch (err) {
    handleError(err);
  }
}

export async function requestEmailCode(email: string): Promise<boolean> {
  try {
    await gateway.authEmailRequest(email);
    return true;
  } catch (err) {
    handleError(err);
    return false;
  }
}

export async function loginEmail(email: string, code: string): Promise<void> {
  try {
    const s = await gateway.authEmailLogin(email, code);
    await adoptSession(s);
    navigate('/');
  } catch (err) {
    handleError(err);
  }
}

export async function logout(): Promise<void> {
  closeStream();
  clearGameCache();
  clearLobby();
  gateway.setToken(null);
  await clearSession();
  app.session = null;
  app.profile = null;
  navigate('/login');
}

function persistPrefs(): void {
  void savePrefs({
    theme: app.theme,
    locale: app.locale,
    reduceMotion: app.reduceMotion,
    boardLabels: app.boardLabels,
  });
}

export function setTheme(theme: ThemePref): void {
  app.theme = theme;
  applyTheme(theme);
  persistPrefs();
}

export function setLocalePref(locale: Locale): void {
  app.locale = locale;
  app.localeLocked = true;
  setLocale(locale);
  persistPrefs();
  void persistLanguageToServer(locale);
}

/**
 * persistLanguageToServer writes the chosen interface language through to the
 * durable account's preferred_language, so the single Settings control is the
 * source of truth (guests keep only the client preference). Best-effort.
 */
async function persistLanguageToServer(locale: Locale): Promise<void> {
  const p = app.profile;
  if (!p || p.isGuest || p.preferredLanguage === locale) return;
  try {
    app.profile = await gateway.profileUpdate({
      displayName: p.displayName,
      preferredLanguage: locale,
      timeZone: p.timeZone,
      awayStart: p.awayStart,
      awayEnd: p.awayEnd,
      blockChat: p.blockChat,
      blockFriendRequests: p.blockFriendRequests,
      notificationsInAppOnly: p.notificationsInAppOnly,
    });
  } catch {
    // The client locale already changed; the server sync is best-effort.
  }
}

export function setReduceMotion(on: boolean): void {
  app.reduceMotion = on;
  applyReduceMotion(on);
  persistPrefs();
}

export function setBoardLabels(mode: BoardLabelMode): void {
  app.boardLabels = mode;
  persistPrefs();
}

// Background/foreground lifecycle: silence the reconnect banner during a suspend and
// reconnect quietly on return (and refresh the lobby badge for any push missed while
// hidden, §10). Several signals cover the platforms: the page Visibility API, the
// pageshow/pagehide pair (iOS), and Telegram's own activated/deactivated (Bot API 8.0).
if (typeof document !== 'undefined') {
  document.addEventListener('visibilitychange', () =>
    document.visibilityState === 'visible' ? goForeground() : goBackground(),
  );
}
if (typeof window !== 'undefined') {
  window.addEventListener('pageshow', goForeground);
  window.addEventListener('pagehide', goBackground);
}
telegramOnEvent('activated', goForeground);
telegramOnEvent('deactivated', goBackground);