// 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 { 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, applyTheme, type ThemePref } from './theme';
import { clearSession, loadPrefs, loadSession, saveSession, savePrefs } from './session';
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 toastTimer: ReturnType<typeof setTimeout> | null = null;

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 {
  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();
  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();
      }
    },
    () => showToast(t('error.unavailable'), 'error'),
  );
}

/**
 * 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 {
  unsubscribeStream?.();
  unsubscribeStream = null;
}

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();
}

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);
  }

  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;
}

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();
  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,
    });
  } 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();
}

// Refresh the lobby badge when the app returns to the foreground — a push 'notify'
// may have been missed while the client was hidden/closed (poll + push, see §10).
if (typeof document !== 'undefined') {
  document.addEventListener('visibilitychange', () => {
    if (document.visibilityState === 'visible' && app.session) void refreshNotifications();
  });
}