import { useEffect, useState } from "react";
import { QueryClientProvider } from "@tanstack/react-query";
import { RouterProvider } from "@tanstack/react-router";
import { fetchMe, type SessionUser } from "./api.js";
import { Login } from "./Login.js";
import { ConnectScreen } from "./ConnectScreen.js";
import { queryClient } from "./lib/query.js";
import { setLanguage } from "./lib/i18n/index.js";
import { applyTheme, applyFontScale } from "./lib/theme.js";
import { router } from "./router.js";
import { initApiBase, inTauri } from "./lib/origin.js";

// App root: bootstraps the session (cookie-based, from /api/auth/me), then hands
// off to TanStack Router inside the QueryClient provider. The router renders the
// terminal chrome + screens; auth gating stays here (Login until signed in), and
// the signed-in user flows into the router context for role-based route guards.
// See wiki/entities/react-vite-spa.md and local-jwt-auth.md.
//
// Desktop shell only: BEFORE any of that, the backend origin itself must be
// known — the same installer is used at every booth (see lib/origin.ts /
// backend-config.ts), so on first launch (or after the operator clears it)
// there is no server to call fetchMe() against yet. ConnectScreen gates that;
// a browser build always has a same-origin backend, so `needsConnect` is
// always false there and this is skipped entirely.

export function App() {
  const [user, setUser] = useState<SessionUser | null>(null);
  const [loading, setLoading] = useState(true);
  const [needsConnect, setNeedsConnect] = useState(false);

  useEffect(() => {
    initApiBase().then((saved) => {
      if (inTauri() && !saved) {
        setNeedsConnect(true);
        setLoading(false);
        return;
      }
      fetchMe()
        .then(setUser)
        .finally(() => setLoading(false));
    });
  }, []);

  // Route-context consumers (RootLayout's nav, route beforeLoad guards) only re-read
  // the router context on navigation — NOT when this `user` state changes. So after
  // any session refresh (login, profile edit, a venue-module flip in Setup → Site)
  // re-validate the current matches once React has committed the new context.
  useEffect(() => {
    if (user) void router.invalidate();
  }, [user]);

  // Apply the signed-in user's preferred language + theme + font scale whenever they
  // resolve/change (login, bootstrap, or a toggle). Albanian + dark + 100% are the defaults
  // before auth resolves; on logout, fall back so the Login screen is consistent.
  useEffect(() => {
    if (user) {
      setLanguage(user.language);
      applyTheme(user.theme);
      applyFontScale(user.fontScale);
    } else {
      applyTheme("dark");
      applyFontScale(100);
    }
  }, [user]);

  if (loading) {
    return <div className="flex h-screen items-center justify-center text-term-muted">loading…</div>;
  }
  if (needsConnect) {
    return (
      <ConnectScreen
        onConnected={() => {
          setNeedsConnect(false);
          setLoading(true);
          fetchMe()
            .then(setUser)
            .finally(() => setLoading(false));
        }}
      />
    );
  }
  if (!user) {
    return (
      <QueryClientProvider client={queryClient}>
        <Login onLoggedIn={setUser} />
      </QueryClientProvider>
    );
  }

  return (
    <QueryClientProvider client={queryClient}>
      <RouterProvider router={router} context={{ user, setUser }} />
    </QueryClientProvider>
  );
}