import React, { Suspense, lazy } from 'react';
import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
import { AuthProvider } from './context/AuthContext';
import { useAuth } from './context/useAuth';
import { ErrorBoundary } from './components/ErrorBoundary';
import { LoginPage } from './pages/LoginPage';

/*
 * Every page except the login screen is loaded on demand.
 *
 * Imported eagerly, the whole app landed in one ~790kB bundle, and every
 * visitor downloaded all of it before they could reach the login form.
 * Splitting per route means each page's code arrives when it is first opened.
 * (The charting library that dominated that bundle went away with the
 * analytics pages, but the split is still worth keeping.)
 *
 * LoginPage stays eager: it is the first thing an unauthenticated visitor
 * sees, so deferring it would only add a round trip before the form appears.
 */
const HomePage = lazy(() => import('./pages/HomePage').then((m) => ({ default: m.HomePage })));
const AdminPage = lazy(() => import('./pages/AdminPage').then((m) => ({ default: m.AdminPage })));

function PageFallback({ label }) {
  return (
    <div className="min-h-screen w-full bg-slate-950 text-slate-400 flex items-center justify-center text-sm">
      {label}
    </div>
  );
}

function ProtectedRoute({ children, allowedRoles }) {
  const { user, role, restoring } = useAuth();

  // A token restored from sessionStorage is still being checked against
  // /api/auth/me. Redirecting to /login now would bounce a valid session out
  // on every refresh; rendering now would flash a dashboard about to be torn
  // down if the token turns out to be expired.
  if (restoring) {
    return <PageFallback label="Restoring session..." />;
  }

  if (!user) {
    return <Navigate to="/login" replace />;
  }

  const effectiveRole = role || (user.role === 'store' ? 'user' : user.role);

  if (allowedRoles && !allowedRoles.includes(effectiveRole)) {
    // Every remaining route is admin-only, so there is nowhere else in the app
    // to send a non-admin. This can still be reached by a token minted before
    // the `user` account was disabled - those stay valid for their 12h TTL -
    // so it has to terminate somewhere public rather than redirect in a loop.
    return <Navigate to="/login" replace />;
  }

  return children;
}

export default function App() {
  return (
    <ErrorBoundary>
      <AuthProvider>
        <BrowserRouter>
          {/* Covers the network fetch for a lazily-loaded page chunk. */}
          <Suspense fallback={<PageFallback label="Loading..." />}>
            <Routes>
            {/* Public Login Route */}
            <Route path="/login" element={<LoginPage />} />

            {/* Catalog Route - RESTRICTED TO ADMIN ONLY */}
            <Route
              path="/"
              element={
                <ProtectedRoute allowedRoles={['admin']}>
                  <HomePage />
                </ProtectedRoute>
              }
            />

            {/* Admin Panel Route - RESTRICTED TO ADMIN ONLY */}
            <Route
              path="/admin"
              element={
                <ProtectedRoute allowedRoles={['admin']}>
                  <AdminPage />
                </ProtectedRoute>
              }
            />

            {/* Catch-all redirect */}
            <Route path="*" element={<Navigate to="/" replace />} />
            </Routes>
          </Suspense>
        </BrowserRouter>
      </AuthProvider>
    </ErrorBoundary>
  );
}