import { NavLink, Navigate, Route, Routes, useLocation, useNavigate } from "react-router-dom";
import { useTranslation } from "react-i18next";
import { useAuth } from "./auth";
import Icon from "./components/Icon";
import ErrorBoundary from "./components/ErrorBoundary";
import BrandMark from "./components/BrandMark";
import Login from "./pages/Login";
import ChangePassword from "./pages/ChangePassword";
import Dashboard from "./pages/Dashboard";
import Accounts from "./pages/Accounts";
import Categories from "./pages/Categories";
import Transactions from "./pages/Transactions";
import Budget from "./pages/Budget";
import Import from "./pages/Import";
import Offen from "./pages/Offen";
import Users from "./pages/Users";
import Settings from "./pages/Settings";
import TwoFactor from "./pages/TwoFactor";
import Account from "./pages/Account";

const navClass = ({ isActive }) => (isActive ? "nav-link active" : "nav-link");

function NavItem({ to, icon, label, end }) {
  return (
    <NavLink to={to} end={end} className={navClass}>
      <Icon name={icon} size={17} />
      <span className="label">{label}</span>
    </NavLink>
  );
}

function Sidebar() {
  const { user, isAdmin, logout } = useAuth();
  const { t } = useTranslation();
  const navigate = useNavigate();

  async function handleLogout() {
    await logout();
    navigate("/login");
  }

  return (
    <aside className="sidebar">
      <div className="sidebar-brand">
        <BrandMark />
      </div>
      <nav className="sidebar-nav">
        <NavItem to="/" end icon="dashboard" label={t("nav.overview")} />
        <NavItem to="/konten" icon="wallet" label={t("nav.accounts")} />
        <NavItem to="/kategorien" icon="list" label={t("nav.categories")} />
        <NavItem to="/buchungen" icon="arrow-left-right" label={t("nav.transactions")} />
        <NavItem to="/offen" icon="inbox" label={t("nav.open")} />
        <NavItem to="/budget" icon="pie-chart" label={t("nav.budget")} />
        <NavItem to="/import" icon="download" label={t("nav.import")} />
        <div className="nav-section">{t("nav.system")}</div>
        <NavItem to="/settings" icon="settings" label={t("nav.settings")} />
        {isAdmin && <NavItem to="/users" icon="users" label={t("nav.users")} />}
      </nav>
      <div className="sidebar-foot">
        <NavLink to="/konto" className="sidebar-user" title={t("account.title")}>
          <span className="name">{user?.display_name || user?.username}</span>
          <span className="role">{isAdmin ? t("common.admin") : t("common.user")}</span>
        </NavLink>
        <button className="btn-icon" onClick={handleLogout} title={t("common.logout")}>
          <Icon name="logout" size={18} />
        </button>
      </div>
    </aside>
  );
}

/** Server nicht erreichbar – die Anmeldung bleibt bestehen, nur der Abruf nicht. */
function StartFehler({ text, erneut }) {
  const { t } = useTranslation();
  return (
    <div className="center" style={{ padding: 60 }}>
      <div className="alert error" style={{ maxWidth: 520 }}>
        <Icon name="alert" size={16} />
        <div>
          <div>{text}</div>
          <div className="muted small" style={{ marginTop: 4 }}>
            {t("server.sessionKept")}
          </div>
        </div>
      </div>
      <button className="btn primary" style={{ marginTop: 16 }} onClick={erneut}>
        {t("common.retry")}
      </button>
    </div>
  );
}

function Protected({ children, adminOnly = false, wide = false }) {
  const { user, isAdmin, loading, startFehler, erneutVersuchen } = useAuth();
  const { pathname } = useLocation();
  const { t } = useTranslation();

  if (loading) return <div className="center muted" style={{ padding: 60 }}>{t("common.loading")}</div>;
  if (startFehler) return <StartFehler text={startFehler} erneut={erneutVersuchen} />;
  if (!user) return <Navigate to="/login" replace />;
  // Offene Pflichten der Reihe nach – dieselbe Reihenfolge erzwingt der Server
  // (backend/app/deps.py, enforce_account_state), sonst liefe man in 403er.
  if (user.must_change_password && pathname !== "/passwort-aendern") {
    return <Navigate to="/passwort-aendern" replace />;
  }
  if (user.mfa_setup_required && pathname !== "/zwei-faktor") {
    return <Navigate to="/zwei-faktor" replace />;
  }
  if (adminOnly && !isAdmin) return <Navigate to="/" replace />;

  return (
    <div className="app-shell">
      <Sidebar />
      <div className="main">
        <div className={wide ? "content content--wide" : "content"}>
          <ErrorBoundary key={pathname} bereich="Diese Seite">
            {children}
          </ErrorBoundary>
        </div>
      </div>
    </div>
  );
}

export default function App() {
  const { user, loading } = useAuth();

  return (
    <Routes>
      <Route
        path="/login"
        element={loading ? null : user ? <Navigate to="/" replace /> : <Login />}
      />
      <Route path="/passwort-aendern" element={<ChangePassword />} />
      <Route path="/" element={<Protected wide><Dashboard /></Protected>} />
      <Route path="/konten" element={<Protected><Accounts /></Protected>} />
      <Route path="/kategorien" element={<Protected><Categories /></Protected>} />
      <Route path="/buchungen" element={<Protected wide><Transactions /></Protected>} />
      <Route path="/offen" element={<Protected><Offen /></Protected>} />
      <Route path="/budget" element={<Protected wide><Budget /></Protected>} />
      <Route path="/import" element={<Protected wide><Import /></Protected>} />
      <Route path="/settings" element={<Protected><Settings /></Protected>} />
      <Route path="/konto" element={<Protected><Account /></Protected>} />
      <Route path="/zwei-faktor" element={<Protected><TwoFactor /></Protected>} />
      <Route path="/users" element={<Protected adminOnly><Users /></Protected>} />
      <Route path="*" element={<Navigate to="/" replace />} />
    </Routes>
  );
}