// App shell — loads the session, applies the entry-routing rule (SD-0001 §6.5), and renders
// the matching screen. The rule is exhaustive: no state lands nowhere (BUC-4). The verify
// response carries the same shape as /me, so onAuthed feeds the session directly.
import { useEffect, useState } from "react";
import { getMe, type StorefrontResult, type VerifyResult } from "./api";
import { routeFor, type SessionState } from "./routing";
import Admin from "./screens/Admin";
import CreateStorefront from "./screens/CreateStorefront";
import Landing from "./screens/Landing";
import SignIn from "./screens/SignIn";

type Door = "signup" | "login";
type Welcome = "new" | "back" | null;

export default function App() {
  const [session, setSession] = useState<SessionState | null>(null);
  const [loading, setLoading] = useState(true);
  const [door, setDoor] = useState<Door | null>(null);
  const [welcome, setWelcome] = useState<Welcome>(null);

  async function reload() {
    setLoading(true);
    setSession(await getMe());
    setLoading(false);
  }

  useEffect(() => {
    void reload();
  }, []);

  if (loading) {
    return (
      <div className="screen screen--plain">
        <main className="screen__main">
          <p className="note">Loading…</p>
        </main>
      </div>
    );
  }

  const route = routeFor(session ?? { account: null, storefront: null });

  if (route === "landing") {
    if (door) {
      return (
        <SignIn
          door={door}
          onBack={() => setDoor(null)}
          onAuthed={(result: VerifyResult) => {
            setWelcome(result.created ? "new" : "back");
            setDoor(null);
            setSession({ account: result.account, storefront: result.storefront });
          }}
        />
      );
    }
    return <Landing onGetStarted={() => setDoor("signup")} onLogIn={() => setDoor("login")} />;
  }

  const email = session!.account!.email;

  function signedOut() {
    setWelcome(null);
    setDoor(null);
    setSession(null);
  }

  if (route === "create-storefront") {
    return (
      <CreateStorefront
        email={email}
        welcome={welcome}
        onCreated={(sf: StorefrontResult) => {
          setWelcome(null);
          setSession({ account: { email }, storefront: sf });
        }}
        onAlreadyOwns={() => void reload()}
        onSignedOut={signedOut}
      />
    );
  }

  return (
    <Admin
      storefrontName={session!.storefront!.name}
      email={email}
      welcome={welcome}
      onSignedOut={signedOut}
    />
  );
}