/**
 * Login — two doors, one identity rule (never both at once):
 *
 * - "Continue as guest": one click, no account. A per-browser secret is
 *   minted locally; the agent remembers this browser across visits.
 * - "Sign in": the BYO-OIDC seam. Rendered only when `auth.oidc` is
 *   configured in guuey.app.json (or via `scripts/bootstrap.mjs`) — any
 *   spec-compliant IdP; this is where a "Sign in with Google" plugs in. The
 *   bound guuey app must be in BYO auth mode for the same issuer. Until it
 *   is configured the page shows the guest door alone: a disabled
 *   "not configured yet" control is a developer note, not a customer door
 *   (guuey#930).
 */
import { useEffect, useRef, useState } from "react";
import { useNavigate } from "react-router-dom";
import { appConfig } from "../config";
import { CHAT_PATH } from "../routes";
import { continueAsGuest, setIdentityMode } from "../lib/identity";
import { completeSignIn, isSigninCallback, oidcConfigured, signIn, signOutOidc } from "../lib/oidc";

export function Login() {
  const navigate = useNavigate();
  const [error, setError] = useState<string | null>(null);
  const [completing, setCompleting] = useState(isSigninCallback());
  // One-shot: StrictMode double-invokes effects in dev, and the OIDC
  // authorization code is single-use — a second signinCallback() would
  // double-spend it and flash a bogus failure.
  const callbackStarted = useRef(false);

  // Finish the redirect flow when the IdP sent us back here.
  useEffect(() => {
    if (!isSigninCallback() || callbackStarted.current) return;
    callbackStarted.current = true;
    completeSignIn()
      .then(() => {
        setIdentityMode("oidc");
        navigate(CHAT_PATH, { replace: true });
      })
      .catch((err: unknown) => {
        setCompleting(false);
        setError(err instanceof Error ? err.message : String(err));
      });
  }, [navigate]);

  function guest() {
    // One identity mode per surface: an explicit guest choice also drops
    // any cached OIDC session, so a stale bearer can never shadow it.
    void signOutOidc();
    continueAsGuest();
    navigate(CHAT_PATH);
  }

  if (completing) {
    return (
      <main className="page login">
        <div className="login-card">
          <p>Completing sign-in…</p>
        </div>
      </main>
    );
  }

  return (
    <main className="page login">
      <div className="login-card">
        <h1>Welcome to {appConfig.brand.name}</h1>
        {oidcConfigured() ? (
          <button type="button" className="btn btn-accent btn-wide" onClick={() => void signIn()}>
            Sign in
          </button>
        ) : null}
        <button type="button" className="btn btn-wide" onClick={guest}>
          Continue as guest
        </button>
        <p className="hint">{appConfig.copy.login.guestHint}</p>
        {error ? <p className="error">Sign-in failed: {error}</p> : null}
      </div>
    </main>
  );
}