import { createMemoryHistory } from "@octanejs/tanstack-router";
import type { Middleware } from "@octanejs/vite-plugin";
import type { AppRouter } from "./router.ts";

export const ROUTER_STATE_KEY = "tanstack.router";

/**
 * Build and load a server router for one request. Loading runs the matched
 * routes' loaders, so the render that follows reads settled data and the
 * router can report a redirect or a 404 before any HTML is sent.
 */
export async function loadServerRouter(url: URL): Promise<AppRouter> {
  const { createAppRouter } = await import("./router.ts");
  const router = createAppRouter({
    history: createMemoryHistory({
      initialEntries: [url.pathname + url.search],
    }),
    isServer: true,
    origin: url.origin,
  });
  await router.load();
  return router;
}

/**
 * RenderRoute middleware: loads the router, hands it to <App> through request
 * state, and turns the router's outcome into the response status.
 */
export const tanstackRouter: Middleware = async (context, next) => {
  const router = await loadServerRouter(context.url);

  const redirect = router.state.redirect;
  if (redirect) {
    const href = redirect.options.href ?? redirect.headers.get("Location");
    if (href) {
      return new Response(null, {
        status: redirect.status || 307,
        headers: { Location: new URL(href, context.url).toString() },
      });
    }
  }

  context.state.set(ROUTER_STATE_KEY, router);
  const response = await next();
  const status = router.stores.statusCode.get();
  if (status === response.status || !response.ok) return response;
  return new Response(response.body, { status, headers: response.headers });
};