import { getContainer } from "@cloudflare/containers";
import type { HandleFetch } from "@sveltejs/kit";

function isBackendPath(pathname: string): boolean {
  return (
    pathname === "/api" ||
    pathname.startsWith("/api/") ||
    pathname === "/metrics" ||
    pathname === "/ready" ||
    pathname.startsWith("/xrpc/")
  );
}

// Browser /api hits the Worker fetch handler, which forwards to the container.
// SvelteKit server loads fetch("/api/...") inside this isolate, so send those
// to the same named container. The event.fetch request carries no cookies,
// so the browser's cookie header is forwarded explicitly: without it the
// container answers as anonymous and logged-in users bounce to /auth/login.
export const handleFetch: HandleFetch = async ({ event, request, fetch }) => {
  const url = new URL(request.url);
  if (url.origin !== event.url.origin || !isBackendPath(url.pathname)) {
    return fetch(request);
  }

  const glean = event.platform?.env?.GLEAN;
  if (!glean) {
    throw new Error("GLEAN container binding missing");
  }

  const headers = new Headers(request.headers);
  const cookie = event.request.headers.get("cookie");
  if (cookie && !headers.has("cookie")) {
    headers.set("cookie", cookie);
  }

  return getContainer(glean, "glean").fetch(new Request(request, { headers }));
};