core/apps/webapp/app/routes/ph-relay-core20.$.tsx

import type { ActionFunction, LoaderFunction } from "@remix-run/node";

const API_HOST = "us.i.posthog.com";
const ASSET_HOST = "us-assets.i.posthog.com";

const posthogProxy = async (request: Request) => {
  const url = new URL(request.url);
  const hostname = url.pathname.startsWith("/ph-relay-core20/static/")
    ? ASSET_HOST
    : API_HOST;

  const newUrl = new URL(url);
  newUrl.protocol = "https";
  newUrl.hostname = hostname;
  newUrl.port = "443";
  newUrl.pathname = newUrl.pathname.replace(/^\/ph-relay-core20/, "");

  const headers = new Headers(request.headers);
  headers.set("host", hostname);

  const response = await fetch(newUrl, {
    duplex: "half",
    method: request.method,
    headers,
    body: request.body,
  });

  return new Response(response.body, {
    status: response.status,
    statusText: response.statusText,
    headers: response.headers,
  });
};

export const loader: LoaderFunction = async ({ request }) =>
  posthogProxy(request);

export const action: ActionFunction = async ({ request }) =>
  posthogProxy(request);