import { createProxyMiddleware } from "http-proxy-middleware";
import type { RequestHandler } from "express";

const CLERK_FAPI = "https://frontend-api.clerk.dev";
export const CLERK_PROXY_PATH = "/api/__clerk";

export function clerkProxyMiddleware(): RequestHandler {
  if (process.env.NODE_ENV !== "production") {
    return (_req, _res, next) => next();
  }
  const secretKey = process.env.CLERK_SECRET_KEY;
  if (!secretKey) {
    return (_req, _res, next) => next();
  }
  return createProxyMiddleware({
    target: CLERK_FAPI,
    changeOrigin: true,
    pathRewrite: (path) => path.replace(new RegExp("^" + CLERK_PROXY_PATH), ""),
    on: {
      proxyReq: (proxyReq, req) => {
        const protocol = req.headers["x-forwarded-proto"] || "https";
        const host = req.headers.host || "";
        proxyReq.setHeader("Clerk-Proxy-Url", protocol + "://" + host + CLERK_PROXY_PATH);
        proxyReq.setHeader("Clerk-Secret-Key", secretKey);
        const xff = req.headers["x-forwarded-for"];
        const clientIp = (Array.isArray(xff) ? xff[0] : xff)?.split(",")[0]?.trim() || req.socket?.remoteAddress || "";
        if (clientIp) proxyReq.setHeader("X-Forwarded-For", clientIp);
      },
    },
  }) as RequestHandler;
}