Building CLI tool for trpc for type generation

import { fetchRequestHandler } from "@trpc/server/adapters/fetch";
import { type NextRequest } from "next/server";

import { env } from "@/env";
import { appRouter } from "@/server/api/root";
import { createTRPCContext } from "@/server/api/trpc";

const corsHeaders = {
  "Access-Control-Allow-Origin": "http://localhost:3001",
  "Access-Control-Request-Method": "*",
  "Access-Control-Allow-Methods": "OPTIONS, GET, POST",
  "Access-Control-Allow-Headers": "*",
  "Access-Control-Allow-Credentials": "true",
};

const createContext = async (req: NextRequest) => {
  return createTRPCContext({
    headers: req.headers,
  });
};

const handler = async (req: NextRequest) => {
  const response = await fetchRequestHandler({
    endpoint: "/api/trpc",
    req,
    router: appRouter,
    createContext: () => createContext(req),
    onError:
      env.NODE_ENV === "development"
        ? ({ path, error }) => {
            console.error(
              `❌ tRPC failed on ${path ?? "<no-path>"}: ${error.message}`,
            );
          }
        : undefined,
  });

  // Create a new response with CORS headers
  const newResponse = new Response(response.body, response);
  newResponse.headers.set("Content-Type", "application/json");

  Object.entries(corsHeaders).forEach(([key, value]) => {
    newResponse.headers.set(key, value);
  });

  return newResponse;
};

export { handler as GET, handler as POST, handler as OPTIONS };