NextJS API Util

handler.ts

import { NextApiRequest, NextApiResponse } from "next";
import { StatusCodes, getReasonPhrase } from "http-status-codes";

type NextHandler<R> = (req: NextApiRequest, res: NextApiResponse<R>) => void;

type ResponseEnhanced<R> = {
  status?: StatusCodes | number;
  headers?: Record<string, string>;
  body?: R;
};

export type TypedNextApiRequest<Q> = Omit<NextApiRequest, "query"> & {
  query: Q;
};

type HandlerParam<R, Q> = (
  req: TypedNextApiRequest<Q>
) => Promise<ResponseEnhanced<R>>;

type Method = "post" | "get" | "delete" | "patch" | "put";

function makeHandler(method?: Method) {
  return <Q, R>(inner: HandlerParam<R, Q>): NextHandler<R> => {
    return (req: NextApiRequest, res: NextApiResponse) => {
      if (method && req.method?.toLowerCase() !== method) {
        return res.status(StatusCodes.METHOD_NOT_ALLOWED).send({
          error: getReasonPhrase(StatusCodes.METHOD_NOT_ALLOWED),
        });
      }

      return inner(req as NextApiRequest & { query: Q })
        .then((_res) => {
          const status = _res.status || StatusCodes.OK;
          const headers = _res.headers || {};

          Object.keys(headers).forEach((key) =>
            res.setHeader(key, headers[key])
          );

          res.status(status).send(_res.body || "");
        })
        .catch((err) => {
          console.log(`Uncaught error: ${err}`);

          res.status(StatusCodes.INTERNAL_SERVER_ERROR).json({
            error: getReasonPhrase(StatusCodes.INTERNAL_SERVER_ERROR),
          });
        });
    };
  };
}

const _defaultHandler = makeHandler();

export function handler<Q, R>(inner: HandlerParam<R, Q>) {
  return _defaultHandler<Q, R>(inner);
}

handler.get = makeHandler("get");
handler.post = makeHandler("post");
handler.delete = makeHandler("delete");
handler.put = makeHandler("get");
handler.patch = makeHandler("get");