express-gateway/lib/policies/request-transformer/index.js

A microservices API gateway built on top of ExpressJS

const jsonParser = require('express').json();
const urlEncoded = require('express').urlencoded({ extended: true });
const { PassThrough } = require('stream');
const transformObject = require('./transform-object');
const formurlencoded = require('form-urlencoded').default;

module.exports = {
  schema: require('./schema'),
  policy: params => {
    return (req, res, next) => {
      let contentType = 'application/x-www-form-urlencoded';

      if (params.headers) {
        transformObject(params.headers, req.egContext, req.headers);
      }

      if (params.body) {
        jsonParser(req, res, (err) => {
          if (err) return next(err);
          if (Object.keys(req.body).length !== 0) contentType = 'application/json';

          urlEncoded(req, res, (err) => {
            if (err) return next(err);
            if (Object.keys(req.body).length === 0) contentType = 'application/json';

            const serializeFn = contentType === 'application/json' ? JSON.stringify : formurlencoded;

            const bodyData = serializeFn(transformObject(params.body, req.egContext, req.body));

            req.headers['content-length'] = Buffer.byteLength(bodyData);
            req.headers['content-type'] = contentType;

            req.egContext.requestStream = new PassThrough();
            req.egContext.requestStream.write(bodyData);

            next();
          });
        });
      } else {
        next();
      }
    };
  }
};