express-respond/lib/index.js

HTTP response methods with auto content negotiation for expressjs

'use strict';

const _ = require('lodash');
const common = require('@lykmapipo/common');
const env = require('@lykmapipo/env');

// TODO: just extend response directly

/**
 * @function prepareBody
 * @name prepareBody
 * @description prepare response body
 * @param {*} [data] valid response body
 * @param {string} [code=500] valid http response status code
 * @returns {object} formatted response body
 * @author lally elias <lallyelias87@mail.com>
 * @since  1.1.0
 * @version 0.1.0
 * @license MIT
 * @private
 * @example
 * const body = prepareBody(new Error('Missing API Key'));
 * //=> { message: 'Missing API Key', ... }
 *
 * const body = prepareBody({ name: 'lykmapipo' });
 * //=> { name: 'lykmapipo' }
 */
const prepareBody = (data, code = 500) => {
  // build response base on http status code
  if (!data) {
    const status = code;
    const message = common.STATUS_CODES[code];
    const description = common.STATUS_CODES[code];
    return { status, code, message, description };
  }

  // handle error or data
  const stack = !env.isProduction();
  let body = {};
  body = _.isError(data) ? common.mapErrorToObject(data, { code, stack }) : data;

  // return formatted response body
  return body;
};

/**
 * @function mapToHttpReply
 * @name mapToHttpReply
 * @description generate http reply method based on http status
 * @param {object} response valid express http response object
 * @param {string} code valid http response status code
 * @returns {Function} a valid response function helper
 * @author lally elias <lallyelias87@mail.com>
 * @since  1.2.0
 * @version 0.1.0
 * @license MIT
 * @private
 */
const mapToHttpReply = (response, code) => (data) => {
  // prepare http status
  let status = _.get(data, 'status', code);

  // FIX: RangeError [ERR_HTTP_INVALID_STATUS_CODE]: Invalid status code
  // FIX: if response data has status field for business logics
  status = _.isNumber(status) || _.isString(status) ? status : code;

  // set response status
  response.status(status);

  // respond with json body
  const ignoreBody = _.includes([204, 304], _.toNumber(status));
  if (ignoreBody) {
    return response.json();
  }

  // prepare response body
  const body = prepareBody(data, status);
  return response.json(body);
};

/**
 * @function mapStatusToMethod
 * @name mapStatusToMethod
 * @description map http status to named response method
 * @param {object} response valid express http response object
 * @returns {Function} a valid response function helper
 * @author lally elias <lallyelias87@mail.com>
 * @since  1.2.0
 * @version 0.1.0
 * @license MIT
 * @private
 */
const mapStatusToMethod = (response) => (status, code) => {
  // prepare response method from http status message
  const method = _.camelCase(status);

  // extend http response with the custom response type method
  const httpReply = mapToHttpReply(response, code);
  response[code] = httpReply;
  response[method] = httpReply;
};

/**
 * @function respond
 * @name respond
 * @description common http responses for expressjs
 * @param {object} request valid express http request object
 * @param {object} response valid express http response object
 * @param {Function} next a middleware to invoke for continuation
 * @returns {Function} a valid expressjs middleware
 * @author lally elias <lallyelias87@mail.com>
 * @since  1.0.0
 * @version 0.1.0
 * @license MIT
 * @public
 * @example
 * const express = require('express');
 * const respond = require('express-respond');
 *
 * const app = express();
 * app.use(respond);
 *
 * app.get('/', (request, response) => {
 *   response.ok({ name: 'lykmapipo' });
 * });
 */
const respond = (request, response, next) => {
  // map http status code to http response method
  _.forEach(common.STATUS_CODES, mapStatusToMethod(response));

  // add error response method
  response.error = mapToHttpReply(response, 500);

  // continue with middleware chain
  return next();
};

module.exports = respond;