@bbc/http-transport/lib/middleware/asJson.js

A flexible, modular REST client built for ease-of-use and resilience.

'use strict';

const jsonRegex = /^application\/([a-z0-9-+]+)?json/;

function isJsonContentType(contentType) {
  return jsonRegex.test(contentType);
}

function isValidBody(body) {
  const notParsed = typeof body !== 'object';
  const validBody = (typeof body !== 'undefined' && body !== null && body !== '');
  return notParsed && validBody;
}

module.exports = (opts) => {
  opts = opts || {};
  const throwOnConflict = opts.throwOnConflict;
  const force = opts.force;

  return async (ctx, next) => {
    await next();

    const contentType = ctx.res.headers['content-type'];
    const body = ctx.res.body;
    const isJson = isJsonContentType(contentType);
    const shouldParse = force || isJson;

    if (shouldParse && isValidBody(body)) {
      try {
        ctx.res.body = JSON.parse(ctx.res.body);
      } catch (err) {
        throw new Error(`JSON parsing failure: ${err.message}`);
      }
    }

    if (!isJson && throwOnConflict) throw new Error(`expected a json content type got ${contentType}`);
  };
};