@apolitical/server/src/middlewares/error.middleware.js

Node.js module to encapsulate Apolitical's express server setup

'use strict';

module.exports =
  ({
    httpStatusCodes: { FORBIDDEN, INTERNAL_SERVER_ERROR, TEMPORARY_REDIRECT },
    config: {
      JWT: { AUTH0 },
    },
    logger,
    loggerHelper: { getUserId },
    serverError: { GeneralError },
  }) =>
  ({ labels, redirectURL, fallbackController }) => {
    // eslint-disable-next-line no-unused-vars
    return function handler(err, req, res, next) {
      // Initialise variables
      let code = INTERNAL_SERVER_ERROR;
      let message = 'Unexpected error';
      let errors = [];
      // Parse errors
      if (err instanceof GeneralError) {
        code = err.code;
        message = err.message;
        errors = err.errors;
      } else {
        const { name, message: errorMessage } = err;
        if (name === AUTH0.ERRORS.UNAUTHORIZED) {
          code = FORBIDDEN;
          message = `Unauthorized error: ${errorMessage}`;
          errors = ['auth0-token'];
        } else {
          code = INTERNAL_SERVER_ERROR;
          message = `Unexpected error: ${errorMessage}`;
          errors = ['unknown-error'];
        }
      }
      // Log the error with all the relevent info
      const userId = getUserId(req);
      if (req.log) {
        req.log.warn(message, { errors, userId });
      } else {
        const errorLogger = logger.where(__filename, 'handler', labels);
        errorLogger.warn(message, { errors, userId });
      }
      // Use the redirect URL to redirect the request
      if (redirectURL) {
        return res.redirect(TEMPORARY_REDIRECT, `${redirectURL}?errorMessage=${encodeURI(message)}`);
      }
      // Use the fallback controller to handle the response
      if (fallbackController) {
        // more known error messages can be added here
        if (message === 'Unexpected error: Cannot read items') {
          return fallbackController(req, res);
        }
      }
      // Use the info on the error to send the response
      return res.status(code).json({ message, errors });
    };
  };