order-service.js

const util = require('util');
const axios = require('axios');
const mailer = require('../libraries/mailer');
const axiosRetry = require('axios-retry');
const OrderRepository = require('../data-access/order-repository');
const { AppError } = require('../error-handling');
const MessageQueueClient = require('../libraries/message-queue-client');

const axiosHTTPClient = axios.create();
axiosRetry(axiosHTTPClient, { retries: 3 });

module.exports.addOrder = async function (newOrder) {
  // validation
  if (!newOrder.productId) {
    throw new AppError('invalid-order', `No product-id specified`, 400);
  }

  // verify user existence by calling external Microservice
  const userWhoOrdered = await getUserFromUsersService(newOrder.userId);

  if (!userWhoOrdered) {
    throw new AppError(
      'user-doesnt-exist',
      `The user ${newOrder.userId} doesnt exist`,
      404
    );
  }

  // save to DB (Caution: simplistic code without layers and validation)
  const DBResponse = await new OrderRepository().addOrder(newOrder);

  if (process.env.SEND_MAILS === 'true') {
    await mailer.send(
      'New order was placed',
      `user ${DBResponse.userId} ordered ${DBResponse.productId}`,
      'admin@app.com'
    );
  }

  // We should notify others that a new order was added - Let's put a message in a queue
  await new MessageQueueClient().publish(
    'order.events',
    'order.events.new',
    newOrder
  );

  return DBResponse;
};

module.exports.deleteOrder = async function (id) {
  return await new OrderRepository().deleteOrder(id);
};

module.exports.getOrder = async function (id) {
  return await new OrderRepository().getOrderById(id);
};

async function getUserFromUsersService(userId) {
  try {
    const getUserResponse = await axiosHTTPClient.get(
      `http://localhost/user/${userId}`,
      {
        timeout: 2000,
        validateStatus: (status) => {
          return status < 500;
        },
      }
    );
    return getUserResponse.data;
  } catch (error) {
    if (error?.code === 'ECONNABORTED') {
      throw new AppError(
        'user-verification-failed',
        `Request to user service failed so user cant be verified`,
        503
      );
    }

    throw error;
  }
}