Phone Corp Module

💬   About

This is an exercise from a company interview process for Junior full-stack developers apply.
The goal of this exercise is to create a backend module for a phone company
to list products and create orders from them.

⚙️   Tech Stack

     

🔩   Main features

• Retrieve the list of products present in the database.
• Retrieve a specific product.
• Place an order of products.
• Display the list of orders.
• Handle non-passing cases: what to do if the requested product does not exist ? What if the order contains products not present in the database ?
• Qualitatives tests and documentation should be written.

？How to run it

1. npm install to install depencies.
2. npm start to run the PhoneCorp system. The server will listen port :4000.
3. npm run test to run tests.
4. You can create a .env file and place MONGODB_URL= followed by your connection string provided by MongoDB to interact with your database.

📁 Architecture

• I decided to create this project trying to build some layers to be able to have a clean and maintenable code.
  
• I found services --> utils --> controllers --> routes a good path to design the project pattern.
• Created a config folder to store mongoose connection module exports and env with PORT config.
• Decided to create my services and utils folders into database because it interacts directly with it.
• Defined my tests in two differents folders functions and routes, both contains order and product.

🚏 Routes

Routes	Methods	Function
/product/create	POST	Create a product
/product/stock	GET	List all existing products sorted by brand
/product/:id	GET	Retrieve a product with :id
/product/	GET	Handle error if :id not provided
/order/create	POST	Pass an order
/order/history	GET	List all orders sorted by date

？ How to use

• For /product/stock, product/ and order/history routes, you just have to send a GET request.
  

• /product/create :

//example body to send to create a product

{
    "brand": "iPhone", // string
    "model": "15 Pro Max", // string
    "sku": 123456, // number
    "price": 1599, // number
    "quantity": 3 // number
}

• /product/:id :

http://localhost:4008/product/ folloed by existing database ID

• /order/create :

//example body to send to create an order

// replace examples Id by existing database ID, anyway if you provide a wrong ID the response will alert you.

{
    "order": [
        {
            "productId": "64bed8f2687ae0df0d3675fd",
            "quantity": 2
        },
           {
            "productId": "64bed8f2687ae0df0d3675fd", "quantity": 2
        },
           {
            "productId": "64bf01c275bc8f6ff962ae34", "quantity": 2
        }
    ]
}

🧱 Process

• Sent all my request with Postman when working on the project and set up all my environment to be comfortable.
  

❌ Errors handling

• When I created my routes i decided to handle some errors handlers :

-product/create => 400(at least 1 product information not provided / quantity ordered is < 1)
                   409(SKU already exists)
                   500(errors)

product/stock   => 500(errors)

product/:id     => 404(ID not found in DB)
                   500(error)

product/        => 400(product/:id not provided)

order/create    => 400(0 product placed on order / negative product quantity ordered)
                   500(errors)
                   alert(Object.JSON response: ID doesnt exists and cannot be placed in order)

order/history   => 500(errors)

🧪 Tests

• I decided to use Jest, SuperTest and mongodb-memory-server to deal with testing.
• This setup is pretty efficient and not that hard to use.
• I defined 33 tests which covers all the functions / API calls and DB interactions that i found relevant to test.
• As explained you can run all tests by running npm run test or you can do this separately with the commands i created in package.json :

 npm run test:getOrder
 npm run test:createOrder
 npm run test:createProduct
 npm run test:getProductStock
 npm run test:getProductById
 npm run test:productFunc
 npm run test:orderFunc

💪🏼 Possible improvements

• Create independents functions to handle errors in API calls.
• Upgrading the module with product/delete and product/update/:id paths.
• Create an assets folder containing a json file to store all the reusable string messages.
• Edit the project config to be able to import with @/whatever instead of ../../../whatever.
• Move all the functions contained in getOrder.ts to keep code cleaner and more maintenable.
• Refactoring some parts of my code to be clearer and more modular.
• Use a Schema Validator like Zod to avoid some possibles issues if the app growth.
• Add an Auth, Login, Register and Roles.
• Add a customer ID to track who passed orders.
• Frontend interface.

🙇🏻 What did i learn, improve and discover

• I Improved my TypeScript's knowledges.
• I improved my vision of project architecture.
• I learned how to run tests properly and to test what seemed relevant to me.
• I learned how to write and structure a well documented README file.
• I discovered mongodb-memory-server which is pretty good for testing interaction with database.

💥 Annoying encountered issues and how i solved them

Jest / TypeScript compatibility

• Had troubles with Jest and TypeScript compatibility, my tests crashed everytime.
  
  
• After some investigations i discovered that i needed to install :
  
  babel/core
babel/preset-env
babel/preset-typescript
  
  
• Create a babel.config.js file and put this inside :

module.exports = {
  presets: [
    ["@babel/preset-env", { targets: { node: "current" } }],
    "@babel/preset-typescript",
  ],
};

• Also create a jest.config.ts and put this inside :

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  testEnvironment: "node",
  preset: "ts-jest --config=jest.config.ts",
  transformIgnorePatterns: ["/node_modules/(?!(uuid)/)"],
};

🔊 Address already in use when testing

• Had troubles running npm run test because tests failed with this error message :

listen EADDRINUSE: address already in use :::4008

• After some investigations i discovered that i needed to mention (require.main === module) && condition in my index.ts :

require.main === module &&
  server.listen(config.port, () => {
    console.log(
      `⚡️[server]: Server started 🚀 running at http://localhost:${config.port}`
    );
  });

• With this condition the server won't force listening on port 4008 between each tests.

🛒 create/order issues

• Encountered some issues with order/create API Response when an order was passed.
• I created a new branch, reworked my schemas and made it works properly.
• Merged it when properly fixed.
• Also had trouble trying to export functions outside of getOrder.ts, had a lot of TypeScript errors
  and bugs and i lost too much time trying to clean this.
  
• It works well like that but it's kind of dirty part of my code, i should rework this later on !

🔭 Conclusion

• Working on this project was really exciting !
• I tried my best but can do way better if i restart from scratch a second time.
  
• But I had to make choices because i lost a lot of times trying to refactor and deal with errors.
• I started by establishing a little sketch on Excalidraw and took some notes to define the logic, structure and path i wanted to create.
• I improved my skills working on this project and i consider this as a really good point for me.
• A little bit frustrated to had no time to create a little frontend interface to have something to show.