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Mobile Acebook Backend

This repository contains a backend application using the MERN stack. The frontend code is also included but is not fully functional due to recent backend changes.

⚠️ The frontend code is included for reference only and is not required for this week's project. You'll be focusing on integrating your Mobile App with the existing backend within this repository.

The application is the same you just worked on during your recent Engineering Project, so it should be extremely familiar.

ℹ️ Do not worry if you used a different tech stack for your Acebook project (e.g. Ruby on Rails), as the project is designed to be backend-agnostic really. Keep reading and this will make more sense soon!

Existing Features

This is a complete Acebook project, but you will only integrate your Mobile App against a subset of the features already available.

Feel free to explore more features if you have extra time!

ℹ️ However, please note that you do not own the backend as it's managed by another team.

Any requests for additional endpoints or changes will be analyzed by this team and taken into consideration. However you can make your requests (via your coach!).

API Endpoints Overview

Here's a quick overview of the API endpoints you'll be interacting with:

Endpoint Method Payload Model Description Response Values
http://127.0.0.1:8080/users POST User Sign up a new user 201 OK: { message: 'OK' }
http://127.0.0.1:8080/tokens POST email, password Log in an existing user 201 OK: { token: String, message: 'OK' }
http://127.0.0.1:8080/posts POST NewPost Create a new post 201 OK: { message: 'OK', token: String }
http://127.0.0.1:8080/posts GET N/A Fetch all posts 200 OK: { posts: [Post], user: User, token: String }

Remember to include the token in the request headers for authenticated routes.

Postman collections

We have created a Postman collection with all the relevant requests in it for the week, in case you need to test your backend in isolation to get clarity about payloads, etc.

This collection should help you make sense of what the Models in the table above mean :)

Consider this a hint for your SwiftUI mobile app!

You can find it here.

And to import it in Postman, simply click on "File" -> "Import" and select the above file, a new collection should be created and you're ready to go!



We have also included all the relevant instructions that were part of the original template for the MERN Acebook project just below as well for reference in case you need them.

Videos

Technologies

M is for MongoDB

MongoDB is a NoSQL database program that stores data in collections of documents (in a format similar to JSON), rather than in tables. The application interacts with MongoDB using a tool called Mongoose.

E is for Express

Express is the Javascript equivalent of Sinatra. The structure of this application will feel quite different to what you're used to but the principles are the same.

R is for React

N is for Node

Javascript was originally designed to run exclusively in browsers, such as Chrome. Node is a tool that allows you to run Javascript outside the browser and its invention made it possible to build full stack Javascript apps.

Architecture

This application is comprised of two distinct pieces.

  • A backend API built with Express
  • A frontend built with React (for reference only)

Authentication

Here's the authentication flow for this application

  1. A registered user submits their email address and password from the frontend (our Mobile App in this case).
  2. The backend receives the data and tries to find a user in the DB with the same email address.
  3. If a user is found, the password in the database is compared to the password that was submitted.
  4. If the passwords match, a JSON Web Token is generated and returned, as part of the response.
  5. The frontend receives the token and holds on to it.
  6. Every request to the backend that requires authentication must include a valid token (which is checked by the backend).
  7. When the user logs out, the front end discards the token.

authentication flow diagram

What is a JSON Web Token?

A JSON Web Token, or JWT, is a token that comprises three parts

  • A header, which contains information about how the token was generated.
  • A signature, which is used to verify the token.
  • A payload, which you can use to store some non-sensitive data like a user id. Note that the payload is not secure and can be decoded very easily.

The signature is created using a 'secret', which must be kept private (i.e. not put on GitHub) otherwise nefarious internet users could start to issue tokens for your application.

Here, we've used an environment variable called JWT_SECRET, which you'll see used in the commands to start the application and run the tests (below). You can change the value of that environment variable to anything you like.

Quickstart

Install Node.js

  1. Install Node Version Manager (NVM) 
    brew install nvm
    Then follow the instructions to update your ~/.bash_profile.
  2. Open a new terminal
  3. Install the latest version of Node.js, currently 18.1.0. 
    nvm install 18

Set up your project

⚠️ Make sure that your backend server (in ./api) is running so that you can interact with it from your Mobile App.

🚨 You do not need to run the React application (in ./frontend) at all.

  1. Clone this project to your local machine. (Do not fork it, as you will not make any changes to it really.)
  2. Install Node.js dependencies for the backend (API) 
    ; cd api
; npm install
  3. Install MongoDB (if you haven't already) 
    brew tap mongodb/brew
brew install mongodb-community@5.0
    Note: If you see a message that says If you need to have mongodb-community@5.0 first in your PATH, run:, follow the instruction. Restart your terminal after this.
  4. Start MongoDB 
    brew services start mongodb-community@5.0

Start

  1. Start the server

Note the use of an environment variable for the JWT secret

; cd api
; JWT_SECRET=SUPER_SECRET npm start

MongoDB Connection Errors?

Some people occasionally experience MongoDB connection errors when running the tests or trying to use the application. Here are some tips which might help resolve such issues.

  • Check that MongoDB is installed using mongo --version
  • Check that it's running using brew services list

If you have issues that are not resolved by these tips, please reach out to a coach and, once the issue is resolved, we can add a new tip!