firebase-backend

A package that helps with the management and expansion of a maintainable firebase backend

firebase-backend

Requirements

node >=10

Overview

Let's to start out by going through a high level overview of how the backend will be setup. This overview will go over the types of functions we use as well as the actual code structure.

Types of Functions

The backend is built around the strengths that firebase poses in their serverless cloud functions setup. Focussing on those strengths we can break the system into two types of functions (could also be called a micro-service if you choose to). Reactive and RESTul

Reactive: This is a function that will run in reaction to data or state updating on the backend. An example of this will be when a file is uploaded to cloud storage or the most common when a document / entry in the database has been updated.
RESTful: This is the function that will run when the user makes an http request to the uri the function is assigned to. Nothing special about these ones. Just 1 note that's very important. This will not be used for single CRUD operations like adding a user, deleting a user, updating a user. And it's built with that in mind. This means you won't be able to define a single api endpoint for user that behaves differently based on the HTTP verb used. This is by design and won't be changed. All CRUD should be performed directly on your Firebase DB of choice. That's how this is supposed to be used.

Code structure

We have an enforced code structure that will help with the organization of the backend as well as the overall maintenance as it grows. There's 3 major things to go over.

Each function will be in its own dedicated file: This is to get rid of the "natural" tendency, when starting with firebase cloud functions, to keep adding functions into the same index file forcing it to grow bigger as your backend requirements grow. The file name will be the exact name of the endpoint to keep things easy to manage. This is not a requirement but I've found it to be quite helpful.
Functions will be placed in a folder titled either restful or reactive
The backend will be split into different resource groups to ensure a structured backend in production

Organize your firebase functions folder into api domain folders (groups) and function type (reactive, restful).

src
  {group_name_folder}
    reactive
      - onSomeTrigger.function.ts
      - onSomeOtherTrigger.function.ts
    restful
      - someEndpointName.endpoint.ts
      - someOtherEndpointName.endpoint.ts
  - index.ts
package.json

Code Setup

Installation

We'll start off by installing the package dedicated to using this system firebase-backend. Install the package through npm

npm install firebase-backend

Configuration

Then you can open the index.ts file in your source folder and update it to

import { FunctionParser } from 'firebase-backend';

exports = new FunctionParser(__dirname, exports).exports;

These are the two magical lines of code that allows us to dynamically add and export functions as the backend grows without ever changing the index file 🥳. And that's also all we need to set it up. Now we can start creating functions 😎

Restful Functions (Endpoints)

Create

Let's say we wanted to make an endpoint where a client application could add a payment method for a user.

The API would be called users
The function would be called addPaymentMethod
The file would be called src/users/restful/addPaymentMethod.endpoint.ts
The endpoint name will be exactly the name of your file
The endpoint.ts file extension identifies the function as an HTTP endpoint

// src/users/restful/addPaymentMethod.endpoint.ts
import { Request, Response } from 'express'
import { Post } from 'firebase-backend' // Get, Post, Put, Update, Delete available


// Use the `Post` class which is extended from the `Endpoint` class.
export default new Post((request: Request, response: Response) => {
  // Read the values out of the body
  const cardNumber = request.body['card_number'];
  const cardHolder = request.body['card_holder'];

  // Do your thing with the values
  var paymentToken = `${cardNumber}_${cardHolder}`;

  // Send your response. 201 to indicate the creation of a new resource
  return response.status(201).send({
    token: paymentToken,
  });
});

Middleware You can now pass an array of middleware you'd want to add to an endpoint:

// src/users/restful/auth.middleware.ts
import { Request, Response, NextFunction } from 'express'
export const authMiddleware = (req: Request, res: Response, next: NextFunction) => { ... }

// src/users/restful/addPaymentMethod.endpoint.ts
import { Request, Response } from 'express'
import { EndpointMiddleware, Post } from 'firebase-backend'
import { authMiddleware } from './auth.middleware'

export default new Post((req: Request, res: Response) => {}, {
  middlewares: [authMiddleware]
})

Testing

To test this out we'll run the following command in the functions folder.

npm run serve

This will build the TypeScript code and then serve the functions locally through the emulator. If this is successful you should see the following in the console. You should see the functions API has deployed (locally) a function at the following url

http://localhost:5001/boxtout-fireship/us-central1/users-api

All the endpoints in the users resource group will be deployed under the /user-api function. This means that we can make a post request to the endpoint with the expected data and check if we get back a result. I'm going to use PostMan to test this out. So we'll put in the above url and add /addpaymentmethod at the end of it. Select post as the HTTP request type and then pass in a body.

{
  "card_number": "5418754514815181",
  "card_holder": "FilledStacks"
}

When we execute this we get back the token in the format we supplied

{
  "token": "5418754514815181_FilledStacks"
}

There we have it, your first endpoint created. Next up is reactive functions.

Reactive Functions

Create

Let's say we wanted to make a function that would run when the firestore db had a user record updated.

The API would be called users
The function would be called onUserCreated
The file would be called src/users/reactive/onUserCreated.function.ts
The endpoint name will be exactly the name of your file
The function.ts file extension identifies the function as reactive

// src/users/reactive/onUserCreated.function.ts
import * as functions from 'firebase-functions';


export default functions.firestore
  .document('users/{userId}')
  .onCreate((userSnapshot, context) => {
    const data = userSnapshot.data();
    console.log(`User Created | send an email to ${data.email}`);
  });

Run npm run build in the functions folder. Then run firebase emulators:start.

You should now have a function deployed at users-onUserCreated as well as at users-api. All the api endpoints go under the one api function, but the reactive functions are added as their own functions. Lets test this out.

Testing

At the bottom of your logs you'll see a link to firestore http://localhost:4000/firestore . Open that in your browser. You'll see an empty page. Click on start collection, make the collection id users . Add a field called email and put the value dane@filledstacks.com and save the document. When this is saved you should see the logs printing out the following message

i  functions: Beginning execution of "users-onUserCreated"
>  User id created TybqxAwnC4X5DWLgtXOp
>  {"severity":"WARNING","message":"Function returned undefined, expected Promise or value"}
i  functions: Finished "users-onUserCreated" in ~1s
>  User Created | send an email to dane@filledstacks.com

And that's it! You've created a reactive function as well as a http endpoint. Going further when you want to expand you backend you simply create a new file in the dedicated folder depending on the function type and it'll be added automatically.

Environment Setup

The way that the default TypeScript project is setup is not sufficient for consistent deployments and debugging. Because of that we'll add some additional things into our project. We'll start by making sure that old function code don't lurk around when we're testing any new changes. To fix that we'll add a new package into the functions folder called rimraf

npm install -D rimraf

Then we'll add 2 new scripts into the package.json . Above the build script we'll add clean and prebuild.

"scripts": {
    "lint": "eslint --ext .js,.ts .",
    "clean": "rimraf lib/",
    "prebuild": "npm run clean",
    "build": "tsc",
    "serve": "npm run build && firebase emulators:start --only functions",
    "shell": "npm run build && firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  }

This will now clean out your generated code before building the new code.

Deploy

And finally we can deploy our backend. We first run npm run build when that's complete we run npm run deploy and that will push all the latest function code to your firebase project.

Author

FilledStacks dane@filledstacks.com

Website: https://www.filledstacks.com
GitHub: @FilledStacks

Contributing

Contributions, issues and feature requests are welcome!

Feel free to check issues page.

License

This project is MIT licensed.

mrseth01/firebase-backend