Using firebase in a back-end node service

useFirebase.ts

// Get the imports
import { credential } from 'firebase-admin'
import { initializeApp } from 'firebase-admin/app'
import { getFirestore, CollectionReference, DocumentData } from 'firebase-admin/firestore'

// get the service account - IT SHOULD BE GIT IGNORED!
// Make one and download it here:
// https://console.firebase.google.com/u/0/project/your-project-name/settings/serviceaccounts/adminsdk
const serviceAccount = require('../../firebase-admin-service-account.json')

// Init the firebase app
export const firebaseApp = initializeApp({
  projectId: 'your-project-name',
  // if we're running this on google cloud in prod (eg: Cloud Run) then it'll auto auth us.
  // So we only need the service account in dev.
  credential: process.env.NODE_ENV === 'production' ? undefined : credential.cert(serviceAccount)
})

// Export firestore incase we need to access it directly
export const firestore = getFirestore()

// This is just a helper to add the type to the db responses
const createCollection = <T = DocumentData>(collectionName: string) => {
  return firestore.collection(collectionName) as CollectionReference<T>
}

// Import all your model types
import { User } from '@your-app/types'

// export all your collections
export const db = {
  users: createCollection<User>('users')
}