A gist for creating Stripe users with Firebase and Google Cloud Functions

app.js

import { databse } from 'firebase'

const userRef = database().ref('users/' + uid) // Assumes you have the users uid
userRef.update({ token, lastFour }) // Assumes you've used Stripe.js to get a card token and lastFour
userRef.child('stripeCustomerId').on('value', snap => {
  let stripeCustomerId = snap.val()
  if (stripeCustomerId) {
    userRef.child('charges').push({ 
      amount: 4000, // $40
      currency: 'usd',
      description: 'Example charge',
      customer: stripeCustomerId
    }) 
    userRef.child('stripeCustomerId').off('value')
  }
})

index.js

const functions = require('firebase-functions')
const stripe = require('stripe')(functions.config().stripe.sk) 
// Add secret key to config by running this command on the command line:
// $ firebase functions:config:set stripe.sk="sk_live_f7ag7agaslkflkjasdfjkla"

exports.updateCard = functions.database.ref('/users/{uid}/token').onWrite(event => {
  let token = event.data.val()
  if (token) {
    let userRef = event.data.ref.parent
    return userRef.once('value', snap => {
      let user = snap.val()
      if (token && user.stripeCustomerId) {
        // If the user is already registered with Stripe just update the card
        return stripe.customers.update(user.stripeCustomerId, { source: token })
      } else if (token) {
        // Otherwise, create a new Stripe customer and save the customer id to firebase
        return stripe.customers.create({
          description: 'User ' + user.email,
          source: token,
          email: user.email
        }).then(stripeCustomer => userRef.update({ stripeCustomerId: stripeCustomer.id })
      }
    })
  }
})


exports.chargeUser = functions.database.ref('/users/{uid}/charges/{chargeId}').onWrite(event => {
  let charge = event.data.val()
  // Make sure the charge object you save is the correct format for Stripe charges like on lines 8-13 in frontend/app.js above
  stripe.charges.create(charge).then(() => event.data.ref.update({ charged: true }))
}