I am trying to update a user's firestore doc from a Firebase Function using a query, and having issues getting it to work. My Function code is the following:

const functions = require('firebase-functions');

// The Firebase Admin SDK to access Firestore.
const admin = require('firebase-admin');
admin.initializeApp();

/**
 * A webhook handler function for the relevant Stripe events.
 */

// Here would be the function that calls updatePlan and passes it the customer email,
// I've omitted it to simplify the snippet


const updatePlan = async (customerEmail) => {

  await admin.firestore()
    .collection('users').where('email', '==', customerEmail).get()
    .then((doc) => {
      const ref = doc.ref;
      ref.update({ 'purchasedTemplateOne': true });
    });
};

I'm getting the following error in the firebase logs when the query is run:

Exception from a finished function: TypeError: Cannot read properties of undefined (reading 'update')

Any help regarding what I may be doing wrong or suggestions on how I could achieve this would be greatly appreciated, Thank you in advance!

Update:

I was able to solve my problem with more understanding of Firestore Queries:

const updatePlan = (customerEmail) => {

  const customerQuery = admin.firestore().collection("users").where("email", "==", customerEmail)
  customerQuery.get().then(querySnapshot => {
    if (!querySnapshot.empty) {
      // Get just the one customer/user document
      const snapshot = querySnapshot.docs[0]
      // Reference of customer/user doc
      const documentRef = snapshot.ref
      documentRef.update({ 'purchasedTemplateOne': true })
      functions.logger.log("User Document Updated:", documentRef);
    }
    else {
      functions.logger.log("User Document Does Not Exist");
    }
  })

};