Passing stripe errors to firebase firestore

Question

I'm trying to pass Stripe errors such as (card declined, not enough money on card, card expired etc...) to Firebase Firestore then to the client.

I dont know how to make it work for Firestore

Any help would be appreciated. Thanks

Here's my code:

    exports = module.exports = functions.firestore.document('/users/{userId}/charges/{id}').onWrite(event => {
   const val = event.data.data();
   const ref =  event.data.ref;

    if (val === null) return null;
    const amount = val.amount;
    const destination = val.destination;

  return admin.firestore().collection('users').doc(`${event.params.userId}`).get().then(snapshot => {
    return snapshot.data();
  }).then(customer => {
      if (!customer.exists) { 
            console.log("NO SUCH CUSTOMER");
         } else {
        const amount = val.amount;
        const customer_id = customer.customer_id;

        stripe.charges.create({
            amount: amount * 100 ,
            currency: "usd",
            customer: customer_id,
            destination: {
               account: destination,
           },
        });
      }
  }).then(response => {
       console.log("RESPONSE", response);
      // If the result is successful, write it back to the database
      // WRITE RESPONSE BACK
       return event.data.ref.set(response, {merge: true});
    }, error => {
       // WRITE ERRORS BACK
        console.log("ERROR", error);
      return event.data.ref.set(error, {merge: true});
    }).catch((error) => {
//    // We want to capture errors and render them in a user-friendly way, while
//    // still logging an exception with Stackdriver
        return event.data.ref.set(userFacingMessage(error));
      }).then(() => {
        //return reportError(error, {user: event.params.userId});
    });
});