getPaymentMethods

The getPaymentMethods Firebase Cloud Function retrieves a list of payment methods (cards) associated with the Stripe customer linked to a specific subscription. It also identifies which payment method is currently set as the default. This function is accessible only to the owner of the subscription.

Function Signature

export const getPaymentMethods = https.onCall(async (data: GetPaymentMethodsData, context) => { ... });

Parameters

The function expects the following data in the data object:

GetPaymentMethodsData Interface:

interface GetPaymentMethodsData {
    subscriptionId: string;
}

Context

The function requires an authenticated user context (context.auth). The authenticated user must also be the owner of the specified subscription.

Behavior

1. Authentication Check: Verifies that the user calling the function is authenticated. If not, it throws an unauthenticated error.
2. Subscription Retrieval: Fetches the subscription document from Firestore using the provided subscriptionId.
   • If the subscription does not exist, it throws a not-found error.
3. Owner Verification: Checks if the authenticated user is the owner (owner_id) of the subscription. If not, it throws a permission-denied error.
4. Stripe Customer ID Retrieval: Retrieves the Stripe subscription to get the associated customer ID.
   • If no customer is found for the subscription, it throws a failed-precondition error.
5. Default Payment Method Identification: Retrieves the Stripe customer details to determine their default payment method.
6. Payment Methods Listing: Calls the Stripe API to list all card payment methods associated with the customer.
7. Mark Default: Iterates through the retrieved payment methods and adds an isDefault: true flag to the one matching the customer’s default payment method.
8. Success: Returns an object containing success: true and an array of paymentMethods (each with an isDefault flag).

Error Handling

The function throws HttpsError with specific codes for different failure scenarios:

• unauthenticated: If the user is not authenticated.
• not-found: If the subscription is not found.
• permission-denied: If the user is not the subscription owner.
• failed-precondition: If no Stripe customer is found for the subscription.
• internal: For any Stripe API errors or other unexpected errors during execution.

Example Usage (Client-side)

import { getFunctions, httpsCallable } from 'firebase/functions';
import { getApp } from 'firebase/app';

const functions = getFunctions(getApp());
const getPaymentMethodsCallable = httpsCallable(functions, 'getPaymentMethods');

async function callGetPaymentMethods(subscriptionId: string) {
    try {
        const result = await getPaymentMethodsCallable({ subscriptionId });
        console.log('Payment methods:', result.data.paymentMethods);
        // Expected result.data.paymentMethods: [{ id: "pm_...", brand: "visa", last4: "4242", isDefault: true }, ...]
    } catch (error) {
        console.error('Error getting payment methods:', error.code, error.message);
    }
}

// Example call
// callGetPaymentMethods('sub_your_stripe_subscription_id');