feat: update subscription when increasing/decreasing workspace members

packages/stripe/src/index.ts

@@ -16,4 +16,59 @@ const createStripeClient = () => {
   return stripe;
 };
 
+export const updateSubscriptionSeats = async (
+  stripeSubscriptionId: string,
+  seatIncrement = 1,
+): Promise<Stripe.Subscription> => {
+  const stripe = createStripeClient();
+
+  // First, retrieve the current subscription to get the subscription items
+  const subscription = await stripe.subscriptions.retrieve(
+    stripeSubscriptionId,
+    {
+      expand: ["items"],
+    },
+  );
+
+  if (!subscription.items.data.length) {
+    throw new Error(
+      `No subscription items found for subscription ${stripeSubscriptionId}`,
+    );
+  }
+
+  // Get the first subscription item
+  const subscriptionItem = subscription.items.data[0];
+  if (!subscriptionItem) {
+    throw new Error(
+      `No subscription item found for subscription ${stripeSubscriptionId}`,
+    );
+  }
+
+  const currentQuantity = subscriptionItem.quantity ?? 1;
+  const newQuantity = currentQuantity + seatIncrement;
+
+  // Ensure we don't go below 1 seat
+  if (newQuantity < 1) {
+    throw new Error(
+      `Cannot reduce seats below 1. Current: ${currentQuantity}, Requested change: ${seatIncrement}`,
+    );
+  }
+
+  // Update the subscription with the new quantity and immediate invoicing
+  const updatedSubscription = await stripe.subscriptions.update(
+    stripeSubscriptionId,
+    {
+      items: [
+        {
+          id: subscriptionItem.id,
+          quantity: newQuantity,
+        },
+      ],
+      proration_behavior: "always_invoice", // Accumulate charges for next billing cycle
+    },
+  );
+
+  return updatedSubscription;
+};
+
 export { createStripeClient };