refactor(payments): unit tests created for calculation of subscription termination date

website/server/libs/payments/util.js

@@ -0,0 +1,32 @@
+import moment from 'moment';
+
+const DEFAULT_REMAINING_DAYS = 30;
+const DEFAULT_REMAINING_DAYS_FOR_GROUP_PLAN = 2;
+
+/**
+ * paymentsApiConstants is provided as parameter because of a dependency cycle
+ * with subscriptions api which will occur if api.constants would be used directly
+ */
+export function calculateSubscriptionTerminationDate (
+  nextBill, purchasedPlan, paymentsApiConstants,
+) {
+  const defaultRemainingDays = (
+    purchasedPlan.customerId === paymentsApiConstants.GROUP_PLAN_CUSTOMER_ID
+  ) ? DEFAULT_REMAINING_DAYS_FOR_GROUP_PLAN
+    : DEFAULT_REMAINING_DAYS;
+  const now = moment();
+
+  const remaining = nextBill
+    ? moment(nextBill).diff(new Date(), 'days', true)
+    : defaultRemainingDays;
+
+  const extraMonths = Math.max(purchasedPlan.extraMonths, 0);
+  const extraDays = Math.ceil(30.5 * extraMonths);
+  const nowStr = `${now.format('MM')}/${now.format('DD')}/${now.format('YYYY')}`;
+  const nowStrFormat = 'MM/DD/YYYY';
+
+  return moment(nowStr, nowStrFormat)
+    .add({ days: remaining })
+    .add({ days: extraDays })
+    .toDate();
+}