billing: Extract out validate_licenses function.

corporate/lib/stripe.py

@@ -71,6 +71,26 @@ def unsign_string(signed_string: str, salt: str) -> str:
     return signer.unsign(signed_string)
 
 
+def validate_licenses(charge_automatically: bool, licenses: Optional[int], seat_count: int) -> None:
+    min_licenses = seat_count
+    max_licenses = None
+    if not charge_automatically:
+        min_licenses = max(seat_count, MIN_INVOICED_LICENSES)
+        max_licenses = MAX_INVOICED_LICENSES
+
+    if licenses is None or licenses < min_licenses:
+        raise BillingError(
+            "not enough licenses", _("You must invoice for at least {} users.").format(min_licenses)
+        )
+
+    if max_licenses is not None and licenses > max_licenses:
+        message = _(
+            "Invoices with more than {} licenses can't be processed from this page. To complete "
+            "the upgrade, please contact {}."
+        ).format(max_licenses, settings.ZULIP_ADMINISTRATOR)
+        raise BillingError("too many licenses", message)
+
+
 # Be extremely careful changing this function. Historical billing periods
 # are not stored anywhere, and are just computed on the fly using this
 # function. Any change you make here should return the same value (or be

corporate/tests/test_stripe.py

@@ -1363,7 +1363,7 @@ class StripeTest(StripeTestCase):
         # Invoice with licenses < MIN_INVOICED_LICENSES
         check_min_licenses_error(True, MIN_INVOICED_LICENSES - 1, MIN_INVOICED_LICENSES)
         # Invoice with licenses < seat count
-        with patch("corporate.views.MIN_INVOICED_LICENSES", 3):
+        with patch("corporate.lib.stripe.MIN_INVOICED_LICENSES", 3):
             check_min_licenses_error(True, 4, self.seat_count)
         # Invoice with not setting licenses
         check_min_licenses_error(True, None, MIN_INVOICED_LICENSES)

corporate/views.py

@@ -14,7 +14,6 @@ from django.utils.translation import gettext as _
 
 from corporate.lib.stripe import (
     DEFAULT_INVOICE_DAYS_UNTIL_DUE,
-    MAX_INVOICED_LICENSES,
     MIN_INVOICED_LICENSES,
     STRIPE_PUBLISHABLE_KEY,
     BillingError,
@@ -31,6 +30,7 @@ from corporate.lib.stripe import (
     stripe_get_customer,
     unsign_string,
     update_sponsorship_status,
+    validate_licenses,
 )
 from corporate.models import (
     CustomerPlan,
@@ -78,27 +78,13 @@ def check_upgrade_parameters(
     if license_management not in VALID_LICENSE_MANAGEMENT_VALUES:  # nocoverage
         raise BillingError("unknown license_management")
 
+    charge_automatically = False
     if billing_modality == "charge_automatically":
+        charge_automatically = True
         if not has_stripe_token:
             raise BillingError("autopay with no card")
 
-    min_licenses = seat_count
-    max_licenses = None
-    if billing_modality == "send_invoice":
-        min_licenses = max(seat_count, MIN_INVOICED_LICENSES)
-        max_licenses = MAX_INVOICED_LICENSES
-
-    if licenses is None or licenses < min_licenses:
-        raise BillingError(
-            "not enough licenses", _("You must invoice for at least {} users.").format(min_licenses)
-        )
-
-    if max_licenses is not None and licenses > max_licenses:
-        message = _(
-            "Invoices with more than {} licenses can't be processed from this page. To complete "
-            "the upgrade, please contact {}."
-        ).format(max_licenses, settings.ZULIP_ADMINISTRATOR)
-        raise BillingError("too many licenses", message)
+    validate_licenses(charge_automatically, licenses, seat_count)
 
 
 # Should only be called if the customer is being charged automatically