billing: Move checks from process_initial_upgrade into separate function.

zilencer/lib/stripe.py

@@ -9,7 +9,6 @@ from django.conf import settings
 from django.db import transaction
 from django.utils.translation import ugettext as _
 from django.core.signing import Signer
-from django.core import signing
 import stripe
 
 from zerver.lib.exceptions import JsonableError
@@ -179,23 +178,11 @@ def do_subscribe_customer_to_plan(stripe_customer: stripe.Customer, stripe_plan_
                 requires_billing_update=True,
                 extra_data=ujson.dumps({'quantity': current_seat_count}))
 
-def process_initial_upgrade(user: UserProfile, plan: str, signed_seat_count: str,
-                            salt: str, stripe_token: str) -> None:
-    if plan not in [Plan.CLOUD_ANNUAL, Plan.CLOUD_MONTHLY]:
-        billing_logger.warning("Tampered plan during realm upgrade. user: %s, realm: %s (%s)."
-                               % (user.id, user.realm.id, user.realm.string_id))
-        raise BillingError('tampered plan', BillingError.CONTACT_SUPPORT)
-    try:
-        seat_count = int(unsign_string(signed_seat_count, salt))
-    except signing.BadSignature:
-        billing_logger.warning("Tampered seat count during realm upgrade. user: %s, realm: %s (%s)."
-                               % (user.id, user.realm.id, user.realm.string_id))
-        raise BillingError('tampered seat count', BillingError.CONTACT_SUPPORT)
-
+def process_initial_upgrade(user: UserProfile, plan: Plan, seat_count: int, stripe_token: str) -> None:
     stripe_customer = do_create_customer_with_payment_source(user, stripe_token)
     do_subscribe_customer_to_plan(
         stripe_customer=stripe_customer,
-        stripe_plan_id=Plan.objects.get(nickname=plan).stripe_plan_id,
+        stripe_plan_id=plan.stripe_plan_id,
         seat_count=seat_count,
         # TODO: billing address details are passed to us in the request;
         # use that to calculate taxes.

zilencer/views.py

@@ -1,6 +1,7 @@
-from typing import Any, Dict, Optional, Union, cast
+from typing import Any, Dict, Optional, Tuple, Union, cast
 import logging
 
+from django.core import signing
 from django.core.exceptions import ValidationError
 from django.core.validators import validate_email, URLValidator
 from django.db import IntegrityError
@@ -27,7 +28,7 @@ from zerver.views.push_notifications import validate_token
 from zilencer.lib.stripe import STRIPE_PUBLISHABLE_KEY, \
     get_stripe_customer, get_upcoming_invoice, get_seat_count, \
     extract_current_subscription, process_initial_upgrade, sign_string, \
-    BillingError
+    unsign_string, BillingError
 from zilencer.models import RemotePushDeviceToken, RemoteZulipServer, \
     Customer, Plan
 
@@ -158,6 +159,22 @@ def remote_server_notify_push(request: HttpRequest, entity: Union[UserProfile, R
 
     return json_success()
 
+def unsign_and_check_upgrade_parameters(user: UserProfile, plan_nickname: str,
+                                        signed_seat_count: str, salt: str) -> Tuple[Plan, int]:
+    if plan_nickname not in [Plan.CLOUD_ANNUAL, Plan.CLOUD_MONTHLY]:
+        billing_logger.warning("Tampered plan during realm upgrade. user: %s, realm: %s (%s)."
+                               % (user.id, user.realm.id, user.realm.string_id))
+        raise BillingError('tampered plan', BillingError.CONTACT_SUPPORT)
+    plan = Plan.objects.get(nickname=plan_nickname)
+
+    try:
+        seat_count = int(unsign_string(signed_seat_count, salt))
+    except signing.BadSignature:
+        billing_logger.warning("Tampered seat count during realm upgrade. user: %s, realm: %s (%s)."
+                               % (user.id, user.realm.id, user.realm.string_id))
+        raise BillingError('tampered seat count', BillingError.CONTACT_SUPPORT)
+    return plan, seat_count
+
 @zulip_login_required
 def initial_upgrade(request: HttpRequest) -> HttpResponse:
     if not settings.DEVELOPMENT:
@@ -172,8 +189,9 @@ def initial_upgrade(request: HttpRequest) -> HttpResponse:
 
     if request.method == 'POST':
         try:
-            process_initial_upgrade(user, request.POST['plan'], request.POST['signed_seat_count'],
-                                    request.POST['salt'], request.POST['stripeToken'])
+            plan, seat_count = unsign_and_check_upgrade_parameters(
+                user, request.POST['plan'], request.POST['signed_seat_count'], request.POST['salt'])
+            process_initial_upgrade(user, plan, seat_count, request.POST['stripeToken'])
         except BillingError as e:
             error_message = e.message
             error_description = e.description