billing: Add backend support for downgrading.

corporate/lib/stripe.py

@@ -82,7 +82,6 @@ def next_month(billing_cycle_anchor: datetime, dt: datetime) -> datetime:
     raise AssertionError('Something wrong in next_month calculation with '
                          'billing_cycle_anchor: %s, dt: %s' % (billing_cycle_anchor, dt))
 
-# TODO take downgrade into account
 def start_of_next_billing_cycle(plan: CustomerPlan, event_time: datetime) -> datetime:
     months_per_period = {
         CustomerPlan.ANNUAL: 12,
@@ -95,8 +94,10 @@ def start_of_next_billing_cycle(plan: CustomerPlan, event_time: datetime) -> dat
         periods += 1
     return dt
 
-# TODO take downgrade into account
-def next_invoice_date(plan: CustomerPlan) -> datetime:
+def next_invoice_date(plan: CustomerPlan) -> Optional[datetime]:
+    if plan.status == CustomerPlan.ENDED:
+        return None
+    assert(plan.next_invoice_date is not None)  # for mypy
     months_per_period = {
         CustomerPlan.ANNUAL: 12,
         CustomerPlan.MONTHLY: 1,
@@ -114,6 +115,8 @@ def renewal_amount(plan: CustomerPlan, event_time: datetime) -> int:  # nocovera
     if plan.fixed_price is not None:
         return plan.fixed_price
     last_ledger_entry = make_end_of_cycle_updates_if_needed(plan, event_time)
+    if last_ledger_entry is None:
+        return 0
     if last_ledger_entry.licenses_at_next_renewal is None:
         return 0
     assert(plan.price_per_license is not None)  # for mypy
@@ -215,17 +218,21 @@ def do_replace_payment_source(user: UserProfile, stripe_token: str,
 
 # event_time should roughly be timezone_now(). Not designed to handle
 # event_times in the past or future
-# TODO handle downgrade
-def make_end_of_cycle_updates_if_needed(plan: CustomerPlan, event_time: datetime) -> LicenseLedger:
+def make_end_of_cycle_updates_if_needed(plan: CustomerPlan,
+                                        event_time: datetime) -> Optional[LicenseLedger]:
     last_ledger_entry = LicenseLedger.objects.filter(plan=plan).order_by('-id').first()
     last_renewal = LicenseLedger.objects.filter(plan=plan, is_renewal=True) \
                                         .order_by('-id').first().event_time
-    plan_renewal_date = start_of_next_billing_cycle(plan, last_renewal)
-    if plan_renewal_date <= event_time:
-        return LicenseLedger.objects.create(
-            plan=plan, is_renewal=True, event_time=plan_renewal_date,
-            licenses=last_ledger_entry.licenses_at_next_renewal,
-            licenses_at_next_renewal=last_ledger_entry.licenses_at_next_renewal)
+    next_billing_cycle = start_of_next_billing_cycle(plan, last_renewal)
+    if next_billing_cycle <= event_time:
+        if plan.status == CustomerPlan.ACTIVE:
+            return LicenseLedger.objects.create(
+                plan=plan, is_renewal=True, event_time=next_billing_cycle,
+                licenses=last_ledger_entry.licenses_at_next_renewal,
+                licenses_at_next_renewal=last_ledger_entry.licenses_at_next_renewal)
+        if plan.status == CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE:
+            process_downgrade(plan)
+        return None
     return last_ledger_entry
 
 # Returns Customer instead of stripe_customer so that we don't make a Stripe
@@ -362,7 +369,8 @@ def process_initial_upgrade(user: UserProfile, licenses: int, automanage_license
 def update_license_ledger_for_automanaged_plan(realm: Realm, plan: CustomerPlan,
                                                event_time: datetime) -> None:
     last_ledger_entry = make_end_of_cycle_updates_if_needed(plan, event_time)
-    # todo: handle downgrade, where licenses_at_next_renewal should be 0
+    if last_ledger_entry is None:
+        return
     licenses_at_next_renewal = get_seat_count(realm)
     licenses = max(licenses_at_next_renewal, last_ledger_entry.licenses)
     LicenseLedger.objects.create(
@@ -464,8 +472,17 @@ def get_discount_for_realm(realm: Realm) -> Optional[Decimal]:
         return customer.default_discount
     return None
 
-def process_downgrade(user: UserProfile) -> None:  # nocoverage
-    pass
+def do_change_plan_status(plan: CustomerPlan, status: int) -> None:
+    plan.status = status
+    plan.save(update_fields=['status'])
+    billing_logger.info('Change plan status: Customer.id: %s, CustomerPlan.id: %s, status: %s' % (
+        plan.customer.id, plan.id, status))
+
+def process_downgrade(plan: CustomerPlan) -> None:
+    from zerver.lib.actions import do_change_plan_type
+    do_change_plan_type(plan.customer.realm, Realm.LIMITED)
+    plan.status = CustomerPlan.ENDED
+    plan.save(update_fields=['status'])
 
 def estimate_annual_recurring_revenue_by_realm() -> Dict[str, int]:  # nocoverage
     annual_revenue = {}

corporate/migrations/0008_nullable_next_invoice_date.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.20 on 2019-04-11 00:45
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('corporate', '0007_remove_deprecated_fields'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='customerplan',
+            name='next_invoice_date',
+            field=models.DateTimeField(db_index=True, null=True),
+        ),
+    ]

corporate/models.py

@@ -35,7 +35,7 @@ class CustomerPlan(models.Model):
     MONTHLY = 2
     billing_schedule = models.SmallIntegerField()  # type: int
 
-    next_invoice_date = models.DateTimeField(db_index=True)  # type: datetime.datetime
+    next_invoice_date = models.DateTimeField(db_index=True, null=True)  # type: Optional[datetime.datetime]
     invoiced_through = models.ForeignKey(
         'LicenseLedger', null=True, on_delete=CASCADE, related_name='+')  # type: Optional[LicenseLedger]
     DONE = 1
@@ -69,6 +69,5 @@ class LicenseLedger(models.Model):
     event_time = models.DateTimeField()  # type: datetime.datetime
     licenses = models.IntegerField()  # type: int
     # None means the plan does not automatically renew.
-    # 0 means the plan has been explicitly downgraded.
     # This cannot be None if plan.automanage_licenses.
     licenses_at_next_renewal = models.IntegerField(null=True)  # type: Optional[int]

corporate/tests/test_stripe.py

@@ -873,6 +873,88 @@ def test_replace_payment_source(self, *mocks: Mock) -> None:
         self.assertEqual(2, RealmAuditLog.objects.filter(
             event_type=RealmAuditLog.STRIPE_CARD_CHANGED).count())
 
+    @patch("corporate.lib.stripe.billing_logger.info")
+    def test_downgrade(self, mock_: Mock) -> None:
+        user = self.example_user("hamlet")
+        self.login(user.email)
+        with patch("corporate.lib.stripe.timezone_now", return_value=self.now):
+            self.local_upgrade(self.seat_count, True, CustomerPlan.ANNUAL, 'token')
+        response = self.client_post("/json/billing/plan/change",
+                                    {'status': CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE})
+        self.assert_json_success(response)
+
+        # Verify that we still write LicenseLedger rows during the remaining
+        # part of the cycle
+        with patch("corporate.lib.stripe.get_seat_count", return_value=20):
+            update_license_ledger_if_needed(user.realm, self.now)
+        self.assertEqual(LicenseLedger.objects.order_by('-id').values_list(
+            'licenses', 'licenses_at_next_renewal').first(), (20, 20))
+
+        # Verify that we invoice them for the additional users
+        from stripe import Invoice
+        Invoice.create = lambda **args: None  # type: ignore # cleaner than mocking
+        Invoice.finalize_invoice = lambda *args: None  # type: ignore # cleaner than mocking
+        with patch("stripe.InvoiceItem.create") as mocked:
+            invoice_plans_as_needed(self.next_month)
+        mocked.assert_called_once()
+        mocked.reset_mock()
+
+        # Check that we downgrade properly if the cycle is over
+        with patch("corporate.lib.stripe.get_seat_count", return_value=30):
+            update_license_ledger_if_needed(user.realm, self.next_year)
+        self.assertEqual(get_realm('zulip').plan_type, Realm.LIMITED)
+        self.assertEqual(CustomerPlan.objects.first().status, CustomerPlan.ENDED)
+        self.assertEqual(LicenseLedger.objects.order_by('-id').values_list(
+            'licenses', 'licenses_at_next_renewal').first(), (20, 20))
+
+        # Verify that we don't write LicenseLedger rows once we've downgraded
+        with patch("corporate.lib.stripe.get_seat_count", return_value=40):
+            update_license_ledger_if_needed(user.realm, self.next_year)
+        self.assertEqual(LicenseLedger.objects.order_by('-id').values_list(
+            'licenses', 'licenses_at_next_renewal').first(), (20, 20))
+
+        # Verify that we call invoice_plan once more after cycle end but
+        # don't invoice them for users added after the cycle end
+        self.assertIsNotNone(CustomerPlan.objects.first().next_invoice_date)
+        with patch("stripe.InvoiceItem.create") as mocked:
+            invoice_plans_as_needed(self.next_year + timedelta(days=32))
+        mocked.assert_not_called()
+        mocked.reset_mock()
+        # Check that we updated next_invoice_date in invoice_plan
+        self.assertIsNone(CustomerPlan.objects.first().next_invoice_date)
+
+        # Check that we don't call invoice_plan after that final call
+        with patch("corporate.lib.stripe.get_seat_count", return_value=50):
+            update_license_ledger_if_needed(user.realm, self.next_year + timedelta(days=80))
+        with patch("corporate.lib.stripe.invoice_plan") as mocked:
+            invoice_plans_as_needed(self.next_year + timedelta(days=400))
+        mocked.assert_not_called()
+
+    @patch("corporate.lib.stripe.billing_logger.info")
+    @patch("stripe.Invoice.create")
+    @patch("stripe.Invoice.finalize_invoice")
+    @patch("stripe.InvoiceItem.create")
+    def test_downgrade_during_invoicing(self, *mocks: Mock) -> None:
+        # The difference between this test and test_downgrade is that
+        # CustomerPlan.status is DOWNGRADE_AT_END_OF_CYCLE rather than ENDED
+        # when we call invoice_plans_as_needed
+        # This test is essentially checking that we call make_end_of_cycle_updates_if_needed
+        # during the invoicing process.
+        user = self.example_user("hamlet")
+        self.login(user.email)
+        with patch("corporate.lib.stripe.timezone_now", return_value=self.now):
+            self.local_upgrade(self.seat_count, True, CustomerPlan.ANNUAL, 'token')
+        self.client_post("/json/billing/plan/change",
+                         {'status': CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE})
+
+        plan = CustomerPlan.objects.first()
+        self.assertIsNotNone(plan.next_invoice_date)
+        self.assertEqual(plan.status, CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE)
+        invoice_plans_as_needed(self.next_year)
+        plan = CustomerPlan.objects.first()
+        self.assertIsNone(plan.next_invoice_date)
+        self.assertEqual(plan.status, CustomerPlan.ENDED)
+
 class RequiresBillingAccessTest(ZulipTestCase):
     def setUp(self) -> None:
         hamlet = self.example_user("hamlet")
@@ -888,7 +970,7 @@ def verify_non_admins_blocked_from_endpoint(
     def test_non_admins_blocked_from_json_endpoints(self) -> None:
         params = [
             ("/json/billing/sources/change", {'stripe_token': ujson.dumps('token')}),
-            ("/json/billing/downgrade", {}),
+            ("/json/billing/plan/change", {'status': ujson.dumps(1)}),
         ]  # type: List[Tuple[str, Dict[str, Any]]]
 
         for (url, data) in params:

corporate/urls.py

@@ -19,8 +19,8 @@
 v1_api_and_json_patterns = [
     url(r'^billing/upgrade$', rest_dispatch,
         {'POST': 'corporate.views.upgrade'}),
-    url(r'^billing/downgrade$', rest_dispatch,
-        {'POST': 'corporate.views.downgrade'}),
+    url(r'^billing/plan/change$', rest_dispatch,
+        {'POST': 'corporate.views.change_plan_at_end_of_cycle'}),
     url(r'^billing/sources/change', rest_dispatch,
         {'POST': 'corporate.views.replace_payment_source'}),
 ]

corporate/views.py

@@ -19,7 +19,7 @@
 from corporate.lib.stripe import STRIPE_PUBLISHABLE_KEY, \
     stripe_get_customer, get_seat_count, \
     process_initial_upgrade, sign_string, \
-    unsign_string, BillingError, process_downgrade, do_replace_payment_source, \
+    unsign_string, BillingError, do_change_plan_status, do_replace_payment_source, \
     MIN_INVOICED_LICENSES, DEFAULT_INVOICE_DAYS_UNTIL_DUE, \
     start_of_next_billing_cycle, renewal_amount, \
     make_end_of_cycle_updates_if_needed
@@ -160,6 +160,13 @@ def billing_home(request: HttpRequest) -> HttpResponse:
         return render(request, 'corporate/billing.html', context=context)
     context = {'admin_access': True}
 
+    plan_name = "Zulip Free"
+    licenses = 0
+    renewal_date = ''
+    renewal_cents = 0
+    payment_method = ''
+    charge_automatically = False
+
     stripe_customer = stripe_get_customer(customer.stripe_customer_id)
     plan = get_current_plan(customer)
     if plan is not None:
@@ -169,25 +176,17 @@ def billing_home(request: HttpRequest) -> HttpResponse:
         }[plan.tier]
         now = timezone_now()
         last_ledger_entry = make_end_of_cycle_updates_if_needed(plan, now)
-        licenses = last_ledger_entry.licenses
-        licenses_used = get_seat_count(user.realm)
-        # Should do this in javascript, using the user's timezone
-        renewal_date = '{dt:%B} {dt.day}, {dt.year}'.format(dt=start_of_next_billing_cycle(plan, now))
-        renewal_cents = renewal_amount(plan, now)
-        charge_automatically = plan.charge_automatically
-        if charge_automatically:
-            payment_method = payment_method_string(stripe_customer)
-        else:
-            payment_method = 'Billed by invoice'
-    # Can only get here by subscribing and then downgrading. We don't support downgrading
-    # yet, but keeping this code here since we will soon.
-    else:  # nocoverage
-        plan_name = "Zulip Free"
-        licenses = 0
-        renewal_date = ''
-        renewal_cents = 0
-        payment_method = ''
-        charge_automatically = False
+        if last_ledger_entry is not None:
+            licenses = last_ledger_entry.licenses
+            licenses_used = get_seat_count(user.realm)
+            # Should do this in javascript, using the user's timezone
+            renewal_date = '{dt:%B} {dt.day}, {dt.year}'.format(dt=start_of_next_billing_cycle(plan, now))
+            renewal_cents = renewal_amount(plan, now)
+            charge_automatically = plan.charge_automatically
+            if charge_automatically:
+                payment_method = payment_method_string(stripe_customer)
+            else:
+                payment_method = 'Billed by invoice'
 
     context.update({
         'plan_name': plan_name,
@@ -203,11 +202,13 @@ def billing_home(request: HttpRequest) -> HttpResponse:
     return render(request, 'corporate/billing.html', context=context)
 
 @require_billing_access
-def downgrade(request: HttpRequest, user: UserProfile) -> HttpResponse:  # nocoverage
-    try:
-        process_downgrade(user)
-    except BillingError as e:
-        return json_error(e.message, data={'error_description': e.description})
+@has_request_variables
+def change_plan_at_end_of_cycle(request: HttpRequest, user: UserProfile,
+                                status: int=REQ("status", validator=check_int)) -> HttpResponse:
+    assert(status in [CustomerPlan.ACTIVE, CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE])
+    plan = get_current_plan(Customer.objects.get(realm=user.realm))
+    assert(plan is not None)  # for mypy
+    do_change_plan_status(plan, status)
     return json_success()
 
 @require_billing_access