✨(backend) send email reminder of upcoming debit installment

The new django command `send_mail_upcoming_debit` will
retrieve all 'pending' state installments on orders
payment schedules and send a reminder email with a certain
amount of days in advance (configured with
`JOANIE_INSTALLMENT_REMINDER_PERIOD_DAYS`) to the order's
owner notifying them that they will be debited on their
credit card.

Fix #864

CHANGELOG.md

@@ -10,6 +10,8 @@ and this project adheres to
 
 ### Added
 
+- Send an email reminder to the user when an installment
+  will be debited on his credit card on his order's payment schedule
 - Send an email to the user when an installment debit has been
   refused
 - Send an email to the user when an installment is successfully

src/backend/joanie/core/management/commands/send_mail_upcoming_debit.py

@@ -0,0 +1,52 @@
+"""Management command to send a reminder email to the order's owner on next installment to pay"""
+
+import logging
+from datetime import timedelta
+
+from django.conf import settings
+from django.core.management import BaseCommand
+from django.utils import timezone
+
+from joanie.core.models import Order
+from joanie.core.tasks.payment_schedule import send_mail_reminder_installment_debit_task
+from joanie.core.utils.payment_schedule import is_next_installment_to_debit
+
+logger = logging.getLogger(__name__)
+
+
+class Command(BaseCommand):
+    """
+    Command to send an email to the order's owner notifying them that an upcoming
+    installment debit from their payment schedule will be debited soon on their credit card.
+    """
+
+    help = __doc__
+
+    def handle(self, *args, **options):
+        """
+        Retrieve all upcoming pending payment schedules depending on the target due date and
+        send an email reminder to the order's owner who will be soon debited.
+        """
+        logger.info(
+            "Starting processing order payment schedule for upcoming installments."
+        )
+        due_date = timezone.localdate() + timedelta(
+            days=settings.JOANIE_INSTALLMENT_REMINDER_PERIOD_DAYS
+        )
+
+        found_orders_count = 0
+        for order in Order.objects.find_pending_installments().iterator():
+            for installment in order.payment_schedule:
+                if is_next_installment_to_debit(
+                    installment=installment, due_date=due_date
+                ):
+                    logger.info("Sending reminder mail for order %s.", order.id)
+                    send_mail_reminder_installment_debit_task.delay(
+                        order_id=order.id, installment_id=installment["id"]
+                    )
+            found_orders_count += 1
+
+        logger.info(
+            "Found %s upcoming 'pending' installment to debit",
+            found_orders_count,
+        )

src/backend/joanie/core/tasks/payment_schedule.py

@@ -4,7 +4,10 @@
 
 from joanie.celery_app import app
 from joanie.core.models import Order
-from joanie.core.utils.payment_schedule import is_installment_to_debit
+from joanie.core.utils.payment_schedule import (
+    is_installment_to_debit,
+    send_mail_reminder_for_installment_debit,
+)
 from joanie.payment import get_payment_backend
 
 logger = getLogger(__name__)
@@ -30,3 +33,20 @@ def debit_pending_installment(order_id):
                 credit_card_token=order.credit_card.token,
                 installment=installment,
             )
+
+
+@app.task
+def send_mail_reminder_installment_debit_task(order_id, installment_id):
+    """
+    Task to send an email reminder to the order's owner about the next installment debit.
+    """
+    order = Order.objects.get(id=order_id)
+    installment = next(
+        (
+            installment
+            for installment in order.payment_schedule
+            if installment["id"] == installment_id
+        ),
+        None,
+    )
+    send_mail_reminder_for_installment_debit(order, installment)

src/backend/joanie/core/utils/payment_schedule.py

@@ -8,13 +8,16 @@
 
 from django.conf import settings
 from django.utils import timezone
+from django.utils.translation import gettext as _
+from django.utils.translation import override
 
 from dateutil.relativedelta import relativedelta
 from stockholm import Money, Number
 from stockholm.exceptions import ConversionError
 
 from joanie.core import enums
 from joanie.core.exceptions import InvalidConversionError
+from joanie.core.utils.emails import prepare_context_for_upcoming_installment, send
 from joanie.payment import get_country_calendar
 
 logger = logging.getLogger(__name__)
@@ -144,6 +147,18 @@ def is_installment_to_debit(installment):
     )
 
 
+def is_next_installment_to_debit(installment, due_date):
+    """
+    Check if the installment is pending and also if its due date will be equal to the parameter
+    `due_date` passed.
+    """
+
+    return (
+        installment["state"] == enums.PAYMENT_STATE_PENDING
+        and installment["due_date"] == due_date
+    )
+
+
 def has_installments_to_debit(order):
     """
     Check if the order has any pending installments with reached due date.
@@ -176,3 +191,31 @@ def convert_amount_str_to_money_object(amount_str: str):
         raise InvalidConversionError(
             f"Invalid format for amount: {exception} : '{amount_str}'."
         ) from exception
+
+
+def send_mail_reminder_for_installment_debit(order, installment):
+    """
+    Prepare the context variables for the mail reminder when the next installment debit
+    from the payment schedule will happen for the owner of the order.
+    """
+    with override(order.owner.language):
+        product_title = order.product.safe_translation_getter(
+            "title", language_code=order.owner.language
+        )
+        currency = settings.DEFAULT_CURRENCY
+        days_until_debit = settings.JOANIE_INSTALLMENT_REMINDER_PERIOD_DAYS
+        installment_amount = Money(installment["amount"])
+        subject = _(
+            f"{settings.JOANIE_CATALOG_NAME} - {product_title} - "
+            f"An installment of {installment_amount} {currency} will be debited in "
+            f"{days_until_debit} days."
+        )
+
+        send(
+            subject=subject,
+            template_vars=prepare_context_for_upcoming_installment(
+                order, installment_amount, product_title, days_until_debit
+            ),
+            template_name="installment_reminder",
+            to_user_email=order.owner.email,
+        )

src/backend/joanie/payment/backends/base.py

@@ -1,12 +1,9 @@
 """Base Payment Backend"""
 
-import smtplib
 from logging import getLogger
 
 from django.conf import settings
 from django.contrib.sites.models import Site
-from django.core.mail import send_mail
-from django.template.loader import render_to_string
 from django.urls import reverse
 from django.utils.translation import gettext as _
 from django.utils.translation import override
@@ -67,36 +64,14 @@ def _do_on_payment_success(cls, order, payment):
             upcoming_installment=not upcoming_installment,
         )
 
-    @classmethod
-    def _send_mail(cls, subject, template_vars, template_name, to_user_email):
-        """Send mail with the current language of the user"""
-        try:
-            msg_html = render_to_string(
-                f"mail/html/{template_name}.html", template_vars
-            )
-            msg_plain = render_to_string(
-                f"mail/text/{template_name}.txt", template_vars
-            )
-            send_mail(
-                subject,
-                msg_plain,
-                settings.EMAIL_FROM,
-                [to_user_email],
-                html_message=msg_html,
-                fail_silently=False,
-            )
-        except smtplib.SMTPException as exception:
-            # no exception raised as user can't sometimes change his mail,
-            logger.error("%s purchase order mail %s not send", to_user_email, exception)
-
     @classmethod
     def _send_mail_subscription_success(cls, order):
         """
         Send mail with the current language of the user when an order subscription is
         confirmed
         """
         with override(order.owner.language):
-            cls._send_mail(
+            emails.send(
                 subject=_("Subscription confirmed!"),
                 template_vars={
                     "title": _("Subscription confirmed!"),
@@ -136,7 +111,7 @@ def _send_mail_payment_installment_success(
                     f"Order completed ! The last installment of {installment_amount} {currency} "
                     "has been debited"
                 )
-            cls._send_mail(
+            emails.send(
                 subject=f"{base_subject}{variable_subject_part}",
                 template_vars=emails.prepare_context_data(
                     order,
@@ -174,7 +149,7 @@ def _send_mail_refused_debit(cls, order, installment_id):
             product_title = order.product.safe_translation_getter(
                 "title", language_code=order.owner.language
             )
-            cls._send_mail(
+            emails.send(
                 subject=_(
                     f"{settings.JOANIE_CATALOG_NAME} - {product_title} - An installment debit "
                     f"has failed {installment_amount} {settings.DEFAULT_CURRENCY}"

src/backend/joanie/tests/core/tasks/test_payment_schedule.py

@@ -4,25 +4,38 @@
 
 import json
 from datetime import date, datetime
+from decimal import Decimal as D
 from logging import Logger
 from unittest import mock
 from zoneinfo import ZoneInfo
 
+from django.core import mail
+from django.core.management import call_command
 from django.test import TestCase
+from django.test.utils import override_settings
 from django.urls import reverse
 
 from rest_framework.test import APIRequestFactory
 from stockholm import Money
 
 from joanie.core.enums import (
     ORDER_STATE_PENDING,
+    ORDER_STATE_PENDING_PAYMENT,
     ORDER_STATE_TO_SAVE_PAYMENT_METHOD,
     PAYMENT_STATE_PAID,
     PAYMENT_STATE_PENDING,
     PAYMENT_STATE_REFUSED,
 )
-from joanie.core.factories import OrderFactory, UserAddressFactory, UserFactory
-from joanie.core.tasks.payment_schedule import debit_pending_installment
+from joanie.core.factories import (
+    OrderFactory,
+    OrderGeneratorFactory,
+    UserAddressFactory,
+    UserFactory,
+)
+from joanie.core.tasks.payment_schedule import (
+    debit_pending_installment,
+    send_mail_reminder_installment_debit_task,
+)
 from joanie.payment import get_payment_backend
 from joanie.payment.backends.dummy import DummyPaymentBackend
 from joanie.payment.factories import InvoiceFactory
@@ -320,3 +333,119 @@ def test_utils_payment_schedule_should_catch_up_late_payments_for_installments_s
                 },
             ],
         )
+
+    @override_settings(
+        JOANIE_PAYMENT_SCHEDULE_LIMITS={
+            5: (30, 70),
+        },
+        JOANIE_INSTALLMENT_REMINDER_PERIOD_DAYS=2,
+        DEFAULT_CURRENCY="EUR",
+    )
+    def test_payment_scheduled_send_mail_reminder_installment_debit_task_full_cycle(
+        self,
+    ):
+        """
+        According to the value configured in the setting `JOANIE_INSTALLMENT_REMINDER_PERIOD_DAYS`,
+        that is 2 days for this test, the command should find the orders that must be treated
+        and calls the method responsible to send the reminder email to the owner orders.
+        """
+        owner_1 = UserFactory(
+            first_name="John",
+            last_name="Doe",
+            email="[email protected]",
+            language="fr-fr",
+        )
+        UserAddressFactory(owner=owner_1)
+        owner_2 = UserFactory(
+            first_name="Sam", last_name="Doe", email="[email protected]", language="fr-fr"
+        )
+        UserAddressFactory(owner=owner_2)
+        order_1 = OrderGeneratorFactory(
+            owner=owner_1,
+            state=ORDER_STATE_PENDING_PAYMENT,
+            product__price=D("5"),
+            product__title="Product 1",
+        )
+        order_1.payment_schedule[0]["state"] = PAYMENT_STATE_PAID
+        order_1.payment_schedule[0]["due_date"] = date(2024, 1, 17)
+        order_1.payment_schedule[1]["id"] = "1932fbc5-d971-48aa-8fee-6d637c3154a5"
+        order_1.payment_schedule[1]["due_date"] = date(2024, 2, 17)
+        order_1.payment_schedule[1]["state"] = PAYMENT_STATE_PENDING
+        order_1.save()
+        order_2 = OrderGeneratorFactory(
+            owner=owner_2,
+            state=ORDER_STATE_PENDING_PAYMENT,
+            product__price=D("5"),
+            product__title="Product 2",
+        )
+        order_2.payment_schedule[0]["state"] = PAYMENT_STATE_PAID
+        order_2.payment_schedule[1]["id"] = "a1cf9f39-594f-4528-a657-a0b9018b90ad"
+        order_2.payment_schedule[1]["due_date"] = date(2024, 2, 17)
+        order_2.save()
+        # This order should be ignored by the django command `send_mail_upcoming_debit`
+        order_3 = OrderGeneratorFactory(
+            state=ORDER_STATE_PENDING_PAYMENT,
+            product__price=D("5"),
+            product__title="Product 2",
+        )
+        order_3.payment_schedule[0]["state"] = PAYMENT_STATE_PAID
+        order_3.payment_schedule[1]["due_date"] = date(2024, 2, 18)
+        order_3.save()
+
+        # Orders that should be found with their installment that will be debited soon
+        expected_calls = [
+            mock.call.delay(
+                order_id=order_2.id,
+                installment_id="a1cf9f39-594f-4528-a657-a0b9018b90ad",
+            ),
+            mock.call.delay(
+                order_id=order_1.id,
+                installment_id="1932fbc5-d971-48aa-8fee-6d637c3154a5",
+            ),
+        ]
+
+        with (
+            mock.patch(
+                "django.utils.timezone.localdate", return_value=date(2024, 2, 15)
+            ),
+            mock.patch(
+                "joanie.core.tasks.payment_schedule.send_mail_reminder_installment_debit_task"
+            ) as mock_send_mail_reminder_installment_debit_task,
+        ):
+            call_command("send_mail_upcoming_debit")
+
+        mock_send_mail_reminder_installment_debit_task.assert_has_calls(
+            expected_calls, any_order=False
+        )
+
+        # Trigger now the task `send_mail_reminder_installment_debit_task` for order_1
+        send_mail_reminder_installment_debit_task.run(
+            order_id=order_1.id, installment_id=order_1.payment_schedule[1]["id"]
+        )
+
+        # Check if mail was sent to owner_1 about next upcoming debit
+        self.assertEqual(mail.outbox[0].to[0], "[email protected]")
+        self.assertIn("will be debited in 2 days.", mail.outbox[0].subject)
+        email_content_1 = " ".join(mail.outbox[0].body.split())
+        fullname_1 = order_1.owner.get_full_name()
+        self.assertIn(f"Hello {fullname_1}", email_content_1)
+        self.assertIn("installment will be withdrawn on 2 days", email_content_1)
+        self.assertIn("We will try to debit an amount of", email_content_1)
+        self.assertIn("3,5", email_content_1)
+        self.assertIn("Product 1", email_content_1)
+
+        # Trigger now the task `send_mail_reminder_installment_debit_task` for order_2
+        send_mail_reminder_installment_debit_task.run(
+            order_id=order_2.id, installment_id=order_2.payment_schedule[1]["id"]
+        )
+
+        # Check if mail was sent to owner_2 about next upcoming debit
+        self.assertEqual(mail.outbox[1].to[0], "[email protected]")
+        self.assertIn("will be debited in 2 days.", mail.outbox[1].subject)
+        fullname_2 = order_2.owner.get_full_name()
+        email_content_2 = " ".join(mail.outbox[1].body.split())
+        self.assertIn(f"Hello {fullname_2}", email_content_2)
+        self.assertIn("installment will be withdrawn on 2 days", email_content_2)
+        self.assertIn("We will try to debit an amount of", email_content_2)
+        self.assertIn("1,5", email_content_2)
+        self.assertIn("Product 2", email_content_2)