send mail to inactive users

counter/management/commands/dump_warning_mail.py

@@ -0,0 +1,88 @@
+import logging
+from smtplib import SMTPException
+
+from django.conf import settings
+from django.core.mail import send_mail
+from django.core.management.base import BaseCommand
+from django.db.models import Exists, OuterRef, Subquery
+from django.template.loader import render_to_string
+from django.utils.timezone import localdate, now
+from django.utils.translation import gettext as _
+
+from core.models import User
+from counter.models import AccountDump
+from subscription.models import Subscription
+
+
+class Command(BaseCommand):
+    """Send mail to inactive users, warning them that their account is about to be dumped.
+
+    This command should be automated with a cron task.
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.logger = logging.getLogger("account_dump_mail")
+        self.logger.setLevel(logging.INFO)
+        super().__init__(*args, **kwargs)
+
+    def handle(self, *args, **options):
+        ongoing_dump_operation = AccountDump.objects.ongoing().filter(
+            customer__user=OuterRef("pk")
+        )
+        users = list(
+            User.objects
+            .filter_inactive()
+            .filter(customer__amount__gt=0)
+            .exclude(Exists(ongoing_dump_operation))
+            .annotate(
+                last_subscription_date=Subquery(
+                    Subscription.objects.filter(member=OuterRef("pk"))
+                    .order_by("-subscription_end")
+                    .values("subscription_end")[:1]
+                ),
+            )
+            .select_related("customer")
+        )
+        self.stdout.write(f"{len(users)} users will be warned of their account dump")
+        dumps = []
+        for user in users:
+            is_success = self._send_mail(user)
+            dumps.append(
+                AccountDump(
+                    customer_id=user.id,
+                    warning_mail_sent_at=now(),
+                    warning_mail_error=not is_success,
+                )
+            )
+        AccountDump.objects.bulk_create(dumps)
+        self.stdout.write("Finished !")
+
+    def _send_mail(self, user: User) -> bool:
+        """Send the warning email to the given user.
+
+        Returns:
+            True if the mail was successfully sent, else False
+        """
+        message = render_to_string(
+            "counter/account_dump_warning_mail.jinja",
+            {
+                "balance": user.customer.amount,
+                "last_subscription_date": user.last_subscription_date,
+                "dump_date": localdate() + settings.SITH_ACCOUNT_DUMP_DELTA,
+            },
+        )
+        try:
+            # sending mails one by one is long and ineffective,
+            # but it makes easier to know which emails failed (and how).
+            # Also, there won't be that much mails sent (except on the first run)
+            send_mail(
+                _("Clearing of your AE account"),
+                message,
+                settings.DEFAULT_FROM_EMAIL,
+                [user.email],
+            )
+            self.logger.info(f"Mail successfully sent to {user.email}")
+            return True
+        except SMTPException as e:
+            self.logger.error(f"failed mail to {user.email} :\n{e}")
+            return False