factors/email(minor): start rebuilding email integration as factor

passbook/factors/email/tasks.py

@@ -0,0 +1,39 @@
+"""email factor tasks"""
+from smtplib import SMTPException
+from typing import Any, Dict, List
+
+from celery import group
+from django.core.mail import EmailMessage
+
+from passbook.factors.email.models import EmailFactor
+from passbook.root.celery import CELERY_APP
+
+
+def send_mails(factor: EmailFactor, *messages: List[EmailMessage]):
+    """Wrapper to convert EmailMessage to dict and send it from worker"""
+    tasks = []
+    for message in messages:
+        tasks.append(_send_mail_task.s(factor.pk, message.__dict__))
+    lazy_group = group(*tasks)
+    promise = lazy_group()
+    return promise
+
+@CELERY_APP.task(bind=True)
+def _send_mail_task(self, email_factor_pk: int, message: Dict[Any, Any]):
+    """Send E-Mail according to EmailFactor parameters from background worker.
+    Automatically retries if message couldn't be sent."""
+    factor: EmailFactor = EmailFactor.objects.get(pk=email_factor_pk)
+    backend = factor.backend
+    backend.open()
+    # Since django's EmailMessage objects are not JSON serialisable,
+    # we need to rebuild them from a dict
+    message_object = EmailMessage()
+    for key, value in message.items():
+        setattr(message_object, key, value)
+    message_object.from_email = factor.from_address
+    try:
+        num_sent = factor.backend.send_messages([message_object])
+    except SMTPException as exc:
+        raise self.retry(exc=exc)
+    if num_sent != 1:
+        raise self.retry()