Method to insert or update the returned-letters

app/dao/returned_letters_dao.py

@@ -0,0 +1,40 @@
+from datetime import datetime
+
+from sqlalchemy.dialects.postgresql import insert
+
+from app import db
+from app.dao.dao_utils import transactional
+from app.models import Notification, NotificationHistory, ReturnedLetter
+
+
+@transactional
+def insert_or_update_returned_letters(references):
+    data = _get_notification_ids_for_references(references)
+    now = datetime.utcnow()
+    for row in data:
+        table = ReturnedLetter.__table__
+
+        stmt = insert(table).values(
+            reported_at=now,
+            service_id=row.service_id,
+            notification_id=row.id)
+
+        stmt = stmt.on_conflict_do_update(
+            index_elements=[table.c.notification_id],
+            set_={
+                'reported_at': now,
+            }
+        )
+        db.session.connection().execute(stmt)
+
+
+def _get_notification_ids_for_references(references):
+    notification_ids = db.session.query(Notification.id, Notification.service_id).filter(
+        Notification.reference.in_(references)
+    ).all()
+
+    notification_history_ids = db.session.query(NotificationHistory.id, NotificationHistory.service_id).filter(
+        NotificationHistory.reference.in_(references)
+    ).all()
+
+    return notification_ids + notification_history_ids