New endpoint to return a summary of returned letters for the service.

app/dao/returned_letters_dao.py

@@ -1,5 +1,6 @@
 from datetime import datetime
 
+from sqlalchemy import func, desc
 from sqlalchemy.dialects.postgresql import insert
 
 from app import db
@@ -7,6 +8,19 @@ from app.dao.dao_utils import transactional
 from app.models import Notification, NotificationHistory, ReturnedLetter
 
 
+
+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
+
+
 @transactional
 def insert_or_update_returned_letters(references):
     data = _get_notification_ids_for_references(references)
@@ -28,13 +42,14 @@ def insert_or_update_returned_letters(references):
         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)
+def get_returned_letter_summary(service_id):
+    return db.session.query(
+        func.count(ReturnedLetter.notification_id).label('returned_letter_count'),
+        ReturnedLetter.reported_at
+    ).filter(
+        ReturnedLetter.service_id == service_id,
+    ).group_by(
+        ReturnedLetter.reported_at
+    ).order_by(
+        desc(ReturnedLetter.reported_at)
     ).all()
-
-    notification_history_ids = db.session.query(NotificationHistory.id, NotificationHistory.service_id).filter(
-        NotificationHistory.reference.in_(references)
-    ).all()
-
-    return notification_ids + notification_history_ids