Add announcements app

marietje/announcements/services.py

@@ -0,0 +1,33 @@
+import json
+import urllib.parse
+
+from announcements.models import Announcement
+
+
+def sanitize_closed_announcements(closed_announcements) -> list:
+    """Convert a cookie (closed_announcements) to a list of id's of closed announcements."""
+    if closed_announcements is None or not isinstance(closed_announcements, str):
+        return []
+    try:
+        closed_announcements_list = json.loads(urllib.parse.unquote(closed_announcements))
+    except json.JSONDecodeError:
+        return []
+
+    if not isinstance(closed_announcements_list, list):
+        return []
+
+    closed_announcements_list_ints = []
+    for closed_announcement in closed_announcements_list:
+        if isinstance(closed_announcement, int):
+            closed_announcements_list_ints.append(closed_announcement)
+    return closed_announcements_list_ints
+
+
+def validate_closed_announcements(closed_announcements) -> list:
+    """Verify the integers in the list such that the ID's that in the database exist only remain."""
+    return list(Announcement.objects.filter(id__in=closed_announcements).values_list("id", flat=True))
+
+
+def encode_closed_announcements(closed_announcements: list) -> str:
+    """Encode the announcement list in URL encoding."""
+    return urllib.parse.quote(json.dumps(closed_announcements))