Keep invalid datetimes at end of sort

app/services/processing.py

@@ -47,7 +47,7 @@ def sort_records(
     reverse = options.order == "desc"
 
     if options.sort_by == "datetime":
-        key_func = _datetime_key
+        return _sort_records_by_datetime(records, reverse)
     elif options.sort_by == "severity":
         key_func = _severity_key
     else:
@@ -56,17 +56,34 @@ def sort_records(
     return sorted(records, key=key_func, reverse=reverse)
 
 
-def _datetime_key(record: dict[str, str]) -> tuple[int, datetime]:
+def _sort_records_by_datetime(
+    records: Iterable[dict[str, str]], reverse: bool
+) -> list[dict[str, str]]:
+    """Sort valid datetimes normally and always place invalid/missing values last."""
+    valid_records: list[tuple[datetime, dict[str, str]]] = []
+    invalid_records: list[dict[str, str]] = []
+
+    for record in records:
+        parsed_datetime = _parse_datetime(record)
+        if parsed_datetime is None:
+            invalid_records.append(record)
+            continue
+        valid_records.append((parsed_datetime, record))
+
+    sorted_valid_records = sorted(valid_records, key=lambda item: item[0], reverse=reverse)
+    return [record for _parsed, record in sorted_valid_records] + invalid_records
+
+
+def _parse_datetime(record: dict[str, str]) -> datetime | None:
     date_value = record.get("v015xxxxdate", "").strip()
     time_value = record.get("time", "").strip()
     if not date_value or not time_value:
-        return (1, datetime.max)
+        return None
 
     try:
-        parsed = datetime.strptime(f"{date_value} {time_value}", "%Y-%m-%d %H:%M:%S")
+        return datetime.strptime(f"{date_value} {time_value}", "%Y-%m-%d %H:%M:%S")
     except ValueError:
-        return (1, datetime.max)
-    return (0, parsed)
+        return None
 
 
 def _severity_key(record: dict[str, str]) -> tuple[int, str]: