added count option and sorting for artists

api/datasource.py

@@ -133,6 +133,33 @@ def sort_events(events: List[Event], sort: Optional[str]) -> List[Event]:
     return events
 
 
+def sort_artist_schedules(items, sort: Optional[str]):
+    """Sort (artist_name, dates) pairs per the ``?sort=`` query param.
+
+    "asc"/"desc" order by each artist's *latest* (most recent) date, since
+    an artist has many dates and not just one to sort on; artists with no
+    parseable date always sort last, regardless of direction. "az"/"za"
+    order alphabetically (case-insensitive) by name. None (or any other
+    value) defaults to "az", matching the plain-list behavior before sort
+    support existed.
+    """
+    items = list(items)
+    if sort in ("asc", "desc"):
+        def _latest(dates) -> Optional[date]:
+            parsed = [d for d in (parse_event_date(x) for x in dates) if d is not None]
+            return max(parsed) if parsed else None
+
+        with_latest = [(name, dates, _latest(dates)) for name, dates in items]
+        dated = sorted(
+            (item for item in with_latest if item[2] is not None),
+            key=lambda item: item[2],
+            reverse=(sort == "desc"),
+        )
+        undated = [(name, dates) for name, dates, latest in with_latest if latest is None]
+        return [(name, dates) for name, dates, _ in dated] + undated
+    return sorted(items, key=lambda item: item[0].lower(), reverse=(sort == "za"))
+
+
 def sort_date_strings(dates) -> List[str]:
     """Sort raw ``dd.mm.yy`` date strings chronologically, de-duplicated.