Combine more holidays

Closes: #84

agenda/data.py

@@ -136,6 +136,17 @@ async def bristol_waste_collection_events(
 
 def combine_holidays(holidays: list[Holiday]) -> list[Event]:
     """Combine UK and US holidays with the same date and title."""
+
+    all_countries = {h.country for h in holidays}
+
+    standard_name = {
+        (1, 1): "New Year's Day",
+        (1, 6): "Epiphany",
+        (12, 8): "Immaculate conception",
+        (12, 25): "Christmas Day",
+        (12, 26): "Boxing Day",
+    }
+
     combined: collections.defaultdict[
         tuple[date, str], set[str]
     ] = collections.defaultdict(set)
@@ -143,12 +154,21 @@ def combine_holidays(holidays: list[Holiday]) -> list[Event]:
     for h in holidays:
         assert isinstance(h.name, str) and isinstance(h.date, date)
 
-        event_key = (h.date, h.name)
+        event_key = (h.date, standard_name.get((h.date.month, h.date.day), h.name))
         combined[event_key].add(h.country)
 
     events: list[Event] = []
     for (d, name), countries in combined.items():
-        title = f'{name} ({", ".join(country.upper() for country in countries)})'
+        if len(countries) == len(all_countries):
+            country_list = ""
+        elif len(countries) < len(all_countries) / 2:
+            country_list = ", ".join(sorted(country.upper() for country in countries))
+        else:
+            country_list = "not " + ", ".join(
+                sorted(country.upper() for country in all_countries - set(countries))
+            )
+
+        title = f"{name} ({country_list})"
         e = Event(name="holiday", date=d, title=title)
         events.append(e)