Add automatic cleanup for previously generated files

Unfortunately the UIDs of the downloaded icals change. To still catch
changes in the trash date schedule over the year, this makes sure to
delete all events with the same year as we're currently scraping.

generate_ical.py

@@ -77,6 +77,17 @@ for trash_type in trash_types:
   if not os.path.exists(trash_type_folder):
     os.makedirs(trash_type_folder)
 
+  for f in next(os.walk(trash_type_folder), (None, None, []))[2]:
+    ical_path = os.path.join(trash_type_folder, f)
+    with open(ical_path, "rb") as fh:
+      try:
+        cal = icalendar.Calendar.from_ical(fh.read())
+      except ValueError:
+        print("{} is not an parsable ical file".format(ical_path))
+        continue
+      if cal.walk()[1]["DTSTAMP"].dt.year == current_year:
+        os.remove(ical_path)
+
   radicale_prop_file = os.path.join(trash_type_folder, ".Radicale.props")
   with open(radicale_prop_file, "w") as f:
     f.write(json.dumps(radicale_props))
@@ -95,7 +106,7 @@ for trash_type in trash_types:
       new_cal.add('prodid', 'Trash dates')
       new_cal.add('version', '2.0')
       new_cal.add_component(event)
-      ical_name = "{}.ical".format(uid)
+      ical_name = "{}_{}.ical".format(current_year, uid)
       ical_path = os.path.join(trash_type_folder, ical_name)
       with open(ical_path, "wb") as single_file:
         single_file.write(new_cal.to_ical())