import '../domain/course_occurrence.dart'; class DeviceCalendar { const DeviceCalendar(this.id, this.name); final String id, name; } abstract class CalendarService { Future requestAccess(); Future> listWritableCalendars(); Future> sync( List occurrences, String calendarId, Map knownEventIds, ); Future deleteOwned(Map eventIds); Future> ownedEventIds(String calendarId) async => const {}; }