refactor: update fallback event, improve type info

src/aura_engine/engine.py

@@ -48,6 +48,8 @@ from aura_engine.resources import (
     ResourceUtil,
 )
 from aura_engine.scheduling.domain import PlaylistItem
+from aura_engine.scheduling.scheduler import AuraScheduler
+from aura_engine.scheduling.timetable import TimetableService
 
 
 class Engine:
@@ -59,7 +61,7 @@ class Engine:
     logger: logging.Logger
     config: confuse.Configuration
     engine_time_offset = 0.0
-    scheduler = None
+    scheduler: AuraScheduler = None
     event_dispatcher = None
     client = None
     playout = None
@@ -144,9 +146,9 @@ class Engine:
         state = DotDict(LU.json_to_dict(state))
 
         def dispatch_fallback_event():
-            timeslot = self.scheduler.timetable.get_current_timeslot()
-            fallback_show_name = self.config.general.fallback_show_name
-            self.event_dispatcher.on_fallback_active(timeslot, fallback_show_name)
+            timetable: TimetableService = self.scheduler.get_timetable()
+            timeslot = timetable.get_current_timeslot()
+            self.event_dispatcher.on_fallback_active(timeslot)
 
         # Initialize state
         if not self.playout_state:

src/aura_engine/events.py

@@ -239,18 +239,26 @@ class EngineEventDispatcher:
         thread = Thread(target=func, args=(self, channel))
         thread.start()
 
-    def on_fallback_active(self, timeslot, fallback_name):
+    def on_fallback_active(self, timeslot):
         """
-        Call when a fallback is activated for the given timeslot.
+        Call when a fallback is activated.
 
-        This means there is no proper playlist scheduled.
+        Fallback means the station fallback audio source is played when:
+            1. no timeslot is available.
+            2. the current timefrome of the active timeslot provides no audio source/playlists.
+
+        TODO In the future case (1) should technically not happen, as "Virtual Timeslots" ensure
+        there is always some timeslot available, even without any playlists/media sources assigned.
+
+        Args:
+            timeslot (Timeslot): The active timeslot, if available. Can be `None`.
         """
 
-        def func(self, timeslot, fallback_type):
+        def func(self, timeslot):
             self.logger.debug("on_fallback_active(..)")
-            self.call_event("on_fallback_active", timeslot, fallback_type)
+            self.call_event("on_fallback_active", timeslot)
 
-        thread = Thread(target=func, args=(self, timeslot, fallback_name))
+        thread = Thread(target=func, args=(self, timeslot))
         thread.start()
 
     def on_queue(self, items: list):