Refactor rhythm action architecture

resources/chart_event.gd

@@ -0,0 +1,26 @@
+class_name ChartEvent
+extends Resource
+
+@export var event_id: StringName = &""
+@export var beat_index := 0
+@export var subdivision := 0
+@export var subdivisions_per_beat := 1
+@export var event_type: StringName = &""
+@export var target_id: StringName = &""
+@export var payload: Dictionary = {}
+@export var lead_beats := 1.0
+
+
+func beat_position() -> float:
+	var safe_subdivisions := maxi(1, subdivisions_per_beat)
+	return float(beat_index) + float(subdivision) / float(safe_subdivisions)
+
+
+func time_seconds(beat_time: float) -> float:
+	return beat_position() * maxf(0.001, beat_time)
+
+
+func key() -> StringName:
+	if not event_id.is_empty():
+		return event_id
+	return StringName("%s:%s:%d:%d" % [event_type, target_id, beat_index, subdivision])