Platformer 2.0

common/state_machine.gd

@@ -0,0 +1,71 @@
+extends RefCounted
+class_name StateMachine
+
+const MIN_PRIORITY = -2147483648
+
+signal state_changed(f_id: StringName, t_id: StringName)
+
+var states: Dictionary[StringName, State] = {}
+var transitions: Array[StateTransition] = []
+var current_state: State
+
+var _pending_id: StringName = &""
+var _pending_priority = MIN_PRIORITY
+
+func setup(state_list: Array[State], transition_list: Array[StateTransition], initial_id: StringName) -> void:
+	states.clear()
+	for s in state_list:
+		if s != null:
+			states[s.id] = s
+	
+	transitions = transition_list
+
+	current_state = states.get(initial_id)
+	if current_state == null and not states.is_empty():
+		current_state = states.values()[0]
+		push_warning("State machine initial state '%s' not found, falling back to '%s'" % [initial_id, current_state.id])
+
+func process(data: Object, delta: float) -> void:
+	if current_state == null:
+		return
+
+	current_state.process(data, delta)
+	_evaluate_transitions(data)
+
+# Escape hatch for an immediate transition
+func request_transition(to_id: StringName, priority: int = 999) -> void:
+	if priority >= _pending_priority:
+		_pending_id = to_id
+		_pending_priority = priority
+
+func _evaluate_transitions(data: Object) -> void:
+	var best_id: StringName = &""
+	var best_priority: int = MIN_PRIORITY
+
+	# Is there a next state pending that isn't our current state?
+	if _pending_id != &"" and _pending_id != current_state.id and states.has(_pending_id):
+		best_id = _pending_id
+		best_priority = _pending_priority
+	
+	for t in transitions:
+		# Skip the current state
+		if not t.matches_current(current_state.id) or t.to == current_state.id:
+			continue
+		if not states.has(t.to):
+			push_warning("StateMachine: transition targets unknown state '%s'" % t.to)
+			continue
+		if t.priority < best_priority:
+			continue
+		if t.is_satisfied(data):
+			best_id = t.to
+			best_priority = t.priority
+	
+	_pending_id = &""
+	_pending_priority = MIN_PRIORITY
+
+	if best_id != &"" and best_id != current_state.id:
+		var from_id = current_state.id
+		current_state.exit(data)
+		current_state = states[best_id]
+		current_state.enter(data)
+		state_changed.emit(from_id, current_state.id)