refactor to state machine

scripts/states/state_machine.gd

@@ -0,0 +1,51 @@
+extends Node
+
+@export var current_state: State
+var subject: Node
+
+func set_subject(new_subject: Node) -> void:
+	subject = new_subject
+	for state in get_children():
+		state.subject = subject
+
+func _change_state(new_state: State) -> void:
+	if current_state:
+		#print("Exiting: %s" % current_state.name)
+		current_state.exit()
+
+	current_state = new_state
+	print("Entering: %s" % current_state.name)
+	current_state.enter()
+
+func process_physics(delta: float) -> void:
+	if not current_state:
+		return
+
+	if not current_state.subject:
+		return
+
+	var new_state = current_state.process_physics(delta)
+	if new_state:
+		_change_state(new_state)
+
+func process_input(event: InputEvent) -> void:
+	if not current_state:
+		return
+
+	if not current_state.subject:
+		return
+
+	var new_state = current_state.process_input(event)
+	if new_state:
+		_change_state(new_state)
+
+func process_frame(delta: float) -> void:
+	if not current_state:
+		return
+
+	if not current_state.subject:
+		return
+
+	var new_state = current_state.process_frame(delta)
+	if new_state:
+		_change_state(new_state)