statemachine

extends Node2D

var states = {}

var state # current state

func _ready():
	states["one"] = StateOne.new()
	states["two"] = StateTwo.new()

	for s in states:
		states[s].connect("change_state_plz", self, "change_state")

    # set the initial state
	state = states["one"]
	set_process(true)

func _process(delta):
	state._process(delta)

func change_state(next_state):
	state = states[next_state]
    # maybe call a `unload` and `load` function on the states to show them that they are active now

class StateOne:
	signal change_state_plz(next_state)
	func _process(delta):
		print("DD")
		pass
class StateTwo:
	signal change_state_plz(next_state)
	func _process(delta):
		print("qq")
		pass



Not tested
but that's how I'd do it
You can then do emit_signal("name of next state")anywhere in a state to switch to a different state
since you can swap out state the call state._process(delta) will always call the function in the currently active state