class Value:
	def __init__(self, initial=None):
		self.value = initial
		self.has_changed = True

	def set(self, value):
		self.has_changed = self.value != value
		self.value = value

	def is_changed(self):
		return self.has_changed

	def get(self):
		self.has_changed = False
		return self.value


class ChangedFloat(object):
	def __init__(self, on_changed, prec=2, initial=None):
		self.on_changed = on_changed
		self.prec = prec
		self.value = initial

	def set(self, value):
		has_changed = True
		value_rounded = round(value, self.prec)
		if self.value is not None:
			has_changed = self.value != value_rounded

		self.value = value_rounded
		if has_changed:
			self.on_changed(value_rounded)


class ChangedInteger(object):
	def __init__(self, on_changed, initial=None):
		self.on_changed = on_changed
		self.value = initial

	def set(self, value):
		value = round(value)
		has_changed = True
		if self.value is not None:
			has_changed = self.value != value

		self.value = value
		if has_changed:
			self.on_changed(value)


class AttributeChange(object):
	def __init__(self):
		self.callbacks = {}

	def set_on_changed(self, key, on_changed):
		if key not in self.callbacks:
			self.callbacks[key] = [on_changed]
		else:
			self.callbacks[key].append(on_changed)

	def __setattr__(self, key, value):
		try:
			old = super().__getattribute__(key)
		except:
			pass
		super().__setattr__(key, value)

		if key in self.callbacks:
			for cb in self.callbacks[key]:
				cb(value)