class Buzzer:
    def __init__(self, pin=None):
        self.pin = pin
        self.enabled = False
        self.pattern = None

    def on(self):
        self.enabled = True
        if self.pin:
            self.pin.value(1)

    def off(self):
        self.enabled = False
        self.pattern = None
        if self.pin:
            self.pin.value(0)

    def set_pattern(self, pattern):
        self.pattern = pattern
        self.enabled = pattern is not None

    def update_from_alarm_view(self, alarm_view):
        if alarm_view.should_buzz():
            self.set_pattern("critical")
        else:
            self.off()