import asyncio

class Timer():
    def __init__(self, minutes, seconds):
        self.minutes = minutes
        self.seconds = seconds
        self.ended = True

    def start(self):
        self.ended = False
        self.timer_task = asyncio.ensure_future(self.update())

    def stop(self):
        self.timer_task.cancel()
        self.endend = True

    async def update(self):
        while self.ended == False:
            await asyncio.sleep(1)
            if (self.minutes > 0 and self.seconds == 0):
                self.minutes -= 1
                self.seconds = 59
            elif (self.seconds > 0):
                self.seconds -= 1
                if (self.minutes == 0 and self.seconds == 0):
                    self.ended = True