class TopicMessage():
    "Object containing both a topic and message string attribute. Can convert itself to a string representation"
    def __init__(self, topic:str = "", message:str = ""):
        self.topic = topic
        self.message = message
    def to_string(self) -> str:
        return f"{self.topic}: {self.message}"

class TMQueue():
    """Simple queue (FIFO) of TopicMessage objects"""
    def __init__(self):
        self.data: list[TopicMessage] = list()

    def get(self):
        if not self.is_empty():
            item = self.data.pop(0)
            return item
        else:
            raise IndexError

    def add(self, item):
        self.data.append(item)

    def is_empty(self):
        if len(self.data) == 0:
            return True
        else:
            return False

def string_to_topicmessage(s: str):
    """Convert string to a TopicMessage object"""
    topic, message = str.split(":", maxsplit = 1)
    return TopicMessage(topic, message)