notifications.py

import datetime

class BaseNotification(object): 
    def to_dict(self, user, sent_at):
        return {
            'timestamp': datetime.time.mktime(sent_at.timetuple()),
        }

    def from_dict(self, data):
        self.timestamp = data['timestamp']
        self.sent_at = datetime.datetime.fromtimestamp(data['timestamp'])

    def get_display(self, user, backend):
        raise NotImplementedError()

class TextNotification(BaseNotification):
    def __init__(self, kwargs):
        self.text = kwargs.pop('text')
        self.kwargs = kwargs

    def to_dict(self, user, sent_at):
        data = super(TextNotification, self).to_dict(user, sent_at)
        data['text'] = self.text % self.kwargs
        return data

    def from_dict(self, data):
        super(TextNotification, self).from_dict(data)
        self.text = data['text']

    def get_display(self, user, backend):
        return self.text

class LazyTextNotification(TextNotification):
    def to_dict(self, user, sent_at):
        data = super(TextNotification, self).to_dict(user, sent_at)
        data['text'] = self.text
        data['kwargs'] = self.kwargs
        return  data
    
    def from_dict(self, data):
        super(LazyTextNotification, self).from_dict(data)
        self.kwargs = data['kwargs']

    def get_display(self, user, backend):
        return self.text % self.kwargs