import abc

class Backend(object):

    @abc.abstractmethod
    def filter_tasks(self, filter_obj):
        """Returns a list of Task objects matching the given filter"""
        pass

    @abc.abstractmethod
    def save_task(self, task):
        pass

    @abc.abstractmethod
    def delete_task(self, task):
        pass

    @abc.abstractmethod
    def start_task(self, task):
        pass

    @abc.abstractmethod
    def stop_task(self, task):
        pass

    @abc.abstractmethod
    def sync(self):
        """Syncs the backend database with the taskd server"""
        pass