import abc


class DataCollector(object, metaclass=abc.ABCMeta):
    def end_epoch(self, epoch):
        pass

    def get_diagnostics(self):
        return {}

    def get_snapshot(self):
        return {}

    @abc.abstractmethod
    def get_epoch_paths(self):
        pass


class PathCollector(DataCollector, metaclass=abc.ABCMeta):
    @abc.abstractmethod
    def collect_new_paths(self, max_path_length, num_steps, discard_incomplete_paths):
        pass


class StepCollector(DataCollector, metaclass=abc.ABCMeta):
    @abc.abstractmethod
    def collect_new_steps(self, max_path_length, num_steps, discard_incomplete_paths):
        pass
