class Fact(object):
    def __init__(self, kind):
        self._kind = kind
        self._domains = {}

    @property
    def kind() -> str:
        return self._kind

    def attr(self, domain: str, key: str):
        try:
            return self._domains[domain][key]
        except KeyError:
            pass

    def set(self, domain: str, key: str, value: str):
        _kv(domain)[key] = value

    def _kv(self, domain: str):
        try:
            kv = self._domains[domain]
        except KeyError:
            kv = {}
            self._domains[domain] = kv

        return kv

    def view(self, domain: str):
        return FactKv(self, domain, self._kv(domain))

    def write(self, output):
        import configparser
        ini = configparser.ConfigParser(interpolation = None)
        for domain, kv in self._domains.items():
            ini.add_section(domain)
            for key, value in kv.items():
                ini.set(domain, key, value)

        ini.write(output)


class FactKv(object):
    def __init__(self, fact, domain, kv):
        self._fact = fact
        self._domain = domain
        self._kv = kv

    def set(self, key, value):
        self._kv[key] = value