import types

class message:
    def __init__(self, default: dict, sections: dict) -> None:
        sections_proxy = dict()

        for key, value in sections.items():
            sections_proxy[key] = types.MappingProxyType(value)

        self.__sections = types.MappingProxyType(sections_proxy)
        self.__default = types.MappingProxyType(default)

    def get_key(self, key: str, section: str | None = None) -> str:
        if section is None:
            return self.get_from_default(key)

        return self.get_from_section(section, key)

    def get_from_default(self, key: str) -> any:
        return self.__default[key]

    def get_from_section(self, section: str, key: str) -> any:
        return self.__sections[section][key]

    @property
    def default(self) -> types.MappingProxyType:
        return self.__default

    @property
    def sections(self) -> types.MappingProxyType:
        return self.__sections

class message_builder:
    def __init__(self) -> None:
        self.__sections = dict()
        self.__default = dict()

    def __add_section(self, section: str) -> object:
        if not section in self.__sections.keys():
            self.__sections[section] = dict()

    def __set_section_key(self, section: str, key: str, value: str) -> None:
        self.__sections[section][key] = value

    def __set_default_key(self, key: str, value: str) -> None:
        self.__default[key] = value

    def set_key(
        self, 
        key: str, 
        value: str, 
        section: str | None = None
    ) -> object:
        key = key.strip()
        value = value.strip()

        if len(key) == 0:
            raise RuntimeError("Key nam can nob being empty.")

        if section is None:
            self.__set_default_key(key, value)
            return self

        section = section.strip()
        
        if len(section) == 0:
            raise RuntimeError("Section name can not being empty.")

        self.__add_section(section)
        self.__set_section_key(section, key, value)

        return self

    def build(self) -> message:
        return message(self.__default, self.__sections)