from typing import Type, Union

from google.protobuf.pyext._message import Message

from delphi_api.bigtable import BigTableAttribute, ProtoAttribute


def apply_dynamic_fields(names: iter, column_family: str,
                         field_class: Union[Type[BigTableAttribute], ProtoAttribute],
                         deserialize_class: Union[Type[Message], Message]) -> callable:
    """Class decorator. Used for adding (many) protobuf type fields dynamically to a model.

    Args:
        names: Field names to add
        column_family: BigTable column family ID (name)
        field_class: Class reference for the model column type.
                     Currently only types of :class:`BigTableAttribute` are supported
        deserialize_class: Class type for the protobuf deserialization

    Returns:
        decorated class
    """

    def class_decorator(cls) -> object:
        for name in names:
            setattr(cls, name,
                    field_class(column_family=column_family,
                                attr_name=name, deserialize_class=deserialize_class))
        return cls

    return class_decorator