from pathlib import Path
from typing import Union, List, Optional


class GenericText:
    def __init__(self, content: Union[List[str], Path]):
        if isinstance(content, List):
            self._content: Optional[List[str]] = content
            self._path = None
        else:
            self._content: Optional[List[str]] = None
            self._path = content

    @property
    def text(self) -> List[str]:
        if self._content is None:
            try:
                with open(self._path, 'r') as file:
                    self._content = file.readlines()
            except FileNotFoundError:
                raise NotImplementedError
            except:
                raise NotImplementedError
        return self._content

    @text.setter
    def text(self, content: Union[List[str], Path]) -> None:
        if isinstance(content, List):
            self._content = content
            self._path = None
        else:
            self._content = None
            self._path = content

    def format(self, **kwargs) -> str:
        for line in self._content:
            try:
                line = line.format(**kwargs)
            except ValueError:
                raise NotImplementedError
        return '\n'.join(self._content)

    def __add__(self, other):
        if isinstance(other, GenericText):
            return GenericText(self.text + other.text)
        else:
            return GenericText(self.text + other)

    def __iadd__(self, other):
        self.text = self + other