from typing import Generic, TypeVar

class UnwrapException(Exception):
    def __init__(self, *args: object) -> None:
        super().__init__(*args)

T = TypeVar("T")
E = TypeVar("E")

class Result(Generic[T, E]):
    def __init__(self) -> None:
        super().__init__()

    def ok(self) -> bool:
        raise NotImplementedError()

    def value(self) -> T:
        raise NotImplementedError()

    def error(self) -> E:
        raise NotImplementedError()

class Ok(Result[T, E]):
    def __init__(self, value: T) -> None:
        super().__init__()
        self.__value = value

    def ok(self) -> bool:
        return True

    def value(self) -> T:
        return self.__value

    def error(self) -> E:
        raise UnwrapException("cannot unwrap error of ok result")

class Err(Result[T, E]):
    def __init__(self, error: E) -> None:
        super().__init__()
        self.__error = error

    def ok(self) -> bool:
        return False

    def value(self) -> T:
        raise UnwrapException("cannot unwrap value of error result")

    def error(self) -> E:
        return self.__error

def unescape_string(value: str) -> Result[str, str]:
    result = ""
    i = 0
    while i < len(value):
        if value[i] == "\\":
            i += 1
            if i >= len(value):
                return Err("unescaped '\\'")
            elif value[i] == "0":
                result += "\0"
            elif value[i] == "n":
                result += "\n"
            elif value[i] == "t":
                result += "\t"
            elif value[i] == "r":
                result += "\r"
            else:
                result += value[i]
        else:
            result += value[i]
        i += 1
    return Ok(result)

def escape_string(value: str) -> str:
    result = ""
    for char in value:
        if char == "\0":
            result += "\\0"
        elif char == "\n":
            result += "\\n"
        elif char == "\t":
            result += "\\t"
        elif char == "\r":
            result += "\\r"
        elif char == "\"":
            result += "\\\""
        elif char == "\'":
            result += "\\'"
        elif char == "\\":
            result += "\\\\"
        else:
            result += char
    return result