"""Utilities for handling privileges."""
from typing import Union, Sequence, TypeAlias

Operator: TypeAlias = str # Valid operators: "AND", "OR"
Privilege: TypeAlias = str
PrivilegesList: TypeAlias = Sequence[Privilege]
ParseTree = tuple[Operator,
                  # Leaves (`PrivilegesList` objects) on the left,
                  # trees (`ParseTree` objects) on the right
                  Union[PrivilegesList, tuple[PrivilegesList, 'ParseTree']]]


class SpecificationValueError(ValueError):
    """Raised when there is an error in the specification string."""
    pass


def parse(spec: str) -> ParseTree:
    """Parse a string specification for privileges and return a tree of data
    objects of the form (<operator> (<check>))"""
    # if(spec.strip() == ""):
    #     raise SpecificationValueError(
    #         "You passed an empty specification. I do not know what to do.")

    return tuple()


def check(spec: str, privileges: tuple[str, ...]) -> bool:
    """Check that the sequence of `privileges` satisfies `spec`."""
    return False