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"""
Part of the BlackStar filesystem (bsfs) module.
A copy of the license is provided with the project.
Author: Matthias Baumgartner, 2022
"""
# imports
import abc
import typing
# bsfs imports
from bsfs import schema
from bsfs.query import ast
from bsfs.triple_store import TripleStoreBase
from bsfs.utils import URI, typename
# exports
__all__: typing.Sequence[str] = (
'AccessControlBase',
)
## code ##
class AccessControlBase(abc.ABC):
"""Defines the interface for access control policies.
An access control policy governs which actions a user may take to query
or to manipulate a graph.
"""
# The triple store backend.
_backend: TripleStoreBase
# The current user.
_user: URI
def __init__(
self,
backend: TripleStoreBase,
user: URI,
):
self._backend = backend
self._user = URI(user)
def __str__(self) -> str:
return f'{typename(self)}({self._user})'
def __repr__(self) -> str:
return f'{typename(self)}({self._user})'
def __eq__(self, other: typing.Any) -> bool:
return isinstance(other, type(self)) \
and self._backend == other._backend \
and self._user == other._user
def __hash__(self) -> int:
return hash((type(self), self._backend, self._user))
@abc.abstractmethod
def is_protected_predicate(self, pred: schema.Predicate) -> bool:
"""Return True if a predicate cannot be modified manually."""
@abc.abstractmethod
def create(self, node_type: schema.Node, guids: typing.Iterable[URI]):
"""Perform post-creation operations on nodes, e.g. ownership information."""
@abc.abstractmethod
def link_from_node(self, node_type: schema.Node, guids: typing.Iterable[URI]) -> typing.Iterable[URI]:
"""Return nodes for which outbound links can be written."""
@abc.abstractmethod
def link_to_node(self, node_type: schema.Node, guids: typing.Iterable[URI]) -> typing.Iterable[URI]:
"""Return nodes for which inbound links can be written."""
@abc.abstractmethod
def write_literal(self, node_type: schema.Node, guids: typing.Iterable[URI]) -> typing.Iterable[URI]:
"""Return nodes to which literals can be attached."""
@abc.abstractmethod
def createable(self, node_type: schema.Node, guids: typing.Iterable[URI]) -> typing.Iterable[URI]:
"""Return nodes that are allowed to be created."""
@abc.abstractmethod
def filter_read(
self,
node_type: schema.Node,
query: typing.Optional[ast.filter.FilterExpression],
) -> typing.Optional[ast.filter.FilterExpression]:
"""Re-write a filter *query* to get (i.e., read) *node_type* nodes."""
@abc.abstractmethod
def fetch_read(self, node_type: schema.Node, query: ast.fetch.FetchExpression) -> ast.fetch.FetchExpression:
"""Re-write a fetch *query* to get (i.e, read) values for *node_type* nodes."""
## EOF ##
|
