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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 typing
# bsfs imports
from bsfs.utils import URI, typename
# exports
__all__: typing.Sequence[str] = (
'ClosedNamespace',
'Namespace',
)
## code ##
class Namespace():
"""A namespace consists of a common prefix that is used in a set of URIs.
Note that the prefix must include the separator between
path and fragment (typically a '#' or a '/').
"""
# namespace prefix.
prefix: URI
def __init__(self, prefix: URI):
self.prefix = URI(prefix)
def __eq__(self, other: typing.Any) -> bool:
return isinstance(other, type(self)) and self.prefix == other.prefix
def __hash__(self) -> int:
return hash((type(self), self.prefix))
def __str__(self) -> str:
return f'{typename(self)}({self.prefix})'
def __repr__(self) -> str:
return f'{typename(self)}({self.prefix})'
def __getattr__(self, fragment: str) -> URI:
"""Return prefix + fragment."""
return URI(self.prefix + fragment)
def __getitem__(self, fragment: str) -> URI:
"""Alias for getattr(self, fragment)."""
return self.__getattr__(fragment)
class ClosedNamespace(Namespace):
"""Namespace that covers a restricted set of URIs."""
# set of permissible fragments.
fragments: typing.Set[str]
def __init__(self, prefix: URI, *args: str):
super().__init__(prefix)
self.fragments = set(args)
def __eq__(self, other: typing.Any) -> bool:
return super().__eq__(other) and self.fragments == other.fragments
def __hash__(self) -> int:
return hash((type(self), self.prefix, tuple(sorted(self.fragments))))
def __getattr__(self, fragment: str) -> URI:
"""Return prefix + fragment.
Raises a KeyError if the fragment is not allowed in this namespace.
"""
if fragment not in self.fragments:
raise KeyError('fragment')
return super().__getattr__(fragment)
## EOF ##
|
