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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 import schema as bsc
from bsfs.query import ast
from bsfs.utils import errors
# inner-module imports
from . import nodes
# exports
__all__: typing.Sequence[str] = (
'Filter',
)
## code ##
class Filter():
"""Rewrites the query to replace `bsfs.graph.nodes.Nodes` instances with the respective URI.
Does only limited type checking and schema validation.
Use `bsfs.schema.validate.Filter` to do so.
Example:
input: Any(ns.bse.tag, Is(Nodes(...)))
output: Any(ns.bse.tag, Or(Is(...), Is(...), ...)))
>>> tags = graph.node(ns.bsfs.Tag, 'http://example.com/me/tag#1234')
>>> graph.get(ns.bsfs.Entity, ast.filter.Any(ns.bse.tag, ast.filter.Is(tags)))
"""
def __init__(self, schema):
self.schema = schema
def __call__(self, root_type: bsc.Node, node: ast.filter.FilterExpression):
return self._parse_filter_expression(root_type, node)
def _parse_filter_expression(
self,
type_: bsc.Vertex,
node: ast.filter.FilterExpression,
) -> ast.filter.FilterExpression:
"""Route *node* to the handler of the respective FilterExpression subclass."""
if isinstance(node, ast.filter.Is):
return self._is(type_, node)
if isinstance(node, ast.filter.Not):
return self._not(type_, node)
if isinstance(node, ast.filter.Has):
return self._has(type_, node)
if isinstance(node, ast.filter.Any):
return self._any(type_, node)
if isinstance(node, ast.filter.All):
return self._all(type_, node)
if isinstance(node, ast.filter.And):
return self._and(type_, node)
if isinstance(node, ast.filter.Or):
return self._or(type_, node)
if isinstance(node, (ast.filter.Equals, ast.filter.Substring, \
ast.filter.StartsWith, ast.filter.EndsWith)):
return self._value(type_, node)
if isinstance(node, (ast.filter.LessThan, ast.filter.GreaterThan)):
return self._bounded(type_, node)
# invalid node
raise errors.BackendError(f'expected filter expression, found {node}')
def _parse_predicate_expression(self, node: ast.filter.PredicateExpression) -> bsc.Vertex:
"""Route *node* to the handler of the respective PredicateExpression subclass."""
if isinstance(node, ast.filter.Predicate):
return self._predicate(node)
if isinstance(node, ast.filter.OneOf):
return self._one_of(node)
# invalid node
raise errors.BackendError(f'expected predicate expression, found {node}')
def _predicate(self, node: ast.filter.Predicate) -> bsc.Vertex:
if not self.schema.has_predicate(node.predicate):
raise errors.ConsistencyError(f'predicate {node.predicate} is not in the schema')
pred = self.schema.predicate(node.predicate)
dom, rng = pred.domain, pred.range
if node.reverse:
dom, rng = rng, dom
return rng
def _one_of(self, node: ast.filter.OneOf) -> bsc.Vertex:
# determine domain and range types
rng = None
for pred in node:
# parse child expression
subrng = self._parse_predicate_expression(pred)
# determine the next type
try:
if rng is None or subrng > rng: # pick most generic range
rng = subrng
except TypeError as err:
raise errors.ConsistencyError(f'ranges {subrng} and {rng} are not related') from err
if not isinstance(rng, (bsc.Node, bsc.Literal)):
raise errors.BackendError(f'the range of node {node} is undefined')
return rng
def _any(self, type_: bsc.Vertex, node: ast.filter.Any) -> ast.filter.Any: # pylint: disable=unused-argument
next_type = self._parse_predicate_expression(node.predicate)
return ast.filter.Any(node.predicate, self._parse_filter_expression(next_type, node.expr))
def _all(self, type_: bsc.Vertex, node: ast.filter.All) -> ast.filter.All: # pylint: disable=unused-argument
next_type = self._parse_predicate_expression(node.predicate)
return ast.filter.All(node.predicate, self._parse_filter_expression(next_type, node.expr))
def _and(self, type_: bsc.Vertex, node: ast.filter.And) -> ast.filter.And:
return ast.filter.And({self._parse_filter_expression(type_, expr) for expr in node})
def _or(self, type_: bsc.Vertex, node: ast.filter.Or) -> ast.filter.Or:
return ast.filter.Or({self._parse_filter_expression(type_, expr) for expr in node})
def _not(self, type_: bsc.Vertex, node: ast.filter.Not) -> ast.filter.Not:
return ast.filter.Not(self._parse_filter_expression(type_, node.expr))
def _has(self, type_: bsc.Vertex, node: ast.filter.Has) -> ast.filter.Has: # pylint: disable=unused-argument
return node
def _value(self, type_: bsc.Vertex, node: ast.filter._Value) -> ast.filter._Value: # pylint: disable=unused-argument
return node
def _bounded(self, type_: bsc.Vertex, node: ast.filter._Bounded) -> ast.filter._Bounded: # pylint: disable=unused-argument
return node
def _is(self, type_: bsc.Vertex, node: ast.filter.Is) -> typing.Union[ast.filter.Or, ast.filter.Is]:
# check if action is needed
if not isinstance(node.value, nodes.Nodes):
return node
# check schema consistency
if node.value.node_type not in self.schema.nodes():
raise errors.ConsistencyError(f'node {node.value.node_type} is not in the schema')
# check type compatibility
if not isinstance(type_, bsc.Node):
raise errors.ConsistencyError(f'expected a node, found {type_}')
if not node.value.node_type <= type_:
raise errors.ConsistencyError(f'expected type {type_} or subtype thereof, found {node.value.node_type}')
# NOTE: We assume that the node type is checked when writing to the backend.
# Links to any of the guids can therefore only exist if the type matches.
# Hence, we don't add a type check/constrain here.
return ast.filter.Or(ast.filter.Is(guid) for guid in node.value.guids)
# optimized code, removing unnecessary ast.filter.Or
#guids = set(node.value.guids)
#if len(guids) == 0:
# raise errors.BackendError(f'')
#if len(guids) == 1:
# return ast.filter.Nodeid(next(iter(guids)))
#return ast.filter.Or(ast.filter.Is(guid) for guid in guids)
## EOF ##
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