Merge branch 'develop'v0.23.03

1 files changed, 174 insertions, 0 deletions

diff --git a/bsfs/graph/resolve.py b/bsfs/graph/resolve.py
new file mode 100644
index 0000000..a58eb67
--- /dev/null
+++ b/bsfs/graph/resolve.py
@@ -0,0 +1,174 @@
+
+# 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.bsn.Tag, 'http://example.com/me/tag#1234')
+    >>> graph.get(ns.bsn.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: typing.Optional[ast.filter.FilterExpression],
+            ):
+        """Alias for `Resolve.resolve`."""
+        return self.resolve(root_type, node)
+
+    def resolve(
+            self,
+            root_type: bsc.Node,
+            node: typing.Optional[ast.filter.FilterExpression],
+            ):
+        """Resolve Nodes instances of a *node* query starting at *root_type*."""
+        if node is None:
+            return None
+        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.Distance):
+            return self._distance(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
+            if rng is None or subrng > rng: # pick most generic range
+                rng = subrng
+            # check range consistency
+            if not subrng <= rng and not subrng >= rng:
+                raise errors.ConsistencyError(f'ranges {subrng} and {rng} are not related')
+        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 _distance(self, type_: bsc.Vertex, node: ast.filter.Distance): # 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 ##