filter ast definition and validation

1 files changed, 176 insertions, 160 deletions

diff --git a/bsfs/query/validator.py b/bsfs/query/validator.py
index 123b947..352203a 100644
--- a/bsfs/query/validator.py
+++ b/bsfs/query/validator.py
@@ -9,6 +9,8 @@ import typing
 
 # bsfs imports
 from bsfs import schema as bsc
+from bsfs.namespace import ns
+from bsfs.utils import errors, typename
 
 # inner-module imports
 from . import ast
@@ -22,6 +24,18 @@ __all__ : typing.Sequence[str] = (
 ## code ##
 
 class Filter():
+    """Validate a `bsfs.query.ast.filter` query's structure and schema compliance.
+
+    * Conditions (Bounded, Value) can only be applied on literals
+    * Branches, Id, and Has can only be applied on nodes
+    * Predicates' domain and range must match
+    * Predicate paths must follow the schema
+    * Referenced types are present in the schema
+
+    """
+
+    # vertex types
+    T_VERTEX = typing.Union[bsc.Node, bsc.Literal] # FIXME: Shouldn't this be in the schema?
 
     # schema to validate against.
     schema: bsc.Schema
@@ -29,180 +43,182 @@ class Filter():
     def __init__(self, schema: bsc.Schema):
         self.schema = schema
 
-    def parse(self, node: ast.filter.FilterExpression, subject: bsc.types._Vertex):
-        # subject is a node type
-        if not isinstance(subject, bsc.Node):
-            raise errors.ConsistencyError(f'Expected a node, found {subject}')
-        # subject exists in the schema
-        if subject not in self.schema.nodes:
-            raise errors.ConsistencyError(f'Invalid node type {subject}')
-        # root expression is valid
-        self._parse(node, subject)
+    def __call__(self, root_type: bsc.Node, query: ast.filter.FilterExpression):
+        """Validate a filter *query*, assuming the subject having *root_type*.
+
+        Raises a `bsfs.utils.errors.ConsistencyError` if the query violates the schema.
+        Raises a `bsfs.utils.errors.BackendError` if the query structure is invalid.
+
+        """
+        # root_type must be a schema.Node
+        if not isinstance(root_type, bsc.Node):
+            raise TypeError(f'Expected a node, found {typename(root_type)}')
+        # root_type must exist in the schema
+        if root_type not in self.schema.nodes():
+            raise errors.ConsistencyError(f'{root_type} is not defined in the schema')
+        # check root expression
+        self._parse_filter_expression(root_type, query)
         # all tests passed
         return True
 
 
-    def _parse_numerical_expression(self, node: ast.filter.FilterExpression, subject: bsc.types._Vertex):
-        if isinstance(node, ast.filter.And):
-            return self._and(node, subject)
-        elif isinstance(node, ast.filter.Or):
-            return self._or(node, subject)
-        elif isinstance(node, ast.filter.LessThan):
-            return self._lessThan(node, subject)
-        elif isinstance(node, ast.filter.GreaterThan):
-            return self._greaterThan(node, subject)
-        elif isinstance(node, ast.filter.Equals):
-            return self._equals(node, subject, numerical=True)
-        else:
-            raise errors.ConsistencyError(f'Expected a numerical expression, found {node}')
-
-
-    def __branch(self, node: typing.Union[ast.filter.Any, ast.filter.And], subject: bsc.types._Vertex):
-        # subject is a node type
-        if not isinstance(subject, bsc.Node):
-            raise errors.ConsistencyError(f'Expected a node, found {subject}')
-        # subject exists in the schema
-        if subject not in self.schema.nodes:
-            raise errors.ConsistencyError(f'Invalid node type {subject}')
-        # predicate is valid
-        dom, rng = self._parse_predicate_expression(node.predicate)
-        # subject is a subtype of the predicate's domain
-        if not subject <= dom:
-            raise errors.ConsistencyError(f'Expected type {dom}, found {subject}')
-        # child expression is valid
-        self._parse_filter_expression(node.expr, rng)
+    ## routing methods
+
+    def _parse_filter_expression(self, type_: T_VERTEX, node: 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, ast.filter.All)):
+            return self._branch(type_, node)
+        if isinstance(node, (ast.filter.And, ast.filter.Or)):
+            return self._agg(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) -> typing.Tuple[T_VERTEX, T_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}')
+
+
+    ## predicate expressions
+
+    def _predicate(self, node: ast.filter.Predicate) -> typing.Tuple[T_VERTEX, T_VERTEX]:
+        # predicate exists in the schema
+        if not self.schema.has_predicate(node.predicate):
+            raise errors.ConsistencyError(f'predicate {node.predicate} is not in the schema')
+        # determine domain and range
+        pred = self.schema.predicate(node.predicate)
+        dom, rng = pred.domain, pred.range
+        if rng is None:
+            # FIXME: It is a design error that Predicates can have a None range...
+            raise errors.BackendError(f'predicate {pred} has no range')
+        if node.reverse:
+            dom, rng = rng, dom # type: ignore [assignment] # variable re-use confuses mypy
+        # return domain and range
+        return dom, rng
 
-    def _any(self, node: ast.filter.Any, subject: bsc.types._Vertex):
-        return self.__branch(node, subject)
+    def _one_of(self, node: ast.filter.OneOf) -> typing.Tuple[T_VERTEX, T_VERTEX]:
+        # determine domain and range types
+        # NOTE: select the most specific domain and the most generic range
+        dom, rng = None, None
+        for pred in node:
+            # parse child expression
+            subdom, subrng = self._parse_predicate_expression(pred)
+            try:
+                # determine overall domain
+                if dom is None or subdom < dom: # pick most specific domain
+                    dom = subdom
+                # domains must be related across all child expressions
+                if not subdom <= dom and not subdom >= dom:
+                    raise errors.ConsistencyError(f'domains {subdom} and {dom} are not related')
+            except TypeError as err: # compared literal vs. node
+                raise errors.ConsistencyError(f'domains {subdom} and {dom} are not of the same type') from err
 
-    def _all(self, node: ast.filter.All, subject: bsc.types._Vertex):
-        return self.__branch(node, subject)
+            try:
+                # determine overall range
+                if rng is None or subrng > rng: # pick most generic range
+                    rng = subrng
+                # ranges must be related across all child expressions
+                if not subrng <= rng and not subrng >= rng:
+                    raise errors.ConsistencyError(f'ranges {subrng} and {rng} are not related')
+            except TypeError as err: # compared literal vs. node
+                raise errors.ConsistencyError(f'ranges {subrng} and {rng} are not of the same type') from err
+        # check domain and range
+        if dom is None or rng is None:
+            # OneOf guarantees at least one expression, these two cases cannot happen
+            raise errors.UnreachableError()
+        # return domain and range
+        return dom, rng
 
 
-    def __agg(self, node: typing.Union[ast.filter.And, ast.filter.Or], subject: bsc.types._Vertex):
+    ## intermediates
+
+    def _branch(self, type_: T_VERTEX, node: ast.filter._Branch):
+        # type is a Node
+        if not isinstance(type_, bsc.Node):
+            raise errors.ConsistencyError(f'expected a Node, found {type_}')
+        # type exists in the schema
+        # FIXME: Isn't it actually guaranteed that the type (except the root type) is part of the schema?
+        # all types can be traced back to (a) root_type, (b) predicate, or (c) manually set (e.g. in _is).
+        # For (a), we do (and have to) perform a check. For (c), the code base should be consistent throughout
+        # the module, so this is an assumption that has to be ensured in schema.Schema. For (b), we know (and
+        # check) that the predicate is in the schema, hence all node/literals derived from it are also in the
+        # schema by construction of the schema.Schema class. So, why do we check this every time?
+        if type_ not in self.schema.nodes():
+            raise errors.ConsistencyError(f'node {type_} is not in the schema')
+        # predicate is valid
+        dom, rng = self._parse_predicate_expression(node.predicate)
+        # type_ is a subtype of the predicate's domain
+        if not type_ <= dom:
+            raise errors.ConsistencyError(f'expected type {dom} or subtype thereof, found {type_}')
+        # child expression is valid
+        self._parse_filter_expression(rng, node.expr)
+
+    def _agg(self, type_: T_VERTEX, node: ast.filter._Agg):
         for expr in node:
             # child expression is valid
-            self._parse_filter_expression(expr, subject)
-
-    def _and(self, node: ast.filter.And, subject: bsc.types._Vertex):
-        return self.__agg(node, subject)
-
-    def _or(self, node: ast.filter.Or, subject: bsc.types._Vertex):
-        return self.__agg(node, subject)
-
+            self._parse_filter_expression(type_, expr)
 
-    def _not(self, node: ast.filter.Not, subject: bsc.types._Vertex):
+    def _not(self, type_: T_VERTEX, node: ast.filter.Not):
         # child expression is valid
-        self._parse_filter_expression(node.expr, subject)
-
-
-    def _has(self, node: ast.filter.Has, subject: bsc.types._Vertex):
-        # subject is a node type
-        if not isinstance(subject, bsc.Node):
-            raise errors.ConsistencyError(f'Expected a node, found {subject}')
-        # subject exists in the schema
-        if subject not in self.schema.nodes:
-            raise errors.ConsistencyError(f'Invalid node type {subject}')
+        self._parse_filter_expression(type_, node.expr)
+
+    def _has(self, type_: T_VERTEX, node: ast.filter.Has):
+        # type is a Node
+        if not isinstance(type_, bsc.Node):
+            raise errors.ConsistencyError(f'expected a Node, found {type_}')
+        # type exists in the schema
+        if type_ not in self.schema.nodes():
+            raise errors.ConsistencyError(f'node {type_} is not in the schema')
         # predicate is valid
-        dom, rng = self._parse_predicate_expression(node.predicate)
-        # subject is a subtype of the predicate's domain
-        if not subject <= dom:
-            raise errors.ConsistencyError(f'Expected type {dom}, found {subject}')
+        dom, _= self._parse_predicate_expression(node.predicate)
+        # type_ is a subtype of the predicate's domain
+        if not type_ <= dom:
+            raise errors.ConsistencyError(f'expected type {dom}, found {type_}')
         # node.count is a numerical expression
-        self._parse_numerical_expression(node.count, self.schema.literal(ns.xsd.numerical))
-
-
-    def _equals(self, node: ast.filter.Equals, subject: bsc.types._Vertex, numerical: bool = False):
-        # subject is a literal
-        #if not isinstance(subject, bsc.Literal):
-        #    raise errors.ConsistencyError(f'Expected a literal, found {subject}')
-        if isinstance(subject, bsc.Node):
-            # FIXME: How to handle this case?
-            # FIXME: How to check if a NodeType is acceptable?
-            # FIXME: Maybe use flags to control what is expected as node identifiers?
-            from bsfs.graph.nodes import Nodes # FIXME
-            if not isinstance(node.value, Nodes) and not isinstance(node.value, URI):
-                raise errors.ConsistencyError(f'Expected a Nodes or URI, found {node.value}')
-        elif isinstance(subject, bsc.Literal):
-            # literal exists in the schema
-            if subject not in self.schema.literals:
-                raise errors.ConsistencyError(f'Invalid literal type {subject}')
-        else:
-            # FIXME:
-            raise errors.ConsistencyError(f'Expected a literal, found {subject}')
-        # node.value is numeric (if requested)
-        if numerical and not isinstance(node.value, float) and not isinstance(node.value, int):
-            raise errors.ConsistencyError(f'Expected a numerical value (int or float), found {node.value}')
-        # NOTE: We cannot check if node.value agrees with the subject since we don't know
-        # all literal types, their hierarchy, and how the backend converts datatypes.
-
-
-    def _substring(self, node: ast.filter.Substring, subject: bsc.types._Vertex):
-        # subject is a literal
-        if not isinstance(subject, bsc.Literal):
-            raise errors.ConsistencyError(f'Expected a literal, found {subject}')
-        # literal exists in the schema
-        if subject not in self.schema.literals:
-            raise errors.ConsistencyError(f'Invalid literal type {subject}')
-        # node.value matches literal datatype
-        if not subject.is_a(ns.xsd.string):
-            raise errors.ConsistencyError(f'Expected a string literal, found {subject}')
-
-
-    def _lessThan(self, node: ast.filter.LessThan, subject: bsc.types._Vertex):
-        # subject is a literal
-        if not isinstance(subject, bsc.Literal):
-            raise errors.ConsistencyError(f'Expected a literal, found {subject}')
-        # literal exists in the schema
-        if subject not in self.schema.literals:
-            raise errors.ConsistencyError(f'Invalid literal type {subject}')
-        # subject is numerical
-        if not subject.is_a(ns.xsd.numerical):
-            raise errors.ConsistencyError(f'Expected a numerical literal, found {subject}')
-
-
-    def _greaterThan(self, node: ast.filter.GreaterThan, subject: bsc.types._Vertex):
-        # subject is a literal
-        if not isinstance(subject, bsc.Literal):
-            raise errors.ConsistencyError(f'Expected a literal, found {subject}')
-        # literal exists in the schema
-        if subject not in self.schema.literals:
-            raise errors.ConsistencyError(f'Invalid literal type {subject}')
-        # subject is numerical
-        if not subject.is_a(ns.xsd.numerical):
-            raise errors.ConsistencyError(f'Expected a numerical literal, found {subject}')
-
-
-    def _predicate(self, node: ast.filter.Predicate):
-        try:
-            # predicate exists in the schema
-            pred = self.schema.predicate(node.predicate)
-        except KeyError:
-            raise errors.ConsistencyError(f'') # FIXME
-        if node.reverse:
-            return pred.range, pred.domain
-        else:
-            return pred.domain, pred.range
-
+        # FIXME: We have to ensure that ns.xsd.integer is always known in the schema!
+        self._parse_filter_expression(self.schema.literal(ns.xsd.integer), node.count)
+
+
+    ## conditions
+
+    def _is(self, type_: T_VERTEX, node: ast.filter.Is): # pylint: disable=unused-argument # (node)
+        if not isinstance(type_, bsc.Node):
+            raise errors.ConsistencyError(f'expected a Node, found {type_}')
+        if type_ not in self.schema.nodes():
+            raise errors.ConsistencyError(f'node {type_} is not in the schema')
+
+    def _value(self, type_: T_VERTEX, node: ast.filter._Value): # pylint: disable=unused-argument # (node)
+        # type is a literal
+        if not isinstance(type_, bsc.Literal):
+            raise errors.ConsistencyError(f'expected a Literal, found {type_}')
+        # type exists in the schema
+        if type_ not in self.schema.literals():
+            raise errors.ConsistencyError(f'literal {type_} is not in the schema')
+        # FIXME: Check if node.value corresponds to type_
+        # FIXME: A specific literal might be requested (i.e., a numeric type when used in Has)
+
+    def _bounded(self, type_: T_VERTEX, node: ast.filter._Bounded): # pylint: disable=unused-argument # (node)
+        # type is a literal
+        if not isinstance(type_, bsc.Literal):
+            raise errors.ConsistencyError(f'expected a Literal, found {type_}')
+        # type exists in the schema
+        if type_ not in self.schema.literals():
+            raise errors.ConsistencyError(f'literal {type_} is not in the schema')
+        # FIXME: Check if node.value corresponds to type_
 
-    def _oneOf(self, node: ast.filter.OneOf):
-        dom, rng = None, None
-        for pred in node:
-            try:
-                # parse child expression
-                subdom, subrng = self._parse_predicate_expression(pred)
-                # domain and range must be related across all child expressions
-                if not subdom <= dom and not subdom >= dom:
-                    raise errors.ConsistencyError(f'') # FIXME
-                if not subrng <= rng and not subrng >= rng:
-                    raise errors.ConsistencyError(f'') # FIXME
-                # determine overall domain and range
-                if dom is None or subdom < dom: # pick most specific domain
-                    dom = subdom
-                if rng is None or subrng > rng: # pick most generic range
-                    rng = subrng
-            except KeyError:
-                raise errors.ConsistencyError(f'')
-        return dom, rng
 
 ## EOF ##