Merge branch 'develop'v0.23.03

1 files changed, 218 insertions, 32 deletions

diff --git a/bsfs/graph/nodes.py b/bsfs/graph/nodes.py
index c417a0e..47b0217 100644
--- a/bsfs/graph/nodes.py
+++ b/bsfs/graph/nodes.py
@@ -1,21 +1,20 @@
-"""
 
-Part of the BlackStar filesystem (bsfs) module.
-A copy of the license is provided with the project.
-Author: Matthias Baumgartner, 2022
-"""
 # imports
+from collections import abc
 import time
 import typing
 
 # bsfs imports
-from bsfs import schema as _schema
+from bsfs import schema as bsc
 from bsfs.namespace import ns
+from bsfs.query import ast, validate
 from bsfs.triple_store import TripleStoreBase
 from bsfs.utils import errors, URI, typename
 
 # inner-module imports
 from . import ac
+from . import result
+from . import walk
 
 # exports
 __all__: typing.Sequence[str] = (
@@ -26,18 +25,20 @@ __all__: typing.Sequence[str] = (
 ## code ##
 
 class Nodes():
-    """
+    """Container for graph nodes, provides operations on nodes.
+
+    NOTE: Should not be created directly but only via `bsfs.graph.Graph`.
     NOTE: guids may or may not exist. This is not verified as nodes are created on demand.
     """
 
     # triple store backend.
     _backend: TripleStoreBase
 
-    # user uri.
-    _user: URI
+    # access controls.
+    _ac: ac.AccessControlBase
 
     # node type.
-    _node_type: _schema.Node
+    _node_type: bsc.Node
 
     # guids of nodes. Can be empty.
     _guids: typing.Set[URI]
@@ -45,34 +46,35 @@ class Nodes():
     def __init__(
             self,
             backend: TripleStoreBase,
-            user: URI,
-            node_type: _schema.Node,
+            access_control: ac.AccessControlBase,
+            node_type: bsc.Node,
             guids: typing.Iterable[URI],
             ):
+        # set main members
         self._backend = backend
-        self._user = user
+        self._ac = access_control
         self._node_type = node_type
-        self._guids = set(guids)
-        self.__ac = ac.NullAC(self._backend, self._user)
+        # convert to URI since this is not guaranteed by Graph
+        self._guids = {URI(guid) for guid in guids}
 
     def __eq__(self, other: typing.Any) -> bool:
         return isinstance(other, Nodes) \
            and self._backend == other._backend \
-           and self._user == other._user \
+           and self._ac == other._ac \
            and self._node_type == other._node_type \
            and self._guids == other._guids
 
     def __hash__(self) -> int:
-        return hash((type(self), self._backend, self._user, self._node_type, tuple(sorted(self._guids))))
+        return hash((type(self), self._backend, self._ac, self._node_type, tuple(sorted(self._guids))))
 
     def __repr__(self) -> str:
-        return f'{typename(self)}({self._backend}, {self._user}, {self._node_type}, {self._guids})'
+        return f'{typename(self)}({self._backend}, {self._ac}, {self._node_type}, {self._guids})'
 
     def __str__(self) -> str:
         return f'{typename(self)}({self._node_type}, {self._guids})'
 
     @property
-    def node_type(self) -> _schema.Node:
+    def node_type(self) -> bsc.Node:
         """Return the node's type."""
         return self._node_type
 
@@ -81,9 +83,72 @@ class Nodes():
         """Return all node guids."""
         return iter(self._guids)
 
+    @property
+    def schema(self) -> bsc.Schema:
+        """Return the store's local schema."""
+        return self._backend.schema
+
+    def __add__(self, other: typing.Any) -> 'Nodes':
+        """Concatenate guids. Backend, AC, and node type must match."""
+        if not isinstance(other, type(self)):
+            return NotImplemented
+        if self._backend != other._backend:
+            raise ValueError(other)
+        if self._ac != other._ac:
+            raise ValueError(other)
+        if self.node_type != other.node_type:
+            raise ValueError(other)
+        return Nodes(self._backend, self._ac, self.node_type, self._guids | other._guids)
+
+    def __or__(self, other: typing.Any) -> 'Nodes':
+        """Concatenate guids. Backend, AC, and node type must match."""
+        return self.__add__(other)
+
+    def __sub__(self, other: typing.Any) -> 'Nodes':
+        """Subtract guids. Backend, AC, and node type must match."""
+        if not isinstance(other, type(self)):
+            return NotImplemented
+        if self._backend != other._backend:
+            raise ValueError(other)
+        if self._ac != other._ac:
+            raise ValueError(other)
+        if self.node_type != other.node_type:
+            raise ValueError(other)
+        return Nodes(self._backend, self._ac, self.node_type, self._guids - other._guids)
+
+    def __and__(self, other: typing.Any) -> 'Nodes':
+        """Intersect guids. Backend, AC, and node type must match."""
+        if not isinstance(other, type(self)):
+            return NotImplemented
+        if self._backend != other._backend:
+            raise ValueError(other)
+        if self._ac != other._ac:
+            raise ValueError(other)
+        if self.node_type != other.node_type:
+            raise ValueError(other)
+        return Nodes(self._backend, self._ac, self.node_type, self._guids & other._guids)
+
+    def __len__(self) -> int:
+        """Return the number of guids."""
+        return len(self._guids)
+
+    def __iter__(self) -> typing.Iterator['Nodes']:
+        """Iterate over individual guids. Returns `Nodes` instances."""
+        return iter(
+            Nodes(self._backend, self._ac, self.node_type, {guid})
+            for guid in self._guids
+            )
+
+    def __getattr__(self, name: str):
+        try:
+            return super().__getattr__(name) # type: ignore [misc] # parent has no getattr
+        except AttributeError:
+            pass
+        return walk.Walk(self, walk.Walk.step(self.schema, self.node_type, name))
+
     def set(
             self,
-            pred: URI, # FIXME: URI or _schema.Predicate?
+            pred: URI, # FIXME: URI or bsc.Predicate?
             value: typing.Any,
             ) -> 'Nodes':
         """Set predicate *pred* to *value*."""
@@ -91,7 +156,7 @@ class Nodes():
 
     def set_from_iterable(
             self,
-            predicate_values: typing.Iterable[typing.Tuple[URI, typing.Any]], # FIXME: URI or _schema.Predicate?
+            predicate_values: typing.Iterable[typing.Tuple[URI, typing.Any]], # FIXME: URI or bsc.Predicate?
             ) -> 'Nodes':
         """Set mutliple predicate-value pairs at once."""
         # TODO: Could group predicate_values by predicate to gain some efficiency
@@ -105,7 +170,7 @@ class Nodes():
             self._backend.commit()
 
         except (
-                errors.PermissionDeniedError, # tried to set a protected predicate (ns.bsm.t_created)
+                errors.PermissionDeniedError, # tried to set a protected predicate
                 errors.ConsistencyError, # node types are not in the schema or don't match the predicate
                 errors.InstanceError, # guids/values don't have the correct type
                 TypeError, # value is supposed to be a Nodes instance
@@ -120,6 +185,126 @@ class Nodes():
 
         return self
 
+    def get(
+            self,
+            *paths: typing.Union[URI, typing.Iterable[URI]],
+            view: typing.Union[typing.Type[list], typing.Type[dict]] = dict,
+            **view_kwargs,
+            ) -> typing.Any:
+        """Get values or nodes at *paths*.
+        Return an iterator (view=list) or a dict (view=dict) over the results.
+        """
+        # FIXME: user-provided Fetch query AST?
+        # check args
+        if len(paths) == 0:
+            raise AttributeError('expected at least one path, found none')
+        if view not in (dict, list):
+            raise ValueError(f'expected dict or list, found {view}')
+        # process paths: create fetch ast, build name mapping, and find unique paths
+        schema = self.schema
+        statements = set()
+        name2path = {}
+        unique_paths = set() # paths that result in a single (unique) value
+        normpath: typing.Tuple[URI, ...]
+        for idx, path in enumerate(paths):
+            # normalize path
+            if isinstance(path, str):
+                normpath = (URI(path), )
+            elif isinstance(path, abc.Iterable):
+                if not all(isinstance(step, str) for step in path):
+                    raise TypeError(path)
+                normpath = tuple(URI(step) for step in path)
+            else:
+                raise TypeError(path)
+            # check path's schema consistency
+            if not all(schema.has_predicate(pred) for pred in normpath):
+                raise errors.ConsistencyError(f'path is not fully covered by the schema: {path}')
+            # check path's uniqueness
+            if all(schema.predicate(pred).unique for pred in normpath):
+                unique_paths.add(path)
+            # fetch tail predicate
+            tail = schema.predicate(normpath[-1])
+            # determine tail ast node type
+            factory = ast.fetch.Node if isinstance(tail.range, bsc.Node) else ast.fetch.Value
+            # assign name
+            name = f'fetch{idx}'
+            name2path[name] = (path, tail)
+            # create tail ast node
+            curr: ast.fetch.FetchExpression = factory(tail.uri, name)
+            # walk towards front
+            hop: URI
+            for hop in normpath[-2::-1]:
+                curr = ast.fetch.Fetch(hop, curr)
+            # add to fetch query
+            statements.add(curr)
+        # aggregate fetch statements
+        if len(statements) == 1:
+            fetch = next(iter(statements))
+        else:
+            fetch = ast.fetch.All(*statements)
+        # add access controls to fetch
+        fetch = self._ac.fetch_read(self.node_type, fetch)
+
+        if len(self._guids) == 0:
+            # shortcut: no need to query; no triples
+            # FIXME: if the Fetch query can given by the user, we might want to check its validity
+            def triple_iter():
+                return []
+        else:
+            # compose filter ast
+            filter = ast.filter.IsIn(self.guids) # pylint: disable=redefined-builtin
+            # add access controls to filter
+            filter = self._ac.filter_read(self.node_type, filter) # type: ignore [assignment]
+
+            # validate queries
+            validate.Filter(self._backend.schema).validate(self.node_type, filter)
+            validate.Fetch(self._backend.schema).validate(self.node_type, fetch)
+
+            # process results, convert if need be
+            def triple_iter():
+                # query the backend
+                triples = self._backend.fetch(self.node_type, filter, fetch)
+                # process triples
+                for root, name, raw in triples:
+                    # get node
+                    node = Nodes(self._backend, self._ac, self.node_type, {root})
+                    # get path
+                    path, tail = name2path[name]
+                    # covert raw to value
+                    if isinstance(tail.range, bsc.Node):
+                        value = Nodes(self._backend, self._ac, tail.range, {raw})
+                    else:
+                        value = raw
+                    # emit triple
+                    yield node, path, value
+
+        # simplify by default
+        view_kwargs['node'] = view_kwargs.get('node', len(self._guids) != 1)
+        view_kwargs['path'] = view_kwargs.get('path', len(paths) != 1)
+        view_kwargs['value'] = view_kwargs.get('value', False)
+
+        # return results view
+        if view == list:
+            return result.to_list_view(
+                triple_iter(),
+                # aggregation args
+                **view_kwargs,
+                )
+
+        if view == dict:
+            return result.to_dict_view(
+                triple_iter(),
+                # context
+                len(self._guids) == 1,
+                len(paths) == 1,
+                unique_paths,
+                # aggregation args
+                **view_kwargs,
+                )
+
+        raise errors.UnreachableError() # view was already checked
+
+
     def __set(self, predicate: URI, value: typing.Any):
         """
         """
@@ -135,7 +320,7 @@ class Nodes():
         # FIXME: Needed? Could be integrated into other AC methods (by passing the predicate!)
         #        This could allow more fine-grained predicate control (e.g. based on ownership)
         #        rather than a global approach like this.
-        if self.__ac.is_protected_predicate(pred):
+        if self._ac.is_protected_predicate(pred):
             raise errors.PermissionDeniedError(pred)
 
         # set operation affects all nodes (if possible)
@@ -145,11 +330,11 @@ class Nodes():
         guids = set(self._ensure_nodes(node_type, guids))
 
         # check value
-        if isinstance(pred.range, _schema.Literal):
+        if isinstance(pred.range, bsc.Literal):
             # check write permissions on existing nodes
             # As long as the user has write permissions, we don't restrict
             # the creation or modification of literal values.
-            guids = set(self.__ac.write_literal(node_type, guids))
+            guids = set(self._ac.write_literal(node_type, guids))
 
             # insert literals
             # TODO: Support passing iterators as values for non-unique predicates
@@ -160,8 +345,9 @@ class Nodes():
                 [value],
                 )
 
-        elif isinstance(pred.range, _schema.Node):
+        elif isinstance(pred.range, bsc.Node):
             # check value type
+            # FIXME: value could be a set of Nodes
             if not isinstance(value, Nodes):
                 raise TypeError(value)
             # value's node_type must be a subclass of the predicate's range
@@ -172,14 +358,14 @@ class Nodes():
             # Link permissions cover adding and removing links on the source node.
             # Specifically, link permissions also allow to remove links to other
             # nodes if needed (e.g. for unique predicates).
-            guids = set(self.__ac.link_from_node(node_type, guids))
+            guids = set(self._ac.link_from_node(node_type, guids))
 
             # get link targets
             targets = set(value.guids)
             # ensure existence of value nodes; create nodes if need be
             targets = set(self._ensure_nodes(value.node_type, targets))
             # check link permissions on target nodes
-            targets = set(self.__ac.link_to_node(value.node_type, targets))
+            targets = set(self._ac.link_to_node(value.node_type, targets))
 
             # insert node links
             self._backend.set(
@@ -192,7 +378,7 @@ class Nodes():
         else:
             raise errors.UnreachableError()
 
-    def _ensure_nodes(self, node_type: _schema.Node, guids: typing.Iterable[URI]):
+    def _ensure_nodes(self, node_type: bsc.Node, guids: typing.Iterable[URI]):
         """
         """
         # check node existence
@@ -203,14 +389,14 @@ class Nodes():
         # create nodes if need be
         if len(missing) > 0:
             # check which missing nodes can be created
-            missing = set(self.__ac.createable(node_type, missing))
+            missing = set(self._ac.createable(node_type, missing))
             # create nodes
             self._backend.create(node_type, missing)
             # add bookkeeping triples
             self._backend.set(node_type, missing,
-                self._backend.schema.predicate(ns.bsm.t_created), [time.time()])
+                self._backend.schema.predicate(ns.bsn.t_created), [time.time()])
             # add permission triples
-            self.__ac.create(node_type, missing)
+            self._ac.create(node_type, missing)
         # return available nodes
         return existing | missing