Set and retrieve tombstone.

lakesuperior/endpoints/ldp.py

@@ -8,7 +8,8 @@ from rdflib import Graph
 from werkzeug.datastructures import FileStorage
 
 from lakesuperior.exceptions import InvalidResourceError, \
-        ResourceExistsError, ResourceNotExistsError, ServerManagedTermError
+        ResourceExistsError, ResourceNotExistsError, ServerManagedTermError, \
+        TombstoneError
 from lakesuperior.model.ldpr import Ldpr
 from lakesuperior.model.ldp_nr import LdpNr
 from lakesuperior.model.ldp_rs import Ldpc, LdpDc, LdpIc, LdpRs
@@ -85,6 +86,8 @@ def get_resource(uuid, force_rdf=False):
         rsrc = Ldpr.readonly_inst(uuid, repr_options)
     except ResourceNotExistsError as e:
         return str(e), 404
+    except TombstoneError as e:
+        return _tombstone_response(e, uuid)
     else:
         out_headers.update(rsrc.head())
         if isinstance(rsrc, LdpRs) \
@@ -125,6 +128,8 @@ def post_resource(parent):
         return str(e), 404
     except InvalidResourceError as e:
         return str(e), 409
+    except TombstoneError as e:
+        return _tombstone_response(e, uuid)
 
     if cls == LdpNr:
         try:
@@ -175,6 +180,8 @@ def put_resource(uuid):
             return str(e), 409
         except ResourceExistsError as e:
             return str(e), 409
+        except TombstoneError as e:
+            return _tombstone_response(e, uuid)
     else:
         if 'prefer' in request.headers:
             prefer = Translator.parse_rfc7240(request.headers['prefer'])
@@ -188,6 +195,8 @@ def put_resource(uuid):
             return str(e), 409
         except ResourceExistsError as e:
             return str(e), 409
+        except TombstoneError as e:
+            return _tombstone_response(e, uuid)
         except ServerManagedTermError as e:
             return str(e), 412
 
@@ -207,6 +216,8 @@ def patch_resource(uuid):
         rsrc.patch(request.get_data().decode('utf-8'))
     except ResourceNotExistsError:
         return 'Resource #{} not found.'.format(rsrc.uuid), 404
+    except TombstoneError as e:
+        return _tombstone_response(e, uuid)
     except ServerManagedTermError as e:
         return str(e), 412
 
@@ -225,6 +236,8 @@ def delete_resource(uuid):
         rsrc.delete()
     except ResourceNotExistsError:
         return 'Resource #{} not found.'.format(rsrc.uuid), 404
+    except TombstoneError as e:
+        return _tombstone_response(e, uuid)
 
     return '', 204, headers
 
@@ -282,3 +295,8 @@ def _get_bitstream(rsrc):
             attachment_filename=rsrc.filename)
 
 
+def _tombstone_response(e, uuid):
+    headers = {
+        'Link' : '<{}/fcr:tombstone>; rel="hasTombstone"'.format(request.url),
+    } if e.uuid == uuid else {}
+    return str(e), 410, headers

lakesuperior/exceptions.py

@@ -102,3 +102,20 @@ class SingleSubjectError(RuntimeError):
                 self.uuid, self.subject)
 
 
+class TombstoneError(RuntimeError):
+    '''
+    Raised when a tombstone resource is found.
+
+    It is up to the caller to handle this which may be a benign and expected
+    result.
+    '''
+    def __init__(self, uuid, ts):
+        self.uuid = uuid
+        self.ts = ts
+
+    def __str__(self):
+        return 'Discovered tombstone resource at /{}, departed: {}'.format(
+                self.uuid, self.ts)
+
+
+

lakesuperior/store_layouts/rdf/base_rdf_layout.py

@@ -184,6 +184,30 @@ class BaseRdfLayout(metaclass=ABCMeta):
             return self.create_rsrc(imr)
 
 
+    def delete_rsrc(self, urn, inbound=True, delete_children=True):
+        '''
+        Delete a resource and optionally its children.
+
+        @param urn (rdflib.term.URIRef) URN of the resource to be deleted.
+        @param inbound (boolean) If specified, delete all inbound relationships
+        as well (this is the default).
+        @param delete_children (boolean) Whether to delete all child resources.
+        This is normally true.
+        '''
+        inbound = inbound if self.conf['referential_integrity'] == 'none' \
+                else True
+        rsrc = self.rsrc(urn)
+        children = rsrc[nsc['ldp'].contains * '+'] if delete_children else []
+
+        self._do_delete_rsrc(rsrc, inbound)
+
+        for child_rsrc in children:
+            self._do_delete_rsrc(child_rsrc, inbound)
+            self._leave_tombstone(child_rsrc.identifier, urn)
+
+        return self._leave_tombstone(urn)
+
+
     ## INTERFACE METHODS ##
 
     # Implementers of custom layouts should look into these methods to
@@ -253,10 +277,29 @@ class BaseRdfLayout(metaclass=ABCMeta):
 
 
     @abstractmethod
-    def delete_rsrc(self, urn, inbound=True):
+    def _do_delete_rsrc(self, rsrc, inbound):
+        '''
+        Delete a single resource.
+
+        @param rsrc (rdflib.resource.Resource) Resource to be deleted.
+        @param inbound (boolean) Whether to delete the inbound relationships.
+        '''
         pass
 
 
+    @abstractmethod
+    def _leave_tombstone(self, urn, parent_urn=None):
+        '''
+        Leave a tombstone when deleting a resource.
+
+        If a parent resource is specified, a pointer to the parent's tombstone
+        is added instead.
+
+        @param urn (rdflib.term.URIRef) URN of the deleted resource.
+        @param parent_urn (rdflib.term.URIRef) URI of deleted parent.
+        '''
+        pass
+
 
     ## PROTECTED METHODS  ##
 

lakesuperior/store_layouts/rdf/simple_layout.py

@@ -13,7 +13,7 @@ from lakesuperior.dictionaries.namespaces import ns_mgr as nsm
 from lakesuperior.dictionaries.srv_mgd_terms import  srv_mgd_subjects, \
         srv_mgd_predicates, srv_mgd_types
 from lakesuperior.exceptions import InvalidResourceError, \
-        ResourceNotExistsError
+        ResourceNotExistsError, TombstoneError
 from lakesuperior.store_layouts.rdf.base_rdf_layout import BaseRdfLayout
 from lakesuperior.util.translator import Translator
 
@@ -40,7 +40,7 @@ class SimpleLayout(BaseRdfLayout):
         inbound_qry = '\nOPTIONAL {{ ?s1 ?p1 {} . }} .'.format(uri.n3()) \
                 if incl_inbound else ''
         embed_children_qry = '''
-        \nOPTIONAL {{
+        OPTIONAL {{
           {0} ldp:contains ?c .
           ?c ?cp ?co .
         }}
@@ -67,8 +67,8 @@ class SimpleLayout(BaseRdfLayout):
             #FILTER (?p != premis:hasMessageDigest) .
         }}
         '''.format(uri=uri.n3(), inb_cnst=inbound_construct,
-                    inb_qry=inbound_qry, incl_chld=incl_children_qry,
-                    embed_chld=embed_children_qry, omit_srv_mgd=srv_mgd_qry)
+                inb_qry=inbound_qry, incl_chld=incl_children_qry,
+                embed_chld=embed_children_qry, omit_srv_mgd=srv_mgd_qry)
 
         try:
             qres = self.query(q)
@@ -83,7 +83,20 @@ class SimpleLayout(BaseRdfLayout):
         if strict and not len(g):
             raise ResourceNotExistsError(uri)
 
-        return Resource(g, uri)
+        rsrc = Resource(g, uri)
+
+        # Check if resource is a tombstone.
+        if rsrc[RDF.type : nsc['fcsystem'].Tombstone]:
+            raise TombstoneError(
+                    Translator.uri_to_uuid(rsrc.identifier),
+                    rsrc.value(nsc['fcrepo'].created))
+        elif rsrc.value(nsc['fcsystem'].tombstone):
+            tombstone_rsrc = rsrc.value(nsc['fcsystem'].tombstone)
+            raise TombstoneError(
+                    Translator.uri_to_uuid(rsrc.identifier),
+                    tombstone_rsrc.value(nsc['fcrepo'].created))
+
+        return rsrc
 
 
     def ask_rsrc_exists(self, urn):
@@ -91,7 +104,8 @@ class SimpleLayout(BaseRdfLayout):
         See base_rdf_layout.ask_rsrc_exists.
         '''
         self._logger.info('Checking if resource exists: {}'.format(urn))
-        return (urn, Variable('p'), Variable('o')) in self.ds
+        imr = self.extract_imr(urn, incl_children=False)
+        return len(imr.graph) > 0
 
 
     def create_rsrc(self, imr):
@@ -145,23 +159,33 @@ class SimpleLayout(BaseRdfLayout):
             self.ds.add(t)
 
 
-    def delete_rsrc(self, urn, inbound=True, delete_children=True):
+    ## PROTECTED METHODS ##
+
+    def _do_delete_rsrc(self, rsrc, inbound):
         '''
-        Delete a resource. If `inbound` is specified, delete all inbound
-        relationships as well (this is the default).
+        See BaseRdfLayout._do_delete_rsrc
         '''
-        rsrc = self.rsrc(urn)
-        if delete_children:
-            self._logger.info('Deleting resource children')
-            for c in rsrc[nsc['ldp'].contains * '+']:
-                self._logger.debug('Removing child: {}'.format(c))
-                c.remove(Variable('p'))
-
-        print('Removing resource {}.'.format(rsrc.identifier))
+        urn = rsrc.identifier
+        print('Removing resource {}.'.format(urn))
 
         rsrc.remove(Variable('p'))
+
         if inbound:
-            self.ds.remove(
-                    (Variable('s'), Variable('p'), rsrc.identifier))
+            self.ds.remove((Variable('s'), Variable('p'), rsrc.identifier))
+
+        return urn
+
+
+    def _leave_tombstone(self, urn, parent_urn=None):
+        '''
+        See BaseRdfLayout._leave_tombstone
+        '''
+        if parent_urn:
+            self.ds.add((urn, nsc['fcsystem'].tombstone, parent_urn))
+        else:
+            # @TODO Use gunicorn to get request timestamp.
+            ts = Literal(arrow.utcnow(), datatype=XSD.dateTime)
+            self.ds.add((urn, RDF.type, nsc['fcsystem'].Tombstone))
+            self.ds.add((urn, nsc['fcrepo'].created, ts))