Fix GET; add HEAD; initial header set.

lakesuperior/ldp/ldpr.py

@@ -42,7 +42,7 @@ class ResourceNotExistsError(RuntimeError):
 
 class InvalidResourceError(RuntimeError):
     '''
-    Raised when a resource is found.
+    Raised when an invalid resource is found.
 
     This usually surfaces at the HTTP level as a 409 or other error.
     '''
@@ -222,7 +222,7 @@ class Ldpr(metaclass=ABCMeta):
         if not hasattr(self, '_ldp_types'):
             self._ldp_types = set()
             for t in self.types:
-                if t.qname[:4] == 'ldp:':
+                if t.qname()[:4] == 'ldp:':
                     self._ldp_types.add(t)
         return self._ldp_types
 
@@ -357,11 +357,29 @@ class Ldpr(metaclass=ABCMeta):
 
     ## LDP METHODS ##
 
-    def get(self):
+    def head(self):
+        '''
+        Return values for the headers.
+        '''
+        headers = self.gs.headers
+
+        for t in self.ldp_types:
+            headers['Link'].append('{};rel="type"'.format(t.identifier.n3()))
+
+        return headers
+
+
+    def get(self, inbound=False):
         '''
         https://www.w3.org/TR/ldp/#ldpr-HTTP_GET
         '''
-        return Translator.globalize_rsrc(self.rsrc)
+        try:
+            g = self.gs.out_graph(inbound)
+        except ResultException:
+            # RDFlib bug? https://github.com/RDFLib/rdflib/issues/775
+            raise ResourceNotExistsError()
+
+        return Translator.globalize_rsrc(g)
 
 
     @transactional

lakesuperior/store_strategies/rdf/base_rdf_strategy.py

@@ -112,10 +112,20 @@ class BaseRdfStrategy(metaclass=ABCMeta):
         pass
 
 
+    @property
+    @abstractmethod
+    @needs_rsrc
+    def headers(self):
+        '''
+        Return minimal information for generating HTTP headers.
+        '''
+        pass
+
+
     ## PUBLIC METHODS ##
 
     @abstractmethod
-    def ask_rsrc_exists(self, rsrc=None):
+    def ask_rsrc_exists(self):
         '''
         Ask if a resource exists (is stored) in the graph store.
 

lakesuperior/store_strategies/rdf/simple_strategy.py

@@ -4,6 +4,7 @@ import arrow
 
 from rdflib import Graph
 from rdflib.namespace import XSD
+from rdflib.resource import Resource
 from rdflib.term import Literal, URIRef, Variable
 
 from lakesuperior.core.namespaces import ns_collection as nsc
@@ -25,11 +26,42 @@ class SimpleStrategy(BaseRdfStrategy):
     '''
 
     @property
-    def out_graph(self):
+    def headers(self):
+        '''
+        See base_rdf_strategy.headers.
+        '''
+        headers = {
+            'ETag' : 'W/"{}"'.format(
+                self.rsrc.value(nsc['premis'].hasMessageDigest)),
+            'Link' : [],
+        }
+
+        last_updated_term = self.rsrc.value(nsc['fedora'].lastUpdated) or \
+                self.rsrc.value(nsc['fedora'].lastUpdated)
+        if last_updated_term:
+            headers['Last-Modified'] = arrow.get(last_updated_term)\
+                .format('ddd, D MMM YYYY HH:mm:ss Z')
+
+        return headers
+
+
+    def out_graph(self, inbound=False):
         '''
         See base_rdf_strategy.out_graph.
         '''
-        return self.rsrc.graph
+        inbound_qry = '\n?s1 ?p1 {}'.format(self.base_urn.n3()) \
+                if inbound else ''
+        q = '''
+        CONSTRUCT {{
+            {0} ?p ?o .{1}
+        }} WHERE {{
+            {0} ?p ?o .{1}
+        }}
+        '''.format(self.base_urn.n3(), inbound_qry)
+
+        qres = self.rsrc.graph.query(q)
+
+        return Resource(qres.graph, self.base_urn)
 
 
     def ask_rsrc_exists(self, rsrc=None):

lakesuperior/util/translator.py

@@ -76,10 +76,15 @@ class Translator:
         '''
         q = '''
         CONSTRUCT {{ ?s ?p ?o . }} WHERE {{
-          ?s ?p ?o .
-          {{ FILTER STRSTARTS(str(?s), "{0}") . }}
+          {{
+            ?s ?p ?o .
+            FILTER STRSTARTS(str(?s), "{0}") .
+          }}
           UNION
-          {{ FILTER STRSTARTS(str(?o), "{0}") . }}
+          {{
+            ?s ?p ?o .
+            FILTER STRSTARTS(str(?o), "{0}") .
+          }}
         }}'''.format(nsc['fcres'])
         flt_g = g.query(q)
 

server.py

@@ -45,14 +45,14 @@ def get_resource(uuid):
     Retrieve RDF or binary content.
     '''
     # @TODO Add conditions for LDP-NR
-    rsrc = Ldpc(uuid).get()
+    rsrc = Ldpc(uuid)
     try:
-        headers = {
-            #'ETag' : 'W/"{}"'.format(ret.value(nsc['premis
-        }
-        return (rsrc.graph.serialize(format='turtle'), headers)
+        out = rsrc.get()
     except ResourceNotExistsError:
         return 'Resource #{} not found.'.format(rsrc.uuid), 404
+    else:
+        headers = rsrc.head()
+        return (out.graph.serialize(format='turtle'), headers)
 
 
 @app.route('/rest/<path:parent>', methods=['POST'])