schema: Add DefinitionsNamespace class

This is a nice way of getting URIs for the various entities as we load
the .morph files, and can be reused.

Change-Id: I7187e9c4692d0f1059856502b521bc0e4e97a270

1 files changed, 45 insertions, 46 deletions

diff --git a/schema/parse.py b/schema/parse.py
index c2f369fb..1ee1b367 100644
--- a/schema/parse.py
+++ b/schema/parse.py
@@ -69,42 +69,42 @@ def get_name_from_morph_file(path):
 
 # FIXME: can you use assignment instead of Resource.set ?
 
-def uriref_for_chunk(base_uri, chunk_name):
-    uriref = base_uri + 'chunks/' + chunk_name
-    return rdflib.URIRef(uriref)
+class DefinitionsNamespace(rdflib.Namespace):
+    '''Helpers to construct URIs for Baserock entities.
 
+    These functions all return instances of the rdflib.URIRef() class.
 
-def uriref_for_chunk_reference(base_uri, stratum_name, chunk_name):
-    stratum_uriref = uriref_for_stratum(base_uri, stratum_name)
-    chunk_reference_uriref = stratum_uriref + '/chunk-refs/' + chunk_name
-    return rdflib.URIRef(chunk_reference_uriref)
+    Example:
 
+        ns = DefinitionsNamespace('http://example.com')
+        chunk1 = ns.chunk('gcc')
+        print(chunk1)   # => rdflib.URIRef('http://example.com/chunks/gcc')
 
-def uriref_for_cluster(base_uri, cluster_name):
-    uriref = base_uri + 'clusters/' + cluster_name
-    return rdflib.URIRef(uriref)
-
+    '''
 
-def uriref_for_stratum(base_uri, stratum_name):
-    uriref = base_uri + 'strata/' + stratum_name
-    return rdflib.URIRef(uriref)
+    def chunk(self, chunk_name):
+        return self.term('chunks/' + chunk_name)
 
+    def chunk_reference(self, stratum_uriref, chunk_name):
+        assert isinstance(stratum_uriref, rdflib.URIRef)
+        return stratum_uriref + '/chunk-refs/' + chunk_name
 
-def uriref_for_stratum_artifact(base_uri, stratum_name, artifact_name):
-    stratum_uriref = uriref_for_stratum(base_uri, stratum_name)
-    artifact_uriref = stratum_uriref + '/products/' + artifact_name
-    return rdflib.URIRef(artifact_uriref)
+    def cluster(self, cluster_name):
+        return self.term('clusters/' + cluster_name)
 
+    def stratum(self, stratum_name):
+        return self.term('strata/' + stratum_name)
 
-def uriref_for_system(base_uri, system_name):
-    uriref = base_uri + 'systems/' + system_name
-    return rdflib.URIRef(uriref)
+    def stratum_artifact(self, stratum_uriref, artifact_name):
+        assert isinstance(stratum_uriref, rdflib.URIRef)
+        return stratum_uriref + '/products/' + artifact_name
 
+    def system(self, system_name):
+        return self.term('systems/' + system_name)
 
-def uriref_for_system_deployment(base_uri, cluster_name, label):
-    cluster_uriref = uriref_for_cluster(base_uri, cluster_name)
-    system_deployment_uriref = cluster_uriref + label
-    return rdflib.URIRef(system_deployment_uriref)
+    def system_deployment(self, cluster_uriref, label):
+        assert isinstance(cluster_uriref, rdflib.URIRef)
+        return cluster_uriref + '/' + label
 
 
 def load_all_morphologies(path='.'):
@@ -123,13 +123,14 @@ def load_all_morphologies(path='.'):
         except Exception as e:
             warnings.warn("Problem loading %s: %s" % (filename, e))
 
-        # FIXME:
-        base_uri = 'http://example.com/'
+        # FIXME: caller should pass in the namespace, or we should make one
+        # up based on os.path.abspath(path)
+        ns = DefinitionsNamespace('http://example.com/')
 
         entity = None
 
         if contents['kind'] == 'chunk':
-            chunk_uriref = uriref_for_chunk(base_uri, contents['name'])
+            chunk_uriref = ns.chunk(contents['name'])
             entity = chunk = rdflib.resource.Resource(graph, chunk_uriref)
 
             # FIXME: order is lost here !!!!!
@@ -162,19 +163,18 @@ def load_all_morphologies(path='.'):
                           rdflib.Literal(contents['post-install-commands']))
 
         elif contents['kind'] == 'stratum':
-            stratum_name = contents['name']
-            stratum_uriref = uriref_for_stratum(base_uri, stratum_name)
+            stratum_uriref = ns.stratum(contents['name'])
             entity = stratum = rdflib.resource.Resource(graph, stratum_uriref)
 
             for entry in contents.get('build-depends', []):
                 build_dep_file = os.path.join(toplevel_path, entry['morph'])
                 build_dep_name = get_name_from_morph_file(build_dep_file)
-                build_dep_uriref = uriref_for_stratum(base_uri, build_dep_name)
+                build_dep_uriref = ns.stratum(build_dep_name)
                 stratum.add(BASEROCK.hasBuildDependency, build_dep_uriref)
 
             for entry in contents.get('products', []):
-                artifact_uri = uriref_for_stratum_artifact(
-                    base_uri,  stratum_name, entry['artifact'])
+                artifact_uri = ns.stratum_artifact(
+                    stratum_uriref, entry['artifact'])
                 artifact = rdflib.resource.Resource(graph, artifact_uri)
                 # FIXME: order probably lost here
                 if 'includes' in entry:
@@ -194,11 +194,11 @@ def load_all_morphologies(path='.'):
                 else:
                     chunk_name = entry['name']
 
-                chunk_ref_uriref = uriref_for_chunk_reference(
-                    base_uri, stratum_name, chunk_name)
+                chunk_ref_uriref = ns.chunk_reference(
+                    stratum_uriref, chunk_name)
                 chunk_ref = rdflib.resource.Resource(graph, chunk_ref_uriref)
 
-                chunk_uriref = uriref_for_chunk(base_uri, chunk_name)
+                chunk_uriref = ns.chunk(chunk_name)
                 chunk_ref.set(BASEROCK.refersToChunk, chunk_uriref)
 
                 chunk_ref.set(BASEROCK.repo, rdflib.Literal(entry['repo']))
@@ -212,15 +212,15 @@ def load_all_morphologies(path='.'):
                               rdflib.Literal(entry.get('prefix', '/usr')))
 
                 for entry_dep in entry.get('build-depends', []):
-                    build_dep_uriref = uriref_for_chunk_reference(
-                        base_uri, stratum_name, entry_dep)
+                    build_dep_uriref = ns.chunk_reference(
+                        stratum_uriref, entry_dep)
                     chunk_ref.set(BASEROCK.hasChunkBuildDependency,
                                   build_dep_uriref)
 
                 stratum.add(BASEROCK.containsChunkReference, chunk_ref)
 
         elif contents['kind'] == 'system':
-            system_uriref = uriref_for_system(base_uri, contents['name'])
+            system_uriref = ns.system(contents['name'])
             entity = system = rdflib.resource.Resource(graph, system_uriref)
 
             system.set(BASEROCK.arch, rdflib.Literal(contents['arch']))
@@ -236,8 +236,8 @@ def load_all_morphologies(path='.'):
                     artifacts = ['%s-runtime' % entry['name'],
                                  '%s-devel' % entry['name']]
                 for artifact in artifacts:
-                    artifact_uriref = uriref_for_stratum_artifact(
-                        base_uri, entry['name'], artifact)
+                    artifact_uriref = ns.stratum_artifact(
+                        ns.stratum(entry['name']), artifact)
                     system.add(BASEROCK.containsStratumArtifact,
                                artifact_uriref)
 
@@ -245,19 +245,18 @@ def load_all_morphologies(path='.'):
                 contents.get('configuration-extensions', [])))
 
         elif contents['kind'] == 'cluster':
-            cluster_name = contents['name']
-            cluster_uriref = uriref_for_cluster(base_uri, cluster_name)
+            cluster_uriref = ns.cluster(contents['name'])
             entity = cluster = rdflib.resource.Resource(graph, cluster_uriref)
 
             for entry in contents.get('systems', []):
                 system_morph_file = os.path.join(toplevel_path, entry['morph'])
                 system_name = get_name_from_morph_file(system_morph_file)
-                system_uriref = uriref_for_system(base_uri, system_name)
+                system_uriref = ns.system(system_name)
 
                 # FIXME: ignores deploy-defaults at present
                 for label, details in entry['deploy'].items():
-                    deployment_uriref = uriref_for_system_deployment(
-                        base_uri, cluster_name, label)
+                    deployment_uriref = ns.system_deployment(
+                        cluster_uriref, label)
                     deployment = rdflib.resource.Resource(
                         graph, deployment_uriref)