app: show more meta information in node info

Show ulo:name, ulo:paratype (e.g. lemma) and ulo:sourceref.  I would
like to now reference the sourceref to the original source as that is
a real world application.

src/ulo-storage-applications/src/main/java/info/mathhub/uloapi/html/Routes.java

 package info.mathhub.uloapi.html;
 
 import info.mathhub.uloapi.config.Config;
+import info.mathhub.uloapi.query.Meta;
 import info.mathhub.uloapi.query.Query;
 import info.mathhub.uloapi.query.Statistics;
 import info.mathhub.uloapi.query.Timer;
-import org.eclipse.rdf4j.model.IRI;
 import org.eclipse.rdf4j.model.Literal;
 import org.eclipse.rdf4j.model.Statement;
 import org.slf4j.Logger;
@@ -82,10 +82,12 @@ public class Routes {
         final String base64uri = request.params("base64uri");
         final String uri = Base64.decode(base64uri);
 
+        final Meta meta = query.getMeta(uri);
         final List<PrintableIRI> uses = PrintableIRI.convert(query.getUses(uri));
 
         final Map<String, Object> model = new HashMap<>();
         model.put("uri", uri);
+        model.put("meta", meta);
         model.put("uses", uses);
 
         return new ModelAndView(withGlobals(model), "explore_node.flt");

src/ulo-storage-applications/src/main/java/info/mathhub/uloapi/query/Meta.java

+package info.mathhub.uloapi.query;
+
+import info.mathhub.uloapi.ontology.ULO;
+import org.eclipse.rdf4j.model.IRI;
+
+/**
+ * Contains meta information for a given URI.
+ */
+public class Meta {
+    /**
+     * IRI of the object.
+     */
+    public IRI iri;
+
+    /**
+     * {@link ULO#name} of the object.
+     */
+    public String name;
+
+    /**
+     * {@link ULO#sourceref} of the object.
+     */
+    public String sourceref;
+
+    /**
+     * {@link ULO#paratype} of this object.
+     */
+    public String paratype;
+
+    public String getName() {
+        return this.name;
+    }
+
+    public String getSourceref() {
+        return this.sourceref;
+    }
+
+    public String getParatype() {
+        return this.paratype;
+    }
+
+    @Override
+    public String toString() {
+        return String.format(
+                "Meta(iri=%s name=%s sourceref=%s paratype=%s)",
+                this.iri.toString(), this.name, this.sourceref, this.paratype
+        );
+    }
+
+}

src/ulo-storage-applications/src/main/java/info/mathhub/uloapi/query/Query.java

@@ -197,4 +197,49 @@ public class Query {
 
         return GraphDB.execute(this.serverUrl, this.repository, operation);
     }
+
+    /**
+     * Try to create a {@link Meta} object for argument {@code nodeuri}.
+     *
+     * @param nodeuri The URI of the node for which we query the meta data.
+     * @return A {@link Meta} object for argument {@code nodeuri}. Never {@code null},
+     * but the returned object can contain {@code null} fields.
+     */
+    public Meta getMeta(String nodeuri) {
+        final GraphDB.Operation<Meta> operation = (manager, repository, connection) -> {
+            final IRI iri = IRIs.fromString(nodeuri);
+
+            final Meta meta = new Meta();
+            meta.iri = iri;
+
+            meta.name = this.getSingleValueOrNull(iri, ULO.name);
+            meta.sourceref = this.getSingleValueOrNull(iri, ULO.sourceref);
+            meta.paratype = this.getSingleValueOrNull(iri, ULO.paratype);
+
+            return meta;
+        };
+
+        return GraphDB.execute(this.serverUrl, this.repository, operation);
+    }
+
+    /**
+     * Given subject and predicate, return the first matching object.
+     *
+     * @return The object as returned by the database, converted to a {@link String}.
+     * If no element was found, this method returns {@code null}.
+     */
+    private String getSingleValueOrNull(IRI subject, IRI predicate) {
+        final GraphDB.Operation<String> operation = (manager, repository, connection) -> {
+            final RepositoryResult<Statement> result = connection.getStatements(subject, predicate, null);
+
+            if (!result.hasNext()) {
+                return null;
+            }
+
+            final Value object = result.next().getObject();
+            return object.stringValue();
+        };
+
+        return GraphDB.execute(this.serverUrl, this.repository, operation);
+    }
 }

src/ulo-storage-applications/src/main/resources/spark/template/freemarker/explore_node.flt

@@ -19,6 +19,30 @@
         </li>
     </ul>
 
+    <h3>Name</h3>
+
+    <ul>
+        <li>
+            <code>${meta.name}</code>
+        </li>
+    </ul>
+
+    <h3>Paragraph Type (<code>ulo:paratype</code>)</h3>
+
+    <ul>
+        <li>
+            <code>${meta.paratype}</code>
+        </li>
+    </ul>
+
+    <h3>Source Reference (<code>ulo:sourceref</code>)</h3>
+
+    <ul>
+        <li>
+            <code>${meta.sourceref}</code>
+        </li>
+    </ul>
+
     <h3>Node uses...</h3>
 
     <ul>