[tracker/wip/sam/resource: 10/13] libtracker-sparql: Work on JSON-LD serialisation for tracker-resource

[Sam Thursfield <sthursfield src gnome org>]

commit dead010d0c7cfaa3df42792b94d344dca0a63329
Author: Sam Thursfield <sam afuera me uk>
Date:   Thu Apr 7 18:03:00 2016 +0100

    libtracker-sparql: Work on JSON-LD serialisation for tracker-resource

 src/libtracker-sparql/tracker-resource.c |   73 +++++++++++++++++++++++------
 src/libtracker-sparql/tracker-resource.h |    2 +
 2 files changed, 60 insertions(+), 15 deletions(-)
---
diff --git a/src/libtracker-sparql/tracker-resource.c b/src/libtracker-sparql/tracker-resource.c
index 5e2dc59..f964d9b 100644
--- a/src/libtracker-sparql/tracker-resource.c
+++ b/src/libtracker-sparql/tracker-resource.c
@@ -18,6 +18,7 @@
  */
 
 #include <glib.h>
+#include <json-glib/json-glib.h>
 
 #include <string.h>
 
@@ -391,20 +392,62 @@ tracker_resource_identifier_compare_func (TrackerResource *resource,
        return strcmp (priv->identifier, identifier);
 }
 
-GString *
-tracker_resource_print_jsonld_string (TrackerResource *resource)
+
+
+/* FIXME: this could hit an infinite loop if there are circular resource
+ * relationships, make sure those are tested & detected.
+ */
+/* This is not exposed publically right now because then everything including
+ * tracker-resource.h would need to pull in the json-glib dependency ...
+ */
+static JsonNode *
+tracker_resource_serialize_jsonld (TrackerResource *self,
+                                   GError **error)
+{
+       /* FIXME: generate a context ! */
+
+       TrackerResourcePrivate *priv = GET_PRIVATE (self);
+       JsonBuilder *builder;
+       JsonNode *result;
+
+       builder = json_builder_new ();
+       json_builder_begin_object (builder);
+
+       json_builder_set_member_name (builder, "@id");
+       json_builder_add_string_value (builder, priv->identifier);
+
+       json_builder_end_object (builder);
+
+       result = json_builder_get_root (builder);
+       g_object_unref (builder);
+       return result;
+};
+
+
+char *
+tracker_resource_print_jsonld (TrackerResource *self,
+                               GError **error)
 {
-       GString *string;
-
-       string = g_string_new ("");
-
-       /* How will this work then? */
-       /* Ignore formatting for now */
-       /*{
-               @context: {
-                       "foo": "prefix"
-               },
-               "nie:title": title
-       }*/
-       return string;
+       GError *sub_error = NULL;
+       JsonNode *json_root_node;
+       JsonGenerator *generator;
+       char *result;
+
+       json_root_node = tracker_resource_serialize_jsonld (self, &sub_error);
+
+       if (json_root_node == NULL) {
+               g_propagate_error (error, sub_error);
+               return NULL;
+       }
+
+       generator = json_generator_new ();
+       json_generator_set_root (generator, json_root_node);
+       json_generator_set_pretty (generator, TRUE);
+
+       result = json_generator_to_data (generator, NULL);
+
+       g_object_unref (json_root_node);
+       g_object_unref (generator);
+
+       return result;
 }
diff --git a/src/libtracker-sparql/tracker-resource.h b/src/libtracker-sparql/tracker-resource.h
index 162c1ca..7abf6d5 100644
--- a/src/libtracker-sparql/tracker-resource.h
+++ b/src/libtracker-sparql/tracker-resource.h
@@ -63,6 +63,8 @@ const char *tracker_resource_get_first_uri (TrackerResource *self, const char *p
 
 gint tracker_resource_identifier_compare_func (TrackerResource *resource, const char *identifier);
 
+char *tracker_resource_print_jsonld (TrackerResource *self, GError **error);
+
 G_END_DECLS
 
 #endif /* __LIBTRACKER_RESOURCE_H__ */