[tracker/wip/carlosg/serialize-api: 9/19] cli: Use serialize() method for "tracker3 export" command

[Carlos Garnacho <carlosg src gnome org>]

commit 823fbd868de85ce9380aeb302d1e05a5ac3a3dc6
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Nov 21 19:30:40 2021 +0100

    cli: Use serialize() method for "tracker3 export" command
    
    Use this new TrackerSparqlConnection method to extract data from a
    SPARQL endpoint.

 src/tracker/tracker-export.c | 96 ++++++++++++++++++++------------------------
 1 file changed, 44 insertions(+), 52 deletions(-)
---
diff --git a/src/tracker/tracker-export.c b/src/tracker/tracker-export.c
index 38c05f941..84b70754c 100644
--- a/src/tracker/tracker-export.c
+++ b/src/tracker/tracker-export.c
@@ -26,6 +26,7 @@
 
 #include <glib.h>
 #include <glib/gi18n.h>
+#include <gio/gunixoutputstream.h>
 
 #include "tracker-sparql.h"
 #include "tracker-color.h"
@@ -136,15 +137,6 @@ format_urn (GHashTable  *prefixes,
        return urn_out;
 }
 
-/* print a URI prefix in Turtle format */
-static void
-print_prefix (gpointer key,
-              gpointer value,
-              gpointer user_data)
-{
-       g_print ("@prefix %s: <%s#> .\n", (gchar *) value, (gchar *) key);
-}
-
 /* Print triples in Turtle format */
 static void
 print_turtle (TrackerSparqlCursor *cursor,
@@ -291,14 +283,38 @@ print_keyfile (TrackerSparqlCursor *cursor)
        g_print ("%s\n", data);
 }
 
+static void
+serialize_cb (GObject      *object,
+              GAsyncResult *res,
+              gpointer      user_data)
+{
+       GInputStream *istream;
+       GOutputStream *ostream;
+       GError *error = NULL;
+
+       istream = tracker_sparql_connection_serialize_finish (TRACKER_SPARQL_CONNECTION (object),
+                                                             res, &error);
+       if (istream) {
+               ostream = g_unix_output_stream_new (STDOUT_FILENO, FALSE);
+               g_output_stream_splice (ostream, istream, G_OUTPUT_STREAM_SPLICE_NONE, NULL, &error);
+               g_output_stream_close (ostream, NULL, NULL);
+               g_object_unref (ostream);
+       }
+
+       if (error)
+               g_printerr ("%s\n", error ? error->message : _("No error given"));
+
+       g_object_unref (istream);
+       g_main_loop_quit (user_data);
+}
+
 static int
 export_run_default (void)
 {
        g_autoptr(TrackerSparqlConnection) connection = NULL;
-       g_autoptr(TrackerSparqlCursor) cursor = NULL;
        g_autoptr(GError) error = NULL;
-       g_autoptr(GHashTable) prefixes = NULL;
        g_autoptr(GString) query = NULL;
+       g_autoptr(GMainLoop) loop = NULL;
        guint i;
 
        connection = create_connection (&error);
@@ -310,56 +326,32 @@ export_run_default (void)
                return EXIT_FAILURE;
        }
 
-       prefixes = tracker_sparql_get_prefixes (connection);
-
-       query = g_string_new (NULL);
-       g_string_append (query,
-                        "SELECT ?g ?u ?p ?v "
-                        "       (EXISTS { ?p rdfs:range [ rdfs:subClassOf rdfs:Resource ] }) AS ?is_resource 
"
-                        "{ "
-                        "    GRAPH ?g { "
-                        "        ?u ?p ?v ");
+       query = g_string_new ("DESCRIBE ");
 
        if (iris) {
-               g_string_append (query, "FILTER (?u IN (");
-
-               for (i = 0; iris[i]; i++) {
-                       if (i != 0)
-                               g_string_append_c (query, ',');
-                       g_string_append_printf (query, "<%s>", iris[i]);
-               }
-
-               g_string_append (query, "))");
+               for (i = 0; iris[i] != NULL; i++)
+                       g_string_append_printf (query, "<%s> ", iris[i]);
        } else {
                g_string_append (query,
-                                "FILTER NOT EXISTS { ?u a rdf:Property } "
-                                "FILTER NOT EXISTS { ?u a rdfs:Class } "
-                                "FILTER NOT EXISTS { ?u a nrl:Namespace } ");
-       }
-
-       g_string_append (query,
-                        "    } "
-                        "} ORDER BY ?g ?u");
-
-       cursor = tracker_sparql_connection_query (connection, query->str, NULL, &error);
-
-       if (error) {
-               g_printerr ("%s, %s\n",
-                           _("Could not run query"),
-                           error->message);
-               return EXIT_FAILURE;
+                                "?u {"
+                                "  ?u a rdfs:Resource . "
+                                "  FILTER NOT EXISTS { ?u a rdf:Property } "
+                                "  FILTER NOT EXISTS { ?u a rdfs:Class } "
+                                "  FILTER NOT EXISTS { ?u a nrl:Namespace } "
+                                "}");
        }
 
        tracker_term_pipe_to_pager ();
 
-       g_hash_table_foreach (prefixes, (GHFunc) print_prefix, NULL);
-       g_print ("\n");
+       loop = g_main_loop_new (NULL, FALSE);
 
-       if (show_graphs) {
-               print_trig (cursor, prefixes, FALSE);
-       } else {
-               print_turtle (cursor, prefixes, FALSE);
-       }
+       tracker_sparql_connection_serialize_async (connection,
+                                                  show_graphs ?
+                                                  TRACKER_RDF_FORMAT_TRIG :
+                                                  TRACKER_RDF_FORMAT_TURTLE,
+                                                  query->str,
+                                                  NULL, serialize_cb, loop);
+       g_main_loop_run (loop);
 
        tracker_term_pager_close ();