[tracker/wip/sam/resource: 9/13] Groundwork for tracker-extract JSON output

[Sam Thursfield <sthursfield src gnome org>]

commit 3c611dc1a84fa5e55b27115f0395bec9d06b9307
Author: Sam Thursfield <sam afuera me uk>
Date:   Thu Apr 7 17:30:56 2016 +0100

    Groundwork for tracker-extract JSON output

 configure.ac                          |    6 ++++--
 src/libtracker-common/tracker-enums.h |   10 ++++++++++
 src/tracker-extract/tracker-extract.c |    7 ++++---
 src/tracker-extract/tracker-extract.h |    7 ++++---
 src/tracker-extract/tracker-main.c    |   19 ++++++++++++++++++-
 src/tracker/tracker-extract.c         |   14 +++++++++++---
 6 files changed, 51 insertions(+), 12 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index bcf676f..10729fe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -237,6 +237,7 @@ GSTREAMER_REQUIRED=0.10.31
 GUPNP_DLNA_REQUIRED=0.9.4
 LIBPNG_REQUIRED=0.89
 LIBMEDIAART_REQUIRED=1.9.0
+JSON_GLIB_REQUIRED=1.0.4
 
 # 3.6.11 for sqlite_backup API
 # 3.6.16 to fix test failures
@@ -321,8 +322,9 @@ LIBTRACKER_CONTROL_REQUIRED="glib-2.0        >= $GLIB_REQUIRED
 PKG_CHECK_MODULES(LIBTRACKER_CONTROL, [$LIBTRACKER_CONTROL_REQUIRED])
 
 # Check requirements for libtracker-sparql
-LIBTRACKER_SPARQL_REQUIRED="glib-2.0     >= $GLIB_REQUIRED
-                            gio-unix-2.0 >= $GLIB_REQUIRED
+LIBTRACKER_SPARQL_REQUIRED="glib-2.0      >= $GLIB_REQUIRED
+                            gio-unix-2.0  >= $GLIB_REQUIRED
+                            json-glib-1.0 >= $JSON_GLIB_REQUIRED
                             uuid"
 
 PKG_CHECK_MODULES(LIBTRACKER_SPARQL, [$LIBTRACKER_SPARQL_REQUIRED])
diff --git a/src/libtracker-common/tracker-enums.h b/src/libtracker-common/tracker-enums.h
index 3fd43d9..edce490 100644
--- a/src/libtracker-common/tracker-enums.h
+++ b/src/libtracker-common/tracker-enums.h
@@ -35,6 +35,16 @@ typedef enum {
        TRACKER_SCHED_IDLE_NEVER,
 } TrackerSchedIdle;
 
+typedef enum {
+       /* JSON and JSON_LD are treated as the same thing right now, but that
+        * could theoretically change, and it's nice to be able to use either
+        * 'json' or 'json-ld' with `tracker extract --output-format=` and such.
+        */
+       TRACKER_SERIALIZATION_FORMAT_JSON,
+       TRACKER_SERIALIZATION_FORMAT_JSON_LD,
+       TRACKER_SERIALIZATION_FORMAT_SPARQL,
+} TrackerSerializationFormat;
+
 G_END_DECLS
 
 #endif /* __TRACKER_ENUMS_H__ */
diff --git a/src/tracker-extract/tracker-extract.c b/src/tracker-extract/tracker-extract.c
index 04b3291..9ff3c31 100644
--- a/src/tracker-extract/tracker-extract.c
+++ b/src/tracker-extract/tracker-extract.c
@@ -762,9 +762,10 @@ tracker_extract_get_media_art_process (TrackerExtract *extract)
 #endif
 
 void
-tracker_extract_get_metadata_by_cmdline (TrackerExtract *object,
-                                         const gchar    *uri,
-                                         const gchar    *mime)
+tracker_extract_get_metadata_by_cmdline (TrackerExtract             *object,
+                                         const gchar                *uri,
+                                         const gchar                *mime,
+                                         TrackerSerializationFormat  output_format)
 {
        GError *error = NULL;
        TrackerExtractPrivate *priv;
diff --git a/src/tracker-extract/tracker-extract.h b/src/tracker-extract/tracker-extract.h
index 704ece4..b1f0aa1 100644
--- a/src/tracker-extract/tracker-extract.h
+++ b/src/tracker-extract/tracker-extract.h
@@ -81,9 +81,10 @@ void            tracker_extract_dbus_start              (TrackerExtract
 void            tracker_extract_dbus_stop               (TrackerExtract         *extract);
 
 /* Not DBus API */
-void            tracker_extract_get_metadata_by_cmdline (TrackerExtract         *object,
-                                                         const gchar            *path,
-                                                         const gchar            *mime);
+void            tracker_extract_get_metadata_by_cmdline (TrackerExtract             *object,
+                                                         const gchar                *path,
+                                                         const gchar                *mime,
+                                                         TrackerSerializationFormat  output_format);
 
 G_END_DECLS
 
diff --git a/src/tracker-extract/tracker-main.c b/src/tracker-extract/tracker-main.c
index 2c8ecd8..0baf9cd 100644
--- a/src/tracker-extract/tracker-main.c
+++ b/src/tracker-extract/tracker-main.c
@@ -72,6 +72,7 @@ static gint verbosity = -1;
 static gchar *filename;
 static gchar *mime_type;
 static gchar *force_module;
+static gchar *output_format_name;
 static gboolean version;
 
 static TrackerConfig *config;
@@ -94,6 +95,9 @@ static GOptionEntry entries[] = {
          G_OPTION_ARG_STRING, &force_module,
          N_("Force a module to be used for extraction (e.g. \"foo\" for \"foo.so\")"),
          N_("MODULE") },
+       { "output-format", 'o', 0, G_OPTION_ARG_STRING, &output_format_name,
+         N_("Output results format: 'json' or 'sparql'"),
+         N_("FORMAT") },
        { "version", 'V', 0,
          G_OPTION_ARG_NONE, &version,
          N_("Displays version information"),
@@ -241,6 +245,9 @@ run_standalone (TrackerConfig *config)
        TrackerExtract *object;
        GFile *file;
        gchar *uri;
+       GEnumClass *enum_class;
+       GEnumValue *enum_value;
+       TrackerSerializationFormat output_format;
 
        /* Set log handler for library messages */
        g_log_set_default_handler (log_handler, NULL);
@@ -250,6 +257,16 @@ run_standalone (TrackerConfig *config)
                verbosity = 3;
        }
 
+       /* Look up the output format by name */
+       enum_class = g_type_class_ref (TRACKER_TYPE_SERIALIZATION_FORMAT);
+       enum_value = g_enum_get_value_by_nick (enum_class, output_format_name);
+       g_type_class_unref (enum_class);
+       if (!enum_value) {
+               g_printerr (N_("Unsupported serialization format '%s'\n"), output_format_name);
+               return EXIT_FAILURE;
+       }
+       output_format = enum_value->value;
+
        tracker_locale_init ();
 
        /* This makes sure we don't steal all the system's resources */
@@ -268,7 +285,7 @@ run_standalone (TrackerConfig *config)
                return EXIT_FAILURE;
        }
 
-       tracker_extract_get_metadata_by_cmdline (object, uri, mime_type);
+       tracker_extract_get_metadata_by_cmdline (object, uri, mime_type, output_format);
 
        g_object_unref (object);
        g_object_unref (file);
diff --git a/src/tracker/tracker-extract.c b/src/tracker/tracker-extract.c
index d4979f3..5f5b838 100644
--- a/src/tracker/tracker-extract.c
+++ b/src/tracker/tracker-extract.c
@@ -30,6 +30,7 @@
 #include "tracker-config.h"
 #include "tracker-extract.h"
 
+static gchar *output_format = "json-ld";
 static gchar *verbosity;
 static gchar **filenames;
 
@@ -37,6 +38,9 @@ static gchar **filenames;
        ((filenames && g_strv_length (filenames) > 0))
 
 static GOptionEntry entries[] = {
+       { "output-format", 'o', 0, G_OPTION_ARG_STRING, &output_format,
+         N_("Output results format: 'json' or 'sparql'"),
+         N_("FORMAT") },
        { "verbosity", 'v', 0, G_OPTION_ARG_STRING, &verbosity,
          N_("Sets the logging verbosity to LEVEL ('debug', 'detailed', 'minimal', 'errors') for all 
processes"),
          N_("LEVEL") },
@@ -48,7 +52,8 @@ static GOptionEntry entries[] = {
 
 
 static gint
-extract_files (TrackerVerbosity verbosity)
+extract_files (TrackerVerbosity verbosity,
+               char *output_format)
 {
        char **p;
        char *tracker_extract_path;
@@ -60,7 +65,10 @@ extract_files (TrackerVerbosity verbosity)
        tracker_extract_path = g_build_filename(LIBEXECDIR, "tracker-extract", NULL);
 
        for (p = filenames; *p; p++) {
-               char *argv[] = {tracker_extract_path, "--verbosity", verbosity_str, "--file", *p, NULL};
+               char *argv[] = {tracker_extract_path,
+                               "--output-format", output_format,
+                               "--verbosity", verbosity_str,
+                               "--file", *p, NULL };
 
                g_spawn_sync(NULL, argv, NULL, G_SPAWN_DEFAULT, NULL, NULL, NULL, NULL, NULL, &error);
 
@@ -99,7 +107,7 @@ extract_run (void)
                }
        }
 
-       return extract_files (verbosity_level);
+       return extract_files (verbosity_level, output_format);
 }
 
 static int