Add GET /api/stats/summary -> .gravity.last_update timestamp exposing the last gravity update via the API

Signed-off-by: DL6ER <dl6er@dl6er.de>

src/api/docs/content/specs/stats.yaml

@@ -560,6 +560,10 @@ components:
               type: integer
               description: Number of domain on your Pi-hole's gravity list
               example: 104756
+            last_update:
+              type: integer
+              description: Unix timestamp of last gravity update (may be `0` if unknown)
+              example: 1725194639
     upstreams:
       type: object
       properties:

src/api/stats.c

@@ -165,6 +165,7 @@ int api_stats_summary(struct ftl_conn *api)
 
 	cJSON *gravity = JSON_NEW_OBJECT();
 	JSON_ADD_NUMBER_TO_OBJECT(gravity, "domains_being_blocked", num_gravity);
+	JSON_ADD_NUMBER_TO_OBJECT(gravity, "last_update", gravity_last_updated());
 
 	cJSON *json = JSON_NEW_OBJECT();
 	JSON_ADD_ITEM_TO_OBJECT(json, "queries", queries);

src/database/gravity-db.c

@@ -2796,3 +2796,8 @@ bool gravity_updated(void)
 
 	return changed;
 }
+
+time_t __attribute__((pure)) gravity_last_updated(void)
+{
+	return last_updated > 0 ? (time_t)last_updated : 0;
+}

src/database/gravity-db.h

@@ -70,4 +70,6 @@ bool gravityDB_delFromTable(const enum gravity_list_type listtype, const cJSON*
 bool gravityDB_edit_groups(const enum gravity_list_type listtype, cJSON *groups,
                            const tablerow *row, const char **message);
 
+time_t gravity_last_updated(void) __attribute__((pure));
+
 #endif //GRAVITY_H