filter bangs by categories

app/lib/features/bangs/data/database/database.drift

@@ -90,4 +90,27 @@ bangQuery WITH BangData:
     bang_icon bi ON b."trigger" = bi."trigger"
   ORDER BY
     RANK,
-    bf.frequency NULLS LAST;
+    bf.frequency NULLS LAST;
+
+categoriesJson:
+  WITH categories AS (
+    SELECT 
+      b.category, 
+      json_group_array(
+        DISTINCT b.sub_category 
+        ORDER BY b.sub_category
+      ) AS sub_categories
+    FROM 
+      bang b 
+    WHERE 
+      b.category IS NOT NULL AND 
+      b.sub_category IS NOT NULL
+    GROUP BY b.category
+    ORDER BY b.category
+  )
+  SELECT 
+    json_group_object(
+      c.category, 
+      json(c.sub_categories)
+    ) AS categories_json
+  FROM categories c;

app/lib/features/bangs/data/database/database.g.dart

@@ -1094,6 +1094,15 @@ abstract class _$BangDatabase extends GeneratedDatabase {
         ));
   }
 
+  Selectable<String> categoriesJson() {
+    return customSelect(
+        'WITH categories AS (SELECT b.category, json_group_array(DISTINCT b.sub_category ORDER BY b.sub_category)AS sub_categories FROM bang AS b WHERE b.category IS NOT NULL AND b.sub_category IS NOT NULL GROUP BY b.category ORDER BY b.category) SELECT json_group_object(c.category, json(c.sub_categories)) AS categories_json FROM categories AS c',
+        variables: [],
+        readsFrom: {
+          bang,
+        }).map((QueryRow row) => row.read<String>('categories_json'));
+  }
+
   @override
   Iterable<TableInfo<Table, Object?>> get allTables =>
       allSchemaEntities.whereType<TableInfo<Table, Object?>>();