fix: improve getGameTypes with DISTINCT query and null filtering

controllers/gameController.js

@@ -1,6 +1,7 @@
 const { Game } = require('../models');
 const { cacheUtils } = require('../config/redis');
 const { sequelize } = require('../config/database');
+const { Op, Sequelize } = require('sequelize');
 
 /**
  * Game Controller - Quản lý trò chơi giáo dục
@@ -410,11 +411,22 @@ class GameController {
         });
       }
 
-      // Get distinct types
-      const types = await Game.aggregate('type', 'DISTINCT', { plain: false });
+      // Get all games with only type field
+      const games = await Game.findAll({
+        attributes: [[Sequelize.fn('DISTINCT', Sequelize.col('type')), 'type']],
+        where: {
+          type: {
+            [Op.and]: [
+              { [Op.ne]: null },
+              { [Op.notIn]: ['', ' '] }
+            ]
+          }
+        },
+        raw: true,
+      });
 
-      // Format response as array of objects
-      const result = types.map(t => ({ type: t.type }));
+      // Get distinct types
+      const result = games.filter(g => g.type);
 
       await cacheUtils.set(cacheKey, result, 3600);