refine luasnip binds

lua/conf/plugins/luasnip.lua

@@ -28,15 +28,27 @@ return { 'L3MON4D3/LuaSnip',
       },
     }
 
-    map({"i", "s"}, { "<C-e>", "<C-a>" }, function()
+    map({"i", "s"}, "<c-a>", function()
       if luasnip.choice_active() then
         luasnip.change_choice(1)
       end
     end)
 
+    map({"i", "s"}, "<c-e>", function()
+      if luasnip.expandable() then
+        luasnip.expand()
+      end
+    end)
+
+    map({"i", "s"}, "<C-j>", function()
+      if luasnip.jumpable(1) then
+        luasnip.jump(1)
+      end
+    end)
+
     map({"i", "s"}, "<C-k>", function()
-      if luasnip.expandable(-1) then
-        luasnip.expand(-1)
+      if luasnip.jumpable(-1) then
+        luasnip.jump(-1)
       end
     end)