fix order queries

lib/templates/order.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Templates
+  module Order
+    module_function
+
+    def call(templates, order)
+      case order
+      when 'used_at'
+        subquery = Submission.select(:template_id, Submission.arel_table[:created_at].maximum.as('created_at'))
+                             .group(:template_id)
+
+        templates = templates.joins(
+          Template.arel_table
+                  .join(subquery.arel.as('submissions'), Arel::Nodes::OuterJoin)
+                  .on(Template.arel_table[:id].eq(Submission.arel_table[:template_id]))
+                  .join_sources
+        )
+
+        templates.order(
+          Arel::Nodes::Case.new
+                           .when(Submission.arel_table[:created_at].gt(Template.arel_table[:updated_at]))
+                           .then(Submission.arel_table[:created_at])
+                           .else(Template.arel_table[:updated_at])
+                           .desc
+        )
+      when 'name'
+        templates.order(name: :asc)
+      else
+        templates.order(id: :desc)
+      end
+    end
+  end
+end