1 files changed, 51 insertions, 0 deletions
diff --git a/app/services/boards/lists/move_service.rb b/app/services/boards/lists/move_service.rb
new file mode 100644
index 00000000000..020ff69f4a7
--- /dev/null
+++ b/app/services/boards/lists/move_service.rb
@@ -0,0 +1,51 @@
+module Boards
+  module Lists
+    class MoveService < Boards::BaseService
+      def execute(list)
+        @old_position = list.position
+        @new_position = params[:position]
+
+        return false unless list.movable?
+        return false unless valid_move?
+
+        list.with_lock do
+          reorder_intermediate_lists
+          update_list_position(list)
+        end
+      end
+
+      private
+
+      attr_reader :old_position, :new_position
+
+      def valid_move?
+        new_position.present? && new_position != old_position &&
+          new_position >= 0 && new_position < board.lists.movable.size
+      end
+
+      def reorder_intermediate_lists
+        if old_position < new_position
+          decrement_intermediate_lists
+        else
+          increment_intermediate_lists
+        end
+      end
+
+      def decrement_intermediate_lists
+        board.lists.movable.where('position > ?',  old_position)
+                           .where('position <= ?', new_position)
+                           .update_all('position = position - 1')
+      end
+
+      def increment_intermediate_lists
+        board.lists.movable.where('position >= ?', new_position)
+                           .where('position < ?',  old_position)
+                           .update_all('position = position + 1')
+      end
+
+      def update_list_position(list)
+        list.update_attribute(:position, new_position)
+      end
+    end
+  end
+end