Disallow adding arbitrary weapons to Extra slots

app/controllers/api/v1/api_controller.rb

@@ -20,6 +20,7 @@ module Api
       rescue_from Api::V1::FavoriteAlreadyExistsError, with: :render_unprocessable_entity_response
       rescue_from Api::V1::NoJobProvidedError, with: :render_unprocessable_entity_response
       rescue_from Api::V1::TooManySkillsOfTypeError, with: :render_unprocessable_entity_response
+      rescue_from Api::V1::IncompatibleWeaponForPositionError, with: :render_unprocessable_entity_response
       rescue_from Api::V1::UnauthorizedError, with: :render_unauthorized_response
       rescue_from ActionController::ParameterMissing, with: :render_unprocessable_entity_response
 

app/controllers/api/v1/grid_weapons_controller.rb

@@ -16,6 +16,10 @@ module Api
         # Set up conflict_position in case it is used
         conflict_position = nil
 
+        if [9, 10, 11].include?(weapon_params[:position].to_i) && ![11, 16, 17, 28, 29].include?(incoming_weapon.series)
+          raise Api::V1::IncompatibleWeaponForPositionError.new(weapon: incoming_weapon)
+        end
+
         # 1. If the weapon has a limit
         # 2. If the weapon does not match a weapon already in grid
         # 3. If the incoming weapon has a limit and other weapons of the same series are in grid

app/errors/api/v1/incompatible_weapon_for_position_error.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Api
+  module V1
+    class IncompatibleWeaponForPositionError < GranblueError
+      def http_status
+        422
+      end
+
+      def code
+        'incompatible_weapon_for_position'
+      end
+
+      def message
+        'A weapon of this series cannot be added to Additional Weapons'
+      end
+
+      def to_hash
+        {
+          message: message,
+          code: code,
+          weapon: @data[:weapon]
+        }
+      end
+    end
+  end
+end