class Policy
  class << self
    def rename_attributes(&block)
      @root ||= {}
      @block = block
    end

    def mapped_attributes
      instance_eval(&@block)
      @root
    end

    def rename(from:, to:, &attribues_block)
      children = instance_eval(&attribues_block) if block_given?
      @root[from] = {
        to: to,
        children: children,
      }
      @root
    end

    def delegates_renaming_to(policy_klass)
      policy_klass.mapped_attributes
    end
  end
end

class StockGroupPolicy < Policy
  rename_attributes do
    rename from: :batch, to: :stock_group_attributes
    rename from: :batch_id, to: :stock_group_id
  end
end

class StockAdjustmentLineItemPolicy < Policy
  rename_attributes do
    rename from: :stock_trails, to: :stock_trails_attrs do
      delegates_renaming_to StockGroupPolicy
    end
  end
end

class StockAdjustmentPolicy < Policy
  rename_attributes do
    rename from: :stock_adjustment_line_items, to: :stock_adjustment_line_items_attrs do
      delegates_renaming_to StockAdjustmentLineItemPolicy
    end
  end
end



StockAdjustmentPolicy.mapped_attributes