module ActiveModel
  module ValidationsRepairHelper
    extend ActiveSupport::Concern

    module Toolbox
      def self.record_validations(*model_classes)
        model_classes.inject({}) do |repair, klass|
          repair[klass] ||= {}
          [:validate, :validate_on_create, :validate_on_update].each do |callback|
            the_callback = klass.instance_variable_get("@#{callback.to_s}_callbacks")
            repair[klass][callback] = (the_callback.nil? ? nil : the_callback.dup)
          end
          repair
        end
      end

      def self.reset_validations(recorded)
        recorded.each do |klass, repairs|
          [:validate, :validate_on_create, :validate_on_update].each do |callback|
            klass.instance_variable_set("@#{callback.to_s}_callbacks", repairs[callback])
          end
        end
      end
    end

    module ClassMethods
      def repair_validations(*model_classes)
        setup do
          @validation_repairs = Toolbox.record_validations(*model_classes)
        end
        teardown do
          Toolbox.reset_validations(@validation_repairs)
        end
      end
    end

    def repair_validations(*model_classes, &block)
      validation_repairs = Toolbox.record_validations(*model_classes)
      return block.call
    ensure
      Toolbox.reset_validations(validation_repairs)
    end
  end
end