module ActiveAdmin::Settings::ClassMethods

def default_settings
  @default_settings ||= {}
end

def deprecated_setting(name, default, message = nil)
  setting(name, default)
  message ||= "The #{name} setting is deprecated and will be removed."
  ActiveAdmin::Deprecation.deprecate self,     name,    message
  ActiveAdmin::Deprecation.deprecate self, :"#{name}=", message
end

def setting(name, default)
  default_settings[name] = default
  attr_writer name
  # Creates a reader that will grab the default if no value has been set.
  class_eval <<-EOC, __FILE__, __LINE__ + 1
    def #{name}
      if instance_variable_defined? :@#{name}
        @#{name}
      else
        read_default_setting(:#{name})
      end
    end
  EOC
end