Getting a list of available user types by a users type

gistfile1.rb

class User
    def user_type
      "system_admin"
    end
  
    def self.user_types_for user
      types = []
      case user.user_type
      when "system_admin"
          types << "system_admin"
          types << "admin"
          types << "case_worker"
          types << "staff"
          types << "student"
      when "admin"
          types << "admin"
          types << "case_worker"
          types << "staff"
          types << "student"
      when "case_worker"
          types << "student"
      when "staff"
          types << "case_worker"
          types << "student"
      when "student"
          types << "student"
      end
      types
    end
end

User.user_types_for User.new