session.rb

require "md5"

module VkontakteAuthentication
  module Session

    def self.included(klass)
      klass.class_eval do
        extend Config
        include InstanceMethods
        
        after_destroy :destroy_vkontakte_cookies
        validate :validate_by_vk_cookie, :if => :authenticating_with_vkontakte?
      end
    end

    class NotInitializedError < StandardError
    end

    module Config
      def find_by_vk_id_method(value = nil)
        rw_config(:find_by_vk_id_method, value, "find_by_vk_id")
      end
      alias_method :find_by_vk_id_method=, :find_by_vk_id_method

      def vk_id_field(value = nil)
        rw_config(:vk_id_field, value, :vk_id)
      end
      alias_method :vk_id_field=, :vk_id_field
    end

    module InstanceMethods
      private
      def credentials=(value)
        super
        cookies = value.is_a?(Array) ? value.first : value
        if record_class.vkontakte_enabled_value && cookies && cookies[VK_APP_COOKIE]
          @vk_cookies = CGI::parse(cookies[VK_APP_COOKIE])
        end
      end

      def authenticating_with_vkontakte?
        record_class.vkontakte_enabled_value && @vk_cookies
      end

      def validate_by_vk_cookie
        result = "expire=%smid=%ssecret=%ssid=%s%s" % [@vk_cookies['expire'], @vk_cookies['mid'], @vk_cookies['secret'], @vk_cookies['sid'], VK_APP_PASSWORD]
        if MD5.md5(result).to_s == @vk_cookies['sig'].to_s
          raise(NotInitializedError, "You must define vk_id column in your User model") unless record_class.respond_to? find_by_vk_id_method
          mid_cookie = @vk_cookies['mid'].first
          possible_record = search_for_record(find_by_vk_id_method, mid_cookie)
          if possible_record.nil?
            possible_record = record_class.new
            possible_record.send "#{vk_id_field}=", mid_cookie
            possible_record.send :persistence_token=, Authlogic::Random.hex_token if possible_record.respond_to? :persistence_token=
            possible_record.send :save, false
          end
          self.attempted_record = possible_record
        end
      end

      def find_by_vk_id_method
        self.class.find_by_vk_id_method
      end

      def vk_id_field
        self.class.vk_id_field
      end

      def record_class
        self.class.klass
      end

      def destroy_vkontakte_cookies
        controller.cookies.delete VK_APP_COOKIE
      end
    end

  end
end