module Rubaidh # :nodoc:
  module GoogleAnalyticsMixin
    def google_analytics_code
      GoogleAnalytics.google_analytics_code(request.ssl?) if GoogleAnalytics.enabled?(request.format)
    end
    
    # An after_filter to automatically add the analytics code.
    # Add the code at the top of the page to support calls to _trackPageView 
    #   (see http://www.google.com/support/googleanalytics/bin/answer.py?answer=55527&topic=11006)
    def add_google_analytics_code
      response.body.sub! '</body>', "#{google_analytics_code}</body>" if response.body.respond_to?(:sub!)
    end
  end

  class GoogleAnalyticsConfigurationError < StandardError; end

  class GoogleAnalytics
    # Specify the Google Analytics ID for this web site.  This can be found
    # as the value of +_uacct+ in the Javascript excerpt
    @@tracker_id = nil
    cattr_accessor :tracker_id

    # Specify a different domain name from the default.  You'll want to use
    # this if you have several subdomains that you want to combine into
    # one report.  See the Google Analytics documentation for more
    # information.
    @@domain_name = nil
    cattr_accessor :domain_name

    # Specify whether the legacy Google Analytics code should be used.
    @@legacy_mode = false
    cattr_accessor :legacy_mode
    
    # I can't see why you'd want to do this, but you can always change the
    # analytics URL.  This is only applicable in legacy mode.
    @@analytics_url = 'http://www.google-analytics.com/urchin.js'
    cattr_accessor :analytics_url

    # I can't see why you'd want to do this, but you can always change the
    # analytics URL (ssl version).  This is only applicable in legacy mode.
    @@analytics_ssl_url = 'https://ssl.google-analytics.com/urchin.js'
    cattr_accessor :analytics_ssl_url

    # The environments in which to enable the Google Analytics code.  Defaults
    # to 'production' only.
    @@environments = ['production']
    cattr_accessor :environments
    
    # The formats for which to add.  Defaults
    # to :html only.
    @@formats = [:html]
    cattr_accessor :formats

    # Return true if the Google Analytics system is enabled and configured
    # correctly for the specified format
    def self.enabled?(format)
      raise Rubaidh::GoogleAnalyticsConfigurationError if tracker_id.blank? || analytics_url.blank?
      environments.include?(RAILS_ENV) && formats.include?(format.to_sym)
    end
    
    def self.google_analytics_code(ssl = false)
      return legacy_google_analytics_code(ssl) if legacy_mode

      extra_code = domain_name.blank? ? nil : "pageTracker._setDomainName(\"#{domain_name}\");"

      code = <<-HTML
      <script type="text/javascript">
      var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
      document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
      </script>
      <script type="text/javascript">
      <!--//--><![CDATA[//><!--
      var pageTracker = _gat._getTracker('#{tracker_id}');
      #{extra_code}
      pageTracker._initData();
      pageTracker._trackPageview();
      //--><!]]>
      </script>
      HTML
    end

    # Run the legacy version of the Google Analytics code.
    def self.legacy_google_analytics_code(ssl = false)
      extra_code = domain_name.blank? ? nil : "_udn = \"#{domain_name}\";"
      url = ssl ? analytics_ssl_url : analytics_url

      code = <<-HTML
      <script src="#{url}" type="text/javascript">
      </script>
      <script type="text/javascript">
      _uacct = "#{tracker_id}";
      #{extra_code}
      urchinTracker();
      </script>
      HTML
    end
  end
end