Add support for Google Analytics 4

lib/rack/tracker.rb

@@ -13,6 +13,7 @@
 require "rack/tracker/handler_delegator"
 require "rack/tracker/controller"
 require "rack/tracker/google_analytics/google_analytics"
+require "rack/tracker/google_analytics4/google_analytics4"
 require "rack/tracker/google_global/google_global"
 require "rack/tracker/google_tag_manager/google_tag_manager"
 require "rack/tracker/google_adwords_conversion/google_adwords_conversion"

lib/rack/tracker/google_analytics4/google_analytics4.rb

@@ -0,0 +1,41 @@
+class Rack::Tracker::GoogleAnalytics4 < Rack::Tracker::Handler
+
+  self.allowed_tracker_options = [:cookie_domain, :user_id]
+
+  def initialize(env, options = {})
+    super(env, options)
+  end
+
+  class Send < OpenStruct
+    def initialize(attrs = {})
+      attrs.reverse_merge!(type: 'event')
+      super
+    end
+
+    def write
+      ['send', event].to_json.gsub(/\[|\]/, '')
+    end
+
+    def event
+      { hitType: self.type }.merge(attributes.stringify_values).compact
+    end
+
+    def attributes
+      Hash[to_h.slice(:category, :action, :label, :value).map { |k,v| [self.type.to_s + k.to_s.capitalize, v] }]
+    end
+  end
+
+  def tracker
+    options[:tracker].respond_to?(:call) ? options[:tracker].call(env) : options[:tracker]
+  end
+
+  private
+
+  def tracker_option_key(key)
+    key.to_s.camelize(:lower).to_sym
+  end
+
+  def tracker_option_value(value)
+    value.to_s
+  end
+end

lib/rack/tracker/google_analytics4/template/google_analytics4.erb

@@ -0,0 +1,18 @@
+<% if tracker %>
+  <script async src="https://www.googletagmanager.com/gtag/js?id=<%= tracker %>"></script>
+  <script>
+    window.dataLayer = window.dataLayer || [];
+    function gtag(){dataLayer.push(arguments);}
+    gtag('js', new Date());
+
+    gtag('config', "<%= tracker %>");
+  </script>
+
+  <script type="text/javascript">
+    <% events.each do |var| %>
+      gtag('event', "<%= var.category %>", {
+        action: "<%= var.action %>"
+      });
+    <% end %>
+  </script>
+<% end %>