rack middleware to append mixpanel scripts

lib/mixpanel.rb

@@ -1 +1,2 @@
 require 'mixpanel/mixpanel'
+require 'mixpanel/middleware'

lib/mixpanel/middleware.rb

@@ -0,0 +1,61 @@
+require 'rack'
+
+class Middleware
+  def initialize(app, mixpanel_token)
+    @app = app
+    @token = mixpanel_token
+  end
+
+  def call(env)
+    status, headers, response = @app.call(env)
+
+    if is_html?(headers)
+      response = build_response(response)
+      headers = update_content_length(response, headers)
+    end
+
+    [status, headers, response]
+  end
+
+  def each(&block)
+    @response.each(&block)
+  end
+
+  private
+
+  def build_response(response)
+    body = ""
+
+    response.each do |part|
+      part.gsub!("</head>", "#{include_mixpanel_scripts}</head>")
+      body << part
+    end
+  end
+
+  def update_content_length(response, headers)
+    headers.merge("Content-Length" => response.join("").length.to_s)
+  end
+
+  def is_html?(headers)
+    headers["Content-Type"].include?("text/html") if headers.has_key?("Content-Type")
+  end
+
+  def include_mixpanel_scripts
+    <<-EOT
+      <script type='text/javascript'>
+        var mp_protocol = (('https:' == document.location.protocol) ? 'https://' : 'http://');
+        document.write(unescape('%3Cscript src="' + mp_protocol + 'api.mixpanel.com/site_media/js/api/mixpanel.js" type="text/javascript"%3E%3C/script%3E'));
+      </script>
+      <script type='text/javascript'>
+        try {
+          var mpmetrics = new MixpanelLib('#{@token}');
+        } catch(err) {
+          null_fn = function () {};
+          var mpmetrics = {
+            track: null_fn,  track_funnel: null_fn,  register: null_fn,  register_once: null_fn, register_funnel: null_fn
+          };
+        }
+      </script>
+    EOT
+  end
+end

mixpanel.gemspec

@@ -1,3 +1,5 @@
+files = ['README.rdoc', 'LICENSE', 'Rakefile', 'mixpanel.gemspec', '{spec,lib}/**/*'].map {|f| Dir[f]}.flatten
+
 spec = Gem::Specification.new do |s|
   s.name = "mixpanel"
   s.version = "0.5.1"
@@ -8,20 +10,14 @@ spec = Gem::Specification.new do |s|
   s.homepage = "http://cuboxsa.com"
   s.platform = Gem::Platform::RUBY
   s.summary = "Supports direct request api and javascript requests."
-  s.files = %w[
-    .gitignore
-    README.rdoc
-    LICENSE
-    Rakefile
-    mixpanel.gemspec
-    lib/mixpanel.rb
-    spec/spec_helper.rb
-    spec/mixpanel/mixpanel_spec.rb
-  ]
+  s.files = files
   s.require_path = "lib"
   s.has_rdoc = false
   s.extra_rdoc_files = ["README.rdoc"]
   s.add_dependency 'json'
+  s.add_dependency 'rack'
   s.add_development_dependency 'rspec'
+  s.add_development_dependency 'rack/test'
   s.add_development_dependency 'fakeweb'
+  s.add_development_dependency 'nokogiri'
 end

spec/mixpanel/middleware_spec.rb

@@ -0,0 +1,39 @@
+require 'spec_helper'
+
+describe Middleware do
+  include Rack::Test::Methods
+
+  describe "Dummy apps, no text/html" do
+    before do
+      setup_rack_application(DummyApp)
+      get "/"
+    end
+
+    it "should pass through if the document is not text/html content type" do
+      last_response.body.should == DummyApp.new.body
+    end
+  end
+
+  describe "Appending mixpanel scripts" do
+    before do
+      setup_rack_application(HtmlApp)
+      get "/"
+    end
+
+    it "should append mixpanel scripts to head element" do
+      Nokogiri::HTML(last_response.body).search('head script').should_not be_empty
+    end
+
+    it "should use the specified token instantiating mixpanel lib" do
+      last_response.should =~ /new MixpanelLib\('#{MIX_PANEL_TOKEN}'\)/
+    end
+
+    it "should define Content-Length if not exist" do
+      last_response.headers.has_key?("Content-Length").should == true
+    end
+
+    it "should update Content-Length in headers" do
+      last_response.headers["Content-Length"].should_not == HtmlApp.new.body.length
+    end
+  end
+end

spec/spec_helper.rb

@@ -1,5 +1,8 @@
 require File.join(File.dirname(__FILE__), "../lib", "mixpanel")
+require 'rack/test'
 require 'fakeweb'
+require 'nokogiri'
+Dir[File.expand_path(File.join(File.dirname(__FILE__),'support','**','*.rb'))].each {|f| require f}
 
 MIX_PANEL_TOKEN = "e2d8b0bea559147844ffab3d607d26a6"
 

spec/support/rack_apps.rb

@@ -0,0 +1,30 @@
+def setup_rack_application(application)
+  stub!(:app).and_return(Middleware.new(application.new, MIX_PANEL_TOKEN))
+end
+
+class HtmlApp
+  def body
+    <<-EOT
+      <html>
+        <head>
+        </head>
+        <body>
+        </body>
+      </html>
+    EOT
+  end
+
+  def call(env)
+    ["200", {"Content-Type" => "text/html"}, [body]]
+  end
+end
+
+class DummyApp
+  def body
+    ""
+  end
+
+  def call(env)
+    ["200", {}, [body]]
+  end
+end