Paypal IPN integration in about 30 lines of Sinatra.

gistfile1.diff

diff --git a/app/account.rb b/app/account.rb
index a108685..c89ad34 100644
--- a/app/account.rb
+++ b/app/account.rb
@@ -1,4 +1,22 @@
+require 'open-uri'
+
 module Sol
+  class Url
+    def self.get(url)
+      open(url).read
+    end
+  end
+
+  class PaypalVerifier
+    def initialize(query)
+      @query = query
+    end
+    def verified?
+      url = "https://www.paypal.com/cgi-bin/webscr?cmd=_notify-validate&#{@query}"
+      Url.get(url) == "VERIFIED"
+    end
+  end
+
   class AccountApp < Sinatra::Application
     get '/?' do
       env['warden'].authenticate!
@@ -26,6 +44,18 @@ module Sol
       redirect '/'
     end
 
+    post '/ipn/?' do
+      return "FAILED VERIFICATION" unless (PaypalVerifier.new(request.env["rack.input"].read).verified?)
+      return "PAYMENT NOT COMPLETE" unless (params[:payment_status] == 'Completed')
+      if (@account = Account.where(:username => params[:option_selection1]).first)
+        @account.update_attribute(:purchased_at, Time.now)
+        Pony.mail(:to => @account.email, :subject => "Your Sol Trader account is activated", :body => erb(:activation_email, :layout => false))
+        "OK"
+      else
+        "NOT FOUND"
+      end
+    end
+
     post '/purchased' do
       if params[:secret] == Build::SECRET
         @account = Account.where(:username => params[:username]).first
diff --git a/spec/integration/recording_purchase_spec.rb b/spec/integration/recording_purchase_spec.rb
index 8380889..debb21e 100644
--- a/spec/integration/recording_purchase_spec.rb
+++ b/spec/integration/recording_purchase_spec.rb
@@ -40,3 +40,56 @@ describe "Recording purchases" do
     post '/purchased', :username => 'username', :secret => Build::SECRET
   end
 end
+
+describe "Paypal IPN" do
+  include Rack::Test::Methods
+
+  def app
+    Sol::AccountApp
+  end
+
+  let(:fields) {{
+    :email => 'foo@example.com',
+    :password => 'password',
+    :password_confirmation => 'password',
+    :username => 'username'
+  }}
+
+  before do
+    Account.create!(fields)
+    Pony.stub(:mail)
+    Sol::Url.stub(:get => "VERIFIED")
+  end
+
+  it "verifies that the paypal address is genuine" do
+    Sol::Url.should_receive(:get).with("https://www.paypal.com/cgi-bin/webscr?cmd=_notify-validate&test=ipn_query_string").and_return("VERIFIED")
+    post '/ipn', :test => 'ipn_query_string'
+  end
+
+  it "doesn't do anything if the account does not verify" do
+    Sol::Url.stub(:get => "INVALID")
+    post '/ipn', 'ipn_query_string'
+    Account.first.should_not be_game_owner
+    Pony.should_not_receive(:mail)
+  end
+
+  it "records purchases for usernames" do
+    post '/ipn', :option_selection1 => fields[:username], :payment_status => "Completed"
+    Account.first.should be_game_owner
+  end
+
+  it "does not record purchases for unknown username" do
+    post '/ipn', :option_selection1 => 'unknown'
+    Account.first.should_not be_game_owner
+  end
+
+  it "does not record purchases unless the payment_status is Completed" do
+    post '/ipn', :option_selection1 => fields[:username]
+    Account.first.should_not be_game_owner
+  end
+
+  it "sends email to the purchaser" do
+    Pony.should_receive(:mail).with(hash_including(:to => Account.first.email))
+    post '/ipn', :option_selection1 => fields[:username], :payment_status => "Completed"
+  end
+end
diff --git a/views/account.erb b/views/account.erb
index c478f26..7eface2 100644
--- a/views/account.erb
+++ b/views/account.erb
@@ -68,6 +68,7 @@
     <input type="hidden" name="no_shipping" value="1">
     <input type="hidden" name="rm" value="1">
     <input type="hidden" name="return" value="http://soltrader.net/success">
+    <input type="hidden" name="notify_url" value="http://soltrader.net/account/ipn">
     <input type="hidden" name="bn" value="PP-BuyNowBF:btn_buynow_LG.gif:NonHosted">
     <input type="image" src="https://www.paypalobjects.com/en_GB/i/btn/btn_buynow_LG.gif" border="0" name="submit" alt="PayPal — The safer, easier way to pay online.">
     <img alt="" border="0" src="https://www.paypalobjects.com/en_GB/i/scr/pixel.gif" width="1" height="1">