Ruby PayPal example

config.ru

require 'sinatra/base'

module PaypalSample
  class App < Sinatra::Base
    get "/" do
      @business_name = ""
      @login = "[email protected]"
      @amount = "1.00"
      @return_url = ""
      @cancel_url = ""
      @currency_code = "USD"
      @tax = nil
      @header_image = "" # 750 px wide, 90px tall
      
      %{<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="POST">
  <p>
    <b>business:</b> #{@business_name}<br/>
    <b>amount:</b> #{@amount}<br/>
  </p>

  <input type="hidden" name="business" value="#{@login}">
  <input type="hidden" name="amount" value="#{@amount}">
  <!--<input type="hidden" name="cmd" value="_ext-enter">-->
  <input type="hidden" name="cmd" value="_notify-validate">
  <input type="hidden" name="redirect_cmd" value="_xclick">
  <input type="hidden" name="return" value="#{@return_url}">
  <input type="hidden" name="cancel_return" value="#{@cancel_url}">
  <input type="hidden" name="currency_code" value="#{@currency_code}">
  <input type="hidden" name="cpp_header_image" value="#{@header_image}">
  #{%{<input type="hidden" name="cart_tax" value="#{@tax}">} unless @tax.nil?}

  <input type="submit">
</form>}
    end
    
    get("/receive_ipn") { recieve_ipn }
    post("/receive_ipn") { recieve_ipn }
    
    private
    
    def cart_item name, amount, tax = nil
      @i ||= 0
      
      str = %{<input type="hidden" name="item_#{@i}" value="#{name}">} +
      %{<input type="hidden" name="amount_#{@i}" value="#{amount}">}
      
      str += %{<input type="hidden" name="tax_#{@i}" value="#{tax}">} unless tax.nil?
    end
    
    def receive_ipn
      verify_ipn params[:raw_post]
    end
    
    def verify_ipn raw
      uri = URI.parse("http://www.sandbox.paypal.com/cgi-bin/webscr")
      status = nil
      
      Net::HTTP.start(uri.host, uri.port) do |request|
        status = request.post(uri.path, @raw + "&cmd=_notify-validate").body
      end
      
      puts "status = '#{status}'"
      status == "VERIFIED"
    end
  end
end

run PaypalSample::App.new