ActiveMerchant and PayPal

gistfile1.rb

# controller

  def notify
    order = Order.capture_payment(request.raw_post)
    render :nothing => true
  end

# Order model

  def self.capture_payment(raw_post)
    notify = Paypal::Notification.new(raw_post)
    order = Order.find(notify.invoice)
    if order
      if notify.acknowledge
        begin
          if notify.complete?
            order.pay!
          else
            order.fail!
          end
        rescue => e
          order.fail!
        end
      end
      order.save
      order
    end
  end

# payment form

= form_tag ActiveMerchant::Billing::Integrations::Paypal.service_url do
  = hidden_field_tag "business", paypal_account

  = hidden_field_tag "cancel_return", "http://" + request.host + "/orders/cancel"
  = hidden_field_tag "notify_url", "http://" + request.host + "/hosted_payment/notify"
  = hidden_field_tag "return", "http://" + request.host + paid_order_path(@cart_order, :key => @cart_order.key)
    
  = hidden_field_tag "redirect_cmd", "_xclick"
  = hidden_field_tag "cmd", "_cart"
  = hidden_field_tag "upload", 1

  = hidden_field_tag "charset", "utf-8"

  = hidden_field_tag "currency_code", Forge::Settings[:currency]
  = hidden_field_tag "invoice", invoice_number_for_paypal(order)
  = hidden_field_tag "tax_cart", order.tax
  - if MySettings.use_coupons
    = hidden_field_tag "discount_amount_cart", order.discount
  = hidden_field_tag "item_name", "Order #{invoice_number_for_paypal(order)}"
  = hidden_field_tag "handling_cart", order.shipping_and_handling

  - i = 1
  - order.line_items.each do |item|
    = hidden_field_tag "item_name_#{i}", item.product.title
    = hidden_field_tag "amount_#{i}", item.price
    = hidden_field_tag "quantity_#{i}", item.quantity
    = hidden_field_tag "tax_#{i}", 0
    - i += 1

  = hidden_field_tag "no_note", 0
  = hidden_field_tag "no_shipping", 2

  = submit_tag 'Pay With Paypal', :class => "order-button"