Moves all transaction logic to a PORO's business class

app/controllers/preorder_controller.rb

@@ -9,28 +9,9 @@ def checkout
 
   def prefill
     @user = User.find_or_create_by(:email => params[:email])
-
-    if Settings.use_payment_options
-      payment_option_id = params['payment_option']
-      raise Exception.new("No payment option was selected") if payment_option_id.nil?
-      payment_option = PaymentOption.find(payment_option_id)
-      price = payment_option.amount
-    else
-      price = Settings.price
-    end
-
-    @order = Order.prefill!(:name => Settings.product_name, :price => price, :user_id => @user.id, :payment_option => payment_option)
-
-    # This is where all the magic happens. We create a multi-use token with Amazon, letting us charge the user's Amazon account
-    # Then, if they confirm the payment, Amazon POSTs us their shipping details and phone number
-    # From there, we save it, and voila, we got ourselves a preorder!
-    port = Rails.env.production? ? "" : ":3000"
-    callback_url = "#{request.scheme}://#{request.host}#{port}/preorder/postfill"
-    redirect_to AmazonFlexPay.multi_use_pipeline(@order.uuid, callback_url,
-                                                 :transaction_amount => price,
-                                                 :global_amount_limit => price + Settings.charge_limit,
-                                                 :collect_shipping_address => "True",
-                                                 :payment_reason => Settings.payment_description)
+    redirect_to Transaction.new(user: @user,
+                                payment_option: params['payment_option'],
+                                request: request).amazon_flex_play
   end
 
   def postfill

app/services/payment_option_checker.rb

@@ -0,0 +1,26 @@
+class PaymentOptionChecker
+
+  def initialize(payment_option_id)
+    @payment_option_id = payment_option_id
+  end
+
+  def price
+    if use_payment_options?
+      payment_option.try(:amount)
+    else
+      Settings.price
+    end
+  end
+
+  def payment_option
+      PaymentOption.find(payment_option_id)
+      raise Exception.new("No payment option was selected") if payment_option.nil?
+    end
+  end
+
+
+private
+  def use_payment_options?
+    Settings.use_payment_options
+  end
+end

app/services/transaction.rb

@@ -0,0 +1,31 @@
+class Transaction
+
+  attr_reader :user, :request, :payment_option_checker, :price
+  def initialize(options = {})
+    @payment_option_checker = PaymentOptionChecker.new(options.fetch(:payment_option))
+    @price = payment_option_checker.price
+    @user = options.fetch(:user)
+    @request = options.fetch(:request)
+  end
+
+  def order
+    Order.prefill!(:name => Settings.product_name, :price => price,
+                   :user_id => user.id, :payment_option => payment_option_checker.payment_option)
+  end
+
+  def port
+    Rails.env.production? ? "" : ":3000"
+  end
+
+  def callback_url
+    "#{request.scheme}://#{request.host}#{port}/preorder/postfill"
+  end
+
+  def amazon_flex_play
+    AmazonFlexPay.multi_use_pipeline(order.uuid, callback_url,
+                                     :transaction_amount => price,
+                                     :global_amount_limit => price + Settings.charge_limit,
+                                     :collect_shipping_address => "True",
+                                     :payment_reason => Settings.payment_description)
+  end
+end