Extract params handling to service

app/controllers/split_checkout_controller.rb

@@ -56,7 +56,7 @@ class SplitCheckoutController < ::BaseController
   end
 
   def update_order
-    return unless params[:order]
+    return if @order.errors.any?
 
     @order.update(order_params) && advance_order_state
   end
@@ -79,37 +79,7 @@ class SplitCheckoutController < ::BaseController
   end
 
   def order_params
-    return @order_params unless @order_params.nil?
-
-    @order_params = params.require(:order).permit(
-      :email, :shipping_method_id, :special_instructions,
-      bill_address_attributes: PermittedAttributes::Address.attributes,
-      ship_address_attributes: PermittedAttributes::Address.attributes,
-      payments_attributes: [:payment_method_id]
-    )
-
-    set_address_details
-    set_payment_amount
-
-    @order_params
-  end
-
-  def set_address_details
-    return unless @order_params[:ship_address_attributes] && @order_params[:bill_address_attributes]
-
-    if params[:ship_address_same_as_billing]
-      @order_params[:ship_address_attributes] = @order_params[:bill_address_attributes]
-    else
-      @order_params[:ship_address_attributes][:firstname] = @order_params[:bill_address_attributes][:firstname]
-      @order_params[:ship_address_attributes][:lastname] = @order_params[:bill_address_attributes][:lastname]
-      @order_params[:ship_address_attributes][:phone] = @order_params[:bill_address_attributes][:phone]
-    end
-  end
-
-  def set_payment_amount
-    return unless @order_params[:payments_attributes]
-
-    @order_params[:payments_attributes].first[:amount] = @order.total
+    @order_params ||= Checkout::Params.new(@order, params).call
   end
 
   def redirect_to_step

app/services/checkout/params.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module Checkout
+  class Params
+    def initialize(order, params)
+      @params = params
+      @order = order
+    end
+
+    def call
+      return {} unless params[:order]
+
+      apply_strong_parameters
+      set_address_details
+      set_payment_amount
+
+      @order_params
+    end
+
+    private
+
+    attr_reader :params, :order
+
+    def apply_strong_parameters
+      @order_params = params.require(:order).permit(
+        :email, :shipping_method_id, :special_instructions,
+        bill_address_attributes: ::PermittedAttributes::Address.attributes,
+        ship_address_attributes: ::PermittedAttributes::Address.attributes,
+        payments_attributes: [:payment_method_id]
+      )
+    end
+
+    def set_address_details
+      return unless addresses_present?
+
+      if params[:ship_address_same_as_billing]
+        set_ship_address_from_bill_address
+      else
+        set_basic_details
+      end
+    end
+
+    def set_payment_amount
+      return unless @order_params[:payments_attributes]
+
+      @order_params[:payments_attributes].first[:amount] = order.total
+    end
+
+    def addresses_present?
+      @order_params[:ship_address_attributes] && @order_params[:bill_address_attributes]
+    end
+
+    def set_ship_address_from_bill_address
+      @order_params[:ship_address_attributes] = @order_params[:bill_address_attributes]
+    end
+
+    def set_basic_details
+      [:firstname, :lastname, :phone].each do |attr|
+        @order_params[:ship_address_attributes][attr] = @order_params[:bill_address_attributes][attr]
+      end
+    end
+  end
+end