Extract checkout step(s) validation to a service

app/controllers/split_checkout_controller.rb

@@ -68,7 +68,7 @@ class SplitCheckoutController < ::BaseController
 
   def confirm_order
     return unless summary_step? && @order.confirmation?
-    return unless validate_summary! && @order.errors.empty?
+    return unless validate_current_step
 
     @order.customer.touch :terms_and_conditions_accepted_at
 
@@ -102,9 +102,11 @@ class SplitCheckoutController < ::BaseController
     @order.update(order_params)
     @order.update_totals_and_states
 
-    validate_current_step!
+    validate_current_step
+  end
 
-    @order.errors.empty?
+  def validate_current_step
+    Checkout::Validation.new(@order, params).call && @order.errors.empty?
   end
 
   def use_shipping_address_from_distributor
@@ -136,31 +138,6 @@ class SplitCheckoutController < ::BaseController
     OrderWorkflow.new(@order).advance_checkout(raw_params.slice(:shipping_method_id))
   end
 
-  def validate_current_step!
-    step = ([params[:step]] & ["details", "payment", "summary"]).first
-    send("validate_#{step}!")
-  end
-
-  def validate_details!
-    return true if params[:shipping_method_id].present?
-
-    @order.errors.add :shipping_method, I18n.t('split_checkout.errors.select_a_shipping_method')
-  end
-
-  def validate_payment!
-    return true if params.dig(:order, :payments_attributes, 0, :payment_method_id).present?
-    return true if @order.zero_priced_order?
-
-    @order.errors.add :payment_method, I18n.t('split_checkout.errors.select_a_payment_method')
-  end
-
-  def validate_summary!
-    return true if params[:accept_terms]
-    return true unless TermsOfService.required?(@order.distributor)
-
-    @order.errors.add(:terms_and_conditions, t("split_checkout.errors.terms_not_accepted"))
-  end
-
   def order_params
     @order_params ||= Checkout::Params.new(@order, params, spree_current_user).call
   end

app/services/checkout/validation.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Checkout
+  class Validation
+    def initialize(order, params)
+      @params = params
+      @order = order
+    end
+
+    def call
+      __send__ "validate_#{current_step}"
+    end
+
+    private
+
+    attr_reader :order, :params
+
+    def current_step
+      ([params[:step]] & ["details", "payment", "summary"]).first
+    end
+
+    def validate_details
+      return true if params[:shipping_method_id].present?
+
+      order.errors.add :shipping_method, I18n.t('split_checkout.errors.select_a_shipping_method')
+    end
+
+    def validate_payment
+      return true if params.dig(:order, :payments_attributes, 0, :payment_method_id).present?
+      return true if order.zero_priced_order?
+
+      order.errors.add :payment_method, I18n.t('split_checkout.errors.select_a_payment_method')
+    end
+
+    def validate_summary
+      return true if params[:accept_terms]
+      return true unless TermsOfService.required?(order.distributor)
+
+      order.errors.add(:terms_and_conditions, I18n.t("split_checkout.errors.terms_not_accepted"))
+    end
+  end
+end