Add failed payment email to StandingOrderMailer

app/mailers/standing_order_mailer.rb

@@ -21,6 +21,11 @@ class StandingOrderMailer < Spree::BaseMailer
     send_mail(order)
   end
 
+  def failed_payment_email(order)
+    @order = order
+    send_mail(order)
+  end
+
   private
 
   def send_mail(order)

app/views/standing_order_mailer/failed_payment_email.html.haml

@@ -0,0 +1,20 @@
+= render 'header', intro: t("email_so_failed_payment_intro_html")
+
+%p.callout
+  = t("email_so_failed_payment_explainer_html", distributor: @order.distributor.name)
+  = t("email_so_edit_false_html",
+    orders_close_at: l(@order.order_cycle.orders_close_at, format: "%a %b %d @ %l:%M%p"),
+    order_url: spree.order_url(@order))
+  = t("email_so_contact_distributor_html", distributor: @order.distributor.name, email: @order.distributor.email)
+
+- if @order.errors.any?
+  %p  
+  %h4
+    = t :email_confirm_customer_number_html, number: @order.number
+  %p
+    = t("email_so_failed_payment_details_html", distributor: @order.distributor.name)
+    - @order.errors.full_messages.each do |message|
+      = message
+      %br
+
+= render 'spree/order_mailer/signoff'

config/locales/en.yml

@@ -1234,6 +1234,9 @@ See the %{link} to find out more about %{sitename}'s features and to start using
   email_so_empty_intro_html: "We tried to place a new order with <strong>%{distributor}</strong>, but had some problems..."
   email_so_empty_explainer_html: "Unfortunately, none of products that you ordered were available, so no order has been placed. The original quantities that you requested appear crossed-out below."
   email_so_empty_details_html: "Here are the details of the unplaced order for <strong>%{distributor}</strong>:"
+  email_so_failed_payment_intro_html: "We tried to process a payment, but had some problems..."
+  email_so_failed_payment_explainer_html: "The payment for your subscription with <strong>%{distributor}</strong> failed because of a problem with your credit card. <strong>%{distributor}</strong> has been notified of this failed payment."
+  email_so_failed_payment_details_html: "Here are the details of the failure provided by the payment gateway:"
   email_shipping_delivery_details: Delivery details
   email_shipping_delivery_time: "Delivery on:"
   email_shipping_delivery_address: "Delivery address:"

spec/mailers/standing_order_mailer_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe StandingOrderMailer do
+  include ActionView::Helpers::SanitizeHelper
+
   let!(:mail_method) { create(:mail_method, preferred_mails_from: 'spree@example.com') }
 
   describe "order placement" do
@@ -77,4 +79,28 @@ describe StandingOrderMailer do
       expect(body).to include "Unfortunately, none of products that you ordered were available"
     end
   end
+
+  describe "failed payment notification" do
+    let(:standing_order) { create(:standing_order, with_items: true) }
+    let(:proxy_order) { create(:proxy_order, standing_order: standing_order) }
+    let!(:order) { proxy_order.initialise_order! }
+
+    before do
+      order.errors.add(:base, "This is a payment failure error")
+
+      expect do
+        StandingOrderMailer.failed_payment_email(order).deliver
+      end.to change{StandingOrderMailer.deliveries.count}.by(1)
+    end
+
+    it "sends the email" do
+      body = strip_tags(StandingOrderMailer.deliveries.last.body.encoded)
+      expect(body).to include I18n.t("email_so_failed_payment_intro_html")
+      explainer = I18n.t("email_so_failed_payment_explainer_html", distributor: standing_order.shop.name)
+      expect(body).to include strip_tags(explainer)
+      details = I18n.t("email_so_failed_payment_details_html", distributor: standing_order.shop.name)
+      expect(body).to include strip_tags(details)
+      expect(body).to include "This is a payment failure error"
+    end
+  end
 end