Add void action to Taler for refunds

app/mailers/payment_mailer.rb

@@ -26,4 +26,17 @@ class PaymentMailer < ApplicationMailer
            reply_to: @order.email)
     end
   end
+
+  def refund_available(payment, taler_order_status_url)
+    @order = payment.order
+    @taler_order_status_url = taler_order_status_url
+
+    subject = I18n.t("spree.payment_mailer.refund_available.subject",
+                     order: @order)
+    I18n.with_locale valid_locale(@order.user) do
+      mail(to: @order.email,
+           subject:,
+           reply_to: @order.email)
+    end
+  end
 end

app/models/spree/payment_method/taler.rb

@@ -21,6 +21,14 @@ module Spree
       preference :backend_url, :string
       preference :api_key, :password
 
+      def actions
+        %w{void}
+      end
+
+      def can_void?(payment)
+        payment.state == "completed"
+      end
+
       # Name of the view to display during checkout
       def method_type
         "check" # empty view
@@ -60,6 +68,25 @@ module Spree
         ActiveMerchant::Billing::Response.new(success, message)
       end
 
+      def void(response_code, gateway_options)
+        payment = gateway_options[:payment]
+        taler_order = taler_order(id: response_code)
+        status = taler_order.fetch("order_status")
+
+        if status == "claimed"
+          return ActiveMerchant::Billing::Response.new(true, "Already expired")
+        end
+
+        raise "Unsupported action" if status != "paid"
+
+        amount = taler_order.fetch("contract_terms")["amount"]
+        taler_order.refund(refund: amount, reason: "void")
+
+        PaymentMailer.refund_available(payment, taler_order.status_url).deliver_later
+
+        ActiveMerchant::Billing::Response.new(true, "Refund initiated")
+      end
+
       private
 
       def load_payment(order)

app/views/payment_mailer/refund_available.html.haml

@@ -0,0 +1,2 @@
+%p= t("spree.payment_mailer.refund_available.message", order_number: @order.number)
+%p= link_to @taler_order_status_url, @taler_order_status_url

config/locales/en.yml

@@ -4930,6 +4930,9 @@ en:
       authorization_required:
         subject: "A payment requires authorization from the customer"
         message: "A payment for order %{order_number} requires additional authorization from the customer. The customer has been notified via email and the payment will appear as pending until it is authorized."
+      refund_available:
+        subject: "Refund available"
+        message: "Your payment for order %{order_number} is being refunded. Claim your refund following the link below."
     shipment_mailer:
       shipped_email:
         dear_customer: "Dear Customer,"

spec/mailers/payment_mailer_spec.rb

@@ -40,4 +40,16 @@ RSpec.describe PaymentMailer do
       end
     end
   end
+
+  describe "#refund_available" do
+    it "tells the user to accept a refund" do
+      payment = create(:payment)
+      link = "https://taler.example.com/order/1"
+      mail = PaymentMailer.refund_available(payment, link)
+
+      expect(mail.subject).to eq "Refund available"
+      expect(mail.body).to match "Claim your refund following the link below."
+      expect(mail.body).to match link
+    end
+  end
 end

spec/models/spree/payment_method/taler_spec.rb

@@ -49,4 +49,50 @@ RSpec.describe Spree::PaymentMethod::Taler do
       expect(response.message).to eq "The payment request expired. Please try again."
     end
   end
+
+  describe "#void" do
+    let(:order_endpoint) { "#{backend_url}/private/orders/taler-order-8" }
+    let(:refund_endpoint) { "#{order_endpoint}/refund" }
+    let(:taler_refund_uri) {
+      "taler://refund/backend.demo.taler.net/instances/sandbox/taler-order-8/"
+    }
+
+    it "starts the refund process" do
+      order_status = {
+        order_status: "paid",
+        contract_terms: {
+          amount: "KUDOS:2",
+        }
+      }
+      stub_request(:get, order_endpoint).to_return(body: order_status.to_json)
+      stub_request(:post, refund_endpoint).to_return(body: { taler_refund_uri: }.to_json)
+      order = create(:completed_order_with_totals)
+      order.payments.create(
+        amount: order.total, state: :completed,
+        payment_method: taler,
+        response_code: "taler-order-8",
+      )
+      expect {
+        response = taler.void("taler-order-8", { payment: order.payments[0] })
+        expect(response.success?).to eq true
+      }.to enqueue_mail(PaymentMailer, :refund_available)
+    end
+
+    it "returns early if payment already void" do
+      order_status = {
+        order_status: "claimed",
+      }
+      stub_request(:get, order_endpoint).to_return(body: order_status.to_json)
+      order = create(:completed_order_with_totals)
+      order.payments.create(
+        amount: order.total, state: :completed,
+        payment_method: taler,
+        response_code: "taler-order-8",
+      )
+      expect {
+        response = taler.void("taler-order-8", { payment: order.payments[0] })
+        expect(response.success?).to eq true
+      }.not_to enqueue_mail
+    end
+  end
 end