Only credit back allowed amount

When a payment is cancelled, previously it would attempt to return the
whole amount to the store credit even if it had been entirely or
partially refunded.

core/app/models/spree/payment_method/store_credit.rb

@@ -58,12 +58,16 @@ def credit(amount_in_cents, auth_code, gateway_options = {})
         currency = gateway_options[:currency] || store_credit.currency
         originator = gateway_options[:originator]
 
-        store_credit.credit(
-          amount_in_cents / 100.0.to_d,
-          auth_code,
-          currency,
-          action_originator: originator
-        ) if amount_in_cents > 0
+        if amount_in_cents > 0
+          store_credit.credit(
+            ::Money.new(amount_in_cents, currency).to_d,
+            auth_code,
+            currency,
+            action_originator: originator
+          )
+        else
+          ActiveMerchant::Billing::Response.new(true, '')
+        end
       end
 
       handle_action(action, :credit, auth_code)
@@ -76,8 +80,12 @@ def cancel(auth_code)
       if store_credit_event.nil? || store_credit.nil?
         ActiveMerchant::Billing::Response.new(false, '', {}, {})
       elsif store_credit_event.capture_action?
-        amount_in_cents = (store_credit_event.amount * 100).round
-        credit(amount_in_cents, auth_code)
+        amount = if store_credit_event.originator_type == 'Spree::Payment'
+          store_credit_event.originator.credit_allowed_money.cents
+        else
+          (store_credit_event.amount * 100).round
+        end
+        credit(amount, auth_code, { originator: store_credit_event.originator })
       elsif store_credit_event.authorization_action?
         void(auth_code)
       else

core/spec/models/spree/payment_method/store_credit_spec.rb

@@ -218,6 +218,19 @@
       end
     end
 
+    context "when attempting to credit for zero" do
+      let(:credit_amount) { 0 }
+
+      it "does not credit the store credit" do
+        expect_any_instance_of(Spree::StoreCredit).to_not receive(:credit)
+        subject
+      end
+
+      it "returns a success response" do
+        expect(subject.success?).to be true
+      end
+    end
+
     context "when the store credit isn't credited successfully" do
       before { allow_any_instance_of(Spree::StoreCredit).to receive_messages(credit: false) }
 
@@ -263,19 +276,34 @@
     end
 
     context "capture event found" do
-      let!(:store_credit_event) {
-        create(:store_credit_capture_event,
-                                        authorization_code: auth_code,
-                                        amount: captured_amount,
-                                        store_credit: store_credit)
-      }
+      let!(:store_credit_event) do
+        create(
+          :store_credit_capture_event,
+          authorization_code: auth_code,
+          amount: captured_amount,
+          store_credit: store_credit,
+          originator: originator
+        )
+      end
+      let(:payment) { create(:payment, order: order, amount: 5) }
+      let(:originator) { nil }
 
       it_behaves_like "a spree payment method"
 
-      it "refunds the capture amount" do
-        expect { subject }.to change{ store_credit.reload.amount_remaining }.
-                              from(original_amount - captured_amount).
-                              to(original_amount)
+      context "when originator is nil" do
+        it "refunds the event amount" do
+          expect { subject }.to change{ store_credit.reload.amount_remaining }.
+            from(90).to(100)
+        end
+      end
+
+      context "when the originator is the payment" do
+        let(:originator) { payment }
+
+        it "refunds the payment credit allowed amount" do
+          expect { subject }.to change{ store_credit.reload.amount_remaining }.
+            from(90).to(95)
+        end
       end
     end