even more refactoring

mutation_initialize_checkout.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+
+	messages "git.tornberg.me/go-cart-actor/proto"
+)
+
+// mutation_initialize_checkout.go
+//
+// Registers the InitializeCheckout mutation.
+// This mutation is invoked AFTER an external Klarna checkout session
+// has been successfully created or updated. It persists the Klarna
+// order reference / status and marks the cart as having a payment in progress.
+//
+// Behavior:
+//   - Sets OrderReference to the Klarna order ID (overwriting if already set).
+//   - Sets PaymentStatus to the current Klarna status.
+//   - Sets / updates PaymentInProgress flag.
+//   - Does NOT alter pricing or line items (so no totals recalculation).
+//
+// Validation:
+//   - Returns an error if payload is nil.
+//   - Returns an error if orderId is empty (integrity guard).
+//
+// Concurrency:
+//   - Relies on upstream mutation serialization for a single grain. If
+//     parallel checkout attempts are possible, add higher-level guards
+//     (e.g. reject if PaymentInProgress already true unless reusing
+//     the same OrderReference).
+func init() {
+	RegisterMutation[messages.InitializeCheckout](
+		"InitializeCheckout",
+		func(g *CartGrain, m *messages.InitializeCheckout) error {
+			if m == nil {
+				return fmt.Errorf("InitializeCheckout: nil payload")
+			}
+			if m.OrderId == "" {
+				return fmt.Errorf("InitializeCheckout: missing orderId")
+			}
+
+			g.OrderReference = m.OrderId
+			g.PaymentStatus = m.Status
+			g.PaymentInProgress = m.PaymentInProgress
+			return nil
+		},
+		// No WithTotals(): monetary aggregates are unaffected.
+	)
+}