From afa79e7b56cea0651559f1afd7fc6d40404f55bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mats=20T=C3=B6rnberg?= <mats@tornberg.me>
Date: Wed, 26 Nov 2025 21:35:40 +0100
Subject: [PATCH] handle limited quantity

---
 pkg/cart/mutation_add_item.go            | 18 +++++++++++++-----
 pkg/cart/mutation_change_quantity.go     | 13 ++++++++++---
 pkg/cart/mutation_initialize_checkout.go |  9 +++++++++
 3 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/pkg/cart/mutation_add_item.go b/pkg/cart/mutation_add_item.go
index 9b36436..0e188e3 100644
--- a/pkg/cart/mutation_add_item.go
+++ b/pkg/cart/mutation_add_item.go
@@ -38,16 +38,24 @@ func AddItem(g *CartGrain, m *messages.AddItem) error {
 		if !sameStore {
 			continue
 		}
-		existing.Quantity += int(m.Quantity)
+		if m.ReservationEndTime != nil {
+			t := m.ReservationEndTime.AsTime()
+			if existing.ReservationEndTime == nil || existing.ReservationEndTime.Before(m.ReservationEndTime.AsTime()) {
+				existing.ReservationEndTime = &t
+				existing.Quantity = int(m.Quantity)
+			} else {
+				existing.ReservationEndTime = &t
+			}
+
+		} else {
+			existing.Quantity += int(m.Quantity)
+		}
 		existing.Stock = uint16(m.Stock)
 		// If existing had nil store but new has one, adopt it.
 		if existing.StoreId == nil && m.StoreId != nil {
 			existing.StoreId = m.StoreId
 		}
-		if m.ReservationEndTime != nil {
-			t := m.ReservationEndTime.AsTime()
-			existing.ReservationEndTime = &t
-		}
+
 		return nil
 	}
 
diff --git a/pkg/cart/mutation_change_quantity.go b/pkg/cart/mutation_change_quantity.go
index de627ae..70e7efa 100644
--- a/pkg/cart/mutation_change_quantity.go
+++ b/pkg/cart/mutation_change_quantity.go
@@ -48,8 +48,15 @@ func ChangeQuantity(g *CartGrain, m *messages.ChangeQuantity) error {
 		g.UpdateTotals()
 		return nil
 	}
-
-	g.Items[foundIndex].Quantity = int(m.Quantity)
-	g.UpdateTotals()
+	item := g.Items[foundIndex]
+	if item == nil {
+		return fmt.Errorf("ChangeQuantity: item id %d not found", m.Id)
+	}
+	if item.ReservationEndTime != nil {
+		return fmt.Errorf("ChangeQuantity: cannot change quantity of reserved item id %d", m.Id)
+	} else {
+		item.Quantity = int(m.Quantity)
+		g.UpdateTotals()
+	}
 	return nil
 }
diff --git a/pkg/cart/mutation_initialize_checkout.go b/pkg/cart/mutation_initialize_checkout.go
index 0e3a14f..83ebff7 100644
--- a/pkg/cart/mutation_initialize_checkout.go
+++ b/pkg/cart/mutation_initialize_checkout.go
@@ -2,6 +2,7 @@ package cart
 
 import (
 	"fmt"
+	"time"
 
 	messages "git.k6n.net/go-cart-actor/pkg/messages"
 )
@@ -36,6 +37,14 @@ func InitializeCheckout(g *CartGrain, m *messages.InitializeCheckout) error {
 	if m.OrderId == "" {
 		return fmt.Errorf("InitializeCheckout: missing orderId")
 	}
+	now := time.Now()
+	for _, item := range g.Items {
+		if item.ReservationEndTime != nil {
+			if now.After(*item.ReservationEndTime) {
+				return fmt.Errorf("InitializeCheckout: item id %d reservation has expired", item.Id)
+			}
+		}
+	}
 
 	g.OrderReference = m.OrderId
 	g.PaymentStatus = m.Status