feat: fix stock check and add admin order status update

backend/internal/api/handlers/order.go

@@ -278,11 +278,13 @@ func (h *OrderHandler) Create(c *gin.Context) {
 		}
 
 		var inventory models.Inventory
-		if err := utils.DB.Where("product_id = ?", cart.ProductID).First(&inventory).Error; err == nil {
-			if inventory.Quantity < cart.Quantity {
-				c.JSON(http.StatusBadRequest, gin.H{"error": "Insufficient stock for " + cart.Product.Name})
-				return
-			}
+		if err := utils.DB.Where("product_id = ?", cart.ProductID).First(&inventory).Error; err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "No inventory record for " + cart.Product.Name})
+			return
+		}
+		if inventory.Quantity < cart.Quantity {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "Insufficient stock for " + cart.Product.Name + ". Available: " + strconv.Itoa(inventory.Quantity)})
+			return
 		}
 
 		subtotal += cart.Product.Price * float64(cart.Quantity)
@@ -723,3 +725,52 @@ func (h *OrderHandler) ConfirmReceipt(c *gin.Context) {
 	utils.DB.Model(&order).Update("status", models.OrderStatusCompleted)
 	c.JSON(http.StatusOK, gin.H{"message": "Order confirmed successfully"})
 }
+
+func (h *OrderHandler) AdminUpdateStatus(c *gin.Context) {
+	id, _ := strconv.Atoi(c.Param("id"))
+
+	var order models.Order
+	if err := utils.DB.First(&order, id).Error; err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Order not found"})
+		return
+	}
+
+	var req struct {
+		Status         string `json:"status" binding:"required"`
+		TrackingNumber string `json:"tracking_number"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	validStatuses := []string{
+		models.OrderStatusPendingPayment,
+		models.OrderStatusPendingConfirm,
+		models.OrderStatusPendingShip,
+		models.OrderStatusShipped,
+		models.OrderStatusCompleted,
+		models.OrderStatusRefunding,
+		models.OrderStatusRefunded,
+		models.OrderStatusCancelled,
+	}
+	valid := false
+	for _, s := range validStatuses {
+		if s == req.Status {
+			valid = true
+			break
+		}
+	}
+	if !valid {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid status"})
+		return
+	}
+
+	updates := map[string]interface{}{"status": req.Status}
+	if req.TrackingNumber != "" {
+		updates["tracking_number"] = req.TrackingNumber
+	}
+
+	utils.DB.Model(&order).Updates(updates)
+	c.JSON(http.StatusOK, gin.H{"message": "Order status updated successfully"})
+}