add new endpoints

app/service/cartsService/cartsService.go

@@ -46,6 +46,10 @@ func (s *CartsService) UpdateCartName(user_id uint, cart_id uint, new_name strin
 	return s.repo.UpdateCartName(user_id, cart_id, new_name)
 }
 
+func (s *CartsService) RetrieveCartsInfo(user_id uint) ([]model.CustomerCart, error) {
+	return s.repo.RetrieveCartsInfo(user_id)
+}
+
 func (s *CartsService) RetrieveCart(user_id uint, cart_id uint) (*model.CustomerCart, error) {
 	amt, err := s.repo.UserHasCart(user_id, cart_id)
 	if err != nil {
@@ -57,3 +61,23 @@ func (s *CartsService) RetrieveCart(user_id uint, cart_id uint) (*model.Customer
 
 	return s.repo.RetrieveCart(user_id, cart_id)
 }
+
+func (s *CartsService) AddProduct(user_id uint, cart_id uint, product_id uint, product_attribute_id *uint, amount uint) error {
+	amt, err := s.repo.UserHasCart(user_id, cart_id)
+	if err != nil {
+		return err
+	}
+	if amt != 1 {
+		return responseErrors.ErrUserHasNoSuchCart
+	}
+
+	amt, err = s.repo.CheckProductExists(product_id, product_attribute_id)
+	if err != nil {
+		return err
+	}
+	if amt != 1 {
+		return responseErrors.ErrProductOrItsVariationDoesNotExist
+	}
+
+	return s.repo.AddProduct(user_id, cart_id, product_id, product_attribute_id, amount)
+}