fix: min quantity for add products to cart should be 1

- existing products in cart should have their quantity modified when added again to cart

backend/src/controllers/cart.controller.ts

@@ -26,15 +26,22 @@ class CartController {
       }
 
       const user = await userRepo.findUserById(req.user.userId);
-      const productInCart = user?.cart?.find((item: any) => item.product.toString() === productId);
       const stock = product.available_quantity ?? 0;
+      const productInCart = user?.cart?.find((item: any) => item.product.toString() === productId);
 
-      if (productInCart) {
-        throw new Error('Product already in cart');
+      if (stock < quantity || quantity <= 0) {
+        throw new Error('Product not available in the requested quantity');
       }
 
-      if (stock < quantity) {
-        throw new Error('Product not available in the requested quantity');
+      if (productInCart) {
+        const updatedUser = await CartRepo.updateProductQuantity(req.user.userId, productId, quantity);
+
+        res.status(ResponseStatusCodes.CREATED).json({
+          message: 'Product quantity updated successfully',
+          cart: updatedUser?.cart,
+        });
+
+        return;
       }
 
       const updatedUser = await CartRepo.addProductToCart(req.user.userId, productId, quantity);

backend/src/database/repositories/cart.repo.ts

@@ -16,6 +16,14 @@ class CartRepo {
     return await User.findByIdAndUpdate(userId, { $push: { cart: cartItem } }, { new: true });
   }
 
+  async updateProductQuantity(userId: string, productId: string, quantity: number) {
+    return await User.findOneAndUpdate(
+      { _id: userId, 'cart.product': productId },
+      { $set: { 'cart.$.quantity': quantity } },
+      { new: true }
+    );
+  }
+
   async removeProductFromCart(userId: string, productId: string) {
     return await User.findByIdAndUpdate(userId, { $pull: { cart: { product: productId } } }, { new: true });
   }