im using react-hook-form in nextjs, now, i have two buttons

<Button
  disabled={form.formState.isSubmitting}
  size="sm"
>
  <ShoppingBagIcon className="mr-1.5 h-3.5 w-3.5" />
  Buy Now
</Button>
<Button
  disabled={form.formState.isSubmitting}
  size="sm"
  variant="outline"
>
  <ShoppingCartIcon className="mr-1.5 h-3.5 w-3.5" />
  Add to Cart
</Button>

and here's my onSubmit function

async function onSubmit(data: z.infer<typeof schema>) {
    const variant = variants.find((v) => v.id === parseInt(data.variantId));

    if (!variant) return null;

    const res = await addToCart({
      productId: variant.product_id,
      variantId: variant.id,
      price: variant.price,
    });

    if (res.error) {
      toast({
        title: res.error,
        variant: "destructive",
      });
      return;
    }

    toast({
      title: res.success,
    });
  }

however i want that, if user clicks the add to cart button the above logic should be executed but if he clicks buy now button then the above logic should be executed and then the user should be redirected to /checkout