/// <summary>
/// Calculates the subtotal (unit price multiplied by <see cref="ShoppingCartItem.Quantity"/>) for a given shopping cart item.
/// </summary>
/// <param name="priceCalculationService">Price calculation service.</param>
/// <param name="cartItem">Shopping cart item.</param>
/// <param name="ignoreDiscounts">A value indicating whether to ignore discounts.</param>
/// <param name="targetCurrency">The target currency to use for money conversion. Obtained from <see cref="IWorkContext.WorkingCurrency"/> if <c>null</c>.</param>
/// <returns>Calculated subtotal.</returns>
public static async Task <CalculatedPrice> CalculateSubtotalAsync(
this IPriceCalculationService2 priceCalculationService,
OrganizedShoppingCartItem cartItem,
bool ignoreDiscounts = false,
Currency targetCurrency = null)
{
Guard.NotNull(priceCalculationService, nameof(priceCalculationService));
Guard.NotNull(cartItem, nameof(cartItem));
var options = priceCalculationService.CreateDefaultOptions(false, cartItem.Item.Customer, targetCurrency);
options.IgnoreDiscounts = ignoreDiscounts;
var context = new PriceCalculationContext(cartItem, options);
var(_, subtotal) = await priceCalculationService.CalculateSubtotalAsync(context);
return(subtotal);
}