public CheckoutState Apply(CheckoutState checkoutState)
{
if (checkoutState.DiscountableItemsTotal == 0)
{
return(ToNotAppliedState(checkoutState));
}
var discountToApply = Math.Min(checkoutState.DiscountableItemsTotal, _value);
var newBasketTotal = checkoutState.CurrentTotal - discountToApply;
return(checkoutState.ToNewState(newBasketTotal, DiscountResult.CreateApplied(_id)));
}
public CheckoutState Apply(CheckoutState checkoutState)
{
var applicableItems = GetApplicableItems(checkoutState).ToArray();
if (!applicableItems.Any())
{
return(ToNotAppliedCheckoutState(checkoutState, GetNoApplicableProductsMessage()));
}
var leftToSpend = AmountRequiredToPassThreshold(checkoutState.DiscountableItemsTotal);
if (leftToSpend > 0)
{
return(ToNotAppliedCheckoutState(checkoutState, GetThresholdNotReachedMessage(leftToSpend)));
}
var currentSpendOnApplicableItems = CurrentSpendOnApplicableItems(applicableItems);
var discountToApply = CalculateDiscountToApply(currentSpendOnApplicableItems);
var newStateTotal = checkoutState.CurrentTotal - discountToApply;
return(checkoutState.ToNewState(newStateTotal, DiscountResult.CreateApplied(_id)));
}
private CheckoutState ToNotAppliedState(CheckoutState checkoutState)
{
var notAppliedResult = DiscountResult.CreateNotApplied(_id, GetNotAppliedMessage());
return(checkoutState.ToNewState(checkoutState.CurrentTotal, notAppliedResult));
}
private CheckoutState ToNotAppliedCheckoutState(CheckoutState checkoutState, string message)
{
var notAppliedResult = DiscountResult.CreateNotApplied(_id, message);
return(checkoutState.ToNewState(checkoutState.CurrentTotal, notAppliedResult));
}
