public ChangeHolder PurchaseItem(ChangeHolder userChangeHolder, int itemCost)
{
int userChangeValue = userChangeHolder.TotalValue();
// If the user didnt provide enough money return thier change
if (userChangeValue < itemCost)
{
this.MessageToUser = Constants.NOT_ENOUGH_MONEY_PROVIDED;
return userChangeHolder;
}
// If change required is not available then just return original change
if ((userChangeValue - itemCost) > _changeHolder.TotalValue())
{
this.MessageToUser = Constants.SORRY_NO_CHANGE;
return userChangeHolder;
}
// Attempt to return change
ChangeHolder changeForUser = new ChangeHolder();
int totalChangeRequiredByUser = userChangeHolder.TotalValue() - itemCost;
Enum.GetValues(typeof(CoinType))
.Cast<CoinType>()
.OrderByDescending(coinType => (int)coinType)
.ToList<CoinType>()
.ForEach(coinType =>
{
if ((int)coinType <= itemCost)
{
_changeHolder.Coins
.Where(c => c.Weight == (int) coinType && c.Weight <= totalChangeRequiredByUser)
.TakeWhile(c =>
{
if (changeForUser.TotalValue() + c.Weight <= totalChangeRequiredByUser)
{
changeForUser.Add(c);
}
return changeForUser.TotalValue() <= totalChangeRequiredByUser;
})
.Select(c => c).ToList(); // ToList() needs to be executed to override
// the deferred execution behaviour of Linq
}
}
);
// Remove the coins returned from the changeholder.
changeForUser.Coins.ForEach(coin => _changeHolder.Coins.Remove(coin));
this.MessageToUser = Constants.THANK_YOU;
return changeForUser;
}