private ChangeCalculationDto DoChangeCalculationAccumulator(ChangeCalculationDto changeCalculator, Coin coin)
{
var coinValueIsBiggerThanRemainingAmount = coin.Value > changeCalculator.RemainingAmountInCents;
if (coinValueIsBiggerThanRemainingAmount)
{
return(changeCalculator);
}
if (coin.Amount <= 0)
{
return(changeCalculator);
}
var amountOfCoins = CalculateAmountOfCoins(changeCalculator.RemainingAmountInCents, coin.Value);
var coins = Enumerable.Repeat(coin, amountOfCoins);
changeCalculator.Coins.AddRange(coins);
return(new ChangeCalculationDto
{
Coins = changeCalculator.Coins,
RemainingAmountInCents = changeCalculator.RemainingAmountInCents - (amountOfCoins * coin.Value)
});
}
public IEnumerable <int> CalculateChange(Money purchaseAmount, Money tenderAmount)
{
if (purchaseAmount.CurrencyAmount > tenderAmount.CurrencyAmount)
{
throw new Exception("I need more money!");
}
var seed = new ChangeCalculationDto {
RemainingAmountInCents = tenderAmount.CentAmount - purchaseAmount.CentAmount
};
var changeCalculationResult = CoinDenominations.Aggregate(seed, DoChangeCalculationAccumulator);
return(changeCalculationResult.Coins.Select(coin => coin.Value));
}