public void AddCoin(Coin coin, int ammount)
{
Contract.Requires(ammount > 0);
Contract.Requires(Contract.Exists(Wallet, el => (decimal)el.Element("Type") == coin.ToValue()),
"PRE: The coin type must exist in the wallet");
Contract.Ensures(ammount <= (int)Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single().Element("Ammount"));
Contract.Ensures(Contract.OldValue((int)Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single().Element("Ammount")) + ammount ==
(int)Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single().Element("Ammount"));
XElement soughtCoin = Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single();
soughtCoin.Element("Ammount").Value = ((int)soughtCoin.Element("Ammount") + ammount).ToString();
Database.Save("CoinDatabase.xml");
}
public TransactionResult InsertCoin(Coin coin)
{
Contract.Requires(state == State.ProductChosen || state == State.MoneyInserted);
Contract.Ensures(state == State.MoneyInserted);
InsertedValue += coin.ToValue();
CoinMan.AddCoin(coin, 1);
state = State.MoneyInserted;
if (SelectedProduct != null && !CoinMan.CheckChange(SelectedProduct.Price, InsertedValue))
return TransactionResult.SuccessButNoChange;
return TransactionResult.Success;
}
public void EjectCoin(Coin coin, int ammount, LinkedList<Coin> coinCase)
{
Contract.Requires(coinCase != null);
Contract.Requires(ammount >= 0);
Contract.Requires(Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Select(c => (int)c.Element("Ammount")).Single() >= ammount,
"PRE: There must be enough of coins of given type to eject");
Contract.Ensures(Contract.OldValue(coinCase.Where(c => c == coin).Count()) + ammount == coinCase.Where(c => c == coin).Count(),
"POST: The ejected coins must be in the case");
Contract.Ensures(Contract.OldValue((int)Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single().Element("Ammount")) - ammount ==
(int)Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single().Element("Ammount"));
XElement soughtCoin = Wallet.Where(c => (decimal)c.Element("Type") == coin.ToValue()).Single();
soughtCoin.Element("Ammount").Value = ((int)soughtCoin.Element("Ammount") - ammount).ToString();
for (int i = 0; i < ammount; ++i)
coinCase.AddLast(coin);
Database.Save("CoinDatabase.xml");
}