public bool DoPurchase(Product product)
{
if (_pBox == null) throw new InvalidOperationException("_pBox");
bool purchased = false;
MachineStatus oldStatus = _status;
_status = MachineStatus.InTransaction;
CoinBox changes = _rBox;
try
{
if (product.Equals(_none))
throw new Exception();
int count = _pBox[product];
if (count < 0)
throw new Exception("No such product is avaiable.");
if (count == 0)
throw new Exception("The product is out of sale.");
int changesValue = _rBox.TotalValue - product.Price;
if (changesValue < 0)
throw new Exception("Not enough money.");
changes = OnMakeChanges(changesValue);
if (changes == null)
{
changes = _rBox;
throw new Exception("Cannot return changes.");
}
DeliverProduct(product);
purchased = true;
}
catch (Exception ex)
{
if (_msg != null)
_msg.Show(ex.Message);
}
finally
{
ReturnChanges(changes);
_status = oldStatus;
}
return purchased;
}
private void DeliverProduct(Product product)
{
if (_pBox[product] <= 0)
throw new InvalidOperationException("product");
if (_msg != null)
_msg.Show(string.Format("Delivering product: {0}", product));
_pBox[product]--;
}
