public decimal PayWithBankAsMuchAsPossible(IEnumerable <BankAccount> bankAccounts, decimal amount, BillsPaymentDbContext db)
{
foreach (var account in bankAccounts)
{
db.Entry(account).State = EntityState.Unchanged;
if (account.Balance >= amount)
{
account.Withdraw(amount);
amount = 0;
break;
}
amount -= account.Balance;
account.Withdraw(account.Balance);
}
return(amount);
}
public void PayWithCreditCards(decimal amount, IEnumerable <CreditCard> creditCards, BillsPaymentDbContext db)
{
if (creditCards.Select(c => c.LimitLeft).Sum() < amount)
{
throw new InvalidOperationException(AmountGreaterThanPossibilities);
}
foreach (var card in creditCards)
{
db.Entry(card).State = EntityState.Unchanged;
if (card.LimitLeft >= amount)
{
card.Withdraw(amount);
return;
}
amount -= card.LimitLeft;
card.Withdraw(card.LimitLeft);
}
}