public OperationResult WithdrawMoney(string accountNumber, decimal withdrawAmount)
{
var account = dbContext.Users
.Single(a => a.UserName == accountNumber);
// in a real system we would be using transactions here to try to withdraw money
// and then check if successful (and amount was not exceeded)
// in order to avoid possible concurrency issues
// here we will stick with naive approach of just checking beforehand and process the results
if (withdrawAmount > account.Balance)
{
throw new AmountExceededException("Can't proceed withdrawal. Not enough balance left!");
}
// process operation
account.Balance -= withdrawAmount;
// log operation
var timestamp = DateTime.Now; // would also abstract that away to allow unit testing and get rid of dependency on a static member touching environment
var opLog = new OperationLog
{
CreditCardAccountId = account.Id,
Timestamp = timestamp,
Code = OperationCode.MoneyWithdrawal,
Payload = String.Format("Withdrawal amount {0}, balance left {1}", withdrawAmount, account.Balance)
};
dbContext.OperationLogs.Add(opLog);
// save
dbContext.SaveChanges();
return new OperationResult
{
CardNumber = accountNumber,
Timestamp = timestamp,
BalanceLeftAmount = account.Balance,
AmountWithdrawed = withdrawAmount
};
}
public AccountBalanceStamp GetBalanceForAccount(string accountNumber)
{
// get balance
var account = dbContext.Users
.Single(a => a.UserName == accountNumber);
// log operation
var timestamp = DateTime.Now; // would also abstract that away to allow unit testing and get rid of dependency on a static member touching environment
var opLog = new OperationLog
{
CreditCardAccountId = account.Id,
Timestamp = timestamp,
Code = OperationCode.BalanceRequest,
Payload = String.Format("Balance equals {0}", account.Balance)
};
dbContext.OperationLogs.Add(opLog);
dbContext.SaveChanges();
// return result
return new AccountBalanceStamp
{
CardNumber = accountNumber,
MoneyAmount = account.Balance,
Timestamp = timestamp,
};
}