Temiz Kod — İsimler, Fonksiyonlar, Yorumlar

1
@Service
2
public class MaintenanceFeeJob {
3

4
    private final MaintenanceFeeProperties rules;
5
    private final FeeLedger ledger;
6
    private final StatementLineFormatter lines;
7

8
    MaintenanceFeeJob(MaintenanceFeeProperties rules, FeeLedger ledger, StatementLineFormatter lines) {
9
        this.rules = rules;
10
        this.ledger = ledger;
11
        this.lines = lines;
12
    }
13

14
    // One level only: the flow. Each step is a name you can jump to.
15
    public void chargeMonthlyFees(List<Account> accounts, YearMonth month) {
16
        for (Account account : accounts) {
17
            if (isExemptFromFee(account, month)) continue;
18
            Money fee = rules.monthlyFee();
19
            Money tax = bsmvOn(fee);
20
            ledger.debit(account.iban(), fee.plus(tax), lines.maintenanceFee(month, fee, tax));
21
        }
22
    }
23

24
    private boolean isExemptFromFee(Account account, YearMonth month) {
25
        return account.isClosed()
26
                || account.receivesSalaryDeposit()
27
                || account.averageBalance(month).isAtLeast(rules.feeWaiverBalance());
28
    }
29

30
    private Money bsmvOn(Money fee) {
31
        return fee.times(rules.bsmvRate()).roundedTo(2, RoundingMode.HALF_UP);
32
    }
33
}

1
// Bound from application.yml, e.g. bank.fees.maintenance.fee-waiver-balance.
2
@ConfigurationProperties(prefix = "bank.fees.maintenance")
3
public record MaintenanceFeeProperties(
4
        Money monthlyFee,
5
        Money feeWaiverBalance,   // average monthly balance at which the fee is waived
6
        BigDecimal bsmvRate) {    // banking and insurance transactions tax on fees
7
}

1
@Component
2
public class StatementLineFormatter {
3

4
    private static final DateTimeFormatter PERIOD = DateTimeFormatter.ofPattern("MM/yyyy");
5

6
    public StatementLine maintenanceFee(YearMonth month, Money fee, Money tax) {
7
        // The tax goes in the description, not a separate line: the fee disclosure
8
        // shown to the customer quotes fee and tax together, and the two must match.
9
        String text = "Hesap işletim ücreti " + month.format(PERIOD)
10
                + " (ücret " + fee + ", BSMV " + tax + ")";
11
        return new StatementLine(text, fee.plus(tax));
12
    }
13
}

1
// The same job in one method: same output, three levels to hold in your head.
2
public class FeeUtil {
3

4
    private final LedgerDao ledgerDao;
5

6
    FeeUtil(LedgerDao ledgerDao) {
7
        this.ledgerDao = ledgerDao;
8
    }
9

10
    public void calc(List<Account> l, YearMonth m) {
11
        for (Account a : l) {
12
            // skip closed accounts
13
            if (a.isClosed()) continue;
14
            // skip salary customers
15
            if (a.receivesSalaryDeposit()) continue;
16
            // skip if balance is high
17
            if (a.averageBalance(m).value().compareTo(new BigDecimal("50000")) >= 0) continue;
18
            BigDecimal f = new BigDecimal("25.00");
19
            BigDecimal t = f.multiply(new BigDecimal("0.05")).setScale(2, RoundingMode.HALF_UP);
20
            String s = "Hesap işletim ücreti " + m.getMonthValue() + "/" + m.getYear()
21
                    + " (ücret " + f + ", BSMV " + t + ")";
22
            ledgerDao.insert(a.iban(), f.add(t).negate(), s);   // currency? nobody knows
23
        }
24
    }
25
}