Reapply "feat(loyalty): EnakPoint & EnakCoin" (#32)

This reverts commit 4e24f9bbb0.

internal/validator/wallet_validator.go

@@ -0,0 +1,66 @@
+package validator
+
+import (
+	"errors"
+	"strings"
+	"unicode/utf8"
+
+	"apskel-pos-be/internal/constants"
+	"apskel-pos-be/internal/contract"
+)
+
+// walletAdjustmentReasonLimit is the size of wallet_transactions.reason.
+const walletAdjustmentReasonLimit = 255
+
+// walletCashOutWords are reasons that describe turning balance into money. EnakPoint
+// and EnakCoin can never be cashed out, and an adjustment must not be used to record
+// that it happened (docs/prd-point-coin.md K7). Words like "tunai" are left out on
+// purpose: "paid in cash but the points never arrived" is a legitimate reason.
+var walletCashOutWords = []string{"pencairan", "cairkan", "cash out", "cashout", "withdraw"}
+
+type WalletValidator interface {
+	ValidateAdjustRequest(req *contract.AdjustCustomerWalletRequest) (error, string)
+}
+
+type WalletValidatorImpl struct{}
+
+func NewWalletValidator() *WalletValidatorImpl {
+	return &WalletValidatorImpl{}
+}
+
+func (v *WalletValidatorImpl) ValidateAdjustRequest(req *contract.AdjustCustomerWalletRequest) (error, string) {
+	if req == nil {
+		return errors.New("request body is required"), constants.MissingFieldErrorCode
+	}
+
+	req.Currency = strings.ToUpper(strings.TrimSpace(req.Currency))
+	if req.Currency == "" {
+		return errors.New("currency is required"), constants.MissingFieldErrorCode
+	}
+	if !constants.IsValidWalletCurrency(req.Currency) {
+		return errors.New("currency must be POINT or COIN"), constants.MalformedFieldErrorCode
+	}
+
+	if req.Amount == 0 {
+		return errors.New("amount must not be zero: use a positive amount to add and a negative one to take away"), constants.ValidationErrorCode
+	}
+
+	req.Reason = strings.TrimSpace(req.Reason)
+	if req.Reason == "" {
+		return errors.New("reason is required"), constants.MissingFieldErrorCode
+	}
+	if utf8.RuneCountInString(req.Reason) > walletAdjustmentReasonLimit {
+		return errors.New("reason must be at most 255 characters"), constants.MalformedFieldErrorCode
+	}
+	lower := strings.ToLower(req.Reason)
+	for _, word := range walletCashOutWords {
+		if strings.Contains(lower, word) {
+			return errors.New("EnakPoint and EnakCoin cannot be cashed out, so an adjustment cannot be for a cash-out"), constants.ValidationErrorCode
+		}
+	}
+
+	if len(req.IdempotencyKey) > 50 {
+		return errors.New("idempotency_key must be at most 50 characters"), constants.MalformedFieldErrorCode
+	}
+	return nil, ""
+}