feat: caret preservation and Luhn validation in card inputs

- Added generic formatAndPreserveCursor() helper on frontend to track
  and restore selection caret position during dynamic input sanitization
- Applied to all card inputs, gift card code inputs, and expiry inputs
- Added Luhn validation (isValidLuhn) for saved cards and gift cards
- Rebuilt payments test DB and got 100% green tests

backend/handlers/payments/giftcards.go

@@ -0,0 +1,703 @@
+package payments
+
+import (
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"log"
+	"net/http"
+	"time"
+
+	"crussell/db"
+	"crussell/internal/square"
+	"crussell/internal/validators"
+	"crussell/mw"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/jackc/pgx/v5"
+)
+
+// --- Types ---
+
+type GiftCard struct {
+	ID               string     `json:"id"`
+	TotalFundsAdded  float64    `json:"total_funds_added"`
+	AmountRemaining  float64    `json:"amount_remaining"`
+	CreatedBy        *string    `json:"created_by,omitempty"`
+	CreatedAt        time.Time  `json:"created_at"`
+	RedeemedAt       *time.Time `json:"redeemed_at,omitempty"`
+	RedeemedBy       *string    `json:"redeemed_by,omitempty"`
+}
+
+type GiftCardSummary struct {
+	TotalUnclaimed   float64    `json:"total_unclaimed"`
+	TotalUserBalances float64   `json:"total_user_balances"`
+	GiftCards        []GiftCard `json:"gift_cards"`
+}
+
+type CreateGiftCardRequest struct {
+	Amount float64 `json:"amount"` // in pounds (e.g. 10.00, 25.00)
+}
+
+type TopUpGiftCardRequest struct {
+	Amount float64 `json:"amount"` // in pounds
+}
+
+type TransferGiftCardRequest struct {
+	ToCardID string  `json:"to_card_id"`
+	Amount   float64 `json:"amount"`
+}
+
+type BuyGiftCardRequest struct {
+	Amount         int64   `json:"amount"`
+	RecipientType  string  `json:"recipient_type"`
+	RecipientEmail string  `json:"recipient_email,omitempty"`
+	CardID         *string `json:"card_id,omitempty"`
+	NewCardToken   *string `json:"new_card_token,omitempty"`
+	SaveCard       bool    `json:"save_card"`
+	IdempotencyKey string  `json:"idempotency_key"`
+}
+
+type RedeemGiftCardRequest struct {
+	Code string `json:"code"`
+}
+
+// --- Admin Handlers ---
+
+func GetGiftCards(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+
+	var summary GiftCardSummary
+	summary.GiftCards = []GiftCard{}
+
+	err := db.DB.QueryRow(ctx, `
+		SELECT COALESCE(SUM(amount_remaining), 0)
+		FROM gift_cards
+		WHERE redeemed_by IS NULL
+	`).Scan(&summary.TotalUnclaimed)
+	if err != nil {
+		log.Printf("Failed to calculate total unclaimed gift cards: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	err = db.DB.QueryRow(ctx, `
+		SELECT COALESCE(SUM(balance), 0)
+		FROM user_giftcard_balances
+	`).Scan(&summary.TotalUserBalances)
+	if err != nil {
+		log.Printf("Failed to calculate total user balances: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	rows, err := db.DB.Query(ctx, `
+		SELECT id, total_funds_added, amount_remaining, created_by, created_at, redeemed_at, redeemed_by
+		FROM gift_cards
+		ORDER BY created_at DESC
+	`)
+	if err != nil {
+		log.Printf("Failed to query gift cards: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var gc GiftCard
+		var createdBy, redeemedBy sql.NullString
+		var redeemedAt sql.NullTime
+
+		err = rows.Scan(
+			&gc.ID,
+			&gc.TotalFundsAdded,
+			&gc.AmountRemaining,
+			&createdBy,
+			&gc.CreatedAt,
+			&redeemedAt,
+			&redeemedBy,
+		)
+		if err != nil {
+			log.Printf("Failed to scan gift card: %v", err)
+			http.Error(w, "Internal server error", http.StatusInternalServerError)
+			return
+		}
+
+		if createdBy.Valid {
+			gc.CreatedBy = &createdBy.String
+		}
+		if redeemedBy.Valid {
+			gc.RedeemedBy = &redeemedBy.String
+		}
+		if redeemedAt.Valid {
+			gc.RedeemedAt = &redeemedAt.Time
+		}
+
+		summary.GiftCards = append(summary.GiftCards, gc)
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(summary)
+}
+
+func CreateGiftCard(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	adminID, _ := ctx.Value(mw.UserIDKey).(string)
+
+	var req CreateGiftCardRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid request", http.StatusBadRequest)
+		return
+	}
+
+	if req.Amount <= 0 {
+		http.Error(w, "Amount must be greater than zero", http.StatusBadRequest)
+		return
+	}
+
+	var gc GiftCard
+	err := db.DB.QueryRow(ctx, `
+		INSERT INTO gift_cards (total_funds_added, amount_remaining, created_by)
+		VALUES ($1, $1, $2)
+		RETURNING id, total_funds_added, amount_remaining, created_by, created_at
+	`, req.Amount, adminID).Scan(
+		&gc.ID,
+		&gc.TotalFundsAdded,
+		&gc.AmountRemaining,
+		&gc.CreatedBy,
+		&gc.CreatedAt,
+	)
+	if err != nil {
+		log.Printf("Failed to create gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusCreated)
+	json.NewEncoder(w).Encode(gc)
+}
+
+func TopUpGiftCard(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	cardID := chi.URLParam(r, "id")
+	if cardID == "" || !validators.IsValidID(cardID) {
+		http.Error(w, "Invalid gift card ID", http.StatusBadRequest)
+		return
+	}
+
+	var req TopUpGiftCardRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid request", http.StatusBadRequest)
+		return
+	}
+
+	if req.Amount <= 0 {
+		http.Error(w, "Amount must be greater than zero", http.StatusBadRequest)
+		return
+	}
+
+	tx, err := db.DB.Begin(ctx)
+	if err != nil {
+		log.Printf("Failed to begin transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer tx.Rollback(ctx)
+
+	var redeemedBy sql.NullString
+	err = tx.QueryRow(ctx, "SELECT redeemed_by FROM gift_cards WHERE id = $1", cardID).Scan(&redeemedBy)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			http.Error(w, "Gift card not found", http.StatusNotFound)
+			return
+		}
+		log.Printf("Failed to check gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if redeemedBy.Valid {
+		http.Error(w, "Cannot top up a card that has already been redeemed to an account", http.StatusBadRequest)
+		return
+	}
+
+	var gc GiftCard
+	var createdBy sql.NullString
+	err = tx.QueryRow(ctx, `
+		UPDATE gift_cards
+		SET total_funds_added = total_funds_added + $1,
+		    amount_remaining = amount_remaining + $1
+		WHERE id = $2
+		RETURNING id, total_funds_added, amount_remaining, created_by, created_at
+	`, req.Amount, cardID).Scan(
+		&gc.ID,
+		&gc.TotalFundsAdded,
+		&gc.AmountRemaining,
+		&createdBy,
+		&gc.CreatedAt,
+	)
+	if err != nil {
+		log.Printf("Failed to top up gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if createdBy.Valid {
+		gc.CreatedBy = &createdBy.String
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		log.Printf("Failed to commit transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(gc)
+}
+
+func TransferGiftCard(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	fromCardID := chi.URLParam(r, "from")
+	if fromCardID == "" || !validators.IsValidID(fromCardID) {
+		http.Error(w, "Invalid source gift card ID", http.StatusBadRequest)
+		return
+	}
+
+	var req TransferGiftCardRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid request", http.StatusBadRequest)
+		return
+	}
+
+	req.ToCardID = normalizeCode(req.ToCardID)
+	if !validators.IsValidID(req.ToCardID) {
+		http.Error(w, "Invalid destination gift card ID", http.StatusBadRequest)
+		return
+	}
+
+	if fromCardID == req.ToCardID {
+		http.Error(w, "Source and destination cards must be different", http.StatusBadRequest)
+		return
+	}
+
+	if req.Amount <= 0 {
+		http.Error(w, "Amount must be greater than zero", http.StatusBadRequest)
+		return
+	}
+
+	tx, err := db.DB.Begin(ctx)
+	if err != nil {
+		log.Printf("Failed to begin transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer tx.Rollback(ctx)
+
+	var fromRedeemedBy, toRedeemedBy sql.NullString
+	var fromRemaining, toRemaining float64
+
+	err = tx.QueryRow(ctx, "SELECT redeemed_by, amount_remaining FROM gift_cards WHERE id = $1", fromCardID).Scan(&fromRedeemedBy, &fromRemaining)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			http.Error(w, "Source gift card not found", http.StatusNotFound)
+			return
+		}
+		log.Printf("Failed to check source gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	err = tx.QueryRow(ctx, "SELECT redeemed_by, amount_remaining FROM gift_cards WHERE id = $1", req.ToCardID).Scan(&toRedeemedBy, &toRemaining)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			http.Error(w, "Destination gift card not found", http.StatusNotFound)
+			return
+		}
+		log.Printf("Failed to check destination gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if fromRedeemedBy.Valid || toRedeemedBy.Valid {
+		http.Error(w, "Cannot transfer balance to/from cards redeemed to accounts", http.StatusBadRequest)
+		return
+	}
+
+	if fromRemaining < req.Amount {
+		http.Error(w, "Insufficient balance on source gift card", http.StatusBadRequest)
+		return
+	}
+
+	_, err = tx.Exec(ctx, `
+		UPDATE gift_cards
+		SET amount_remaining = amount_remaining - $1
+		WHERE id = $2
+	`, req.Amount, fromCardID)
+	if err != nil {
+		log.Printf("Failed to deduct from source: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	_, err = tx.Exec(ctx, `
+		UPDATE gift_cards
+		SET amount_remaining = amount_remaining + $1,
+		    total_funds_added = total_funds_added + $1
+		WHERE id = $2
+	`, req.Amount, req.ToCardID)
+	if err != nil {
+		log.Printf("Failed to add to destination: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		log.Printf("Failed to commit transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	json.NewEncoder(w).Encode(map[string]string{"status": "success"})
+}
+
+// --- User Handlers ---
+
+func RedeemGiftCard(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	userID, ok := ctx.Value(mw.UserIDKey).(string)
+	if !ok || userID == "" {
+		http.Error(w, "Authentication required", http.StatusUnauthorized)
+		return
+	}
+
+	var req RedeemGiftCardRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid request", http.StatusBadRequest)
+		return
+	}
+
+	code := normalizeCode(req.Code)
+	if !validators.IsValidID(code) {
+		http.Error(w, "Invalid gift card code format", http.StatusBadRequest)
+		return
+	}
+
+	tx, err := db.DB.Begin(ctx)
+	if err != nil {
+		log.Printf("Failed to begin transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer tx.Rollback(ctx)
+
+	var amountRemaining float64
+	var redeemedBy sql.NullString
+	err = tx.QueryRow(ctx, `
+		SELECT amount_remaining, redeemed_by
+		FROM gift_cards
+		WHERE id = $1
+	`, code).Scan(&amountRemaining, &redeemedBy)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			http.Error(w, "Invalid or expired gift card code", http.StatusNotFound)
+			return
+		}
+		log.Printf("Failed to query gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if redeemedBy.Valid {
+		http.Error(w, "This gift card has already been redeemed", http.StatusBadRequest)
+		return
+	}
+
+	if amountRemaining <= 0 {
+		http.Error(w, "This gift card has no remaining balance", http.StatusBadRequest)
+		return
+	}
+
+	_, err = tx.Exec(ctx, `
+		UPDATE gift_cards
+		SET amount_remaining = 0,
+		    redeemed_at = NOW(),
+		    redeemed_by = $1
+		WHERE id = $2
+	`, userID, code)
+	if err != nil {
+		log.Printf("Failed to update gift card: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	_, err = tx.Exec(ctx, `
+		INSERT INTO user_giftcard_balances (user_id, balance, updated_at)
+		VALUES ($1, $2, NOW())
+		ON CONFLICT (user_id) DO UPDATE SET
+			balance = user_giftcard_balances.balance + EXCLUDED.balance,
+			updated_at = NOW()
+	`, userID, amountRemaining)
+	if err != nil {
+		log.Printf("Failed to update user gift card balance: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		log.Printf("Failed to commit transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	json.NewEncoder(w).Encode(map[string]interface{}{
+		"status": "success",
+		"amount_redeemed": amountRemaining,
+	})
+}
+
+func GetGiftCardBalance(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	userID, ok := ctx.Value(mw.UserIDKey).(string)
+	if !ok || userID == "" {
+		http.Error(w, "Authentication required", http.StatusUnauthorized)
+		return
+	}
+
+	var balance float64
+	err := db.DB.QueryRow(ctx, "SELECT balance FROM user_giftcard_balances WHERE user_id = $1", userID).Scan(&balance)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]float64{"balance": 0.00})
+			return
+		}
+		log.Printf("Failed to query user balance: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]float64{"balance": balance})
+}
+
+// GetUserGiftCardBalanceAdmin Handler returns any user's balance for the admin.
+func GetUserGiftCardBalanceAdmin(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	userID := chi.URLParam(r, "id")
+	if userID == "" || !validators.IsValidID(userID) {
+		http.Error(w, "Invalid user ID", http.StatusBadRequest)
+		return
+	}
+
+	var balance float64
+	err := db.DB.QueryRow(ctx, "SELECT balance FROM user_giftcard_balances WHERE user_id = $1", userID).Scan(&balance)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]float64{"balance": 0.00})
+			return
+		}
+		log.Printf("Failed to query user balance: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]float64{"balance": balance})
+}
+
+func BuyGiftCard(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	userID, ok := ctx.Value(mw.UserIDKey).(string)
+	if !ok || userID == "" {
+		http.Error(w, "Authentication required", http.StatusUnauthorized)
+		return
+	}
+
+	var req BuyGiftCardRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid request", http.StatusBadRequest)
+		return
+	}
+
+	allowedAmounts := map[int64]bool{1000: true, 2000: true, 5000: true}
+	if !allowedAmounts[req.Amount] {
+		http.Error(w, "Invalid amount. Must be £10, £20, or £50.", http.StatusBadRequest)
+		return
+	}
+
+	if req.RecipientType != "self" && req.RecipientType != "friend" {
+		http.Error(w, "Invalid recipient type", http.StatusBadRequest)
+		return
+	}
+
+	if err := ValidateCardInfo(req.CardID, req.NewCardToken); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	paymentService := NewPaymentService()
+
+	var sourceID string
+	var savedCardID *string
+
+	if req.NewCardToken != nil && *req.NewCardToken != "" {
+		cardOnFile, err := SquareClient.CreateCardOnFile(ctx, userID, *req.NewCardToken)
+		if err != nil {
+			log.Printf("Failed to create card on file: %v", err)
+			http.Error(w, "Failed to process card", http.StatusInternalServerError)
+			return
+		}
+
+		sourceID = cardOnFile.CardID
+
+		if req.SaveCard {
+			cardID, err := paymentService.SaveCardForUser(ctx, userID, cardOnFile.CardID, cardOnFile.Brand, cardOnFile.Last4, cardOnFile.ExpMonth, cardOnFile.ExpYear, cardOnFile.Fingerprint)
+			if err != nil {
+				log.Printf("Failed to save card: %v", err)
+			} else {
+				savedCardID = &cardID
+			}
+		}
+	} else if req.CardID != nil {
+		card, err := paymentService.GetCardByID(ctx, *req.CardID, userID)
+		if err != nil {
+			if errors.Is(err, pgx.ErrNoRows) {
+				http.Error(w, "Card not found", http.StatusNotFound)
+				return
+			}
+			log.Printf("Failed to get card: %v", err)
+			http.Error(w, "Internal server error", http.StatusInternalServerError)
+			return
+		}
+		sourceID = card.SquareCardID
+		savedCardID = req.CardID
+	}
+
+	paymentReq := square.CreatePaymentReq{
+		Amount:         req.Amount,
+		Currency:       "GBP",
+		SourceID:       sourceID,
+		IdempotencyKey: req.IdempotencyKey,
+		Note:           "Gift Card Purchase",
+	}
+
+	paymentResult, err := SquareClient.CreatePayment(ctx, paymentReq)
+	if err != nil {
+		log.Printf("Failed to process gift card purchase payment: %v", err)
+		http.Error(w, "Payment failed", http.StatusPaymentRequired)
+		return
+	}
+
+	tx, err := db.DB.Begin(ctx)
+	if err != nil {
+		log.Printf("Failed to begin transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+	defer tx.Rollback(ctx)
+
+	amountPounds := float64(req.Amount) / 100.0
+
+	var cardID string
+
+	if req.RecipientType == "self" {
+		err = tx.QueryRow(ctx, `
+			INSERT INTO gift_cards (total_funds_added, amount_remaining, created_by, redeemed_at, redeemed_by)
+			VALUES ($1, 0, $2, NOW(), $2)
+			RETURNING id
+		`, amountPounds, userID).Scan(&cardID)
+		if err != nil {
+			log.Printf("Failed to insert gift card: %v", err)
+			http.Error(w, "Internal server error", http.StatusInternalServerError)
+			return
+		}
+
+		_, err = tx.Exec(ctx, `
+			INSERT INTO user_giftcard_balances (user_id, balance, updated_at)
+			VALUES ($1, $2, NOW())
+			ON CONFLICT (user_id) DO UPDATE SET
+				balance = user_giftcard_balances.balance + EXCLUDED.balance,
+				updated_at = NOW()
+		`, userID, amountPounds)
+		if err != nil {
+			log.Printf("Failed to update balance: %v", err)
+			http.Error(w, "Internal server error", http.StatusInternalServerError)
+			return
+		}
+	} else {
+		err = tx.QueryRow(ctx, `
+			INSERT INTO gift_cards (total_funds_added, amount_remaining, created_by)
+			VALUES ($1, $1, $2)
+			RETURNING id
+		`, amountPounds, userID).Scan(&cardID)
+		if err != nil {
+			log.Printf("Failed to insert gift card: %v", err)
+			http.Error(w, "Internal server error", http.StatusInternalServerError)
+			return
+		}
+
+		recipient := req.RecipientEmail
+		if recipient == "" {
+			var userEmail string
+			_ = tx.QueryRow(ctx, "SELECT email FROM users WHERE id = $1", userID).Scan(&userEmail)
+			recipient = userEmail
+		}
+		log.Printf("[TODO EMAIL] Send gift card code %s (Value: £%.2f) to %s", cardID, amountPounds, recipient)
+	}
+
+	fees := paymentService.CalculateFees(req.Amount, "online")
+	record := PaymentRecord{
+		PaymentType:     "full",
+		PaymentMethod:   "online_square",
+		Status:          "completed",
+		Amount:          amountPounds,
+		SquarePaymentID: &paymentResult.SquarePayID,
+		IdempotencyKey:  &req.IdempotencyKey,
+		Fees:            float64(fees) / 100.0,
+		UserSavedCardID: savedCardID,
+		CreatedAt:       time.Now(),
+		UpdatedAt:       time.Now(),
+		CreatedBy:       &userID,
+	}
+
+	_, err = tx.Exec(ctx, `
+		INSERT INTO payments (payment_type, payment_method, status, amount, square_payment_id, idempotency_key, fees, user_saved_card_id, created_by, created_at, updated_at)
+		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
+	`, record.PaymentType, record.PaymentMethod, record.Status, record.Amount, record.SquarePaymentID, record.IdempotencyKey, record.Fees, record.UserSavedCardID, record.CreatedBy, record.CreatedAt, record.UpdatedAt)
+	if err != nil {
+		log.Printf("Failed to insert payment record: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		log.Printf("Failed to commit buy transaction: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusCreated)
+	json.NewEncoder(w).Encode(map[string]interface{}{
+		"status": "success",
+		"code": cardID,
+		"amount": amountPounds,
+	})
+}
+
+// --- Helpers ---
+
+func normalizeCode(code string) string {
+	clean := ""
+	for _, char := range code {
+		if (char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z') || (char >= '0' && char <= '9') {
+			clean += string(char)
+		}
+	}
+	return clean
+}