Limit Coupon Redemptions: Code Review Practice

Marketing wants coupons that run out. Each coupon now has an expiry and a redemption limit, and each customer can redeem a coupon once. Also adds the HTTP handler for the redeem button.

Mcoupons/service.go1 of 3

Files Changed

coupons/

coupons/service.go

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@@ -1,20 +1,43 @@

package coupons

import (

"context"

"errors"

"time"

)

var ErrNotFound = errors.New("coupon not found")

var (

ErrNotFound = errors.New("coupon not found")

ErrExpired = errors.New("coupon expired")

ErrExhausted = errors.New("coupon fully redeemed")

ErrAlreadyRedeemed = errors.New("coupon already redeemed")

)

type Service struct {

store Store

}

func (s *Service) Redeem(ctx context.Context, userID, code string) error {

c, err := s.store.GetCoupon(ctx, code)

if err != nil {

return err

}

if time.Now().After(c.ExpiresAt) {

return ErrExpired

}

used, err := s.store.HasRedeemed(ctx, userID, c.Code)

if err != nil {

return err

}

if used {

return ErrAlreadyRedeemed

}

if c.Redemptions >= c.MaxRedemptions {

return ErrExhausted

}

c.Redemptions++

if err := s.store.SaveCoupon(ctx, c); err != nil {

return err

}

return s.store.AddRedemption(ctx, userID, c.Code)

}

coupons/service.go

coupons/handler.go

coupons/service_test.go