Dayner에서 이벤트성, 일회성 쿠폰을 발급하고 관리하는 방법 [1]

public void issueCoupon(Long userId, String couponType) {
    if (couponType.equals("WELCOME")) {
        // 할인율 10%, 만료 30일
        couponRepository.save(new Coupon(userId, 10, 30));
    } else if (couponType.equals("BIRTHDAY")) {
        // 할인율 20%, 만료 7일
        couponRepository.save(new Coupon(userId, 20, 7));
    } else if (couponType.equals("NEW_SEMESTER")) {
        // 신학기 이벤트: 할인율 15%, 만료 14일
        couponRepository.save(new Coupon(userId, 15, 14));
    }
    // 쿠폰 종류가 늘어날수록 분기가 무한정 증가...
}

@Entity
@Table(name = "coupon_policy")
public class CouponPolicy {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    private String name;
 
    @Enumerated(EnumType.STRING)
    private PolicyType policyType;
 
    private int discountRate;
 
    private int minOrderAmount;
 
    private int validDays;
 
    private LocalDateTime eventStartAt;
 
    private LocalDateTime eventEndAt;
 
    private boolean active;
}

public enum PolicyType {
    WELCOME,        // 회원가입 웰컴 쿠폰
    BIRTHDAY,       // 생일 쿠폰
    EVENT,          // 이벤트성 쿠폰 (신학기, 크리스마스 등)
    MANUAL          // 운영팀 수동 발급
}

public interface CouponProcessor {
    PolicyType getSupportedType();
    void issue(Long userId, CouponPolicy policy);
}

@Component
public class EventCouponProcessor implements CouponProcessor {
 
    private final CouponRepository couponRepository;
 
    public EventCouponProcessor(CouponRepository couponRepository) {
        this.couponRepository = couponRepository;
    }
 
    @Override
    public PolicyType getSupportedType() {
        return PolicyType.EVENT;
    }
 
    @Override
    public void issue(Long userId, CouponPolicy policy) {
        LocalDateTime now = LocalDateTime.now();
        if (now.isBefore(policy.getEventStartAt()) || now.isAfter(policy.getEventEndAt())) {
            throw new IllegalStateException("이벤트 기간이 아닙니다.");
        }
 
        LocalDateTime expiredAt = now.plusDays(policy.getValidDays());
        Coupon coupon = Coupon.of(userId, policy, expiredAt);
        couponRepository.save(coupon);
    }
}

@Component
public class WelcomeCouponProcessor implements CouponProcessor {
 
    private final CouponRepository couponRepository;
 
    public WelcomeCouponProcessor(CouponRepository couponRepository) {
        this.couponRepository = couponRepository;
    }
 
    @Override
    public PolicyType getSupportedType() {
        return PolicyType.WELCOME;
    }
 
    @Override
    public void issue(Long userId, CouponPolicy policy) {
        boolean alreadyIssued = couponRepository.existsByUserIdAndPolicyId(userId, policy.getId());
        if (alreadyIssued) {
            throw new IllegalStateException("이미 웰컴 쿠폰이 발급되었습니다.");
        }
 
        LocalDateTime expiredAt = LocalDateTime.now().plusDays(policy.getValidDays());
        Coupon coupon = Coupon.of(userId, policy, expiredAt);
        couponRepository.save(coupon);
    }
}