package com.mydreamjob.deletion;

import com.mydreamjob.audit.AuditService;
import com.mydreamjob.auth.User;
import com.mydreamjob.auth.UserRepository;
import com.mydreamjob.dataexport.PersonalDataExportCleanupService;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.orm.ObjectOptimisticLockingFailureException;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;

/**
 * 注销完成工人（独立事务）。
 *
 * <p>将到期的 PENDING 一次性转为 COMPLETED 并执行用户 PII 脱敏和审计。
 * 通过 REQUIRES_NEW 独立事务 + @Version 乐观锁，保证定时任务与懒转换并发时
 * 只有一个事务完成状态迁移；并发冲突时另一方直接返回 false 且不影响外层请求。幂等安全。
 */
@Slf4j
@Service
@RequiredArgsConstructor
public class AccountDeletionCompletionWorker {

    private static final String PHONE_PREFIX = "deleted_";

    private final AccountDeletionRepository accountDeletionRepository;
    private final UserRepository userRepository;
    private final AuditService auditService;
    private final AccountDeletionPhoneHasher phoneHasher;
    private final PersonalDataExportCleanupService dataExportCleanupService;

    /**
     * 若用户处于 PENDING 且已到期，则执行完成态迁移 + 脱敏 + 审计。
     *
     * @return 本调用是否实际完成了迁移（去重判据）；未到期/非 PENDING/已被它事务完成则返回 false
     */
    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public boolean completeIfExpired(Long userId) {
        AccountDeletion rec = accountDeletionRepository.findByUserId(userId).orElse(null);
        if (rec == null || rec.getStatus() != DeletionStatus.PENDING) {
            return false;
        }
        LocalDateTime now = LocalDateTime.now();
        if (rec.getEffectiveAt() == null || rec.getEffectiveAt().isAfter(now)) {
            return false;
        }
        try {
            // 先记录原手机号墓碑（HMAC），再脱敏；幂等：已脱敏则不会再进入
            beforeDesensitize(rec);
            rec.setStatus(DeletionStatus.COMPLETED);
            rec.setCompletedAt(now);
            accountDeletionRepository.saveAndFlush(rec); // @Version 门控：并发时后到者抛异常
            desensitize(rec.getUserId());
            // 注销完成：清理该用户的个人导出文件并作废未完成任务
            dataExportCleanupService.purgeForDeletedUser(rec.getUserId());
            // 完成 + 脱敏审计各写一次
            auditService.log(userId, "ACCOUNT_DELETION_COMPLETED", "ACCOUNT_DELETION",
                    rec.getId(), "account deletion completed; userId=" + userId
                            + "; PENDING->COMPLETED", null, null, null);
            auditService.log(userId, "ACCOUNT_DATA_DESENSITIZED", "USER",
                    userId, "user pii desensitized; userId=" + userId, null, null, null);
            return true;
        } catch (ObjectOptimisticLockingFailureException e) {
            log.info("Deletion already completed concurrently for userId={}", userId);
            return false;
        }
    }

    /**
     * 脱敏前：用服务端密钥对原手机号计算 HMAC-SHA256 摘要并写入注销记录，
     * 作为"原手机号禁止重新注册"的墓碑。只在首次完成时执行，幂等安全。
     */
    private void beforeDesensitize(AccountDeletion rec) {
        User u = userRepository.findById(rec.getUserId()).orElse(null);
        if (u == null) {
            return;
        }
        String originalPhone = u.getPhone();
        if (originalPhone == null || originalPhone.isBlank()
                || originalPhone.startsWith(PHONE_PREFIX)) {
            return;
        }
        rec.setDeletedPhoneHash(phoneHasher.hash(originalPhone));
    }

    /**
     * 对 users 表做 PII 脱敏（幂等）：phone 改为 deleted_{id} 保证唯一，
     * 其余敏感字段置空，is_active=false。不物理删除任何业务数据。
     */
    private void desensitize(Long userId) {
        User u = userRepository.findById(userId).orElse(null);
        if (u == null) {
            return;
        }
        // 幂等：已脱敏则跳过
        if (Boolean.FALSE.equals(u.getActive()) && u.getPhone() != null
                && u.getPhone().startsWith(PHONE_PREFIX)) {
            return;
        }
        u.setPhone(PHONE_PREFIX + userId);
        u.setEmail(null);
        u.setNickname("deleted");
        u.setAvatarUrl(null);
        u.setPasswordHash(null);
        u.setActive(false);
        userRepository.saveAndFlush(u);
    }
}