/**
 * 钱包生成重试定时任务 (增强版)
 *
 * 设计目标：100% 确保每个用户的钱包最终能生成成功
 *
 * 核心改进：
 * 1. 基于数据库扫描：不依赖 Redis 状态，直接查询钱包不完整的用户
 * 2. 指数退避：1分钟 → 2分钟 → 4分钟 → ... → 最大60分钟
 * 3. 无时间限制：持续重试直到成功，不会放弃
 * 4. 分布式锁：防止多实例重复触发同一用户的重试
 *
 * 重试触发条件：
 * - 数据库中三链地址不全的用户
 * - Redis 状态为 failed/超时/无状态
 *
 * 与 getWalletStatus API 的配合：
 * - API 调用时也会触发重试（用户主动轮询）
 * - 定时任务作为兜底，确保即使用户不调用 API 也能重试
 */

import { Injectable, Logger } from '@nestjs/common';
import { Cron, CronExpression } from '@nestjs/schedule';
import { RedisService } from '@/infrastructure/redis/redis.service';
import { EventPublisherService } from '@/infrastructure/kafka/event-publisher.service';
import {
  UserAccountRepository,
  USER_ACCOUNT_REPOSITORY,
} from '@/domain/repositories/user-account.repository.interface';
import { Inject } from '@nestjs/common';
import { UserId } from '@/domain/value-objects';
import { MpcKeygenRequestedEvent } from '@/domain/events';

// Redis key prefix
const KEYGEN_STATUS_PREFIX = 'keygen:status:';
const KEYGEN_RETRY_PREFIX = 'keygen:retry:';
const KEYGEN_LOCK_PREFIX = 'keygen:lock:';

// 超时配置
const KEYGEN_TIMEOUT_MS = 60 * 1000; // 60 秒视为超时

// 指数退避配置
const MIN_BACKOFF_MINUTES = 1; // 最小退避时间：1分钟
const MAX_BACKOFF_MINUTES = 60; // 最大退避时间：60分钟

// 每次扫描的最大用户数
const MAX_USERS_PER_SCAN = 100;

// 每次任务最多触发的重试数量（防止 MPC 服务过载）
const MAX_RETRIES_PER_RUN = 10;

export interface KeygenStatusData {
  status: 'pending' | 'generating' | 'deriving' | 'completed' | 'failed';
  userId: string;
  mpcSessionId?: string;
  publicKey?: string;
  errorMessage?: string;
  updatedAt: string;
}

export interface RetryRecord {
  userId: string;
  retryCount: number;
  firstRetryAt: string;
  lastRetryAt: string;
  nextRetryAt: string; // 下次允许重试的时间
}

@Injectable()
export class WalletRetryTask {
  private readonly logger = new Logger(WalletRetryTask.name);

  constructor(
    private readonly redisService: RedisService,
    private readonly eventPublisher: EventPublisherService,
    @Inject(USER_ACCOUNT_REPOSITORY)
    private readonly userRepository: UserAccountRepository,
  ) {}

  /**
   * 每分钟执行一次检查
   *
   * 使用分布式锁保护整个任务，防止多实例并发执行
   */
  @Cron(CronExpression.EVERY_MINUTE)
  async handleWalletRetry() {
    const taskLockKey = 'wallet-retry-task:lock';

    // 尝试获取任务级别的分布式锁（2分钟过期）
    const gotTaskLock = await this.redisService.tryLock(taskLockKey, 120);
    if (!gotTaskLock) {
      this.logger.debug(
        '[TASK] Another instance is running the task, skipping',
      );
      return;
    }

    this.logger.log('[TASK] Starting wallet retry check (database-driven)...');

    try {
      // 1. 从数据库查询钱包不完整的用户
      const incompleteUserIds =
        await this.userRepository.findUsersWithIncompleteWallets(
          MAX_USERS_PER_SCAN,
        );

      if (incompleteUserIds.length === 0) {
        this.logger.log('[TASK] No users with incomplete wallets found');
        return;
      }

      this.logger.log(
        `[TASK] Found ${incompleteUserIds.length} users with incomplete wallets`,
      );

      // 2. 逐个检查并处理
      let retriedCount = 0;
      let skippedCount = 0;

      for (const userId of incompleteUserIds) {
        // 限制每次任务最多触发的重试数量，防止 MPC 服务过载
        if (retriedCount >= MAX_RETRIES_PER_RUN) {
          this.logger.log(
            `[TASK] Reached max retries per run (${MAX_RETRIES_PER_RUN}), stopping`,
          );
          break;
        }

        try {
          const retried = await this.checkAndRetryUser(userId.value.toString());
          if (retried) {
            retriedCount++;
          } else {
            skippedCount++;
          }
        } catch (error) {
          this.logger.error(
            `[TASK] Error processing user ${userId.value}: ${error}`,
          );
        }
      }

      this.logger.log(
        `[TASK] Wallet retry check completed: retried=${retriedCount}, skipped=${skippedCount}`,
      );
    } catch (error) {
      this.logger.error(`[TASK] Wallet retry task failed: ${error}`, error);
    } finally {
      // 释放任务锁
      await this.redisService.unlock(taskLockKey);
    }
  }

  /**
   * 检查单个用户并决定是否重试
   *
   * @returns true 如果触发了重试，false 如果跳过
   */
  private async checkAndRetryUser(userId: string): Promise<boolean> {
    // 1. 检查是否在退避期内
    const shouldWait = await this.isInBackoffPeriod(userId);
    if (shouldWait) {
      this.logger.debug(
        `[TASK] User ${userId} is in backoff period, skipping`,
      );
      return false;
    }

    // 2. 检查 Redis 状态
    const redisKey = `${KEYGEN_STATUS_PREFIX}${userId}`;
    const statusData = await this.redisService.get(redisKey);

    let needsRetry = false;

    if (statusData) {
      try {
        const parsed = JSON.parse(statusData) as KeygenStatusData;
        const status = parsed.status;
        const updatedAt = parsed.updatedAt;

        // 检查是否超时
        const isTimeout =
          updatedAt &&
          Date.now() - new Date(updatedAt).getTime() > KEYGEN_TIMEOUT_MS;

        if (status === 'completed') {
          // Redis 显示 completed 但数据库钱包不完整 → 状态不一致，需要重试
          this.logger.warn(
            `[TASK] User ${userId} Redis status 'completed' but wallet incomplete`,
          );
          needsRetry = true;
        } else if (status === 'failed') {
          // 明确失败
          needsRetry = true;
        } else if (
          (status === 'generating' || status === 'deriving') &&
          isTimeout
        ) {
          // 超时
          this.logger.log(
            `[TASK] User ${userId} status '${status}' timed out`,
          );
          needsRetry = true;
        } else if (status === 'pending' && isTimeout) {
          // pending 超时
          needsRetry = true;
        }
        // generating/deriving/pending 且未超时 → 正常等待，不重试
      } catch (e) {
        // JSON 解析失败
        needsRetry = true;
      }
    } else {
      // Redis 无状态但数据库钱包不完整 → 需要触发生成
      needsRetry = true;
    }

    if (!needsRetry) {
      return false;
    }

    // 3. 尝试获取用户级别的分布式锁
    const lockKey = `${KEYGEN_LOCK_PREFIX}${userId}`;
    const gotLock = await this.redisService.tryLock(lockKey, 60);

    if (!gotLock) {
      this.logger.debug(
        `[TASK] User ${userId} lock not acquired, retry in progress`,
      );
      return false;
    }

    // 4. 执行重试
    await this.retryWalletGeneration(userId);
    return true;
  }

  /**
   * 检查用户是否在退避期内
   *
   * 指数退避策略：每次重试后等待时间翻倍
   * 1分钟 → 2分钟 → 4分钟 → 8分钟 → 16分钟 → 32分钟 → 60分钟（上限）
   */
  private async isInBackoffPeriod(userId: string): Promise<boolean> {
    const retryKey = `${KEYGEN_RETRY_PREFIX}${userId}`;
    const retryData = await this.redisService.get(retryKey);

    if (!retryData) {
      return false; // 第一次重试，无需等待
    }

    try {
      const record = JSON.parse(retryData) as RetryRecord;
      const nextRetryTime = new Date(record.nextRetryAt).getTime();
      const now = Date.now();

      if (now < nextRetryTime) {
        // 还在退避期内
        const remainingSeconds = Math.floor((nextRetryTime - now) / 1000);
        this.logger.debug(
          `[TASK] User ${userId} backoff: ${remainingSeconds}s remaining`,
        );
        return true;
      }

      return false;
    } catch (e) {
      return false;
    }
  }

  /**
   * 计算下次重试时间（指数退避）
   */
  private calculateNextRetryTime(retryCount: number): Date {
    // 指数退避：2^(retryCount-1) 分钟，最大 60 分钟
    const backoffMinutes = Math.min(
      Math.pow(2, retryCount - 1) * MIN_BACKOFF_MINUTES,
      MAX_BACKOFF_MINUTES,
    );

    const nextRetryTime = new Date(Date.now() + backoffMinutes * 60 * 1000);
    return nextRetryTime;
  }

  /**
   * 执行钱包生成重试
   *
   * 发布 MpcKeygenRequestedEvent 触发 MPC 服务生成钱包
   */
  private async retryWalletGeneration(userId: string): Promise<void> {
    this.logger.log(`[TASK] Retrying wallet generation for user: ${userId}`);

    try {
      // 1. 获取用户账号信息
      const userIdObj = UserId.create(BigInt(userId));
      const account = await this.userRepository.findById(userIdObj);

      if (!account) {
        this.logger.error(`[TASK] User ${userId} not found, cannot retry`);
        return;
      }

      // 2. 更新重试记录（包含指数退避时间）
      const retryCount = await this.updateRetryRecord(userId);

      // 3. 发布 MpcKeygenRequestedEvent 触发钱包生成（与注册流程使用相同的事件类型）
      const sessionId = crypto.randomUUID();
      await this.eventPublisher.publish(
        new MpcKeygenRequestedEvent({
          sessionId,
          userId: account.userId.toString(),
          accountSequence: account.accountSequence.value,
          username: `user_${account.accountSequence.value}`,
          threshold: 2,
          totalParties: 3,
          requireDelegate: true,
        }),
      );

      this.logger.log(
        `[TASK] Wallet generation retry #${retryCount} triggered for user: ${userId}, sessionId=${sessionId}`,
      );

      // 4. 更新 Redis 状态为 pending
      const statusData: KeygenStatusData = {
        status: 'pending',
        userId,
        updatedAt: new Date().toISOString(),
      };

      await this.redisService.set(
        `${KEYGEN_STATUS_PREFIX}${userId}`,
        JSON.stringify(statusData),
        60 * 60 * 24, // 24 小时
      );
    } catch (error) {
      this.logger.error(
        `[TASK] Failed to retry wallet generation for user ${userId}: ${error}`,
        error,
      );
    }
  }

  /**
   * 更新重试记录
   *
   * @returns 当前重试次数
   */
  private async updateRetryRecord(userId: string): Promise<number> {
    const retryKey = `${KEYGEN_RETRY_PREFIX}${userId}`;
    const retryData = await this.redisService.get(retryKey);

    let record: RetryRecord;
    let retryCount: number;

    if (!retryData) {
      // 第一次重试
      retryCount = 1;
      record = {
        userId,
        retryCount: 1,
        firstRetryAt: new Date().toISOString(),
        lastRetryAt: new Date().toISOString(),
        nextRetryAt: this.calculateNextRetryTime(1).toISOString(),
      };
    } else {
      const existing = JSON.parse(retryData) as RetryRecord;
      retryCount = existing.retryCount + 1;
      record = {
        ...existing,
        retryCount,
        lastRetryAt: new Date().toISOString(),
        nextRetryAt: this.calculateNextRetryTime(retryCount).toISOString(),
      };
    }

    // TTL 设置为 7 天，足够长以跟踪长期重试
    await this.redisService.set(
      retryKey,
      JSON.stringify(record),
      60 * 60 * 24 * 7, // 7 天
    );

    const nextRetryMinutes = Math.min(
      Math.pow(2, retryCount - 1) * MIN_BACKOFF_MINUTES,
      MAX_BACKOFF_MINUTES,
    );

    this.logger.log(
      `[TASK] User ${userId} retry #${retryCount}, next retry in ${nextRetryMinutes} minutes`,
    );

    return retryCount;
  }
}