import {
  Injectable,
  Logger,
  OnModuleInit,
  OnModuleDestroy,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { Kafka, Producer, logLevel } from 'kafkajs';
import {
  OutboxRepository,
  OutboxEvent,
} from '../persistence/repositories/outbox.repository';

/**
 * Outbox Publisher Service (B方案 - 消费方确认模式)
 *
 * 轮询 Outbox 表并发布事件到 Kafka
 * 使用消费方确认机制保证事件100%被处理
 *
 * 工作流程:
 * 1. 轮询 PENDING 状态的事件
 * 2. 发送到 Kafka，标记为 SENT（等待确认）
 * 3. 消费方处理成功后发送确认到 identity.events.ack
 * 4. 收到确认后标记为 CONFIRMED
 * 5. 超时未确认的事件重置为 PENDING 重发
 */
@Injectable()
export class OutboxPublisherService implements OnModuleInit, OnModuleDestroy {
  private readonly logger = new Logger(OutboxPublisherService.name);
  private kafka: Kafka;
  private producer: Producer;
  private isRunning = false;
  private pollInterval: NodeJS.Timeout | null = null;
  private timeoutCheckInterval: NodeJS.Timeout | null = null;
  private cleanupInterval: NodeJS.Timeout | null = null;
  private isConnected = false;

  // 配置
  private readonly pollIntervalMs: number;
  private readonly batchSize: number;
  private readonly cleanupIntervalMs: number;
  private readonly confirmationTimeoutMinutes: number;
  private readonly timeoutCheckIntervalMs: number;

  constructor(
    private readonly outboxRepository: OutboxRepository,
    private readonly configService: ConfigService,
  ) {
    this.pollIntervalMs = this.configService.get<number>(
      'OUTBOX_POLL_INTERVAL_MS',
      1000,
    );
    this.batchSize = this.configService.get<number>('OUTBOX_BATCH_SIZE', 100);
    this.cleanupIntervalMs = this.configService.get<number>(
      'OUTBOX_CLEANUP_INTERVAL_MS',
      3600000,
    ); // 1小时
    this.confirmationTimeoutMinutes = this.configService.get<number>(
      'OUTBOX_CONFIRMATION_TIMEOUT_MINUTES',
      5,
    );
    this.timeoutCheckIntervalMs = this.configService.get<number>(
      'OUTBOX_TIMEOUT_CHECK_INTERVAL_MS',
      60000,
    ); // 1分钟

    const brokers = this.configService
      .get<string>('KAFKA_BROKERS', 'localhost:9092')
      .split(',');
    const clientId = this.configService.get<string>(
      'KAFKA_CLIENT_ID',
      'identity-service',
    );

    this.kafka = new Kafka({
      clientId: `${clientId}-outbox`,
      brokers,
      logLevel: logLevel.WARN,
    });
    this.producer = this.kafka.producer();

    this.logger.log(
      `[OUTBOX] OutboxPublisher (B方案) configured: ` +
        `pollInterval=${this.pollIntervalMs}ms, batchSize=${this.batchSize}, ` +
        `confirmationTimeout=${this.confirmationTimeoutMinutes}min`,
    );
  }

  async onModuleInit() {
    this.logger.log('[OUTBOX] Connecting to Kafka...');
    try {
      await this.producer.connect();
      this.isConnected = true;
      this.logger.log('[OUTBOX] Connected to Kafka');
      this.start();
    } catch (error) {
      this.logger.error('[OUTBOX] Failed to connect to Kafka:', error);
      this.logger.warn(
        '[OUTBOX] OutboxPublisher will not start - events will accumulate in outbox table',
      );
    }
  }

  async onModuleDestroy() {
    this.stop();
    if (this.isConnected) {
      await this.producer.disconnect();
    }
  }

  /**
   * 启动轮询
   */
  start(): void {
    if (this.isRunning) {
      this.logger.warn('[OUTBOX] Publisher already running');
      return;
    }

    this.isRunning = true;
    this.logger.log('[OUTBOX] Starting outbox publisher (B方案)...');

    // 启动发布轮询
    this.pollInterval = setInterval(() => {
      this.processOutbox().catch((err) => {
        this.logger.error('[OUTBOX] Error processing outbox:', err);
      });
    }, this.pollIntervalMs);

    // 启动超时检查任务（B方案核心）
    this.timeoutCheckInterval = setInterval(() => {
      this.checkConfirmationTimeouts().catch((err) => {
        this.logger.error(
          '[OUTBOX] Error checking confirmation timeouts:',
          err,
        );
      });
    }, this.timeoutCheckIntervalMs);

    // 启动清理任务
    this.cleanupInterval = setInterval(() => {
      this.cleanup().catch((err) => {
        this.logger.error('[OUTBOX] Error cleaning up outbox:', err);
      });
    }, this.cleanupIntervalMs);

    this.logger.log(
      '[OUTBOX] Outbox publisher started (B方案 - 消费方确认模式)',
    );
  }

  /**
   * 停止轮询
   */
  stop(): void {
    if (!this.isRunning) return;

    this.isRunning = false;

    if (this.pollInterval) {
      clearInterval(this.pollInterval);
      this.pollInterval = null;
    }

    if (this.timeoutCheckInterval) {
      clearInterval(this.timeoutCheckInterval);
      this.timeoutCheckInterval = null;
    }

    if (this.cleanupInterval) {
      clearInterval(this.cleanupInterval);
      this.cleanupInterval = null;
    }

    this.logger.log('[OUTBOX] Outbox publisher stopped');
  }

  /**
   * 处理 Outbox 事件
   */
  async processOutbox(): Promise<void> {
    if (!this.isConnected) {
      return;
    }

    try {
      // 1. 获取待发布事件
      const pendingEvents = await this.outboxRepository.findPendingEvents(
        this.batchSize,
      );

      // 2. 获取需要重试的事件
      const retryEvents = await this.outboxRepository.findEventsForRetry(
        Math.floor(this.batchSize / 2),
      );

      const allEvents = [...pendingEvents, ...retryEvents];

      if (allEvents.length === 0) {
        return;
      }

      this.logger.debug(
        `[OUTBOX] Processing ${allEvents.length} events (${pendingEvents.length} pending, ${retryEvents.length} retry)`,
      );

      // 3. 逐个发布
      for (const event of allEvents) {
        await this.publishEvent(event);
      }
    } catch (error) {
      this.logger.error('[OUTBOX] Error in processOutbox:', error);
    }
  }

  /**
   * 发布单个事件 (B方案)
   *
   * 使用 producer.send() 发送到 Kafka，成功后标记为 SENT（等待消费方确认）
   * 只有收到消费方确认后才标记为 CONFIRMED
   */
  private async publishEvent(event: OutboxEvent): Promise<void> {
    try {
      this.logger.debug(
        `[OUTBOX] Publishing event ${event.id} to topic ${event.topic}`,
      );

      // 构造 Kafka 消息，包含 outboxId 用于确认
      const payload = {
        ...(event.payload as Record<string, unknown>),
        _outbox: {
          id: event.id.toString(),
          aggregateId: event.aggregateId,
          eventType: event.eventType,
        },
      };

      // 发布到 Kafka
      await this.producer.send({
        topic: event.topic,
        messages: [
          {
            key: event.key,
            value: JSON.stringify(payload),
          },
        ],
      });

      // B方案：标记为 SENT（等待消费方确认）
      await this.outboxRepository.markAsSent(event.id);

      this.logger.log(
        `[OUTBOX] → Event ${event.id} sent to ${event.topic} (awaiting consumer confirmation)`,
      );
    } catch (error) {
      const errorMessage =
        error instanceof Error ? error.message : String(error);
      this.logger.error(
        `[OUTBOX] ✗ Failed to publish event ${event.id}: ${errorMessage}`,
      );

      // 标记为失败并安排重试
      await this.outboxRepository.markAsFailed(event.id, errorMessage);
    }
  }

  /**
   * 检查确认超时的事件 (B方案核心)
   *
   * 将超时未确认的 SENT 事件重置为 PENDING 以便重发
   */
  private async checkConfirmationTimeouts(): Promise<void> {
    if (!this.isConnected) {
      return;
    }

    try {
      const timedOutEvents = await this.outboxRepository.findSentEventsTimedOut(
        this.confirmationTimeoutMinutes,
        this.batchSize,
      );

      if (timedOutEvents.length === 0) {
        return;
      }

      this.logger.warn(
        `[OUTBOX] Found ${timedOutEvents.length} events without confirmation after ${this.confirmationTimeoutMinutes} minutes`,
      );

      for (const event of timedOutEvents) {
        await this.outboxRepository.resetSentToPending(event.id);
        this.logger.warn(
          `[OUTBOX] Event ${event.id} reset to PENDING for retry (retry #${event.retryCount + 1})`,
        );
      }
    } catch (error) {
      this.logger.error(
        '[OUTBOX] Error checking confirmation timeouts:',
        error,
      );
    }
  }

  /**
   * 清理旧事件
   */
  private async cleanup(): Promise<void> {
    const retentionDays = this.configService.get<number>(
      'OUTBOX_RETENTION_DAYS',
      7,
    );
    await this.outboxRepository.cleanupOldEvents(retentionDays);
  }

  /**
   * 手动触发处理（用于测试或紧急情况）
   */
  async triggerProcessing(): Promise<void> {
    this.logger.log('[OUTBOX] Manual processing triggered');
    await this.processOutbox();
  }

  /**
   * 获取统计信息
   */
  async getStats(): Promise<{
    isRunning: boolean;
    isConnected: boolean;
    pending: number;
    sent: number;
    confirmed: number;
    failed: number;
  }> {
    const stats = await this.outboxRepository.getStats();
    return {
      isRunning: this.isRunning,
      isConnected: this.isConnected,
      ...stats,
    };
  }
}