// lib/realtime/NotificationManager.ts
import { Client } from 'pg';
import { EventEmitter } from 'events';

interface NotificationPayload {
  id: string;
  user_id: string;
  title: string;
  message: string;
  type: string;
  related_record_id?: string;
  related_record_type?: string;
  is_read: boolean;
  created_at: string;
}

interface NotificationReadPayload {
  id: string;
  user_id: string;
  is_read: boolean;
  read_at?: string;
}

class NotificationManager extends EventEmitter {
  private client: Client | null = null;
  private isConnected = false;
  private reconnectAttempts = 0;
  private maxReconnectAttempts = 5;
  private reconnectDelay = 1000;
  private reconnectTimeout: NodeJS.Timeout | null = null;

  constructor() {
    super();
    this.setMaxListeners(100); // SSE 연결이 많을 수 있으므로 제한 증가
    this.connect();
  }

  private async connect() {
    try {
      // 기존 연결이 있으면 정리
      if (this.client) {
        try {
          await this.client.end();
        } catch (error) {
          console.warn('Error closing existing connection:', error);
        }
      }

      this.client = new Client({
        connectionString: process.env.DATABASE_URL,
        application_name: 'notification_listener',
        // 연결 유지 설정
        keepAlive: true,
        keepAliveInitialDelayMillis: 10000,
      });

      await this.client.connect();
      
      // LISTEN 채널 구독
      await this.client.query('LISTEN new_notification');
      await this.client.query('LISTEN notification_read');
      
      console.log('NotificationManager: PostgreSQL LISTEN connected');

      // 알림 수신 처리
      this.client.on('notification', (msg) => {
        try {
          if (msg.channel === 'new_notification') {
            const payload: NotificationPayload = JSON.parse(msg.payload || '{}');
            console.log('New notification received:', payload.id, 'for user:', payload.user_id);
            this.emit('newNotification', payload);
          } else if (msg.channel === 'notification_read') {
            const payload: NotificationReadPayload = JSON.parse(msg.payload || '{}');
            console.log('Notification read:', payload.id, 'by user:', payload.user_id);
            this.emit('notificationRead', payload);
          }
        } catch (error) {
          console.error('Error parsing notification payload:', error);
        }
      });

      // 연결 오류 처리
      this.client.on('error', (error) => {
        console.error('PostgreSQL LISTEN error:', error);
        this.isConnected = false;
        this.scheduleReconnect();
      });

      // 연결 종료 처리
      this.client.on('end', () => {
        console.log('PostgreSQL LISTEN connection ended');
        this.isConnected = false;
        this.scheduleReconnect();
      });

      this.isConnected = true;
      this.reconnectAttempts = 0;
      
      // 연결 성공 이벤트 발송
      this.emit('connected');
      
    } catch (error) {
      console.error('Failed to connect NotificationManager:', error);
      this.isConnected = false;
      this.scheduleReconnect();
    }
  }

  private scheduleReconnect() {
    // 이미 재연결이 예약되어 있으면 무시
    if (this.reconnectTimeout) {
      return;
    }

    if (this.reconnectAttempts >= this.maxReconnectAttempts) {
      console.error('Max reconnection attempts reached for NotificationManager');
      this.emit('maxReconnectAttemptsReached');
      return;
    }

    this.reconnectAttempts++;
    const delay = this.reconnectDelay * Math.pow(2, this.reconnectAttempts - 1);
    
    console.log(`Scheduling NotificationManager reconnection in ${delay}ms (attempt ${this.reconnectAttempts})`);
    
    this.reconnectTimeout = setTimeout(() => {
      this.reconnectTimeout = null;
      this.connect();
    }, delay);
  }

  public async disconnect() {
    if (this.reconnectTimeout) {
      clearTimeout(this.reconnectTimeout);
      this.reconnectTimeout = null;
    }

    if (this.client) {
      try {
        await this.client.end();
      } catch (error) {
        console.warn('Error disconnecting NotificationManager:', error);
      }
      this.client = null;
    }
    
    this.isConnected = false;
    this.emit('disconnected');
  }

  public getConnectionStatus(): boolean {
    return this.isConnected && this.client !== null;
  }

  public getReconnectAttempts(): number {
    return this.reconnectAttempts;
  }

  // 강제 재연결 (관리자 API용)
  public async forceReconnect() {
    console.log('Forcing NotificationManager reconnection...');
    this.reconnectAttempts = 0;
    if (this.reconnectTimeout) {
      clearTimeout(this.reconnectTimeout);
      this.reconnectTimeout = null;
    }
    await this.disconnect();
    await this.connect();
  }

  // 연결 상태 체크 (헬스체크용)
  public async healthCheck(): Promise<{ status: string; details: any }> {
    try {
      if (!this.client || !this.isConnected) {
        return {
          status: 'unhealthy',
          details: {
            connected: false,
            reconnectAttempts: this.reconnectAttempts,
            maxReconnectAttempts: this.maxReconnectAttempts
          }
        };
      }

      // 간단한 쿼리로 연결 상태 확인
      await this.client.query('SELECT 1');
      
      return {
        status: 'healthy',
        details: {
          connected: true,
          reconnectAttempts: this.reconnectAttempts,
          uptime: process.uptime()
        }
      };
    } catch (error) {
      return {
        status: 'unhealthy',
        details: {
          connected: false,
          error: error instanceof Error ? error.message : 'Unknown error',
          reconnectAttempts: this.reconnectAttempts
        }
      };
    }
  }
}

// 싱글톤 인스턴스
const notificationManager = new NotificationManager();

// 프로세스 종료 시 정리
process.on('SIGINT', async () => {
  console.log('Shutting down NotificationManager...');
  await notificationManager.disconnect();
});

process.on('SIGTERM', async () => {
  console.log('Shutting down NotificationManager...');
  await notificationManager.disconnect();
});

export default notificationManager;