import { Injectable, Logger } from '@nestjs/common';
import {
  NotificationGateway,
  WS_NOTIFICATION_EVENT,
} from './notification.gateway';

/**
 * WebSocket 通知事件发射器
 * @description 封装 NotificationGateway 的推送能力，提供面向业务层的事件发射接口。
 *              可被 Core 层的事件监听器注入使用，实现领域事件到 WebSocket 的桥接。
 */
@Injectable()
export class WsNotificationEmitter {
  private readonly logger = new Logger(WsNotificationEmitter.name);

  constructor(private readonly gateway: NotificationGateway) {}

  /**
   * 向指定用户推送 WebSocket 事件
   * @param userId - 目标用户 ID
   * @param event - 事件名称（默认使用 'notification'）
   * @param data - 事件负载数据
   */
  async emitToUser(
    userId: string,
    event: string = WS_NOTIFICATION_EVENT,
    data: unknown,
  ): Promise<void> {
    if (!userId || typeof userId !== 'string') {
      this.logger.warn('emitToUser called with invalid userId, skipping');
      return;
    }

    try {
      await this.gateway.sendToUser(userId, { event, data });
    } catch (error) {
      this.logger.error(
        `Failed to emit WebSocket event to userId=${userId}: ${error instanceof Error ? error.message : String(error)}`,
      );
    }
  }
}