import {
  CallHandler,
  ExecutionContext,
  Injectable,
  NestInterceptor,
} from '@nestjs/common';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';
import { ApiResponse } from '../dto/api-response.dto';

/**
 * 全局统一响应拦截器
 * 把所有 controller 返回值包装成 { code, msg, data } 结构
 */
@Injectable()
export class TransformInterceptor<T>
  implements NestInterceptor<T, ApiResponse<T>>
{
  intercept(
    context: ExecutionContext,
    next: CallHandler<T>,
  ): Observable<ApiResponse<T>> {
    return next.handle().pipe(
      map((data) => {
        // 如果已经是 ApiResponse，则原样返回
        if (data instanceof ApiResponse) {
          return data;
        }
        return ApiResponse.success(data) as ApiResponse<T>;
      }),
    );
  }
}