src/interceptors/response.interceptor.ts

import {
  Injectable,
  NestInterceptor,
  ExecutionContext,
  CallHandler,
  StreamableFile,
} from '@nestjs/common';
import { Response } from 'express';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';
import { ApiResponse } from '../utils/response-wrapper.utils';

@Injectable()
export class ResponseInterceptor<T>
  implements NestInterceptor<T, ApiResponse<T> | T>
{
  intercept(
    context: ExecutionContext,
    next: CallHandler,
  ): Observable<ApiResponse<T> | T> {
    const response = context.switchToHttp().getResponse<Response>();
    return next.handle().pipe(
      map((data: T) => {
        if (data instanceof StreamableFile) return data;
        if (response.headersSent) return data;
        return {
          data,
          successful: true,
        };
      }),
    );
  }
}