import { DecoratorHandler, Dispatcher, fetch, MockAgent } from 'undici';

class LoggingHandler extends DecoratorHandler implements Dispatcher.DispatchHandlers {
  private requestBody = '';

  constructor(
    protected requestOptions: Dispatcher.DispatchOptions,
    protected handler: Dispatcher.DispatchHandlers,
  ) {
    super(handler);
  }

  onConnect(abort: (err?: Error) => void): void {
    if (this.handler.onConnect) {
      return this.handler.onConnect(abort);
    }
  }

  onBodySent(chunk: any, totalBytesSent: number) {
    try {
      this.requestBody += Buffer.from(chunk).toString();
    } catch (err) {
      console.debug('Failed to parse request body:', err);
    }
    if (this.handler.onBodySent) {
      this.handler.onBodySent(chunk, totalBytesSent);
    }
  }

  onComplete(trailers: string[] | null) {
    console.log('onComplete', this.requestBody); // In reality this would log to something like GCP with headers/response/status etc
    return this.handler.onComplete!(trailers);
  }
}

function createLoggingInterceptor() {
  return (dispatch: Dispatcher['dispatch']) => {
    return function Cache(requestOptions: Dispatcher.DispatchOptions, handler: Dispatcher.DispatchHandlers) {
      return dispatch(requestOptions, new LoggingHandler(requestOptions, handler));
    };
  };
}

describe('onBodySent', () => {
  it('onBodySent should be called when using MockAgent', async () => {
    const mockAgent = new MockAgent();
    mockAgent.disableNetConnect();
    const mockPool = mockAgent.get('http://mock.localhost');

    const onConnectSpy = jest.spyOn(LoggingHandler.prototype, 'onConnect');
    const onBodySentSpy = jest.spyOn(LoggingHandler.prototype, 'onBodySent');

    const dispatcher = mockAgent.compose(createLoggingInterceptor());

    const bodyString = JSON.stringify({
      amount: '100',
    });

    mockPool
      .intercept({
        path: '/test',
        method: 'POST',
        body: () => {
          return true;
        },
      })
      .reply(200, {
        test: 1,
      });

    const res = await fetch('http://mock.localhost/test', {
      dispatcher,
      method: 'POST',
      body: bodyString,
    });
    expect(await res.json()).toEqual({ test: 1 });
    expect(onConnectSpy).toHaveBeenCalledTimes(1);
    expect(onBodySentSpy).toHaveBeenCalledTimes(1); // fails
  });
});