Class to ease process of polling an endpoint

poller.ts

import axios, { AxiosRequestConfig, AxiosError, AxiosResponse, CancelTokenSource } from 'axios';

interface PollOptions<PollResponse, CompleteResponse> {
  interval: number;
  shouldContinuePolling: (response: PollResponse | CompleteResponse) => response is PollResponse;
  isComplete: (response: PollResponse | CompleteResponse) => response is CompleteResponse;
  onStart?: () => any;
  onStop?: () => any;
  onError: (error: AxiosError) => any;
  onComplete: (response: CompleteResponse) => any;
}

export class Poller<PollResponse, CompleteResponse> {
  private axiosConfig: AxiosRequestConfig;
  private options: PollOptions<PollResponse, CompleteResponse>;
  private polling: boolean = false;
  private timeout?: number;
  private cancelTokenSource?: CancelTokenSource;

  public constructor(axiosConfig: AxiosRequestConfig, options: PollOptions<PollResponse, CompleteResponse>) {
    this.axiosConfig = axiosConfig;
    this.options = options;
  }

  public start() {
    if (!this.polling) {
      this.polling = true;

      this.startPoll();

      if (typeof this.options.onStart === 'function') {
        this.options.onStart();
      }
    }
  }

  public stop() {
    if (this.polling) {
      this.polling = false;
      window.clearTimeout(this.timeout);

      if (this.cancelTokenSource) {
        this.cancelTokenSource.cancel();
      }

      if (typeof this.options.onStop === 'function') {
        this.options.onStop();
      }
    }
  }

  private startPoll() {
    this.cancelTokenSource = axios.CancelToken.source();

    axios
      .request({
        ...this.axiosConfig,
        cancelToken: this.cancelTokenSource.token
      })
      .then(
        (response: AxiosResponse) => {
          if (this.options.shouldContinuePolling(response.data)) {
            this.timeout = window.setTimeout(() => {
              this.startPoll();
            }, this.options.interval);
          } else if (this.options.isComplete(response.data)) {
            this.options.onComplete(response.data);
          } else {
            throw new Error('Polling was not complete, and should not continue');
          }
        },
        (error: AxiosError) => {
          if (axios.isCancel(error)) {
            console.error('Polling cancelled');
          } else {
            this.options.onError(error);
          }
        }
      );
  }
}