axios http auth client with refresh token

HttpAuth.ts

import axios, { AxiosInstance, AxiosRequestConfig } from "axios";
import createAuthRefreshInterceptor from "axios-auth-refresh";
import config from "../config";

export const generateAuthHeader = authToken =>
  `Token api_key=${config.API_KEY}, auth_token=${authToken}`;

interface Storage {
  get: (key: string) => Promise<string>;
  set: (key: string, data: string) => Promise<string>;
}
    
export class HttpAuth {
  http: AxiosInstance;

  constructor(private storage: Storage) {}

  async init() {
    if (this.http) return this.http;

    const authToken = await this.storage.get("AUTH_TOKEN");
    const refreshToken = await this.storage.get("REFRESH_TOKEN");

    this.http = axios.create({
      baseURL: `${config.API_HOST}/api/`,
      headers: {
        "Content-Type": "application/json",
        Authorization: generateAuthHeader(authToken)
      }
    });

    createAuthRefreshInterceptor(this.http, async failedRequest => {
      const response = await this.http.post("/users/refresh", {
        refresh_token: refreshToken
      });
      failedRequest.response.config.headers[
        "Authorization"
      ] = generateAuthHeader(response.data.auth_token);

      await this.storage.set("REFRESH_TOKEN", response.data.refresh_token);
      await this.storage.set("AUTH_TOKEN", response.data.auth_token);

      return Promise.resolve();
    });

    return this.http;
  }

  async get(url: string, config?: AxiosRequestConfig) {
    await this.init();
    return this.http.get(url, config);
  }

  async post(url: string, data?: any, config?: AxiosRequestConfig) {
    await this.init();
    this.http.post(url, data, config);
  }

  async put(url: string, data?: any, config?: AxiosRequestConfig) {
    await this.init();
    this.http.put(url, data, config);
  }

  async delete(url: string, config?: AxiosRequestConfig) {
    await this.init();
    this.http.delete(url, config);
  }
}