import axios from 'axios';

interface TokenResponse {
  access_token: string;
  expires_in: number;
  token_type: string;
}

export default class CognitoClient {
  tokenEndpont: string;
  clientId: string;
  clientSecret: string;
  scope: string;
  expiresAt: number;
  accessToken: string;

  constructor(
    tokenEndpoint: string,
    clientId: string,
    clientSecret: string,
    scope: string,
  ) {
    this.tokenEndpont = `${tokenEndpoint}/oauth2/token`;
    this.clientId = clientId;
    this.clientSecret = clientSecret;
    this.scope = scope;
    this.accessToken = '';
    this.expiresAt = 0;
  }

  private getPostData(): URLSearchParams {
    const params = new URLSearchParams();
    params.append('grant_type', 'client_credentials');
    params.append('client_id', this.clientId);
    params.append('scope', this.scope);
    return params;
  }

  public async getToken(): Promise<string> {
    const now = Date.now();
    if (this.expiresAt < now) {
      await this.getNewToken();
    }
    console.log('Getting cached token');
    return this.accessToken;
  }

  private async getNewToken(): Promise<void> {
    console.log('Getting new token');
    const authString =
      'Basic ' +
      Buffer.from(this.clientId + ':' + this.clientSecret).toString('base64');
    const res: TokenResponse = await axios
      .post(this.tokenEndpont, this.getPostData(), {
        headers: {
          'Content-Type': 'application/x-www-form-urlencoded',
          Authorization: authString,
        },
      })
      .then((r) => r.data);

    this.accessToken = res.access_token;
    this.expiresAt = Date.now() + res.expires_in * 1e3;
  }
}