【Cognito】更新トークンによるIDトークン再取得処理について！

/**
   * This is used to get a session, either from the session object
   * or from  the local storage, or by using a refresh token
   *
   * @param {nodeCallback<CognitoUserSession>} callback Called on success or error.
   * @returns {void}
   */
  getSession(callback) {
    if (this.username == null) {
      return callback(new Error('Username is null. Cannot retrieve a new session'), null);
    }

    if (this.signInUserSession != null && this.signInUserSession.isValid()) {
      return callback(null, this.signInUserSession);
    }

    const keyPrefix = `CognitoIdentityServiceProvider.${this.pool.getClientId()}.${this.username}`;
    const idTokenKey = `${keyPrefix}.idToken`;
    const accessTokenKey = `${keyPrefix}.accessToken`;
    const refreshTokenKey = `${keyPrefix}.refreshToken`;
    const clockDriftKey = `${keyPrefix}.clockDrift`;

    if (this.storage.getItem(idTokenKey)) {
      const idToken = new CognitoIdToken({
        IdToken: this.storage.getItem(idTokenKey),
      });
      const accessToken = new CognitoAccessToken({
        AccessToken: this.storage.getItem(accessTokenKey),
      });
      const refreshToken = new CognitoRefreshToken({
        RefreshToken: this.storage.getItem(refreshTokenKey),
      });
      const clockDrift = parseInt(this.storage.getItem(clockDriftKey), 0) || 0;

      const sessionData = {
        IdToken: idToken,
        AccessToken: accessToken,
        RefreshToken: refreshToken,
        ClockDrift: clockDrift,
      };
      const cachedSession = new CognitoUserSession(sessionData);
      if (cachedSession.isValid()) {
        this.signInUserSession = cachedSession;
        return callback(null, this.signInUserSession);
      }

      if (!refreshToken.getToken()) {
        return callback(new Error('Cannot retrieve a new session. Please authenticate.'), null);
      }

      this.refreshSession(refreshToken, callback);
    } else {
      callback(new Error('Local storage is missing an ID Token, Please authenticate'), null);
    }

    return undefined;
  }

/**
   * This uses the refreshToken to retrieve a new session
   * @param {CognitoRefreshToken} refreshToken A previous session's refresh token.
   * @param {nodeCallback<CognitoUserSession>} callback Called on success or error.
   * @returns {void}
   */
  refreshSession(refreshToken, callback) {
    const authParameters = {};
    authParameters.REFRESH_TOKEN = refreshToken.getToken();
    const keyPrefix = `CognitoIdentityServiceProvider.${this.pool.getClientId()}`;
    const lastUserKey = `${keyPrefix}.LastAuthUser`;

    if (this.storage.getItem(lastUserKey)) {
      this.username = this.storage.getItem(lastUserKey);
      const deviceKeyKey = `${keyPrefix}.${this.username}.deviceKey`;
      this.deviceKey = this.storage.getItem(deviceKeyKey);
      authParameters.DEVICE_KEY = this.deviceKey;
    }

    const jsonReq = {
      ClientId: this.pool.getClientId(),
      AuthFlow: 'REFRESH_TOKEN_AUTH',
      AuthParameters: authParameters,
    };
    if (this.getUserContextData()) {
      jsonReq.UserContextData = this.getUserContextData();
    }
    this.client.request('InitiateAuth', jsonReq, (err, authResult) => {
      if (err) {
        if (err.code === 'NotAuthorizedException') {
          this.clearCachedUser();
        }
        return callback(err, null);
      }
      if (authResult) {
        const authenticationResult = authResult.AuthenticationResult;
        if (!Object.prototype.hasOwnProperty.call(authenticationResult, 'RefreshToken')) {
          authenticationResult.RefreshToken = refreshToken.getToken();
        }
        this.signInUserSession = this.getCognitoUserSession(authenticationResult);
        this.cacheTokens();
        return callback(null, this.signInUserSession);
      }
      return undefined;
    });
  }