authenticate(email, password) {
    return new Promise((resolved, reject) => {
      const userPool = new AWSCognito.CognitoUserPool(this._POOL_DATA);

      const authDetails = new AWSCognito.AuthenticationDetails({
        Username: email,
        Password: password
      });

      const cognitoUser = new AWSCognito.CognitoUser({
        Username: email,
        Pool: userPool
      });

      cognitoUser.authenticateUser(authDetails, {
        onSuccess: result => {
          resolved(result);
        },
        onFailure: err => {
          reject(err);
        },
        newPasswordRequired: userAttributes => {
          // User was signed up by an admin and must provide new
          // password and required attributes, if any, to complete
          // authentication.

          // the api doesn't accept this field back
          userAttributes.email = email;
          delete userAttributes.email_verified;

          cognitoUser.completeNewPasswordChallenge(password, userAttributes, {
            onSuccess: function(result) {},
            onFailure: function(error) {
              reject(error);
            }
          });
        }
      });
    });
  }