18F/identity-idp

import { request, ResponseError } from '@18f/identity-request';

export interface SessionLiveStatusResponse {
  /**
   * Whether the session is still active.
   */
  live: true;

  /**
   * ISO8601-formatted date string for session timeout.
   */
  timeout: string;
}

export interface SessionTimedOutStatusResponse {
  /**
   * Whether the session is still active.
   */
  live: false;

  /**
   * ISO8601-formatted date string for session timeout.
   */
  timeout: null;
}

type SessionStatusResponse = SessionLiveStatusResponse | SessionTimedOutStatusResponse;

interface SessionLiveStatus {
  /**
   * Whether the session is still active.
   */
  isLive: true;

  /**
   * ISO8601-formatted date string for session timeout.
   */
  timeout: Date;
}

interface SessionTimedOutStatus {
  /**
   * Whether the session is still active.
   */
  isLive: false;

  /**
   * ISO8601-formatted date string for session timeout.
   */
  timeout?: undefined;
}

export type SessionStatus = SessionLiveStatus | SessionTimedOutStatus;

function mapSessionStatusResponse<R extends SessionLiveStatusResponse>(
  response: R,
): SessionLiveStatus;
function mapSessionStatusResponse<R extends SessionTimedOutStatusResponse>(
  response: R,
): SessionTimedOutStatus;
function mapSessionStatusResponse<
  R extends SessionLiveStatusResponse | SessionTimedOutStatusResponse,
>({ live, timeout }: R): SessionLiveStatus | SessionTimedOutStatus {
  return live ? { isLive: true, timeout: new Date(timeout) } : { isLive: false };
}

/**
 * Handles a thrown error from a session endpoint, interpreting an unauthorized request (401) as
 * effectively an inactive session. Any other error is re-thrown as being unexpected.
 *
 * @param error Error thrown from request.
 */
function handleUnauthorizedStatusResponse(error: ResponseError) {
  if (error.status === 401) {
    return { live: false, timeout: null };
  }

  throw error;
}

/**
 * Request the current session status. Returns a promise resolving to the current session status.
 *
 * @param sessionsURL The URL for the session API
 * @return A promise resolving to the current session status
 */
export const requestSessionStatus = (sessionsURL: string): Promise<SessionStatus> =>
  request<SessionStatusResponse>(sessionsURL)
    .catch(handleUnauthorizedStatusResponse)
    .then(mapSessionStatusResponse);

/**
 * Request that the current session be kept alive. Returns a promise resolving to the updated
 * session status.
 *
 * @param sessionsURL The URL for the session API
 * @return A promise resolving to the updated session status.
 */
export const extendSession = (sessionsURL: string): Promise<SessionStatus> =>
  request<SessionStatusResponse>(sessionsURL, { method: 'PUT' })
    .catch(handleUnauthorizedStatusResponse)
    .then(mapSessionStatusResponse);