Javascript Server Time handler

server-time-handler.ts

import ko from 'knockout';

import {getLogger} from 'Util/Logger';

export const serverTimeHandler = {
  computeTimeOffset(serverTimeString: string): void {
    const timeOffset = Date.now() - new Date(serverTimeString).valueOf();
    this.timeOffset(timeOffset);
    this.logger.log(`Current backend time is '${serverTimeString}'. Time offset updated to '${this.timeOffset()}' ms`);
  },

  getTimeOffset(): number {
    if (this.timeOffset() === undefined) {
      this.logger.warn('Trying to get server/client time offset, but no server time has been set.');
      return 0;
    }
    return this.timeOffset();
  },

  logger: getLogger('serverTimeHandler'),
  timeOffset: ko.observable(undefined) as ko.Observable<number>,

  /**
   * Converts a server timestamp to a local timestamp.
   * @param serverTimestamp the server timestamp to convert
   * @returns the timestamp adjusted with the client/server time shift
   */
  toLocalTimestamp(serverTimestamp = Date.now()): number {
    return serverTimestamp + this.getTimeOffset();
  },

  /**
   * Converts a local timestamp to a server timestamp.
   * @param localTimestamp the local timestamp to convert
   * @returns the timestamp adjusted with the client/server time shift
   */
  toServerTimestamp(localTimestamp = Date.now()): number {
    return localTimestamp - this.getTimeOffset();
  },
};

export type ServerTimeHandler = typeof serverTimeHandler;