/**
 * Offset between this machine's clock and the server's, in milliseconds.
 *
 * Activity timestamps (a Spotify track's start and end, for instance) are
 * computed on the server and rendered here. A machine whose clock is a minute
 * off would draw the progress bar a minute out of place — or past the end of
 * the track — with nothing obviously wrong on screen.
 */
let offsetMs = 0;

/** Called on every `ready`: the round trip is short enough to ignore. */
export function setServerTime(serverTime: number): void {
  offsetMs = Date.now() - serverTime;
}

/** `Date.now()` as the server would report it. */
export function serverNow(): number {
  return Date.now() - offsetMs;
}