/**
 * Status messages are saved per device (`lotus-status-msg-<user>`) and
 * re-sent with every presence heartbeat, because a presence write that omits
 * `status_msg` clears it on Synapse. #187 DP3: a device never receives its own
 * user's presence changes made on other devices, so a status cleared elsewhere
 * stayed in its local copy and was re-published on the next heartbeat. The
 * heartbeat now reconciles with the server first (see usePresenceUpdater); this
 * module only tracks this device's own writes so that a fresh local save isn't
 * overridden by a server read that hasn't caught up yet.
 */

/** The status_msg Lotus sends for Do Not Disturb (see usePresenceUpdater). */
export const DND_STATUS_SENTINEL = 'dnd';

/** Trust this device's own copy for this long after it saved or cleared it. */
export const LOCAL_WRITE_GRACE_MS = 15_000;

let lastLocalWriteAt = 0;

/** Call whenever this device saves or clears its own status. */
export const noteLocalStatusWrite = (now: number = Date.now()): void => {
  lastLocalWriteAt = now;
};

export const getLastLocalStatusWrite = (): number => lastLocalWriteAt;

/**
 * Which status a heartbeat should send, given what the server says now.
 * `server` is undefined when the read failed. An offline server presence
 * (invisible mode) carries an empty status by design, so it isn't a clear.
 */
export const pickHeartbeatStatus = ({
  local,
  server,
  lastLocalWriteAt: writtenAt,
  now,
}: {
  local: string;
  server: { presence: string; status_msg?: string } | undefined;
  lastLocalWriteAt: number;
  now: number;
}): string => {
  // [Gitea #283] Lotus encodes Do Not Disturb as status_msg "dnd", so a device
  // leaving DND must not adopt that sentinel as the user's status — keep (and
  // so restore) the real one it holds locally.
  const mine = local === DND_STATUS_SENTINEL ? '' : local;
  if (!server || server.presence === 'offline') return mine;
  if (now - writtenAt < LOCAL_WRITE_GRACE_MS) return mine;
  if (server.status_msg === DND_STATUS_SENTINEL) return mine;
  return server.status_msg ?? '';
};