eatme/frontend/src/lib/liveSession.ts

import type { Session, StatsSummary } from '../api/types';

/**
 * The API computes worked/break durations at fetch time, so an open (still
 * running) session freezes until the next request. This recomputes an open
 * session's durations against a live clock so the UI can tick without polling.
 */
function recomputeOpenSession(session: Session, now: Date): Session {
  if (!session.open) return session;

  const start = new Date(session.clockIn).getTime();
  const breakMs = session.breaks.reduce((sum, b) => {
    const end = b.end ? new Date(b.end).getTime() : now.getTime();
    return sum + Math.max(0, end - new Date(b.start).getTime());
  }, 0);
  const workedMs = Math.max(0, now.getTime() - start - breakMs);

  return { ...session, breakMs, workedMs };
}

export function withLiveTime(stats: StatsSummary, now: Date): StatsSummary {
  let deltaWorked = 0;
  let deltaBreak = 0;

  const sessions = stats.sessions.map((s) => {
    if (!s.open) return s;
    const live = recomputeOpenSession(s, now);
    deltaWorked += live.workedMs - s.workedMs;
    deltaBreak += live.breakMs - s.breakMs;
    return live;
  });

  return {
    ...stats,
    sessions,
    totalWorkedMs: stats.totalWorkedMs + deltaWorked,
    totalBreakMs: stats.totalBreakMs + deltaBreak,
  };
}