export function beginSession(session, nowTs = Date.now()) {
  session.status = "running";
  session.startedAt = nowTs;
  session.endedAt = null;
  session.finishedByTimer = false;
  session.followUpStartedAt = null;
  session.pausedAt = null;
  session.totalPausedMs = 0;
  session.followUpPausedMs = 0;
  session.audioAnnouncements = [];
  return session;
}

export function finishSession(session, nowTs = Date.now()) {
  // Finishing while paused must fold the still-open pause segment into totalPausedMs the
  // same way resumeSession does - otherwise that final segment's duration is silently
  // dropped, and the session's own displayed elapsed time (getSessionTiming) keeps
  // growing after finish, since it would still be missing from totalPausedMs.
  if (session?.status === "paused" && session.pausedAt) {
    const pausedDuration = Math.max(0, nowTs - Number(session.pausedAt || nowTs));
    session.totalPausedMs = Math.max(0, Number(session.totalPausedMs || 0)) + pausedDuration;
  }
  session.status = "finished";
  session.endedAt = nowTs;
  session.finishedByTimer = false;
  session.followUpStartedAt = null;
  session.pausedAt = null;
  return session;
}

export function pauseSession(session, nowTs = Date.now()) {
  if (session?.status !== "running") return false;
  session.status = "paused";
  session.pausedAt = nowTs;
  return true;
}

export function resumeSession(session, nowTs = Date.now()) {
  if (session?.status !== "paused") return false;
  const pausedDuration = Math.max(0, nowTs - Number(session.pausedAt || nowTs));
  session.totalPausedMs = Math.max(0, Number(session.totalPausedMs || 0)) + pausedDuration;
  if (session.followUpStartedAt) {
    session.followUpPausedMs = Math.max(0, Number(session.followUpPausedMs || 0)) + pausedDuration;
  }
  session.pausedAt = null;
  session.status = "running";
  return true;
}