import type { Session } from '@opencode-ai/sdk/v2';

const RECENT_SESSION_MAX_AGE_MS = 48 * 60 * 60 * 1000;

const isSubtaskSession = (session: Session): boolean => {
  return Boolean((session as Session & { parentID?: string | null }).parentID);
};

const isArchivedSession = (session: Session): boolean => {
  return Boolean(session.time?.archived);
};

const getSessionUpdatedAt = (session: Session): number => {
  const updated = session.time?.updated;
  const created = session.time?.created;
  if (typeof updated === 'number' && Number.isFinite(updated)) {
    return updated;
  }
  if (typeof created === 'number' && Number.isFinite(created)) {
    return created;
  }
  return 0;
};

// Recent contains non-archived root sessions that are active now or were
// updated within the retention window. The caller applies shared lifecycle
// ordering after this membership filter; batching ("Show more") handles long
// windows in the UI.
export const deriveRecentSessions = (
  sessions: Session[],
  activeSessionIds: ReadonlySet<string>,
  now = Date.now(),
): Session[] => {
  const minUpdatedAt = now - RECENT_SESSION_MAX_AGE_MS;
  return sessions.filter((session) => {
    if (isArchivedSession(session) || isSubtaskSession(session)) {
      return false;
    }
    return activeSessionIds.has(session.id) || getSessionUpdatedAt(session) >= minUpdatedAt;
  });
};