Function decodeOffsetCursor

server/src/training-agent/pagination.ts:17–28

(kind: string, cursor: string | undefined)

// (corrupt cursors duplicate items the caller already saw). An absent
// cursor returns 0 (start of pagination).
export function decodeOffsetCursor(kind: string, cursor: string | undefined): number | null {
  if (!cursor) return 0;
  try {
    const decoded = Buffer.from(cursor, 'base64url').toString('utf8');
    const m = new RegExp(`^${kind}:offset:(\\d+)$`).exec(decoded);
    if (!m) return null;
    const n = Number.parseInt(m[1], 10);
    return Number.isFinite(n) && n >= 0 ? n : null;
  } catch {
    return null;
  }
}