type Task = { taskId: string; status: string; [key: string]: unknown };

/** A deadline stops this client; it does not cancel the server task. */
export async function pollTask(
  taskId: string,
  apiKey: string,
  options: {
    timeoutMs?: number;
    signal?: AbortSignal;
    fetch?: typeof fetch;
    now?: () => number;
    sleep?: (ms: number, signal: AbortSignal) => Promise<void>;
  } = {},
): Promise<Task> {
  const now = options.now ?? Date.now;
  const deadline = now() + (options.timeoutMs ?? 45 * 60_000);
  const request = options.fetch ?? fetch;
  const deadlineSignal = AbortSignal.timeout(options.timeoutMs ?? 45 * 60_000);
  const signal = options.signal
    ? AbortSignal.any([options.signal, deadlineSignal]) : deadlineSignal;
  const sleep = options.sleep ?? ((ms: number, signal: AbortSignal) => new Promise<void>((resolve, reject) => {
    signal.throwIfAborted();
    const abort = () => { clearTimeout(timer); reject(signal.reason); };
    const timer = setTimeout(() => { signal.removeEventListener('abort', abort); resolve(); }, ms);
    signal.addEventListener('abort', abort, { once: true });
  }));
  for (let attempt = 0; now() < deadline; attempt++) {
    signal.throwIfAborted();
    const response = await request(`https://api.omnapi.com/api/v1/tasks/${encodeURIComponent(taskId)}`, {
      headers: { 'x-api-key': apiKey },
      signal: AbortSignal.any([signal, AbortSignal.timeout(30_000)]),
    });
    let waitMs = Math.min(2000 * 2 ** Math.min(attempt, 4), 30_000);
    if (response.status === 429 || response.status === 503) {
      const retry = response.headers.get('Retry-After');
      if (retry) {
        const seconds = Number(retry);
        const delay = Number.isFinite(seconds) ? seconds * 1000 : Date.parse(retry) - now();
        if (Number.isFinite(delay)) waitMs = Math.max(waitMs, delay);
      }
    } else {
      if (!response.ok) throw new Error(`Task query HTTP ${response.status}; preserve taskId ${taskId}.`);
      const task = await response.json() as Task;
      if (typeof task.status !== 'string') throw new Error('Invalid task response; preserve the original receipt.');
      if (['COMPLETED', 'FAILED', 'CANCELLED'].includes(task.status)) return task;
    }
    if (now() + waitMs >= deadline) break;
    await sleep(waitMs, signal);
  }
  throw new Error(`Polling deadline reached; resume task ${taskId}, do not create a replacement.`);
}