JobHandlers

type OnTimeoutCallback = () => number | void | undefined;

interface JobContext {
  /** Proactively reset the timeout deadline.
   *  If ms is provided, sets deadline to ms from now.
   *  If omitted, resets to the original timeoutMs. */
  prolong: (ms?: number) => void;

  /** Register a callback invoked when timeout fires (before abort).
   *  Return a number (ms) to extend, or nothing to let timeout proceed.
   *  The callback may be called multiple times if the job keeps extending. */
  onTimeout: (callback: OnTimeoutCallback) => void;
}

type JobHandler<PayloadMap, T extends keyof PayloadMap> = (
  payload: PayloadMap[T],
  signal: AbortSignal,
  ctx: JobContext,
) => Promise<void>;

// Map of job types to handlers

export type JobHandlers<PayloadMap> = {
  [K in keyof PayloadMap]: JobHandler<PayloadMap, K>;
};

const handlers = {
  email: async (payload, signal) => {
    // send email
  },
  generateReport: async (payload, signal, { prolong }) => {
    // prolong the timeout before a heavy step
    prolong(60_000);
    // generate report
  },
  processData: async (payload, signal, { onTimeout }) => {
    let progress = 0;
    onTimeout(() => {
      if (progress < 100) return 30_000; // extend if still working
    });
    // process data in chunks, updating progress
  },
};