/**
 * Runs the server's recurring tasks. Each module that needs one exports a
 * {@link Job}, and `main.ts` passes them all to {@link startJobs} when it runs
 * directly, so nothing recurs in the tests, which call a job's `run` when
 * they need it.
 *
 * @module
 */

/** A recurring task, exported by its module for `main.ts` to start. */
export interface Job {
  /** Names it in the log, as `[digest]`. */
  name: string;
  /** How long from one run's start to the next. */
  everyMs: number;
  /** How long after the start the first run waits, `everyMs` by default. */
  firstAfterMs?: number;
  /** Logs what it did itself, if anything; its errors are logged here. */
  run(): void | Promise<void>;
}

/**
 * Starts running each of `jobs` on its own timer. A run still going when the
 * next is due makes that one skip, and a run that throws or rejects is logged
 * and the next one runs anyway.
 */
export function startJobs(jobs: readonly Job[]): void {
  for (const job of jobs) {
    let running = false;
    const tick = async () => {
      if (running) return;
      running = true;
      try {
        await job.run();
      } catch (err) {
        console.error(`[${job.name}] run failed:`, err);
      } finally {
        running = false;
      }
    };
    setTimeout(() => {
      tick();
      setInterval(tick, job.everyMs);
    }, job.firstAfterMs ?? job.everyMs);
  }
}