A scheduler that calls a function with a unique identifier at a specific time

Scheduler.ts

import schedule from "node-schedule";
import { logger } from "./winston.js";

/**
 * A scheduler that calls a function with a unique identifier at a specific time
 * @param type_T - the type of the unique identifier to track each job
 */
export class Scheduler<T> {
  private jobs: Map<T, schedule.Job> = new Map();

  /**
   * Create a scheduler instance
   * @param callback - Function to be executed when a scheduled job fires. It takes in a unique identifier.
   */
  public constructor(private readonly callback: (unique_identifier: T) => Promise<void>) {}

  /**
   * Schedule a job to run on a specific date
   * @param date The date to run the callback. Returns with warning if the date is in the past.
   * @param uuid The unique identifier that will be passed into the callback
   */
  schedule(date: Date, uuid: T) {
    if (date.valueOf() < Date.now()) {
      logger.warn(`Not adding job uuid: ${uuid} scheduled for the past`);
      return;
    }

    this.cancel(uuid);

    const newJob = schedule.scheduleJob(date, () => {
      this.callback(uuid)
        .then(() => {
          logger.info(`Finished performing job: ${uuid} on ${date.valueOf()}`);
        })
        .catch(() => {
          logger.warn(`Failed performing job: ${uuid} on ${date.valueOf()}`);
        });
    });
    this.jobs.set(uuid, newJob);
  }

  /**
   * Cancel a job based on the unique identifier
   * @param uuid - The identifier of the job to cacnel
   */

  cancel(uuid: T) {
    const oldJob = this.jobs.get(uuid);
    if (oldJob) {
      oldJob.cancel();
      this.jobs.delete(uuid);
    }
  }

  /**
   * Load a batch of jobs
   * @param jobs An array containing the uuid of the jobs and the date to execute them.
   */
  loadJobs(jobs: { uuid: T; date: Date }[]) {
    for (const job of jobs) {
      this.schedule(job.date, job.uuid);
    }
  }

  print() {
    this.jobs.forEach((job, uuid) => {
      console.log(`${uuid} scheduled to be posted on ${job.nextInvocation()}`);
    });
  }
}