project-inter-server/src/loaders/TimedApiBasedRepositoryLoader.ts

import { GetterSetterRepository } from "../repositories/GetterSetterRepository";
import { IEta, IRoute, IShuttle, IStop, ISystem } from "../entities/entities";
import { ApiBasedRepositoryLoader } from "./ApiBasedRepositoryLoader";

// Ideas to break this into smaller pieces in the future:
// Have one repository data loader running for each supported system
// Each data loader independently updates data based on frequency of usage

// Notes on this: we only need to reload ETA data frequently
// Other data can be reloaded periodically
// Detailed list:
// - ETA: reload frequently or switch to write-through approach
// - Shuttles: reload every minute
// - Routes: reload every few minutes
// - Stops: reload every few minutes
// - OrderedStops: reload every few minutes
// - Systems: reload once a day

export class TimedApiBasedRepositoryLoader extends ApiBasedRepositoryLoader {
  private shouldBeRunning: boolean = false;
  private timer: any;

  readonly timeout = 10000;

  constructor(
    repository: GetterSetterRepository,
  ) {
    super(repository);
    this.startFetchDataAndUpdate = this.startFetchDataAndUpdate.bind(this);
  }

  public async start() {
    if (this.shouldBeRunning) {
      console.warn("DataLoader timer is already running");
      return;
    }

    this.shouldBeRunning = true;
    await this.startFetchDataAndUpdate();
  }

  public stop() {
    this.shouldBeRunning = false;
  }

  private async startFetchDataAndUpdate() {
    if (!this.shouldBeRunning) return;

    try {
      await this.repository.clearSystemData();
      await this.fetchAndUpdateSystemData();
      await this.repository.clearRouteData();
      await this.fetchAndUpdateRouteDataForExistingSystemsInRepository();
      await this.repository.clearStopData();
      await this.fetchAndUpdateStopAndPolylineDataForRoutesInExistingSystemsInRepository();
      await this.repository.clearShuttleData();
      await this.fetchAndUpdateShuttleDataForExistingSystemsInRepository();
      await this.repository.clearEtaData();
      await this.fetchAndUpdateEtaDataForExistingStopsForSystemsInRepository();
    } catch (e) {
      console.error(e);
    }

    this.timer = setTimeout(this.startFetchDataAndUpdate, this.timeout);
  }
}