project-inter-server/src/repositories/shuttle/eta/InMemorySelfUpdatingETARepository.ts

import { SelfUpdatingETARepository } from "./SelfUpdatingETARepository";
import { ShuttleGetterRepository, ShuttleRepositoryEvent, ShuttleStopArrival, ShuttleTravelTimeDataIdentifier, ShuttleTravelTimeDateFilterArguments } from "../ShuttleGetterRepository";
import { BaseInMemoryETARepository } from "./BaseInMemoryETARepository";
import { IShuttle } from "../../../entities/ShuttleRepositoryEntities";

export class InMemorySelfUpdatingETARepository extends BaseInMemoryETARepository implements SelfUpdatingETARepository {
  private referenceTime: Date | null = null;
  private travelTimeData: Map<string, Array<{ timestamp: number; seconds: number }>> = new Map();

  constructor(
    readonly shuttleRepository: ShuttleGetterRepository
  ) {
    super();

    this.setReferenceTime = this.setReferenceTime.bind(this);
    this.getAverageTravelTimeSeconds = this.getAverageTravelTimeSeconds.bind(this);
    this.startListeningForUpdates = this.startListeningForUpdates.bind(this);
    this.handleShuttleUpdate = this.handleShuttleUpdate.bind(this);
    this.handleShuttleWillArriveAtStop = this.handleShuttleWillArriveAtStop.bind(this);
  }

  setReferenceTime(referenceTime: Date): void {
    this.referenceTime = referenceTime;
  }

  async getAverageTravelTimeSeconds(
    { routeId, fromStopId, toStopId }: ShuttleTravelTimeDataIdentifier,
    { from, to }: ShuttleTravelTimeDateFilterArguments
  ): Promise<number | undefined> {
    const key = `${routeId}:${fromStopId}:${toStopId}`;
    const dataPoints = this.travelTimeData.get(key);

    if (!dataPoints || dataPoints.length === 0) {
      return undefined;
    }

    const fromTimestamp = from.getTime();
    const toTimestamp = to.getTime();

    const filteredPoints = dataPoints.filter(
      (point) => point.timestamp >= fromTimestamp && point.timestamp <= toTimestamp
    );

    if (filteredPoints.length === 0) {
      return undefined;
    }

    const sum = filteredPoints.reduce((acc, point) => acc + point.seconds, 0);
    return sum / filteredPoints.length;
  }

  startListeningForUpdates(): void {
    this.shuttleRepository.addListener(ShuttleRepositoryEvent.SHUTTLE_UPDATED, this.handleShuttleUpdate);
    this.shuttleRepository.addListener(ShuttleRepositoryEvent.SHUTTLE_WILL_ARRIVE_AT_STOP, this.handleShuttleWillArriveAtStop);
  }

  private async handleShuttleUpdate(shuttle: IShuttle): Promise<void> {
    const lastStop = await this.shuttleRepository.getShuttleLastStopArrival(shuttle.id);
    if (!lastStop) return;

    const lastOrderedStop = await this.shuttleRepository.getOrderedStopByRouteAndStopId(shuttle.routeId, lastStop.stopId);
    const nextStop = lastOrderedStop?.nextStop;
    if (!nextStop) return;

    let referenceCurrentTime = new Date();
    if (this.referenceTime != null) {
      referenceCurrentTime = this.referenceTime;
    }
    const oneWeekAgo = new Date(referenceCurrentTime.getTime() - (60 * 60 * 24 * 7 * 1000));

    const travelTimeSeconds = await this.getAverageTravelTimeSeconds({
      routeId: shuttle.routeId,
      fromStopId: lastStop.stopId,
      toStopId: nextStop.stopId,
    }, {
      from: oneWeekAgo,
      to: new Date(oneWeekAgo.getTime() + (60 * 60 * 1000))
    });
    if (travelTimeSeconds == undefined) return;

    const elapsedTimeMs = referenceCurrentTime.getTime() - lastStop.timestamp.getTime();
    const predictedTimeSeconds = travelTimeSeconds - (elapsedTimeMs / 1000);

    await this.addOrUpdateEta({
      secondsRemaining: predictedTimeSeconds,
      shuttleId: shuttle.id,
      stopId: nextStop.stopId,
      systemId: nextStop.systemId,
      updatedTime: new Date(),
    });
  }

  private async handleShuttleWillArriveAtStop(shuttleArrival: ShuttleStopArrival): Promise<void> {
    const lastStopTimestamp = await this.shuttleRepository.getShuttleLastStopArrival(shuttleArrival.shuttleId);
    if (lastStopTimestamp) {
      // disallow cases where this gets triggered multiple times
      if (lastStopTimestamp.stopId === shuttleArrival.stopId) return;

      const shuttle = await this.shuttleRepository.getShuttleById(lastStopTimestamp.shuttleId);
      if (!shuttle) return;

      const routeId = shuttle.routeId;
      const fromStopId = lastStopTimestamp.stopId;
      const toStopId = shuttleArrival.stopId;

      const travelTimeSeconds = (shuttleArrival.timestamp.getTime() - lastStopTimestamp.timestamp.getTime()) / 1000;
      await this.addTravelTimeDataPoint({ routeId, fromStopId, toStopId }, travelTimeSeconds, shuttleArrival.timestamp.getTime());
    }
  }

  private async addTravelTimeDataPoint(
    { routeId, fromStopId, toStopId }: ShuttleTravelTimeDataIdentifier,
    travelTimeSeconds: number,
    timestamp = Date.now(),
  ): Promise<void> {
    const key = `${routeId}:${fromStopId}:${toStopId}`;
    const dataPoints = this.travelTimeData.get(key) || [];
    dataPoints.push({ timestamp, seconds: travelTimeSeconds });
    this.travelTimeData.set(key, dataPoints);
  }
}