project-inter-server/src/repositories/InMemoryNotificationRepository.ts

import {
  Listener,
  NotificationEvent,
  NotificationLookupArguments,
  NotificationRepository,
  ScheduledNotification
} from "./NotificationRepository";
import { TupleKey } from "../types/TupleKey";

type DeviceIdSecondsThresholdAssociation = { [key: string]: number };

export class InMemoryNotificationRepository implements NotificationRepository {
  /**
   * An object of device ID arrays to deliver notifications to.
   * The key should be a combination of the shuttle ID and
   * stop ID, which can be generated using `TupleKey`.
   * The value is a dictionary of the device ID to the stored seconds threshold.
   * @private
   */
  private deviceIdsToDeliverTo: { [key: string]: DeviceIdSecondsThresholdAssociation } = {}

  private listeners: Listener[] = [];

  constructor() {
    this.getAllNotificationsForShuttleAndStopId = this.getAllNotificationsForShuttleAndStopId.bind(this);
    this.getSecondsThresholdForNotificationIfExists = this.getSecondsThresholdForNotificationIfExists.bind(this);
    this.deleteNotificationIfExists = this.deleteNotificationIfExists.bind(this);
    this.addOrUpdateNotification = this.addOrUpdateNotification.bind(this);
    this.isNotificationScheduled = this.isNotificationScheduled.bind(this);
    this.subscribeToNotificationChanges = this.subscribeToNotificationChanges.bind(this);
    this.unsubscribeFromNotificationChanges = this.unsubscribeFromNotificationChanges.bind(this);
  }

  async getAllNotificationsForShuttleAndStopId(shuttleId: string, stopId: string) {
    const tuple = new TupleKey(shuttleId, stopId);
    if (this.deviceIdsToDeliverTo[tuple.toString()] === undefined) {
      return [];
    }

    return Object.keys(this.deviceIdsToDeliverTo[tuple.toString()])
      .map((deviceId) => {
        return {
          shuttleId,
          stopId,
          deviceId,
          secondsThreshold: this.deviceIdsToDeliverTo[tuple.toString()][deviceId]
        }
      });
  }

  async getSecondsThresholdForNotificationIfExists({
    shuttleId,
    stopId,
    deviceId
  }: NotificationLookupArguments) {
    const tuple = new TupleKey(shuttleId, stopId);
    if (this.deviceIdsToDeliverTo[tuple.toString()] === undefined) {
      return null;
    }
    return this.deviceIdsToDeliverTo[tuple.toString()][deviceId];
  }

  async isNotificationScheduled(lookupArguments: NotificationLookupArguments): Promise<boolean> {
    const threshold = await this.getSecondsThresholdForNotificationIfExists(lookupArguments);
    return threshold !== null;
  }

  async addOrUpdateNotification({
    shuttleId,
    stopId,
    deviceId,
    secondsThreshold
  }: ScheduledNotification) {
    const tuple = new TupleKey(shuttleId, stopId);
    if (this.deviceIdsToDeliverTo[tuple.toString()] === undefined) {
      this.deviceIdsToDeliverTo[tuple.toString()] = {};
    }

    this.deviceIdsToDeliverTo[tuple.toString()][deviceId] = secondsThreshold;
    this.listeners.forEach((listener: Listener) => {
      const event: NotificationEvent = {
        event: 'addOrUpdate',
        notification: {
          shuttleId,
          stopId,
          deviceId,
          secondsThreshold
        },
      }

      listener(event);
    })
  }

  async deleteNotificationIfExists({
    deviceId,
    shuttleId,
    stopId
  }: NotificationLookupArguments) {
    const tupleKey = new TupleKey(shuttleId, stopId);
    if (
      this.deviceIdsToDeliverTo[tupleKey.toString()] === undefined
      || !(deviceId in this.deviceIdsToDeliverTo[tupleKey.toString()])
    ) {
      return;
    }

    const secondsThreshold = this.deviceIdsToDeliverTo[tupleKey.toString()][deviceId];
    delete this.deviceIdsToDeliverTo[tupleKey.toString()][deviceId];

    if (Object.keys(this.deviceIdsToDeliverTo[tupleKey.toString()]).length === 0) {
      // no more device IDs remaining for this key combination
      delete this.deviceIdsToDeliverTo[tupleKey.toString()];
    }

    this.listeners.forEach((listener) => {
      const event: NotificationEvent = {
        event: 'delete',
        notification: {
          deviceId,
          shuttleId,
          stopId,
          secondsThreshold
        }
      }

      listener(event);
    })
  }

  public subscribeToNotificationChanges(listener: Listener): void {
    const index = this.listeners.findIndex((existingListener) => existingListener == listener);
    if (index < 0) {
      this.listeners.push(listener);
    }
  }

  public unsubscribeFromNotificationChanges(listener: Listener): void {
    const index = this.listeners.findIndex((existingListener) => existingListener == listener);
    if (index >= 0) {
      this.listeners.splice(index, 1);
    }
  }
}