project-inter-server/src/notifications/senders/AppleNotificationSender.ts

import jwt from "jsonwebtoken";
import http2 from "http2";
import { ClientHttp2Session } from "node:http2";

interface APNsUrl {
  fullUrl: string;
  path: string;
  host: string;
}

export interface NotificationAlertArguments {
  title: string;
  body: string;
  customKeys?: any,
}

export class AppleNotificationSender {
  private apnsToken: string | undefined = undefined;
  private _lastRefreshedTimeMs: number | undefined = undefined;

  private client: ClientHttp2Session | undefined = undefined;

  constructor(private shouldActuallySendNotifications = true) {
    this.sendNotificationImmediately = this.sendNotificationImmediately.bind(this);
    this.lastReloadedTimeForAPNsIsTooRecent = this.lastReloadedTimeForAPNsIsTooRecent.bind(this);
    this.reloadAPNsTokenIfTimePassed = this.reloadAPNsTokenIfTimePassed.bind(this);
  }

  get lastRefreshedTimeMs(): number | undefined {
    return this._lastRefreshedTimeMs;
  }

  private lastReloadedTimeForAPNsIsTooRecent() {
    const thirtyMinutesMs = 1800000;
    return this._lastRefreshedTimeMs && Date.now() - this._lastRefreshedTimeMs < thirtyMinutesMs;
  }

  public reloadAPNsTokenIfTimePassed() {
    if (this.lastReloadedTimeForAPNsIsTooRecent()) {
      return;
    }

    const keyId = process.env.APNS_KEY_ID;
    const teamId = process.env.APNS_TEAM_ID;

    const privateKeyBase64 = process.env.APNS_PRIVATE_KEY;
    if (!privateKeyBase64) return;
    const privateKey = Buffer.from(privateKeyBase64, 'base64').toString('utf-8');

    const tokenHeader = {
      alg: "ES256",
      "kid": keyId,
    };

    const nowMs = Date.now();
    const claimsPayload = {
      "iss": teamId,
      "iat": Math.ceil(nowMs / 1000),  // APNs requires number of seconds since Epoch
    };

    this.apnsToken = jwt.sign(claimsPayload, privateKey, {
      algorithm: "ES256",
      header: tokenHeader
    });
    this._lastRefreshedTimeMs = nowMs;
  }

  /**
   * Send a notification immediately.
   * @param deviceId
   * @param notificationAlertArguments
   *
   * @return Boolean promise indicating whether the
   * notification was sent successfully.
   */
  public async sendNotificationImmediately(deviceId: string, notificationAlertArguments: NotificationAlertArguments) {
    if (!this.shouldActuallySendNotifications) {
      // pretend that the notification sent
      return true;
    }

    this.reloadAPNsTokenIfTimePassed();

    const bundleId = process.env.APNS_BUNDLE_ID;
    if (typeof bundleId !== "string") {
      throw new Error("APNS_BUNDLE_ID environment variable is not set correctly");
    }

    this.openConnectionIfNoneExists();

    const { path } = AppleNotificationSender.getAPNsFullUrlToUse(deviceId);

    const headers = {
      ':method': 'POST',
      ':path': path,
      'authorization': `bearer ${this.apnsToken}`,
      "apns-push-type": "alert",
      "apns-expiration": "0",
      "apns-priority": "10",
      "apns-topic": bundleId,
    };
    try {
      if (!this.client) { return false }
      const client = this.client;
      const req = client.request(headers);
      req.setEncoding('utf8');

      await new Promise<void>((resolve, reject) => {
        req.on('response', (headers, _flags) => {
          if (headers[":status"] !== 200) {
            reject(`APNs request failed with status ${headers[":status"]}`);
          }
          resolve();
        });

        const customKeys = {
          ...notificationAlertArguments.customKeys,
        }
        delete notificationAlertArguments.customKeys;

        // See https://developer.apple.com/documentation/usernotifications/generating-a-remote-notification
        // for notification payload examples
        const payload = JSON.stringify({
          aps: {
            alert: notificationAlertArguments,
            sound: "default"
          },
          ...customKeys,
        });
        req.write(payload);
        req.end();
      });
      return true;
    } catch(e) {
      console.error(e);
      return false;
    }
  }

  private openConnectionIfNoneExists() {
    const host = AppleNotificationSender.getAPNsHostToUse();

    if (!this.client) {
      this.client = http2.connect(host);
    }
  }

  private closeConnectionIfExists() {
    this.client?.close();
    this.client = undefined;
  }

  public static getAPNsFullUrlToUse(deviceId: string): APNsUrl {
    let hostToUse = this.getAPNsHostToUse();

    const path = "/3/device/" + deviceId;
    const fullUrl = hostToUse + path;

    return {
      fullUrl,
      host: hostToUse,
      path,
    };
  }

  public static getAPNsHostToUse() {
    // Construct the fetch request
    const devBaseUrl = "https://api.development.push.apple.com"
    const prodBaseUrl = "https://api.push.apple.com"

    let hostToUse = devBaseUrl;
    if (process.env.APNS_IS_PRODUCTION === "1") {
      hostToUse = prodBaseUrl;
    }
    return hostToUse;
  }
}