/** A browser's push subscription (Web Push), as the browser hands it over. */
export interface PushSubscriptionRecord {
  userId: string;
  /** The push service URL of that browser on that device: unique. */
  endpoint: string;
  keys: { p256dh: string; auth: string };
  createdAt: string;
}

/** What the service worker shows: a title, a line and where a tap goes. */
export interface PushPayload {
  title: string;
  body: string;
  /** A path in the web app, e.g. `/p/WEB/issues/WEB-12`. */
  url: string;
  /** Replaces an earlier notification with the same tag on the device. */
  tag: string;
}

/**
 * Sends Web Push messages (VAPID). Without keys configured it is off and
 * nobody is offered push.
 */
export abstract class PushSender {
  /** The VAPID public key browsers subscribe with; null: push is off. */
  abstract get publicKey(): string | null;
  /** `gone`: the browser dropped the subscription; forget it. */
  abstract send(
    subscription: PushSubscriptionRecord,
    payload: PushPayload,
  ): Promise<'sent' | 'gone'>;
}