/**
 * Presence seam: tracks which thread each socket has in the foreground so the notification
 * projector can suppress push for a thread the recipient is actively viewing. Async so it can be
 * backed by Redis across replicas (prod) or an in-memory Map on a single instance (dev).
 */
export interface PresencePort {
  /** Record a socket's foregrounded thread (null when the window is blurred / no thread open). */
  setFocus(socketId: string, userId: string, threadId: string | null): Promise<void>;
  /** Forget everything about a socket (on disconnect). */
  clearSocket(socketId: string): Promise<void>;
  /** True if ANY of the user's sockets currently has this thread in the foreground. */
  isViewing(userId: string, threadId: string): Promise<boolean>;
}

export const PRESENCE_PORT = Symbol('PRESENCE_PORT');