export interface SSEEventClient {
  send: (data: string) => void;
  events?: Set<string>;
  userId?: number;
}

const clients = new Set<SSEEventClient>();

export function subscribe(client: SSEEventClient): () => void {
  clients.add(client);
  return () => clients.delete(client);
}

export function unsubscribe(client: SSEEventClient): void {
  clients.delete(client);
}

export function clientCount(): number {
  return clients.size;
}

export function broadcast(event: string, data: unknown): number {
  const payload = `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
  for (const client of clients) {
    if (client.events && !client.events.has(event)) continue;
    try {
      client.send(payload);
    } catch {
      clients.delete(client);
    }
  }
  return clients.size;
}

export function broadcastToUser(event: string, userId: number, data: unknown): number {
  const payload = `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
  const targetUserId = Number(userId);
  for (const client of clients) {
    if (client.userId !== targetUserId) continue;
    if (client.events && !client.events.has(event)) continue;
    try {
      client.send(payload);
    } catch {
      clients.delete(client);
    }
  }
  return clients.size;
}