const clients = new Map();

function subscribe(req, res) {
  const id = `${Date.now()}:${Math.random().toString(16).slice(2)}`;
  const user = req.session?.user || null;
  const client = { id, res, user, connectedAt: Date.now() };
  clients.set(id, client);

  res.writeHead(200, {
    "Content-Type": "text/event-stream",
    "Cache-Control": "no-store, no-transform",
    Connection: "keep-alive",
    "X-Accel-Buffering": "no"
  });
  send(client, "server:status", {
    status: "connected",
    message: "Lumi event stream connected.",
    connected_at: client.connectedAt
  });

  const keepAlive = setInterval(() => {
    send(client, "server:status", { status: "heartbeat", at: Date.now() });
  }, 25000);

  req.on("close", () => {
    clearInterval(keepAlive);
    clients.delete(id);
  });
}

function publish(event, payload = {}, options = {}) {
  let delivered = 0;
  for (const client of clients.values()) {
    if (!canReceive(client.user, options)) continue;
    send(client, event, payload);
    delivered += 1;
  }
  return delivered;
}

function send(client, event, payload) {
  try {
    client.res.write(`event: ${event}\n`);
    client.res.write(`data: ${JSON.stringify({ ...payload, event, at: Date.now() })}\n\n`);
  } catch {
    clients.delete(client.id);
  }
}

function canReceive(user, options = {}) {
  const role = options.role || "public";
  if (role === "public") return true;
  if (!user) return false;
  if (role === "user") return true;
  if (role === "mod") return Boolean(user.isMod || user.isAdmin);
  if (role === "admin") return Boolean(user.isAdmin);
  return false;
}

module.exports = {
  publishWebEvent: publish,
  subscribeWebEvents: subscribe
};