package com.sw.platecabinet.socket;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/**
 * Simple UDP discovery client:
 * Sends "DISCOVER_SERVER" broadcast and waits for first reply "SERVER_FOUND:serverName:ip"
 */
public class UdpDiscoveryClient {

    public interface Listener {
        void onFound(String ip, String serverName);

        void onError(Exception e);
    }

    public void discover(int discoveryPort, int timeoutMs, Listener listener) {
        new Thread(() -> {
            try (DatagramSocket socket = new DatagramSocket()) {
                socket.setBroadcast(true);
                byte[] data = "DISCOVER_SERVER".getBytes();
                DatagramPacket packet = new DatagramPacket(data, data.length, InetAddress.getByName("255.255.255.255"), discoveryPort);
                socket.send(packet);

                socket.setSoTimeout(timeoutMs);
                byte[] buf = new byte[512];
                DatagramPacket resp = new DatagramPacket(buf, buf.length);
                socket.receive(resp);

                String msg = new String(resp.getData(), 0, resp.getLength());
                if (msg.startsWith("SERVER_FOUND")) {
                    // format: SERVER_FOUND:serverName:ip
                    String[] parts = msg.split(":", 3);
                    if (parts.length >= 3) {
                        listener.onFound(parts[2], parts[1]);
                        return;
                    }
                }
                listener.onError(new Exception("Invalid response"));
            } catch (Exception e) {
                listener.onError(e);
            }
        }).start();
    }
}