package udp

import (
	"log/slog"
	"net"
	"runtime/debug"
)

type UdpServer interface {
	Listen()
	Close()
}

type UdpMsgHandler func(b []byte)

type server struct {
	addr    string
	conn    *net.UDPConn
	handler UdpMsgHandler
}

// NewServer creates a new instance of UdpServer.
func NewServer(addr string, handler UdpMsgHandler) UdpServer {
	return &server{addr: addr, handler: handler}
}

func (s *server) Listen() {
	udpAddr, err := net.ResolveUDPAddr("udp", s.addr)
	if err != nil {
		panic(err)
	}
	conn, err := net.ListenUDP("udp", udpAddr)
	if err != nil {
		panic(err)
	}
	s.conn = conn
	// 启动监听处理
	go s.listenAndHandle()
}

func (s *server) Close() {
	err := s.conn.Close()
	if err != nil {
		slog.Error("udp server close error", "error", err)
	}
}

func (s *server) listenAndHandle() {
	defer s.conn.Close()
	for {
		b := make([]byte, 1024)
		n, err := s.conn.Read(b)
		if err != nil {
			slog.Error("udp server read error", err)
			return
		}
		if n > 0 {
			go s.handle(b[0:n])
		}
	}
}

func (s *server) handle(b []byte) {
	defer func() {
		if err := recover(); err != nil {
			slog.Error("udp server handle error", "error", err, "stack", string(debug.Stack()))
			debug.PrintStack()
		}
	}()
	// slog.Info("udp server handle", "msg", string(b))
	s.handler(b)
}