gamestatus/java/query.go

package java

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"net"
	"strconv"
	"strings"
	"time"

	"github.com/VexoraDevelopment/gamestatus/info"
)

func (c *Client) QueryFull(address string, port int) (*info.ServerInfo, error) {
	if port == 0 {
		port = 25565
	}

	host := address
	p := port
	if c.opt.EnableSRV && net.ParseIP(host) == nil {
		if rh, rp, err := c.resolveSRV(host); err == nil && rh != "" {
			host = rh
			if rp != 0 {
				p = rp
			}
		}
	}

	conn, _, err := c.dialUDP(host, p)
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	start := time.Now()

	chalPayload, err := c.writeQueryPacket(conn, 0x09, nil)
	if err != nil {
		return nil, err
	}
	chalStr := strings.TrimRight(string(chalPayload), "\x00\r\n\t ")
	chalInt, err := strconv.Atoi(chalStr)
	if err != nil {
		return nil, fmt.Errorf("java query challenge parse failed: %w (payload=%q)", err, chalStr)
	}

	chal := make([]byte, 4)
	binary.BigEndian.PutUint32(chal, uint32(chalInt))

	appendData := make([]byte, 0, 8)
	appendData = append(appendData, chal...)
	appendData = append(appendData, 0x00, 0x00, 0x00, 0x00)

	data, err := c.writeQueryPacket(conn, 0x00, appendData)
	if err != nil {
		return nil, err
	}

	if len(data) < 11 {
		return nil, errors.New("java query full stat response too short")
	}
	payload := data[11:]

	marker := []byte{0x00, 0x00, 0x01, 'p', 'l', 'a', 'y', 'e', 'r', '_', 0x00, 0x00}
	parts := bytes.SplitN(payload, marker, 2)
	if len(parts) != 2 {
		return nil, errors.New("java query parse failed: marker not found")
	}
	kvPart := parts[0]
	playersPart := parts[1]
	if len(playersPart) >= 2 {
		playersPart = playersPart[:len(playersPart)-2]
	}

	raw := map[string]string{}
	kvs := bytes.Split(kvPart, []byte{0x00})
	for i := 0; i+1 < len(kvs); i += 2 {
		k := string(kvs[i])
		v := string(kvs[i+1])
		if k == "" {
			continue
		}
		raw[k] = v
	}

	var players []string
	if len(playersPart) > 0 {
		pp := bytes.Split(playersPart, []byte{0x00})
		for _, b := range pp {
			s := string(b)
			if s != "" {
				players = append(players, s)
			}
		}
	}

	srvInfo := &info.ServerInfo{
		Edition:  info.EditionJava,
		Address:  address,
		IP:       resolveIP(address),
		Port:     intFromMap(raw, "hostport", port),
		MOTD:     raw["hostname"],
		Version:  raw["version"],
		GameMode: raw["gametype"],
		Map:      raw["map"],
		Game:     raw["game_id"],
		Online:   intFromMap(raw, "numplayers", 0),
		Slots:    intFromMap(raw, "maxplayers", 0),
		Players:  players,
		Query:    true,
		RawQuery: raw,
		Latency:  time.Since(start),
	}

	if pl := raw["plugins"]; pl != "" {
		split := strings.SplitN(pl, ": ", 2)
		srvInfo.Software = split[0]
		if len(split) == 2 {
			p2 := strings.Split(split[1], "; ")
			clean := make([]string, 0, len(p2))
			for _, x := range p2 {
				x = strings.TrimSpace(x)
				if x != "" {
					clean = append(clean, x)
				}
			}
			if len(clean) > 0 {
				srvInfo.Plugins = clean
			}
		}
	} else if eng := raw["server_engine"]; eng != "" {
		srvInfo.Software = eng
	}

	return srvInfo, nil
}

func (c *Client) dialUDP(host string, port int) (*net.UDPConn, *net.UDPAddr, error) {
	raddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", host, port))
	if err != nil {
		return nil, nil, err
	}
	conn, err := net.DialUDP("udp", nil, raddr)
	if err != nil {
		return nil, nil, err
	}
	if err := conn.SetDeadline(time.Now().Add(c.opt.Timeout)); err != nil {
		_ = conn.Close()
		return nil, nil, err
	}
	return conn, raddr, nil
}

func (c *Client) writeQueryPacket(conn *net.UDPConn, typ byte, appendData []byte) ([]byte, error) {
	header := []byte{0xFE, 0xFD, typ, 0x01, 0x02, 0x03, 0x04}
	packet := make([]byte, 0, len(header)+len(appendData))
	packet = append(packet, header...)
	packet = append(packet, appendData...)

	if err := conn.SetDeadline(time.Now().Add(c.opt.Timeout)); err != nil {
		return nil, err
	}
	if _, err := conn.Write(packet); err != nil {
		return nil, err
	}

	buf := make([]byte, 4096)
	n, err := conn.Read(buf)
	if err != nil {
		return nil, err
	}
	resp := buf[:n]
	if len(resp) < 5 || resp[0] != typ {
		return nil, errors.New("java query response validation failed")
	}
	return resp[5:], nil
}

func intFromMap(m map[string]string, key string, def int) int {
	v := strings.TrimSpace(m[key])
	if v == "" {
		return def
	}
	n, err := strconv.Atoi(v)
	if err != nil {
		return def
	}
	return n
}