feat: add initial code

internal/quake3/client/client.go

@@ -0,0 +1,186 @@
+package client
+
+import (
+	"bytes"
+	"fmt"
+	"net"
+	"strconv"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+const (
+	outOfBandPrefix = "\xff\xff\xff\xff"
+	bufSize         = 1024 * 1024
+	timeout         = 5 * time.Second
+)
+
+type Q3Client struct {
+	address *net.UDPAddr
+	conn    *net.UDPConn
+}
+
+type Status struct {
+	Cfg     map[string]string
+	Players []Player
+}
+
+type Player struct {
+	Name  string
+	Ping  int
+	Score int
+}
+
+func New(host string, port int) (*Q3Client, error) {
+	// Resolve host in case it's a hostname not an IP
+	addr, err := net.ResolveUDPAddr(
+		"udp4",
+		fmt.Sprintf("%s:%d", host, port),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	// Open UDP socket to server
+	conn, err := net.DialUDP("udp4", nil, addr)
+	if err != nil {
+		return nil, err
+	}
+
+	// Build client object
+	return &Q3Client{
+		address: addr,
+		conn:    conn,
+	}, nil
+}
+
+func (c *Q3Client) Close() error {
+	if err := c.conn.Close(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Q3Client) Ping() error {
+	_, err := c.sendCommand("getinfo")
+	return err
+}
+
+func (c *Q3Client) GetInfo() (map[string]string, error) {
+	resp, err := c.sendCommand("getinfo")
+	if err != nil {
+		return nil, err
+	}
+
+	return parseAsMap(resp), nil
+}
+
+func (c *Q3Client) GetStatus() (*Status, error) {
+	data, err := c.sendCommand("getstatus")
+	if err != nil {
+		return nil, err
+	}
+
+	// Try to split into three parts by newlines:
+	// header \n status-string \n players
+	data = bytes.TrimSuffix(data, []byte("\n"))
+	parts := bytes.SplitN(data, []byte("\n"), 3)
+
+	switch len(parts) {
+	case 2: // only header and status-string -> no players
+		return &Status{
+			Cfg:     parseAsMap(parts[1]),
+			Players: make([]Player, 0),
+		}, nil
+	case 3: // header + status-string + players
+		players, err := parsePlayers(parts[2])
+		if err != nil {
+			return nil, err
+		}
+		return &Status{
+			Cfg:     parseAsMap(parts[1]),
+			Players: players,
+		}, nil
+	default:
+		return nil, errors.Errorf(
+			"cannot parse response: %q", data,
+		)
+	}
+}
+
+func (c *Q3Client) sendCommand(command string) ([]byte, error) {
+	// Reset socket timeout
+	if err := c.conn.SetDeadline(time.Now().Add(timeout)); err != nil {
+		return nil, err
+	}
+
+	// Send our message
+	if _, err := c.conn.Write(
+		fmt.Appendf(nil, "%s%s", outOfBandPrefix, command),
+	); err != nil {
+		return nil, err
+	}
+
+	// Read the reply
+	buf := make([]byte, bufSize)
+	n, _, err := c.conn.ReadFrom(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf[:n], nil
+}
+
+func parseAsMap(data []byte) map[string]string {
+	// Strip header if any
+	if i := bytes.Index(data, []byte("\n")); i >= 0 {
+		data = data[i+1:]
+	}
+
+	// Trim ends
+	data = bytes.TrimPrefix(data, []byte("\\"))
+	data = bytes.TrimSuffix(data, []byte("\n"))
+
+	// Split up by backslashes and mapify
+	parts := bytes.Split(data, []byte("\\"))
+	m := make(map[string]string)
+	for i := 0; i < len(parts)-1; i += 2 {
+		m[string(parts[i])] = string(parts[i+1])
+	}
+
+	return m
+}
+
+func parsePlayers(data []byte) ([]Player, error) {
+	players := make([]Player, 0)
+	for p := range bytes.SplitSeq(data, []byte("\n")) {
+		parts := bytes.SplitN(p, []byte(" "), 3)
+		if len(parts) != 3 {
+			continue
+		}
+
+		score, err := strconv.Atoi(string(parts[0]))
+		if err != nil {
+			return nil, err
+		}
+
+		ping, err := strconv.Atoi(string(parts[1]))
+		if err != nil {
+			return nil, err
+		}
+
+		name, err := strconv.Unquote(string(parts[2]))
+		if err != nil {
+			return nil, err
+		}
+
+		players = append(
+			players,
+			Player{Name: name, Score: score, Ping: ping},
+		)
+	}
+
+	return players, nil
+}