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package hotline
import (
"bufio"
"bytes"
"context"
"encoding/binary"
"fmt"
"io"
"log/slog"
"net"
"time"
)
type ClientPrefs struct {
Username string `yaml:"Username"`
IconID int `yaml:"IconID"`
Tracker string `yaml:"Tracker"`
EnableBell bool `yaml:"EnableBell"`
}
func (cp *ClientPrefs) IconBytes() []byte {
iconBytes := make([]byte, 2)
binary.BigEndian.PutUint16(iconBytes, uint16(cp.IconID))
return iconBytes
}
type Client struct {
Connection net.Conn
Logger *slog.Logger
Pref *ClientPrefs
Handlers map[[2]byte]ClientHandler
activeTasks map[[4]byte]*Transaction
UserList []User
}
type ClientHandler func(context.Context, *Client, *Transaction) ([]Transaction, error)
func (c *Client) HandleFunc(tranType [2]byte, handler ClientHandler) {
c.Handlers[tranType] = handler
}
func NewClient(username string, logger *slog.Logger) *Client {
c := &Client{
Logger: logger,
activeTasks: make(map[[4]byte]*Transaction),
Handlers: make(map[[2]byte]ClientHandler),
Pref: &ClientPrefs{Username: username},
}
return c
}
type ClientTransaction struct {
Name string
Handler func(*Client, *Transaction) ([]Transaction, error)
}
func (ch ClientTransaction) Handle(cc *Client, t *Transaction) ([]Transaction, error) {
return ch.Handler(cc, t)
}
type ClientTHandler interface {
Handle(*Client, *Transaction) ([]Transaction, error)
}
// JoinServer connects to a Hotline server and completes the login flow
func (c *Client) Connect(address, login, passwd string) (err error) {
// Establish TCP connection to server
c.Connection, err = net.DialTimeout("tcp", address, 5*time.Second)
if err != nil {
return err
}
// Send handshake sequence
if err := c.Handshake(); err != nil {
return err
}
// Authenticate (send TranLogin 107)
err = c.Send(
NewTransaction(
TranLogin, [2]byte{0, 0},
NewField(FieldUserName, []byte(c.Pref.Username)),
NewField(FieldUserIconID, c.Pref.IconBytes()),
NewField(FieldUserLogin, EncodeString([]byte(login))),
NewField(FieldUserPassword, EncodeString([]byte(passwd))),
),
)
if err != nil {
return fmt.Errorf("error sending login transaction: %w", err)
}
// start keepalive go routine
go func() { _ = c.keepalive() }()
return nil
}
const keepaliveInterval = 300 * time.Second
func (c *Client) keepalive() error {
for {
time.Sleep(keepaliveInterval)
_ = c.Send(NewTransaction(TranKeepAlive, [2]byte{}))
}
}
var ClientHandshake = []byte{
0x54, 0x52, 0x54, 0x50, // TRTP
0x48, 0x4f, 0x54, 0x4c, // HOTL
0x00, 0x01,
0x00, 0x02,
}
var ServerHandshake = []byte{
0x54, 0x52, 0x54, 0x50, // TRTP
0x00, 0x00, 0x00, 0x00, // ErrorCode
}
func (c *Client) Handshake() error {
// Protocol Type 4 ‘TRTP’ 0x54 52 54 50
// Sub-protocol Type 4 User defined
// Version 2 1 Currently 1
// Sub-version 2 User defined
if _, err := c.Connection.Write(ClientHandshake); err != nil {
return fmt.Errorf("handshake write err: %s", err)
}
replyBuf := make([]byte, 8)
_, err := c.Connection.Read(replyBuf)
if err != nil {
return err
}
if bytes.Equal(replyBuf, ServerHandshake) {
return nil
}
// In the case of an error, client and server close the connection.
return fmt.Errorf("handshake response err: %s", err)
}
func (c *Client) Send(t Transaction) error {
requestNum := binary.BigEndian.Uint16(t.Type[:])
// if transaction is NOT reply, add it to the list to transactions we're expecting a response for
if t.IsReply == 0 {
c.activeTasks[t.ID] = &t
}
n, err := io.Copy(c.Connection, &t)
if err != nil {
return fmt.Errorf("error sending transaction: %w", err)
}
c.Logger.Debug("Sent Transaction",
"IsReply", t.IsReply,
"type", requestNum,
"sentBytes", n,
)
return nil
}
func (c *Client) HandleTransaction(ctx context.Context, t *Transaction) error {
var origT Transaction
if t.IsReply == 1 {
origT = *c.activeTasks[t.ID]
t.Type = origT.Type
}
if handler, ok := c.Handlers[t.Type]; ok {
c.Logger.Debug(
"Received transaction",
"IsReply", t.IsReply,
"type", t.Type[:],
)
outT, err := handler(ctx, c, t)
if err != nil {
c.Logger.Error("error handling transaction", "err", err)
}
for _, t := range outT {
if err := c.Send(t); err != nil {
return err
}
}
}
return nil
}
func (c *Client) Disconnect() error {
return c.Connection.Close()
}
func (c *Client) HandleTransactions(ctx context.Context) error {
// Create a new scanner for parsing incoming bytes into transaction tokens
scanner := bufio.NewScanner(c.Connection)
scanner.Split(transactionScanner)
// Scan for new transactions and handle them as they come in.
for scanner.Scan() {
// Make a new []byte slice and copy the scanner bytes to it. This is critical to avoid a data race as the
// scanner re-uses the buffer for subsequent scans.
buf := make([]byte, len(scanner.Bytes()))
copy(buf, scanner.Bytes())
var t Transaction
_, err := t.Write(buf)
if err != nil {
break
}
if err := c.HandleTransaction(ctx, &t); err != nil {
c.Logger.Error("Error handling transaction", "err", err)
}
}
if scanner.Err() == nil {
return scanner.Err()
}
return nil
}
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