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client.go
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client.go
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package tcp
import (
"bufio"
"errors"
"fmt"
"io"
"log/slog"
"net"
"time"
"github.com/zusi/zusi-go/tcp/message"
)
type Client struct {
conn net.Conn
zusiVersion string
messageChan chan message.Message
errorChan chan error
abort chan struct{}
messageHandler func(*message.Message) (keepMessage bool, err error)
}
func New() *Client {
client := &Client{}
client.abort = make(chan struct{})
return client
}
func NewWithHandler(messageHandler func(*message.Message) (keepMessage bool, err error)) *Client {
client := New()
client.messageHandler = messageHandler
return client
}
func (c *Client) Receive() (*message.Message, error) {
select {
case msg, ok := <-c.messageChan:
if !ok {
return nil, io.EOF
}
return &msg, nil
case err := <-c.errorChan:
return nil, err
}
}
func (c *Client) ConnectWithType(address string, typ message.ClientTyp) error {
if c.conn != nil {
return errors.New("already connected to a server. first close old connection")
}
conn, err := net.DialTimeout("tcp", address, 10*time.Second)
if err != nil {
return fmt.Errorf("error connecting to zusi host: %w", err)
}
c.conn = conn
bufReader := bufio.NewReader(c.conn)
err = c.handshake(bufReader, typ)
if err != nil {
return fmt.Errorf("error during handshake: %w", err)
}
c.messageChan = make(chan message.Message)
c.errorChan = make(chan error)
go c.read(bufReader)
return err
}
func (c *Client) handshake(reader io.Reader, typ message.ClientTyp) error {
handshakeMsg := message.Message{
Verbindungsaufbau: &message.VerbindungsaufbauMessage{
Hello: &message.HelloMessage{
ProtokollVersion: Uint16(2),
ClientTyp: Uint16(uint16(typ)),
Name: String("Client TCP-Test"),
Version: String("1.0-alpha"),
},
},
}
err := c.Send(handshakeMsg)
if err != nil {
return err
}
msg, err := Read(reader)
if err != nil {
slog.With("err", err).Error("Error unmarshalling initial message")
return fmt.Errorf("unmarshaling initial message failed: %w", err)
}
if msg.Verbindungsaufbau == nil || msg.Verbindungsaufbau.AckHello == nil {
slog.With("message", msg).Error("Initial message is not of type Verbindungsaufbau.AckHello")
return errors.New("Initial message is not of type Verbindungsaufbau.AckHello")
}
if *msg.Verbindungsaufbau.AckHello.ErrorCode != 0 {
slog.With("message", msg, "errorCode", msg.Verbindungsaufbau.AckHello.ErrorCode).Error("ErrorCode of initial message != 0")
return errors.New("ErrorCode of initial message != 0")
}
c.zusiVersion = *msg.Verbindungsaufbau.AckHello.ZusiVersion
return nil
}
func (c *Client) read(reader io.Reader) {
for {
msg, err := Read(reader)
if err != nil {
if errors.Is(err, io.EOF) {
c.errorChan <- fmt.Errorf("remote connection died: %w", err)
close(c.messageChan)
return
}
c.errorChan <- fmt.Errorf("error unmarshalling message. one message is lost but keep receiving: %w", err)
continue
}
if c.messageHandler != nil {
keep, err := c.messageHandler(msg)
if err != nil {
c.errorChan <- fmt.Errorf("error handling message internally but keep receiving: %w", err)
}
if !keep {
continue
}
}
c.messageChan <- *msg
}
}
func (c *Client) Send(message message.Message) error {
bts, err := MarshalMessage(message)
if err != nil {
slog.With("err", err, "message", message).Warn("Error marshalling message")
return err
}
_, err = c.conn.Write(bts)
if err != nil {
slog.With("err", err, "message", message).Warn("Error writing message to stream")
return err
}
return nil
}
func (c *Client) Close() error {
err := c.conn.Close()
c.conn = nil
if c.abort != nil {
c.abort <- struct{}{}
}
return err
}