feat: web client, get/drop updates and fixes

1 files changed, 101 insertions, 0 deletions

diff --git a/internal/net/conn.go b/internal/net/conn.go
new file mode 100644
index 0000000..e46031b
--- /dev/null
+++ b/internal/net/conn.go
@@ -0,0 +1,101 @@
+package net
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"net"
+	"strings"
+)
+
+type Conn interface {
+	ReadMessage() (string, error)
+	io.Writer
+	io.Closer
+	SetEcho(bool) error
+}
+
+type tcpConn struct {
+	conn    net.Conn
+	reader  *bufio.Reader
+	echoOff bool
+}
+
+func newTCPConn(conn net.Conn) *tcpConn {
+	return &tcpConn{
+		conn:   conn,
+		reader: bufio.NewReader(conn),
+	}
+}
+
+func (t *tcpConn) ReadMessage() (string, error) {
+	line, err := t.reader.ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	line = strings.TrimRight(line, "\r\n")
+	line = stripIAC(line)
+	if t.echoOff {
+		t.conn.Write([]byte("\r\n"))
+	}
+	return line, nil
+}
+
+func (t *tcpConn) Write(b []byte) (int, error) {
+	return t.conn.Write(b)
+}
+
+func (t *tcpConn) Close() error {
+	return t.conn.Close()
+}
+
+func (t *tcpConn) SetEcho(on bool) error {
+	t.echoOff = !on
+	if on {
+		return t.writeTelnetCmd(wont, echo)
+	}
+	return t.writeTelnetCmd(will, echo)
+}
+
+const (
+	iac  = 255
+	will = 251
+	wont = 252
+	do   = 253
+	dont = 254
+	sb   = 250
+	se   = 240
+	echo = 1
+)
+
+func (t *tcpConn) writeTelnetCmd(cmd, opt byte) error {
+	_, err := t.conn.Write([]byte{iac, cmd, opt})
+	return err
+}
+
+func stripIAC(s string) string {
+	b := []byte(s)
+	var out []byte
+	i := 0
+	iacSE := []byte{iac, se}
+	for i < len(b) {
+		if b[i] == iac && i+2 < len(b) {
+			if b[i+1] == sb {
+				end := bytes.Index(b[i+2:], iacSE)
+				if end >= 0 {
+					i += end + 4
+					continue
+				}
+			}
+			i += 3
+			continue
+		}
+		if b[i] == iac {
+			i++
+			continue
+		}
+		out = append(out, b[i])
+		i++
+	}
+	return string(out)
+}