refactor: extract internal/session and eliminate I/O globals

Move serial port, trzsz filter, and pipe lifecycle into
internal/session.SerialSession. Replace 8 global I/O vars
(serialPort, trzszFilter, stdinPipe, stdoutPipe, clientIn,
clientOut, termch, termchOnce) with single sess variable.
Delete utils.go.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app.go

@@ -156,8 +156,8 @@ func (a *App) Close() {
 		close(a.done)
 		a.forward.Close()
 		a.plugins.Close()
-		CloseTrzsz()
+		sess.Close()
-		CloseSerial()
+		
 		if a.logFile != nil {
 			_ = a.logFile.Close()
 		}
@@ -216,7 +216,7 @@ func (a *App) writeRawToSession(data []byte) error {
 
 	a.stdinMu.Lock()
 	defer a.stdinMu.Unlock()
-	_, err := stdinPipe.Write(data)
+	_, err := sess.StdinPipe.Write(data)
 	return err
 }
 
@@ -246,7 +246,7 @@ func (a *App) sendCtrl(letter byte) error {
 		letter = letter + ('a' - 'A')
 	}
 	control := []byte{letter & 0x1f}
-	_, err := serialPort.Write(control)
+	_, err := sess.Port.Write(control)
 	return err
 }
 
@@ -300,7 +300,7 @@ func (a *App) readHexOutput() {
 
 	buf := make([]byte, frameSize)
 	for {
-		n, err := stdoutPipe.Read(buf)
+		n, err := sess.StdoutPipe.Read(buf)
 		if n > 0 {
 			chunk := make([]byte, n)
 			copy(chunk, buf[:n])
@@ -333,7 +333,7 @@ func (a *App) readHexOutput() {
 func (a *App) readTextOutput() {
 	buf := make([]byte, 4096)
 	for {
-		n, err := stdoutPipe.Read(buf)
+		n, err := sess.StdoutPipe.Read(buf)
 		if n > 0 {
 			chunk := make([]byte, n)
 			copy(chunk, buf[:n])

app_test.go

@@ -9,6 +9,7 @@ import (
 	"go.bug.st/serial"
 
 	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/event"
+	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/session"
 	"github.com/jixishi/SerialTerminalForWindowsTerminal/pkg/forward"
 	"github.com/jixishi/SerialTerminalForWindowsTerminal/pkg/luaplugin"
 )
@@ -204,11 +205,14 @@ func TestReportForwardIngress(t *testing.T) {
 }
 
 func TestSendCtrl(t *testing.T) {
-	oldSp := serialPort
+	if sess == nil {
-	defer func() { serialPort = oldSp }()
+		sess = &session.SerialSession{}
+	}
+	oldSp := sess.Port
+	defer func() { sess.Port = oldSp }()
 
 	// Use a mock serial port
-	serialPort = &mockSerialPort{}
+	sess.Port = &mockSerialPort{}
 	a := &App{
 		cfg:      &Config{},
 		uiEvents: make(chan event.UIEvent, 4),

command_test.go

@@ -6,13 +6,17 @@ import (
 	"testing"
 
 	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/event"
+	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/session"
 	"github.com/jixishi/SerialTerminalForWindowsTerminal/pkg/forward"
 	"github.com/jixishi/SerialTerminalForWindowsTerminal/pkg/luaplugin"
 )
 
 func setupTestPipes() {
+	if sess == nil {
+		sess = &session.SerialSession{}
+	}
 	var cr *io.PipeReader
-	cr, stdinPipe = io.Pipe()
+	cr, sess.StdinPipe = io.Pipe()
 	go func() {
 		buf := make([]byte, 4096)
 		for {

internal/session/session.go

@@ -0,0 +1,138 @@
+// Package session manages the serial port connection and its associated pipes.
+package session
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"os/signal"
+	"runtime"
+	"sync"
+
+	"github.com/trzsz/trzsz-go/trzsz"
+	"go.bug.st/serial"
+	"golang.org/x/term"
+
+	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/config"
+)
+
+// SerialSession owns the serial port, trzsz filter, and pipe pair.
+type SerialSession struct {
+	Port        serial.Port
+	TrzszFilter *trzsz.TrzszFilter
+	StdinPipe   *io.PipeWriter
+	StdoutPipe  *io.PipeReader
+	ClientIn    *io.PipeReader
+	ClientOut   *io.PipeWriter
+
+	termCh    chan os.Signal
+	closeOnce sync.Once
+}
+
+// Open creates a SerialSession by opening the serial port and initializing trzsz.
+func Open(cfg *config.Config) (*SerialSession, error) {
+	mode := &serial.Mode{
+		BaudRate: cfg.BaudRate,
+		StopBits: serial.StopBits(cfg.StopBits),
+		DataBits: cfg.DataBits,
+		Parity:   serial.Parity(cfg.ParityBit),
+	}
+	port, err := serial.Open(cfg.PortName, mode)
+	if err != nil {
+		return nil, err
+	}
+
+	fd := int(os.Stdin.Fd())
+	width, _, err := term.GetSize(fd)
+	if err != nil {
+		if runtime.GOOS != "windows" {
+			port.Close()
+			return nil, fmt.Errorf("term get size failed: %w", err)
+		}
+		width = 80
+	}
+
+	clientIn, stdinPipe := io.Pipe()
+	stdoutPipe, clientOut := io.Pipe()
+	trzszFilter := trzsz.NewTrzszFilter(clientIn, clientOut, port, port,
+		trzsz.TrzszOptions{TerminalColumns: int32(width), EnableZmodem: true})
+	trzsz.SetAffectedByWindows(false)
+
+	s := &SerialSession{
+		Port:        port,
+		TrzszFilter: trzszFilter,
+		StdinPipe:   stdinPipe,
+		StdoutPipe:  stdoutPipe,
+		ClientIn:    clientIn,
+		ClientOut:   clientOut,
+		termCh:      make(chan os.Signal, 1),
+	}
+
+	go func() {
+		for range s.termCh {
+			w, _, err := term.GetSize(fd)
+			if err != nil {
+				fmt.Printf("term get size failed: %s\n", err)
+				continue
+			}
+			trzszFilter.SetTerminalColumns(int32(w))
+		}
+	}()
+
+	return s, nil
+}
+
+// Write writes data to the stdin pipe (toward serial port, through trzsz).
+func (s *SerialSession) Write(data []byte) (int, error) {
+	return s.StdinPipe.Write(data)
+}
+
+// Read reads data from the stdout pipe (from serial port, through trzsz).
+func (s *SerialSession) Read(buf []byte) (int, error) {
+	return s.StdoutPipe.Read(buf)
+}
+
+// SendCtrl sends a control character directly to the serial port (bypasses trzsz).
+func (s *SerialSession) SendCtrl(letter byte) (int, error) {
+	if letter >= 'A' && letter <= 'Z' {
+		letter = letter + ('a' - 'A')
+	}
+	control := []byte{letter & 0x1f}
+	return s.Port.Write(control)
+}
+
+// Close tears down the session: stops term signals, closes trzsz, then serial port.
+func (s *SerialSession) Close() {
+	s.closeOnce.Do(func() {
+		if s.termCh != nil {
+			signal.Stop(s.termCh)
+			close(s.termCh)
+		}
+		if s.Port != nil {
+			if err := s.Port.Close(); err != nil {
+				fmt.Fprint(os.Stderr, err)
+				fmt.Fprint(os.Stderr, "\n")
+			}
+		}
+	})
+}
+
+// CheckPortAvailability returns the list of available ports and verifies the named port exists.
+func CheckPortAvailability(name string) ([]string, error) {
+	ports, err := serial.GetPortsList()
+	if err != nil {
+		return nil, err
+	}
+	if len(ports) == 0 {
+		return nil, fmt.Errorf("no serial ports found")
+	}
+	if name == "" {
+		return ports, fmt.Errorf("port name not specified")
+	}
+	for _, port := range ports {
+		if port == name {
+			return ports, nil
+		}
+	}
+	return ports, fmt.Errorf("port " + name + " is not available")
+}

main.go

@@ -11,6 +11,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/session"
 	"golang.org/x/term"
 )
 
@@ -35,20 +36,16 @@ func main() {
 	if cfg.PortName == "" {
 		getCliFlag()
 	}
-	ports, err := checkPortAvailability(cfg.PortName)
+	ports, err := session.CheckPortAvailability(cfg.PortName)
 	if err != nil {
 		fmt.Println(err)
 		printUsage(ports)
 		os.Exit(0)
 	}
 
-	if err = OpenSerial(); err != nil {
+	sess, err = session.Open(cfg)
-		fmt.Fprintf(os.Stderr, "open serial failed: %v\n", err)
+	if err != nil {
-		os.Exit(1)
+		fmt.Fprintf(os.Stderr, "open session failed: %v\n", err)
-	}
-
-	if err = OpenTrzsz(); err != nil {
-		fmt.Fprintf(os.Stderr, "open trzsz failed: %v\n", err)
 		os.Exit(1)
 	}
 

mutual.go

@@ -1,18 +1,13 @@
 package main
 
 import (
-	"github.com/trzsz/trzsz-go/trzsz"
-	"go.bug.st/serial"
 	"io"
 	"os"
+
+	"github.com/jixishi/SerialTerminalForWindowsTerminal/internal/session"
 )
 
 var (
-	serialPort  serial.Port
+	sess *session.SerialSession
-	out         io.Writer = os.Stdout
+	out  io.Writer = os.Stdout
-	trzszFilter *trzsz.TrzszFilter
-	clientIn    *io.PipeReader
-	stdoutPipe  *io.PipeReader
-	stdinPipe   *io.PipeWriter
-	clientOut   *io.PipeWriter
 )

utils.go

@@ -1,110 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"github.com/trzsz/trzsz-go/trzsz"
-	"go.bug.st/serial"
-	"golang.org/x/term"
-	"io"
-	"os"
-	"os/signal"
-	"runtime"
-	"strings"
-	"sync"
-)
-
-func checkPortAvailability(name string) ([]string, error) {
-	ports, err := serial.GetPortsList()
-	if err != nil {
-		return nil, err
-	}
-	if len(ports) == 0 {
-		return nil, fmt.Errorf("无串口")
-	}
-	if name == "" {
-		return ports, fmt.Errorf("串口未指定")
-	}
-	for _, port := range ports {
-		if strings.Compare(port, name) == 0 {
-			return ports, nil
-		}
-	}
-	return ports, fmt.Errorf("串口 " + name + " 未在线")
-}
-
-func OpenSerial() error {
-	mode := &serial.Mode{
-		BaudRate: cfg.BaudRate,
-		StopBits: serial.StopBits(cfg.StopBits),
-		DataBits: cfg.DataBits,
-		Parity:   serial.Parity(cfg.ParityBit),
-	}
-	var err error
-	serialPort, err = serial.Open(cfg.PortName, mode)
-	return err
-}
-
-func CloseSerial() {
-	if serialPort == nil {
-		return
-	}
-
-	if err := serialPort.Close(); err != nil {
-		fmt.Fprint(os.Stderr, err)
-		fmt.Fprint(os.Stderr, "\n")
-	}
-}
-
-var termch chan os.Signal
-var termchOnce sync.Once
-
-// OpenTrzsz create a TrzszFilter to support trzsz ( trz / tsz ).
-//
-// ┌────────┐   stdinPipe  ┌────────┐   ClientIn   ┌─────────────┐   SerialIn   ┌────────┐
-// │        ├─────────────►│        ├─────────────►│             ├─────────────►│        │
-// │ mutual │              │ Client │              │ TrzszFilter │              │ Serial │
-// │        │◄─────────────│        │◄─────────────┤             │◄─────────────┤        │
-// └────────┘   stdoutPipe └────────┘   ClientOut  └─────────────┘   SerialOut  └────────┘
-func OpenTrzsz() error {
-	fd := int(os.Stdin.Fd())
-	width, _, err := term.GetSize(fd)
-	if err != nil {
-		if runtime.GOOS != "windows" {
-			return fmt.Errorf("term get size failed: %w", err)
-		}
-		width = 80
-	}
-
-	clientIn, stdinPipe = io.Pipe()
-	stdoutPipe, clientOut = io.Pipe()
-	trzszFilter = trzsz.NewTrzszFilter(clientIn, clientOut, serialPort, serialPort,
-		trzsz.TrzszOptions{TerminalColumns: int32(width), EnableZmodem: true})
-	trzsz.SetAffectedByWindows(false)
-	termch = make(chan os.Signal, 1)
-	termchOnce = sync.Once{}
-
-	go func() {
-		for range termch {
-			width, _, err := term.GetSize(fd)
-			if err != nil {
-				fmt.Printf("term get size failed: %s\n", err)
-				continue
-			}
-			trzszFilter.SetTerminalColumns(int32(width))
-		}
-	}()
-
-	return nil
-}
-
-func CloseTrzsz() {
-	if termch == nil {
-		return
-	}
-
-	termchOnce.Do(func() {
-		signal.Stop(termch)
-		close(termch)
-	})
-}
-