feat: implement local terminal support with shell configuration and UI integration

internal/localshell/localshell.go

@@ -0,0 +1,190 @@
+// Package localshell provides a local PTY-based terminal session.
+// It spawns a shell process and bridges I/O for the frontend terminal.
+package localshell
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"runtime"
+	"sync"
+
+	"github.com/creack/pty"
+)
+
+// Client manages a local shell PTY session.
+type Client struct {
+	mu       sync.Mutex
+	cmd      *exec.Cmd
+	ptmx     *os.File
+	shell    string
+	onData   func([]byte)
+	onError  func(error)
+	onClose  func()
+	closed   bool
+	cols     uint16
+	rows     uint16
+}
+
+// Config holds configuration for a local shell session.
+type Config struct {
+	Shell   string // Path to the shell binary (e.g. /bin/zsh)
+	Cols    uint16
+	Rows    uint16
+	OnData  func([]byte)
+	OnError func(error)
+	OnClose func()
+}
+
+// DefaultShell returns the system default shell.
+func DefaultShell() string {
+	if runtime.GOOS == "windows" {
+		// Prefer PowerShell if available, else cmd.exe.
+		if ps, err := exec.LookPath("powershell.exe"); err == nil {
+			return ps
+		}
+		return "cmd.exe"
+	}
+	// Unix: use SHELL env var, fallback to /bin/sh.
+	if sh := os.Getenv("SHELL"); sh != "" {
+		return sh
+	}
+	return "/bin/sh"
+}
+
+// NewClient creates a new local shell client.
+func NewClient(cfg Config) *Client {
+	shell := cfg.Shell
+	if shell == "" {
+		shell = DefaultShell()
+	}
+	cols := cfg.Cols
+	if cols == 0 {
+		cols = 80
+	}
+	rows := cfg.Rows
+	if rows == 0 {
+		rows = 24
+	}
+	return &Client{
+		shell:  shell,
+		cols:   cols,
+		rows:   rows,
+		onData: cfg.OnData,
+		onError: cfg.OnError,
+		onClose: cfg.OnClose,
+	}
+}
+
+// Start spawns the shell process and begins reading output.
+func (c *Client) Start() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.ptmx != nil {
+		return fmt.Errorf("shell already running")
+	}
+
+	cmd := exec.Command(c.shell)
+	cmd.Env = os.Environ()
+
+	// Start in the user's home directory.
+	if home, err := os.UserHomeDir(); err == nil {
+		cmd.Dir = home
+	}
+
+	// Set TERM for proper terminal behaviour.
+	cmd.Env = append(cmd.Env, "TERM=xterm-256color")
+
+	ptmx, err := pty.StartWithSize(cmd, &pty.Winsize{
+		Cols: c.cols,
+		Rows: c.rows,
+	})
+	if err != nil {
+		return fmt.Errorf("failed to start shell %q: %w", c.shell, err)
+	}
+
+	c.cmd = cmd
+	c.ptmx = ptmx
+
+	// Read loop — forward PTY output to the frontend.
+	go c.readLoop()
+
+	// Wait for process exit.
+	go func() {
+		_ = cmd.Wait()
+		c.mu.Lock()
+		wasClosed := c.closed
+		c.closed = true
+		c.mu.Unlock()
+
+		if !wasClosed && c.onClose != nil {
+			c.onClose()
+		}
+	}()
+
+	return nil
+}
+
+// Write sends data to the shell's stdin (PTY).
+func (c *Client) Write(data []byte) error {
+	c.mu.Lock()
+	ptmx := c.ptmx
+	c.mu.Unlock()
+
+	if ptmx == nil {
+		return fmt.Errorf("shell not running")
+	}
+	_, err := ptmx.Write(data)
+	return err
+}
+
+// Resize updates the PTY window size.
+func (c *Client) Resize(cols, rows uint16) error {
+	c.mu.Lock()
+	ptmx := c.ptmx
+	c.mu.Unlock()
+
+	if ptmx == nil {
+		return nil
+	}
+	return pty.Setsize(ptmx, &pty.Winsize{Cols: cols, Rows: rows})
+}
+
+// Close terminates the shell process and PTY.
+func (c *Client) Close() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.closed {
+		return
+	}
+	c.closed = true
+
+	if c.ptmx != nil {
+		c.ptmx.Close()
+		c.ptmx = nil
+	}
+	if c.cmd != nil && c.cmd.Process != nil {
+		c.cmd.Process.Kill()
+	}
+}
+
+func (c *Client) readLoop() {
+	buf := make([]byte, 32*1024)
+	for {
+		n, err := c.ptmx.Read(buf)
+		if n > 0 && c.onData != nil {
+			c.onData(buf[:n])
+		}
+		if err != nil {
+			c.mu.Lock()
+			wasClosed := c.closed
+			c.mu.Unlock()
+			if !wasClosed && c.onError != nil {
+				c.onError(err)
+			}
+			return
+		}
+	}
+}