feat(muxterm): PTY pool with attach, resize, cleanup

muxterm/pool.go

@@ -0,0 +1,129 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"sync"
+	"syscall"
+
+	"github.com/creack/pty"
+)
+
+// Session represents a PTY-backed tmux attach process.
+type Session struct {
+	PTY  *os.File
+	Cmd  *exec.Cmd
+	Cols uint16
+	Rows uint16
+}
+
+// Pool manages named tmux PTY sessions.
+type Pool struct {
+	mu       sync.Mutex
+	sessions map[string]*Session
+}
+
+// NewPool returns an empty Pool.
+func NewPool() *Pool {
+	return &Pool{
+		sessions: make(map[string]*Session),
+	}
+}
+
+// Attach reuses an existing live session or spawns a new tmux attach process.
+// Dead sessions are cleaned up before spawning a replacement.
+func (p *Pool) Attach(name string, cols, rows uint16) (*Session, error) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if sess, ok := p.sessions[name]; ok {
+		// Check if process is still alive via Signal(0).
+		if sess.Cmd.Process != nil && sess.Cmd.Process.Signal(syscall.Signal(0)) == nil {
+			return sess, nil
+		}
+		// Dead session — clean up.
+		sess.PTY.Close()
+		delete(p.sessions, name)
+	}
+
+	cmd := exec.Command("tmux", "attach", "-t", name)
+	winSize := &pty.Winsize{Cols: cols, Rows: rows}
+
+	ptmx, err := pty.StartWithSize(cmd, winSize)
+	if err != nil {
+		return nil, fmt.Errorf("pty start: %w", err)
+	}
+
+	sess := &Session{
+		PTY:  ptmx,
+		Cmd:  cmd,
+		Cols: cols,
+		Rows: rows,
+	}
+	p.sessions[name] = sess
+
+	// Background goroutine: wait for process exit and clean up.
+	go func() {
+		cmd.Wait()
+		p.mu.Lock()
+		defer p.mu.Unlock()
+		// Only delete if the map still holds this exact session
+		// (Attach may have replaced it already).
+		if cur, ok := p.sessions[name]; ok && cur == sess {
+			sess.PTY.Close()
+			delete(p.sessions, name)
+		}
+	}()
+
+	return sess, nil
+}
+
+// Resize changes the PTY window size for a named session.
+func (p *Pool) Resize(name string, cols, rows uint16) error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	sess, ok := p.sessions[name]
+	if !ok {
+		return fmt.Errorf("session %q not found", name)
+	}
+
+	if err := pty.Setsize(sess.PTY, &pty.Winsize{Cols: cols, Rows: rows}); err != nil {
+		return fmt.Errorf("setsize: %w", err)
+	}
+	sess.Cols = cols
+	sess.Rows = rows
+	return nil
+}
+
+// Get returns the session for name, or nil if not present.
+func (p *Pool) Get(name string) *Session {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.sessions[name]
+}
+
+// IsAlive returns true if the named session exists and its process is alive.
+func (p *Pool) IsAlive(name string) bool {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	sess, ok := p.sessions[name]
+	if !ok {
+		return false
+	}
+	return sess.Cmd.Process != nil && sess.Cmd.Process.Signal(syscall.Signal(0)) == nil
+}
+
+// CloseAll sends SIGTERM to all sessions and closes their PTYs.
+func (p *Pool) CloseAll() {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	for name, sess := range p.sessions {
+		if sess.Cmd.Process != nil {
+			sess.Cmd.Process.Signal(syscall.SIGTERM)
+		}
+		sess.PTY.Close()
+		delete(p.sessions, name)
+	}
+}