ssh-netbox-wrapper/internal/multiplex/tmux.go

package multiplex

import (
	"strconv"
	"strings"
)

// paneScript runs the pane's command and keeps a failed one on screen, so an
// unreachable host shows its error instead of the pane vanishing.
const paneScript = `"$@"; status=$?; if [ "$status" -ne 0 ]; then echo; echo "netssh exited with status $status, press Enter to close"; read -r _; fi`

// tmuxArgv runs the pane through sh with argv as arguments: no quoting, and
// independent of the user's default-shell (which may be fish).
func tmuxArgv(p Pane) []string {
	return append([]string{"sh", "-c", paneScript, "netssh-pane"}, p.Argv...)
}

// openTmux adds a window per chunk of panes: to the current session inside
// tmux, else to a new detached session that is attached at the end.
func openTmux(panes []Pane, opts Options, r Runner) error {
	inside := r.Getenv("TMUX") != ""
	session := ""
	if !inside {
		session = freeSession(r, "netssh-"+opts.Label)
	}
	groups := chunks(panes, opts.PerWindow)
	first := ""
	for i, group := range groups {
		name := windowLabel(opts.Label, i, len(groups))
		format := []string{"-P", "-F", "#{window_id} #{pane_id}", "-n", name}
		var create []string
		switch {
		case inside:
			create = append([]string{"tmux", "new-window"}, format...)
		case i == 0:
			// A large virtual size leaves room for the splits; attaching resizes it.
			create = append([]string{"tmux", "new-session", "-d", "-x", "240", "-y", "70", "-s", session}, format...)
		default:
			create = append([]string{"tmux", "new-window", "-t", session + ":"}, format...)
		}
		out, err := r.Output(append(create, tmuxArgv(group[0])...)...)
		if err != nil {
			return err
		}
		window, pane, _ := strings.Cut(out, " ")
		if first == "" {
			first = window
		}
		paneIDs := []string{pane}
		for _, p := range group[1:] {
			id, err := r.Output(append([]string{"tmux", "split-window", "-t", window, "-P", "-F", "#{pane_id}"}, tmuxArgv(p)...)...)
			if err != nil {
				return err
			}
			paneIDs = append(paneIDs, id)
			// Re-tile after every split so the next one still has room.
			if _, err := r.Output("tmux", "select-layout", "-t", window, "tiled"); err != nil {
				return err
			}
		}
		for j, id := range paneIDs {
			// A pane may already be gone (host unreachable and closed); not fatal.
			_, _ = r.Output("tmux", "set-option", "-p", "-t", id, "@netssh_host", group[j].Title)
		}
		windowOptions := [][]string{
			{"pane-border-status", "top"},
			{"pane-border-format", " #{@netssh_host}#{?pane_synchronized, [SYNC],} "},
		}
		if opts.Sync {
			windowOptions = append(windowOptions, []string{"synchronize-panes", "on"})
		}
		for _, option := range windowOptions {
			if _, err := r.Output("tmux", "set-window-option", "-t", window, option[0], option[1]); err != nil {
				return err
			}
		}
	}
	if inside {
		_, err := r.Output("tmux", "select-window", "-t", first)
		return err
	}
	opts.Hint("toggle broadcast with: netssh sync (or Ctrl+b :setw synchronize-panes)")
	return r.Exec("tmux", "attach-session", "-t", session)
}

// freeSession returns name, or name-2, name-3, … if a session already uses it.
func freeSession(r Runner, name string) string {
	candidate := name
	for n := 2; ; n++ {
		if _, err := r.Output("tmux", "has-session", "-t", "="+candidate); err != nil {
			return candidate
		}
		candidate = name + "-" + strconv.Itoa(n)
	}
}