go-ssh-server/main.go

package main

import (
	"context"
	"crypto/ed25519"
	"crypto/rand"
	"encoding/pem"
	"errors"
	"log/slog"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"

	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
	"github.com/charmbracelet/log"
	"github.com/charmbracelet/ssh"
	"github.com/charmbracelet/wish"
	"github.com/charmbracelet/wish/activeterm"
	"github.com/charmbracelet/wish/bubbletea"
	"github.com/charmbracelet/wish/logging"
	"github.com/charmbracelet/wish/recover"
	gossh "golang.org/x/crypto/ssh"
)

type Theme struct {
	Bg     lipgloss.Color
	Fg     lipgloss.Color
	Red    lipgloss.Color
	Green  lipgloss.Color
	Yellow lipgloss.Color
	Blue   lipgloss.Color
	Purple lipgloss.Color
	Aqua   lipgloss.Color
	Orange lipgloss.Color
	Gray   lipgloss.Color
}

func gruvboxDark() Theme {
	return Theme{
		Bg:     lipgloss.Color("#282828"),
		Fg:     lipgloss.Color("#ebdbb2"),
		Red:    lipgloss.Color("#cc241d"),
		Green:  lipgloss.Color("#98971a"),
		Yellow: lipgloss.Color("#d79921"),
		Blue:   lipgloss.Color("#458588"),
		Purple: lipgloss.Color("#b16286"),
		Aqua:   lipgloss.Color("#689d6a"),
		Orange: lipgloss.Color("#d65d0e"),
		Gray:   lipgloss.Color("#928374"),
	}
}

type model struct {
	showWelcome bool
	focus       int
	showHelp    bool
	theme       Theme
	blink       bool
	blinkCount  int
}

const numBoxes = 4

func (m model) Init() tea.Cmd {
	return tea.Tick(time.Millisecond*70, func(t time.Time) tea.Msg {
		return tickMsg(t)
	})
}

type tickMsg time.Time

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tickMsg:
		m.blinkCount++
		m.blink = (m.blinkCount / 3) % 2 == 0
		return m, tea.Tick(time.Millisecond*70, func(t time.Time) tea.Msg {
			return tickMsg(t)
		})
	case tea.KeyMsg:
		if m.showWelcome {
			m.showWelcome = false
			return m, nil
		}
		if m.showHelp {
			switch msg.String() {
			case "q", "esc", "?", "enter", "backspace":
				m.showHelp = false
			}
			return m, nil
		}
		switch msg.String() {
		case "h", "left":
			m.focus = (m.focus + 3) % numBoxes
		case "l", "right":
			m.focus = (m.focus + 1) % numBoxes
		case "j", "down":
			if m.focus < 2 {
				m.focus += 2
			} else {
				m.focus -= 2
			}
		case "k", "up":
			if m.focus >= 2 {
				m.focus -= 2
			} else {
				m.focus += 2
			}
		case "?":
			m.showHelp = true
		case "q", "esc":
			return m, tea.Quit
		}
	}
	return m, nil
}

func (m model) View() string {
	if m.showWelcome {
		fg := lipgloss.NewStyle().Foreground(m.theme.Fg).Background(m.theme.Bg)
		accentFg := lipgloss.NewStyle().Foreground(m.theme.Blue).Background(m.theme.Bg)
		if m.blink {
			accentFg = lipgloss.NewStyle().Foreground(m.theme.Bg).Background(m.theme.Bg)
		}
		welcome := fg.Render("Welcome to ") +
			lipgloss.NewStyle().Foreground(m.theme.Orange).Background(m.theme.Bg).Render("dcorral.com") +
			fg.Render("!") + "\n" +
			fg.Render("press ") + accentFg.Render("any key") + fg.Render(" to continue")
		return welcome
	}
	if m.showHelp {
		return lipgloss.NewStyle().Foreground(m.theme.Fg).Background(m.theme.Bg).Render(
			"Navigation:\n" +
				"h / ←: Move left\n" +
				"l / →: Move right\n" +
				"j / ↓: Move down\n" +
				"k / ↑: Move up\n" +
				"? : Show help\n" +
				"q / Esc: Quit",
		)
	}
	// Render the boxes
	boxes := make([]string, numBoxes)
	for i := range boxes {
		var style lipgloss.Style
		if i == m.focus {
			style = lipgloss.NewStyle().Background(m.theme.Blue).Foreground(m.theme.Bg).Border(lipgloss.NormalBorder()).Padding(0, 1)
		} else {
			style = lipgloss.NewStyle().Background(m.theme.Bg).Foreground(m.theme.Fg).Border(lipgloss.NormalBorder()).Padding(0, 1)
		}
		boxes[i] = style.Render("Box " + string(rune('0'+i)))
	}
	grid := lipgloss.JoinHorizontal(lipgloss.Top, boxes[0], " ", boxes[1]) + "\n" +
		lipgloss.JoinHorizontal(lipgloss.Top, boxes[2], " ", boxes[3]) + "\n" +
		lipgloss.NewStyle().Foreground(m.theme.Fg).Background(m.theme.Bg).Render("Use hjkl or arrows to navigate, ? for help, q to quit")
	return grid
}

func main() {
	// Generate host key
	_, key, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		log.Error("Failed to generate host key", "error", err)
		os.Exit(1)
	}
	block, err := gossh.MarshalPrivateKey(key, "")
	if err != nil {
		log.Error("Failed to marshal host key", "error", err)
		os.Exit(1)
	}
	privateKeyBytes := pem.EncodeToMemory(block)
	log.Info("Generated host key")

	ctx, cancel := context.WithCancel(context.Background())
	signalChan := make(chan os.Signal, 1)
	signal.Notify(signalChan, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
	go func() {
		<-signalChan
		cancel()
	}()

	port := os.Getenv("PORT")
	if port == "" {
		port = "22"
	}

	s, err := wish.NewServer(
		wish.WithAddress(net.JoinHostPort("0.0.0.0", port)),
		wish.WithHostKeyPEM(privateKeyBytes),
		wish.WithMiddleware(
			recover.Middleware(
				bubbletea.Middleware(teaHandler),
				activeterm.Middleware(),
				logging.Middleware(),
			),
		),
		wish.WithPublicKeyAuth(func(ctx ssh.Context, key ssh.PublicKey) bool {
			return true
		}),
		wish.WithKeyboardInteractiveAuth(
			func(ctx ssh.Context, challenger gossh.KeyboardInteractiveChallenge) bool {
				return true
			},
		),
	)
	if err != nil {
		log.Error("Could not start server", "error", err)
		os.Exit(1)
	}

	log.Info("Starting SSH server", "port", port)
	go func() {
		if err = s.ListenAndServe(); err != nil && !errors.Is(err, ssh.ErrServerClosed) {
			log.Error("Could not start server", "error", err)
			cancel()
		}
	}()

	<-ctx.Done()
	s.Shutdown(ctx)
	slog.Info("Shutting down server")
}

func teaHandler(s ssh.Session) (tea.Model, []tea.ProgramOption) {
	return model{
		showWelcome: true,
		focus:       0,
		showHelp:    false,
		theme:       gruvboxDark(),
		blink:       false,
		blinkCount:  0,
	}, []tea.ProgramOption{tea.WithAltScreen()}
}