scrawl/main.go

package main

import (
	"context"
	"errors"
	"log"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"

	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
	"github.com/charmbracelet/ssh"
	"github.com/charmbracelet/wish"
	"github.com/charmbracelet/wish/logging"
	"github.com/muesli/termenv"

	"scrawl/game"
)

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "23235"
	}
	hostKeyPath := os.Getenv("HOST_KEY_PATH")
	if hostKeyPath == "" {
		hostKeyPath = ".ssh/scrawl_host_key"
	}

	canvas := game.NewCanvas()

	// Not wish/bubbletea's bm.Middleware helper -- that hides the
	// *tea.Program behind its own closure, and the whole point of this
	// app is a shared canvas that broadcasts a redraw to every OTHER
	// connected session the moment one of them paints. Building the
	// program directly keeps that reference so canvas.Join/Leave can
	// register it. Same "no shell, no exec" guarantee as delve-term:
	// this program is the entire session handler, nothing else is ever
	// reachable through it.
	scrawlMiddleware := func(next ssh.Handler) ssh.Handler {
		return func(s ssh.Session) {
			pty, winCh, isPty := s.Pty()
			if !isPty {
				next(s)
				return
			}

			id := game.RandomID()
			label := s.User()
			if label == "" {
				label = id
			}

			// A renderer bound to lipgloss's package-level default detects
			// color support from the *server process's* os.Stdout -- not
			// this session's actual terminal, and that stdout is typically
			// redirected (a log file, systemd journal), so every session
			// would silently lose all color/background styling at once.
			// Confirmed by hitting exactly that: a cursor's background
			// highlight change produced zero output bytes over live SSH
			// until styles were rebound to a per-session renderer forced
			// to color output.
			renderer := lipgloss.NewRenderer(s)
			renderer.SetColorProfile(termenv.TrueColor)
			m := game.NewModel(canvas, id, label, renderer)

			p := tea.NewProgram(m,
				tea.WithInput(s),
				tea.WithOutput(s),
				tea.WithAltScreen(),
			)

			canvas.Join(id, label, p)
			defer canvas.Leave(id)

			go func() {
				for w := range winCh {
					p.Send(tea.WindowSizeMsg{Width: w.Width, Height: w.Height})
				}
			}()
			// Async, same reason as canvas.go's broadcastLocked: Program.Send
			// blocks until Run()'s event loop is reading from it, which hasn't
			// started yet at this line -- an inline Send here deadlocked every
			// session before it ever reached Run(), confirmed by testing.
			go p.Send(tea.WindowSizeMsg{Width: pty.Window.Width, Height: pty.Window.Height})

			if _, err := p.Run(); err != nil {
				log.Printf("session error: %v", err)
			}
		}
	}

	s, err := wish.NewServer(
		wish.WithAddress(net.JoinHostPort("0.0.0.0", port)),
		wish.WithHostKeyPath(hostKeyPath),
		wish.WithMiddleware(
			scrawlMiddleware,
			logging.Middleware(),
		),
	)
	if err != nil {
		log.Fatalln(err)
	}

	done := make(chan os.Signal, 1)
	signal.Notify(done, os.Interrupt, syscall.SIGTERM)
	log.Printf("scrawl listening on :%s", port)
	go func() {
		if err = s.ListenAndServe(); err != nil && !errors.Is(err, ssh.ErrServerClosed) {
			log.Fatalln(err)
		}
	}()

	<-done
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	if err := s.Shutdown(ctx); err != nil {
		log.Fatalln(err)
	}
}