chatter/main.go

package main

import (
	"context"
	"crypto/rand" // For more robust random generation
	"errors"
	"fmt"
	"math/big" // For crypto/rand with charset
	"net"
	"os"
	"os/signal"
	"regexp"
	"sort" // For /users command
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/charmbracelet/bubbles/textarea"
	"github.com/charmbracelet/bubbles/textinput"
	"github.com/charmbracelet/bubbles/viewport"
	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/muesli/termenv"
)

const (
	host                 = "0.0.0.0"
	port                 = "23234"
	maxRoomNameLength    = 24
	roomNameCharset      = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	rateLimitMaxMessages = 15               // Max messages per user within the rateLimitWindow
	rateLimitWindow      = 15 * time.Second // The time window for rate limiting
	maxChatMessageLength = 2000             // Max characters per chat message
)

// generateRandomRoomName creates a random alphanumeric string of a given length.
func generateRandomRoomName(length int) string {
	b := make([]byte, length)
	for i := range b {
		n, err := rand.Int(rand.Reader, big.NewInt(int64(len(roomNameCharset))))
		if err != nil {
			log.Errorf("Error generating random char for room name: %v, falling back for char %d", err, i)
			b[i] = roomNameCharset[0] // Fallback to 'a'
			continue
		}
		b[i] = roomNameCharset[n.Int64()]
	}
	return string(b)
}

type programInfo struct {
	roomName string
	userID   string
}

// app contains a wish server and manages chat rooms and programs.
type app struct {
	*ssh.Server
	activePrograms map[*tea.Program]programInfo // program -> programInfo
	rooms          map[string][]*tea.Program    // roomName -> list of programs in that room
	mu             sync.Mutex
}

// BroadcastToRoom sends a message to all running programs in a specific room,
// optionally excluding one program.
func (a *app) BroadcastToRoom(roomName string, msg tea.Msg, excludeProg *tea.Program) {
	a.mu.Lock()
	defer a.mu.Unlock()

	if progsInRoom, ok := a.rooms[roomName]; ok {
		log.Debugf("Broadcasting to room %s (%d programs, excluding %p): %+v", roomName, len(progsInRoom), excludeProg, msg)
		for _, p := range progsInRoom {
			if excludeProg != nil && p == excludeProg {
				continue
			}
			go p.Send(msg)
		}
	} else {
		log.Warnf("Attempted to broadcast to non-existent or empty room: %s", roomName)
	}
}

func (a *app) GetUserIDsInRoom(roomName string) []string {
	a.mu.Lock()
	defer a.mu.Unlock()

	var userIDs []string
	if progsInRoom, ok := a.rooms[roomName]; ok {
		for _, p := range progsInRoom {
			if info, ok := a.activePrograms[p]; ok {
				userIDs = append(userIDs, info.userID)
			}
		}
	}
	sort.Strings(userIDs) // Sort for consistent display
	return userIDs
}

func newApp() *app {
	a := &app{
		activePrograms: make(map[*tea.Program]programInfo),
		rooms:          make(map[string][]*tea.Program),
	}
	s, err := wish.NewServer(
		wish.WithAddress(net.JoinHostPort(host, port)),
		wish.WithHostKeyPath(".ssh/id_ed25519"),
		wish.WithMiddleware(
			bubbletea.MiddlewareWithProgramHandler(a.ProgramHandler, termenv.ANSI256),
			activeterm.Middleware(),
			logging.Middleware(),
		),
	)
	if err != nil {
		log.Fatal("Could not initialize server", "error", err)
	}

	a.Server = s
	return a
}

func (a *app) Start() {
	var err error
	done := make(chan os.Signal, 1)
	signal.Notify(done, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
	log.Info("Starting SSH server", "host", host, "port", port)
	go func() {
		if err = a.ListenAndServe(); err != nil && !errors.Is(err, ssh.ErrServerClosed) {
			log.Error("Could not start server", "error", err)
			done <- syscall.SIGTERM // Trigger shutdown if server fails to start
		}
	}()

	<-done // Wait for shutdown signal
	log.Info("Stopping SSH server...")
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer func() {
		cancel()
		// Clear program and room data after shutdown attempt
		a.mu.Lock()
		a.activePrograms = make(map[*tea.Program]programInfo)
		a.rooms = make(map[string][]*tea.Program)
		a.mu.Unlock()
		log.Info("Cleared app program stores.")
	}()

	if err := a.Shutdown(ctx); err != nil && !errors.Is(err, ssh.ErrServerClosed) { // Don't log ErrServerClosed as an error during graceful shutdown
		log.Error("Could not gracefully stop server", "error", err)
	}
	log.Info("SSH server stopped.")
}

func (a *app) ProgramHandler(s ssh.Session) *tea.Program {
	userID := s.User()
	if userID == "" {
		userID = "guest" // Default userID if empty
	}
	m := initialModel(a, userID)
	p := tea.NewProgram(m, bubbletea.MakeOptions(s)...)
	m.SetProgram(p) // Give the model a reference to its own program
	a.addProgram(p, userID)
	return p
}

func (a *app) addProgram(p *tea.Program, userID string) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.activePrograms[p] = programInfo{roomName: "", userID: userID}
	log.Debugf("Program %p added for user %s (unassigned)", p, userID)
}

func (a *app) AssignProgramToRoom(prog *tea.Program, roomName string) {
	a.mu.Lock()
	defer a.mu.Unlock()

	currentInfo, exists := a.activePrograms[prog]
	if !exists {
		log.Warnf("Program %p not found in activePrograms, cannot assign to room %s", prog, roomName)
		return
	}
	userID := currentInfo.userID
	currentRoom := currentInfo.roomName

	// If program was in a different room, remove it from the old room's list
	if currentRoom != "" && currentRoom != roomName {
		if progsInOldRoom, ok := a.rooms[currentRoom]; ok {
			var updatedRoomProgs []*tea.Program
			for _, pInRoom := range progsInOldRoom {
				if pInRoom != prog {
					updatedRoomProgs = append(updatedRoomProgs, pInRoom)
				}
			}
			if len(updatedRoomProgs) > 0 {
				a.rooms[currentRoom] = updatedRoomProgs
			} else {
				delete(a.rooms, currentRoom) // Clean up empty room
			}
			log.Debugf("Program %p (user: %s) moved from room %s", prog, userID, currentRoom)
		}
	}

	// Ensure the new room exists in the map
	if _, ok := a.rooms[roomName]; !ok {
		a.rooms[roomName] = []*tea.Program{}
	}

	// Add program to the new room's list if not already there
	foundInNewRoomList := false
	for _, pInList := range a.rooms[roomName] {
		if pInList == prog {
			foundInNewRoomList = true
			break
		}
	}
	if !foundInNewRoomList {
		a.rooms[roomName] = append(a.rooms[roomName], prog)
	}

	a.activePrograms[prog] = programInfo{roomName: roomName, userID: userID}
	log.Infof("Program %p assigned/confirmed in room %s (user: %s)", prog, roomName, userID)
}

func (a *app) HandleUserExitFromRoom(prog *tea.Program, oldRoomName string) {
	a.mu.Lock()

	info, exists := a.activePrograms[prog]
	if !exists {
		a.mu.Unlock()
		log.Warnf("Program %p tried to exit room but not found in activePrograms.", prog)
		return
	}
	if info.roomName == "" || info.roomName != oldRoomName {
		a.mu.Unlock()
		log.Warnf("Program %p (user: %s) tried to exit room %s but was not in it (actual: '%s').", prog, info.userID, oldRoomName, info.roomName)
		return
	}
	userID := info.userID

	leaveMsgText := fmt.Sprintf("%s has left the room.", userID)
	var recipients []*tea.Program
	if progs, ok := a.rooms[info.roomName]; ok {
		recipients = make([]*tea.Program, 0, len(progs))
		for _, p := range progs {
			if p != prog {
				recipients = append(recipients, p)
			}
		}
	}

	var updatedRoomProgs []*tea.Program
	if progsInRoom, ok := a.rooms[info.roomName]; ok {
		for _, pInRoom := range progsInRoom {
			if pInRoom != prog {
				updatedRoomProgs = append(updatedRoomProgs, pInRoom)
			}
		}
	}

	if len(updatedRoomProgs) > 0 {
		a.rooms[info.roomName] = updatedRoomProgs
	} else {
		delete(a.rooms, info.roomName)
	}
	a.activePrograms[prog] = programInfo{roomName: "", userID: userID}
	a.mu.Unlock() // Unlock before broadcasting

	if len(recipients) > 0 {
		for _, p := range recipients {
			go p.Send(chatMsg{id: "system", text: leaveMsgText, room: oldRoomName, isSystemMessage: true})
		}
		log.Infof("Broadcasted leave message for user %s from room %s (commanded exit)", userID, oldRoomName)
	}
	log.Infof("Program %p (user: %s) exited room %s via /exit command.", prog, userID, oldRoomName)
}

func (a *app) RemoveProgram(prog *tea.Program) {
	a.mu.Lock()

	info, exists := a.activePrograms[prog]
	if !exists {
		a.mu.Unlock()
		log.Warnf("Attempted to remove unknown or already removed program: %p", prog)
		return
	}
	userID := info.userID
	roomName := info.roomName

	var leaveRecipients []*tea.Program
	var leaveMsgText string

	if roomName != "" {
		leaveMsgText = fmt.Sprintf("%s has disconnected.", userID)
		if progs, ok := a.rooms[roomName]; ok {
			leaveRecipients = make([]*tea.Program, 0, len(progs))
			for _, p := range progs {
				if p != prog {
					leaveRecipients = append(leaveRecipients, p)
				}
			}
		}
	}

	if roomName != "" {
		var updatedRoomProgs []*tea.Program
		if progsInRoom, ok := a.rooms[roomName]; ok {
			for _, pInRoom := range progsInRoom {
				if pInRoom != prog {
					updatedRoomProgs = append(updatedRoomProgs, pInRoom)
				}
			}
		}
		if len(updatedRoomProgs) > 0 {
			a.rooms[roomName] = updatedRoomProgs
		} else {
			delete(a.rooms, roomName)
		}
		log.Infof("Program %p (user: %s) removed from room %s tracking (full disconnect).", prog, userID, roomName)
	}

	delete(a.activePrograms, prog)
	a.mu.Unlock() // Unlock before broadcasting

	if roomName != "" && len(leaveRecipients) > 0 {
		for _, p := range leaveRecipients {
			go p.Send(chatMsg{id: "system", text: leaveMsgText, room: roomName, isSystemMessage: true})
		}
		log.Infof("Broadcasted disconnect message for user %s from room %s.", userID, roomName)
	}
	log.Infof("Program %p (user: %s) removed from active list (full disconnect).", prog, userID)
}

func main() {
	// Optional: Setup file logging
	// logFile, err := os.OpenFile("chatter_server.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	// if err == nil {
	// 	defer logFile.Close()
	// 	// You can use a multiwriter to log to both stderr and file if desired
	// 	// log.Default().SetOutput(io.MultiWriter(os.Stderr, logFile))
	// 	log.Default().SetOutput(logFile) // Log only to file
	// 	log.SetTimeFormat(time.RFC3339)
	// 	log.SetLevel(log.DebugLevel) // Set desired log level
	// } else {
	// 	log.Error("Failed to open log file", "error", err)
	// }

	app := newApp()
	app.Start()
}

type (
	errMsg  error    // Used for tea.Cmd to send errors to Update
	chatMsg struct { // Used for tea.Cmd to send chat messages to Update
		id              string
		text            string
		room            string
		isSystemMessage bool
	}
)

type modelPhase int

const (
	phaseRoomInput modelPhase = iota
	phaseChat
)

var roomNameRegex = regexp.MustCompile("^[a-zA-Z0-9]{1," + fmt.Sprintf("%d", maxRoomNameLength) + "}$")

func isValidRoomName(name string) bool {
	return roomNameRegex.MatchString(name)
}

type model struct {
	app                *app
	program            *tea.Program // Reference to the Bubble Tea program managing this model
	phase              modelPhase
	roomInput          textinput.Model
	currentRoom        string
	id                 string // User ID from SSH session
	viewport           viewport.Model
	messages           []string // Chat messages displayed in the viewport
	textarea           textarea.Model
	senderStyle        lipgloss.Style
	systemMessageStyle lipgloss.Style // For join/leave/command output (not for m.err)
	messageTimestamps  []time.Time    // For rate limiting user messages
	err                error          // For displaying transient input errors to the user (e.g., rate limit, too long)
}

func initialModel(appInstance *app, userID string) *model {
	roomTi := textinput.New()
	roomTi.Placeholder = "e.g., 'dev-chat' or 'random' (or press Enter for random)"
	roomTi.Focus()
	roomTi.CharLimit = maxRoomNameLength
	roomTi.Width = 50

	ta := textarea.New()
	ta.Placeholder = "Type your message or a command (e.g. /help)..."
	ta.Prompt = "┃ "
	ta.CharLimit = maxChatMessageLength              // User-facing limit in textarea
	ta.SetWidth(60)                                  // Example width, adjust as needed
	ta.SetHeight(3)                                  // Multi-line input area
	ta.FocusedStyle.CursorLine = lipgloss.NewStyle() // No special styling for cursor line
	ta.ShowLineNumbers = false
	ta.KeyMap.InsertNewline.SetEnabled(false) // Use Enter to send, not for newlines in message

	vp := viewport.New(60, 15) // Example dimensions, adjust as needed
	vp.SetContent("Welcome! Please enter a room name to join or create.")

	return &model{
		app:                appInstance,
		id:                 userID,
		phase:              phaseRoomInput,
		roomInput:          roomTi,
		textarea:           ta,
		messages:           []string{},
		messageTimestamps:  []time.Time{}, // Initialize for rate limiting
		viewport:           vp,
		senderStyle:        lipgloss.NewStyle().Foreground(lipgloss.Color("12")),                                      // Light Blue for sender ID
		systemMessageStyle: lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "#909090", Dark: "#6C6C6C"}), // Grey for system messages
		err:                nil,                                                                                       // No error initially
	}
}

func (m *model) SetProgram(p *tea.Program) {
	m.program = p
}

func (m *model) Init() tea.Cmd {
	switch m.phase {
	case phaseRoomInput:
		return textinput.Blink
	case phaseChat:
		return textarea.Blink
	default:
		return nil
	}
}

func (m *model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	var cmds []tea.Cmd
	var cmd tea.Cmd

	switch m.phase {
	case phaseRoomInput:
		switch keyEvent := msg.(type) {
		case tea.KeyMsg:
			switch keyEvent.Type {
			case tea.KeyCtrlC, tea.KeyEsc:
				if m.program != nil {
					m.app.RemoveProgram(m.program) // Deregister before quitting
				}
				return m, tea.Quit
			case tea.KeyEnter:
				roomName := strings.TrimSpace(m.roomInput.Value())
				if roomName == "" { // Generate random room name if input is empty
					roomName = generateRandomRoomName(8) // Shorter random name for readability
					m.roomInput.SetValue(roomName)       // Show generated name in input briefly
					log.Infof("User %s generated random room name: %s", m.id, roomName)
				}

				if isValidRoomName(roomName) {
					m.currentRoom = roomName
					m.phase = phaseChat
					m.err = nil // Clear any previous error from room input phase

					if m.program == nil {
						log.Error("CRITICAL: m.program is nil when trying to assign to room.")
						m.err = errors.New("internal setup error: program reference missing")
						return m, nil // Stay in current phase with error displayed
					}
					m.app.AssignProgramToRoom(m.program, m.currentRoom)

					joinMsgText := fmt.Sprintf("%s has joined the room.", m.id)
					m.app.BroadcastToRoom(m.currentRoom, chatMsg{
						id:              "system",
						text:            joinMsgText,
						room:            m.currentRoom,
						isSystemMessage: true,
					}, nil) // Broadcast to all, including self

					m.textarea.Focus()
					m.roomInput.Blur()
					// Initial welcome message for the room, not appended to m.messages directly to avoid duplication
					m.viewport.SetContent(fmt.Sprintf("Welcome to room '%s'! (User: %s)\nType /help for commands.", m.currentRoom, m.id))
					m.messages = []string{} // Clear message history from potential previous room/session
					cmds = append(cmds, textarea.Blink)
				} else {
					m.err = fmt.Errorf("invalid room name: use 1-%d alphanumeric characters", maxRoomNameLength)
					m.roomInput.Focus() // Keep focus on room input if error
					cmds = append(cmds, textinput.Blink)
				}
				return m, tea.Batch(cmds...)
			}
		case errMsg: // This would be an error from a command, not typically used in room input phase
			m.err = keyEvent
			return m, nil
		}
		m.roomInput, cmd = m.roomInput.Update(msg)
		cmds = append(cmds, cmd)

	case phaseChat:
		// Order of updates: components first, then specific message handling.
		m.textarea, cmd = m.textarea.Update(msg)
		cmds = append(cmds, cmd)
		m.viewport, cmd = m.viewport.Update(msg) // Handles scrolling based on content changes
		cmds = append(cmds, cmd)

		switch event := msg.(type) {
		case tea.KeyMsg:
			// If a key is pressed (and it's not Enter potentially causing a new error),
			// and there was a previous user input error (m.err), clear it.
			if m.err != nil && event.Type != tea.KeyEnter {
				isTextModifyingKey := false
				switch event.Type {
				case tea.KeyRunes, tea.KeySpace, tea.KeyBackspace, tea.KeyDelete:
					isTextModifyingKey = true
				}
				if isTextModifyingKey {
					m.err = nil // Clear error as user types new input
				}
			}

			switch event.Type {
			case tea.KeyCtrlC, tea.KeyEsc:
				if m.program != nil {
					m.app.RemoveProgram(m.program)
				}
				return m, tea.Quit

			case tea.KeyEnter:
				val := strings.TrimSpace(m.textarea.Value())
				m.textarea.Reset() // Reset textarea immediately after getting value

				if strings.HasPrefix(val, "/") {
					m.err = nil // Clear previous input errors when a command is attempted
					parts := strings.Fields(val)
					command := parts[0]
					// args := parts[1:] // For future use

					switch command {
					case "/help":
						helpText := m.systemMessageStyle.Render(`Available commands:
  /help         Show this help message.
  /exit         Leave the current room.
  /users        List users in this room.`)
						m.messages = append(m.messages, helpText)
					case "/exit", "/leave":
						if m.program != nil && m.currentRoom != "" {
							m.app.HandleUserExitFromRoom(m.program, m.currentRoom)
						}
						m.phase = phaseRoomInput
						m.currentRoom = ""
						m.messages = []string{}
						m.err = nil // Ensure error is clear when changing phase
						m.roomInput.Reset()
						m.roomInput.Placeholder = "Enter another room or press Enter for random..."
						m.roomInput.Focus()
						m.textarea.Blur()
						m.viewport.SetContent("You have left the room. Enter a new room name.")
						cmds = append(cmds, textinput.Blink)
						return m, tea.Batch(cmds...) // Return early as state has significantly changed
					case "/users":
						if m.currentRoom != "" {
							userIDs := m.app.GetUserIDsInRoom(m.currentRoom)
							var userListText string
							if len(userIDs) > 0 {
								userListText = "Users in '" + m.currentRoom + "':\n  " + strings.Join(userIDs, "\n  ")
							} else {
								// This case (only one here) should be handled by GetUserIDsInRoom including self.
								userListText = "It seems you are the only one here."
							}
							m.messages = append(m.messages, m.systemMessageStyle.Render(userListText))
						} else {
							// This should not happen if in phaseChat, currentRoom should be set.
							m.messages = append(m.messages, m.systemMessageStyle.Render("Error: Not in a room."))
						}
					default:
						m.messages = append(m.messages, m.systemMessageStyle.Render("Unknown command: "+command))
					}
					// Update viewport with command output
					m.viewport.SetContent(strings.Join(m.messages, "\n"))
					m.viewport.GotoBottom()

				} else if val != "" { // Regular chat message attempt
					// 1. Message Length Check
					if len(val) > maxChatMessageLength {
						m.err = fmt.Errorf("message too long (max %d chars). Not sent.", maxChatMessageLength)
					} else {
						// 2. Rate Limiting Check
						now := time.Now()
						// Remove timestamps older than the window
						var recentTimestamps []time.Time
						for _, ts := range m.messageTimestamps {
							if now.Sub(ts) < rateLimitWindow {
								recentTimestamps = append(recentTimestamps, ts)
							}
						}
						m.messageTimestamps = recentTimestamps

						if len(m.messageTimestamps) >= rateLimitMaxMessages {
							m.err = fmt.Errorf("too many messages (max %d per %s). Wait. Not sent.", rateLimitMaxMessages, rateLimitWindow.String())
						} else {
							// SUCCESSFUL SEND
							m.err = nil                                            // Clear any prior input error
							m.messageTimestamps = append(m.messageTimestamps, now) // Add current message's timestamp

							m.app.BroadcastToRoom(m.currentRoom, chatMsg{
								id:              m.id,
								text:            val,
								room:            m.currentRoom,
								isSystemMessage: false,
							}, nil) // Broadcast to all, including self (sender)
						}
					}
				} else { // val == "" (empty input submitted via Enter)
					m.err = nil // Clear any previous error, do nothing for empty message
				}
				// After sending, command, or empty Enter, ensure textarea is focused for next input
				cmds = append(cmds, m.textarea.Focus(), textarea.Blink)

			} // end switch event.Type (inner for KeyMsg)

		case chatMsg: // Received a message (could be own, from others, or system)
			// Process only if message is for the current room
			if event.room == m.currentRoom {
				var styledMessage string
				if event.isSystemMessage {
					styledMessage = m.systemMessageStyle.Render(event.text)
				} else {
					styledId := m.senderStyle.Render(event.id)
					// Handle potential multi-line messages by ensuring they are displayed correctly
					messageText := strings.ReplaceAll(event.text, "\n", "\n  ") // Indent subsequent lines
					styledMessage = styledId + ": " + messageText
				}
				m.messages = append(m.messages, styledMessage)
				m.viewport.SetContent(strings.Join(m.messages, "\n"))
				m.viewport.GotoBottom()
			} else if event.room != "" && !event.isSystemMessage {
				// Log if a non-system message for a different room is somehow received by this model's Update
				log.Warnf("Client '%s' in room '%s' received non-system message for different room '%s': %s", m.id, m.currentRoom, event.room, event.text)
			}

		case errMsg: // This is for system/internal errors passed as errMsg type to Update
			m.err = event // Display this error using the m.err mechanism
			log.Error("Internal error in model", "user", m.id, "room", m.currentRoom, "error", event)
		}
	}
	return m, tea.Batch(cmds...)
}

func (m *model) View() string {
	var viewBuilder strings.Builder

	titleStyle := lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("63")) // Purple for titles
	errorStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("9")).Bold(true)  // Red for m.err

	switch m.phase {
	case phaseRoomInput:
		viewBuilder.WriteString(titleStyle.Render("chatter.sh") + "\n\n")
		viewBuilder.WriteString("Please enter a room name to join or create.\n")
		viewBuilder.WriteString(fmt.Sprintf("Rules: 1-%d characters, letters (a-z, A-Z) and numbers (0-9) only.\n", maxRoomNameLength))
		viewBuilder.WriteString("(Leave empty and press Enter for a random room name.)\n\n")
		viewBuilder.WriteString(m.roomInput.View())
		viewBuilder.WriteString("\n\n(Ctrl+C or Esc to quit)")
	case phaseChat:
		header := fmt.Sprintf("Room: %s / User: %s (type /help for commands)", m.currentRoom, m.id)
		viewBuilder.WriteString(titleStyle.Render(header) + "\n")
		// Simple border for viewport content
		viewBuilder.WriteString(lipgloss.NewStyle().BorderStyle(lipgloss.RoundedBorder()).Padding(0, 1).Render(m.viewport.View()) + "\n")
		viewBuilder.WriteString(m.textarea.View())
		viewBuilder.WriteString("\n(Ctrl+C or Esc to quit)")
	default:
		viewBuilder.WriteString("Unknown application state. This is a bug.")
	}

	// Display m.err if it's set (for transient input errors like rate limit, too long message)
	if m.err != nil {
		viewBuilder.WriteString("\n\n" + errorStyle.Render("Error: "+m.err.Error()))
	}

	return viewBuilder.String() + "\n"
}