agentu/internal/tui/app.go

package tui

import (
	"context"
	"errors"
	"fmt"
	"io"
	"math"
	"strings"

	"agentu/internal/agent"
	"agentu/internal/llm"

	"github.com/charmbracelet/bubbles/spinner"
	"github.com/charmbracelet/bubbles/textarea"
	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

const (
	minInputLines = 1
	maxInputLines = 6
)

type Options struct {
	ModelName    string
	Yolo         bool
	ThemeMode    ThemeMode
	ModelManager ModelManager
	WorkingDir   string
}

type ModelManager interface {
	CurrentProvider() string
	CurrentModel() string
	CurrentThinking() string
	CurrentSessionID() string
	CurrentSessionName() string
	Info() string
	SetProvider(name string) (string, error)
	SetModel(model string) (string, error)
	SetThinking(level string) (string, error)
	Save() error
	Resume(id string) error
	Rename(name string) (string, error)
	Sessions() (string, error)
	NewSession() (string, error)
}

func Run(ctx context.Context, assistant *agent.Agent, opts Options) error {
	model := newModel(ctx, assistant, opts)
	_, err := tea.NewProgram(model, tea.WithAltScreen()).Run()
	return err
}

type role string

const (
	roleUser      role = "user"
	roleAssistant role = "assistant"
	roleTool      role = "tool"
	roleError     role = "error"
	roleSystem    role = "system"
)

type message struct {
	role    role
	content string
}

type model struct {
	ctx        context.Context
	agent      *agent.Agent
	modelName  string
	yolo       bool
	models     ModelManager
	workingDir string
	theme      theme
	styles     styles

	viewport viewport.Model
	input    textarea.Model
	spinner  spinner.Model

	width  int
	height int

	messages     []message
	status       string
	contextUsage string
	running      bool
	cancel       context.CancelFunc
	events       <-chan tea.Msg

	// Session picker state
	picking      bool
	pickerItems  []pickerItem
	pickerCursor int
}

type pickerItem struct {
	id        string
	name      string
	detail    string
	isCurrent bool
}

type assistantChunkMsg string
type toolLogMsg string
type turnStartedMsg struct{}
type turnDoneMsg struct {
	err error
}

var errOpenPicker = fmt.Errorf("open picker")

type slashCommand struct {
	Name        string
	Description string
}

var slashCommands = []slashCommand{
	{Name: "/clear", Description: "reset context"},
	{Name: "/compact", Description: "compress context"},
	{Name: "/exit", Description: "quit"},
	{Name: "/quit", Description: "quit"},
	{Name: "/model", Description: "model/provider/thinking"},
	{Name: "/sessions", Description: "list sessions"},
	{Name: "/resume", Description: "resume session"},
	{Name: "/rename", Description: "rename session"},
	{Name: "/new", Description: "new session"},
	{Name: "/status", Description: "show changed files"},
	{Name: "/diff", Description: "show unstaged diff"},
	{Name: "/test", Description: "run project tests"},
}

func newModel(ctx context.Context, assistant *agent.Agent, opts Options) model {
	mode := opts.ThemeMode
	if mode == "" {
		mode = ThemeLight
	}
	th := themeForMode(mode)
	st := th.styles()

	input := textarea.New()
	input.Placeholder = "Message agentu..."
	input.Prompt = ""
	input.ShowLineNumbers = false
	input.MaxHeight = maxInputLines
	input.SetHeight(minInputLines)
	input.SetWidth(80)
	applyTextareaTheme(&input, th)
	input.Focus()

	spin := spinner.New(
		spinner.WithSpinner(spinner.Line),
	)

	vp := viewport.New(80, 20)
	vp.Style = st.Viewport
	vp.SetContent("")

	m := model{
		ctx:        ctx,
		agent:      assistant,
		modelName:  opts.ModelName,
		yolo:       opts.Yolo,
		models:     opts.ModelManager,
		workingDir: opts.WorkingDir,
		theme:      th,
		styles:     st,
		viewport:   vp,
		input:      input,
		spinner:    spin,
		status:     "ready",
	}
	m.refreshContextUsage()
	return m
}

func (m model) Init() tea.Cmd {
	m.syncMessages()
	return textarea.Blink
}

// syncMessages rebuilds the TUI display messages from the agent's conversation history.
func (m *model) syncMessages() {
	if m.agent == nil {
		return
	}
	msgs := m.agent.Messages()
	m.messages = m.messages[:0]
	for _, msg := range msgs {
		switch msg.Role {
		case llm.RoleUser:
			m.messages = append(m.messages, message{role: roleUser, content: msg.Content})
		case llm.RoleAssistant:
			if msg.Content != "" {
				m.messages = append(m.messages, message{role: roleAssistant, content: msg.Content})
			}
		case llm.RoleTool:
			text := cleanToolLog(msg.Content)
			if text != "" {
				m.messages = append(m.messages, message{role: roleTool, content: text})
			}
		}
	}
	m.refreshViewport(true)
}

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

	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.width = msg.Width
		m.height = msg.Height
		m.resize()
		m.refreshViewport(true)
		return m, nil

	case spinner.TickMsg:
		if !m.running {
			return m, nil
		}
		var cmd tea.Cmd
		m.spinner, cmd = m.spinner.Update(msg)
		return m, cmd

	case tea.KeyMsg:
		if m.picking {
			return m.updatePicker(msg)
		}
		switch msg.String() {
		case "ctrl+c":
			if m.cancel != nil {
				m.cancel()
			}
			return m, tea.Quit
		case "esc":
			if m.running && m.cancel != nil {
				m.cancel()
				m.status = "canceling..."
				return m, nil
			}
		case "enter":
			if m.running {
				return m, nil
			}
			return m.submit()
		case "alt+enter", "ctrl+j":
			return m.insertInputNewline()
		}

	case assistantChunkMsg:
		m.appendAssistantChunk(string(msg))
		m.status = "streaming..."
		m.refreshViewport(true)
		return m, m.waitForEvent()

	case toolLogMsg:
		text := cleanToolLog(string(msg))
		if text != "" {
			m.messages = append(m.messages, message{role: roleTool, content: text})
			m.status = text
			m.refreshViewport(true)
		}
		return m, m.waitForEvent()

	case turnDoneMsg:
		m.running = false
		m.events = nil
		m.cancel = nil
		if msg.err != nil {
			m.messages = append(m.messages, message{role: roleError, content: msg.err.Error()})
			m.status = "error"
		} else {
			m.status = "ready"
		}
		// Auto-save session after turn completes
		if m.models != nil {
			_ = m.models.Save()
		}
		m.refreshContextUsage()
		m.resize()
		m.refreshViewport(true)
		cmds = append(cmds, textarea.Blink)
	}

	if keyMsg, ok := msg.(tea.KeyMsg); ok {
		if isViewportKey(keyMsg.String()) {
			nextViewport, cmd := m.viewport.Update(msg)
			m.viewport = nextViewport
			return m, cmd
		}
		if !m.running {
			nextInput, cmd := m.input.Update(msg)
			m.input = nextInput
			m.afterInputChanged()
			return m, cmd
		}
		return m, nil
	}

	if !m.running {
		nextInput, cmd := m.input.Update(msg)
		m.input = nextInput
		m.afterInputChanged()
		cmds = append(cmds, cmd)
	}

	nextViewport, cmd := m.viewport.Update(msg)
	m.viewport = nextViewport
	cmds = append(cmds, cmd)

	return m, tea.Batch(cmds...)
}

func (m model) View() string {
	if m.width <= 0 || m.height <= 0 {
		return "agentu"
	}

	if m.picking {
		parts := []string{m.viewport.View()}
		parts = append(parts, m.pickerView(), m.modelMetaView(), m.footerView())
		body := lipgloss.JoinVertical(lipgloss.Left, parts...)
		return m.styles.App.Width(m.width).Height(m.height).Render(body)
	}

	parts := []string{m.viewport.View()}
	if activity := m.activityView(); activity != "" {
		parts = append(parts, activity)
	}
	parts = append(parts, m.inputView(), m.modelMetaView(), m.footerView())
	body := lipgloss.JoinVertical(lipgloss.Left, parts...)
	return m.styles.App.Width(m.width).Height(m.height).Render(body)
}

func (m *model) submit() (tea.Model, tea.Cmd) {
	input := strings.TrimSpace(m.input.Value())
	if input == "" {
		return *m, nil
	}

	switch input {
	case "/exit", "/quit":
		return *m, tea.Quit
	case "/clear":
		m.agent.Clear()
		m.refreshContextUsage()
		m.messages = []message{{role: roleSystem, content: "Context cleared."}}
		m.input.SetValue("")
		m.afterInputChanged()
		m.status = "ready"
		m.refreshViewport(true)
		return *m, nil
	case "/model", "/compact":
		return m.runLocalCommand(input)
	}

	if strings.HasPrefix(input, "/") {
		return m.runLocalCommand(input)
	}

	m.messages = append(m.messages, message{role: roleUser, content: input})
	m.input.SetValue("")
	m.afterInputChanged()
	m.running = true
	m.status = "thinking..."
	m.resize()
	m.refreshViewport(true)

	turnCtx, cancel := context.WithCancel(m.ctx)
	m.cancel = cancel

	events := make(chan tea.Msg, 256)
	m.events = events

	start := func() tea.Msg {
		go func() {
			defer close(events)
			out := eventWriter{ctx: turnCtx, events: events, assistant: true}
			logs := eventWriter{ctx: turnCtx, events: events}
			err := m.agent.RunTurn(turnCtx, input, out, logs)
			if errors.Is(err, context.Canceled) {
				err = nil
			}
			select {
			case events <- turnDoneMsg{err: err}:
			case <-turnCtx.Done():
			}
		}()
		return turnStartedMsg{}
	}

	return *m, tea.Batch(start, m.waitForEvent(), m.spinner.Tick)
}

func (m *model) insertInputNewline() (tea.Model, tea.Cmd) {
	enter := tea.KeyMsg{Type: tea.KeyEnter}
	nextInput, cmd := m.input.Update(enter)
	m.input = nextInput
	m.afterInputChanged()
	return *m, cmd
}

func (m model) waitForEvent() tea.Cmd {
	events := m.events
	if events == nil {
		return nil
	}
	return func() tea.Msg {
		msg, ok := <-events
		if !ok {
			return turnDoneMsg{}
		}
		return msg
	}
}

func (m *model) appendAssistantChunk(chunk string) {
	if chunk == "" {
		return
	}
	if len(m.messages) == 0 || m.messages[len(m.messages)-1].role != roleAssistant {
		m.messages = append(m.messages, message{role: roleAssistant})
	}
	m.messages[len(m.messages)-1].content += chunk
}

func (m *model) resize() {
	width := max(40, m.width)
	inputWidth := max(20, width-m.styles.InputBox.GetHorizontalFrameSize())
	m.input.SetWidth(inputWidth)
	m.syncInputHeight()

	activityHeight := 0
	if m.running {
		activityHeight = 1
	}
	inputHeight := m.inputBlockHeight()
	footerHeight := 2
	m.viewport.Width = width
	m.viewport.Height = max(4, m.height-activityHeight-inputHeight-footerHeight)
	m.viewport.Style = m.styles.Viewport
}

func (m *model) refreshViewport(bottom bool) {
	m.viewport.SetContent(m.renderMessages())
	if bottom {
		m.viewport.GotoBottom()
	}
}

func (m model) renderMessages() string {
	width := max(40, m.width)
	contentWidth := width
	parts := make([]string, 0, len(m.messages))
	for _, msg := range m.messages {
		content := strings.TrimRight(msg.content, "\n")
		if content == "" {
			continue
		}
		parts = append(parts, m.messageView(msg.role, content, contentWidth))
	}
	if len(parts) == 0 {
		return ""
	}
	return strings.Join(parts, "\n\n")
}

func (m model) messageView(r role, content string, width int) string {
	label := roleLabel(r)
	style := m.styles.AssistantMsg
	labelStyle := m.styles.SystemLabel

	switch r {
	case roleUser:
		style = m.styles.UserMessage
	case roleTool:
		style = m.styles.ToolMessage
		labelStyle = m.styles.ToolLabel
	case roleError:
		style = m.styles.ErrorMessage
		labelStyle = m.styles.ErrorLabel
	case roleSystem:
		style = m.styles.SystemMessage
		labelStyle = m.styles.SystemLabel
	}

	bodyContent := content
	if r == roleAssistant {
		bodyWidth := max(minMarkdownWidth, width-style.GetHorizontalFrameSize())
		bodyContent = renderMarkdown(content, bodyWidth, m.theme)
	}

	bodyWidth := messageBodyWidth(bodyContent, width, style)
	if r == roleUser {
		bodyWidth = width
	}
	body := style.Width(bodyWidth).Render(bodyContent)
	if label == "" {
		return body
	}
	labelLine := labelStyle.Render(label)
	return lipgloss.JoinVertical(lipgloss.Left, labelLine, body)
}

func messageBodyWidth(content string, maxWidth int, style lipgloss.Style) int {
	maxWidth = max(1, maxWidth)
	contentWidth := 1
	for _, line := range strings.Split(content, "\n") {
		contentWidth = max(contentWidth, lipgloss.Width(line))
	}
	return min(maxWidth, contentWidth+style.GetHorizontalFrameSize())
}

func roleLabel(r role) string {
	switch r {
	case roleUser:
		return ""
	case roleAssistant:
		return ""
	case roleTool:
		return "Tool"
	case roleError:
		return "Error"
	case roleSystem:
		return "Note"
	default:
		return string(r)
	}
}

func (m model) modelMetaView() string {
	mode := "read-only tools"
	if m.yolo {
		mode = "yolo tools"
	}
	modelName := m.modelName
	parts := []string{}
	if m.models != nil {
		if sessionName := m.models.CurrentSessionName(); sessionName != "" {
			parts = append(parts, "session "+sessionName)
		}
		if provider := m.models.CurrentProvider(); provider != "" {
			parts = append(parts, "provider "+provider)
		}
		modelName = m.models.CurrentModel()
		if currentThinking := m.models.CurrentThinking(); currentThinking != "" && currentThinking != "unset" {
			parts = append(parts, "thinking "+currentThinking)
		}
	}
	if m.contextUsage != "" {
		parts = append(parts, m.contextUsage)
	}
	parts = append([]string{modelName, mode}, parts...)
	parts = append(parts, "theme "+string(m.theme.Mode))
	line := fitLine(strings.Join(parts, " · "), max(1, m.width-2))
	return m.styles.ModelMeta.Width(max(1, m.width)).Render(line)
}

func (m model) inputView() string {
	suggestions := m.slashSuggestionsView()
	box := m.styles.InputBox.Width(max(20, m.width-2)).Render(m.input.View())
	if suggestions != "" {
		return lipgloss.JoinVertical(lipgloss.Left, suggestions, box)
	}
	return box
}

func (m model) activityView() string {
	if !m.running {
		return ""
	}
	status := strings.TrimSpace(m.status)
	if status == "" || status == "ready" {
		status = "working..."
	}
	line := fitLine(fmt.Sprintf("%s Working · %s · esc cancels", m.spinner.View(), status), max(1, m.width-2))
	return m.styles.Activity.Width(max(1, m.width)).Render(line)
}

func (m model) footerView() string {
	hint := "enter send · ctrl+j newline · alt+enter newline · / commands"
	if m.running {
		hint = "esc cancel · ctrl+c quit"
	}
	return m.styles.Footer.Width(max(1, m.width)).Render(fitLine(hint, max(1, m.width-2)))
}

type eventWriter struct {
	ctx       context.Context
	events    chan<- tea.Msg
	assistant bool
}

func (w eventWriter) Write(p []byte) (int, error) {
	if len(p) == 0 {
		return 0, nil
	}
	text := string(append([]byte(nil), p...))
	var msg tea.Msg
	if w.assistant {
		msg = assistantChunkMsg(text)
	} else {
		msg = toolLogMsg(text)
	}
	select {
	case w.events <- msg:
		return len(p), nil
	case <-w.ctx.Done():
		return 0, w.ctx.Err()
	}
}

func cleanToolLog(text string) string {
	text = strings.TrimSpace(text)
	text = strings.TrimPrefix(text, "[tool]")
	return strings.TrimSpace(text)
}

func isViewportKey(key string) bool {
	switch key {
	case "pgup", "pgdown", "ctrl+up", "ctrl+down":
		return true
	default:
		return false
	}
}

func (m *model) afterInputChanged() {
	m.syncInputHeight()
	if m.width > 0 && m.height > 0 {
		m.resize()
		m.refreshViewport(true)
	}
}

func (m *model) syncInputHeight() {
	m.input.SetHeight(m.desiredInputHeight())
}

func (m model) desiredInputHeight() int {
	value := m.input.Value()
	if value == "" {
		return minInputLines
	}

	textWidth := max(1, m.input.Width())
	lines := 0
	for _, line := range strings.Split(value, "\n") {
		displayWidth := lipgloss.Width(line)
		wrapped := int(math.Ceil(float64(max(1, displayWidth)) / float64(textWidth)))
		lines += max(1, wrapped)
	}
	return min(max(lines, minInputLines), maxInputLines)
}

func (m model) inputBlockHeight() int {
	height := m.input.Height() + m.styles.InputBox.GetVerticalFrameSize()
	if m.showSlashSuggestions() {
		height += m.slashSuggestionCount()
	}
	return height
}

func (m model) slashSuggestionCount() int {
	prefix := strings.TrimSpace(m.input.Value())
	count := 0
	for _, command := range slashCommands {
		if strings.HasPrefix(command.Name, prefix) {
			count++
		}
	}
	if count == 0 {
		count = 1 // "No matching commands"
	}
	return count
}

func (m model) showSlashSuggestions() bool {
	value := strings.TrimSpace(m.input.Value())
	return strings.HasPrefix(value, "/") && !strings.Contains(value, " ")
}

func (m model) slashSuggestionsView() string {
	if !m.showSlashSuggestions() {
		return ""
	}
	prefix := strings.TrimSpace(m.input.Value())
	var parts []string
	for _, command := range slashCommands {
		if !strings.HasPrefix(command.Name, prefix) {
			continue
		}
		parts = append(parts, fmt.Sprintf("%s %s", command.Name, command.Description))
	}
	if len(parts) == 0 {
		parts = append(parts, "No matching commands")
	}
	return m.styles.CommandHint.Width(max(20, m.width-2)).Render(strings.Join(parts, "\n"))
}

func (m model) modelInfo() string {
	if m.models != nil {
		return m.models.Info()
	}
	mode := "read-only tools"
	if m.yolo {
		mode = "yolo tools"
	}
	return fmt.Sprintf("model: %s\nmode: %s\ntheme: %s", m.modelName, mode, m.theme.Mode)
}

func (m *model) refreshContextUsage() {
	m.contextUsage = contextUsageMeta(m.agent)
}

func contextUsageMeta(assistant *agent.Agent) string {
	if assistant == nil {
		return ""
	}
	info := assistant.RuntimeInfo()
	if info.ContextTokens <= 0 && info.MaxContextTokens <= 0 {
		return ""
	}
	used := formatTokenCount(info.ContextTokens)
	if info.MaxContextTokens <= 0 {
		return "ctx ~" + used
	}
	return fmt.Sprintf("ctx ~%s/%s (%s)", used, formatTokenCount(info.MaxContextTokens), contextPercent(info.ContextTokens, info.MaxContextTokens))
}

func contextPercent(used int, limit int) string {
	if limit <= 0 {
		return ""
	}
	if used <= 0 {
		return "0%"
	}
	percent := used * 100 / limit
	if percent == 0 {
		return "<1%"
	}
	return fmt.Sprintf("%d%%", percent)
}

func formatTokenCount(tokens int) string {
	if tokens < 0 {
		tokens = 0
	}
	if tokens < 1000 {
		return fmt.Sprintf("%d", tokens)
	}
	if tokens < 1_000_000 {
		if tokens%1000 == 0 {
			return fmt.Sprintf("%dk", tokens/1000)
		}
		return fmt.Sprintf("%.1fk", float64(tokens)/1000)
	}
	if tokens%1_000_000 == 0 {
		return fmt.Sprintf("%dm", tokens/1_000_000)
	}
	return fmt.Sprintf("%.1fm", float64(tokens)/1_000_000)
}

func fitLine(text string, width int) string {
	width = max(1, width)
	if lipgloss.Width(text) <= width {
		return text
	}
	if width <= 3 {
		return strings.Repeat(".", width)
	}

	target := width - 3
	used := 0
	var b strings.Builder
	for _, r := range text {
		next := lipgloss.Width(string(r))
		if used+next > target {
			break
		}
		b.WriteRune(r)
		used += next
	}
	return b.String() + "..."
}

func (m *model) runLocalCommand(input string) (tea.Model, tea.Cmd) {
	output, err := m.handleLocalCommand(input)
	if err == errOpenPicker {
		m.openSessionPicker()
		return *m, nil
	}
	role := roleSystem
	status := "command"
	if err != nil {
		output = err.Error()
		role = roleError
		status = "command error"
	}
	m.input.SetValue("")
	m.afterInputChanged()
	m.status = status
	// Rebuild display from agent history (matters after /resume and /new)
	m.syncMessages()
	m.refreshContextUsage()
	// Append command output after synced history
	m.messages = append(m.messages, message{role: role, content: output})
	m.refreshViewport(true)
	return *m, nil
}

func (m model) handleLocalCommand(input string) (string, error) {
	fields := strings.Fields(input)
	if len(fields) == 0 {
		return "", fmt.Errorf("empty command")
	}
	switch fields[0] {
	case "/compact":
		return m.handleCompactCommand()
	case "/model":
		return m.handleModelCommand(fields[1:])
	case "/sessions":
		return m.handleSessionsCommand()
	case "/resume":
		return m.handleResumeCommand(fields[1:])
	case "/rename":
		return m.handleRenameCommand(fields[1:])
	case "/new":
		return m.handleNewCommand()
	case "/status":
		return m.handleStatusCommand(fields[1:])
	case "/diff":
		return m.handleDiffCommand(fields[1:])
	case "/test":
		return m.handleTestCommand(fields[1:])
	default:
		return "", fmt.Errorf("unknown command: %s", fields[0])
	}
}

func (m model) handleCompactCommand() (string, error) {
	if m.agent == nil {
		return "", fmt.Errorf("agent is not configured")
	}
	if err := m.agent.Compact(m.ctx); err != nil {
		return "", err
	}
	return "Context compacted.", nil
}

func (m model) handleModelCommand(args []string) (string, error) {
	if m.models == nil {
		if len(args) > 0 {
			return "", fmt.Errorf("model switching is not configured")
		}
		return m.modelInfo(), nil
	}
	if len(args) == 0 || args[0] == "help" {
		return m.models.Info(), nil
	}
	if len(args) == 1 {
		return m.models.SetModel(args[0])
	}
	switch args[0] {
	case "provider":
		if len(args) != 2 {
			return "", fmt.Errorf("usage: /model provider <name>")
		}
		return m.models.SetProvider(args[1])
	case "model":
		if len(args) != 2 {
			return "", fmt.Errorf("usage: /model model <name>")
		}
		return m.models.SetModel(args[1])
	case "thinking":
		if len(args) != 2 {
			return "", fmt.Errorf("usage: /model thinking <none|middle|high|xhigh|max>")
		}
		return m.models.SetThinking(args[1])
	default:
		return "", fmt.Errorf("unknown /model command %q", args[0])
	}
}

func (m model) handleSessionsCommand() (string, error) {
	if m.models == nil {
		return "", fmt.Errorf("session management is not configured")
	}
	return m.models.Sessions()
}

func (m model) handleResumeCommand(args []string) (string, error) {
	if m.models == nil {
		return "", fmt.Errorf("session management is not configured")
	}
	if len(args) > 0 {
		id := strings.TrimSpace(args[0])
		if err := m.models.Resume(id); err != nil {
			return "", err
		}
		return fmt.Sprintf("Resumed session %q.", m.models.CurrentSessionName()), nil
	}
	// No args — open interactive picker (handled in runLocalCommand)
	return "", errOpenPicker
}

func (m model) handleRenameCommand(args []string) (string, error) {
	if m.models == nil {
		return "", fmt.Errorf("session management is not configured")
	}
	if len(args) == 0 {
		return "", fmt.Errorf("usage: /rename <name>")
	}
	name := strings.Join(args, " ")
	return m.models.Rename(name)
}

func (m model) handleNewCommand() (string, error) {
	if m.models == nil {
		return "", fmt.Errorf("session management is not configured")
	}
	return m.models.NewSession()
}

func (m *model) openSessionPicker() {
	if m.models == nil {
		return
	}
	output, err := m.models.Sessions()
	if err != nil {
		m.messages = append(m.messages, message{role: roleError, content: err.Error()})
		return
	}
	// Parse session list into picker items
	m.pickerItems = m.pickerItems[:0]
	m.pickerCursor = 0
	for _, line := range strings.Split(output, "\n") {
		line = strings.TrimSpace(line)
		if line == "" || line == "Sessions:" || strings.HasPrefix(line, "No saved") {
			continue
		}
		// Format: "  id  name  date  msgs (current)"
		fields := strings.Fields(line)
		if len(fields) < 2 {
			continue
		}
		id := fields[0]
		isCurrent := strings.Contains(line, "(current)")
		// Reconstruct display
		m.pickerItems = append(m.pickerItems, pickerItem{
			id:        id,
			name:      line,
			isCurrent: isCurrent,
		})
	}
	if len(m.pickerItems) == 0 {
		m.messages = append(m.messages, message{role: roleSystem, content: "No saved sessions."})
		m.refreshViewport(true)
		return
	}
	// Skip current session in picker, pre-select next one
	for i, item := range m.pickerItems {
		if !item.isCurrent {
			m.pickerCursor = i
			break
		}
	}
	m.picking = true
	m.input.SetValue("")
	m.input.Blur()
	m.refreshViewport(true)
}

func (m *model) updatePicker(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
	switch msg.String() {
	case "ctrl+c", "esc":
		m.picking = false
		m.input.Focus()
		return *m, textarea.Blink
	case "up", "k":
		if m.pickerCursor > 0 {
			m.pickerCursor--
		}
		return *m, nil
	case "down", "j":
		if m.pickerCursor < len(m.pickerItems)-1 {
			m.pickerCursor++
		}
		return *m, nil
	case "enter":
		if m.pickerCursor >= 0 && m.pickerCursor < len(m.pickerItems) {
			item := m.pickerItems[m.pickerCursor]
			m.picking = false
			m.input.Focus()
			if err := m.models.Resume(item.id); err != nil {
				m.messages = append(m.messages, message{role: roleError, content: err.Error()})
			} else {
				m.syncMessages()
				m.messages = append(m.messages, message{role: roleSystem, content: fmt.Sprintf("Resumed session %q.", m.models.CurrentSessionName())})
			}
			m.refreshViewport(true)
		}
		return *m, textarea.Blink
	}
	return *m, nil
}

func (m model) pickerView() string {
	if !m.picking || len(m.pickerItems) == 0 {
		return ""
	}
	width := max(40, m.width-4)
	var b strings.Builder
	b.WriteString(m.styles.Muted.Render("Select a session (↑/↓ navigate, enter select, esc cancel)"))
	b.WriteString("\n\n")
	for i, item := range m.pickerItems {
		line := item.name
		if item.isCurrent {
			line += " (current)"
		}
		if i == m.pickerCursor {
			b.WriteString(m.styles.UserLabel.Render("▸ " + line))
		} else {
			b.WriteString(m.styles.Muted.Render("  " + line))
		}
		b.WriteString("\n")
	}
	return m.styles.InputBox.Width(width).Render(b.String())
}

var _ io.Writer = eventWriter{}