feat(tui): add slide navigation command interface

- add `Command` struct with list-based slide navigation
- implement keyboard controls for slide selection and filtering
- add styling and layout for the navigation modal
- support slide title display with fallback numbering
- include quit and selection handling with proper state management

Author: tharropoulos

internal/tui/command.go

@@ -0,0 +1,185 @@
+package tui
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/charmbracelet/bubbles/key"
+	"github.com/charmbracelet/bubbles/list"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+)
+
+var (
+	titleStyle = lipgloss.NewStyle()
+	itemStyle  = lipgloss.NewStyle().
+			PaddingLeft(2)
+	selectedItemStyle = lipgloss.NewStyle().
+				Foreground(lipgloss.Color("#9999CC"))
+	paginationStyle = list.DefaultStyles().PaginationStyle.
+			PaddingLeft(2)
+	helpStyle = list.DefaultStyles().HelpStyle.
+			PaddingLeft(2).
+			PaddingBottom(2)
+	quitTextStyle = lipgloss.NewStyle().
+			Margin(0, 0, 0, 2)
+)
+
+type SlideItem struct {
+	slide  *Slide
+	title  string
+	number int
+}
+
+func (s SlideItem) FilterValue() string { return s.title }
+
+type itemDelegate struct{}
+
+func (d itemDelegate) Height() int                             { return 1 }
+func (d itemDelegate) Spacing() int                            { return 0 }
+func (d itemDelegate) Update(_ tea.Msg, _ *list.Model) tea.Cmd { return nil }
+func (d itemDelegate) Render(w io.Writer, m list.Model, index int, listItem list.Item) {
+	i, ok := listItem.(SlideItem)
+	if !ok {
+		return
+	}
+
+	str := fmt.Sprintf("%d. %s", i.number, i.title)
+
+	fn := itemStyle.Render
+	if index == m.Index() {
+		fn = func(s ...string) string {
+			return selectedItemStyle.Render("> " + strings.Join(s, " "))
+		}
+	}
+
+	fmt.Fprint(w, fn(str))
+}
+
+type Command struct {
+	list     list.Model
+	choice   *Slide
+	quitting bool
+}
+
+func NewCommand(rootSlide *Slide) Command {
+	items := []list.Item{}
+
+	current := rootSlide
+	slideNumber := 1
+
+	for current != nil {
+		title := current.Properties.Title
+		if title == "" {
+			title = fmt.Sprintf("#%d", slideNumber)
+		}
+
+		items = append(items, SlideItem{
+			slide:  current,
+			title:  title,
+			number: slideNumber,
+		})
+
+		current = current.Next
+		slideNumber++
+	}
+
+	const modalWidth = 90
+	const listHeight = 10
+
+	l := list.New(items, itemDelegate{}, modalWidth, listHeight)
+	l.Title = "Go to Slide"
+	l.SetShowStatusBar(false)
+	l.SetFilteringEnabled(true)
+	l.SetShowHelp(true)
+
+	l.Styles.PaginationStyle = paginationStyle
+	l.Styles.Title = titleStyle
+	l.Styles.HelpStyle = helpStyle
+
+	l.Styles.NoItems = lipgloss.NewStyle().
+		MarginLeft(0).
+		Foreground(lipgloss.Color("240"))
+
+	l.KeyMap.Filter = key.NewBinding(
+		key.WithKeys("f"),
+		key.WithHelp("f", "filter"),
+	)
+
+	return Command{list: l}
+}
+
+func (m Command) Init() tea.Cmd {
+	return nil
+}
+
+func (m Command) Update(msg tea.Msg) (Command, tea.Cmd) {
+	switch msg := msg.(type) {
+	case tea.WindowSizeMsg:
+		m.list.SetWidth(msg.Width)
+		return m, nil
+
+	case tea.KeyMsg:
+		switch keypress := msg.String(); keypress {
+		case "ctrl+c", "q":
+			m.quitting = true
+			return m, tea.Quit
+		case "esc":
+			// If currently filtering, let the list handle it (clear filter)
+			// Otherwise, quit the modal
+			if m.list.FilterState() == list.Filtering || m.list.FilterState() == list.FilterApplied {
+				var cmd tea.Cmd
+				m.list, cmd = m.list.Update(msg)
+				return m, cmd
+			} else {
+				m.quitting = true
+				return m, tea.Quit
+			}
+		case "enter":
+			if item := m.list.SelectedItem(); item != nil {
+				if i, ok := item.(SlideItem); ok {
+					m.choice = i.slide
+				}
+			}
+			m.quitting = true
+			return m, tea.Quit
+		}
+	}
+
+	var cmd tea.Cmd
+	m.list, cmd = m.list.Update(msg)
+	return m, cmd
+}
+
+func (m Command) View() string {
+	if m.choice != nil {
+		title := m.choice.Properties.Title
+		if title == "" {
+			title = "selected slide"
+		}
+		return quitTextStyle.Render(fmt.Sprintf("Navigating to: %s", title))
+	}
+	if m.quitting {
+		return quitTextStyle.Render("Cancelled.")
+	}
+
+	content := lipgloss.Place(
+		90,
+		15,
+		lipgloss.Left,
+		lipgloss.Center,
+		m.list.View(),
+	)
+
+	return "\n" + content
+}
+
+func (m Command) Choice() *Slide {
+	return m.choice
+}
+
+type OpenCommandMsg struct{}
+type CloseCommandMsg struct {
+	SelectedSlide *Slide
+}