Implement TUI pane navigation

internal/tui/model.go

@@ -3,8 +3,10 @@ package tui
 import (
 	"fmt"
 	"hosts-go/internal/core"
+	"strings"
 
 	list "github.com/charmbracelet/bubbles/list"
+	viewport "github.com/charmbracelet/bubbles/viewport"
 	tea "github.com/charmbracelet/bubbletea"
 )
 
@@ -30,12 +32,21 @@ const (
 	EditMode
 )
 
+type pane int
+
+const (
+	listPane pane = iota
+	detailPane
+)
+
 type Model struct {
 	list   list.Model
+	detail viewport.Model
 	hosts  *core.HostsFile
 	width  int
 	height int
 	mode   Mode
+	focus  pane
 }
 
 // NewModel constructs the TUI model from a parsed HostsFile.
@@ -51,11 +62,39 @@ func NewModel(hf *core.HostsFile) Model {
 	l.SetShowHelp(false)
 	l.SetShowPagination(false)
 
-	return Model{
+	m := Model{
 		list:   l,
+		detail: viewport.New(0, 0),
 		hosts:  hf,
 		mode:   ViewMode,
+		focus:  listPane,
 	}
+	m.refreshDetail()
+	return m
+}
+
+func (m *Model) refreshDetail() {
+	if len(m.hosts.Entries) == 0 {
+		m.detail.SetContent("")
+		return
+	}
+	entry := m.hosts.Entries[m.list.Index()]
+	var b strings.Builder
+	status := "active"
+	if !entry.Active {
+		status = "inactive"
+	}
+	fmt.Fprintf(&b, "IP: %s\n", entry.IP)
+	fmt.Fprintf(&b, "Host: %s\n", entry.Hostname)
+	if len(entry.Aliases) > 0 {
+		fmt.Fprintf(&b, "Aliases: %s\n", strings.Join(entry.Aliases, ", "))
+	}
+	if entry.Comment != "" {
+		fmt.Fprintf(&b, "Comment: %s\n", entry.Comment)
+	}
+	fmt.Fprintf(&b, "Status: %s", status)
+	m.detail.SetContent(b.String())
+	m.detail.YOffset = 0
 }
 
 // Init satisfies tea.Model.

internal/tui/update.go

@@ -12,13 +12,47 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		switch msg.String() {
 		case "q", "ctrl+c":
 			return m, tea.Quit
+		case "tab":
+			if m.focus == listPane {
+				m.focus = detailPane
+			} else {
+				m.focus = listPane
+			}
+		case "up", "k":
+			if m.focus == detailPane {
+				m.detail.LineUp(1)
+			} else {
+				m.list, cmd = m.list.Update(msg)
+				m.refreshDetail()
+			}
+			return m, cmd
+		case "down", "j":
+			if m.focus == detailPane {
+				m.detail.LineDown(1)
+			} else {
+				m.list, cmd = m.list.Update(msg)
+				m.refreshDetail()
+			}
+			return m, cmd
+		}
+		if m.focus == listPane {
+			m.list, cmd = m.list.Update(msg)
+			m.refreshDetail()
 		}
 	case tea.WindowSizeMsg:
 		m.width = msg.Width
-		m.height = msg.Height
-		m.list.SetSize(msg.Width/2, msg.Height)
-	}
-
+		m.height = msg.Height - 1
+		m.list.SetSize(msg.Width/2, m.height)
+		m.detail.Width = msg.Width - msg.Width/2
+		m.detail.Height = m.height
+		if m.focus == listPane {
 			m.list, cmd = m.list.Update(msg)
+		}
+	default:
+		if m.focus == listPane {
+			m.list, cmd = m.list.Update(msg)
+			m.refreshDetail()
+		}
+	}
 	return m, cmd
 }

internal/tui/view.go

@@ -2,7 +2,6 @@ package tui
 
 import (
 	"fmt"
-	"strings"
 
 	"github.com/charmbracelet/lipgloss"
 )
@@ -10,33 +9,22 @@ import (
 var (
 	listStyle    = lipgloss.NewStyle().Padding(0, 1)
 	detailStyle  = lipgloss.NewStyle().Padding(0, 1)
+	focusedStyle = lipgloss.NewStyle().BorderStyle(lipgloss.RoundedBorder()).BorderForeground(lipgloss.Color("62"))
 	statusStyle  = lipgloss.NewStyle().Padding(0, 1).Foreground(lipgloss.Color("240")).Background(lipgloss.Color("236"))
 )
 
 // View renders the two-pane layout.
 func (m Model) View() string {
 	listView := m.list.View()
-
-	var detail strings.Builder
-	if len(m.hosts.Entries) > 0 {
-		entry := m.hosts.Entries[m.list.Index()]
-		status := "active"
-		if !entry.Active {
-			status = "inactive"
-		}
-		fmt.Fprintf(&detail, "IP: %s\n", entry.IP)
-		fmt.Fprintf(&detail, "Host: %s\n", entry.Hostname)
-		if len(entry.Aliases) > 0 {
-			fmt.Fprintf(&detail, "Aliases: %s\n", strings.Join(entry.Aliases, ", "))
-		}
-		if entry.Comment != "" {
-			fmt.Fprintf(&detail, "Comment: %s\n", entry.Comment)
-		}
-		fmt.Fprintf(&detail, "Status: %s", status)
-	}
+	detailView := m.detail.View()
 
 	left := listStyle.Width(m.width / 2).Height(m.height).Render(listView)
-	right := detailStyle.Width(m.width - m.width/2).Height(m.height).Render(detail.String())
+	right := detailStyle.Width(m.width - m.width/2).Height(m.height).Render(detailView)
+	if m.focus == listPane {
+		left = focusedStyle.Render(left)
+	} else {
+		right = focusedStyle.Render(right)
+	}
 	panes := lipgloss.JoinHorizontal(lipgloss.Top, left, right)
 
 	status := fmt.Sprintf("VIEW MODE • %d entries", len(m.hosts.Entries))

memory-bank/activeContext.md

@@ -2,8 +2,8 @@
 
 ## Current Work Focus
 
-**Status**: Phase 2 In Progress - Basic TUI prototype implemented
-**Priority**: Expand Bubble Tea TUI with navigation and view features
+**Status**: Phase 2 Complete - Basic TUI prototype finished
+**Priority**: Begin Phase 3 - Edit mode and file integration
 
 ## Recent Changes
 
@@ -17,6 +17,12 @@
 - ✅ **Comprehensive testing**: 54 comprehensive tests covering all parser functionality (100% passing)
 - ✅ **Demo application**: Full showcase of parser capabilities with real-world examples
 
+### Phase 2: TUI Prototype (COMPLETED) ✅
+- ✅ **Two-pane layout** with list and detail panes
+- ✅ **Navigation system** with pane switching and detail scrolling
+- ✅ **View mode** showing entry details and status bar
+- ✅ **Parser integration** loading `/etc/hosts` into the UI
+
 ### Parser Capabilities Achieved
 - ✅ **Standard entries**: IPv4, IPv6, multiple aliases, inline comments
 - ✅ **Disabled entries**: Commented lines with `# IP hostname` format detection
@@ -35,33 +41,14 @@
 
 ## Next Steps
 
-### Immediate (Phase 2 - Current Priority)
-1. **TUI Architecture Design** ✅
-   - Main Bubble Tea model with list and detail panes
-   - State tracks selection and window size
-
-2. **Two-Pane Layout Implementation** ✅
-   - Left pane: entry list using Bubbles list component
-   - Right pane: detail view of selected entry
-   - Responsive sizing handled in update
-
-3. **Navigation System** 🟡
-   - Basic keyboard navigation via list component
-   - Need scroll handling and pane switching
-
-4. **View Mode Implementation** 🟡
-   - Read-only display of `/etc/hosts` entries
-   - Status bar and active/inactive indicators in list implemented
-   - Further styling improvements pending
-
-### Medium-term (Phase 3)
+### Immediate (Phase 3 - Current Priority)
 1. **Edit Mode Implementation**
    - Explicit mode transition with visual indicators
    - Permission handling with sudo request
    - Entry modification forms with validation
 
 2. **File Integration**
-   - Connect TUI with existing parser functionality
+   - Connect TUI with existing parser functionality for writes
    - Real-time display of actual `/etc/hosts` content
    - Live validation and formatting preview
 

memory-bank/progress.md

@@ -44,13 +44,13 @@
 
 ## What's Left to Build
 
-### 🎨 Basic TUI (Phase 2 - Current Priority)
+### 🎨 Basic TUI (Phase 2 - Completed)
 - [x] **Main Bubble Tea model**: Core application state and structure
 - [x] **Two-pane layout**: Left list + right detail view
 - [x] **Entry list display**: Show IP and hostname columns
 - [x] **Entry selection**: Navigate and select entries with keyboard
 - [x] **View mode**: Safe browsing with status bar and active/inactive indicators
- - [ ] **Integration**: Connect TUI with existing parser functionality
+- [x] **Integration**: Connect TUI with existing parser functionality
 
 ### 🔧 Edit Functionality (Phase 3)
 - [ ] **Edit mode transition**: Explicit mode switching with visual indicators
@@ -74,9 +74,9 @@
 
 ## Current Status
 
-### Project Phase: **Phase 1 Complete → Phase 2 (TUI Implementation)**
-- **Completion**: ~65% (foundation and complete core parser functionality implemented)
-- **Active work**: Ready to implement Bubble Tea TUI with two-pane layout (Phase 2)
+### Project Phase: **Phase 2 Complete → Phase 3 (Edit Mode Implementation)**
+- **Completion**: ~75% (parser and basic TUI implemented)
+- **Active work**: Begin edit mode and file integration (Phase 3)
 - **Blockers**: None - comprehensive parser foundation with 54 tests completed
 - **Parser status**: Production-ready with all safety features implemented
 
@@ -132,10 +132,10 @@
 ## Success Metrics & Milestones
 
 ### Milestone 1: Basic Functionality (Target: Week 1)
-- [ ] Parse and display existing hosts file entries
-- [ ] Navigate entries with keyboard
-- [ ] View entry details in right pane
-- **Success criteria**: Can safely browse hosts file without editing
+- [x] Parse and display existing hosts file entries
+- [x] Navigate entries with keyboard
+- [x] View entry details in right pane
+- **Success criteria**: Can safely browse hosts file without editing (achieved)
 
 ### Milestone 2: Core Editing (Target: Week 2)  
 - [ ] Toggle entries active/inactive
@@ -179,15 +179,14 @@
 19. ✅ **Verify atomic operations** (temp files with rollback for safe writes)
 20. ✅ **Complete parser documentation** (comprehensive demo showing all capabilities)
 
-### 🚧 NEXT Phase 2 Actions (TUI Implementation)
-1. **Design TUI architecture** following Bubble Tea MVU pattern
-2. **Create main application model** with state management
-3. **Implement two-pane layout** (entry list + detail view)
-4. **Add navigation controls** (keyboard-driven interaction)
-5. **Integrate parser functionality** with TUI display
-6. **Implement view mode** (safe browsing without modifications)
+### 🚧 NEXT Phase 3 Actions (Edit Mode & File Integration)
+1. **Edit mode transition** with explicit mode switching
+2. **Permission handling** requesting sudo when entering edit mode
+3. **Entry modification** forms for add/edit/delete/toggle
+4. **File writing** with backups and atomic updates
+5. **Input validation** in real time
 
-**Phase 1 is fully complete with a production-ready parser foundation.**
+**Phase 2 delivered a functional view-only TUI.**
 
 ### Parser Achievement Summary
 - **54 comprehensive tests** covering all hosts file variations and edge cases
@@ -197,4 +196,4 @@
 - **Search and management** capabilities for finding and manipulating entries
 - **Demo application** showcasing all functionality with realistic examples
 
-The foundation is robust, tested, and ready for TUI implementation in Phase 2.
+The foundation is robust, tested, and ready for edit mode implementation in Phase 3.

tests/tui_test.go

@@ -45,3 +45,20 @@ func TestViewModeStatusBar(t *testing.T) {
 	assert.Contains(t, view, "[✓] localhost")
 	assert.Contains(t, view, "[ ] example.com")
 }
+
+func TestPaneSwitching(t *testing.T) {
+	sample := "127.0.0.1 localhost\n192.168.1.10 example.com"
+	lines := strings.Split(sample, "\n")
+	hf, _, err := core.ParseHostsContent(lines)
+	require.NoError(t, err)
+
+	m := tui.NewModel(hf)
+	// Switch focus to detail pane
+	nm, _ := m.Update(tea.KeyMsg{Type: tea.KeyTab})
+	m = nm.(tui.Model)
+
+	// Attempt to move down; selection should remain on first entry
+	nm, _ = m.Update(tea.KeyMsg{Type: tea.KeyDown})
+	m = nm.(tui.Model)
+	assert.Equal(t, "localhost", m.SelectedEntry().Hostname)
+}