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{
-		list:  l,
-		hosts: hf,
-		mode:  ViewMode,
+	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.