feat: add motd-assist TUI for managing dynamic MOTDs

Initial Go project built with Bubble Tea and Lip Gloss:
- Live preview and management of /etc/update-motd.d scripts
- Embedded presets (ubuntu-default, minimal, server-dashboard)
- Bundled POSIX sh style scripts (brand header, sysinfo panel, footer)
- Snapshot/restore safety around applying changes
- CLI subcommands preview, apply, restore, list-presets
- Unit tests for detect, sanitize, and apply logic

internal/ui/update.go

@@ -0,0 +1,255 @@
+package ui
+
+import (
+	"strings"
+
+	"github.com/charmbracelet/bubbles/spinner"
+	"github.com/charmbracelet/bubbles/textinput"
+	tea "github.com/charmbracelet/bubbletea"
+
+	"motd-assist/internal/motd"
+	"motd-assist/internal/preset"
+)
+
+// Update behandelt Fenstergröße, Ergebnisse der Hintergrundkommandos und
+// Tastendrücke.
+func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	switch msg := msg.(type) {
+	case tea.WindowSizeMsg:
+		m.width, m.height = msg.Width, msg.Height
+		m.ready = true
+		if w := m.width - 20; w > 10 {
+			m.input.Width = w
+		}
+		if len(m.working) > 0 {
+			return m, m.previewCmd() // Breite geändert → Preview neu rendern
+		}
+		return m, nil
+
+	case spinner.TickMsg:
+		var cmd tea.Cmd
+		m.spinner, cmd = m.spinner.Update(msg)
+		return m, cmd
+
+	case discoverMsg:
+		if msg.err != nil {
+			m.err = msg.err
+			m.current, m.working = nil, nil
+			return m, nil
+		}
+		m.err = nil
+		m.current = msg.scripts
+		m.host = msg.host
+		m.working = rowsFromCurrent(msg.scripts)
+		if m.cursor >= len(m.working) {
+			m.cursor = max(0, len(m.working)-1)
+		}
+		m.refreshPresetMatches()
+		m.previewOff = 0
+		return m, m.previewCmd()
+
+	case presetsMsg:
+		if msg.err == nil {
+			m.presets = msg.presets
+			if m.presetIdx >= len(m.presets) {
+				m.presetIdx = max(0, len(m.presets)-1)
+			}
+			m.refreshPresetMatches()
+		}
+		return m, nil
+
+	case previewMsg:
+		if msg.version < m.previewVersion {
+			return m, nil // veraltetes Ergebnis, neuere Preview läuft schon
+		}
+		m.previewBusy = false
+		m.preview = msg.text
+		m.previewOff = 0
+		return m, nil
+
+	case applyDoneMsg:
+		m.applying = false
+		if msg.err != nil {
+			m.status = "Anwenden fehlgeschlagen: " + msg.err.Error()
+		} else {
+			m.status = "Angewendet: " + m.lastSummary
+		}
+		return m, discoverCmd(m.root)
+
+	case tea.KeyMsg:
+		return m.handleKey(msg)
+	}
+	return m, nil
+}
+
+func (m Model) handleKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch m.mode {
+	case modeHelp:
+		m.mode = modeNormal
+		return m, nil
+
+	case modeSaveName:
+		switch msg.String() {
+		case "enter":
+			name := strings.TrimSpace(m.input.Value())
+			m.mode = modeNormal
+			m.input.Blur()
+			if name == "" {
+				return m, nil
+			}
+			if _, err := preset.SaveUser(m.presetFromWorking(name)); err != nil {
+				m.status = "Speichern fehlgeschlagen: " + err.Error()
+			} else {
+				m.status = "Preset \"" + name + "\" gespeichert"
+			}
+			return m, presetsCmd()
+		case "esc", "ctrl+c":
+			m.mode = modeNormal
+			m.input.Blur()
+			return m, nil
+		}
+		var cmd tea.Cmd
+		m.input, cmd = m.input.Update(msg)
+		return m, cmd
+	}
+
+	key := msg.String()
+	switch key {
+	case "q", "ctrl+c":
+		return m, tea.Quit
+	case "tab":
+		m.focus = (m.focus + 1) % 3
+		return m, nil
+	case "shift+tab":
+		m.focus = (m.focus + 2) % 3
+	case "?":
+		m.mode = modeHelp
+		return m, nil
+	case "r":
+		m.status = ""
+		return m, discoverCmd(m.root)
+	case "esc":
+		if m.err != nil {
+			return m, tea.Quit
+		}
+		m.working = rowsFromCurrent(m.current)
+		m.previewOff = 0
+		m.status = "Änderungen verworfen"
+		return m, m.previewCmd()
+	case "s":
+		if m.err != nil {
+			return m, nil
+		}
+		m.mode = modeSaveName
+		m.input.SetValue("")
+		m.input.Focus()
+		return m, textinput.Blink
+	case "a":
+		return m.applyWorking()
+	case "D":
+		if len(m.presets) == 0 {
+			return m, nil
+		}
+		p := m.presets[m.presetIdx]
+		if err := preset.DeleteUser(p.Name); err != nil {
+			m.status = err.Error()
+		} else {
+			m.status = "Preset \"" + p.Name + "\" gelöscht"
+		}
+		return m, presetsCmd()
+	}
+
+	switch m.focus {
+	case panePresets:
+		switch key {
+		case "j", "down":
+			if m.presetIdx < len(m.presets)-1 {
+				m.presetIdx++
+			}
+		case "k", "up":
+			if m.presetIdx > 0 {
+				m.presetIdx--
+			}
+		case "enter", " ":
+			return m.loadPreset()
+		}
+
+	case paneScripts:
+		switch key {
+		case "j", "down":
+			if m.cursor < len(m.working)-1 {
+				m.cursor++
+			}
+		case "k", "up":
+			if m.cursor > 0 {
+				m.cursor--
+			}
+		case " ":
+			if len(m.working) == 0 {
+				return m, nil
+			}
+			r := &m.working[m.cursor]
+			if r.Remove {
+				return m, nil
+			}
+			r.Enabled = !r.Enabled
+			return m, m.previewCmd()
+		case "u":
+			return m.moveRow(-1)
+		case "d":
+			return m.moveRow(1)
+		}
+
+	case panePreview:
+		lines := strings.Count(m.preview, "\n") + 1
+		switch key {
+		case "j", "down":
+			m.previewOff = min(m.previewOff+1, max(0, lines-1))
+		case "k", "up":
+			if m.previewOff > 0 {
+				m.previewOff--
+			}
+		}
+	}
+	return m, nil
+}
+
+func (m Model) loadPreset() (tea.Model, tea.Cmd) {
+	if len(m.presets) == 0 {
+		return m, nil
+	}
+	p := m.presets[m.presetIdx]
+	entries := make([]motd.DesiredEntry, 0, len(p.Scripts))
+	for _, e := range p.Scripts {
+		entries = append(entries, motd.DesiredEntry{Name: e.Name, Enabled: e.Enabled, Install: e.Install})
+	}
+	m.working = rowsFromDesired(motd.DesiredFromPreset(m.current, entries), m.current)
+	m.cursor = 0
+	m.previewOff = 0
+	m.status = "Preset \"" + p.Name + "\" geladen – mit 'a' anwenden"
+	return m, m.previewCmd()
+}
+
+func (m Model) moveRow(delta int) (tea.Model, tea.Cmd) {
+	i, j := m.cursor, m.cursor+delta
+	if i < 0 || i >= len(m.working) || j < 0 || j >= len(m.working) {
+		return m, nil
+	}
+	m.working[i], m.working[j] = m.working[j], m.working[i]
+	m.cursor = j
+	return m, m.previewCmd()
+}
+
+func (m Model) applyWorking() (tea.Model, tea.Cmd) {
+	if m.applying || m.err != nil {
+		return m, nil
+	}
+	plan := m.currentPlan()
+	if plan.Empty() {
+		m.status = "Keine Änderungen zum Anwenden"
+		return m, nil
+	}
+	m.applying = true
+	m.lastSummary = plan.Summary()
+	return m, applyExec(plan)
+}