feat(tui): add link picker and navigation history

Press [ in detail view to open link picker showing all [[links]]
in the current entry. Enter follows a link, resolving by title
then body substring. Navigation history stack enables esc to pop
back through followed links before returning to list.

Adds Store.ResolveLink() for non-transactional link resolution
from the TUI layer.

internal/tui/commands.go

@@ -59,6 +59,10 @@ type backlinksLoadedMsg struct {
 	backlinks []db.Backlink
 }
 
+type linkFollowedMsg struct {
+	entity *db.Entity
+}
+
 type tagsLoadedMsg struct {
 	tags []db.TagCount
 }
@@ -208,6 +212,16 @@ func loadBacklinks(store *db.Store, entityID string) tea.Cmd {
 	}
 }
 
+func followLink(store *db.Store, linkText string) tea.Cmd {
+	return func() tea.Msg {
+		entity, err := store.ResolveLink(context.Background(), linkText)
+		if err != nil {
+			return errMsg{err}
+		}
+		return linkFollowedMsg{entity}
+	}
+}
+
 func loadRailTags(store *db.Store) tea.Cmd {
 	return func() tea.Msg {
 		tags, err := store.ListTags(context.Background(), false)

internal/tui/help.go

@@ -60,6 +60,8 @@ func renderHelp(width, height int) string {
 			{"!", "toggle pin"},
 			{"r", "run checklist"},
 			{"f", "fill template"},
+			{"[", "follow [[link]]"},
+			{"esc", "back (pops link history)"},
 		}},
 		{"Stumble", [][2]string{
 			{"n / →", "skip to next"},

internal/tui/linkpicker.go

@@ -0,0 +1,65 @@
+package tui
+
+import (
+	"strings"
+
+	"github.com/lerko/nib/internal/link"
+)
+
+type linkPickerModel struct {
+	links  []string
+	cursor int
+}
+
+func newLinkPicker(body string) linkPickerModel {
+	return linkPickerModel{
+		links: link.ExtractLinks(body),
+	}
+}
+
+func (lp linkPickerModel) selected() string {
+	if len(lp.links) == 0 || lp.cursor >= len(lp.links) {
+		return ""
+	}
+	return lp.links[lp.cursor]
+}
+
+func (lp linkPickerModel) update(key string) linkPickerModel {
+	switch key {
+	case "up", "k":
+		if lp.cursor > 0 {
+			lp.cursor--
+		}
+	case "down", "j":
+		if lp.cursor < len(lp.links)-1 {
+			lp.cursor++
+		}
+	}
+	return lp
+}
+
+func (lp linkPickerModel) view(width int) string {
+	var b strings.Builder
+	b.WriteString(titleStyle.Render("follow link") + "\n\n")
+
+	if len(lp.links) == 0 {
+		b.WriteString(hintDescStyle.Render("  no [[links]] in this entry"))
+		b.WriteString("\n\n")
+		b.WriteString(helpStyle.Render("esc:back"))
+		return b.String()
+	}
+
+	for i, lt := range lp.links {
+		label := "[[" + lt + "]]"
+		if i == lp.cursor {
+			b.WriteString(selectedItemStyle.Render(" " + label))
+		} else {
+			b.WriteString(listItemStyle.Render(label))
+		}
+		b.WriteString("\n")
+	}
+
+	b.WriteString("\n")
+	b.WriteString(helpStyle.Render("enter:follow  esc:back"))
+	return b.String()
+}

internal/tui/model.go

@@ -24,6 +24,7 @@ const (
 	statePromote
 	stateAbsorb
 	stateStumble
+	stateLinkPicker
 )
 
 type viewMode int
@@ -90,6 +91,8 @@ type model struct {
 	stumble      stumbleModel
 	showHelp     bool
 	autocomplete autocompleteModel
+	linkPicker   linkPickerModel
+	navStack     []string
 
 	focus       focusPane
 	splitDetail bool
@@ -293,6 +296,11 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		}
 		return m, nil
 
+	case linkFollowedMsg:
+		m.detail.setEntity(msg.entity)
+		m.state = stateDetail
+		return m, loadBacklinks(m.store, msg.entity.ID)
+
 	case tagsLoadedMsg:
 		m.filter.setTags(msg.tags)
 		m.tagRail.setTags(msg.tags)
@@ -346,6 +354,8 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			return m.updateAbsorb(msg)
 		case stateStumble:
 			return m.updateStumble(msg)
+		case stateLinkPicker:
+			return m.updateLinkPicker(msg)
 		default:
 			return m.updateKeys(msg)
 		}
@@ -717,6 +727,19 @@ func (m model) updateBrowse(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 				}
 				return m, nil
 			}
+			if len(m.navStack) > 0 {
+				prevID := m.navStack[len(m.navStack)-1]
+				m.navStack = m.navStack[:len(m.navStack)-1]
+				return m, tea.Batch(
+					func() tea.Msg {
+						e, err := m.store.Get(context.Background(), prevID)
+						if err != nil {
+							return errMsg{err}
+						}
+						return linkFollowedMsg{e}
+					},
+				)
+			}
 			if m.isSplit() {
 				m.state = stateList
 				m.splitDetail = true
@@ -835,6 +858,14 @@ func (m model) updateBrowse(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		}
 		return m, nil
 
+	case "[":
+		if m.state == stateDetail && m.detail.entity != nil && m.detail.mode == detailPreview {
+			m.linkPicker = newLinkPicker(m.detail.entity.Body)
+			m.state = stateLinkPicker
+			return m, nil
+		}
+		return m, nil
+
 	case "r":
 		if m.state == stateDetail && m.detail.entity != nil && m.detail.mode == detailPreview {
 			if m.detail.entity.CardType != nil && *m.detail.entity.CardType == db.CardChecklist {
@@ -927,6 +958,26 @@ func (m model) updateConfirm(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 	return m, nil
 }
 
+func (m model) updateLinkPicker(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
+	switch msg.String() {
+	case "esc", "q":
+		m.state = stateDetail
+		return m, nil
+	case "enter":
+		lt := m.linkPicker.selected()
+		if lt == "" {
+			return m, nil
+		}
+		if m.detail.entity != nil {
+			m.navStack = append(m.navStack, m.detail.entity.ID)
+		}
+		return m, followLink(m.store, lt)
+	default:
+		m.linkPicker = m.linkPicker.update(msg.String())
+		return m, nil
+	}
+}
+
 func (m model) updatePromote(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 	switch msg.String() {
 	case "esc", "q":
@@ -1045,6 +1096,8 @@ func (m model) View() string {
 		content = m.absorb.view(m.width)
 	case stateStumble:
 		content = m.stumble.view()
+	case stateLinkPicker:
+		content = m.linkPicker.view(m.width)
 	}
 
 	header := m.headerView()