tui: add paused stream row selection and highlight

4 files changed, 183 insertions, 18 deletions

diff --git a/internal/tui/eventstream/model.go b/internal/tui/eventstream/model.go
index 0c50d0c..fc423cb 100644
--- a/internal/tui/eventstream/model.go
+++ b/internal/tui/eventstream/model.go
@@ -23,6 +23,7 @@ type Model struct {
 
 	scrollOffset int
 	autoScroll   bool
+	selectedIdx  int
 
 	width  int
 	height int
@@ -33,6 +34,7 @@ func NewModel(source *RingBuffer) Model {
 		source:      source,
 		filterModal: NewFilterModal(),
 		autoScroll:  true,
+		selectedIdx: -1,
 	}
 }
 
@@ -84,7 +86,11 @@ func (m *Model) HandleKey(keyStr string) bool {
 		if !m.paused {
 			// Resuming should return to live-tail behavior immediately.
 			m.autoScroll = true
+			m.selectedIdx = -1
 			m.Refresh()
+		} else {
+			m.ensureSelection()
+			m.centerSelection()
 		}
 		return true
 	case "f", "F":
@@ -93,28 +99,52 @@ func (m *Model) HandleKey(keyStr string) bool {
 		m.filterModal = m.filterModal.Open(m.filter)
 		return true
 	case "G":
-		m.autoScroll = true
-		m.scrollOffset = m.maxScrollOffset()
+		if m.paused {
+			m.moveSelectionTo(len(m.filtered) - 1)
+		} else {
+			m.autoScroll = true
+			m.scrollOffset = m.maxScrollOffset()
+		}
 		return true
 	case "g":
-		m.autoScroll = false
-		m.scrollOffset = 0
+		if m.paused {
+			m.moveSelectionTo(0)
+		} else {
+			m.autoScroll = false
+			m.scrollOffset = 0
+		}
 		return true
 	case "c":
 		m.filter = Filter{}
 		m.applyFilter()
 		return true
 	case "j", "down":
-		m.scrollByLines(1)
+		if m.paused {
+			m.moveSelectionBy(1)
+		} else {
+			m.scrollByLines(1)
+		}
 		return true
 	case "k", "up":
-		m.scrollByLines(-1)
+		if m.paused {
+			m.moveSelectionBy(-1)
+		} else {
+			m.scrollByLines(-1)
+		}
 		return true
 	case "pgdown", "pgdn", "pagedown":
-		m.scrollByLines(m.pageStep())
+		if m.paused {
+			m.moveSelectionBy(m.pageStep())
+		} else {
+			m.scrollByLines(m.pageStep())
+		}
 		return true
 	case "pgup", "pageup":
-		m.scrollByLines(-m.pageStep())
+		if m.paused {
+			m.moveSelectionBy(-m.pageStep())
+		} else {
+			m.scrollByLines(-m.pageStep())
+		}
 		return true
 	default:
 		return false
@@ -160,14 +190,21 @@ func (m *Model) View(width, height int) string {
 		end = len(m.filtered)
 	}
 	visible := m.filtered[start:end]
+	selectedVisibleIdx := -1
+	if m.paused && m.selectedIdx >= start && m.selectedIdx < end {
+		selectedVisibleIdx = m.selectedIdx - start
+	}
 
 	bufferLen := 0
 	if m.source != nil {
 		bufferLen = m.source.Len()
 	}
 
-	base := RenderStreamTable(width, m.paused, len(m.allEvents), len(m.filtered), bufferLen, ringBufferCapacity, m.filter, visible)
+	base := RenderStreamTable(width, m.paused, len(m.allEvents), len(m.filtered), bufferLen, ringBufferCapacity, m.filter, visible, selectedVisibleIdx)
 	status := fmt.Sprintf("Row %d/%d | space:pause f:filter G:tail g:top c:clear j/k:scroll", rowNumber(start, len(m.filtered)), len(m.filtered))
+	if m.paused && m.selectedIdx >= 0 {
+		status = fmt.Sprintf("Row %d/%d | Sel %d/%d | space:pause f:filter G:tail g:top c:clear j/k:select", rowNumber(start, len(m.filtered)), len(m.filtered), rowNumber(m.selectedIdx, len(m.filtered)), len(m.filtered))
+	}
 	out := base + "\n" + status
 
 	if m.filterModal.Visible() {
@@ -197,6 +234,7 @@ func (m *Model) applyFilter() {
 	if len(m.allEvents) == 0 {
 		m.filtered = []StreamEvent{}
 		m.scrollOffset = 0
+		m.selectedIdx = -1
 		return
 	}
 
@@ -215,6 +253,11 @@ func (m *Model) applyFilter() {
 	} else {
 		m.scrollOffset = clamp(m.scrollOffset, 0, max)
 	}
+	m.clampSelection()
+	if m.paused {
+		m.ensureSelection()
+		m.centerSelection()
+	}
 }
 
 func (m *Model) maxScrollOffset() int {
@@ -264,6 +307,57 @@ func (m *Model) scrollByLines(delta int) {
 	}
 }
 
+func (m *Model) moveSelectionBy(delta int) {
+	if len(m.filtered) == 0 {
+		m.selectedIdx = -1
+		return
+	}
+	m.ensureSelection()
+	m.moveSelectionTo(m.selectedIdx + delta)
+}
+
+func (m *Model) moveSelectionTo(idx int) {
+	if len(m.filtered) == 0 {
+		m.selectedIdx = -1
+		return
+	}
+	m.selectedIdx = clamp(idx, 0, len(m.filtered)-1)
+	m.centerSelection()
+}
+
+func (m *Model) centerSelection() {
+	if len(m.filtered) == 0 || m.selectedIdx < 0 {
+		return
+	}
+	m.autoScroll = false
+	mid := m.visibleRows() / 2
+	target := m.selectedIdx - mid
+	m.scrollOffset = clamp(target, 0, m.maxScrollOffset())
+}
+
+func (m *Model) ensureSelection() {
+	if len(m.filtered) == 0 {
+		m.selectedIdx = -1
+		return
+	}
+	if m.selectedIdx >= 0 && m.selectedIdx < len(m.filtered) {
+		return
+	}
+	mid := m.visibleRows() / 2
+	m.selectedIdx = clamp(m.scrollOffset+mid, 0, len(m.filtered)-1)
+}
+
+func (m *Model) clampSelection() {
+	if len(m.filtered) == 0 {
+		m.selectedIdx = -1
+		return
+	}
+	if m.selectedIdx < 0 {
+		return
+	}
+	m.selectedIdx = clamp(m.selectedIdx, 0, len(m.filtered)-1)
+}
+
 func keyMsgFromString(keyStr string) tea.KeyMsg {
 	switch keyStr {
 	case "esc":
diff --git a/internal/tui/eventstream/model_test.go b/internal/tui/eventstream/model_test.go
index bfcbca7..ade1010 100644
--- a/internal/tui/eventstream/model_test.go
+++ b/internal/tui/eventstream/model_test.go
@@ -307,3 +307,64 @@ func TestPausedScrollWithJKAndPageKeys(t *testing.T) {
 		t.Fatalf("expected pgdown to scroll down while paused: afterPgUp=%d afterPgDown=%d", afterPgUp, afterPgDown)
 	}
 }
+
+func TestPausedSelectionInitializesNearMiddleAndCenters(t *testing.T) {
+	rb := NewRingBuffer()
+	m := NewModel(rb)
+	m.height = 20 // visibleRows = 12
+	pushEvents(rb, 100)
+	m.Refresh()
+
+	if !m.HandleKey("space") {
+		t.Fatalf("space should toggle pause")
+	}
+	if !m.paused {
+		t.Fatalf("expected paused state")
+	}
+	if m.selectedIdx < 0 {
+		t.Fatalf("expected selected index while paused")
+	}
+
+	mid := m.visibleRows() / 2
+	wantOffset := clamp(m.selectedIdx-mid, 0, m.maxScrollOffset())
+	if m.scrollOffset != wantOffset {
+		t.Fatalf("expected centered offset %d, got %d", wantOffset, m.scrollOffset)
+	}
+}
+
+func TestPausedSelectionMovesAndRecentersWithJKAndArrows(t *testing.T) {
+	rb := NewRingBuffer()
+	m := NewModel(rb)
+	m.height = 20 // visibleRows = 12
+	pushEvents(rb, 100)
+	m.Refresh()
+
+	if !m.HandleKey("g") {
+		t.Fatalf("g should be handled")
+	}
+	if !m.HandleKey("space") {
+		t.Fatalf("space should toggle pause")
+	}
+	startSel := m.selectedIdx
+
+	if !m.HandleKey("j") {
+		t.Fatalf("j should be handled while paused")
+	}
+	if m.selectedIdx != startSel+1 {
+		t.Fatalf("expected selected index +1 after j, got %d->%d", startSel, m.selectedIdx)
+	}
+	mid := m.visibleRows() / 2
+	if m.scrollOffset != clamp(m.selectedIdx-mid, 0, m.maxScrollOffset()) {
+		t.Fatalf("expected centered viewport after j")
+	}
+
+	if !m.HandleKey("up") {
+		t.Fatalf("up should be handled while paused")
+	}
+	if m.selectedIdx != startSel {
+		t.Fatalf("expected selected index back to start after up, got %d", m.selectedIdx)
+	}
+	if m.scrollOffset != clamp(m.selectedIdx-mid, 0, m.maxScrollOffset()) {
+		t.Fatalf("expected centered viewport after up")
+	}
+}
diff --git a/internal/tui/eventstream/render.go b/internal/tui/eventstream/render.go
index 24864b9..92a70be 100644
--- a/internal/tui/eventstream/render.go
+++ b/internal/tui/eventstream/render.go
@@ -5,6 +5,8 @@ import (
 	"ior/internal/tui/common"
 	"strconv"
 	"strings"
+
+	"github.com/charmbracelet/lipgloss"
 )
 
 type columnLayout struct {
@@ -18,7 +20,12 @@ type columnLayout struct {
 	file    int
 }
 
-func RenderStreamTable(width int, paused bool, totalCount, filteredCount, bufferLen, bufferCap int, filter Filter, events []StreamEvent) string {
+var selectedRowStyle = lipgloss.NewStyle().
+	Bold(true).
+	Foreground(common.ColorBackground).
+	Background(common.ColorPrimary)
+
+func RenderStreamTable(width int, paused bool, totalCount, filteredCount, bufferLen, bufferCap int, filter Filter, events []StreamEvent, selectedVisibleIdx int) string {
 	if width <= 0 {
 		width = 100
 	}
@@ -28,8 +35,8 @@ func RenderStreamTable(width int, paused bool, totalCount, filteredCount, buffer
 	lines = append(lines, renderStatusLine(paused, totalCount, filteredCount, bufferLen, bufferCap))
 	lines = append(lines, renderFilterLine(filter))
 	lines = append(lines, renderColumnHeader(contentWidth))
-	for _, ev := range events {
-		lines = append(lines, renderEventRow(ev, contentWidth))
+	for i, ev := range events {
+		lines = append(lines, renderEventRow(ev, contentWidth, i == selectedVisibleIdx))
 	}
 
 	return common.PanelStyle.Width(contentWidth).Render(strings.Join(lines, "\n"))
@@ -70,7 +77,7 @@ func renderColumnHeader(width int) string {
 	return common.HelpBarStyle.Render(header)
 }
 
-func renderEventRow(ev StreamEvent, width int) string {
+func renderEventRow(ev StreamEvent, width int, selected bool) string {
 	cols := computeColumnLayout(width)
 	pidTid := fmt.Sprintf("%d.%d", ev.PID, ev.TID)
 	row := fmt.Sprintf("%-*s %-*s %-*s %-*s %-*s %-*s %-*s %s",
@@ -83,6 +90,9 @@ func renderEventRow(ev StreamEvent, width int) string {
 		cols.bytes, fitCell(strconv.FormatUint(ev.Bytes, 10), cols.bytes),
 		fitCell(ev.FileName, cols.file),
 	)
+	if selected {
+		return selectedRowStyle.Render(row)
+	}
 	if ev.IsError {
 		return common.ErrorStyle.Render(row)
 	}
diff --git a/internal/tui/eventstream/render_test.go b/internal/tui/eventstream/render_test.go
index 65d7a61..8c2d39a 100644
--- a/internal/tui/eventstream/render_test.go
+++ b/internal/tui/eventstream/render_test.go
@@ -10,7 +10,7 @@ import (
 func TestRenderStatusAndFilterLines(t *testing.T) {
 	events := []StreamEvent{{Syscall: "read", Comm: "nginx", PID: 1, TID: 2, DurationNs: 1200, GapNs: 300, Bytes: 64, FileName: "/tmp/a", RetVal: 64}}
 	f := Filter{Syscall: &StringFilter{Pattern: "read"}, PID: &NumericFilter{Op: OpEq, Value: 1}}
-	out := RenderStreamTable(120, false, 100, 1, 100, 10000, f, events)
+	out := RenderStreamTable(120, false, 100, 1, 100, 10000, f, events, -1)
 
 	for _, want := range []string{"LIVE", "total:100", "filtered:1", "buffer:100/10000", "Filter:", "syscall~read", "pid=1"} {
 		if !strings.Contains(out, want) {
@@ -21,7 +21,7 @@ func TestRenderStatusAndFilterLines(t *testing.T) {
 
 func TestRenderPausedAndErrorRow(t *testing.T) {
 	events := []StreamEvent{{Syscall: "write", Comm: "worker", PID: 1, TID: 2, DurationNs: 1000000, GapNs: 5000, Bytes: 32, FileName: "/tmp/b", RetVal: -1, IsError: true}}
-	out := RenderStreamTable(120, true, 10, 1, 10, 10000, Filter{}, events)
+	out := RenderStreamTable(120, true, 10, 1, 10, 10000, Filter{}, events, -1)
 
 	if !strings.Contains(out, "PAUSED") {
 		t.Fatalf("expected PAUSED indicator\n%s", out)
@@ -46,7 +46,7 @@ func TestRenderHeaderAndTruncate(t *testing.T) {
 		FileName:   "/very/long/path/that/should/be/truncated/for/narrow/views/file.log",
 		RetVal:     1,
 	}}
-	out := RenderStreamTable(80, false, 1, 1, 1, 10000, Filter{}, events)
+	out := RenderStreamTable(80, false, 1, 1, 1, 10000, Filter{}, events, -1)
 
 	for _, col := range []string{"Gap", "Latency", "Comm", "PID.TID", "Syscall", "Ret", "Bytes", "File"} {
 		if !strings.Contains(out, col) {
@@ -87,7 +87,7 @@ func TestRenderEventRowIsSingleLineWithControlCharsAndLongValues(t *testing.T) {
 		RetVal:     -9223372036854775808,
 	}
 
-	row := renderEventRow(ev, 80)
+	row := renderEventRow(ev, 80, false)
 	if strings.Contains(row, "\n") || strings.Contains(row, "\r") || strings.Contains(row, "\t") {
 		t.Fatalf("expected a sanitized single-line row, got %q", row)
 	}
@@ -116,7 +116,7 @@ func TestRenderStreamTableFitsRequestedWidth(t *testing.T) {
 			FileName:   "/very/long/path/that/should/be/truncated/for/narrow/views/file.log",
 			RetVal:     1,
 		},
-	})
+	}, -1)
 
 	for _, line := range strings.Split(out, "\n") {
 		if lipgloss.Width(line) > 80 {