tui/dashboard: implement files tab with scrolling

4 files changed, 171 insertions, 4 deletions

diff --git a/internal/tui/dashboard/files.go b/internal/tui/dashboard/files.go
new file mode 100644
index 0000000..c52e887
--- /dev/null
+++ b/internal/tui/dashboard/files.go
@@ -0,0 +1,87 @@
+package dashboard
+
+import (
+	"ior/internal/statsengine"
+	"strconv"
+
+	"github.com/charmbracelet/bubbles/table"
+)
+
+func renderFiles(snap *statsengine.Snapshot, width, height int) string {
+	return renderFilesWithOffset(snap, width, height, 0)
+}
+
+func renderFilesWithOffset(snap *statsengine.Snapshot, width, height, offset int) string {
+	if snap == nil {
+		return "Files: waiting for stats..."
+	}
+
+	rows := fileRows(snap.Files())
+	if len(rows) == 0 {
+		return "Files: no data"
+	}
+
+	columns := []table.Column{
+		{Title: "Path", Width: filePathWidth(width)},
+		{Title: "Accesses", Width: 10},
+		{Title: "Bytes Read", Width: 12},
+		{Title: "Bytes Written", Width: 14},
+		{Title: "Avg Latency", Width: 12},
+		{Title: "Max Latency", Width: 12},
+	}
+
+	tbl := table.New(
+		table.WithColumns(columns),
+		table.WithRows(rows),
+		table.WithFocused(true),
+	)
+	tbl.SetHeight(syscallTableHeight(height))
+	tbl.SetWidth(tableWidth(width))
+	tbl.SetCursor(clampOffset(offset, len(rows)))
+	return tbl.View()
+}
+
+func fileRows(files []statsengine.FileSnapshot) []table.Row {
+	rows := make([]table.Row, 0, len(files))
+	for _, f := range files {
+		rows = append(rows, table.Row{
+			truncatePathMiddle(f.Path, 48),
+			strconv.FormatUint(f.Accesses, 10),
+			formatBytes(float64(f.BytesRead)),
+			formatBytes(float64(f.BytesWritten)),
+			formatDurationNs(f.AvgLatencyNs),
+			formatDurationUintNs(f.MaxLatencyNs),
+		})
+	}
+	return rows
+}
+
+func filePathWidth(width int) int {
+	if width <= 0 {
+		return 48
+	}
+	w := width - 66
+	if w < 20 {
+		return 20
+	}
+	if w > 72 {
+		return 72
+	}
+	return w
+}
+
+func truncatePathMiddle(path string, limit int) string {
+	if len(path) <= limit {
+		return path
+	}
+	if limit <= 3 {
+		return path[:limit]
+	}
+
+	head := (limit - 3) / 2
+	tail := limit - 3 - head
+	if tail <= 0 {
+		return path[:limit]
+	}
+	return path[:head] + "..." + path[len(path)-tail:]
+}
diff --git a/internal/tui/dashboard/files_test.go b/internal/tui/dashboard/files_test.go
new file mode 100644
index 0000000..f889b66
--- /dev/null
+++ b/internal/tui/dashboard/files_test.go
@@ -0,0 +1,51 @@
+package dashboard
+
+import (
+	"strings"
+	"testing"
+
+	"ior/internal/statsengine"
+)
+
+func TestRenderFilesIncludesHeaders(t *testing.T) {
+	snap := statsengine.NewSnapshot(
+		nil,
+		nil,
+		nil,
+		nil,
+		[]statsengine.FileSnapshot{
+			{Path: "/var/log/app.log", Accesses: 42, BytesRead: 4096, BytesWritten: 2048, AvgLatencyNs: 1500, MaxLatencyNs: 20_000},
+		},
+		nil,
+		statsengine.HistogramSnapshot{},
+		statsengine.HistogramSnapshot{},
+	)
+
+	out := renderFiles(&snap, 120, 30)
+	for _, token := range []string{"Path", "Accesses", "Bytes Read", "Bytes Written", "Avg Latency", "Max Latency", "app.log"} {
+		if !strings.Contains(out, token) {
+			t.Fatalf("expected token %q in files table output", token)
+		}
+	}
+}
+
+func TestRenderFilesNoData(t *testing.T) {
+	snap := statsengine.NewSnapshot(nil, nil, nil, nil, nil, nil, statsengine.HistogramSnapshot{}, statsengine.HistogramSnapshot{})
+	if got := renderFiles(&snap, 100, 20); got != "Files: no data" {
+		t.Fatalf("unexpected no-data output: %q", got)
+	}
+}
+
+func TestTruncatePathMiddle(t *testing.T) {
+	longPath := "/very/long/path/with/high/cardinality/segments/and/filename.log"
+	got := truncatePathMiddle(longPath, 24)
+	if len(got) != 24 {
+		t.Fatalf("expected truncated path length 24, got %d (%q)", len(got), got)
+	}
+	if !strings.Contains(got, "...") {
+		t.Fatalf("expected ellipsis in truncated path, got %q", got)
+	}
+	if !strings.HasPrefix(got, "/very") || !strings.HasSuffix(got, "e.log") {
+		t.Fatalf("expected head and tail preservation, got %q", got)
+	}
+}
diff --git a/internal/tui/dashboard/model.go b/internal/tui/dashboard/model.go
index 454e8ab..ae5c60f 100644
--- a/internal/tui/dashboard/model.go
+++ b/internal/tui/dashboard/model.go
@@ -1,7 +1,6 @@
 package dashboard
 
 import (
-	"fmt"
 	"ior/internal/statsengine"
 	"ior/internal/tui"
 	"ior/internal/tui/messages"
@@ -34,6 +33,7 @@ type Model struct {
 	refreshEvery    time.Duration
 	keys            tui.KeyMap
 	syscallsOffset  int
+	filesOffset     int
 	processesOffset int
 }
 
@@ -107,6 +107,18 @@ func (m Model) handleKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			return m, nil
 		}
 	}
+	if m.activeTab == TabFiles {
+		switch msg.String() {
+		case "down", "j":
+			m.filesOffset++
+			return m, nil
+		case "up", "k":
+			if m.filesOffset > 0 {
+				m.filesOffset--
+			}
+			return m, nil
+		}
+	}
 
 	switch {
 	case key.Matches(msg, m.keys.Tab):
@@ -141,7 +153,7 @@ func (m Model) View() string {
 	var b strings.Builder
 	b.WriteString(renderTabBar(m.activeTab, m.width))
 	b.WriteString("\n")
-	b.WriteString(renderActiveTab(m.activeTab, m.latest, m.width, m.height, m.syscallsOffset, m.processesOffset))
+	b.WriteString(renderActiveTab(m.activeTab, m.latest, m.width, m.height, m.syscallsOffset, m.filesOffset, m.processesOffset))
 	b.WriteString("\n")
 	b.WriteString(renderHelpBar(m.keys))
 	return tui.ScreenStyle.Render(b.String())
@@ -151,7 +163,7 @@ func tickCmd(d time.Duration) tea.Cmd {
 	return tea.Tick(d, func(time.Time) tea.Msg { return refreshTickMsg{} })
 }
 
-func renderActiveTab(tab Tab, snap *statsengine.Snapshot, width, height, syscallsOffset, processesOffset int) string {
+func renderActiveTab(tab Tab, snap *statsengine.Snapshot, width, height, syscallsOffset, filesOffset, processesOffset int) string {
 	_ = width
 	_ = height
 
@@ -165,7 +177,7 @@ func renderActiveTab(tab Tab, snap *statsengine.Snapshot, width, height, syscall
 	case TabSyscalls:
 		return renderSyscallsWithOffset(snap, width, height, syscallsOffset)
 	case TabFiles:
-		return tui.PanelStyle.Render(fmt.Sprintf("Files: %d rows", len(snap.Files())))
+		return renderFilesWithOffset(snap, width, height, filesOffset)
 	case TabProcesses:
 		return renderProcessesWithOffset(snap, width, height, processesOffset)
 	case TabLatency:
diff --git a/internal/tui/dashboard/model_test.go b/internal/tui/dashboard/model_test.go
index 3d93659..1d2329d 100644
--- a/internal/tui/dashboard/model_test.go
+++ b/internal/tui/dashboard/model_test.go
@@ -77,6 +77,23 @@ func TestProcessesTabScrollsWithJK(t *testing.T) {
 	}
 }
 
+func TestFilesTabScrollsWithJK(t *testing.T) {
+	m := NewModelWithConfig(nil, 250, tui.DefaultKeyMap())
+	m.activeTab = TabFiles
+
+	next, _ := m.Update(tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{'j'}})
+	model := next.(Model)
+	if model.filesOffset != 1 {
+		t.Fatalf("expected files offset 1 after j, got %d", model.filesOffset)
+	}
+
+	next, _ = model.Update(tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{'k'}})
+	model = next.(Model)
+	if model.filesOffset != 0 {
+		t.Fatalf("expected files offset 0 after k, got %d", model.filesOffset)
+	}
+}
+
 func TestRefreshTickEmitsStatsTickMsg(t *testing.T) {
 	snap := &statsengine.Snapshot{TotalSyscalls: 9}
 	engine := &fakeSnapshotSource{snap: snap}