task 359: add flamegraph zoom interactions

4 files changed, 204 insertions, 10 deletions

diff --git a/internal/tui/flamegraph/model.go b/internal/tui/flamegraph/model.go
index 8c8d434..c4ca94a 100644
--- a/internal/tui/flamegraph/model.go
+++ b/internal/tui/flamegraph/model.go
@@ -20,8 +20,8 @@ type snapshotNode struct {
 }
 
 type zoomState struct {
-	path        string
-	selectedIdx int
+	path                string
+	previousSelectedIdx int
 }
 
 type frameSpring struct{}
@@ -31,6 +31,9 @@ type flameKeyMap struct {
 	MoveDeeper    key.Binding
 	PrevSibling   key.Binding
 	NextSibling   key.Binding
+	ZoomIn        key.Binding
+	ZoomUndo      key.Binding
+	ZoomReset     key.Binding
 }
 
 func defaultFlameKeyMap() flameKeyMap {
@@ -39,6 +42,9 @@ func defaultFlameKeyMap() flameKeyMap {
 		MoveDeeper:    key.NewBinding(key.WithKeys("k", "up")),
 		PrevSibling:   key.NewBinding(key.WithKeys("h", "left")),
 		NextSibling:   key.NewBinding(key.WithKeys("l", "right")),
+		ZoomIn:        key.NewBinding(key.WithKeys("enter")),
+		ZoomUndo:      key.NewBinding(key.WithKeys("backspace", "u")),
+		ZoomReset:     key.NewBinding(key.WithKeys("esc")),
 	}
 }
 
@@ -56,6 +62,7 @@ type Model struct {
 	selectedIdx int
 	zoomStack   []zoomState
 	zoomRoot    *snapshotNode
+	zoomPath    string
 
 	searchActive bool
 	searchQuery  string
@@ -111,6 +118,12 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	case tea.KeyPressMsg:
 		prev := m.selectedIdx
 		switch {
+		case key.Matches(msg, m.keys.ZoomIn):
+			m.zoomIn()
+		case key.Matches(msg, m.keys.ZoomUndo):
+			m.zoomUndo()
+		case key.Matches(msg, m.keys.ZoomReset):
+			m.zoomReset()
 		case key.Matches(msg, m.keys.MoveShallower):
 			m.moveVertical(-1)
 		case key.Matches(msg, m.keys.MoveDeeper):
@@ -144,6 +157,9 @@ func (m *Model) SetLiveTrie(liveTrie *coreflamegraph.LiveTrie) {
 	m.selectedIdx = 0
 	m.frames = nil
 	m.targetFrames = nil
+	m.zoomStack = nil
+	m.zoomRoot = nil
+	m.zoomPath = ""
 	m.subtreeSet = make(map[int]bool)
 }
 
@@ -162,11 +178,13 @@ func (m *Model) RefreshFromLiveTrie() bool {
 	if err := json.Unmarshal(payload, &snapshot); err != nil {
 		return false
 	}
-	m.targetFrames = BuildTerminalLayout(&snapshot, m.width, m.height)
-	m.frames = append(m.frames[:0], m.targetFrames...)
-	m.clampSelection()
-	m.subtreeSet = computeSubtreeSet(m.frames, m.selectedIdx)
 	m.snapshot = &snapshot
+	if m.zoomPath != "" {
+		m.zoomRoot = findNodeByPath(m.snapshot, m.zoomPath)
+	} else {
+		m.zoomRoot = nil
+	}
+	m.rebuildFrames()
 	m.lastVersion = version
 	return true
 }
@@ -180,10 +198,7 @@ func (m Model) LastVersion() uint64 {
 func (m *Model) SetViewport(width, height int) {
 	m.width = width
 	m.height = height
-	m.targetFrames = BuildTerminalLayout(m.snapshot, width, height)
-	m.frames = append(m.frames[:0], m.targetFrames...)
-	m.clampSelection()
-	m.subtreeSet = computeSubtreeSet(m.frames, m.selectedIdx)
+	m.rebuildFrames()
 }
 
 // SetDarkMode sets the active color theme mode.
@@ -191,6 +206,67 @@ func (m *Model) SetDarkMode(isDark bool) {
 	m.isDark = isDark
 }
 
+func (m *Model) rebuildFrames() {
+	var root *snapshotNode
+	rootPath := ""
+	if m.zoomRoot != nil {
+		root = m.zoomRoot
+		rootPath = m.zoomPath
+	} else {
+		root = m.snapshot
+	}
+	m.targetFrames = buildTerminalLayoutWithPath(root, m.width, m.height, rootPath)
+	m.frames = append(m.frames[:0], m.targetFrames...)
+	m.clampSelection()
+	m.subtreeSet = computeSubtreeSet(m.frames, m.selectedIdx)
+}
+
+func (m *Model) zoomIn() {
+	if len(m.frames) == 0 || m.snapshot == nil {
+		return
+	}
+	m.clampSelection()
+	selectedPath := m.frames[m.selectedIdx].Path
+	target := findNodeByPath(m.snapshot, selectedPath)
+	if target == nil {
+		return
+	}
+	m.zoomStack = append(m.zoomStack, zoomState{
+		path:                m.zoomPath,
+		previousSelectedIdx: m.selectedIdx,
+	})
+	m.zoomRoot = target
+	m.zoomPath = selectedPath
+	m.selectedIdx = 0
+	m.rebuildFrames()
+}
+
+func (m *Model) zoomUndo() {
+	if len(m.zoomStack) == 0 || m.snapshot == nil {
+		return
+	}
+	last := m.zoomStack[len(m.zoomStack)-1]
+	m.zoomStack = m.zoomStack[:len(m.zoomStack)-1]
+	m.zoomPath = last.path
+	if m.zoomPath == "" {
+		m.zoomRoot = nil
+	} else {
+		m.zoomRoot = findNodeByPath(m.snapshot, m.zoomPath)
+	}
+	m.selectedIdx = last.previousSelectedIdx
+	m.rebuildFrames()
+}
+
+func (m *Model) zoomReset() {
+	if m.zoomRoot == nil && len(m.zoomStack) == 0 {
+		return
+	}
+	m.zoomRoot = nil
+	m.zoomPath = ""
+	m.zoomStack = nil
+	m.rebuildFrames()
+}
+
 func (m *Model) moveVertical(delta int) {
 	if len(m.frames) == 0 {
 		return
diff --git a/internal/tui/flamegraph/model_test.go b/internal/tui/flamegraph/model_test.go
index 4569296..f79b095 100644
--- a/internal/tui/flamegraph/model_test.go
+++ b/internal/tui/flamegraph/model_test.go
@@ -126,6 +126,78 @@ func TestKeyboardNavigationSingleNodeClamped(t *testing.T) {
 	}
 }
 
+func TestZoomInUndoResetAndNestedZoom(t *testing.T) {
+	m := newZoomModel()
+
+	m.selectedIdx = mustFrameIndex(t, m.frames, "root"+pathSeparator+"A")
+	m = pressFlameKey(t, m, tea.KeyPressMsg{Code: tea.KeyEnter})
+	if got, want := m.zoomPath, "root"+pathSeparator+"A"; got != want {
+		t.Fatalf("expected zoomPath %q, got %q", want, got)
+	}
+	if len(m.zoomStack) != 1 || m.zoomStack[0].path != "" {
+		t.Fatalf("expected one zoom stack entry from root, got %#v", m.zoomStack)
+	}
+	if m.zoomRoot == nil || m.zoomRoot.Name != "A" {
+		t.Fatalf("expected zoomRoot A, got %+v", m.zoomRoot)
+	}
+
+	m.selectedIdx = mustFrameIndex(t, m.frames, "root"+pathSeparator+"A"+pathSeparator+"A1")
+	m = pressFlameKey(t, m, tea.KeyPressMsg{Code: tea.KeyEnter})
+	if got, want := m.zoomPath, "root"+pathSeparator+"A"+pathSeparator+"A1"; got != want {
+		t.Fatalf("expected nested zoomPath %q, got %q", want, got)
+	}
+	if len(m.zoomStack) != 2 || m.zoomStack[1].path != "root"+pathSeparator+"A" {
+		t.Fatalf("expected nested zoom stack to preserve parent path, got %#v", m.zoomStack)
+	}
+
+	m = pressFlameKey(t, m, tea.KeyPressMsg{Code: tea.KeyBackspace})
+	if got, want := m.zoomPath, "root"+pathSeparator+"A"; got != want {
+		t.Fatalf("expected zoomPath after undo %q, got %q", want, got)
+	}
+	if len(m.zoomStack) != 1 {
+		t.Fatalf("expected one stack entry after undo, got %d", len(m.zoomStack))
+	}
+
+	m = pressFlameKey(t, m, tea.KeyPressMsg{Code: tea.KeyEsc})
+	if m.zoomPath != "" || m.zoomRoot != nil || len(m.zoomStack) != 0 {
+		t.Fatalf("expected zoom reset to root state, got path=%q root=%+v stack=%d", m.zoomPath, m.zoomRoot, len(m.zoomStack))
+	}
+}
+
+func newZoomModel() Model {
+	m := NewModel(nil)
+	m.width = 120
+	m.height = 30
+	m.snapshot = &snapshotNode{
+		Name:  "root",
+		Total: 100,
+		Children: []*snapshotNode{
+			{
+				Name:  "A",
+				Total: 60,
+				Children: []*snapshotNode{
+					{Name: "A1", Total: 30},
+					{Name: "A2", Total: 30},
+				},
+			},
+			{Name: "B", Total: 40},
+		},
+	}
+	m.rebuildFrames()
+	return m
+}
+
+func mustFrameIndex(t *testing.T, frames []tuiFrame, path string) int {
+	t.Helper()
+	for idx, frame := range frames {
+		if frame.Path == path {
+			return idx
+		}
+	}
+	t.Fatalf("frame path %q not found", path)
+	return -1
+}
+
 func pressFlameKey(t *testing.T, m Model, keyMsg tea.KeyPressMsg) Model {
 	t.Helper()
 	next, _ := m.Update(keyMsg)
diff --git a/internal/tui/flamegraph/renderer.go b/internal/tui/flamegraph/renderer.go
index 8b2aff0..5e223a6 100644
--- a/internal/tui/flamegraph/renderer.go
+++ b/internal/tui/flamegraph/renderer.go
@@ -18,6 +18,10 @@ const minFlameWidth = 60
 
 // BuildTerminalLayout converts a live trie snapshot into terminal frame cells.
 func BuildTerminalLayout(snapshot *snapshotNode, width, height int) []tuiFrame {
+	return buildTerminalLayoutWithPath(snapshot, width, height, "")
+}
+
+func buildTerminalLayoutWithPath(snapshot *snapshotNode, width, height int, rootPath string) []tuiFrame {
 	if snapshot == nil || width <= 0 || height <= 0 {
 		return nil
 	}
@@ -27,6 +31,9 @@ func BuildTerminalLayout(snapshot *snapshotNode, width, height int) []tuiFrame {
 	}
 
 	rootName := frameName(snapshot.Name, 0)
+	if rootPath != "" {
+		rootName = rootPath
+	}
 	frames := make([]tuiFrame, 0, len(snapshot.Children)+1)
 	collectTerminalLayout(&frames, snapshot, rootTotal, width, height, 0, 0, rootName)
 	return frames
diff --git a/internal/tui/flamegraph/zoom.go b/internal/tui/flamegraph/zoom.go
new file mode 100644
index 0000000..7a3aa42
--- /dev/null
+++ b/internal/tui/flamegraph/zoom.go
@@ -0,0 +1,39 @@
+package flamegraph
+
+import "strings"
+
+func findNodeByPath(root *snapshotNode, path string) *snapshotNode {
+	if root == nil {
+		return nil
+	}
+	if path == "" {
+		return root
+	}
+	parts := strings.Split(path, pathSeparator)
+	if len(parts) == 0 {
+		return root
+	}
+	rootName := frameName(root.Name, 0)
+	if parts[0] == rootName {
+		parts = parts[1:]
+	}
+
+	node := root
+	for _, part := range parts {
+		next := findChildByName(node, part)
+		if next == nil {
+			return nil
+		}
+		node = next
+	}
+	return node
+}
+
+func findChildByName(node *snapshotNode, name string) *snapshotNode {
+	for _, child := range node.Children {
+		if child.Name == name || frameName(child.Name, 1) == name {
+			return child
+		}
+	}
+	return nil
+}