From 8361fd22d45e4fbf6b24309aaa1b6d49d9010759 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Tue, 24 Feb 2026 20:20:42 +0200
Subject: flamegraph: add native svg pipeline and tests

---
 internal/flamegraph/nativesvg.go      |  74 +++++++++++++++++++++++
 internal/flamegraph/svgwriter_test.go | 109 ++++++++++++++++++++++++++++++++++
 2 files changed, 183 insertions(+)
 create mode 100644 internal/flamegraph/nativesvg.go
 create mode 100644 internal/flamegraph/svgwriter_test.go

(limited to 'internal/flamegraph')

diff --git a/internal/flamegraph/nativesvg.go b/internal/flamegraph/nativesvg.go
new file mode 100644
index 0000000..2c76a7d
--- /dev/null
+++ b/internal/flamegraph/nativesvg.go
@@ -0,0 +1,74 @@
+package flamegraph
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"iter"
+)
+
+type NativeSVG struct {
+	fields     []string
+	countField string
+	config     SVGConfig
+}
+
+func NewNativeSVG(fields []string, countField string) NativeSVG {
+	return NativeSVG{
+		fields:     fields,
+		countField: countField,
+		config:     defaultSVGConfig(),
+	}
+}
+
+func (n NativeSVG) WriteSVGFromFile(iorDataFile string) error {
+	outFile := fmt.Sprintf("%s.%s-by-%s.svg",
+		strings.TrimSuffix(iorDataFile, ".ior.zst"),
+		strings.Join(n.fields, ":"),
+		n.countField,
+	)
+
+	iod, err := newIorDataFromFile(iorDataFile)
+	if err != nil {
+		return fmt.Errorf("read ior data: %w", err)
+	}
+
+	fd, err := os.Create(outFile)
+	if err != nil {
+		return fmt.Errorf("create output %s: %w", outFile, err)
+	}
+	defer fd.Close()
+
+	return n.WriteSVGFromIter(iod.iter(), fd)
+}
+
+func (n NativeSVG) WriteSVGFromIter(records iter.Seq[IterRecord], w io.Writer) error {
+	tr := newTrie()
+	for record := range records {
+		frames, err := n.recordFrames(record)
+		if err != nil {
+			return err
+		}
+		tr.add(frames, record.Cnt.ValueByName(n.countField))
+	}
+	tr.computeTotals()
+	return WriteSVG(w, tr, n.config)
+}
+
+func (n NativeSVG) recordFrames(record IterRecord) ([]string, error) {
+	var frames []string
+	for _, fieldName := range n.fields {
+		value, err := record.StringByName(fieldName)
+		if err != nil {
+			return nil, fmt.Errorf("field %s: %w", fieldName, err)
+		}
+		for _, part := range strings.Split(value, ";") {
+			if part != "" {
+				frames = append(frames, part)
+			}
+		}
+	}
+	return frames, nil
+}
diff --git a/internal/flamegraph/svgwriter_test.go b/internal/flamegraph/svgwriter_test.go
new file mode 100644
index 0000000..6fdbe3d
--- /dev/null
+++ b/internal/flamegraph/svgwriter_test.go
@@ -0,0 +1,109 @@
+package flamegraph
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func renderSVGForTest(t *testing.T, tr *trie, cfg SVGConfig) string {
+	t.Helper()
+	var buf bytes.Buffer
+	if err := WriteSVG(&buf, tr, cfg); err != nil {
+		t.Fatalf("WriteSVG failed: %v", err)
+	}
+	return buf.String()
+}
+
+func TestWriteSVGBasic(t *testing.T) {
+	tr := newTrie()
+	tr.add([]string{"a", "b"}, 3)
+	tr.add([]string{"a", "c"}, 2)
+	tr.computeTotals()
+
+	svg := renderSVGForTest(t, tr, defaultSVGConfig())
+	if !strings.Contains(svg, "<svg") || !strings.Contains(svg, "</svg>") {
+		t.Fatalf("expected valid svg wrapper, got: %s", svg)
+	}
+	if !strings.Contains(svg, "data-name=\"a\"") || !strings.Contains(svg, "data-name=\"b\"") {
+		t.Fatalf("expected rendered frame names, got: %s", svg)
+	}
+}
+
+func TestWriteSVGEmptyTrie(t *testing.T) {
+	tr := newTrie()
+	tr.computeTotals()
+
+	svg := renderSVGForTest(t, tr, defaultSVGConfig())
+	if !strings.Contains(svg, "<svg") || !strings.Contains(svg, "</svg>") {
+		t.Fatalf("expected valid svg wrapper, got: %s", svg)
+	}
+	if strings.Contains(svg, "class=\"frame\"") {
+		t.Fatalf("expected no rendered frames for empty trie, got: %s", svg)
+	}
+}
+
+func TestWriteSVGMinWidth(t *testing.T) {
+	tr := newTrie()
+	tr.add([]string{"wide"}, 100)
+	tr.add([]string{"tiny"}, 1)
+	tr.computeTotals()
+
+	cfg := defaultSVGConfig()
+	cfg.Width = 120
+	cfg.MinWidthPx = 2.0
+	svg := renderSVGForTest(t, tr, cfg)
+
+	if !strings.Contains(svg, "data-name=\"wide\"") {
+		t.Fatalf("expected wide frame to be rendered, got: %s", svg)
+	}
+	if strings.Contains(svg, "data-name=\"tiny\"") {
+		t.Fatalf("expected tiny frame to be skipped by min width, got: %s", svg)
+	}
+}
+
+func TestWriteSVGTitle(t *testing.T) {
+	tr := newTrie()
+	tr.add([]string{"a"}, 1)
+	tr.computeTotals()
+
+	cfg := defaultSVGConfig()
+	cfg.Title = "Custom Flamegraph"
+	svg := renderSVGForTest(t, tr, cfg)
+
+	if !strings.Contains(svg, "Custom Flamegraph") {
+		t.Fatalf("expected custom title in output, got: %s", svg)
+	}
+}
+
+func TestFrameColor(t *testing.T) {
+	colorA1 := frameColor("read")
+	colorA2 := frameColor("read")
+	colorB := frameColor("write")
+
+	if colorA1 != colorA2 {
+		t.Fatalf("expected deterministic color for identical names, got %q vs %q", colorA1, colorA2)
+	}
+	if !strings.HasPrefix(colorA1, "rgb(") || !strings.HasSuffix(colorA1, ")") {
+		t.Fatalf("expected rgb() format, got %q", colorA1)
+	}
+	if colorA1 == colorB {
+		t.Fatalf("expected different colors for different names, got %q", colorA1)
+	}
+}
+
+func TestWriteSVGInvalidConfigFallsBack(t *testing.T) {
+	tr := newTrie()
+	tr.add([]string{"a"}, 1)
+	tr.computeTotals()
+
+	cfg := SVGConfig{Title: "x", Width: 0, FrameHeight: 0, FontSize: 0, MinWidthPx: 0}
+	svg := renderSVGForTest(t, tr, cfg)
+
+	if !strings.Contains(svg, `width="1200"`) {
+		t.Fatalf("expected fallback width, got: %s", svg)
+	}
+	if !strings.Contains(svg, "I/O Flame Graph") {
+		t.Fatalf("expected fallback title, got: %s", svg)
+	}
+}
-- 
cgit v1.2.3