Extract renderer-agnostic flamegraph layout

1 files changed, 77 insertions, 0 deletions

diff --git a/internal/flamegraph/layout_test.go b/internal/flamegraph/layout_test.go
new file mode 100644
index 0000000..8fa7398
--- /dev/null
+++ b/internal/flamegraph/layout_test.go
@@ -0,0 +1,77 @@
+package flamegraph
+
+import (
+	"math"
+	"testing"
+)
+
+func almostEqual(a, b float64) bool {
+	return math.Abs(a-b) < 1e-6
+}
+
+func TestBuildFrameLayoutBasicGeometry(t *testing.T) {
+	tr := newTrie()
+	tr.add([]string{"A"}, 4)
+	tr.add([]string{"B"}, 1)
+	tr.computeTotals()
+
+	cfg := defaultSVGConfig()
+	cfg.Width = 100
+	cfg.FrameHeight = 10
+	cfg.FontSize = 10
+	cfg.MinWidthPx = 1
+
+	frames := BuildFrameLayout(tr, cfg)
+	if len(frames) != 2 {
+		t.Fatalf("frames len = %d, want 2", len(frames))
+	}
+
+	a := frames[0]
+	if a.Name != "A" {
+		t.Fatalf("first frame name = %q, want %q", a.Name, "A")
+	}
+	if !almostEqual(a.X, 0) {
+		t.Fatalf("A x = %f, want 0", a.X)
+	}
+	if !almostEqual(a.Width, 80) {
+		t.Fatalf("A width = %f, want 80", a.Width)
+	}
+	if !almostEqual(a.Percent, 80) {
+		t.Fatalf("A percent = %f, want 80", a.Percent)
+	}
+	if a.Depth != 1 {
+		t.Fatalf("A depth = %d, want 1", a.Depth)
+	}
+
+	b := frames[1]
+	if b.Name != "B" {
+		t.Fatalf("second frame name = %q, want %q", b.Name, "B")
+	}
+	if !almostEqual(b.X, 80) {
+		t.Fatalf("B x = %f, want 80", b.X)
+	}
+	if !almostEqual(b.Width, 20) {
+		t.Fatalf("B width = %f, want 20", b.Width)
+	}
+}
+
+func TestBuildFrameLayoutSkipsFramesBelowMinWidth(t *testing.T) {
+	tr := newTrie()
+	tr.add([]string{"A"}, 999)
+	tr.add([]string{"B"}, 1)
+	tr.computeTotals()
+
+	cfg := defaultSVGConfig()
+	cfg.Width = 100
+	cfg.FrameHeight = 10
+	cfg.FontSize = 10
+	cfg.MinWidthPx = 1
+
+	frames := BuildFrameLayout(tr, cfg)
+	if len(frames) != 1 {
+		t.Fatalf("frames len = %d, want 1", len(frames))
+	}
+	if frames[0].Name != "A" {
+		t.Fatalf("remaining frame name = %q, want %q", frames[0].Name, "A")
+	}
+}