Execute PLAN_FRONTEND.md

cmd/frontend/sparkline.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"html/template"
+	"strings"
+
+	pb "git.ipng.ch/ipng/nginx-logtail/proto/logtailpb"
+)
+
+const (
+	svgW   = 300.0
+	svgH   = 60.0
+	svgPad = 4.0
+)
+
+// renderSparkline converts trend points into an inline SVG polyline.
+// Returns "" if there are fewer than 2 points or all counts are zero.
+func renderSparkline(points []*pb.TrendPoint) template.HTML {
+	if len(points) < 2 {
+		return ""
+	}
+
+	var maxCount int64
+	for _, p := range points {
+		if p.Count > maxCount {
+			maxCount = p.Count
+		}
+	}
+	if maxCount == 0 {
+		return ""
+	}
+
+	n := len(points)
+	var pts strings.Builder
+	for i, p := range points {
+		x := svgPad + float64(i)*(svgW-2*svgPad)/float64(n-1)
+		y := svgPad + (svgH-2*svgPad)*(1.0-float64(p.Count)/float64(maxCount))
+		if i > 0 {
+			pts.WriteByte(' ')
+		}
+		fmt.Fprintf(&pts, "%.1f,%.1f", x, y)
+	}
+
+	return template.HTML(fmt.Sprintf(
+		`<svg viewBox="0 0 %d %d" width="%d" height="%d" xmlns="http://www.w3.org/2000/svg">`+
+			`<polyline points="%s" fill="none" stroke="#4a90d9" stroke-width="1.5" stroke-linejoin="round"/>`+
+			`</svg>`,
+		int(svgW), int(svgH), int(svgW), int(svgH), pts.String(),
+	))
+}