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(),
	))
}