package controller

import (
	"bytes"
	"strings"

	"golang.org/x/net/html"
)

// Artwork scripts run only inside an opaque-origin sandbox. CSP blocks network
// access; navigation, forms, and embedded documents are removed here.
func sanitizeDetectionHTML(source string) string {
	root, err := html.Parse(strings.NewReader(source))
	if err != nil {
		return ""
	}
	var walk func(*html.Node)
	walk = func(n *html.Node) {
		for child := n.FirstChild; child != nil; {
			next := child.NextSibling
			switch strings.ToLower(child.Data) {
			case "iframe", "frame", "frameset", "object", "embed", "base", "meta", "link", "form", "input", "textarea", "select", "audio", "video", "source", "foreignobject":
				if child.Type == html.ElementNode {
					n.RemoveChild(child)
					child = next
					continue
				}
			}
			if child.Type == html.ElementNode {
				attrs := child.Attr[:0]
				for _, attr := range child.Attr {
					name := strings.ToLower(attr.Key)
					value := strings.TrimSpace(attr.Val)
					if strings.HasPrefix(name, "on") {
						continue
					}
					switch name {
					case "href":
						if !strings.HasPrefix(value, "#") {
							continue
						}
					case "src":
						if child.Data != "img" || !(strings.HasPrefix(value, "data:image/png;") || strings.HasPrefix(value, "data:image/jpeg;") || strings.HasPrefix(value, "data:image/webp;")) {
							continue
						}
					case "srcset", "srcdoc", "action", "formaction", "ping", "target", "download", "http-equiv":
						continue
					}
					attrs = append(attrs, attr)
				}
				child.Attr = attrs
			}
			walk(child)
			child = next
		}
	}
	walk(root)
	var out bytes.Buffer
	if html.Render(&out, root) != nil {
		return ""
	}
	return out.String()
}