1package rel2abs
 2
 3import (
 4	"bytes"
 5	"fmt"
 6	"net/url"
 7
 8	"golang.org/x/net/html"
 9)
10
11func rel2abs(n *html.Node, nurl *url.URL) error {
12	if n.Type == html.ElementNode && n.Data == "a" {
13		for _, a := range n.Attr {
14			if a.Key == "href" {
15				rel, err := url.Parse(a.Val)
16				fmt.Println("rel:", rel)
17				if err != nil {
18					return fmt.Errorf("relative url: %w\n", err)
19				}
20
21				a.Val = nurl.ResolveReference(rel).String()
22				fmt.Println("resolved:", a.Val)
23			}
24		}
25		for c := n.FirstChild; c != nil; c = c.NextSibling {
26			rel2abs(c, nurl)
27		}
28	}
29	return nil
30}
31
32// Converts all relative URLs in htmlContent to absolute URLs,
33// resolved against a base URL.
34func Rel2Abs(htmlContent []byte, base string) ([]byte, error) {
35	doc, err := html.Parse(bytes.NewReader(htmlContent))
36	if err != nil {
37		return nil, fmt.Errorf("html parse: %w\n", err)
38	}
39
40	nurl, err := url.Parse(base)
41	if err != nil {
42		return nil, fmt.Errorf("url parse: %w\n", err)
43	}
44	rel2abs(doc, nurl)
45	buf := bytes.Buffer{}
46	html.Render(&buf, doc)
47	return buf.Bytes(), nil
48}