How can I replace all with argument in Golang regex? - regex

Question

I am using Golang regex package, I want to use regex ReplaceAllStringFunc with argument, not only with the source string.
For example, I want to update this text
"<img src=\"/m/1.jpg\" /> <img src=\"/m/2.jpg\" /> <img src=\"/m/3.jpg\" />"
To (change "m" to "a" or anything else):
"<img src=\"/a/1.jpg\" /> <img src=\"/a/2.jpg\" /> <img src=\"/a/3.jpg\" />"
I would like to have something like:
func UpdateText(text string) string {
re, _ := regexp.Compile(`<img.*?src=\"(.*?)\"`)
text = re.ReplaceAllStringFunc(text, updateImgSrc)
return text
}
// update "/m/1.jpg" to "/a/1.jpg"
func updateImgSrc(imgSrcText, prefix string) string {
// replace "m" by prefix
return "<img src=\"" + newImgSrc + "\""
}
I checked the doc, ReplaceAllStringFunc doesn't support argument, but what would be the best way to achieve my goal?
More generally, I would like to find all occurrences of one pattern then update each with a new string which is composed by source string + a new parameter, could anyone give any idea?

Answer 1

I agree with the comments, you probably don't want to parse HTML with regular expressions (bad things will happen).
However, let's pretend it's not HTML, and you want to only replace submatches. You could do this
func UpdateText(input string) (string, error) {
re, err := regexp.Compile(`img.*?src=\"(.*?)\.(.*?)\"`)
if err != nil {
return "", err
}
indexes := re.FindAllStringSubmatchIndex(input, -1)
output := input
for _, match := range indexes {
imgStart := match[2]
imgEnd := match[3]
newImgName := strings.Replace(input[imgStart:imgEnd], "m", "a", -1)
output = output[:imgStart] + newImgName + input[imgEnd:]
}
return output, nil
}
see on playground
(note that I've slightly changed your regular expression to match the file extension separately)

Answer 2

thanks for kostix's advice, here is my solution using html parser.
func UpdateAllResourcePath(text, prefix string) (string, error) {
doc, err := goquery.NewDocumentFromReader(strings.NewReader(text))
if err != nil {
return "", err
}
sel := doc.Find("img")
length := len(sel.Nodes)
for index := 0; index < length; index++ {
imgSrc, ok := sel.Eq(index).Attr("src")
if !ok {
continue
}
newImgSrc, err := UpdateResourcePath(imgSrc, prefix) // change the imgsrc here
if err != nil {
return "", err
}
sel.Eq(index).SetAttr("src", newImgSrc)
}
newtext, err := doc.Find("body").Html()
if err != nil {
return "", err
}
return newtext, nil
}