// Tidy up extracted content into something that'll produce reasonable html when
// rendered
// - remove comments
// - trim empty text nodes
// - TODO make links absolute
func tidyNode(node *html.Node) {
var commentSel cascadia.Selector = func(n *html.Node) bool {
return n.Type == html.CommentNode
}
var textSel cascadia.Selector = func(n *html.Node) bool {
return n.Type == html.TextNode
}
var elementSel cascadia.Selector = func(n *html.Node) bool {
return n.Type == html.ElementNode
}
var imgSel cascadia.Selector = func(n *html.Node) bool {
return n.Type == html.ElementNode && n.DataAtom == atom.Img
}
// remove all comments
for _, n := range commentSel.MatchAll(node) {
n.Parent.RemoveChild(n)
}
leadingSpace := regexp.MustCompile(`^\s+`)
trailingSpace := regexp.MustCompile(`\s+$`)
// trim excessive leading/trailing space in text nodes, and cull empty ones
for _, n := range textSel.MatchAll(node) {
txt := leadingSpace.ReplaceAllStringFunc(n.Data, func(in string) string {
if strings.Contains(in, "\n") {
return "\n"
} else {
return " "
}
})
txt = trailingSpace.ReplaceAllStringFunc(n.Data, func(in string) string {
if strings.Contains(in, "\n") {
return "\n"
} else {
return " "
}
})
if len(strings.TrimSpace(txt)) == 0 {
n.Parent.RemoveChild(n)
} else {
n.Data = txt
}
}
// remove any elements or attrs not on the whitelist
for _, n := range elementSel.MatchAll(node) {
allowedAttrs, whiteListed := elementWhitelist[n.DataAtom]
if !whiteListed {
if n.Parent != nil {
n.Parent.RemoveChild(n)
}
continue
}
filterAttrs(n, func(attr *html.Attribute) bool {
for _, allowed := range allowedAttrs {
if attr.Key == allowed.String() {
return true
}
}
return false
})
}
// special pass for images - strip out ones with huge URIs (eg embedded
// 'data:' + base64 encoded images)
const maxSrcURI = 1024
for _, img := range imgSel.MatchAll(node) {
src := getAttr(img, "src")
if len(src) > maxSrcURI {
img.Parent.RemoveChild(img)
continue
}
}
}
