feed-to-muc/vendor/github.com/andybalholm/cascadia/pseudo_classes.go

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2021-12-13 10:29:47 +01:00
package cascadia
import (
"bytes"
"fmt"
"regexp"
"strings"
"golang.org/x/net/html"
"golang.org/x/net/html/atom"
)
// This file implements the pseudo classes selectors,
// which share the implementation of PseudoElement() and Specificity()
type abstractPseudoClass struct{}
func (s abstractPseudoClass) Specificity() Specificity {
return Specificity{0, 1, 0}
}
func (c abstractPseudoClass) PseudoElement() string {
return ""
}
type relativePseudoClassSelector struct {
name string // one of "not", "has", "haschild"
match SelectorGroup
}
func (s relativePseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
switch s.name {
case "not":
// matches elements that do not match a.
return !s.match.Match(n)
case "has":
// matches elements with any descendant that matches a.
return hasDescendantMatch(n, s.match)
case "haschild":
// matches elements with a child that matches a.
return hasChildMatch(n, s.match)
default:
panic(fmt.Sprintf("unsupported relative pseudo class selector : %s", s.name))
}
}
// hasChildMatch returns whether n has any child that matches a.
func hasChildMatch(n *html.Node, a Matcher) bool {
for c := n.FirstChild; c != nil; c = c.NextSibling {
if a.Match(c) {
return true
}
}
return false
}
// hasDescendantMatch performs a depth-first search of n's descendants,
// testing whether any of them match a. It returns true as soon as a match is
// found, or false if no match is found.
func hasDescendantMatch(n *html.Node, a Matcher) bool {
for c := n.FirstChild; c != nil; c = c.NextSibling {
if a.Match(c) || (c.Type == html.ElementNode && hasDescendantMatch(c, a)) {
return true
}
}
return false
}
// Specificity returns the specificity of the most specific selectors
// in the pseudo-class arguments.
// See https://www.w3.org/TR/selectors/#specificity-rules
func (s relativePseudoClassSelector) Specificity() Specificity {
var max Specificity
for _, sel := range s.match {
newSpe := sel.Specificity()
if max.Less(newSpe) {
max = newSpe
}
}
return max
}
func (c relativePseudoClassSelector) PseudoElement() string {
return ""
}
type containsPseudoClassSelector struct {
abstractPseudoClass
value string
own bool
}
func (s containsPseudoClassSelector) Match(n *html.Node) bool {
var text string
if s.own {
// matches nodes that directly contain the given text
text = strings.ToLower(nodeOwnText(n))
} else {
// matches nodes that contain the given text.
text = strings.ToLower(nodeText(n))
}
return strings.Contains(text, s.value)
}
type regexpPseudoClassSelector struct {
abstractPseudoClass
regexp *regexp.Regexp
own bool
}
func (s regexpPseudoClassSelector) Match(n *html.Node) bool {
var text string
if s.own {
// matches nodes whose text directly matches the specified regular expression
text = nodeOwnText(n)
} else {
// matches nodes whose text matches the specified regular expression
text = nodeText(n)
}
return s.regexp.MatchString(text)
}
// writeNodeText writes the text contained in n and its descendants to b.
func writeNodeText(n *html.Node, b *bytes.Buffer) {
switch n.Type {
case html.TextNode:
b.WriteString(n.Data)
case html.ElementNode:
for c := n.FirstChild; c != nil; c = c.NextSibling {
writeNodeText(c, b)
}
}
}
// nodeText returns the text contained in n and its descendants.
func nodeText(n *html.Node) string {
var b bytes.Buffer
writeNodeText(n, &b)
return b.String()
}
// nodeOwnText returns the contents of the text nodes that are direct
// children of n.
func nodeOwnText(n *html.Node) string {
var b bytes.Buffer
for c := n.FirstChild; c != nil; c = c.NextSibling {
if c.Type == html.TextNode {
b.WriteString(c.Data)
}
}
return b.String()
}
type nthPseudoClassSelector struct {
abstractPseudoClass
a, b int
last, ofType bool
}
func (s nthPseudoClassSelector) Match(n *html.Node) bool {
if s.a == 0 {
if s.last {
return simpleNthLastChildMatch(s.b, s.ofType, n)
} else {
return simpleNthChildMatch(s.b, s.ofType, n)
}
}
return nthChildMatch(s.a, s.b, s.last, s.ofType, n)
}
// nthChildMatch implements :nth-child(an+b).
// If last is true, implements :nth-last-child instead.
// If ofType is true, implements :nth-of-type instead.
func nthChildMatch(a, b int, last, ofType bool, n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
parent := n.Parent
if parent == nil {
return false
}
if parent.Type == html.DocumentNode {
return false
}
i := -1
count := 0
for c := parent.FirstChild; c != nil; c = c.NextSibling {
if (c.Type != html.ElementNode) || (ofType && c.Data != n.Data) {
continue
}
count++
if c == n {
i = count
if !last {
break
}
}
}
if i == -1 {
// This shouldn't happen, since n should always be one of its parent's children.
return false
}
if last {
i = count - i + 1
}
i -= b
if a == 0 {
return i == 0
}
return i%a == 0 && i/a >= 0
}
// simpleNthChildMatch implements :nth-child(b).
// If ofType is true, implements :nth-of-type instead.
func simpleNthChildMatch(b int, ofType bool, n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
parent := n.Parent
if parent == nil {
return false
}
if parent.Type == html.DocumentNode {
return false
}
count := 0
for c := parent.FirstChild; c != nil; c = c.NextSibling {
if c.Type != html.ElementNode || (ofType && c.Data != n.Data) {
continue
}
count++
if c == n {
return count == b
}
if count >= b {
return false
}
}
return false
}
// simpleNthLastChildMatch implements :nth-last-child(b).
// If ofType is true, implements :nth-last-of-type instead.
func simpleNthLastChildMatch(b int, ofType bool, n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
parent := n.Parent
if parent == nil {
return false
}
if parent.Type == html.DocumentNode {
return false
}
count := 0
for c := parent.LastChild; c != nil; c = c.PrevSibling {
if c.Type != html.ElementNode || (ofType && c.Data != n.Data) {
continue
}
count++
if c == n {
return count == b
}
if count >= b {
return false
}
}
return false
}
type onlyChildPseudoClassSelector struct {
abstractPseudoClass
ofType bool
}
// Match implements :only-child.
// If `ofType` is true, it implements :only-of-type instead.
func (s onlyChildPseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
parent := n.Parent
if parent == nil {
return false
}
if parent.Type == html.DocumentNode {
return false
}
count := 0
for c := parent.FirstChild; c != nil; c = c.NextSibling {
if (c.Type != html.ElementNode) || (s.ofType && c.Data != n.Data) {
continue
}
count++
if count > 1 {
return false
}
}
return count == 1
}
type inputPseudoClassSelector struct {
abstractPseudoClass
}
// Matches input, select, textarea and button elements.
func (s inputPseudoClassSelector) Match(n *html.Node) bool {
return n.Type == html.ElementNode && (n.Data == "input" || n.Data == "select" || n.Data == "textarea" || n.Data == "button")
}
type emptyElementPseudoClassSelector struct {
abstractPseudoClass
}
// Matches empty elements.
func (s emptyElementPseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
switch c.Type {
case html.ElementNode:
return false
case html.TextNode:
if strings.TrimSpace(nodeText(c)) == "" {
continue
} else {
return false
}
}
}
return true
}
type rootPseudoClassSelector struct {
abstractPseudoClass
}
// Match implements :root
func (s rootPseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
if n.Parent == nil {
return false
}
return n.Parent.Type == html.DocumentNode
}
func hasAttr(n *html.Node, attr string) bool {
return matchAttribute(n, attr, func(string) bool { return true })
}
type linkPseudoClassSelector struct {
abstractPseudoClass
}
// Match implements :link
func (s linkPseudoClassSelector) Match(n *html.Node) bool {
return (n.DataAtom == atom.A || n.DataAtom == atom.Area || n.DataAtom == atom.Link) && hasAttr(n, "href")
}
type langPseudoClassSelector struct {
abstractPseudoClass
lang string
}
func (s langPseudoClassSelector) Match(n *html.Node) bool {
own := matchAttribute(n, "lang", func(val string) bool {
return val == s.lang || strings.HasPrefix(val, s.lang+"-")
})
if n.Parent == nil {
return own
}
return own || s.Match(n.Parent)
}
type enabledPseudoClassSelector struct {
abstractPseudoClass
}
func (s enabledPseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
switch n.DataAtom {
case atom.A, atom.Area, atom.Link:
return hasAttr(n, "href")
case atom.Optgroup, atom.Menuitem, atom.Fieldset:
return !hasAttr(n, "disabled")
case atom.Button, atom.Input, atom.Select, atom.Textarea, atom.Option:
return !hasAttr(n, "disabled") && !inDisabledFieldset(n)
}
return false
}
type disabledPseudoClassSelector struct {
abstractPseudoClass
}
func (s disabledPseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
switch n.DataAtom {
case atom.Optgroup, atom.Menuitem, atom.Fieldset:
return hasAttr(n, "disabled")
case atom.Button, atom.Input, atom.Select, atom.Textarea, atom.Option:
return hasAttr(n, "disabled") || inDisabledFieldset(n)
}
return false
}
func hasLegendInPreviousSiblings(n *html.Node) bool {
for s := n.PrevSibling; s != nil; s = s.PrevSibling {
if s.DataAtom == atom.Legend {
return true
}
}
return false
}
func inDisabledFieldset(n *html.Node) bool {
if n.Parent == nil {
return false
}
if n.Parent.DataAtom == atom.Fieldset && hasAttr(n.Parent, "disabled") &&
(n.DataAtom != atom.Legend || hasLegendInPreviousSiblings(n)) {
return true
}
return inDisabledFieldset(n.Parent)
}
type checkedPseudoClassSelector struct {
abstractPseudoClass
}
func (s checkedPseudoClassSelector) Match(n *html.Node) bool {
if n.Type != html.ElementNode {
return false
}
switch n.DataAtom {
case atom.Input, atom.Menuitem:
return hasAttr(n, "checked") && matchAttribute(n, "type", func(val string) bool {
t := toLowerASCII(val)
return t == "checkbox" || t == "radio"
})
case atom.Option:
return hasAttr(n, "selected")
}
return false
}