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- package cascadia
- import (
- "bytes"
- "fmt"
- "regexp"
- "strings"
- "golang.org/x/net/html"
- )
- // the Selector type, and functions for creating them
- // A Selector is a function which tells whether a node matches or not.
- type Selector func(*html.Node) bool
- // hasChildMatch returns whether n has any child that matches a.
- func hasChildMatch(n *html.Node, a Selector) bool {
- for c := n.FirstChild; c != nil; c = c.NextSibling {
- if a(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 Selector) bool {
- for c := n.FirstChild; c != nil; c = c.NextSibling {
- if a(c) || (c.Type == html.ElementNode && hasDescendantMatch(c, a)) {
- return true
- }
- }
- return false
- }
- // Compile parses a selector and returns, if successful, a Selector object
- // that can be used to match against html.Node objects.
- func Compile(sel string) (Selector, error) {
- p := &parser{s: sel}
- compiled, err := p.parseSelectorGroup()
- if err != nil {
- return nil, err
- }
- if p.i < len(sel) {
- return nil, fmt.Errorf("parsing %q: %d bytes left over", sel, len(sel)-p.i)
- }
- return compiled, nil
- }
- // MustCompile is like Compile, but panics instead of returning an error.
- func MustCompile(sel string) Selector {
- compiled, err := Compile(sel)
- if err != nil {
- panic(err)
- }
- return compiled
- }
- // MatchAll returns a slice of the nodes that match the selector,
- // from n and its children.
- func (s Selector) MatchAll(n *html.Node) []*html.Node {
- return s.matchAllInto(n, nil)
- }
- func (s Selector) matchAllInto(n *html.Node, storage []*html.Node) []*html.Node {
- if s(n) {
- storage = append(storage, n)
- }
- for child := n.FirstChild; child != nil; child = child.NextSibling {
- storage = s.matchAllInto(child, storage)
- }
- return storage
- }
- // Match returns true if the node matches the selector.
- func (s Selector) Match(n *html.Node) bool {
- return s(n)
- }
- // MatchFirst returns the first node that matches s, from n and its children.
- func (s Selector) MatchFirst(n *html.Node) *html.Node {
- if s.Match(n) {
- return n
- }
- for c := n.FirstChild; c != nil; c = c.NextSibling {
- m := s.MatchFirst(c)
- if m != nil {
- return m
- }
- }
- return nil
- }
- // Filter returns the nodes in nodes that match the selector.
- func (s Selector) Filter(nodes []*html.Node) (result []*html.Node) {
- for _, n := range nodes {
- if s(n) {
- result = append(result, n)
- }
- }
- return result
- }
- // typeSelector returns a Selector that matches elements with a given tag name.
- func typeSelector(tag string) Selector {
- tag = toLowerASCII(tag)
- return func(n *html.Node) bool {
- return n.Type == html.ElementNode && n.Data == tag
- }
- }
- // toLowerASCII returns s with all ASCII capital letters lowercased.
- func toLowerASCII(s string) string {
- var b []byte
- for i := 0; i < len(s); i++ {
- if c := s[i]; 'A' <= c && c <= 'Z' {
- if b == nil {
- b = make([]byte, len(s))
- copy(b, s)
- }
- b[i] = s[i] + ('a' - 'A')
- }
- }
- if b == nil {
- return s
- }
- return string(b)
- }
- // attributeSelector returns a Selector that matches elements
- // where the attribute named key satisifes the function f.
- func attributeSelector(key string, f func(string) bool) Selector {
- key = toLowerASCII(key)
- return func(n *html.Node) bool {
- if n.Type != html.ElementNode {
- return false
- }
- for _, a := range n.Attr {
- if a.Key == key && f(a.Val) {
- return true
- }
- }
- return false
- }
- }
- // attributeExistsSelector returns a Selector that matches elements that have
- // an attribute named key.
- func attributeExistsSelector(key string) Selector {
- return attributeSelector(key, func(string) bool { return true })
- }
- // attributeEqualsSelector returns a Selector that matches elements where
- // the attribute named key has the value val.
- func attributeEqualsSelector(key, val string) Selector {
- return attributeSelector(key,
- func(s string) bool {
- return s == val
- })
- }
- // attributeNotEqualSelector returns a Selector that matches elements where
- // the attribute named key does not have the value val.
- func attributeNotEqualSelector(key, val string) Selector {
- key = toLowerASCII(key)
- return func(n *html.Node) bool {
- if n.Type != html.ElementNode {
- return false
- }
- for _, a := range n.Attr {
- if a.Key == key && a.Val == val {
- return false
- }
- }
- return true
- }
- }
- // attributeIncludesSelector returns a Selector that matches elements where
- // the attribute named key is a whitespace-separated list that includes val.
- func attributeIncludesSelector(key, val string) Selector {
- return attributeSelector(key,
- func(s string) bool {
- for s != "" {
- i := strings.IndexAny(s, " \t\r\n\f")
- if i == -1 {
- return s == val
- }
- if s[:i] == val {
- return true
- }
- s = s[i+1:]
- }
- return false
- })
- }
- // attributeDashmatchSelector returns a Selector that matches elements where
- // the attribute named key equals val or starts with val plus a hyphen.
- func attributeDashmatchSelector(key, val string) Selector {
- return attributeSelector(key,
- func(s string) bool {
- if s == val {
- return true
- }
- if len(s) <= len(val) {
- return false
- }
- if s[:len(val)] == val && s[len(val)] == '-' {
- return true
- }
- return false
- })
- }
- // attributePrefixSelector returns a Selector that matches elements where
- // the attribute named key starts with val.
- func attributePrefixSelector(key, val string) Selector {
- return attributeSelector(key,
- func(s string) bool {
- if strings.TrimSpace(s) == "" {
- return false
- }
- return strings.HasPrefix(s, val)
- })
- }
- // attributeSuffixSelector returns a Selector that matches elements where
- // the attribute named key ends with val.
- func attributeSuffixSelector(key, val string) Selector {
- return attributeSelector(key,
- func(s string) bool {
- if strings.TrimSpace(s) == "" {
- return false
- }
- return strings.HasSuffix(s, val)
- })
- }
- // attributeSubstringSelector returns a Selector that matches nodes where
- // the attribute named key contains val.
- func attributeSubstringSelector(key, val string) Selector {
- return attributeSelector(key,
- func(s string) bool {
- if strings.TrimSpace(s) == "" {
- return false
- }
- return strings.Contains(s, val)
- })
- }
- // attributeRegexSelector returns a Selector that matches nodes where
- // the attribute named key matches the regular expression rx
- func attributeRegexSelector(key string, rx *regexp.Regexp) Selector {
- return attributeSelector(key,
- func(s string) bool {
- return rx.MatchString(s)
- })
- }
- // intersectionSelector returns a selector that matches nodes that match
- // both a and b.
- func intersectionSelector(a, b Selector) Selector {
- return func(n *html.Node) bool {
- return a(n) && b(n)
- }
- }
- // unionSelector returns a selector that matches elements that match
- // either a or b.
- func unionSelector(a, b Selector) Selector {
- return func(n *html.Node) bool {
- return a(n) || b(n)
- }
- }
- // negatedSelector returns a selector that matches elements that do not match a.
- func negatedSelector(a Selector) Selector {
- return func(n *html.Node) bool {
- if n.Type != html.ElementNode {
- return false
- }
- return !a(n)
- }
- }
- // 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()
- }
- // textSubstrSelector returns a selector that matches nodes that
- // contain the given text.
- func textSubstrSelector(val string) Selector {
- return func(n *html.Node) bool {
- text := strings.ToLower(nodeText(n))
- return strings.Contains(text, val)
- }
- }
- // ownTextSubstrSelector returns a selector that matches nodes that
- // directly contain the given text
- func ownTextSubstrSelector(val string) Selector {
- return func(n *html.Node) bool {
- text := strings.ToLower(nodeOwnText(n))
- return strings.Contains(text, val)
- }
- }
- // textRegexSelector returns a selector that matches nodes whose text matches
- // the specified regular expression
- func textRegexSelector(rx *regexp.Regexp) Selector {
- return func(n *html.Node) bool {
- return rx.MatchString(nodeText(n))
- }
- }
- // ownTextRegexSelector returns a selector that matches nodes whose text
- // directly matches the specified regular expression
- func ownTextRegexSelector(rx *regexp.Regexp) Selector {
- return func(n *html.Node) bool {
- return rx.MatchString(nodeOwnText(n))
- }
- }
- // hasChildSelector returns a selector that matches elements
- // with a child that matches a.
- func hasChildSelector(a Selector) Selector {
- return func(n *html.Node) bool {
- if n.Type != html.ElementNode {
- return false
- }
- return hasChildMatch(n, a)
- }
- }
- // hasDescendantSelector returns a selector that matches elements
- // with any descendant that matches a.
- func hasDescendantSelector(a Selector) Selector {
- return func(n *html.Node) bool {
- if n.Type != html.ElementNode {
- return false
- }
- return hasDescendantMatch(n, a)
- }
- }
- // nthChildSelector returns a selector that implements :nth-child(an+b).
- // If last is true, implements :nth-last-child instead.
- // If ofType is true, implements :nth-of-type instead.
- func nthChildSelector(a, b int, last, ofType bool) Selector {
- return func(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
- }
- }
- // simpleNthChildSelector returns a selector that implements :nth-child(b).
- // If ofType is true, implements :nth-of-type instead.
- func simpleNthChildSelector(b int, ofType bool) Selector {
- return func(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
- }
- }
- // simpleNthLastChildSelector returns a selector that implements
- // :nth-last-child(b). If ofType is true, implements :nth-last-of-type
- // instead.
- func simpleNthLastChildSelector(b int, ofType bool) Selector {
- return func(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
- }
- }
- // onlyChildSelector returns a selector that implements :only-child.
- // If ofType is true, it implements :only-of-type instead.
- func onlyChildSelector(ofType bool) Selector {
- return func(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 count > 1 {
- return false
- }
- }
- return count == 1
- }
- }
- // inputSelector is a Selector that matches input, select, textarea and button elements.
- func inputSelector(n *html.Node) bool {
- return n.Type == html.ElementNode && (n.Data == "input" || n.Data == "select" || n.Data == "textarea" || n.Data == "button")
- }
- // emptyElementSelector is a Selector that matches empty elements.
- func emptyElementSelector(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, html.TextNode:
- return false
- }
- }
- return true
- }
- // descendantSelector returns a Selector that matches an element if
- // it matches d and has an ancestor that matches a.
- func descendantSelector(a, d Selector) Selector {
- return func(n *html.Node) bool {
- if !d(n) {
- return false
- }
- for p := n.Parent; p != nil; p = p.Parent {
- if a(p) {
- return true
- }
- }
- return false
- }
- }
- // childSelector returns a Selector that matches an element if
- // it matches d and its parent matches a.
- func childSelector(a, d Selector) Selector {
- return func(n *html.Node) bool {
- return d(n) && n.Parent != nil && a(n.Parent)
- }
- }
- // siblingSelector returns a Selector that matches an element
- // if it matches s2 and in is preceded by an element that matches s1.
- // If adjacent is true, the sibling must be immediately before the element.
- func siblingSelector(s1, s2 Selector, adjacent bool) Selector {
- return func(n *html.Node) bool {
- if !s2(n) {
- return false
- }
- if adjacent {
- for n = n.PrevSibling; n != nil; n = n.PrevSibling {
- if n.Type == html.TextNode || n.Type == html.CommentNode {
- continue
- }
- return s1(n)
- }
- return false
- }
- // Walk backwards looking for element that matches s1
- for c := n.PrevSibling; c != nil; c = c.PrevSibling {
- if s1(c) {
- return true
- }
- }
- return false
- }
- }
- // rootSelector implements :root
- func rootSelector(n *html.Node) bool {
- if n.Type != html.ElementNode {
- return false
- }
- if n.Parent == nil {
- return false
- }
- return n.Parent.Type == html.DocumentNode
- }
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