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-rw-r--r--vendor/github.com/andybalholm/cascadia/parser.go835
1 files changed, 835 insertions, 0 deletions
diff --git a/vendor/github.com/andybalholm/cascadia/parser.go b/vendor/github.com/andybalholm/cascadia/parser.go
new file mode 100644
index 0000000..495db9c
--- /dev/null
+++ b/vendor/github.com/andybalholm/cascadia/parser.go
@@ -0,0 +1,835 @@
+// Package cascadia is an implementation of CSS selectors.
+package cascadia
+
+import (
+ "errors"
+ "fmt"
+ "regexp"
+ "strconv"
+ "strings"
+
+ "golang.org/x/net/html"
+)
+
+// a parser for CSS selectors
+type parser struct {
+ s string // the source text
+ i int // the current position
+}
+
+// parseEscape parses a backslash escape.
+func (p *parser) parseEscape() (result string, err error) {
+ if len(p.s) < p.i+2 || p.s[p.i] != '\\' {
+ return "", errors.New("invalid escape sequence")
+ }
+
+ start := p.i + 1
+ c := p.s[start]
+ switch {
+ case c == '\r' || c == '\n' || c == '\f':
+ return "", errors.New("escaped line ending outside string")
+ case hexDigit(c):
+ // unicode escape (hex)
+ var i int
+ for i = start; i < p.i+6 && i < len(p.s) && hexDigit(p.s[i]); i++ {
+ // empty
+ }
+ v, _ := strconv.ParseUint(p.s[start:i], 16, 21)
+ if len(p.s) > i {
+ switch p.s[i] {
+ case '\r':
+ i++
+ if len(p.s) > i && p.s[i] == '\n' {
+ i++
+ }
+ case ' ', '\t', '\n', '\f':
+ i++
+ }
+ }
+ p.i = i
+ return string(rune(v)), nil
+ }
+
+ // Return the literal character after the backslash.
+ result = p.s[start : start+1]
+ p.i += 2
+ return result, nil
+}
+
+func hexDigit(c byte) bool {
+ return '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F'
+}
+
+// nameStart returns whether c can be the first character of an identifier
+// (not counting an initial hyphen, or an escape sequence).
+func nameStart(c byte) bool {
+ return 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_' || c > 127
+}
+
+// nameChar returns whether c can be a character within an identifier
+// (not counting an escape sequence).
+func nameChar(c byte) bool {
+ return 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_' || c > 127 ||
+ c == '-' || '0' <= c && c <= '9'
+}
+
+// parseIdentifier parses an identifier.
+func (p *parser) parseIdentifier() (result string, err error) {
+ startingDash := false
+ if len(p.s) > p.i && p.s[p.i] == '-' {
+ startingDash = true
+ p.i++
+ }
+
+ if len(p.s) <= p.i {
+ return "", errors.New("expected identifier, found EOF instead")
+ }
+
+ if c := p.s[p.i]; !(nameStart(c) || c == '\\') {
+ return "", fmt.Errorf("expected identifier, found %c instead", c)
+ }
+
+ result, err = p.parseName()
+ if startingDash && err == nil {
+ result = "-" + result
+ }
+ return
+}
+
+// parseName parses a name (which is like an identifier, but doesn't have
+// extra restrictions on the first character).
+func (p *parser) parseName() (result string, err error) {
+ i := p.i
+loop:
+ for i < len(p.s) {
+ c := p.s[i]
+ switch {
+ case nameChar(c):
+ start := i
+ for i < len(p.s) && nameChar(p.s[i]) {
+ i++
+ }
+ result += p.s[start:i]
+ case c == '\\':
+ p.i = i
+ val, err := p.parseEscape()
+ if err != nil {
+ return "", err
+ }
+ i = p.i
+ result += val
+ default:
+ break loop
+ }
+ }
+
+ if result == "" {
+ return "", errors.New("expected name, found EOF instead")
+ }
+
+ p.i = i
+ return result, nil
+}
+
+// parseString parses a single- or double-quoted string.
+func (p *parser) parseString() (result string, err error) {
+ i := p.i
+ if len(p.s) < i+2 {
+ return "", errors.New("expected string, found EOF instead")
+ }
+
+ quote := p.s[i]
+ i++
+
+loop:
+ for i < len(p.s) {
+ switch p.s[i] {
+ case '\\':
+ if len(p.s) > i+1 {
+ switch c := p.s[i+1]; c {
+ case '\r':
+ if len(p.s) > i+2 && p.s[i+2] == '\n' {
+ i += 3
+ continue loop
+ }
+ fallthrough
+ case '\n', '\f':
+ i += 2
+ continue loop
+ }
+ }
+ p.i = i
+ val, err := p.parseEscape()
+ if err != nil {
+ return "", err
+ }
+ i = p.i
+ result += val
+ case quote:
+ break loop
+ case '\r', '\n', '\f':
+ return "", errors.New("unexpected end of line in string")
+ default:
+ start := i
+ for i < len(p.s) {
+ if c := p.s[i]; c == quote || c == '\\' || c == '\r' || c == '\n' || c == '\f' {
+ break
+ }
+ i++
+ }
+ result += p.s[start:i]
+ }
+ }
+
+ if i >= len(p.s) {
+ return "", errors.New("EOF in string")
+ }
+
+ // Consume the final quote.
+ i++
+
+ p.i = i
+ return result, nil
+}
+
+// parseRegex parses a regular expression; the end is defined by encountering an
+// unmatched closing ')' or ']' which is not consumed
+func (p *parser) parseRegex() (rx *regexp.Regexp, err error) {
+ i := p.i
+ if len(p.s) < i+2 {
+ return nil, errors.New("expected regular expression, found EOF instead")
+ }
+
+ // number of open parens or brackets;
+ // when it becomes negative, finished parsing regex
+ open := 0
+
+loop:
+ for i < len(p.s) {
+ switch p.s[i] {
+ case '(', '[':
+ open++
+ case ')', ']':
+ open--
+ if open < 0 {
+ break loop
+ }
+ }
+ i++
+ }
+
+ if i >= len(p.s) {
+ return nil, errors.New("EOF in regular expression")
+ }
+ rx, err = regexp.Compile(p.s[p.i:i])
+ p.i = i
+ return rx, err
+}
+
+// skipWhitespace consumes whitespace characters and comments.
+// It returns true if there was actually anything to skip.
+func (p *parser) skipWhitespace() bool {
+ i := p.i
+ for i < len(p.s) {
+ switch p.s[i] {
+ case ' ', '\t', '\r', '\n', '\f':
+ i++
+ continue
+ case '/':
+ if strings.HasPrefix(p.s[i:], "/*") {
+ end := strings.Index(p.s[i+len("/*"):], "*/")
+ if end != -1 {
+ i += end + len("/**/")
+ continue
+ }
+ }
+ }
+ break
+ }
+
+ if i > p.i {
+ p.i = i
+ return true
+ }
+
+ return false
+}
+
+// consumeParenthesis consumes an opening parenthesis and any following
+// whitespace. It returns true if there was actually a parenthesis to skip.
+func (p *parser) consumeParenthesis() bool {
+ if p.i < len(p.s) && p.s[p.i] == '(' {
+ p.i++
+ p.skipWhitespace()
+ return true
+ }
+ return false
+}
+
+// consumeClosingParenthesis consumes a closing parenthesis and any preceding
+// whitespace. It returns true if there was actually a parenthesis to skip.
+func (p *parser) consumeClosingParenthesis() bool {
+ i := p.i
+ p.skipWhitespace()
+ if p.i < len(p.s) && p.s[p.i] == ')' {
+ p.i++
+ return true
+ }
+ p.i = i
+ return false
+}
+
+// parseTypeSelector parses a type selector (one that matches by tag name).
+func (p *parser) parseTypeSelector() (result Selector, err error) {
+ tag, err := p.parseIdentifier()
+ if err != nil {
+ return nil, err
+ }
+
+ return typeSelector(tag), nil
+}
+
+// parseIDSelector parses a selector that matches by id attribute.
+func (p *parser) parseIDSelector() (Selector, error) {
+ if p.i >= len(p.s) {
+ return nil, fmt.Errorf("expected id selector (#id), found EOF instead")
+ }
+ if p.s[p.i] != '#' {
+ return nil, fmt.Errorf("expected id selector (#id), found '%c' instead", p.s[p.i])
+ }
+
+ p.i++
+ id, err := p.parseName()
+ if err != nil {
+ return nil, err
+ }
+
+ return attributeEqualsSelector("id", id), nil
+}
+
+// parseClassSelector parses a selector that matches by class attribute.
+func (p *parser) parseClassSelector() (Selector, error) {
+ if p.i >= len(p.s) {
+ return nil, fmt.Errorf("expected class selector (.class), found EOF instead")
+ }
+ if p.s[p.i] != '.' {
+ return nil, fmt.Errorf("expected class selector (.class), found '%c' instead", p.s[p.i])
+ }
+
+ p.i++
+ class, err := p.parseIdentifier()
+ if err != nil {
+ return nil, err
+ }
+
+ return attributeIncludesSelector("class", class), nil
+}
+
+// parseAttributeSelector parses a selector that matches by attribute value.
+func (p *parser) parseAttributeSelector() (Selector, error) {
+ if p.i >= len(p.s) {
+ return nil, fmt.Errorf("expected attribute selector ([attribute]), found EOF instead")
+ }
+ if p.s[p.i] != '[' {
+ return nil, fmt.Errorf("expected attribute selector ([attribute]), found '%c' instead", p.s[p.i])
+ }
+
+ p.i++
+ p.skipWhitespace()
+ key, err := p.parseIdentifier()
+ if err != nil {
+ return nil, err
+ }
+
+ p.skipWhitespace()
+ if p.i >= len(p.s) {
+ return nil, errors.New("unexpected EOF in attribute selector")
+ }
+
+ if p.s[p.i] == ']' {
+ p.i++
+ return attributeExistsSelector(key), nil
+ }
+
+ if p.i+2 >= len(p.s) {
+ return nil, errors.New("unexpected EOF in attribute selector")
+ }
+
+ op := p.s[p.i : p.i+2]
+ if op[0] == '=' {
+ op = "="
+ } else if op[1] != '=' {
+ return nil, fmt.Errorf(`expected equality operator, found "%s" instead`, op)
+ }
+ p.i += len(op)
+
+ p.skipWhitespace()
+ if p.i >= len(p.s) {
+ return nil, errors.New("unexpected EOF in attribute selector")
+ }
+ var val string
+ var rx *regexp.Regexp
+ if op == "#=" {
+ rx, err = p.parseRegex()
+ } else {
+ switch p.s[p.i] {
+ case '\'', '"':
+ val, err = p.parseString()
+ default:
+ val, err = p.parseIdentifier()
+ }
+ }
+ if err != nil {
+ return nil, err
+ }
+
+ p.skipWhitespace()
+ if p.i >= len(p.s) {
+ return nil, errors.New("unexpected EOF in attribute selector")
+ }
+ if p.s[p.i] != ']' {
+ return nil, fmt.Errorf("expected ']', found '%c' instead", p.s[p.i])
+ }
+ p.i++
+
+ switch op {
+ case "=":
+ return attributeEqualsSelector(key, val), nil
+ case "!=":
+ return attributeNotEqualSelector(key, val), nil
+ case "~=":
+ return attributeIncludesSelector(key, val), nil
+ case "|=":
+ return attributeDashmatchSelector(key, val), nil
+ case "^=":
+ return attributePrefixSelector(key, val), nil
+ case "$=":
+ return attributeSuffixSelector(key, val), nil
+ case "*=":
+ return attributeSubstringSelector(key, val), nil
+ case "#=":
+ return attributeRegexSelector(key, rx), nil
+ }
+
+ return nil, fmt.Errorf("attribute operator %q is not supported", op)
+}
+
+var errExpectedParenthesis = errors.New("expected '(' but didn't find it")
+var errExpectedClosingParenthesis = errors.New("expected ')' but didn't find it")
+var errUnmatchedParenthesis = errors.New("unmatched '('")
+
+// parsePseudoclassSelector parses a pseudoclass selector like :not(p).
+func (p *parser) parsePseudoclassSelector() (Selector, error) {
+ if p.i >= len(p.s) {
+ return nil, fmt.Errorf("expected pseudoclass selector (:pseudoclass), found EOF instead")
+ }
+ if p.s[p.i] != ':' {
+ return nil, fmt.Errorf("expected attribute selector (:pseudoclass), found '%c' instead", p.s[p.i])
+ }
+
+ p.i++
+ name, err := p.parseIdentifier()
+ if err != nil {
+ return nil, err
+ }
+ name = toLowerASCII(name)
+
+ switch name {
+ case "not", "has", "haschild":
+ if !p.consumeParenthesis() {
+ return nil, errExpectedParenthesis
+ }
+ sel, parseErr := p.parseSelectorGroup()
+ if parseErr != nil {
+ return nil, parseErr
+ }
+ if !p.consumeClosingParenthesis() {
+ return nil, errExpectedClosingParenthesis
+ }
+
+ switch name {
+ case "not":
+ return negatedSelector(sel), nil
+ case "has":
+ return hasDescendantSelector(sel), nil
+ case "haschild":
+ return hasChildSelector(sel), nil
+ }
+
+ case "contains", "containsown":
+ if !p.consumeParenthesis() {
+ return nil, errExpectedParenthesis
+ }
+ if p.i == len(p.s) {
+ return nil, errUnmatchedParenthesis
+ }
+ var val string
+ switch p.s[p.i] {
+ case '\'', '"':
+ val, err = p.parseString()
+ default:
+ val, err = p.parseIdentifier()
+ }
+ if err != nil {
+ return nil, err
+ }
+ val = strings.ToLower(val)
+ p.skipWhitespace()
+ if p.i >= len(p.s) {
+ return nil, errors.New("unexpected EOF in pseudo selector")
+ }
+ if !p.consumeClosingParenthesis() {
+ return nil, errExpectedClosingParenthesis
+ }
+
+ switch name {
+ case "contains":
+ return textSubstrSelector(val), nil
+ case "containsown":
+ return ownTextSubstrSelector(val), nil
+ }
+
+ case "matches", "matchesown":
+ if !p.consumeParenthesis() {
+ return nil, errExpectedParenthesis
+ }
+ rx, err := p.parseRegex()
+ if err != nil {
+ return nil, err
+ }
+ if p.i >= len(p.s) {
+ return nil, errors.New("unexpected EOF in pseudo selector")
+ }
+ if !p.consumeClosingParenthesis() {
+ return nil, errExpectedClosingParenthesis
+ }
+
+ switch name {
+ case "matches":
+ return textRegexSelector(rx), nil
+ case "matchesown":
+ return ownTextRegexSelector(rx), nil
+ }
+
+ case "nth-child", "nth-last-child", "nth-of-type", "nth-last-of-type":
+ if !p.consumeParenthesis() {
+ return nil, errExpectedParenthesis
+ }
+ a, b, err := p.parseNth()
+ if err != nil {
+ return nil, err
+ }
+ if !p.consumeClosingParenthesis() {
+ return nil, errExpectedClosingParenthesis
+ }
+ if a == 0 {
+ switch name {
+ case "nth-child":
+ return simpleNthChildSelector(b, false), nil
+ case "nth-of-type":
+ return simpleNthChildSelector(b, true), nil
+ case "nth-last-child":
+ return simpleNthLastChildSelector(b, false), nil
+ case "nth-last-of-type":
+ return simpleNthLastChildSelector(b, true), nil
+ }
+ }
+ return nthChildSelector(a, b,
+ name == "nth-last-child" || name == "nth-last-of-type",
+ name == "nth-of-type" || name == "nth-last-of-type"),
+ nil
+
+ case "first-child":
+ return simpleNthChildSelector(1, false), nil
+ case "last-child":
+ return simpleNthLastChildSelector(1, false), nil
+ case "first-of-type":
+ return simpleNthChildSelector(1, true), nil
+ case "last-of-type":
+ return simpleNthLastChildSelector(1, true), nil
+ case "only-child":
+ return onlyChildSelector(false), nil
+ case "only-of-type":
+ return onlyChildSelector(true), nil
+ case "input":
+ return inputSelector, nil
+ case "empty":
+ return emptyElementSelector, nil
+ case "root":
+ return rootSelector, nil
+ }
+
+ return nil, fmt.Errorf("unknown pseudoclass :%s", name)
+}
+
+// parseInteger parses a decimal integer.
+func (p *parser) parseInteger() (int, error) {
+ i := p.i
+ start := i
+ for i < len(p.s) && '0' <= p.s[i] && p.s[i] <= '9' {
+ i++
+ }
+ if i == start {
+ return 0, errors.New("expected integer, but didn't find it")
+ }
+ p.i = i
+
+ val, err := strconv.Atoi(p.s[start:i])
+ if err != nil {
+ return 0, err
+ }
+
+ return val, nil
+}
+
+// parseNth parses the argument for :nth-child (normally of the form an+b).
+func (p *parser) parseNth() (a, b int, err error) {
+ // initial state
+ if p.i >= len(p.s) {
+ goto eof
+ }
+ switch p.s[p.i] {
+ case '-':
+ p.i++
+ goto negativeA
+ case '+':
+ p.i++
+ goto positiveA
+ case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+ goto positiveA
+ case 'n', 'N':
+ a = 1
+ p.i++
+ goto readN
+ case 'o', 'O', 'e', 'E':
+ id, nameErr := p.parseName()
+ if nameErr != nil {
+ return 0, 0, nameErr
+ }
+ id = toLowerASCII(id)
+ if id == "odd" {
+ return 2, 1, nil
+ }
+ if id == "even" {
+ return 2, 0, nil
+ }
+ return 0, 0, fmt.Errorf("expected 'odd' or 'even', but found '%s' instead", id)
+ default:
+ goto invalid
+ }
+
+positiveA:
+ if p.i >= len(p.s) {
+ goto eof
+ }
+ switch p.s[p.i] {
+ case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+ a, err = p.parseInteger()
+ if err != nil {
+ return 0, 0, err
+ }
+ goto readA
+ case 'n', 'N':
+ a = 1
+ p.i++
+ goto readN
+ default:
+ goto invalid
+ }
+
+negativeA:
+ if p.i >= len(p.s) {
+ goto eof
+ }
+ switch p.s[p.i] {
+ case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+ a, err = p.parseInteger()
+ if err != nil {
+ return 0, 0, err
+ }
+ a = -a
+ goto readA
+ case 'n', 'N':
+ a = -1
+ p.i++
+ goto readN
+ default:
+ goto invalid
+ }
+
+readA:
+ if p.i >= len(p.s) {
+ goto eof
+ }
+ switch p.s[p.i] {
+ case 'n', 'N':
+ p.i++
+ goto readN
+ default:
+ // The number we read as a is actually b.
+ return 0, a, nil
+ }
+
+readN:
+ p.skipWhitespace()
+ if p.i >= len(p.s) {
+ goto eof
+ }
+ switch p.s[p.i] {
+ case '+':
+ p.i++
+ p.skipWhitespace()
+ b, err = p.parseInteger()
+ if err != nil {
+ return 0, 0, err
+ }
+ return a, b, nil
+ case '-':
+ p.i++
+ p.skipWhitespace()
+ b, err = p.parseInteger()
+ if err != nil {
+ return 0, 0, err
+ }
+ return a, -b, nil
+ default:
+ return a, 0, nil
+ }
+
+eof:
+ return 0, 0, errors.New("unexpected EOF while attempting to parse expression of form an+b")
+
+invalid:
+ return 0, 0, errors.New("unexpected character while attempting to parse expression of form an+b")
+}
+
+// parseSimpleSelectorSequence parses a selector sequence that applies to
+// a single element.
+func (p *parser) parseSimpleSelectorSequence() (Selector, error) {
+ var result Selector
+
+ if p.i >= len(p.s) {
+ return nil, errors.New("expected selector, found EOF instead")
+ }
+
+ switch p.s[p.i] {
+ case '*':
+ // It's the universal selector. Just skip over it, since it doesn't affect the meaning.
+ p.i++
+ case '#', '.', '[', ':':
+ // There's no type selector. Wait to process the other till the main loop.
+ default:
+ r, err := p.parseTypeSelector()
+ if err != nil {
+ return nil, err
+ }
+ result = r
+ }
+
+loop:
+ for p.i < len(p.s) {
+ var ns Selector
+ var err error
+ switch p.s[p.i] {
+ case '#':
+ ns, err = p.parseIDSelector()
+ case '.':
+ ns, err = p.parseClassSelector()
+ case '[':
+ ns, err = p.parseAttributeSelector()
+ case ':':
+ ns, err = p.parsePseudoclassSelector()
+ default:
+ break loop
+ }
+ if err != nil {
+ return nil, err
+ }
+ if result == nil {
+ result = ns
+ } else {
+ result = intersectionSelector(result, ns)
+ }
+ }
+
+ if result == nil {
+ result = func(n *html.Node) bool {
+ return n.Type == html.ElementNode
+ }
+ }
+
+ return result, nil
+}
+
+// parseSelector parses a selector that may include combinators.
+func (p *parser) parseSelector() (result Selector, err error) {
+ p.skipWhitespace()
+ result, err = p.parseSimpleSelectorSequence()
+ if err != nil {
+ return
+ }
+
+ for {
+ var combinator byte
+ if p.skipWhitespace() {
+ combinator = ' '
+ }
+ if p.i >= len(p.s) {
+ return
+ }
+
+ switch p.s[p.i] {
+ case '+', '>', '~':
+ combinator = p.s[p.i]
+ p.i++
+ p.skipWhitespace()
+ case ',', ')':
+ // These characters can't begin a selector, but they can legally occur after one.
+ return
+ }
+
+ if combinator == 0 {
+ return
+ }
+
+ c, err := p.parseSimpleSelectorSequence()
+ if err != nil {
+ return nil, err
+ }
+
+ switch combinator {
+ case ' ':
+ result = descendantSelector(result, c)
+ case '>':
+ result = childSelector(result, c)
+ case '+':
+ result = siblingSelector(result, c, true)
+ case '~':
+ result = siblingSelector(result, c, false)
+ }
+ }
+
+ panic("unreachable")
+}
+
+// parseSelectorGroup parses a group of selectors, separated by commas.
+func (p *parser) parseSelectorGroup() (result Selector, err error) {
+ result, err = p.parseSelector()
+ if err != nil {
+ return
+ }
+
+ for p.i < len(p.s) {
+ if p.s[p.i] != ',' {
+ return result, nil
+ }
+ p.i++
+ c, err := p.parseSelector()
+ if err != nil {
+ return nil, err
+ }
+ result = unionSelector(result, c)
+ }
+
+ return
+}
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