mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 18:12:46 +00:00
410 lines
8.6 KiB
Go
410 lines
8.6 KiB
Go
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package parser
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import (
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"errors"
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"fmt"
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"regexp"
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"strings"
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"github.com/gorilla/css/scanner"
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"github.com/aymerick/douceur/css"
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)
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const (
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importantSuffixRegexp = `(?i)\s*!important\s*$`
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)
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var (
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importantRegexp *regexp.Regexp
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)
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// Parser represents a CSS parser
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type Parser struct {
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scan *scanner.Scanner // Tokenizer
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// Tokens parsed but not consumed yet
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tokens []*scanner.Token
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// Rule embedding level
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embedLevel int
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}
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func init() {
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importantRegexp = regexp.MustCompile(importantSuffixRegexp)
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}
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// NewParser instanciates a new parser
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func NewParser(txt string) *Parser {
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return &Parser{
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scan: scanner.New(txt),
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}
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}
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// Parse parses a whole stylesheet
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func Parse(text string) (*css.Stylesheet, error) {
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result, err := NewParser(text).ParseStylesheet()
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if err != nil {
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return nil, err
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}
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return result, nil
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}
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// ParseDeclarations parses CSS declarations
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func ParseDeclarations(text string) ([]*css.Declaration, error) {
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result, err := NewParser(text).ParseDeclarations()
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if err != nil {
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return nil, err
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}
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return result, nil
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}
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// ParseStylesheet parses a stylesheet
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func (parser *Parser) ParseStylesheet() (*css.Stylesheet, error) {
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result := css.NewStylesheet()
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// Parse BOM
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if _, err := parser.parseBOM(); err != nil {
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return result, err
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}
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// Parse list of rules
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rules, err := parser.ParseRules()
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if err != nil {
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return result, err
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}
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result.Rules = rules
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return result, nil
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}
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// ParseRules parses a list of rules
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func (parser *Parser) ParseRules() ([]*css.Rule, error) {
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result := []*css.Rule{}
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inBlock := false
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if parser.tokenChar("{") {
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// parsing a block of rules
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inBlock = true
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parser.embedLevel++
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parser.shiftToken()
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}
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for parser.tokenParsable() {
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if parser.tokenIgnorable() {
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parser.shiftToken()
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} else if parser.tokenChar("}") {
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if !inBlock {
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errMsg := fmt.Sprintf("Unexpected } character: %s", parser.nextToken().String())
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return result, errors.New(errMsg)
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}
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parser.shiftToken()
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parser.embedLevel--
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// finished
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break
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} else {
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rule, err := parser.ParseRule()
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if err != nil {
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return result, err
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}
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rule.EmbedLevel = parser.embedLevel
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result = append(result, rule)
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}
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}
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return result, parser.err()
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}
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// ParseRule parses a rule
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func (parser *Parser) ParseRule() (*css.Rule, error) {
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if parser.tokenAtKeyword() {
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return parser.parseAtRule()
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}
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return parser.parseQualifiedRule()
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}
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// ParseDeclarations parses a list of declarations
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func (parser *Parser) ParseDeclarations() ([]*css.Declaration, error) {
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result := []*css.Declaration{}
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if parser.tokenChar("{") {
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parser.shiftToken()
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}
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for parser.tokenParsable() {
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if parser.tokenIgnorable() {
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parser.shiftToken()
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} else if parser.tokenChar("}") {
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// end of block
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parser.shiftToken()
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break
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} else {
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declaration, err := parser.ParseDeclaration()
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if err != nil {
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return result, err
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}
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result = append(result, declaration)
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}
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}
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return result, parser.err()
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}
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// ParseDeclaration parses a declaration
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func (parser *Parser) ParseDeclaration() (*css.Declaration, error) {
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result := css.NewDeclaration()
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curValue := ""
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for parser.tokenParsable() {
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if parser.tokenChar(":") {
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result.Property = strings.TrimSpace(curValue)
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curValue = ""
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parser.shiftToken()
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} else if parser.tokenChar(";") || parser.tokenChar("}") {
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if result.Property == "" {
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errMsg := fmt.Sprintf("Unexpected ; character: %s", parser.nextToken().String())
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return result, errors.New(errMsg)
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}
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if importantRegexp.MatchString(curValue) {
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result.Important = true
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curValue = importantRegexp.ReplaceAllString(curValue, "")
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}
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result.Value = strings.TrimSpace(curValue)
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if parser.tokenChar(";") {
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parser.shiftToken()
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}
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// finished
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break
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} else {
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token := parser.shiftToken()
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curValue += token.Value
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}
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}
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// log.Printf("[parsed] Declaration: %s", result.String())
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return result, parser.err()
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}
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// Parse an At Rule
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func (parser *Parser) parseAtRule() (*css.Rule, error) {
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// parse rule name (eg: "@import")
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token := parser.shiftToken()
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result := css.NewRule(css.AtRule)
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result.Name = token.Value
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for parser.tokenParsable() {
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if parser.tokenChar(";") {
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parser.shiftToken()
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// finished
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break
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} else if parser.tokenChar("{") {
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if result.EmbedsRules() {
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// parse rules block
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rules, err := parser.ParseRules()
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if err != nil {
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return result, err
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}
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result.Rules = rules
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} else {
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// parse declarations block
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declarations, err := parser.ParseDeclarations()
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if err != nil {
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return result, err
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}
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result.Declarations = declarations
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}
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// finished
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break
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} else {
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// parse prelude
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prelude, err := parser.parsePrelude()
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if err != nil {
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return result, err
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}
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result.Prelude = prelude
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}
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}
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// log.Printf("[parsed] Rule: %s", result.String())
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return result, parser.err()
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}
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// Parse a Qualified Rule
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func (parser *Parser) parseQualifiedRule() (*css.Rule, error) {
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result := css.NewRule(css.QualifiedRule)
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for parser.tokenParsable() {
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if parser.tokenChar("{") {
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if result.Prelude == "" {
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errMsg := fmt.Sprintf("Unexpected { character: %s", parser.nextToken().String())
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return result, errors.New(errMsg)
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}
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// parse declarations block
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declarations, err := parser.ParseDeclarations()
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if err != nil {
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return result, err
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}
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result.Declarations = declarations
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// finished
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break
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} else {
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// parse prelude
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prelude, err := parser.parsePrelude()
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if err != nil {
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return result, err
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}
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result.Prelude = prelude
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}
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}
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result.Selectors = strings.Split(result.Prelude, ",")
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for i, sel := range result.Selectors {
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result.Selectors[i] = strings.TrimSpace(sel)
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}
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// log.Printf("[parsed] Rule: %s", result.String())
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return result, parser.err()
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}
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// Parse Rule prelude
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func (parser *Parser) parsePrelude() (string, error) {
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result := ""
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for parser.tokenParsable() && !parser.tokenEndOfPrelude() {
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token := parser.shiftToken()
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result += token.Value
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}
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result = strings.TrimSpace(result)
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// log.Printf("[parsed] prelude: %s", result)
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return result, parser.err()
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}
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// Parse BOM
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func (parser *Parser) parseBOM() (bool, error) {
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if parser.nextToken().Type == scanner.TokenBOM {
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parser.shiftToken()
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return true, nil
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}
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return false, parser.err()
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}
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// Returns next token without removing it from tokens buffer
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func (parser *Parser) nextToken() *scanner.Token {
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if len(parser.tokens) == 0 {
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// fetch next token
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nextToken := parser.scan.Next()
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// log.Printf("[token] %s => %v", nextToken.Type.String(), nextToken.Value)
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// queue it
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parser.tokens = append(parser.tokens, nextToken)
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}
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return parser.tokens[0]
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}
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// Returns next token and remove it from the tokens buffer
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func (parser *Parser) shiftToken() *scanner.Token {
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var result *scanner.Token
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result, parser.tokens = parser.tokens[0], parser.tokens[1:]
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return result
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}
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// Returns tokenizer error, or nil if no error
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func (parser *Parser) err() error {
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if parser.tokenError() {
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token := parser.nextToken()
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return fmt.Errorf("Tokenizer error: %s", token.String())
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}
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return nil
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}
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// Returns true if next token is Error
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func (parser *Parser) tokenError() bool {
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return parser.nextToken().Type == scanner.TokenError
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}
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// Returns true if next token is EOF
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func (parser *Parser) tokenEOF() bool {
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return parser.nextToken().Type == scanner.TokenEOF
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}
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// Returns true if next token is a whitespace
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func (parser *Parser) tokenWS() bool {
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return parser.nextToken().Type == scanner.TokenS
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}
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// Returns true if next token is a comment
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func (parser *Parser) tokenComment() bool {
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return parser.nextToken().Type == scanner.TokenComment
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}
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// Returns true if next token is a CDO or a CDC
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func (parser *Parser) tokenCDOorCDC() bool {
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switch parser.nextToken().Type {
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case scanner.TokenCDO, scanner.TokenCDC:
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return true
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default:
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return false
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}
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}
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// Returns true if next token is ignorable
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func (parser *Parser) tokenIgnorable() bool {
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return parser.tokenWS() || parser.tokenComment() || parser.tokenCDOorCDC()
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}
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// Returns true if next token is parsable
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func (parser *Parser) tokenParsable() bool {
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return !parser.tokenEOF() && !parser.tokenError()
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}
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// Returns true if next token is an At Rule keyword
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func (parser *Parser) tokenAtKeyword() bool {
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return parser.nextToken().Type == scanner.TokenAtKeyword
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}
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// Returns true if next token is given character
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func (parser *Parser) tokenChar(value string) bool {
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token := parser.nextToken()
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return (token.Type == scanner.TokenChar) && (token.Value == value)
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}
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// Returns true if next token marks the end of a prelude
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func (parser *Parser) tokenEndOfPrelude() bool {
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return parser.tokenChar(";") || parser.tokenChar("{")
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}
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