gitea/vendor/github.com/aymerick/douceur/parser/parser.go

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