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rule.go
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rule.go
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// +gengo:runtimedoc=false
package rules
import (
"bytes"
"fmt"
"regexp"
"text/scanner"
)
func MustParseRuleString(rule string) *Rule {
r, err := ParseRuleString(rule)
if err != nil {
panic(err)
}
return r
}
func ParseRuleString(rule string) (*Rule, error) {
return ParseRule([]byte(rule))
}
func ParseRule(b []byte) (*Rule, error) {
return newRuleScanner(b).rootRule()
}
func newRuleScanner(b []byte) *ruleScanner {
s := &scanner.Scanner{}
s.Init(bytes.NewReader(b))
return &ruleScanner{
data: b,
Scanner: s,
}
}
type ruleScanner struct {
data []byte
*scanner.Scanner
}
func (s *ruleScanner) rootRule() (*Rule, error) {
rule, err := s.rule()
if err != nil {
return nil, err
}
if tok := s.Scan(); tok != scanner.EOF {
return nil, NewSyntaxError("%s | rule should be end but got `%s`", s.data[0:s.Pos().Offset], string(tok))
}
return rule, nil
}
var keychars = func() map[rune]bool {
m := map[rune]bool{}
for _, r := range "@?=[](){}/<>,:" {
m[r] = true
}
return m
}()
func (s *ruleScanner) scanLit() (string, error) {
tok := s.Scan()
if keychars[tok] {
return "", NewSyntaxError("%s | invalid literal token `%s`", s.data[0:s.Pos().Offset], string(tok))
}
return s.TokenText(), nil
}
func (s *ruleScanner) rule() (*Rule, error) {
if firstToken := s.Next(); firstToken != '@' {
return nil, NewSyntaxError("%s | rule should start with `@` but got `%s`", s.data[0:s.Pos().Offset], string(firstToken))
}
startAt := s.Pos().Offset - 1
name, err := s.scanLit()
if err != nil {
return nil, err
}
if name == "" {
return nil, NewSyntaxError("%s | rule missing name", s.data[0:s.Pos().Offset])
}
rule := NewRule(name)
LOOP:
for tok := s.Peek(); ; tok = s.Peek() {
switch tok {
case '?', '=':
optional, defaultValue, err := s.optionalAndDefaultValue()
if err != nil {
return nil, err
}
rule.Optional = optional
rule.DefaultValue = defaultValue
case '<':
params, err := s.params()
if err != nil {
return nil, err
}
rule.Params = params
case '[', '(':
ranges, endTok, err := s.ranges()
if err != nil {
return nil, err
}
rule.Range = ranges
rule.ExclusiveLeft = tok == '('
rule.ExclusiveRight = endTok == ')'
case '{':
values, err := s.values()
if err != nil {
return nil, err
}
rule.ValueMatrix = append(rule.ValueMatrix, values)
case '/':
pattern, err := s.pattern()
if err != nil {
return nil, err
}
rule.Pattern = pattern.String()
case ' ':
s.Next()
default:
break LOOP
}
}
endAt := s.Pos().Offset
rule.RAW = s.data[startAt:endAt]
return rule, nil
}
func (s *ruleScanner) params() ([]RuleNode, error) {
if firstToken := s.Next(); firstToken != '<' {
return nil, NewSyntaxError("%s | parameters of rule should start with `<` but got `%s`", s.data[0:s.Pos().Offset], string(firstToken))
}
params := map[int]RuleNode{}
paramCount := 1
for tok := s.Peek(); tok != '>'; tok = s.Peek() {
if tok == scanner.EOF {
return nil, NewSyntaxError("%s | parameters of rule should end with `>` but got `%s`", s.data[0:s.Pos().Offset], string(tok))
}
switch tok {
case ' ':
s.Next()
case ',':
s.Next()
paramCount++
case '@':
rule, err := s.rule()
if err != nil {
return nil, err
}
params[paramCount] = rule
default:
lit, err := s.scanLit()
if err != nil {
return nil, err
}
if ruleNode, ok := params[paramCount]; !ok {
params[paramCount] = NewRuleLit([]byte(lit))
} else if ruleLit, ok := ruleNode.(*RuleLit); ok {
ruleLit.Append([]byte(lit))
} else {
return nil, NewSyntaxError("%s | rule should be end but got `%s`", s.data[0:s.Pos().Offset], string(tok))
}
}
}
paramList := make([]RuleNode, paramCount)
for i := range paramList {
if p, ok := params[i+1]; ok {
paramList[i] = p
} else {
paramList[i] = NewRuleLit([]byte(""))
}
}
s.Next()
return paramList, nil
}
func (s *ruleScanner) ranges() ([]*RuleLit, rune, error) {
if firstToken := s.Next(); !(firstToken == '[' || firstToken == '(') {
return nil, firstToken, NewSyntaxError("%s range of rule should start with `[` or `(` but got `%s`", s.data[0:s.Pos().Offset], string(firstToken))
}
ruleLits := map[int]*RuleLit{}
litCount := 1
for tok := s.Peek(); !(tok == ']' || tok == ')'); tok = s.Peek() {
if tok == scanner.EOF {
return nil, tok, NewSyntaxError("%s range of rule should end with `]` `)` but got `%s`", s.data[0:s.Pos().Offset], string(tok))
}
switch tok {
case ' ':
s.Next()
case ',':
s.Next()
litCount++
default:
lit, err := s.scanLit()
if err != nil {
return nil, tok, err
}
if ruleLit, ok := ruleLits[litCount]; !ok {
ruleLits[litCount] = NewRuleLit([]byte(lit))
} else {
ruleLit.Append([]byte(lit))
}
}
}
litList := make([]*RuleLit, litCount)
for i := range litList {
if p, ok := ruleLits[i+1]; ok {
litList[i] = p
} else {
litList[i] = NewRuleLit([]byte(""))
}
}
return litList, s.Next(), nil
}
func (s *ruleScanner) values() ([]*RuleLit, error) {
if firstToken := s.Next(); firstToken != '{' {
return nil, NewSyntaxError("%s | values of rule should start with `{` but got `%s`", s.data[0:s.Pos().Offset], string(firstToken))
}
ruleValues := map[int]*RuleLit{}
valueCount := 1
for tok := s.Peek(); tok != '}'; tok = s.Peek() {
if tok == scanner.EOF {
return nil, NewSyntaxError("%s values of rule should end with `}`", s.data[0:s.Pos().Offset])
}
switch tok {
case ' ':
s.Next()
case ',':
s.Next()
valueCount++
default:
lit, err := s.scanLit()
if err != nil {
return nil, err
}
if ruleLit, ok := ruleValues[valueCount]; !ok {
ruleValues[valueCount] = NewRuleLit([]byte(lit))
} else {
ruleLit.Append([]byte(lit))
}
}
}
s.Next()
valueList := make([]*RuleLit, valueCount)
for i := range valueList {
if p, ok := ruleValues[i+1]; ok {
valueList[i] = p
} else {
valueList[i] = NewRuleLit([]byte(""))
}
}
return valueList, nil
}
func (s *ruleScanner) pattern() (*regexp.Regexp, error) {
firstTok := s.Next()
if firstTok != '/' {
return nil, NewSyntaxError("%s | pattern of rule should start with `/`", s.data[0:s.Pos().Offset])
}
b := &bytes.Buffer{}
for tok := s.Peek(); tok != '/'; tok = s.Peek() {
if tok == scanner.EOF {
return nil, NewSyntaxError("%s | pattern of rule should end with `/`", s.data[0:s.Pos().Offset])
}
if tok == '\\' {
tok = s.Next()
next := s.Next()
// \/ -> /
if next != '/' {
b.WriteRune(tok)
}
b.WriteRune(next)
continue
}
b.WriteRune(tok)
s.Next()
}
s.Next()
return regexp.Compile(b.String())
}
func (s *ruleScanner) optionalAndDefaultValue() (bool, []byte, error) {
firstTok := s.Next()
if !(firstTok == '=' || firstTok == '?') {
return false, nil, NewSyntaxError("%s | optional or default value of rule should start with `?` or `=`", s.data[0:s.Pos().Offset])
}
b := &bytes.Buffer{}
tok := s.Peek()
for tok == ' ' {
tok = s.Next()
}
if tok == '\'' {
for tok = s.Peek(); tok != '\''; tok = s.Peek() {
if tok == scanner.EOF {
return true, nil, NewSyntaxError("%s | default value of of rule should end with `'`", s.data[0:s.Pos().Offset])
}
if tok == '\\' {
tok = s.Next()
next := s.Next()
// \' -> '
if next != '\'' {
b.WriteRune(tok)
}
b.WriteRune(next)
continue
}
b.WriteRune(tok)
s.Next()
}
s.Next()
} else if tok != scanner.EOF && tok != '>' && tok != ',' {
// end or in stmt
b.WriteRune(tok)
lit, err := s.scanLit()
if err != nil {
return false, nil, err
}
b.WriteString(lit)
}
defaultValue := b.Bytes()
if firstTok == '=' && defaultValue == nil {
return true, []byte{}, nil
}
return true, defaultValue, nil
}
func NewSyntaxError(format string, args ...interface{}) *SyntaxError {
return &SyntaxError{
Msg: fmt.Sprintf(format, args...),
}
}
type SyntaxError struct {
Msg string
}
func (e *SyntaxError) Error() string {
return fmt.Sprintf("invalid syntax: %s", e.Msg)
}