/
parse.go
90 lines (81 loc) · 1.69 KB
/
parse.go
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package lich
import (
"errors"
"strings"
"github.com/carlmjohnson/lich/lex"
)
// Errors introduced during decoding
var (
ErrUnexpectedClose = errors.New("Got unexpected close token")
ErrMissingClose = errors.New("Did not receive a close token")
ErrBadKeyType = errors.New("Lich dict key must be of type data")
)
func Decode(s string) (Element, error) {
sc := lex.NewScanner(strings.NewReader(s))
el, err := decodeElement(sc)
if err != nil {
return nil, err
}
if sc.Next() {
panic("Huh?")
}
if err = sc.Error(); err != nil {
return nil, err
}
return el, err
}
func decodeElement(s *lex.Scanner) (Element, error) {
if !s.Next() {
return nil, ErrUnexpectedClose
}
switch s.Token {
case lex.DataToken:
return DataString(s.Data), nil
case lex.ArrayOpen:
return decodeArray(s)
case lex.ArrayClose:
return nil, ErrUnexpectedClose
case lex.DictOpen:
return decodeDict(s)
case lex.DictClose:
return nil, ErrUnexpectedClose
}
panic("Unknown lexer token type")
}
func decodeArray(s *lex.Scanner) (Element, error) {
var a Array
for s.Next() {
switch s.Token {
case lex.DataToken:
a = append(a, DataString(s.Data))
case lex.ArrayOpen:
el, err := decodeArray(s)
if err != nil {
return nil, err
}
a = append(a, el)
case lex.ArrayClose:
return a, nil
}
}
return nil, ErrMissingClose
}
func decodeDict(s *lex.Scanner) (Element, error) {
d := make(Dict)
for s.Next() {
switch s.Token {
case lex.DataToken:
key := DataString(s.Data)
el, err := decodeElement(s)
if err != nil {
return nil, err
}
d[key] = el
case lex.DictClose:
return d, nil
default:
return nil, ErrBadKeyType
}
}
return nil, ErrMissingClose
}