forked from alecthomas/kingpin
/
lexer.go
135 lines (119 loc) · 2.34 KB
/
lexer.go
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package kingpin
import (
"bufio"
"os"
"strings"
)
type TokenType int
// Token types.
const (
TokenShort TokenType = iota
TokenLong
TokenArg
TokenEOL
)
var (
TokenEOLMarker = Token{TokenEOL, ""}
)
type Token struct {
Type TokenType
Value string
}
func (t *Token) IsFlag() bool {
return t.Type == TokenShort || t.Type == TokenLong
}
func (t *Token) IsEOF() bool {
return t.Type == TokenEOL
}
func (t *Token) String() string {
switch t.Type {
case TokenShort:
return "-" + t.Value
case TokenLong:
return "--" + t.Value
case TokenArg:
return t.Value
case TokenEOL:
return "<EOL>"
default:
panic("unhandled type")
}
}
type Tokens []*Token
func (t Tokens) String() string {
out := []string{}
for _, tok := range t {
out = append(out, tok.String())
}
return strings.Join(out, " ")
}
func (t Tokens) Next() Tokens {
if len(t) == 0 {
return nil
}
return t[1:]
}
func (t Tokens) Return(token *Token) Tokens {
if token.Type == TokenEOL {
return t
}
return append(Tokens{token}, t...)
}
func (t Tokens) Peek() *Token {
if len(t) == 0 {
return &TokenEOLMarker
}
return t[0]
}
func Tokenize(args []string) *ParseContext {
tokens := make(Tokens, 0, len(args))
allowFlags := true
for _, arg := range args {
if allowFlags {
if arg == "--" {
allowFlags = false
continue
}
if strings.HasPrefix(arg, "--") {
parts := strings.SplitN(arg[2:], "=", 2)
tokens = append(tokens, &Token{TokenLong, parts[0]})
if len(parts) == 2 {
tokens = append(tokens, &Token{TokenArg, parts[1]})
}
continue
}
if strings.HasPrefix(arg, "-") {
for _, a := range arg[1:] {
tokens = append(tokens, &Token{TokenShort, string(a)})
}
continue
}
}
tokens = append(tokens, &Token{TokenArg, arg})
}
return &ParseContext{Tokens: tokens}
}
// ExpandArgsFromFiles expands arguments in the form @<file> into one-arg-per-
// line read from that file.
func ExpandArgsFromFiles(args []string) ([]string, error) {
out := []string{}
for _, arg := range args {
if strings.HasPrefix(arg, "@") {
r, err := os.Open(arg[1:])
if err != nil {
return nil, err
}
scanner := bufio.NewScanner(r)
for scanner.Scan() {
out = append(out, scanner.Text())
}
r.Close()
if scanner.Err() != nil {
return nil, scanner.Err()
}
} else {
out = append(out, arg)
}
}
return out, nil
}