Implement lexer

ltm_lex.go

@@ -0,0 +1,121 @@
+package tmsh
+
+import (
+	"bytes"
+	"strings"
+)
+
+type Token int
+
+const (
+	ILLEGAL Token = iota
+	EOF
+	WS
+	NEWLINE
+
+	L_BRACE
+	R_BRACE
+
+	IDENT
+
+	LTM
+	TYPE
+)
+
+type Scanner struct {
+	r *strings.Reader
+}
+
+func NewScanner(data string) *Scanner {
+	return &Scanner{r: strings.NewReader(data)}
+}
+func isWhitespace(ch rune) bool {
+	return ch == ' ' || ch == '\t'
+}
+
+func isLetter(ch rune) bool {
+	return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') ||
+		ch == '.' || ch == '_' || ch == '-' || ch == ':'
+}
+
+func isDigit(ch rune) bool {
+	return (ch >= '0' && ch <= '9')
+}
+
+func (s *Scanner) read() rune {
+	ch, _, err := s.r.ReadRune()
+	if err != nil {
+		return rune(0)
+	}
+	return ch
+}
+
+func (s *Scanner) unread() { _ = s.r.UnreadRune() }
+
+func (s *Scanner) Scan() (tok Token, lit string) {
+	ch := s.read()
+
+	if isWhitespace(ch) {
+		s.unread()
+		return s.scanWhitespace()
+	} else if isLetter(ch) || isDigit(ch) {
+		s.unread()
+		return s.scanIdent()
+	}
+
+	switch ch {
+	case rune(0):
+		return EOF, ""
+	case '\n':
+		return NEWLINE, string(ch)
+	case '{':
+		return L_BRACE, string(ch)
+	case '}':
+		return R_BRACE, string(ch)
+	}
+
+	return ILLEGAL, string(ch)
+}
+
+func (s *Scanner) scanWhitespace() (tok Token, lit string) {
+	var buf bytes.Buffer
+	buf.WriteRune(s.read())
+
+	for {
+		if ch := s.read(); ch == rune(0) {
+			break
+		} else if !isWhitespace(ch) {
+			s.unread()
+			break
+		} else {
+			buf.WriteRune(ch)
+		}
+	}
+
+	return WS, buf.String()
+}
+
+func (s *Scanner) scanIdent() (tok Token, lit string) {
+	var buf bytes.Buffer
+	buf.WriteRune(s.read())
+
+	for {
+		if ch := s.read(); ch == rune(0) {
+			break
+		} else if !isLetter(ch) && !isDigit(ch) && ch != '_' {
+			s.unread()
+			break
+		} else {
+			_, _ = buf.WriteRune(ch)
+		}
+	}
+
+	switch buf.String() {
+	case "ltm":
+		return LTM, buf.String()
+	case "node", "pool", "virtual":
+		return TYPE, buf.String()
+	}
+
+	return IDENT, buf.String()
+}