Nothing special here (yet)

Former-commit-id: 826d7c370481b78afd9ba92f4ae8bef1fb85a567

_future/ipel/lexer/lexer.go

@@ -0,0 +1,136 @@
+package lexer
+
+import (
+	"gopkg.in/kataras/iris.v6/_future/ipel/token"
+)
+
+type Lexer struct {
+	input   string
+	pos     int  // current pos in input, current char
+	readPos int  // current reading pos in input, after current char
+	ch      byte // current char under examination
+}
+
+func New(input string) *Lexer {
+	l := &Lexer{
+		input: input,
+	}
+	// step to the first character in order to be ready
+	l.readChar()
+	return l
+}
+
+func (l *Lexer) readChar() {
+	if l.readPos >= len(l.input) {
+		l.ch = 0
+	} else {
+		l.ch = l.input[l.readPos]
+	}
+	l.pos = l.readPos
+	l.readPos += 1
+}
+
+func (l *Lexer) NextToken() (t token.Token) {
+	l.skipWhitespace()
+
+	switch l.ch {
+	case '{':
+		t = l.newTokenRune(token.LBRACE, l.ch)
+	case '}':
+		t = l.newTokenRune(token.RBRACE, l.ch)
+	// Let's keep it simple, no evaluation for logical operators, we are not making a new programming language, keep it simple makis.
+	// ||
+	// case '|':
+	// 	if l.peekChar() == '|' {
+	// 		ch := l.ch
+	// 		l.readChar()
+	// 		t = token.Token{Type: token.OR, Literal: string(ch) + string(l.ch)}
+	// 	}
+	// ==
+	case ':':
+		t = l.newTokenRune(token.COLON, l.ch)
+	case '(':
+		t = l.newTokenRune(token.LPAREN, l.ch)
+	case ')':
+		t = l.newTokenRune(token.RPAREN, l.ch)
+	case ',':
+		t = l.newTokenRune(token.COMMA, l.ch)
+		// literals
+	case 0:
+		t.Literal = ""
+		t.Type = token.EOF
+	default:
+		// letters
+		if isLetter(l.ch) {
+			lit := l.readIdentifier()
+			typ := token.LookupIdent(lit)
+			t = l.newToken(typ, lit)
+			return
+			// numbers
+		} else if isDigit(l.ch) {
+			lit := l.readNumber()
+			t = l.newToken(token.INT, lit)
+			return
+		} else {
+			t = l.newTokenRune(token.ILLEGAL, l.ch)
+		}
+	}
+	l.readChar() // set the pos to the next
+	return
+}
+
+func (l *Lexer) newToken(tokenType token.TokenType, lit string) token.Token {
+	t := token.Token{
+		Type:    tokenType,
+		Literal: lit,
+		Start:   l.pos,
+		End:     l.pos,
+	}
+
+	if l.pos > 1 && len(lit) > 1 {
+		t.End = t.Start + len(lit) - 1
+	}
+
+	return t
+}
+
+func (l *Lexer) newTokenRune(tokenType token.TokenType, ch byte) token.Token {
+	return l.newToken(tokenType, string(ch))
+}
+
+func (l *Lexer) skipWhitespace() {
+	for l.ch == ' ' || l.ch == '\t' || l.ch == '\n' || l.ch == '\r' {
+		l.readChar()
+	}
+}
+
+func (l *Lexer) readIdentifier() string {
+	pos := l.pos
+	for isLetter(l.ch) {
+		l.readChar()
+	}
+	return l.input[pos:l.pos]
+}
+
+func (l *Lexer) peekChar() byte {
+	if l.readPos >= len(l.input) {
+		return 0
+	}
+	return l.input[l.readPos]
+}
+
+func isLetter(ch byte) bool {
+	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_'
+}
+
+func (l *Lexer) readNumber() string {
+	pos := l.pos
+	for isDigit(l.ch) {
+		l.readChar()
+	}
+	return l.input[pos:l.pos]
+}
+
+func isDigit(ch byte) bool {
+	return '0' <= ch && ch <= '9'
+}