wip

vendor/github.com/antonmedv/expr/parser/lexer/state.go

@@ -0,0 +1,134 @@
+package lexer
+
+import (
+	"strings"
+)
+
+type stateFn func(*lexer) stateFn
+
+func root(l *lexer) stateFn {
+	switch r := l.next(); {
+	case r == eof:
+		l.emitEOF()
+		return nil
+	case IsSpace(r):
+		l.ignore()
+		return root
+	case r == '\'' || r == '"':
+		l.scanString(r)
+		str, err := unescape(l.word())
+		if err != nil {
+			l.error("%v", err)
+		}
+		l.emitValue(String, str)
+	case '0' <= r && r <= '9':
+		l.backup()
+		return number
+	case strings.ContainsRune("([{", r):
+		l.emit(Bracket)
+	case strings.ContainsRune(")]}", r):
+		l.emit(Bracket)
+	case strings.ContainsRune("#,?:%+-/", r): // single rune operator
+		l.emit(Operator)
+	case strings.ContainsRune("&|!=*<>", r): // possible double rune operator
+		l.accept("&|=*")
+		l.emit(Operator)
+	case r == '.':
+		l.backup()
+		return dot
+	case IsAlphaNumeric(r):
+		l.backup()
+		return identifier
+	default:
+		return l.error("unrecognized character: %#U", r)
+	}
+	return root
+}
+
+func number(l *lexer) stateFn {
+	if !l.scanNumber() {
+		return l.error("bad number syntax: %q", l.word())
+	}
+	l.emit(Number)
+	return root
+}
+
+func (l *lexer) scanNumber() bool {
+	digits := "0123456789_"
+	// Is it hex?
+	if l.accept("0") {
+		// Note: Leading 0 does not mean octal in floats.
+		if l.accept("xX") {
+			digits = "0123456789abcdefABCDEF_"
+		} else if l.accept("oO") {
+			digits = "01234567_"
+		} else if l.accept("bB") {
+			digits = "01_"
+		}
+	}
+	l.acceptRun(digits)
+	loc, prev, end := l.loc, l.prev, l.end
+	if l.accept(".") {
+		// Lookup for .. operator: if after dot there is another dot (1..2), it maybe a range operator.
+		if l.peek() == '.' {
+			// We can't backup() here, as it would require two backups,
+			// and backup() func supports only one for now. So, save and
+			// restore it here.
+			l.loc, l.prev, l.end = loc, prev, end
+			return true
+		}
+		l.acceptRun(digits)
+	}
+	if l.accept("eE") {
+		l.accept("+-")
+		l.acceptRun(digits)
+	}
+	// Next thing mustn't be alphanumeric.
+	if IsAlphaNumeric(l.peek()) {
+		l.next()
+		return false
+	}
+	return true
+}
+
+func dot(l *lexer) stateFn {
+	l.next()
+	if l.accept("0123456789") {
+		l.backup()
+		return number
+	}
+	l.accept(".")
+	l.emit(Operator)
+	return root
+}
+
+func identifier(l *lexer) stateFn {
+loop:
+	for {
+		switch r := l.next(); {
+		case IsAlphaNumeric(r):
+			// absorb
+		default:
+			l.backup()
+			switch l.word() {
+			case "not":
+				return not
+			case "in", "or", "and", "matches", "contains", "startsWith", "endsWith":
+				l.emit(Operator)
+			default:
+				l.emit(Identifier)
+			}
+			break loop
+		}
+	}
+	return root
+}
+
+func not(l *lexer) stateFn {
+	if l.acceptWord(" in") {
+		l.emit(Operator)
+	} else {
+		l.emit(Operator)
+	}
+	return root
+}