// The Lex method lexs the next token into t, or returns an error.
// Implements the Lexer interface.
func (l *lexer) Lex(t *token.Token) error {
// Skip past whitespace, comments, etc.
if !l.advanceToNextToken() {
return l.err
}
t.Start = l.lastIndex
if l.eof {
t.Kind = token.EOF
t.End = t.Start
return nil
}
r := l.scanner.Rune()
if k, exists := token.RunePunctuators[r]; exists {
t.Kind = k
t.End = t.Start + 1
t.Value = string(r)
if !l.advance() {
return l.err
}
return nil
}
switch {
case r == '_', l.isUpperLetter(), l.isLowerLetter():
return l.readName(t)
case r == '-', l.isDigit():
return l.readNumber(t)
case r < token.SPACE && r != token.TAB && r != token.LF && r != token.CR:
return &SyntaxError{t.Start, fmt.Errorf("invalid character: %U", r)}
}
switch r {
case '"':
return l.readString(t)
case '.':
return l.readSpread(t)
default:
return &SyntaxError{t.Start, fmt.Errorf("unexpected character: %U", r)}
}
}
