/**
* Lexes the backslash character ("\")
*
* The backslash character ("\") is arguably the most important character in the
* RTF specification. A backslash character can indicate the following:
*
* 1. a control word (e.g., "\foo")
* 2. a control symbol (e.g., "\-")
* 3. an escaped special character (e.g., "\\")
* 4. an escaped new-line or carriage return (e.g., "\\n")
*
* @param Jstewmc\Stream\Stream $stream the character stream
* @return Jstewmc\Rtf\Token\Token|false
* @throws InvalidArgumentException if the current character in $stream is not
* the backslash character ("\")
* @since 0.2.0
*/
protected function lexBackslash(\Jstewmc\Stream\Stream $stream)
{
if ($stream->current() !== '\\') {
throw new \InvalidArgumentExeption(__METHOD__ . "() expects the current character in the stream to be a '\\'");
}
// look ahead to the next character, it'll determine what we do; just be sure
// you rollback to the current character
//
$next = $stream->next();
$stream->previous();
// if a next character exists
if ($next !== false) {
// the next character may be a literal character, an escaped new-line or
// carriage-return (i.e., an implicit "\par" control word), a control
// word, or a control symbol
//
if (in_array($next, ['\\', '{', '}'])) {
$token = Token\Text::createFromStream($stream);
} elseif ($next == "\n" || $next == "\r") {
$token = new Token\Control\Word('par');
$stream->next();
// consume the current "\" character
} elseif (ctype_alpha($next)) {
$token = Token\Control\Word::createFromStream($stream);
} else {
$token = Token\Control\Symbol::createFromStream($stream);
}
}
return $token;
}
