League\CommonMark\Inline\Parser\EmphasisParser::determineCanOpenOrClose PHP Метод

    private function determineCanOpenOrClose($charBefore, $charAfter, $character)
    {
        $afterIsWhitespace = preg_match(RegexHelper::REGEX_UNICODE_WHITESPACE_CHAR, $charAfter);
        $afterIsPunctuation = preg_match(RegexHelper::REGEX_PUNCTUATION, $charAfter);
        $beforeIsWhitespace = preg_match(RegexHelper::REGEX_UNICODE_WHITESPACE_CHAR, $charBefore);
        $beforeIsPunctuation = preg_match(RegexHelper::REGEX_PUNCTUATION, $charBefore);
        $leftFlanking = !$afterIsWhitespace && !($afterIsPunctuation && !$beforeIsWhitespace && !$beforeIsPunctuation);
        $rightFlanking = !$beforeIsWhitespace && !($beforeIsPunctuation && !$afterIsWhitespace && !$afterIsPunctuation);
        if ($character === '_') {
            $canOpen = $leftFlanking && (!$rightFlanking || $beforeIsPunctuation);
            $canClose = $rightFlanking && (!$leftFlanking || $afterIsPunctuation);
        } else {
            $canOpen = $leftFlanking;
            $canClose = $rightFlanking;
        }
        return [$canOpen, $canClose];
    }