class.ilDclTokenizer.php

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<?php

class ilDclTokenizer
{
    public static function getTokens(string $expression): array
    {
        $expression = ltrim($expression, '=');
        $expression = trim($expression);

        $matches = [];
        //Match all & inside [] (e.g. [[Metadaten & OER]])
        preg_match_all("/\[\[[^\]]*&[^\]]*\]\]/ui", $expression, $matches);
        $matches_inside_brackets = $matches[0];
        $replace_random = sha1("replacement_string");


        //Replace those & with a set of unprobable chars, to be ignored by the following selection of tokens
        foreach ($matches_inside_brackets as $match) {
            if (!$match) {
                continue;
            }
            $match_save = str_replace("&", $replace_random, $match);
            $expression = str_replace($match, $match_save, $expression);
        }

        //var_dump($expression);
        preg_match_all("/([^\\\\&]|\\\\&)*/ui", $expression, $matches);
        $results = $matches[0];

        $return = [];
        foreach ($results as $result) {
            if (!$result) {
                continue;
            }
            $replace = str_ireplace('\&', '&', $result);

            //Replace those & before replaced chars back
            $return[] = str_replace($replace_random, "&", $replace);

        }

        return array_map('trim', $return);
    }

    public static function getMathTokens(string $math_expression): array
    {
        $operators = array_keys(ilDclExpressionParser::getOperators());
        $pattern = '#((^\[\[)[\d\.]+)|(\(|\)|\\' . implode("|\\", $operators) . ')#';
        $tokens = preg_split($pattern, $math_expression, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);

        return array_map('trim', $tokens);
    }
}