Forum Extension badly in need of refactoring...

[tmallen]

This extension loads some stylesheets and scripts, then extends the StringFormatter class to provide my own forum post parser. The parser does only four things:

 

1,2. Replace < with < and > with >

3. Replace

[code/] with <pre title="code"/>, and

 with <pre title="code" class="$1"/>
4. Replace all newlines not occurring in a "pre" block with an HTML line break

Judging by how complex the Regex needed to be for step four, I know I'm doing something very wrong. Here's the class:

[code]<?php
class SyntaxHighlighterFormatter extends StringFormatter {
    function Parse($String, $Object, $FormatPurpose) {
        if ($FormatPurpose == FORMAT_STRING_FOR_DISPLAY) {
            $hlString = $String;
            // Steps 1 and 2
            $hlString = str_replace('<', '<', $hlString);
            $hlString = str_replace('>', '>', $hlString);
            // Step 3
            $hlString = preg_replace("/\[code( lang=\"([A-Za-z]+)\")?\]/", "<pre title=\"code\" class=\"$2\">", $hlString);
            // I had to remove part of the close "code" tag because the PHPFreaks forum was
            // butchering the code otherwise.
            $hlString = str_replace('/code]', '</pre>', $hlString);
            // Step 4
            $hlString = preg_replace("#(?:\r\n|[\r\n])(?=(?:[^<]|<(?!/pre))*(?:<pre|\Z))#", "<br />", $hlString);
            return $hlString;
        }
        // This extension only needs to deal with 'FORMAT_STRING_FOR_DISPLAY'
        else {
            return $String;
        }
    }
}
?>

 

Any advice? Specifically, I'm interested in the best way to parse the Post string, as I'm sure that my current method is impractical. Note that it does execute steps 1-4 perfectly every time, so nothing's functionally broken.

[tmallen]

Edit: I've replaced the manual < and > substitution lines with the simpler:

 

<?php             
$hlString = htmlspecialchars($String, ENT_NOQUOTES);
?>

 

It seems to be working fine.

 

A big hurdle for me is that I want to further build this parser. I'd like it to, at the very least, convert URLs to links and maybe even add some basic HTML/markdown/BBCode support.

[tmallen]

Also, this is for escaping/transforming output, not filtering input.

[tmallen]

Any advice?