Catastrofic backtracking fix

[DemonTPx]

Fixes #425

Update setHostInContent regexes to reduce steps and hopefully prevent a PREG_BACKTRACK_LIMIT_ERROR and check result of preg_replace to be sure we do not set content or description to null.

Also refactor setHostInContent and getHostFromLink a bit for readability.

cc @IgorA100

[DemonTPx]

I also tested the updated regex again with a modified version of the feed item, see:

https://regex101.com/r/oxU67Z/1

[IgorA100]

I see this problem with your link.
I'll think about a solution.

[IgorA100]

You have a lot of nested tags.
Change to:
$this->content = preg_replace('!(href=|src=)(.?)(\/[^\/])!','\1\2'.$host.'\3', $this->content) ?? $this->content;
Similarly for "$this->description"

This will fix error for preg_replace

[IgorA100]

I'll write the most correct regular expression a little later.
Wait a bit. I have a lot to do now.

[DemonTPx]

I already fixed the regex in my PR. The cycles went down from over 5.8 million to 10.000 by removing the * after the first <

[IgorA100]

It is also necessary to exclude the processing of "href" in tags <code>

[DemonTPx]

Fair point, maybe the regex should only search inside <a> and <img> tags or something?

[IgorA100]

Here is most correct regular expression:
preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(\/[^\/])(?!(.(?!<code))*<\/code>)~','\1\2\3'.$host.'\4', $this->content)

[IgorA100]

maybe the regex should only search inside <a> and <img> tags

I'm not 100% sure about this, but I'll think about it. In addition, it is still necessary to replace relative links like href="xxx..."

[IgorA100]

Even if analyze only <a> and <img>, don’t need to change them in <code>.

[IgorA100]

I modified the function to include all the other possible replacements for relative links.
Can you test my changes and make them in this PR?
All replacements can be moved to a separate function since there are more of them.

All links in https://go.dev/blog/feed.atom are replaced correctly.

    protected function setHostInContent(string $host = null): void
    {
        if (is_null($host)) {
            return;
        }
        // Replaced links like href="/aaa/bbb.xxx"
        if (property_exists($this, 'content') && !is_null($this->content)) {
            $this->content = preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(\/[^\/])(?!(.(?!<code))*<\/code>)~','\1\2\3'.$host.'\4', $this->content) ?? $this->content;
        }
        if (property_exists($this, 'description') && !is_null($this->description)) {
            $this->description = preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(\/[^\/])(?!(.(?!<code))*<\/code>)~','\1\2\3'.$host.'\4', $this->description) ?? $this->description;
        }

        $itemFullLink = $this->getLink();
        if (property_exists($this, 'link') && !is_null($itemFullLink)) {
            $itemLink = implode("/", array_slice(explode("/", $itemFullLink), 0, -1))."/";
            if (property_exists($this, 'content') && !is_null($this->content)){
                // Replaced links like href="#aaa/bbb.xxx"
                $this->content = preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(#)(?!(.(?!<code))*<\/code>)~','\1\2\3'.$itemFullLink.'\4', $this->content) ?? $this->content;

                // Replaced links like href="aaa/bbb.xxx"
                $this->content = preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(\w+\b)(?![:])(?!(.(?!<code))*<\/code>)~','\1\2\3'.$itemLink.'\4', $this->content) ?? $this->content;
            }
            if (property_exists($this, 'description') && !is_null($this->description)) {
                // Replaced links like href="#aaa/bbb.xxx"
                $this->description = preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(#)(?!(.(?!<code))*<\/code>)~','\1\2\3'.$itemFullLink.'\4', $this->description) ?? $this->description;

                // Replaced links like href="aaa/bbb.xxx"
                $this->description = preg_replace('~(<\s*[^>]*)(href=|src=)(.?)(\w+\b)(?![:])(?!(.(?!<code))*<\/code>)~','\1\2\3'.$itemLink.'\4', $this->description) ?? $this->description;
            }
        }
    }

[IgorA100]

Cleanest code:

    protected function setHostInContent(string $host = null): void
    {
        if (is_null($host)) {
            return;
        }
        // Replaced links like href="/aaa/bbb.xxx"
        $pattern = '(<\s*[^>]*)(href=|src=)(.?)(\/[^\/])(?!(.(?!<code))*<\/code>)';
        $this->pregReplaceInProperty('content', $pattern, '\1\2\3'.$host.'\4');
        $this->pregReplaceInProperty('description', $pattern, '\1\2\3'.$host.'\4');

        $itemFullLink = $this->getLink();
        $itemLink = implode("/", array_slice(explode("/", $itemFullLink), 0, -1))."/";

        // Replaced links like href="#aaa/bbb.xxx"
        $pattern = '(<\s*[^>]*)(href=|src=)(.?)(#)(?!(.(?!<code))*<\/code>)';
        $this->pregReplaceInProperty('content', $pattern, '\1\2\3'.$itemFullLink.'\4');
        $this->pregReplaceInProperty('description', $pattern, '\1\2\3'.$itemFullLink.'\4');

        // Replaced links like href="aaa/bbb.xxx"
        $pattern = '(<\s*[^>]*)(href=|src=)(.?)(\w+\b)(?![:])(?!(.(?!<code))*<\/code>)';
        $this->pregReplaceInProperty('content', $pattern, '\1\2\3'.$itemLink.'\4');
        $this->pregReplaceInProperty('description', $pattern, '\1\2\3'.$itemLink.'\4');
    }

    public function pregReplaceInProperty(string $property, string $pattern, string $replacement): void
    {
        if (property_exists($this, $property) && !is_null($this->{$property})) {
            $this->{$property} = preg_replace('~'.$pattern.'~', $replacement, $this->{$property}) ?? $this->{$property};
        }
    }