Fetch all available discussions in a single DB query for this post in the Renderer

[n-peugnet]

Currently the Renderer makes 1 DB query for each CROSSREFERENCE* tag in the post.

flarum-ext-cross-references/src/Formatter/CrossReferencesRenderer.php

Lines 69 to 97 in 152437d

	public function __invoke(Renderer $renderer, $context, ?string $xml, ?ServerRequestInterface $request)
	{
	if (is_null($request)) {
	if ($this->config->inDebugMode()) {
	$msg = 'request is "null", falling back to display discussion as for Guest. This is probably due to another extension not passing this parameter to "Formatter->render()". See stack trace below.';
	$this->log->report(new RuntimeException($msg));
	}
	$actor = new Guest();
	} else {
	$actor = RequestUtil::getActor($request);
	}
	$filterCrossReferences = function ($attributes) use ($actor) {
	/** @var Discussion|null */
	$discussion = Discussion::whereVisibleTo($actor)->firstWhere('id', $attributes['id']);
	if ($discussion) {
	$attributes['title'] = $discussion->title;
	} else {
	$attributes['title'] = $this->translator->trans('club-1-cross-references.forum.unknown_discussion');
	$attributes['unknown'] = true;
	}
	$attributes['comment'] = $this->translator->trans('club-1-cross-references.forum.comment');
	return $attributes;
	};
	$xml = Utils::replaceAttributes($xml, 'CROSSREFERENCESHORT', $filterCrossReferences);
	$xml = Utils::replaceAttributes($xml, 'CROSSREFERENCEURL', $filterCrossReferences);
	$xml = Utils::replaceAttributes($xml, 'CROSSREFERENCEURLCOMMENT', $filterCrossReferences);
	return $xml;
	}
	}

It is not very optimised for posts that contains multiple tags of this kind. Even less so when multiple tags all refer to the same discussion. It would be good first aggregate all the discussion ids to be able to fetch all available discussion in a single DB query.
Then, at replacement time, if the discussion is not in the fetched collection, when can mark it as unknown.

This is also a good opportunity to refactor the code to parse the XML only once and make the replacements in the resulting DOM instead of parsing it 3 times with Utils::replaceAttributes().