Numbered templates (for theorems) in MediaWiki

I am setting up a MediaWiki instance that will in particular contain mathematical material. I want to write a template for theorems, with the two following properties:

1. The theorems are automatically numbered. This numbering should be dynamic: if an edition inserts a theorem between Theorems 1 and 2, the latter should become Theorem 3.
2. The theorems can be referred to: I want a piece of code that produces "Theorem 2", given an identifier of the second theorem of the page. (Which means that the template for theorems should be given this identifier as a parameter.)

Basically, I want an equivalent of LaTeX's theorem environment and of its \ref command. I'm asking for a template, but mere templates may not be powerful enough, in which case any alternative is appreciated.

Do you have any hints of what is the best way to achieve this?

As pointed out by @Alexander Mashin, there is no hope for a solution using MediaWiki's embedded Lua engine. In the end I relied on this answer and did the following.

First a template for theorems.

A parameter id is stored in a data-theoremid attribute of the container. As an (unnecessary) enhancement, I did the same for a parameter type allowing for different theorem types: Theorem, Lemma, etc.

<div class="theorembox {{{type}}}" data-theoremid="{{{id}}}" data-theoremtype="{{{type}}}">
<div class="theoremhead">
<span class="theoremtype">{{ucfirst:{{{type}}}}}</span>&nbsp;<span class="theoremcount"></span>
{{#if:{{{title|}}}|<span class="theoremtitle">({{{title}}})</span>|}}
</div>
{{{content}}}
</div>

The usage is {{Theorem box|id=mytheorem|type=Theorem|title=Fermat's last theorem|content=For all n≥3, ...}}.

Second a template for references.

The identifier of the referred theorem is given as {{{1}}}.

<span class="theoremref" data-referto="{{{1}}}">[[#theorem:{{{1}}}|<span class="theoremtype"></span>&nbsp;<span class="theoremcount"></span>]]</span>

The usage is {{Theorem ref|mytheorem}}.

Then two JavaScript functions

The first one looks for theorems and numbers them (storing, for each identifier, the corresponding theorem type and number); the second one looks for reference calls and fills them. I put these functions in MediaWiki:Common.js.

var theorems = {};

document.querySelectorAll('.theorembox').forEach((el,i) => {
    var id = el.getAttribute('data-theoremid').replace(/\s/g, "_");
    var type = el.getAttribute('data-theoremtype');
    var number = i+1;
    el.setAttribute('id', 'theorem:' + id);
    el.querySelector('.theoremcount').innerHTML = number;
    theorems[id] = {type:type, number:number};
});

document.querySelectorAll('.theoremref').forEach((el,i) => {
    var id = el.getAttribute('data-referto').replace(/\s/g, "_");
    var href = '#theorem:' + id;
    var type = theorems[id].type;
    var number = theorems[id].number;
    el.querySelector('a').setAttribute('href', href);
    el.querySelector('.theoremtype').innerHTML = type.charAt(0).toUpperCase() + type.slice(1);
    el.querySelector('.theoremcount').innerHTML = number;
});