Message Rewrite Facility-like system

[aumetra]

Somewhat of a followup to #140/#159 (since this system could potentially deprecate them)

I would really like to have a system similar to Akkoma's "Message Rewrite Facility" system (https://docs.akkoma.dev/stable/configuration/mrf/).

Somewhat related to #132 since we have to figure out what "scripting" system we want for these facilities.
The current main candidates are:

• WASM
• Lua
• Rhai

[erlend-sh]

WASM would be great (multi-lang support!), but the ecosystem is still in flux. Many different approaches to consider.

Another good candidate is Rhai:

• https://www.apollographql.com/docs/router/customizations/rhai
• Projects using Rhai rhaiscript/rhai#69

On that note, here’s an interesting discussion considering the trade offs between Rhai and Deno, albeit for a different use case: aurae-runtime/aurae#35

I think one interesting point in Rhai’s favor not mentioned there is that it supports WASM. Meaning, for a scripting system with a long term plan to use WASM, Rhai can serve as an intermediary step, starting as the singular scripting language until it’s eventually delegated to one of many options when WASM is introduced as the primary scripting platform.

[silverpill]

+1 for WASM. I'm considering it as well, because WASM MRF modules can be reused by other implementations.

[aumetra]

@silverpill Interoperability would be really nice. I think an API such as

$$ (retCode, newActivityOption) = f(activity) $$

should be sufficient for a start? That should be possible since WASM does have the possibility to return multiple values now.

Or the newActivityOption could be an externally tagged union, where retCode implies the type of the union. Enough options to think about, I guess

[silverpill]

Yes, that should be enough. In the future it would be nice to also expose some kind of API to MRF module (to let it read some data from database, for example).

[aumetra]

Definitely. Maybe we should define some kind of API together and specify it somewhere so at least Mitra and Kitsune stay in sync.
Versioning could potentially be done via an global export of an i32 or something as a version discriminant

[silverpill]

That would make a good Fediverse Enhancement Proposal :)
I can't start working on it right away though, need to finish a bunch of other tasks first, and I haven't worked with WebAssembly before... So I will probably follow your lead.

[aumetra]

I guess that would also be a nice preparation for me to write an FEP before I attempt to write the "identity proof login" FEP, heh

[erlend-sh]

Related scripting discussions in Lemmy:

• Server-side plugins / extensions LemmyNet/lemmy#3562
• Automoderation LemmyNet/lemmy#3277