Support UndoManager

[satoren]

https://docs.yjs.dev/api/undo-manager

[cortfritz]

played around with an approach using updates. could evolve to support other types, depth, persistence, and better efficiency using SVs.

https://github.com/cortfritz/undo_manager

Let me know if you think that direction makes sense vs. something else. I don't love coding inversions of %{insert: blah...}

Possibly inversions of updates in rust?

I'm open.

[cortfritz]

I could put the question better; do you think the use of Yex doc updates to store differences can be a good path to implant the yjs spec for undo manager?

I could leverage SVs to be more efficient. And instead of a string for clients, I would implement the spec for contexts.

[satoren]

I was planning to export the UndoManager of yrs(rust) with nif.

[cortfritz]

derp. so much better. I'm happy to take a stab at it if you would like.

[cortfritz]

cannot get your main branch to pass tests. If i futz with mix.exs and compile the rust directly with cargo build i can compile. I'm guessing i'm not doing that right though.

in the meantime my WiP is here: https://github.com/cortfritz/y_ex/tree/feature/undo

just sketching for now.

[satoren]

The RUSTLER_PRECOMPILATION_YEX_BUILD environment variable must be set to 1. For those developers who are willing to participate I need to update README.

[cortfritz]

that works! thank you.

[cortfritz]

This is as far as i got.

https://github.com/cortfritz/y_ex/blob/feature/undo/native/yex/src/undo.rs

I'm able to create a new yrs::UndoManager and exercise some functions, but unable to get Undo to... undo. When I passed a Text into UndoManager::new as scope I could only get panics. Couldn't figure out how set up Undo to do it's job. I'm going to come back to this eventually but effort/progress is out of whack and i'm going to back off for now.

LOVE THIS PROJECT, thank you.

[satoren]

The panic is probably because the ENV is not registered with thread_local. This is used in the observer callback to send messages to the beam. Therefore, any function that will be modified must be wrapped in this. https://github.com/satoren/y_ex/blob/a23ce60c66bcfbe80b6a3accfd3aae92275cecbd/native/yex/src/awareness.rs#L96

[cortfritz]

followed your advice - this seems to go better:

https://github.com/cortfritz/y_ex/blob/feature/undo/native/yex/src/undo.rs

no errors, but I'm still not actually effecting an undo, with or without origin.

[cortfritz]

got it working!!!

I'm not able to get async working - but it looks like your implementation is synchronous?

[cortfritz]

getting Yex.UndoManager.new/2 to take Yex.Text, Yex.Map, Yex.Array, etc may have a better pattern. I couldn't get NifSharedType to work or NifYInput... I ended up with the less elegant:

1. pattern match on the elixir side to have separate functions for each
2. separate elixir go to separate rust functions in undo.rs
3. I tried having these functions use a shared impelementation but did not get that working either. So very not DRY, each function does essentially the same thing in prepping the call to yrs undo::new

I haven't tackled XML types yet.

But tests passing for undo on Text, Map, Array, and multiple origins for Text. Will grow tests on these to be more comprehensive and add XML types, then address other functionality.

Can refactor if I find a better pattern for the interface.

[cortfritz]

fixed the NIF interface and implementation so we are DRY and don't have parallel implementations.

implemented redo

next will support adding scopes.

[cortfritz]

implemented stop_capture, expand_scope, and exclude_origin

next adding the observable behavior and the ability to add/get meta info on stack items.

[cortfritz]

ok, i believe i have implemented (with caveats below) all of the features demonstrated in the yjs example you link above.

rust

• core undo.rs here: https://github.com/cortfritz/y_ex/blob/feature/undo/native/yex/src/undo.rs
• some additions to atoms.rs
• that one necessary line in lib.rs

elixir

• core elixir undo_manager.ex here: https://github.com/cortfritz/y_ex/blob/feature/undo/lib/undo_manager.ex
• tests - good place to see usage obvs - here: https://github.com/cortfritz/y_ex/blob/feature/undo/test/undo_manager_test.exs
• additional tests mirroring examples found on your yjs example page linked at the top of this issue: https://github.com/cortfritz/y_ex/blob/feature/undo/test/undo_yjs_scenarios_test.exs
• awkward directory tree placement of stack item here (maybe should go somewhere else): https://github.com/cortfritz/y_ex/blob/feature/undo/lib/undo_manager/stack_item.ex
• GenServer to support observer, necessary for metadata management and super useful for other activity in /lib/server along side your doc server.

caveats

• no support for XML yet.
• need more tests to validate more complex embedded Yex entitites (text in map, in array, and so on )
• i have no idea what i'm doing in rust, so maybe there are much better ways to do these things
• i haven't taken a second pass at the genserver, i feel like i overengineered it.
• calls to underlying yrs undomanager are synchronous. not sure how this will behave at scale.
• wide wide open for notes. happy to change anything.
• aside from tests you see, untested at all. i will be using in the coming week so may have some improvements resulting from real world use

[cortfritz]

upon creating a pull request I see some egregious mistakes, bad structure, etc. have to love coderabbit!

i'm fixing these now.